Programs & Examples On #Xnu

xnu is the name of the operating system kernel that underpins Mac OS X/darwin and iOS.

Differences between arm64 and aarch64

AArch64 is the 64-bit state introduced in the Armv8-A architecture (https://en.wikipedia.org/wiki/ARM_architecture#ARMv8-A). The 32-bit state which is backwards compatible with Armv7-A and previous 32-bit Arm architectures is referred to as AArch32. Therefore the GNU triplet for the 64-bit ISA is aarch64. The Linux kernel community chose to call their port of the kernel to this architecture arm64 rather than aarch64, so that's where some of the arm64 usage comes from.

As far as I know the Apple backend for aarch64 was called arm64 whereas the LLVM community-developed backend was called aarch64 (as it is the canonical name for the 64-bit ISA) and later the two were merged and the backend now is called aarch64.

So AArch64 and ARM64 refer to the same thing.

Hadoop cluster setup - java.net.ConnectException: Connection refused

From the netstat output you can see the process is listening on address 127.0.0.1

tcp        0      0 127.0.0.1:9000          0.0.0.0:*  ...

from the exception message you can see that it tries to connect to address 127.0.1.1

java.net.ConnectException: Call From marta-komputer/127.0.1.1 to localhost:9000 failed ...

further in the exception it's mentionend

For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused

on this page you find

Check that there isn't an entry for your hostname mapped to 127.0.0.1 or 127.0.1.1 in /etc/hosts (Ubuntu is notorious for this)

so the conclusion is to remove this line in your /etc/hosts

127.0.1.1       marta-komputer

how to set mongod --dbpath

First you will have a config file in /etc/mongodb.conf, therefore this sounds like a homebrew install which will use some more standardized paths. The whole /data/db/ thing is referenced in a lot of manual install documentation.

So basically from your log the server is not running, it's shutting down, so there is nothing for the shell to connect to. Seems like you have had some unclean shutdowns/restarts which has led to the inconsistency.

Clear the files in the journal /usr/local/var/mongodb/journal/ on your config.

Also:

sudo rm /var/lib/mongodb/mongod.lock

Just in case, even though that part looks clean. And then restart.

Error: Expression must have integral or unscoped enum type

Your variable size is declared as: float size;

You can't use a floating point variable as the size of an array - it needs to be an integer value.

You could cast it to convert to an integer:

float *temp = new float[(int)size];

Your other problem is likely because you're writing outside of the bounds of the array:

   float *temp = new float[size];

    //Getting input from the user
    for (int x = 1; x <= size; x++){
        cout << "Enter temperature " << x << ": ";

        // cin >> temp[x];
        // This should be:
        cin >> temp[x - 1];
    }

Arrays are zero based in C++, so this is going to write beyond the end and never write the first element in your original code.

ECONNREFUSED error when connecting to mongodb from node.js

ECONNREFUSED error

There are few reasons of this error in node :

  1. Your port is already serving some service so it will refuse your connection.

    go to command line and get pid by using following command

    $ lsof -i:port_number

    Now kill pid by using

    $ kill -9 pid(which you will get by above command)

  2. Your server is not running e.g. in this case please check your mongoose server is running or run by using following command.

    $ mongod

  3. There is also possibility your localhost is not configured properly so use 127.0.0.1:27017 instead of localhost.

How to get column by number in Pandas?

another way to access a column by number is to use a mapping dictionary where the key is the column name and the value is the column number

dates = pd.date_range('1/1/2000', periods=8)

df = pd.DataFrame(np.random.randn(8, 4),
   index=dates, columns=['A', 'B', 'C', 'D'])
print(df)
dct={'A':0,'B':1,'C':2,'D':3}
columns=df.columns

print(df.iloc[:,dct['D']])

Determining type of an object in ruby

Oftentimes in Ruby, you don't actually care what the object's class is, per se, you just care that it responds to a certain method. This is known as Duck Typing and you'll see it in all sorts of Ruby codebases.

So in many (if not most) cases, its best to use Duck Typing using #respond_to?(method):

object.respond_to?(:to_i)

no matching function for call to ' '

You are passing pointers (Complex*) when your function takes references (const Complex&). A reference and a pointer are entirely different things. When a function expects a reference argument, you need to pass it the object directly. The reference only means that the object is not copied.

To get an object to pass to your function, you would need to dereference your pointers:

Complex::distanta(*firstComplexNumber, *secondComplexNumber);

Or get your function to take pointer arguments.

However, I wouldn't really suggest either of the above solutions. Since you don't need dynamic allocation here (and you are leaking memory because you don't delete what you have newed), you're better off not using pointers in the first place:

Complex firstComplexNumber(81, 93);
Complex secondComplexNumber(31, 19);
Complex::distanta(firstComplexNumber, secondComplexNumber);

Creating a List of Lists in C#

I have been toying with this idea too, but I was trying to achieve a slightly different behavior. My idea was to make a list which inherits itself, thus creating a data structure that by nature allows you to embed lists within lists within lists within lists...infinitely!

Implementation

//InfiniteList<T> is a list of itself...
public class InfiniteList<T> : List<InfiniteList<T>>
{
    //This is necessary to allow your lists to store values (of type T).
    public T Value { set; get; }
}

T is a generic type parameter. It is there to ensure type safety in your class. When you create an instance of InfiniteList, you replace T with the type you want your list to be populated with, or in this instance, the type of the Value property.

Example

//The InfiniteList.Value property will be of type string
InfiniteList<string> list = new InfiniteList<string>();

A "working" example of this, where T is in itself, a List of type string!

//Create an instance of InfiniteList where T is List<string>
InfiniteList<List<string>> list = new InfiniteList<List<string>>();

//Add a new instance of InfiniteList<List<string>> to "list" instance.
list.Add(new InfiniteList<List<string>>());

//access the first element of "list". Access the Value property, and add a new string to it.
list[0].Value.Add("Hello World");

Javascript regular expression password validation having special characters

If you check the length seperately, you can do the following:

var regularExpression  = /^[a-zA-Z]$/;

if (regularExpression.test(newPassword)) {
    alert("password should contain atleast one number and one special character");
    return false;
} 

configure: error: C compiler cannot create executables

In my case, I tried xcode-select --install but it says that it's not available from the store. Then, inspired by Rimian, I checked my gcc : gcc -v and then I got a message saying I did not aggreed.

From that point I just followed the agreement process from gcc -v, after I agreed it works fine for me.

what does this mean ? image/png;base64?

That data:image/png;base64 URL is cool, I’ve never run into it before. The long encrypted link is the actual image, i.e. no image call to the server. See RFC 2397 for details.

Side note: I have had trouble getting larger base64 images to render on IE8. I believe IE8 has a 32K limit that can be problematic for larger files. See this other StackOverflow thread for details.

No increment operator (++) in Ruby?

Ruby has no pre/post increment/decrement operator. For instance, x++ or x-- will fail to parse. More importantly, ++x or --x will do nothing! In fact, they behave as multiple unary prefix operators: -x == ---x == -----x == ...... To increment a number, simply write x += 1.

Taken from "Things That Newcomers to Ruby Should Know " (archive, mirror)

That explains it better than I ever could.

EDIT: and the reason from the language author himself (source):

  1. ++ and -- are NOT reserved operator in Ruby.
  2. C's increment/decrement operators are in fact hidden assignment. They affect variables, not objects. You cannot accomplish assignment via method. Ruby uses +=/-= operator instead.
  3. self cannot be a target of assignment. In addition, altering the value of integer 1 might cause severe confusion throughout the program.

Specifying maxlength for multiline textbox

Use a regular expression validator instead. This will work on the client side using JavaScript, but also when JavaScript is disabled (as the length check will be performed on the server as well).

The following example checks that the entered value is between 0 and 100 characters long:

<asp:RegularExpressionValidator runat="server" ID="valInput"
    ControlToValidate="txtInput"
    ValidationExpression="^[\s\S]{0,100}$"
    ErrorMessage="Please enter a maximum of 100 characters"
    Display="Dynamic">*</asp:RegularExpressionValidator>

There are of course more complex regexs you can use to better suit your purposes.

Parse v. TryParse

double.Parse("-"); raises an exception, while double.TryParse("-", out parsed); parses to 0 so I guess TryParse does more complex conversions.

How do I check/uncheck all checkboxes with a button using jQuery?

try this

$(".checkAll").click(function() {
    if("checkall" === $(this).val()) {
         $(".cb-element").attr('checked', true);
         $(this).val("uncheckall"); //change button text
    }
    else if("uncheckall" === $(this).val()) {
         $(".cb-element").attr('checked', false);
         $(this).val("checkall"); //change button text
    }
});

check output from CalledProcessError

This will return true only if host responds to ping. Works on windows and linux

def ping(host):
    """
    Returns True if host (str) responds to a ping request.
    NB on windows ping returns true for success and host unreachable
    """
    param = '-n' if platform.system().lower()=='windows' else '-c'
    result = False
    try:
        out = subprocess.check_output(['ping', param, '1', host])
        #ping exit code 0
        if 'Reply from {}'.format(host) in str(out):
            result = True          
    except  subprocess.CalledProcessError:
        #ping exit code not 0
            result = False
    #print(str(out))
    return result

How can I use optional parameters in a T-SQL stored procedure?

Five years late to the party.

It is mentioned in the provided links of the accepted answer, but I think it deserves an explicit answer on SO - dynamically building the query based on provided parameters. E.g.:

Setup

-- drop table Person
create table Person
(
    PersonId INT NOT NULL IDENTITY(1, 1) CONSTRAINT PK_Person PRIMARY KEY,
    FirstName NVARCHAR(64) NOT NULL,
    LastName NVARCHAR(64) NOT NULL,
    Title NVARCHAR(64) NULL
)
GO

INSERT INTO Person (FirstName, LastName, Title)
VALUES ('Dick', 'Ormsby', 'Mr'), ('Serena', 'Kroeger', 'Ms'), 
    ('Marina', 'Losoya', 'Mrs'), ('Shakita', 'Grate', 'Ms'), 
    ('Bethann', 'Zellner', 'Ms'), ('Dexter', 'Shaw', 'Mr'),
    ('Zona', 'Halligan', 'Ms'), ('Fiona', 'Cassity', 'Ms'),
    ('Sherron', 'Janowski', 'Ms'), ('Melinda', 'Cormier', 'Ms')
GO

Procedure

ALTER PROCEDURE spDoSearch
    @FirstName varchar(64) = null,
    @LastName varchar(64) = null,
    @Title varchar(64) = null,
    @TopCount INT = 100
AS
BEGIN
    DECLARE @SQL NVARCHAR(4000) = '
        SELECT TOP ' + CAST(@TopCount AS VARCHAR) + ' *
        FROM Person
        WHERE 1 = 1'

    PRINT @SQL

    IF (@FirstName IS NOT NULL) SET @SQL = @SQL + ' AND FirstName = @FirstName'
    IF (@LastName IS NOT NULL) SET @SQL = @SQL + ' AND FirstName = @LastName'
    IF (@Title IS NOT NULL) SET @SQL = @SQL + ' AND Title = @Title'

    EXEC sp_executesql @SQL, N'@TopCount INT, @FirstName varchar(25), @LastName varchar(25), @Title varchar(64)', 
         @TopCount, @FirstName, @LastName, @Title
END
GO

Usage

exec spDoSearch @TopCount = 3
exec spDoSearch @FirstName = 'Dick'

Pros:

  • easy to write and understand
  • flexibility - easily generate the query for trickier filterings (e.g. dynamic TOP)

Cons:

  • possible performance problems depending on provided parameters, indexes and data volume

Not direct answer, but related to the problem aka the big picture

Usually, these filtering stored procedures do not float around, but are being called from some service layer. This leaves the option of moving away business logic (filtering) from SQL to service layer.

One example is using LINQ2SQL to generate the query based on provided filters:

    public IList<SomeServiceModel> GetServiceModels(CustomFilter filters)
    {
        var query = DataAccess.SomeRepository.AllNoTracking;

        // partial and insensitive search 
        if (!string.IsNullOrWhiteSpace(filters.SomeName))
            query = query.Where(item => item.SomeName.IndexOf(filters.SomeName, StringComparison.OrdinalIgnoreCase) != -1);
        // filter by multiple selection
        if ((filters.CreatedByList?.Count ?? 0) > 0)
            query = query.Where(item => filters.CreatedByList.Contains(item.CreatedById));
        if (filters.EnabledOnly)
            query = query.Where(item => item.IsEnabled);

        var modelList = query.ToList();
        var serviceModelList = MappingService.MapEx<SomeDataModel, SomeServiceModel>(modelList);
        return serviceModelList;
    }

Pros:

  • dynamically generated query based on provided filters. No parameter sniffing or recompile hints needed
  • somewhat easier to write for those in the OOP world
  • typically performance friendly, since "simple" queries will be issued (appropriate indexes are still needed though)

Cons:

  • LINQ2QL limitations may be reached and forcing a downgrade to LINQ2Objects or going back to pure SQL solution depending on the case
  • careless writing of LINQ might generate awful queries (or many queries, if navigation properties loaded)

Removing display of row names from data frame

If you want to format your table via kable, you can use row.names = F

kable(df, row.names = F)

Source file 'Properties\AssemblyInfo.cs' could not be found

delete the assemeblyinfo.cs file from project under properties menu and rebulid it.

How to sum array of numbers in Ruby?

Ruby 2.4+ / Rails - array.sum i.e. [1, 2, 3].sum # => 6

Ruby pre 2.4 - array.inject(:+) or array.reduce(:+)

*Note: The #sum method is a new addition to 2.4 for enumerable so you will now be able to use array.sum in pure ruby, not just Rails.

Entity Framework VS LINQ to SQL VS ADO.NET with stored procedures?

your question is basically O/RM's vs hand writing SQL

Using an ORM or plain SQL?

Take a look at some of the other O/RM solutions out there, L2S isn't the only one (NHibernate, ActiveRecord)

http://en.wikipedia.org/wiki/List_of_object-relational_mapping_software

to address the specific questions:

  1. Depends on the quality of the O/RM solution, L2S is pretty good at generating SQL
  2. This is normally much faster using an O/RM once you grok the process
  3. Code is also usually much neater and more maintainable
  4. Straight SQL will of course get you more flexibility, but most O/RM's can do all but the most complicated queries
  5. Overall I would suggest going with an O/RM, the flexibility loss is negligable

Stop node.js program from command line

Resume and kill the process:

Ctrl+Z suspends it, which means it is still running as a suspended background process.

You are likely now at a terminal prompt...

  1. Give the command fg to resume the process in the foreground.

  2. type Ctrl+C to properly kill it.


Alternatively, you can kill it manually like this:

(NOTE: the following commands may require root, so sudo ... is your friend)

pkill -9 node

or, if you don't have pkill, this may work:

killall node

or perhaps this:

kill $(ps -e | grep node | awk '{print $1}')

sometimes the process will list its own grep, in which case you'll need:

kill $(ps -e | grep dmn | awk '{print $2}')

.


h/t @ruffin from the comments on the question itself. I had the same issue and his comment helped me solve it myself.

Split an integer into digits to compute an ISBN checksum

I have made this program and here is the bit of code that actually calculates the check digit in my program

    #Get the 10 digit number
    number=input("Please enter ISBN number: ")

    #Explained below
    no11 = (((int(number[0])*11) + (int(number[1])*10) + (int(number[2])*9) + (int(number[3])*8) 
           + (int(number[4])*7) + (int(number[5])*6) + (int(number[6])*5) + (int(number[7])*4) +
           (int(number[8])*3) + (int(number[9])*2))/11)

    #Round to 1 dp
    no11 = round(no11, 1)

    #explained below
    no11 = str(no11).split(".")

    #get the remainder and check digit
    remainder = no11[1]
    no11 = (11 - int(remainder))

    #Calculate 11 digit ISBN
    print("Correct ISBN number is " + number + str(no11))

Its a long line of code, but it splits the number up, multiplies the digits by the appropriate amount, adds them together and divides them by 11, in one line of code. The .split() function just creates a list (being split at the decimal) so you can take the 2nd item in the list and take that from 11 to find the check digit. This could also be made even more efficient by changing these two lines:

    remainder = no11[1]
    no11 = (11 - int(remainder))

To this:

    no11 = (11 - int(no11[1]))

Hope this helps :)

How do you check what version of SQL Server for a database using TSQL?

Try this:

SELECT
    'the sqlserver is ' + substring(@@VERSION, 21, 5) AS [sql version]

How to Multi-thread an Operation Within a Loop in Python

Edit 2018-02-06: revision based on this comment

Edit: forgot to mention that this works on Python 2.7.x

There's multiprocesing.pool, and the following sample illustrates how to use one of them:

from multiprocessing.pool import ThreadPool as Pool
# from multiprocessing import Pool

pool_size = 5  # your "parallelness"

# define worker function before a Pool is instantiated
def worker(item):
    try:
        api.my_operation(item)
    except:
        print('error with item')

pool = Pool(pool_size)

for item in items:
    pool.apply_async(worker, (item,))

pool.close()
pool.join()

Now if you indeed identify that your process is CPU bound as @abarnert mentioned, change ThreadPool to the process pool implementation (commented under ThreadPool import). You can find more details here: http://docs.python.org/2/library/multiprocessing.html#using-a-pool-of-workers

How can I send a Firebase Cloud Messaging notification without use the Firebase Console?

As mentioned by Frank, you can use Firebase Cloud Messaging (FCM) HTTP API to trigger push notification from your own back-end. But you won't be able to

  1. send notifications to a Firebase User Identifier (UID) and
  2. send notifications to user segments (targeting properties & events like you can on the user console).

Meaning: you'll have to store FCM/GCM registration ids (push tokens) yourself or use FCM topics to subscribe users. Keep also in mind that FCM is not an API for Firebase Notifications, it's a lower-level API without scheduling or open-rate analytics. Firebase Notifications is build on top on FCM.

How to change the project in GCP using CLI commands

The selected answer doesn't help if you don't know the name of projects you have added gcloud already. My flow is to list the active projects, then switch to the one I want.

gcloud config configurations list

gcloud config configurations activate [NAME]
where [NAME] is listed from the prior command.

How to copy Outlook mail message into excel using VBA or Macros

Since you have not mentioned what needs to be copied, I have left that section empty in the code below.

Also you don't need to move the email to the folder first and then run the macro in that folder. You can run the macro on the incoming mail and then move it to the folder at the same time.

This will get you started. I have commented the code so that you will not face any problem understanding it.

First paste the below mentioned code in the outlook module.

Then

  1. Click on Tools~~>Rules and Alerts
  2. Click on "New Rule"
  3. Click on "start from a blank rule"
  4. Select "Check messages When they arrive"
  5. Under conditions, click on "with specific words in the subject"
  6. Click on "specific words" under rules description.
  7. Type the word that you want to check in the dialog box that pops up and click on "add".
  8. Click "Ok" and click next
  9. Select "move it to specified folder" and also select "run a script" in the same box
  10. In the box below, specify the specific folder and also the script (the macro that you have in module) to run.
  11. Click on finish and you are done.

When the new email arrives not only will the email move to the folder that you specify but data from it will be exported to Excel as well.

UNTESTED

Const xlUp As Long = -4162

Sub ExportToExcel(MyMail As MailItem)
    Dim strID As String, olNS As Outlook.Namespace
    Dim olMail As Outlook.MailItem
    Dim strFileName As String

    '~~> Excel Variables
    Dim oXLApp As Object, oXLwb As Object, oXLws As Object
    Dim lRow As Long

    strID = MyMail.EntryID
    Set olNS = Application.GetNamespace("MAPI")
    Set olMail = olNS.GetItemFromID(strID)

    '~~> Establish an EXCEL application object
    On Error Resume Next
    Set oXLApp = GetObject(, "Excel.Application")

    '~~> If not found then create new instance
    If Err.Number <> 0 Then
        Set oXLApp = CreateObject("Excel.Application")
    End If
    Err.Clear
    On Error GoTo 0

    '~~> Show Excel
    oXLApp.Visible = True

    '~~> Open the relevant file
    Set oXLwb = oXLApp.Workbooks.Open("C:\Sample.xls")

    '~~> Set the relevant output sheet. Change as applicable
    Set oXLws = oXLwb.Sheets("Sheet1")

    lRow = oXLws.Range("A" & oXLApp.Rows.Count).End(xlUp).Row + 1

    '~~> Write to outlook
    With oXLws
        '
        '~~> Code here to output data from email to Excel File
        '~~> For example
        '
        .Range("A" & lRow).Value = olMail.Subject
        .Range("B" & lRow).Value = olMail.SenderName
        '
    End With

    '~~> Close and Clean up Excel
    oXLwb.Close (True)
    oXLApp.Quit
    Set oXLws = Nothing
    Set oXLwb = Nothing
    Set oXLApp = Nothing

    Set olMail = Nothing
    Set olNS = Nothing
End Sub

FOLLOWUP

To extract the contents from your email body, you can split it using SPLIT() and then parsing out the relevant information from it. See this example

Dim MyAr() As String

MyAr = Split(olMail.body, vbCrLf)

For i = LBound(MyAr) To UBound(MyAr)
    '~~> This will give you the contents of your email
    '~~> on separate lines
    Debug.Print MyAr(i)
Next i

Qt Creator color scheme

I found some trick for your problem! Here you can see it: Habrahabr -- Redesigning Qt Creator by your hands (russian lang.)

According to that article, that trick is kind of not so dirty, but "hack" (probably it wouldn't harm your system, but it can leave some artifacts on your interface).

You don't need to patch something (there is possibility, but I don't recommend).

Main idea is to use stylesheet like this stylesheet.css:

// on Linux
qtcreator -stylesheet='.qt-stylesheet.css' 
// on Windows
[pathToQt]\QtCreator\bin\qtcreator.exe -stylesheet [pathToStyleSheet]

To get such effect: QtCreator before and after

To customize by your needs, you may need to read documentation: Qt Style Sheets Reference, Qt Style Sheets Examples and so on.

This wiki page is dedicated to custom Qt Creator styling.

P.S. If you'll got better stylesheet, share it, I'll be happy! :)


UPD (10.12.2014): Hopefully, now we can close this topic. Thanks, Simon G., Things have changed once again. Users may use custom themes since QtCreator 3.3. So hacky stylesheets are no longer needed.

Everyone can take a look at todays update: Qt 5.4 released. There you can find information that Qt 5.4, also comes with a brand new version of Qt Creator 3.3. Just take a look at official video at Youtube.

So, to apply dark theme you need go to "Tools" -> "Options" -> "Environment" -> "General" tab, and there you need to change "Theme".

See more information about its configuring here: Configuring Qt Creator.

How do I create 7-Zip archives with .NET?

If you can guarantee the 7-zip app will be installed (and in the path) on all target machines, you can offload by calling the command line app 7z. Not the most elegant solution but it is the least work.

Python None comparison: should I use "is" or ==?

is is generally preferred when comparing arbitrary objects to singletons like None because it is faster and more predictable. is always compares by object identity, whereas what == will do depends on the exact type of the operands and even on their ordering.

This recommendation is supported by PEP 8, which explicitly states that "comparisons to singletons like None should always be done with is or is not, never the equality operators."

What is a good way to handle exceptions when trying to read a file in python?

Adding to @Josh's example;

fName = [FILE TO OPEN]
if os.path.exists(fName):
    with open(fName, 'rb') as f:
        #add you code to handle the file contents here.
elif IOError:
    print "Unable to open file: "+str(fName)

This way you can attempt to open the file, but if it doesn't exist (if it raises an IOError), alert the user!

change pgsql port

There should be a line in your postgresql.conf file that says:

port = 1486

Change that.

The location of the file can vary depending on your install options. On Debian-based distros it is /etc/postgresql/8.3/main/

On Windows it is C:\Program Files\PostgreSQL\9.3\data

Don't forget to sudo service postgresql restart for changes to take effect.

Default keystore file does not exist?

For Mac/Linux debug keystore, the Android docs have:

keytool -exportcert -list -v \
-alias androiddebugkey -keystore ~/.android/debug.keystore

But there is something that may not be obvious: If you put the backslash, make sure to do a shift + return in terminal after the backslash so that the second that starts with -alias is on a new line. Simply pasting as-is will not work.

Your terminal (if successful) will look something like this:

$ keytool -exportcert -list -v \
? -alias androiddebugkey -keystore ~/.android/debug.keystore
Enter keystore password: 

The default debug password is: android

Side note: In Android Studio you can manage signing in:

File > Project Structure > Modules - (Your App) > Signing

What is the easiest way to remove all packages installed by pip?

This will work for all Mac, Windows, and Linux systems. To get the list of all pip packages in the requirements.txt file (Note: This will overwrite requirements.txt if exist else will create the new one, also if you don't want to replace old requirements.txt then give different file name in the all following command in place requirements.txt).

pip freeze > requirements.txt

Now to remove one by one

pip uninstall -r requirements.txt

If we want to remove all at once then

pip uninstall -r requirements.txt -y

If you're working on an existing project that has a requirements.txt file and your environment has diverged, simply replace requirements.txt from the above examples with toberemoved.txt. Then, once you have gone through the steps above, you can use the requirements.txt to update your now clean environment.

And For single command without creating any file (As @joeb suggested).

pip uninstall -y -r <(pip freeze)

How to determine if OpenSSL and mod_ssl are installed on Apache2

If you have PHP installed on your server, you can create a php file, let's called it phpinfo.php and add this <?php echo phpinfo();?>, and open the file in your browser, this shows information about your system environment, to quickly find info about your Apache loaded modules, locate 'Loaded Modules' on the resulting page.

MySQL Multiple Where Clause

SELECT a.image_id 
FROM list a
INNER JOIN list b
   ON a.image_id = b.image_id
   AND b.style_id = 25
   AND b.style_value = 'big'
INNER JOIN list c
   ON a.image_id = c.image_id
   AND c.style_id = 27
   AND c.style_value = 'round'
WHERE a.style_id = 24 
   AND a.style_value = 'red'

In Python, what is the difference between ".append()" and "+= []"?

let's take an example first

list1=[1,2,3,4]
list2=list1     (that means they points to same object)

if we do 
list1=list1+[5]    it will create a new object of list
print(list1)       output [1,2,3,4,5] 
print(list2)       output [1,2,3,4]

but if we append  then 
list1.append(5)     no new object of list created
print(list1)       output [1,2,3,4,5] 
print(list2)       output [1,2,3,4,5]

extend(list) also do the same work as append it just append a list instead of a 
single variable 

How to check if dropdown is disabled?

Try following or check demo disabled and readonly

$('#dropUnit').is(':disabled') //Returns bool
$('#dropUnit').attr('readonly') == "readonly"  //If Condition

You can check jQuery FAQ .

How to send parameters from a notification-click to an activity?

It's easy,this is my solution using objects!

My POJO

public class Person implements Serializable{

    private String name;
    private int age;

    //get & set

}

Method Notification

  Person person = new Person();
  person.setName("david hackro");
  person.setAge(10);

    Intent notificationIntent = new Intent(this, Person.class);
    notificationIntent.putExtra("person",person);
    notificationIntent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP | Intent.FLAG_ACTIVITY_CLEAR_TOP);

NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.mipmap.notification_icon)
                .setAutoCancel(true)
                .setColor(getResources().getColor(R.color.ColorTipografiaAdeudos))
                .setPriority(2)
                .setLargeIcon(bm)
                .setTicker(fotomulta.getTitle())
                .setContentText(fotomulta.getMessage())
                .setContentIntent(PendingIntent.getActivity(this, 0, notificationIntent, PendingIntent.FLAG_UPDATE_CURRENT))
                .setWhen(System.currentTimeMillis())
                .setContentTitle(fotomulta.getTicketText())
                .setDefaults(Notification.DEFAULT_ALL);

New Activity

 private Person person;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_notification_push);
    person = (Person) getIntent().getSerializableExtra("person");
}

Good Luck!!

Regex for Comma delimited list

This regex extracts an element from a comma separated list, regardless of contents:

(.+?)(?:,|$)

If you just replace the comma with something else, it should work for any delimiter.

How to check the version before installing a package using apt-get?

Linux Mint, Debian 9, Ubuntu 16.04 and older:

Short info:

apt policy <package_name>

Detailed info (With Description and Depends):

apt show <package_name>

Invoke-Command error "Parameter set cannot be resolved using the specified named parameters"

I was solving same problem recently. I was designing a write cmdlet for my Subtitle module. I had six different user stories:

  • Subtitle only
  • Subtitle and path (original file name is used)
  • Subtitle and new file name (original path is used)
  • Subtitle and name suffix is used (original path and modified name is used).
  • Subtile, new path and new file name is is used.
  • Subtitle, new path and suffix is used.

I end up in the big frustration because I though that 4 parameters will be enough. Like most of the times, the frustration was pointless because it was my fault. I didn't know enough about parameter sets.

After some research in documentation, I realized where is the problem. With knowledge how the parameter sets should be used, I developed a general and simple approach how to solve this problem. A pencil and a sheet of paper is required but a spreadsheet editor is better:

  1. Write down all intended ways how the cmdlet should be used => user stories.
  2. Keep adding parameters with meaningful names and mark the use of the parameters until you have a unique collection set => no repetitive combination of parameters.
  3. Implement parameter sets into your code.
  4. Prepare tests for all possible user stories.
  5. Run tests (big surprise, right?). IDEs doesn't checks parameter sets collision, tests could save lots of trouble later one.

Example:

Unique parameter binding resolution approach.

The practical example could be seen over here.

BTW: The parameter uniqueness within parameter sets is the reason why the ParameterSetName property doesn't support [String[]]. It doesn't really make any sense.

How to convert a date to milliseconds

You don't have a Date, you have a String representation of a date. You should convert the String into a Date and then obtain the milliseconds. To convert a String into a Date and vice versa you should use SimpleDateFormat class.

Here's an example of what you want/need to do (assuming time zone is not involved here):

String myDate = "2014/10/29 18:10:45";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = sdf.parse(myDate);
long millis = date.getTime();

Still, be careful because in Java the milliseconds obtained are the milliseconds between the desired epoch and 1970-01-01 00:00:00.


Using the new Date/Time API available since Java 8:

String myDate = "2014/10/29 18:10:45";
LocalDateTime localDateTime = LocalDateTime.parse(myDate,
    DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss") );
/*
  With this new Date/Time API, when using a date, you need to
  specify the Zone where the date/time will be used. For your case,
  seems that you want/need to use the default zone of your system.
  Check which zone you need to use for specific behaviour e.g.
  CET or America/Lima
*/
long millis = localDateTime
    .atZone(ZoneId.systemDefault())
    .toInstant().toEpochMilli();

How to document a method with parameter(s)?

Building upon the type-hints answer (https://stackoverflow.com/a/9195565/2418922), which provides a better structured way to document types of parameters, there exist also a structured manner to document both type and descriptions of parameters:

def copy_net(
    infile: (str, 'The name of the file to send'),
    host: (str, 'The host to send the file to'),
    port: (int, 'The port to connect to')):

    pass

example adopted from: https://pypi.org/project/autocommand/

What Process is using all of my disk IO

To find out which processes in state 'D' (waiting for disk response) are currently running:

while true; do date; ps aux | awk '{if($8=="D") print $0;}'; sleep 1; done

or

watch -n1 -d "ps axu | awk '{if (\$8==\"D\") {print \$0}}'"

Wed Aug 29 13:00:46 CLT 2012
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:00:47 CLT 2012
Wed Aug 29 13:00:48 CLT 2012
Wed Aug 29 13:00:49 CLT 2012
Wed Aug 29 13:00:50 CLT 2012
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:00:51 CLT 2012
Wed Aug 29 13:00:52 CLT 2012
Wed Aug 29 13:00:53 CLT 2012
Wed Aug 29 13:00:55 CLT 2012
Wed Aug 29 13:00:56 CLT 2012
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:00:57 CLT 2012
root       302  0.0  0.0      0     0 ?        D    May28   3:07  \_ [kdmflush]
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:00:58 CLT 2012
root       302  0.0  0.0      0     0 ?        D    May28   3:07  \_ [kdmflush]
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:00:59 CLT 2012
root       302  0.0  0.0      0     0 ?        D    May28   3:07  \_ [kdmflush]
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:01:00 CLT 2012
root       302  0.0  0.0      0     0 ?        D    May28   3:07  \_ [kdmflush]
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:01:01 CLT 2012
root       302  0.0  0.0      0     0 ?        D    May28   3:07  \_ [kdmflush]
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]
Wed Aug 29 13:01:02 CLT 2012
Wed Aug 29 13:01:03 CLT 2012
root       321  0.0  0.0      0     0 ?        D    May28   4:25  \_ [jbd2/dm-0-8]

As you can see from the result, the jdb2/dm-0-8 (ext4 journal process), and kdmflush are constantly block your Linux.

For more details this URL could be helpful: Linux Wait-IO Problem

Opening a folder in explorer and selecting a file

Use "/select,c:\file.txt"

Notice there should be a comma after /select instead of space..

XML Carriage return encoding

To insert a CR into XML, you need to use its character entity &#13;.

This is because compliant XML parsers must, before parsing, translate CRLF and any CR not followed by a LF to a single LF. This behavior is defined in the End-of-Line handling section of the XML 1.0 specification.

Double value to round up in Java

There is something fundamentally wrong with what you're trying to do. Binary floating-points values do not have decimal places. You cannot meaningfully round one to a given number of decimal places, because most "round" decimal values simply cannot be represented as a binary fraction. Which is why one should never use float or double to represent money.

So if you want decimal places in your result, that result must either be a String (which you already got with the DecimalFormat), or a BigDecimal (which has a setScale() method that does exactly what you want). Otherwise, the result cannot be what you want it to be.

Read The Floating-Point Guide for more information.

How to go from one page to another page using javascript?

Verifying that a user is an admin in javascript leads to trouble because javascript code is visible to anyone. The server is the one who should tell the difference between an admin and a regular user AFTER the login process and then generate the new page accordingly.

Maybe that's not what you are trying to do so to answer your question:

window.location.href="<the page you are going to>";

What characters are valid in a URL?

All the gory details can be found in the current RFC on the topic: RFC 3986 (Uniform Resource Identifier (URI): Generic Syntax)

Based on this related answer, you are looking at a list that looks like: A-Z, a-z, 0-9, -, ., _, ~, :, /, ?, #, [, ], @, !, $, &, ', (, ), *, +, ,, ;, %, and =. Everything else must be url-encoded. Also, some of these characters can only exist in very specific spots in a URI and outside of those spots must be url-encoded (e.g. % can only be used in conjunction with url encoding as in %20), the RFC has all of these specifics.

How do I check in JavaScript if a value exists at a certain array index?

With Lodash, you can do:

if(_.has(req,'documents')){
      if (req.documents.length)
      _.forEach(req.documents, function(document){
        records.push(document);
      });
} else {
}

if(_.has(req,'documents')) is to check whether our request object has a property named documents and if it has that prop, the next if (req.documents.length) is to validate if it is not an empty array, so the other stuffs like forEach can be proceeded.

Python error: AttributeError: 'module' object has no attribute

The way I would do it is to leave the __ init__.py files empty, and do:

import lib.mod1.mod11
lib.mod1.mod11.mod12()

or

from lib.mod1.mod11 import mod12
mod12()

You may find that the mod1 dir is unnecessary, just have mod12.py in lib.

What causes javac to issue the "uses unchecked or unsafe operations" warning

If you do what it suggests and recompile with the "-Xlint:unchecked" switch, it will give you more detailed information.

As well as the use of raw types (as described by the other answers), an unchecked cast can also cause the warning.

Once you've compiled with -Xlint, you should be able to rework your code to avoid the warning. This is not always possible, particularly if you are integrating with legacy code that cannot be changed. In this situation, you may decide to suppress the warning in places where you know that the code is correct:

@SuppressWarnings("unchecked")
public void myMethod()
{
    //...
}

How do I authenticate a WebClient request?

You need to give the WebClient object the credentials. Something like this...

 WebClient client = new WebClient();
 client.Credentials = new NetworkCredential("username", "password");

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoRestController'

Your DemoApplication class is in the com.ag.digital.demo.boot package and your LoginBean class is in the com.ag.digital.demo.bean package. By default components (classes annotated with @Component) are found if they are in the same package or a sub-package of your main application class DemoApplication. This means that LoginBean isn't being found so dependency injection fails.

There are a couple of ways to solve your problem:

  1. Move LoginBean into com.ag.digital.demo.boot or a sub-package.
  2. Configure the packages that are scanned for components using the scanBasePackages attribute of @SpringBootApplication that should be on DemoApplication.

A few of other things that aren't causing a problem, but are not quite right with the code you've posted:

  • @Service is a specialisation of @Component so you don't need both on LoginBean
  • Similarly, @RestController is a specialisation of @Component so you don't need both on DemoRestController
  • DemoRestController is an unusual place for @EnableAutoConfiguration. That annotation is typically found on your main application class (DemoApplication) either directly or via @SpringBootApplication which is a combination of @ComponentScan, @Configuration, and @EnableAutoConfiguration.

Process to convert simple Python script into Windows executable

I would join @Nicholas in recommending PyInstaller (with the --onefile flag), but be warned: do not use the "latest release", PyInstaller 1.3 -- it's years old. Use the "pre-release" 1.4, download it here -- or even better the code from the svn repo -- install SVN and run svn co http://svn.pyinstaller.org/trunk pyinstaller.

As @Nicholas implies, dynamic libraries cannot be run from the same file as the rest of the executable -- but fortunately they can be packed together with all the rest in a "self-unpacking" executable that will unpack itself into some temporary directory as needed; PyInstaller does a good job at this (and at many other things -- py2exe is more popular, but pyinstaller in my opinion is preferable in all other respects).

Dynamically load a function from a DLL

This is not exactly a hot topic, but I have a factory class that allows a dll to create an instance and return it as a DLL. It is what I came looking for but couldn't find exactly.

It is called like,

IHTTP_Server *server = SN::SN_Factory<IHTTP_Server>::CreateObject();
IHTTP_Server *server2 =
      SN::SN_Factory<IHTTP_Server>::CreateObject(IHTTP_Server_special_entry);

where IHTTP_Server is the pure virtual interface for a class created either in another DLL, or the same one.

DEFINE_INTERFACE is used to give a class id an interface. Place inside interface;

An interface class looks like,

class IMyInterface
{
    DEFINE_INTERFACE(IMyInterface);

public:
    virtual ~IMyInterface() {};

    virtual void MyMethod1() = 0;
    ...
};

The header file is like this

#if !defined(SN_FACTORY_H_INCLUDED)
#define SN_FACTORY_H_INCLUDED

#pragma once

The libraries are listed in this macro definition. One line per library/executable. It would be cool if we could call into another executable.

#define SN_APPLY_LIBRARIES(L, A)                          \
    L(A, sn, "sn.dll")                                    \
    L(A, http_server_lib, "http_server_lib.dll")          \
    L(A, http_server, "")

Then for each dll/exe you define a macro and list its implementations. Def means that it is the default implementation for the interface. If it is not the default, you give a name for the interface used to identify it. Ie, special, and the name will be IHTTP_Server_special_entry.

#define SN_APPLY_ENTRYPOINTS_sn(M)                                     \
    M(IHTTP_Handler, SNI::SNI_HTTP_Handler, sn, def)                   \
    M(IHTTP_Handler, SNI::SNI_HTTP_Handler, sn, special)

#define SN_APPLY_ENTRYPOINTS_http_server_lib(M)                        \
    M(IHTTP_Server, HTTP::server::server, http_server_lib, def)

#define SN_APPLY_ENTRYPOINTS_http_server(M)

With the libraries all setup, the header file uses the macro definitions to define the needful.

#define APPLY_ENTRY(A, N, L) \
    SN_APPLY_ENTRYPOINTS_##N(A)

#define DEFINE_INTERFACE(I) \
    public: \
        static const long Id = SN::I##_def_entry; \
    private:

namespace SN
{
    #define DEFINE_LIBRARY_ENUM(A, N, L) \
        N##_library,

This creates an enum for the libraries.

    enum LibraryValues
    {
        SN_APPLY_LIBRARIES(DEFINE_LIBRARY_ENUM, "")
        LastLibrary
    };

    #define DEFINE_ENTRY_ENUM(I, C, L, D) \
        I##_##D##_entry,

This creates an enum for interface implementations.

    enum EntryValues
    {
        SN_APPLY_LIBRARIES(APPLY_ENTRY, DEFINE_ENTRY_ENUM)
        LastEntry
    };

    long CallEntryPoint(long id, long interfaceId);

This defines the factory class. Not much to it here.

    template <class I>
    class SN_Factory
    {
    public:
        SN_Factory()
        {
        }

        static I *CreateObject(long id = I::Id )
        {
            return (I *)CallEntryPoint(id, I::Id);
        }
    };
}

#endif //SN_FACTORY_H_INCLUDED

Then the CPP is,

#include "sn_factory.h"

#include <windows.h>

Create the external entry point. You can check that it exists using depends.exe.

extern "C"
{
    __declspec(dllexport) long entrypoint(long id)
    {
        #define CREATE_OBJECT(I, C, L, D) \
            case SN::I##_##D##_entry: return (int) new C();

        switch (id)
        {
            SN_APPLY_CURRENT_LIBRARY(APPLY_ENTRY, CREATE_OBJECT)
        case -1:
        default:
            return 0;
        }
    }
}

The macros set up all the data needed.

namespace SN
{
    bool loaded = false;

    char * libraryPathArray[SN::LastLibrary];
    #define DEFINE_LIBRARY_PATH(A, N, L) \
        libraryPathArray[N##_library] = L;

    static void LoadLibraryPaths()
    {
        SN_APPLY_LIBRARIES(DEFINE_LIBRARY_PATH, "")
    }

    typedef long(*f_entrypoint)(long id);

    f_entrypoint libraryFunctionArray[LastLibrary - 1];
    void InitlibraryFunctionArray()
    {
        for (long j = 0; j < LastLibrary; j++)
        {
            libraryFunctionArray[j] = 0;
        }

        #define DEFAULT_LIBRARY_ENTRY(A, N, L) \
            libraryFunctionArray[N##_library] = &entrypoint;

        SN_APPLY_CURRENT_LIBRARY(DEFAULT_LIBRARY_ENTRY, "")
    }

    enum SN::LibraryValues libraryForEntryPointArray[SN::LastEntry];
    #define DEFINE_ENTRY_POINT_LIBRARY(I, C, L, D) \
            libraryForEntryPointArray[I##_##D##_entry] = L##_library;
    void LoadLibraryForEntryPointArray()
    {
        SN_APPLY_LIBRARIES(APPLY_ENTRY, DEFINE_ENTRY_POINT_LIBRARY)
    }

    enum SN::EntryValues defaultEntryArray[SN::LastEntry];
        #define DEFINE_ENTRY_DEFAULT(I, C, L, D) \
            defaultEntryArray[I##_##D##_entry] = I##_def_entry;

    void LoadDefaultEntries()
    {
        SN_APPLY_LIBRARIES(APPLY_ENTRY, DEFINE_ENTRY_DEFAULT)
    }

    void Initialize()
    {
        if (!loaded)
        {
            loaded = true;
            LoadLibraryPaths();
            InitlibraryFunctionArray();
            LoadLibraryForEntryPointArray();
            LoadDefaultEntries();
        }
    }

    long CallEntryPoint(long id, long interfaceId)
    {
        Initialize();

        // assert(defaultEntryArray[id] == interfaceId, "Request to create an object for the wrong interface.")
        enum SN::LibraryValues l = libraryForEntryPointArray[id];

        f_entrypoint f = libraryFunctionArray[l];
        if (!f)
        {
            HINSTANCE hGetProcIDDLL = LoadLibraryA(libraryPathArray[l]);

            if (!hGetProcIDDLL) {
                return NULL;
            }

            // resolve function address here
            f = (f_entrypoint)GetProcAddress(hGetProcIDDLL, "entrypoint");
            if (!f) {
                return NULL;
            }
            libraryFunctionArray[l] = f;
        }
        return f(id);
    }
}

Each library includes this "cpp" with a stub cpp for each library/executable. Any specific compiled header stuff.

#include "sn_pch.h"

Setup this library.

#define SN_APPLY_CURRENT_LIBRARY(L, A) \
    L(A, sn, "sn.dll")

An include for the main cpp. I guess this cpp could be a .h. But there are different ways you could do this. This approach worked for me.

#include "../inc/sn_factory.cpp"

How can I bind to the change event of a textarea in jQuery?

Try this

 $('textarea').trigger('change');
 $("textarea").bind('cut paste', function(e) { });

$(window).height() vs $(document).height

This fixed me

var width = window.innerWidth;
var height = window.innerHeight;

Sending GET request with Authentication headers using restTemplate

You're not missing anything. RestTemplate#exchange(..) is the appropriate method to use to set request headers.

Here's an example (with POST, but just change that to GET and use the entity you want).

Here's another example.

Note that with a GET, your request entity doesn't have to contain anything (unless your API expects it, but that would go against the HTTP spec). It can be an empty String.

react-native :app:installDebug FAILED

Just lock and unlock the android solved my issue then

adb reverse tcp:8081 tcp:8081

How to print a int64_t type in C

For int64_t type:

#include <inttypes.h>
int64_t t;
printf("%" PRId64 "\n", t);

for uint64_t type:

#include <inttypes.h>
uint64_t t;
printf("%" PRIu64 "\n", t);

you can also use PRIx64 to print in hexadecimal.

cppreference.com has a full listing of available macros for all types including intptr_t (PRIxPTR). There are separate macros for scanf, like SCNd64.


A typical definition of PRIu16 would be "hu", so implicit string-constant concatenation happens at compile time.

For your code to be fully portable, you must use PRId32 and so on for printing int32_t, and "%d" or similar for printing int.

Warning comparison between pointer and integer

It should be

if (*message == '\0')

In C, simple quotes delimit a single character whereas double quotes are for strings.

Matplotlib transparent line plots

After I plotted all the lines, I was able to set the transparency of all of them as follows:

for l in fig_field.gca().lines:
    l.set_alpha(.7)

EDIT: please see Joe's answer in the comments.

SQL Query for Selecting Multiple Records

If you know the list of ids try this query:

SELECT * FROM `Buses` WHERE BusId IN (`list of busIds`)

or if you pull them from another table list of busIds could be another subquery:

SELECT * FROM `Buses` WHERE BusId IN (SELECT SomeId from OtherTable WHERE something = somethingElse)

If you need to compare to another table you need a join:

SELECT * FROM `Buses` JOIN OtheTable on Buses.BusesId = OtehrTable.BusesId

SQLite add Primary Key

I tried to add the primary key afterwards by changing the sqlite_master table directly. This trick seems to work. It is a hack solution of course.

In short: create a regular (unique) index on the table, then make the schema writable and change the name of the index to the form reserved by sqlite to identify a primary key index, (i.e. sqlite_autoindex_XXX_1, where XXX is the table name) and set the sql string to NULL. At last change the table definition itself. One pittfal: sqlite does not see the index name change until the database is reopened. This seems like a bug, but not a severe one (even without reopening the database, you can still use it).

Suppose the table looks like:

CREATE TABLE tab1(i INTEGER, j INTEGER, t TEXT);

Then I did the following:

BEGIN;
CREATE INDEX pk_tab1 ON tab1(i,j);
pragma writable_schema=1;
UPDATE sqlite_master SET name='sqlite_autoindex_tab1_1',sql=null WHERE name='pk_tab1';
UPDATE sqlite_master SET sql='CREATE TABLE tab1(i integer,j integer,t text,primary key(i,j))' WHERE name='tab1';
COMMIT;

Some tests (in sqlite shell):

sqlite> explain query plan select * from tab1 order by i,j;
0|0|0|SCAN TABLE tab1 USING INDEX sqlite_autoindex_tab1_1
sqlite> drop index sqlite_autoindex_tab1_1;
Error: index associated with UNIQUE or PRIMARY KEY constraint cannot be dropped    

How to check if internet connection is present in Java?

You can simply write like this

import java.net.InetAddress;
import java.net.UnknownHostException;

public class Main {

    private static final String HOST = "localhost";

    public static void main(String[] args) throws UnknownHostException {

        boolean isConnected = !HOST.equals(InetAddress.getLocalHost().getHostAddress().toString());

        if (isConnected) System.out.println("Connected");
        else System.out.println("Not connected");

    }
}

How to join two sets in one line without using "|"

If you are fine with modifying the original set (which you may want to do in some cases), you can use set.update():

S.update(T)

The return value is None, but S will be updated to be the union of the original S and T.

Find stored procedure by name

You can use:

select * 
from 
   sys.procedures 
where 
   name like '%name_of_proc%'

if you need the code you can look in the syscomments table

select text 
from 
    syscomments c
    inner join sys.procedures p on p.object_id = c.object_id
where 
    p.name like '%name_of_proc%'

Edit Update:

you can can also use the ansi standard version

SELECT * 
FROM 
    INFORMATION_SCHEMA.ROUTINES 
WHERE 
    ROUTINE_NAME LIKE '%name_of_proc%'

JPQL IN clause: Java-Arrays (or Lists, Sets...)?

I'm not sure for JPA 1.0 but you can pass a Collection in JPA 2.0:

String qlString = "select item from Item item where item.name IN :names"; 
Query q = em.createQuery(qlString, Item.class);

List<String> names = Arrays.asList("foo", "bar");

q.setParameter("names", names);
List<Item> actual = q.getResultList();

assertNotNull(actual);
assertEquals(2, actual.size());

Tested with EclipseLInk. With Hibernate 3.5.1, you'll need to surround the parameter with parenthesis:

String qlString = "select item from Item item where item.name IN (:names)";

But this is a bug, the JPQL query in the previous sample is valid JPQL. See HHH-5126.

Working with select using AngularJS's ng-options

The question is already answered (BTW, really good and comprehensive answer provided by Ben), but I would like to add another element for completeness, which may be also very handy.

In the example suggested by Ben:

<select ng-model="blah" ng-options="item.ID as item.Title for item in items"></select>

the following ngOptions form has been used: select as label for value in array.

Label is an expression, which result will be the label for <option> element. In that case you can perform certain string concatenations, in order to have more complex option labels.

Examples:

  • ng-options="item.ID as item.Title + ' - ' + item.ID for item in items" gives you labels like Title - ID
  • ng-options="item.ID as item.Title + ' (' + item.Title.length + ')' for item in items" gives you labels like Title (X), where X is length of Title string.

You can also use filters, for example,

  • ng-options="item.ID as item.Title + ' (' + (item.Title | uppercase) + ')' for item in items" gives you labels like Title (TITLE), where Title value of Title property and TITLE is the same value but converted to uppercase characters.
  • ng-options="item.ID as item.Title + ' (' + (item.SomeDate | date) + ')' for item in items" gives you labels like Title (27 Sep 2015), if your model has a property SomeDate

copy all files and folders from one drive to another drive using DOS (command prompt)

This worked for me On Windows 10,

xcopy /s {source drive..i.e. C:} {destination drive..i.e. D:} This will copy all the files and folders plus the folder contents.

How to add 'libs' folder in Android Studio?

You can create lib folder inside app you press right click and select directory you named as libs its will be worked

In Android, how do I set margins in dp programmatically?

((FrameLayout.LayoutParams) linearLayout.getLayoutParams()).setMargins(450, 20, 0, 250);
        linearLayout.setBackgroundResource(R.drawable.smartlight_background);

I had to cast mine to FrameLayout for a linearLayout as it inherits from it and set margins there so the activity appears only on part of the screen along with a different background than the original layout params in the setContentView.

LinearLayout linearLayout = (LinearLayout) findViewById(R.id.activity);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(WindowManager.LayoutParams.FILL_PARENT, WindowManager.LayoutParams.MATCH_PARENT);
linearLayout.setBackgroundColor(getResources().getColor(R.color.full_white));
setContentView(linearLayout,layoutParams);

None of the others worked for using the same activity and changing the margins based on opening the activity from a different menu! setLayoutParams never worked for me - the device would crash every single time. Even though these are hardcoded numbers - this is only an example of the code for demonstration purposes only.

ng-repeat :filter by single field

my way is this

subjcts is

[{"id":"1","title":"GFATM"},{"id":"2","title":"Court Case"},{"id":"3","title":"Renewal\/Validity"},{"id":"4","title":"Change of Details"},{"id":"5","title":"Student Query"},{"id":"6","title":"Complains"}]

sub is a Input field or whatever you like

Displaying like this

<div ng-if="x.id === sub" ng-repeat=" x in subjcts">{{x.title}}</div>

Creating a URL in the controller .NET MVC

Another way to create an absolute URL to an action:

var relativeUrl = Url.Action("MyAction");  //..or one of the other .Action() overloads
var currentUrl = Request.Url;

var absoluteUrl = new System.Uri(currentUrl, relativeUrl);

UICollectionView spacing margins

use setMinimumLineSpacing: and setMinimumInteritemSpacing: on the UICollectionViewFlowLayout-Object.

How to convert list data into json in java

Try like below with Gson Library.

Earlier Conversion List format were:

[Product [Id=1, City=Bengalore, Category=TV, Brand=Samsung, Name=Samsung LED, Type=LED, Size=32 inches, Price=33500.5, Stock=17.0], Product [Id=2, City=Bengalore, Category=TV, Brand=Samsung, Name=Samsung LED, Type=LED, Size=42 inches, Price=41850.0, Stock=9.0]]

and here the conversion source begins.

//** Note I have created the method toString() in Product class.

//Creating and initializing a java.util.List of Product objects
List<Product> productList = (List<Product>)productRepository.findAll();

//Creating a blank List of Gson library JsonObject
List<JsonObject> entities = new ArrayList<JsonObject>();

//Simply printing productList size
System.out.println("Size of productList is : " + productList.size());

//Creating a Iterator for productList
Iterator<Product> iterator = productList.iterator();

//Run while loop till Product Object exists.
while(iterator.hasNext()){

    //Creating a fresh Gson Object
    Gson gs = new Gson();

    //Converting our Product Object to JsonElement 
    //Object by passing the Product Object String value (iterator.next())
    JsonElement element = gs.fromJson (gs.toJson(iterator.next()), JsonElement.class);

    //Creating JsonObject from JsonElement
    JsonObject jsonObject = element.getAsJsonObject();

    //Collecting the JsonObject to List
    entities.add(jsonObject);

}

//Do what you want to do with Array of JsonObject
System.out.println(entities);

Converted Json Result is :

[{"Id":1,"City":"Bengalore","Category":"TV","Brand":"Samsung","Name":"Samsung LED","Type":"LED","Size":"32 inches","Price":33500.5,"Stock":17.0}, {"Id":2,"City":"Bengalore","Category":"TV","Brand":"Samsung","Name":"Samsung LED","Type":"LED","Size":"42 inches","Price":41850.0,"Stock":9.0}]

Hope this would help many guys!

Call and receive output from Python script in Java?

ProcessBuilder is very easy to use.

ProcessBuilder pb = new ProcessBuilder("python","Your python file",""+Command line arguments if any);
Process p = pb.start();

This should call python. Refer to the process approach here for full example!

https://bytes.com/topic/python/insights/949995-three-ways-run-python-programs-java

How to study design patterns?

Practice, practice, practice.

You can read about playing the cello for years, and still not be able to put a bow to instrument and make anything that sounds like music.

Design patterns are best recognized as a high-level issue; one that is only relevant if you have the experience necessary to recognize them as useful. It's good that you recognize that they're useful, but unless you've seen situations where they would apply, or have applied, it's almost impossible to understand their true value.

Where they become useful is when you recognize design patterns in others' code, or recognize a problem in the design phase that fits well with a pattern; and then examine the formal pattern, and examine the problem, and determine what the delta is between them, and what that says about both the pattern and the problem.

It's really the same as coding; K&R may be the "bible" for C, but reading it cover-to-cover several times just doesn't give one practical experience; there's no replacement for experience.

How do you change the width and height of Twitter Bootstrap's tooltips?

On BS3

.tooltip-inner {
    min-width: 150px; /* the minimum width */
}

Linux find and grep command together

You are looking for -H option in gnu grep.

find . -name '*bills*' -exec grep -H "put" {} \;

Here is the explanation

    -H, --with-filename
      Print the filename for each match.

Phone Number Validation MVC

Try for simple regular expression for Mobile No

[Required (ErrorMessage="Required")]
[RegularExpression(@"^(\d{10})$", ErrorMessage = "Wrong mobile")]
public string Mobile { get; set; }

How to get POSTed JSON in Flask?

For all those whose issue was from the ajax call, here is a full example :

Ajax call : the key here is to use a dict and then JSON.stringify

    var dict = {username : "username" , password:"password"};

    $.ajax({
        type: "POST", 
        url: "http://127.0.0.1:5000/", //localhost Flask
        data : JSON.stringify(dict),
        contentType: "application/json",
    });

And on server side :

from flask import Flask
from flask import request
import json

app = Flask(__name__)

@app.route("/",  methods = ['POST'])
def hello():
    print(request.get_json())
    return json.dumps({'success':True}), 200, {'ContentType':'application/json'} 

if __name__ == "__main__":
    app.run()

excel - if cell is not blank, then do IF statement

You need to use AND statement in your formula

=IF(AND(IF(NOT(ISBLANK(Q2));TRUE;FALSE);Q2<=R2);"1";"0")

And if both conditions are met, return 1.

You could also add more conditions in your AND statement.

How do I remove all non alphanumeric characters from a string except dash?

The regex is [^\w\s\-]*:

\s is better to use instead of space (), because there might be a tab in the text.

Remap values in pandas column with a dict

Or do apply:

df['col1'].apply(lambda x: {1: "A", 2: "B"}.get(x,x))

Demo:

>>> df['col1']=df['col1'].apply(lambda x: {1: "A", 2: "B"}.get(x,x))
>>> df
  col1 col2
0    w    a
1    1    2
2    2  NaN
>>> 

Angular 4 setting selected option in Dropdown

To preselect an option when the form is initialized, the value of the select element must be set to an element attribute of the array you are iterating over and setting the value of option to. Which is the key attribute in this case.

From your example.

<select [id]="question.key" [formControlName]="question.key">
  <option *ngFor="let opt of question.options" [value]="opt.key"</option>
</select>

You are iterating over 'options' to create the select options. So the value of select must be set to the key attribute of an item in options(the one you want to display on initialization). This will display the default of select as the option whose value matches the value you set for select.

You can achieve this by setting the value of the select element in the onInit method like so.

ngOnInit(): void{
    myForm : new FormGroup({
       ...
       question.key : new FormControl(null)
    })
    // Get desired initial value to display on <select>
    desiredValue = question.options.find(opt => opt === initialValue)
    this.myForm.get(question.key).setValue(desiredValue.key)
}

How to deploy ASP.NET webservice to IIS 7?

  1. rebuild project in VS
  2. copy project folder to iis folder, probably C:\inetpub\wwwroot\
  3. in iis manager (run>inetmgr) add website, point to folder, point application pool based on your .net
  4. add web service to created website, almost the same as 3.
  5. INSTALL ASP for windows 7 and .net 4.0: c:\windows\microsoft.net framework\v4.(some numbers)\regiis.exe -i
  6. check access to web service on your browser

MySQL load NULL values from CSV data

The behaviour is different depending upon the database configuration. In the strict mode this would throw an error else a warning. Following query may be used for identifying the database configuration.

mysql> show variables like 'sql_mode';

Which JRE am I using?

The following command will tell you a lot of information about your java version, including the vendor:

java -XshowSettings:properties -version

It works on Windows, Mac, and Linux.

Left align and right align within div in Bootstrap

2021 Update...

Bootstrap 5 (beta)

For aligning within a flexbox div or row...

  • ml-auto is now ms-auto
  • mr-auto is now me-auto

Bootstrap 4+

  • pull-right is now float-right
  • text-right is the same as 3.x, and works for inline elements
  • both float-* and text-* are responsive for different alignment at different widths (ie: float-sm-right)

The flexbox utils (eg:justify-content-between) can also be used for alignment:

<div class="d-flex justify-content-between">
      <div>
         left
      </div>
      <div>
         right
      </div>
 </div>

or, auto-margins (eg:ml-auto) in any flexbox container (row,navbar,card,d-flex,etc...)

<div class="d-flex">
      <div>
         left
      </div>
      <div class="ml-auto">
         right
      </div>
 </div>

Bootstrap 4 Align Demo
Bootstrap 4 Right Align Examples(float, flexbox, text-right, etc...)


Bootstrap 3

Use the pull-right class..

<div class="container">
  <div class="row">
    <div class="col-md-6">Total cost</div>
    <div class="col-md-6"><span class="pull-right">$42</span></div>
  </div>
</div>

Bootstrap 3 Demo

You can also use the text-right class like this:

  <div class="row">
    <div class="col-md-6">Total cost</div>
    <div class="col-md-6 text-right">$42</div>
  </div>

Bootstrap 3 Demo 2

Call An Asynchronous Javascript Function Synchronously

"don't tell me about how I should just do it "the right way" or whatever"

OK. but you should really do it the right way... or whatever

" I need a concrete example of how to make it block ... WITHOUT freezing the UI. If such a thing is possible in JS."

No, it is impossible to block the running JavaScript without blocking the UI.

Given the lack of information, it's tough to offer a solution, but one option may be to have the calling function do some polling to check a global variable, then have the callback set data to the global.

function doSomething() {

      // callback sets the received data to a global var
  function callBack(d) {
      window.data = d;
  }
      // start the async
  myAsynchronousCall(param1, callBack);

}

  // start the function
doSomething();

  // make sure the global is clear
window.data = null

  // start polling at an interval until the data is found at the global
var intvl = setInterval(function() {
    if (window.data) { 
        clearInterval(intvl);
        console.log(data);
    }
}, 100);

All of this assumes that you can modify doSomething(). I don't know if that's in the cards.

If it can be modified, then I don't know why you wouldn't just pass a callback to doSomething() to be called from the other callback, but I better stop before I get into trouble. ;)


Oh, what the heck. You gave an example that suggests it can be done correctly, so I'm going to show that solution...

function doSomething( func ) {

  function callBack(d) {
    func( d );
  }

  myAsynchronousCall(param1, callBack);

}

doSomething(function(data) {
    console.log(data);
});

Because your example includes a callback that is passed to the async call, the right way would be to pass a function to doSomething() to be invoked from the callback.

Of course if that's the only thing the callback is doing, you'd just pass func directly...

myAsynchronousCall(param1, func);

How to solve “Microsoft Visual Studio (VS)” error “Unable to connect to the configured development Web server”

We solved this problem with deleting .vs folder on project folder and deleting temporary ASP.NET files.

1. Close the Visual Studio.
2. Delete .vs folder on project folder that includes applicationhost.config file.
3. Delete temporary ASP.NET Files located: C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root

How to check if an object implements an interface?

In general for AnInterface and anInstance of any class:

AnInterface.class.isAssignableFrom(anInstance.getClass());

R: Select values from data table in range

Lots of options here, but one of the easiest to follow is subset. Consider:

> set.seed(43)
> df <- data.frame(name = sample(letters, 100, TRUE), date = sample(1:500, 100, TRUE))
> 
> subset(df, date > 5 & date < 15)
   name date
11    k   10
67    y   12
86    e    8

You can also insert logic directly into the index for your data.frame. The comma separates the rows from columns. We just have to remember that R indexes rows first, then columns. So here we are saying rows with date > 5 & < 15 and then all columns:

df[df$date > 5 & df$date < 15 ,]

I'd also recommend checking out the help pages for subset, ?subset and the logical operators ?"&"

Delete a row in Excel VBA

Something like this will do it:

Rows("12:12").Select
Selection.Delete

So in your code it would look like something like this:

Rows(CStr(rand) & ":" & CStr(rand)).Select
Selection.Delete

Greyscale Background Css Images

You don't need to use complicated coding really!

Greyscale Hover:

-webkit-filter: grayscale(100%);

Greyscale "Hover-out":

-webkit-filter: grayscale(0%);


I simply made my css class have a separate hover class and added in the second greyscale. It's really simple if you really don't like complexity.

Using curl to upload POST data with files

You need to use the -F option:
-F/--form <name=content> Specify HTTP multipart POST data (H)

Try this:

curl \
  -F "userid=1" \
  -F "filecomment=This is an image file" \
  -F "image=@/home/user1/Desktop/test.jpg" \
  localhost/uploader.php

NTFS performance and large volumes of files and directories

For local access, large numbers of directories/files doesn't seem to be an issue. However, if you're accessing it across a network, there's a noticeable performance hit after a few hundred (especially when accessed from Vista machines (XP to Windows Server w/NTFS seemed to run much faster in that regard)).

Transparent CSS background color

yes, thats possible. just use the rgba-syntax for your background-color.

.menue{
  background-color: rgba(255, 0, 0, 0.5); //semi-transparent red
}

How can I split a JavaScript string by white space or comma?

"my, tags are, in here".split(/[ ,]+/)

the result is :

["my", "tags", "are", "in", "here"]

How to monitor network calls made from iOS Simulator

A free and open source proxy tool that runs easily on a Mac is mitmproxy.

The website includes links to a Mac binary, as well as the source code on Github.

The docs contain a very helpful intro to loading a cert into your test device to view HTTPS traffic.

Not quite as GUI-tastic as Charles, but it does everything I need and its free and maintained. Good stuff, and pretty straightforward if you've used some command line tools before.

UPDATE: I just noticed on the website that mitmproxy is available as a homebrew install. Couldn't be easier.

With arrays, why is it the case that a[5] == 5[a]?

For pointers in C, we have

a[5] == *(a + 5)

and also

5[a] == *(5 + a)

Hence it is true that a[5] == 5[a].

How to figure out the SMTP server host?

To automate the answer of @Jordan S. Jones at WIN/DOS command-line,

Put this in a batch file named: getmns.bat (get mail name server):

@echo off
if @%1==@ goto USAGE
echo set type=MX>mnscmd.txt
echo %1>>mnscmd.txt
echo exit>>mnscmd.txt
nslookup<mnscmd.txt>mnsresult.txt
type mnsresult.txt
del mnsresult.txt
goto END
:USAGE
echo usage:
echo %0 domainname.ext
:END
echo.

For example:

getmns google.com

output:

google.com      MX preference = 20, mail exchanger = alt1.aspmx.l.google.com
google.com      MX preference = 10, mail exchanger = aspmx.l.google.com
google.com      MX preference = 50, mail exchanger = alt4.aspmx.l.google.com
google.com      MX preference = 40, mail exchanger = alt3.aspmx.l.google.com
google.com      MX preference = 30, mail exchanger = alt2.aspmx.l.google.com

alt4.aspmx.l.google.com internet address = 74.125.25.27
alt3.aspmx.l.google.com internet address = 173.194.72.27
aspmx.l.google.com      internet address = 173.194.65.27
alt1.aspmx.l.google.com internet address = 74.125.200.27
alt2.aspmx.l.google.com internet address = 64.233.187.27

For example to pipe the result again into a file do:

getmns google.com > google.mns.txt

:-D

What is ROWS UNBOUNDED PRECEDING used for in Teradata?

ROWS UNBOUNDED PRECEDING is no Teradata-specific syntax, it's Standard SQL. Together with the ORDER BY it defines the window on which the result is calculated.

Logically a Windowed Aggregate Function is newly calculated for each row within the PARTITION based on all ROWS between a starting row and an ending row.

Starting and ending rows might be fixed or relative to the current row based on the following keywords:

  • CURRENT ROW, the current row
  • UNBOUNDED PRECEDING, all rows before the current row -> fixed
  • UNBOUNDED FOLLOWING, all rows after the current row -> fixed
  • x PRECEDING, x rows before the current row -> relative
  • y FOLLOWING, y rows after the current row -> relative

Possible kinds of calculation include:

  • Both starting and ending row are fixed, the window consists of all rows of a partition, e.g. a Group Sum, i.e. aggregate plus detail rows
  • One end is fixed, the other relative to current row, the number of rows increases or decreases, e.g. a Running Total, Remaining Sum
  • Starting and ending row are relative to current row, the number of rows within a window is fixed, e.g. a Moving Average over n rows

So SUM(x) OVER (ORDER BY col ROWS UNBOUNDED PRECEDING) results in a Cumulative Sum or Running Total

11 -> 11
 2 -> 11 +  2                = 13
 3 -> 13 +  3 (or 11+2+3)    = 16
44 -> 16 + 44 (or 11+2+3+44) = 60

Keeping ASP.NET Session Open / Alive

[Late to the party...]

Another way to do this without the overhead of an Ajax call or WebService handler is to load a special ASPX page after a given amount of time (i.e., prior to the session state time-out, which is typically 20 minutes):

// Client-side JavaScript
function pingServer() {
    // Force the loading of a keep-alive ASPX page
    var img = new Image(1, 1);
    img.src = '/KeepAlive.aspx';
}

The KeepAlive.aspx page is simply an empty page which does nothing but touch/refresh the Session state:

// KeepAlive.aspx.cs
public partial class KeepSessionAlive: System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // Refresh the current user session
        Session["refreshTime"] = DateTime.UtcNow;
    }
}

This works by creating an img (image) element and forcing the browser to load its contents from the KeepAlive.aspx page. Loading that page causes the server to touch (update) the Session object, extending the session's expiration sliding time window (typically by another 20 minutes). The actual web page contents are discarded by the browser.

An alternative, and perhaps cleaner, way to do this is to create a new iframe element and load the KeepAlive.aspx page into it. The iframe element is hidden, such as by making it a child element of a hidden div element somewhere on the page.

Activity on the page itself can be detected by intercepting mouse and keyboard actions for the entire page body:

// Called when activity is detected
function activityDetected(evt) {
    ...
}

// Watch for mouse or keyboard activity
function watchForActivity() {
    var opts = { passive: true };
    document.body.addEventListener('mousemove', activityDetected, opts);
    document.body.addEventListener('keydown', activityDetected, opts);
}

I cannot take credit for this idea; see: https://www.codeproject.com/Articles/227382/Alert-Session-Time-out-in-ASP-Net.

Duplicate headers received from server

Just put a pair of double quotes around your file name like this:

this.Response.AddHeader("Content-disposition", $"attachment; filename=\"{outputFileName}\"");

How to convert enum value to int?

Sometime some C# approach makes the life easier in Java world..:

class XLINK {
static final short PAYLOAD = 102, ACK = 103, PAYLOAD_AND_ACK = 104;
}
//Now is trivial to use it like a C# enum:
int rcv = XLINK.ACK;

jQuery callback for multiple ajax calls

I got some good hints from the answers on this page. I adapted it a bit for my use and thought I could share.

// lets say we have 2 ajax functions that needs to be "synchronized". 
// In other words, we want to know when both are completed.
function foo1(callback) {
    $.ajax({
        url: '/echo/html/',
        success: function(data) {
            alert('foo1');
            callback();               
        }
    });
}

function foo2(callback) {
    $.ajax({
        url: '/echo/html/',
        success: function(data) {
            alert('foo2');
            callback();
        }
    });
}

// here is my simplified solution
ajaxSynchronizer = function() {
    var funcs = [];
    var funcsCompleted = 0;
    var callback;

    this.add = function(f) {
        funcs.push(f);
    }

    this.synchronizer = function() {
        funcsCompleted++;
        if (funcsCompleted == funcs.length) {
            callback.call(this);
        }
    }

    this.callWhenFinished = function(cb) {
        callback = cb;
        for (var i = 0; i < funcs.length; i++) {
            funcs[i].call(this, this.synchronizer);
        }
    }
}

// this is the function that is called when both ajax calls are completed.
afterFunction = function() {
    alert('All done!');
}

// this is how you set it up
var synchronizer = new ajaxSynchronizer();
synchronizer.add(foo1);
synchronizer.add(foo2);
synchronizer.callWhenFinished(afterFunction);

There are some limitations here, but for my case it was ok. I also found that for more advanced stuff it there is also a AOP plugin (for jQuery) that might be useful: http://code.google.com/p/jquery-aop/

How do I get JSON data from RESTful service using Python?

I would give the requests library a try for this. Essentially just a much easier to use wrapper around the standard library modules (i.e. urllib2, httplib2, etc.) you would use for the same thing. For example, to fetch json data from a url that requires basic authentication would look like this:

import requests

response = requests.get('http://thedataishere.com',
                         auth=('user', 'password'))
data = response.json()

For kerberos authentication the requests project has the reqests-kerberos library which provides a kerberos authentication class that you can use with requests:

import requests
from requests_kerberos import HTTPKerberosAuth

response = requests.get('http://thedataishere.com',
                         auth=HTTPKerberosAuth())
data = response.json()

Optional Parameters in Go?

Go does not have optional parameters nor does it support method overloading:

Method dispatch is simplified if it doesn't need to do type matching as well. Experience with other languages told us that having a variety of methods with the same name but different signatures was occasionally useful but that it could also be confusing and fragile in practice. Matching only by name and requiring consistency in the types was a major simplifying decision in Go's type system.

What is a NullPointerException, and how do I fix it?

It's like you are trying to access an object which is null. Consider below example:

TypeA objA;

At this time you have just declared this object but not initialized or instantiated. And whenever you try to access any property or method in it, it will throw NullPointerException which makes sense.

See this below example as well:

String a = null;
System.out.println(a.toString()); // NullPointerException will be thrown

UIView Infinite 360 degree rotation animation?

Here is my swift solution as a UIView extension. It could be considered as a simulation of a UIActivityIndicator behaviour on any UIImageView.

import UIKit

extension UIView
{

    /**
    Starts rotating the view around Z axis.

    @param duration Duration of one full 360 degrees rotation. One second is default.
    @param repeatCount How many times the spin should be done. If not provided, the view will spin forever.
    @param clockwise Direction of the rotation. Default is clockwise (true).
     */
    func startZRotation(duration duration: CFTimeInterval = 1, repeatCount: Float = Float.infinity, clockwise: Bool = true)
    {
        if self.layer.animationForKey("transform.rotation.z") != nil {
            return
        }
        let animation = CABasicAnimation(keyPath: "transform.rotation.z")
        let direction = clockwise ? 1.0 : -1.0
        animation.toValue = NSNumber(double: M_PI * 2 * direction)
        animation.duration = duration
        animation.cumulative = true
        animation.repeatCount = repeatCount
        self.layer.addAnimation(animation, forKey:"transform.rotation.z")
    }


    /// Stop rotating the view around Z axis.
    func stopZRotation()
    {
        self.layer.removeAnimationForKey("transform.rotation.z")
    }

}

How to get a value from the last inserted row?

With PostgreSQL you can do it via the RETURNING keyword:

PostgresSQL - RETURNING

INSERT INTO mytable( field_1, field_2,... )
VALUES ( value_1, value_2 ) RETURNING anyfield

It will return the value of "anyfield". "anyfield" may be a sequence or not.

To use it with JDBC, do:

ResultSet rs = statement.executeQuery("INSERT ... RETURNING ID");
rs.next();
rs.getInt(1);

Why can't I enter a string in Scanner(System.in), when calling nextLine()-method?

import java.util.*;

public class ScannerExample {

    public static void main(String args[]) {
        int a;
        String s;
        Scanner scan = new Scanner(System.in);

        System.out.println("enter a no");
        a = scan.nextInt();
        System.out.println("no is =" + a);

        System.out.println("enter a string");
        s = scan.next();
        System.out.println("string is=" + s);
    }
}

How do I create a Java string from the contents of a file?

To read a File as binary and convert at the end

public static String readFileAsString(String filePath) throws IOException {
    DataInputStream dis = new DataInputStream(new FileInputStream(filePath));
    try {
        long len = new File(filePath).length();
        if (len > Integer.MAX_VALUE) throw new IOException("File "+filePath+" too large, was "+len+" bytes.");
        byte[] bytes = new byte[(int) len];
        dis.readFully(bytes);
        return new String(bytes, "UTF-8");
    } finally {
        dis.close();
    }
}

What is the difference between active and passive FTP?

I recently run into this question in my work place so I think I should say something more here. I will use image to explain how the FTP works as an additional source for previous answer.

Active mode:

active mode


Passive mode:

enter image description here


In an active mode configuration, the server will attempt to connect to a random client-side port. So chances are, that port wouldn't be one of those predefined ports. As a result, an attempt to connect to it will be blocked by the firewall and no connection will be established.

enter image description here


A passive configuration will not have this problem since the client will be the one initiating the connection. Of course, it's possible for the server side to have a firewall too. However, since the server is expected to receive a greater number of connection requests compared to a client, then it would be but logical for the server admin to adapt to the situation and open up a selection of ports to satisfy passive mode configurations.

So it would be best for you to configure server to support passive mode FTP. However, passive mode would make your system vulnerable to attacks because clients are supposed to connect to random server ports. Thus, to support this mode, not only should your server have to have multiple ports available, your firewall should also allow connections to all those ports to pass through!

To mitigate the risks, a good solution would be to specify a range of ports on your server and then to allow only that range of ports on your firewall.

For more information, please read the official document.

How to decode viewstate

This is somewhat "native" .NET way of converting ViewState from string into StateBag Code is below:

public static StateBag LoadViewState(string viewState)
    {
        System.Web.UI.Page converterPage = new System.Web.UI.Page();
        HiddenFieldPageStatePersister persister = new HiddenFieldPageStatePersister(new Page());
        Type utilClass = typeof(System.Web.UI.BaseParser).Assembly.GetType("System.Web.UI.Util");
        if (utilClass != null && persister != null)
        {
            MethodInfo method = utilClass.GetMethod("DeserializeWithAssert", BindingFlags.NonPublic | BindingFlags.Static);
            if (method != null)
            {
                PropertyInfo formatterProperty = persister.GetType().GetProperty("StateFormatter", BindingFlags.NonPublic | BindingFlags.Instance);
                if (formatterProperty != null)
                {
                    IStateFormatter formatter = (IStateFormatter)formatterProperty.GetValue(persister, null);
                    if (formatter != null)
                    {
                        FieldInfo pageField = formatter.GetType().GetField("_page", BindingFlags.NonPublic | BindingFlags.Instance);
                        if (pageField != null)
                        {
                            pageField.SetValue(formatter, null);
                            try
                            {
                                Pair pair = (Pair)method.Invoke(null, new object[] { formatter, viewState });
                                if (pair != null)
                                {
                                    MethodInfo loadViewState = converterPage.GetType().GetMethod("LoadViewStateRecursive", BindingFlags.Instance | BindingFlags.NonPublic);
                                    if (loadViewState != null)
                                    {
                                        FieldInfo postback = converterPage.GetType().GetField("_isCrossPagePostBack", BindingFlags.NonPublic | BindingFlags.Instance);
                                        if (postback != null)
                                        {
                                            postback.SetValue(converterPage, true);
                                        }
                                        FieldInfo namevalue = converterPage.GetType().GetField("_requestValueCollection", BindingFlags.NonPublic | BindingFlags.Instance);
                                        if (namevalue != null)
                                        {
                                            namevalue.SetValue(converterPage, new NameValueCollection());
                                        }
                                        loadViewState.Invoke(converterPage, new object[] { ((Pair)((Pair)pair.First).Second) });
                                        FieldInfo viewStateField = typeof(Control).GetField("_viewState", BindingFlags.NonPublic | BindingFlags.Instance);
                                        if (viewStateField != null)
                                        {
                                            return (StateBag)viewStateField.GetValue(converterPage);
                                        }
                                    }
                                }
                            }
                            catch (Exception ex)
                            {
                                if (ex != null)
                                {

                                }
                            }
                        }
                    }
                }
            }
        }
        return null;
    }

How can I sort generic list DESC and ASC?

I was checking all the answer above and wanted to add one more additional information. I wanted to sort the list in DESC order and I was searching for the solution which is faster for bigger inputs and I was using this method earlier :-

li.Sort();
li.Reverse();

but my test cases were failing for exceeding time limits, so below solution worked for me:-

li.Sort((a, b) => b.CompareTo(a));

So Ultimately the conclusion is that 2nd way of Sorting list in Descending order is bit faster than the previous one.

Java check if boolean is null

boolean is a primitive type, and therefore can not be null.

Its boxed type, Boolean, can be null.

The function is probably returning a Boolean as opposed to a boolean, so assigning the result to a Boolean-type variable will allow you to test for nullity.

Dynamically add item to jQuery Select2 control that uses AJAX

This provided a simple solution: Set data in Select2 after insert with AJAX

$("#select2").select2('data', {id: newID, text: newText});      

Android "hello world" pushnotification example

Overview of gcm: You send a request to google server from your android phone. You receive a registration id as a response. You will then have to send this registration id to the server from where you wish to send notifications to the mobile. Using this registration id you can then send notification to the device.

Answer:

  1. To send a notification you send the data(message) with the registration id of the device to https://android.googleapis.com/gcm/send. (use curl in php).
  2. To receive notification and registration etc, thats all you will be requiring.
  3. You will have to store the registration id on the device as well as on server. If you use GCM.jar the registration id is stored in preferences. If you wish you can save it in your local database as well.

Global Events in Angular

My favorite way to do is by using behavior subject or event emitter (almost the same) in my service to control all my subcomponent.

Using angular cli, run ng g s to create a new service then use a BehaviorSubject or EventEmitter

export Class myService {
#all the stuff that must exist

myString: string[] = [];
contactChange : BehaviorSubject<string[]> = new BehaviorSubject(this.myString);

   getContacts(newContacts) {
     // get your data from a webservices & when you done simply next the value 
    this.contactChange.next(newContacts);
   }
}

When you do that every component using your service as a provider will be aware of the change. Simply subscribe to the result like you do with eventEmitter ;)

export Class myComp {
#all the stuff that exists like @Component + constructor using (private myService: myService)

this.myService.contactChange.subscribe((contacts) => {
     this.contactList += contacts; //run everytime next is called
  }
}

Adding +1 to a variable inside a function

You could also pass points to the function: Small example:

def test(points):
    addpoint = raw_input ("type ""add"" to add a point")
    if addpoint == "add":
        points = points + 1
    else:
        print "asd"
    return points;
if __name__ == '__main__':
    points = 0
    for i in range(10):
        points = test(points)
        print points

How to download/upload files from/to SharePoint 2013 using CSOM?

A little late this comment but I will leave here my results working with the library of SharePoin Online and it is very easy to use and implement in your project, just go to the NuGet administrator of .Net and Add Microsoft.SharePoint.CSOM to your project .

https://developer.microsoft.com/en-us/office/blogs/new-sharepoint-csom-version-released-for-office-365-may-2017/

The following code snippet will help you connect your credentials to your SharePoint site, you can also read and download files from a specific site and folder.

using System;
using System.IO;
using System.Linq;
using System.Web;
using Microsoft.SharePoint.Client;
using System.Security;

using ClientOM = Microsoft.SharePoint.Client;

namespace MvcApplication.Models.Home
{
    public class SharepointModel
    {
        public ClientContext clientContext { get; set; }
        private string ServerSiteUrl = "https://somecompany.sharepoint.com/sites/ITVillahermosa";
        private string LibraryUrl = "Shared Documents/Invoices/";
        private string UserName = "[email protected]";
        private string Password = "********";
        private Web WebClient { get; set; }

        public SharepointModel()
        {
            this.Connect();
        }

        public void Connect()
        {
            try
            {
                using (clientContext = new ClientContext(ServerSiteUrl))
                {
                    var securePassword = new SecureString();
                    foreach (char c in Password)
                    {
                        securePassword.AppendChar(c);
                    }

                    clientContext.Credentials = new SharePointOnlineCredentials(UserName, securePassword);
                    WebClient = clientContext.Web;
                }
            }
            catch (Exception ex)
            {
                throw (ex);
            }
        }

        public string UploadMultiFiles(HttpRequestBase Request, HttpServerUtilityBase Server)
        {
            try
            {
                HttpPostedFileBase file = null;
                for (int f = 0; f < Request.Files.Count; f++)
                {
                    file = Request.Files[f] as HttpPostedFileBase;

                    string[] SubFolders = LibraryUrl.Split('/');
                    string filename = System.IO.Path.GetFileName(file.FileName);
                    var path = System.IO.Path.Combine(Server.MapPath("~/App_Data/uploads"), filename);
                    file.SaveAs(path);

                    clientContext.Load(WebClient, website => website.Lists, website => website.ServerRelativeUrl);
                    clientContext.ExecuteQuery();

                    //https://somecompany.sharepoint.com/sites/ITVillahermosa/Shared Documents/
                    List documentsList = clientContext.Web.Lists.GetByTitle("Documents"); //Shared Documents -> Documents
                    clientContext.Load(documentsList, i => i.RootFolder.Folders, i => i.RootFolder);
                    clientContext.ExecuteQuery();

                    string SubFolderName = SubFolders[1];//Get SubFolder 'Invoice'
                    var folderToBindTo = documentsList.RootFolder.Folders;
                    var folderToUpload = folderToBindTo.Where(i => i.Name == SubFolderName).First();

                    var fileCreationInformation = new FileCreationInformation();
                    //Assign to content byte[] i.e. documentStream
                    fileCreationInformation.Content = System.IO.File.ReadAllBytes(path);
                    //Allow owerwrite of document
                    fileCreationInformation.Overwrite = true;
                    //Upload URL
                    fileCreationInformation.Url = ServerSiteUrl + LibraryUrl + filename;

                    Microsoft.SharePoint.Client.File uploadFile = documentsList.RootFolder.Files.Add(fileCreationInformation);

                    //Update the metadata for a field having name "DocType"
                    uploadFile.ListItemAllFields["Title"] = "UploadedCSOM";

                    uploadFile.ListItemAllFields.Update();
                    clientContext.ExecuteQuery();
                }

                return "";
            }
            catch (Exception ex)
            {
                throw (ex);
            }
        }

        public string DownloadFiles()
        {
            try
            {
                string tempLocation = @"c:\Downloads\Sharepoint\";
                System.IO.DirectoryInfo di = new DirectoryInfo(tempLocation);
                foreach (FileInfo file in di.GetFiles())
                {
                    file.Delete();
                }

                FileCollection files = WebClient.GetFolderByServerRelativeUrl(this.LibraryUrl).Files;
                clientContext.Load(files);
                clientContext.ExecuteQuery();

                if (clientContext.HasPendingRequest)
                    clientContext.ExecuteQuery();

                foreach (ClientOM.File file in files)
                {
                    FileInformation fileInfo = ClientOM.File.OpenBinaryDirect(clientContext, file.ServerRelativeUrl);
                    clientContext.ExecuteQuery();

                    var filePath = tempLocation + file.Name;
                    using (var fileStream = new System.IO.FileStream(filePath, System.IO.FileMode.Create))
                    {
                        fileInfo.Stream.CopyTo(fileStream);
                    }
                }

                return "";
            }
            catch (Exception ex)
            {
                throw (ex);
            }
        }

    }
}

Then to invoke the functions from the controller in this case MVC ASP.NET is done in the following way.


using MvcApplication.Models.Home;
using System;
using System.Web.Mvc;

namespace MvcApplication.Controllers
{
    public class SharepointController : MvcBoostraBaseController
    {
        [HttpPost]
        public ActionResult Upload(FormCollection form)
        {
            try
            {
                SharepointModel sharepointModel = new SharepointModel();
                return Json(sharepointModel.UploadMultiFiles(Request, Server), JsonRequestBehavior.AllowGet);
            }
            catch (Exception ex)
            {
                return ThrowJSONError(ex);
            }
        }

        public ActionResult Download(string ServerUrl, string RelativeUrl)
        {
            try
            {
                SharepointModel sharepointModel = new SharepointModel();
                return Json(sharepointModel.DownloadFiles(), JsonRequestBehavior.AllowGet);
            }
            catch (Exception ex)
            {
                return ThrowJSONError(ex);
            }
        }
    }
}

If you need the source code of this project you can request it to [email protected]

Not an enclosing class error Android Studio

Intent myIntent = new Intent(MainActivity.this, Katra_home.class);
startActivity(myIntent);

This Should the perfect one :)

Import an Excel worksheet into Access using VBA

Pass the sheet name with the Range parameter of the DoCmd.TransferSpreadsheet Method. See the box titled "Worksheets in the Range Parameter" near the bottom of that page.

This code imports from a sheet named "temp" in a workbook named "temp.xls", and stores the data in a table named "tblFromExcel".

Dim strXls As String
strXls = CurrentProject.Path & Chr(92) & "temp.xls"
DoCmd.TransferSpreadsheet acImport, , "tblFromExcel", _
    strXls, True, "temp!"

Get the current displaying UIViewController on the screen in AppDelegate.m

Always check your build configuration if you you are running your app with debug or release.

IMPORTANT NOTE: You can't be able to test it without running your app in debug mode

This was my solution

How to determine a user's IP address in node

Had the same problem...im also new at javascript but i solved this with req.connection.remoteAddress; that gave me th IP address (but in ipv6 format ::ffff.192.168.0.101 ) and then .slice to remove the 7 first digits.

var ip = req.connection.remoteAddress;

if (ip.length < 15) 
{   
   ip = ip;
}
else
{
   var nyIP = ip.slice(7);
   ip = nyIP;
}

How does PHP 'foreach' actually work?

NOTE FOR PHP 7

To update on this answer as it has gained some popularity: This answer no longer applies as of PHP 7. As explained in the "Backward incompatible changes", in PHP 7 foreach works on copy of the array, so any changes on the array itself are not reflected on foreach loop. More details at the link.

Explanation (quote from php.net):

The first form loops over the array given by array_expression. On each iteration, the value of the current element is assigned to $value and the internal array pointer is advanced by one (so on the next iteration, you'll be looking at the next element).

So, in your first example you only have one element in the array, and when the pointer is moved the next element does not exist, so after you add new element foreach ends because it already "decided" that it it as the last element.

In your second example, you start with two elements, and foreach loop is not at the last element so it evaluates the array on the next iteration and thus realises that there is new element in the array.

I believe that this is all consequence of On each iteration part of the explanation in the documentation, which probably means that foreach does all logic before it calls the code in {}.

Test case

If you run this:

<?
    $array = Array(
        'foo' => 1,
        'bar' => 2
    );
    foreach($array as $k=>&$v) {
        $array['baz']=3;
        echo $v." ";
    }
    print_r($array);
?>

You will get this output:

1 2 3 Array
(
    [foo] => 1
    [bar] => 2
    [baz] => 3
)

Which means that it accepted the modification and went through it because it was modified "in time". But if you do this:

<?
    $array = Array(
        'foo' => 1,
        'bar' => 2
    );
    foreach($array as $k=>&$v) {
        if ($k=='bar') {
            $array['baz']=3;
        }
        echo $v." ";
    }
    print_r($array);
?>

You will get:

1 2 Array
(
    [foo] => 1
    [bar] => 2
    [baz] => 3
)

Which means that array was modified, but since we modified it when the foreach already was at the last element of the array, it "decided" not to loop anymore, and even though we added new element, we added it "too late" and it was not looped through.

Detailed explanation can be read at How does PHP 'foreach' actually work? which explains the internals behind this behaviour.

Data binding for TextBox

I Recommend you implement INotifyPropertyChanged and change your databinding code to this:

this.textBox.DataBindings.Add("Text",
                                this.Food,
                                "Name",
                                false,
                                DataSourceUpdateMode.OnPropertyChanged);

That'll fix it.

Note that the default DataSourceUpdateMode is OnValidation, so if you don't specify OnPropertyChanged, the model object won't be updated until after your validations have occurred.

Error in plot.new() : figure margins too large, Scatter plot

If you get this message in RStudio, clicking the 'broomstick' figure "Clear All Plots" in Plots tab and try plot() again.

Moreover Execute the command

graphics.off()

How to set text size in a button in html

Try this

<input type="submit" 
       value="HOME" 
       onclick="goHome()" 
       style="font-size : 20px; width: 100%; height: 100px;" /> 

Go to beginning of line without opening new line in VI

You can use ^ or 0 (Zero) in normal mode to move to the beginning of a line.

^ moves the cursor to the first non-blank character of a line
0 always moves the cursor to the "first column"

You can also use Shifti to move and switch to Insert mode.

Render partial from different folder (not shared)

In my case I was using MvcMailer (https://github.com/smsohan/MvcMailer) and wanted to access a partial view from another folder, that wasn't in "Shared." The above solutions didn't work, but using a relative path did.

@Html.Partial("../MyViewFolder/Partials/_PartialView", Model.MyObject)

Show popup after page load

try something like this

<script type="text/javascript">
function PopUp(hideOrshow) {
    if (hideOrshow == 'hide') document.getElementById('ac-wrapper').style.display = "none";
    else document.getElementById('ac-wrapper').removeAttribute('style');
}
window.onload = function () {
    setTimeout(function () {
        PopUp('show');
    }, 5000);
}
</script>

and your html

<div id="ac-wrapper" style='display:none'>
    <div id="popup">
        <center>
             <h2>Popup Content Here</h2>    
            <input type="submit" name="submit" value="Submit" onClick="PopUp('hide')" />
        </center>
    </div>
</div>

Demo JsFiddle

How to get Month Name from Calendar?

It returns English name of the month. 04 returns APRIL and so on.

String englishMonth (int month){
        return Month.of(month);
    }

Binding ComboBox SelectedItem using MVVM

I had a similar problem where the SelectedItem-binding did not update when I selected something in the combobox. My problem was that I had to set UpdateSourceTrigger=PropertyChanged for the binding.

<ComboBox ItemsSource="{Binding SalesPeriods}" 
          SelectedItem="{Binding SelectedItem, UpdateSourceTrigger=PropertyChanged}" />

Typescript - multidimensional array initialization

You only need [] to instantiate an array - this is true regardless of its type. The fact that the array is of an array type is immaterial.

The same thing applies at the first level in your loop. It is merely an array and [] is a new empty array - job done.

As for the second level, if Thing is a class then new Thing() will be just fine. Otherwise, depending on the type, you may need a factory function or other expression to create one.

class Something {
    private things: Thing[][];

    constructor() {
        this.things = [];

        for(var i: number = 0; i < 10; i++) {
            this.things[i] = [];
            for(var j: number = 0; j< 10; j++) {
                this.things[i][j] = new Thing();
            }
        }
    }
}

Setting the default page for ASP.NET (Visual Studio) server configuration

Right click on the web page you want to use as the default page and choose "Set as Start Page" whenever you run the web application from Visual Studio, it will open the selected page.

Casting to string in JavaScript

They do behave differently when the value is null.

  • null.toString() throws an error - Cannot call method 'toString' of null
  • String(null) returns - "null"
  • null + "" also returns - "null"

Very similar behaviour happens if value is undefined (see jbabey's answer).

Other than that, there is a negligible performance difference, which, unless you're using them in huge loops, isn't worth worrying about.

Date Conversion from String to sql Date in Java giving different output?

You need to use MM as mm stands for minutes.

There are two ways of producing month pattern.

SimpleDateFormat sdf1 = new SimpleDateFormat("dd-MM-yyyy"); //outputs month in numeric way, 2013-02-01

SimpleDateFormat sdf2 = new SimpleDateFormat("dd-MMM-yyyy"); // Outputs months as follows, 2013-Feb-01

Full coding snippet:

        String startDate="01-Feb-2013"; // Input String
        SimpleDateFormat sdf1 = new SimpleDateFormat("dd-MM-yyyy"); // New Pattern
        java.util.Date date = sdf1.parse(startDate); // Returns a Date format object with the pattern
        java.sql.Date sqlStartDate = new java.sql.Date(date.getTime());
        System.out.println(sqlStartDate); // Outputs : 2013-02-01

How to index into a dictionary?

You can't, since dict is unordered. you can use .popitem() to get an arbitrary item, but that will remove it from the dict.

Installing Java 7 (Oracle) in Debian via apt-get

Managed to get answer after do some google..

echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu precise main" | tee -a /etc/apt/sources.list
echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu precise main" | tee -a /etc/apt/sources.list
apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys EEA14886
apt-get update
# Java 7
apt-get install oracle-java7-installer
# For Java 8 command is:
apt-get install oracle-java8-installer

Setting background images in JFrame

Try this :

import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;


public class Test {

    public static void main(String[] args) {
        JFrame f = new JFrame();
        try {
            f.setContentPane(new JLabel(new ImageIcon(ImageIO.read(new File("test.jpg")))));
        } catch (IOException e) {
            e.printStackTrace();
        }
        f.pack();
        f.setVisible(true);
    }

}

By the way, this will result in the content pane not being a container. If you want to add things to it you have to subclass a JPanel and override the paintComponent method.

Breaking out of a for loop in Java

break; is what you need to break out of any looping statement like for, while or do-while.

In your case, its going to be like this:-

for(int x = 10; x < 20; x++) {
         // The below condition can be present before or after your sysouts, depending on your needs.
         if(x == 15){
             break; // A unlabeled break is enough. You don't need a labeled break here.
         }
         System.out.print("value of x : " + x );
         System.out.print("\n");
}

How to delete a folder with files using Java

In JDK 7 you could use Files.walkFileTree() and Files.deleteIfExists() to delete a tree of files. (Sample: http://fahdshariff.blogspot.ru/2011/08/java-7-deleting-directory-by-walking.html)

In JDK 6 one possible way is to use FileUtils.deleteQuietly from Apache Commons which will remove a file, a directory, or a directory with files and sub-directories.

How to set a timeout on a http.request() in Node?

For me - here is a less confusing way of doing the socket.setTimeout

var request=require('https').get(
    url
   ,function(response){
        var r='';
        response.on('data',function(chunk){
            r+=chunk;
            });
        response.on('end',function(){
            console.dir(r);            //end up here if everything is good!
            });
        }).on('error',function(e){
            console.dir(e.message);    //end up here if the result returns an error
            });
request.on('error',function(e){
    console.dir(e);                    //end up here if a timeout
    });
request.on('socket',function(socket){
    socket.setTimeout(1000,function(){
        request.abort();                //causes error event ?
        });
    });

Strip off URL parameter with PHP

The safest "correct" method would be:

  1. Parse the url into an array with parse_url()
  2. Extract the query portion, decompose that into an array using parse_str()
  3. Delete the query parameters you want by unset() them from the array
  4. Rebuild the original url using http_build_query()

Quick and dirty is to use a string search/replace and/or regex to kill off the value.

Passing Parameters JavaFX FXML

I realize this is a very old post and has some great answers already, but I wanted to make a simple MCVE to demonstrate one such approach and allow new coders a way to quickly see the concept in action.

In this example, we will use 5 files:

  1. Main.java - Simply used to start the application and call the first controller.
  2. Controller1.java - The controller for the first FXML layout.
  3. Controller2.java - The controller for the second FXML layout.
  4. Layout1.fxml - The FXML layout for the first scene.
  5. Layout2.fxml - The FXML layout for the second scene.

All files are listed in their entirety at the bottom of this post.

The Goal: To demonstrate passing values from Controller1 to Controller2 and vice versa.

The Program Flow:

  • The first scene contains a TextField, a Button, and a Label. When the Button is clicked, the second window is loaded and displayed, including the text entered in the TextField.
  • Within the second scene, there is also a TextField, a Button, and a Label. The Label will display the text entered in the TextField on the first scene.
  • Upon entering text in the second scene's TextField and clicking its Button, the first scene's Label is updated to show the entered text.

This is a very simple demonstration and could surely stand for some improvement, but should make the concept very clear.

The code itself is also commented with some details of what is happening and how.

THE CODE

Main.java:

import javafx.application.Application;
import javafx.stage.Stage;

public class Main extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {

        // Create the first controller, which loads Layout1.fxml within its own constructor
        Controller1 controller1 = new Controller1();

        // Show the new stage
        controller1.showStage();

    }
}

Controller1.java:

import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.stage.Stage;

import java.io.IOException;

public class Controller1 {

    // Holds this controller's Stage
    private final Stage thisStage;

    // Define the nodes from the Layout1.fxml file. This allows them to be referenced within the controller
    @FXML
    private TextField txtToSecondController;
    @FXML
    private Button btnOpenLayout2;
    @FXML
    private Label lblFromController2;

    public Controller1() {

        // Create the new stage
        thisStage = new Stage();

        // Load the FXML file
        try {
            FXMLLoader loader = new FXMLLoader(getClass().getResource("Layout1.fxml"));

            // Set this class as the controller
            loader.setController(this);

            // Load the scene
            thisStage.setScene(new Scene(loader.load()));

            // Setup the window/stage
            thisStage.setTitle("Passing Controllers Example - Layout1");

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Show the stage that was loaded in the constructor
     */
    public void showStage() {
        thisStage.showAndWait();
    }

    /**
     * The initialize() method allows you set setup your scene, adding actions, configuring nodes, etc.
     */
    @FXML
    private void initialize() {

        // Add an action for the "Open Layout2" button
        btnOpenLayout2.setOnAction(event -> openLayout2());
    }

    /**
     * Performs the action of loading and showing Layout2
     */
    private void openLayout2() {

        // Create the second controller, which loads its own FXML file. We pass a reference to this controller
        // using the keyword [this]; that allows the second controller to access the methods contained in here.
        Controller2 controller2 = new Controller2(this);

        // Show the new stage/window
        controller2.showStage();

    }

    /**
     * Returns the text entered into txtToSecondController. This allows other controllers/classes to view that data.
     */
    public String getEnteredText() {
        return txtToSecondController.getText();
    }

    /**
     * Allows other controllers to set the text of this layout's Label
     */
    public void setTextFromController2(String text) {
        lblFromController2.setText(text);
    }
}

Controller2.java:

import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.stage.Stage;

import java.io.IOException;

public class Controller2 {

    // Holds this controller's Stage
    private Stage thisStage;

    // Will hold a reference to the first controller, allowing us to access the methods found there.
    private final Controller1 controller1;

    // Add references to the controls in Layout2.fxml
    @FXML
    private Label lblFromController1;
    @FXML
    private TextField txtToFirstController;
    @FXML
    private Button btnSetLayout1Text;

    public Controller2(Controller1 controller1) {
        // We received the first controller, now let's make it usable throughout this controller.
        this.controller1 = controller1;

        // Create the new stage
        thisStage = new Stage();

        // Load the FXML file
        try {
            FXMLLoader loader = new FXMLLoader(getClass().getResource("Layout2.fxml"));

            // Set this class as the controller
            loader.setController(this);

            // Load the scene
            thisStage.setScene(new Scene(loader.load()));

            // Setup the window/stage
            thisStage.setTitle("Passing Controllers Example - Layout2");

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Show the stage that was loaded in the constructor
     */
    public void showStage() {
        thisStage.showAndWait();
    }

    @FXML
    private void initialize() {

        // Set the label to whatever the text entered on Layout1 is
        lblFromController1.setText(controller1.getEnteredText());

        // Set the action for the button
        btnSetLayout1Text.setOnAction(event -> setTextOnLayout1());
    }

    /**
     * Calls the "setTextFromController2()" method on the first controller to update its Label
     */
    private void setTextOnLayout1() {
        controller1.setTextFromController2(txtToFirstController.getText());
    }

}

Layout1.fxml:

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<AnchorPane xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1">
    <VBox alignment="CENTER" spacing="10.0">
        <padding>
            <Insets bottom="10.0" left="10.0" right="10.0" top="10.0"/>
        </padding>
        <Label style="-fx-font-weight: bold;" text="This is Layout1!"/>
        <HBox alignment="CENTER_LEFT" spacing="10.0">
            <Label text="Enter Text:"/>
            <TextField fx:id="txtToSecondController"/>
            <Button fx:id="btnOpenLayout2" mnemonicParsing="false" text="Open Layout2"/>
        </HBox>
        <VBox alignment="CENTER">
            <Label text="Text From Controller2:"/>
            <Label fx:id="lblFromController2" text="Nothing Yet!"/>
        </VBox>
    </VBox>
</AnchorPane>

Layout2.fxml:

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<AnchorPane xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1">
    <VBox alignment="CENTER" spacing="10.0">
        <padding>
            <Insets bottom="10.0" left="10.0" right="10.0" top="10.0"/>
        </padding>
        <Label style="-fx-font-weight: bold;" text="Welcome to Layout 2!"/>
        <VBox alignment="CENTER">
            <Label text="Text From Controller1:"/>
            <Label fx:id="lblFromController1" text="Nothing Yet!"/>
        </VBox>
        <HBox alignment="CENTER_LEFT" spacing="10.0">
            <Label text="Enter Text:"/>
            <TextField fx:id="txtToFirstController"/>
            <Button fx:id="btnSetLayout1Text" mnemonicParsing="false" text="Set Text on Layout1"/>
        </HBox>
    </VBox>
</AnchorPane>

How to change the text of a button in jQuery?

Changing name of the button etiquette in C#.

<button type="submit" name="add" id="btnUpdate" class="btn btn-primary" runat="server" onserverclick="btnUpdate_Click">
Add

btnUpdate.**InnerText** = "Update";

Python Remove last 3 characters of a string

>>> foo = 'BS1 1AB'
>>> foo.replace(" ", "").rstrip()[:-3].upper()
'BS1'

Map.Entry: How to use it?

Note that you can also create your own structures using a Map.Entry as the main type, using its basic implementation AbstractMap.SimpleEntry. For instance, if you wanted to have an ordered list of entries, you could write:

List<Map.Entry<String, Integer>> entries = new ArrayList<>();
entries.add(new AbstractMap.SimpleEntry<String, Integer>(myStringValue, myIntValue));

And so on. From there, you have a list of tuples. Very useful when you want ordered tuples and a basic Map is a no-go.

How can I add a class attribute to an HTML element generated by MVC's HTML Helpers?

In order to create an anonymous type (or any type) with a property that has a reserved keyword as its name in C#, you can prepend the property name with an at sign, @:

Html.BeginForm("Foo", "Bar", FormMethod.Post, new { @class = "myclass"})

For VB.NET this syntax would be accomplished using the dot, ., which in that language is default syntax for all anonymous types:

Html.BeginForm("Foo", "Bar", FormMethod.Post, new with { .class = "myclass" })

How to blur background images in Android

You can use

    Glide.with(getContext()).load(R.mipmap.bg)
            .apply(bitmapTransform(new BlurTransformation(22)))
            .into((ImageView) view.findViewById(R.id.imBg));

How to calculate combination and permutation in R?

It might be that the package "Combinations" is not updated anymore and does not work with a recent version of R (I was also unable to install it on R 2.13.1 on windows). The package "combinat" installs without problem for me and might be a solution for you depending on what exactly you're trying to do.

size of NumPy array

This is called the "shape" in NumPy, and can be requested via the .shape attribute:

>>> a = zeros((2, 5))
>>> a.shape
(2, 5)

If you prefer a function, you could also use numpy.shape(a).

Mismatched anonymous define() module

Per the docs:

If you manually code a script tag in HTML to load a script with an anonymous define() call, this error can occur.

Also seen if you manually code a script tag in HTML to load a script that has a few named modules, but then try to load an anonymous module that ends up having the same name as one of the named modules in the script loaded by the manually coded script tag.

Finally, if you use the loader plugins or anonymous modules (modules that call define() with no string ID) but do not use the RequireJS optimizer to combine files together, this error can occur. The optimizer knows how to name anonymous modules correctly so that they can be combined with other modules in an optimized file.

To avoid the error:

  • Be sure to load all scripts that call define() via the RequireJS API. Do not manually code script tags in HTML to load scripts that have define() calls in them.

  • If you manually code an HTML script tag, be sure it only includes named modules, and that an anonymous module that will have the same name as one of the modules in that file is not loaded.

  • If the problem is the use of loader plugins or anonymous modules but the RequireJS optimizer is not used for file bundling, use the RequireJS optimizer.

Convert AM/PM time to 24 hours format?

using System;

class Solution
{
    static string timeConversion(string s)
    {
        return DateTime.Parse(s).ToString("HH:mm");
    }

    static void Main(string[] args)
    {
        Console.WriteLine(timeConversion("01:00 PM"));
        Console.Read();
    }
}

Android/Eclipse: how can I add an image in the res/drawable folder?

Open folder path of Android application, open src folder then Add your image in /res/drawable folder

How to get the last five characters of a string using Substring() in C#?

Substring. This method extracts strings. It requires the location of the substring (a start index, a length). It then returns a new string with the characters in that range.

See a small example :

string input = "OneTwoThree";
// Get first three characters.
string sub = input.Substring(0, 3);
Console.WriteLine("Substring: {0}", sub);

Output : Substring: One

SQLAlchemy: how to filter date field?

In fact, your query is right except for the typo: your filter is excluding all records: you should change the <= for >= and vice versa:

qry = DBSession.query(User).filter(
        and_(User.birthday <= '1988-01-17', User.birthday >= '1985-01-17'))
# or same:
qry = DBSession.query(User).filter(User.birthday <= '1988-01-17').\
        filter(User.birthday >= '1985-01-17')

Also you can use between:

qry = DBSession.query(User).filter(User.birthday.between('1985-01-17', '1988-01-17'))

How to handle iframe in Selenium WebDriver using java

Below approach of frame handling : When no id or name is given incase of nested frame

WebElement element =driver.findElement(By.xpath(".//*[@id='block-block19']//iframe"));
driver.switchTo().frame(element);
driver.findElement(By.xpath(".//[@id='carousel']/li/div/div[3]/a")).click();

how to pass command line arguments to main method dynamically

Run ---> Debug Configuration ---> YourConfiguration ---> Arguments tab

enter image description here

T-SQL How to create tables dynamically in stored procedures?

You are using a table variable i.e. you should declare the table. This is not a temporary table.

You create a temp table like so:

CREATE TABLE #customer
(
     Name varchar(32) not null
)

You declare a table variable like so:

DECLARE @Customer TABLE
(
      Name varchar(32) not null
)

Notice that a temp table is declared using # and a table variable is declared using a @. Go read about the difference between table variables and temp tables.

UPDATE:

Based on your comment below you are actually trying to create tables in a stored procedure. For this you would need to use dynamic SQL. Basically dynamic SQL allows you to construct a SQL Statement in the form of a string and then execute it. This is the ONLY way you will be able to create a table in a stored procedure. I am going to show you how and then discuss why this is not generally a good idea.

Now for a simple example (I have not tested this code but it should give you a good indication of how to do it):

CREATE PROCEDURE sproc_BuildTable 
    @TableName NVARCHAR(128)
   ,@Column1Name NVARCHAR(32)
   ,@Column1DataType NVARCHAR(32)
   ,@Column1Nullable NVARCHAR(32)
AS

   DECLARE @SQLString NVARCHAR(MAX)
   SET @SQString = 'CREATE TABLE '+@TableName + '( '+@Column1Name+' '+@Column1DataType +' '+@Column1Nullable +') ON PRIMARY '

   EXEC (@SQLString)
   GO

This stored procedure can be executed like this:

sproc_BuildTable 'Customers','CustomerName','VARCHAR(32)','NOT NULL'

There are some major problems with this type of stored procedure.

Its going to be difficult to cater for complex tables. Imagine the following table structure:

CREATE TABLE [dbo].[Customers] (
    [CustomerID] [int] IDENTITY(1,1) NOT NULL,
    [CustomerName] [nvarchar](64) NOT NULL,
    [CustomerSUrname] [nvarchar](64) NOT NULL,
    [CustomerDateOfBirth] [datetime] NOT NULL,
    [CustomerApprovedDiscount] [decimal](3, 2) NOT NULL,
    [CustomerActive] [bit] NOT NULL,
    CONSTRAINT [PK_Customers] PRIMARY KEY CLUSTERED 
    (
        [CustomerID] ASC
    ) WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF,      ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[Customers] ADD CONSTRAINT [DF_Customers_CustomerApprovedDiscount] DEFAULT ((0.00)) FOR [CustomerApprovedDiscount]
GO 

This table is a little more complex than the first example, but not a lot. The stored procedure will be much, much more complex to deal with. So while this approach might work for small tables it is quickly going to be unmanageable.

Creating tables require planning. When you create tables they should be placed strategically on different filegroups. This is to ensure that you don't cause disk I/O contention. How will you address scalability if everything is created on the primary file group?

Could you clarify why you need tables to be created dynamically?

UPDATE 2:

Delayed update due to workload. I read your comment about needing to create a table for each shop and I think you should look at doing it like the example I am about to give you.

In this example I make the following assumptions:

  1. It's an e-commerce site that has many shops
  2. A shop can have many items (goods) to sell.
  3. A particular item (good) can be sold at many shops
  4. A shop will charge different prices for different items (goods)
  5. All prices are in $ (USD)

Let say this e-commerce site sells gaming consoles (i.e. Wii, PS3, XBOX360).

Looking at my assumptions I see a classical many-to-many relationship. A shop can sell many items (goods) and items (goods) can be sold at many shops. Let's break this down into tables.

First I would need a shop table to store all the information about the shop.

A simple shop table might look like this:

CREATE TABLE [dbo].[Shop](
    [ShopID] [int] IDENTITY(1,1) NOT NULL,
    [ShopName] [nvarchar](128) NOT NULL,
    CONSTRAINT [PK_Shop] PRIMARY KEY CLUSTERED 
    (
      [ShopID] ASC
    ) WITH (
              PAD_INDEX  = OFF
              , STATISTICS_NORECOMPUTE  = OFF
              , IGNORE_DUP_KEY = OFF
              , ALLOW_ROW_LOCKS  = ON
              , ALLOW_PAGE_LOCKS  = ON
    ) ON [PRIMARY]
    ) ON [PRIMARY]

    GO

Let's insert three shops into the database to use during our example. The following code will insert three shops:

INSERT INTO Shop
SELECT 'American Games R US'
UNION
SELECT 'Europe Gaming Experience'
UNION
SELECT 'Asian Games Emporium'

If you execute a SELECT * FROM Shop you will probably see the following:

ShopID  ShopName
1           American Games R US
2           Asian Games Emporium
3           Europe Gaming Experience

Right, so now let's move onto the Items (goods) table. Since the items/goods are products of various companies I am going to call the table product. You can execute the following code to create a simple Product table.

CREATE TABLE [dbo].[Product](
    [ProductID] [int] IDENTITY(1,1) NOT NULL,
    [ProductDescription] [nvarchar](128) NOT NULL,
 CONSTRAINT [PK_Product] PRIMARY KEY CLUSTERED 
 (
     [ProductID] ASC
 )WITH (PAD_INDEX  = OFF
        , STATISTICS_NORECOMPUTE  = OFF
        , IGNORE_DUP_KEY = OFF
        ,     ALLOW_ROW_LOCKS  = ON
         , ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
  ) ON [PRIMARY]

GO

Let's populate the products table with some products. Execute the following code to insert some products:

INSERT INTO Product
SELECT 'Wii'
UNION 
SELECT 'PS3'
UNION 
SELECT 'XBOX360'

If you execute SELECT * FROM Product you will probably see the following:

ProductID   ProductDescription
1           PS3
2           Wii
3           XBOX360

OK, at this point you have both product and shop information. So how do you bring them together? Well we know we can identify the shop by its ShopID primary key column and we know we can identify a product by its ProductID primary key column. Also, since each shop has a different price for each product we need to store the price the shop charges for the product.

So we have a table that maps the Shop to the product. We will call this table ShopProduct. A simple version of this table might look like this:

CREATE TABLE [dbo].[ShopProduct](
[ShopID] [int] NOT NULL,
[ProductID] [int] NOT NULL,
[Price] [money] NOT NULL,
CONSTRAINT [PK_ShopProduct] PRIMARY KEY CLUSTERED 
 (
     [ShopID] ASC,
      [ProductID] ASC
 )WITH (PAD_INDEX  = OFF,
     STATISTICS_NORECOMPUTE  = OFF, 
     IGNORE_DUP_KEY = OFF, 
     ALLOW_ROW_LOCKS  = ON,
     ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
  ) ON [PRIMARY]

 GO

So let's assume the American Games R Us shop only sells American consoles, the Europe Gaming Experience sells all consoles and the Asian Games Emporium sells only Asian consoles. We would need to map the primary keys from the shop and product tables into the ShopProduct table.

Here is how we are going to do the mapping. In my example the American Games R Us has a ShopID value of 1 (this is the primary key value) and I can see that the XBOX360 has a value of 3 and the shop has listed the XBOX360 for $159.99

By executing the following code you would complete the mapping:

INSERT INTO ShopProduct VALUES(1,3,159.99)

Now we want to add all product to the Europe Gaming Experience shop. In this example we know that the Europe Gaming Experience shop has a ShopID of 3 and since it sells all consoles we will need to insert the ProductID 1, 2 and 3 into the mapping table. Let's assume the prices for the consoles (products) at the Europe Gaming Experience shop are as follows: 1- The PS3 sells for $259.99 , 2- The Wii sells for $159.99 , 3- The XBOX360 sells for $199.99.

To get this mapping done you would need to execute the following code:

INSERT INTO ShopProduct VALUES(3,2,159.99) --This will insert the WII console into the mapping table for the Europe Gaming Experience Shop with a price of 159.99
INSERT INTO ShopProduct VALUES(3,1,259.99) --This will insert the PS3 console into the mapping table for the Europe Gaming Experience Shop with a price of 259.99
INSERT INTO ShopProduct VALUES(3,3,199.99) --This will insert the XBOX360 console into the mapping table for the Europe Gaming Experience Shop with a price of 199.99

At this point you have mapped two shops and their products into the mapping table. OK, so now how do I bring this all together to show a user browsing the website? Let's say you want to show all the product for the European Gaming Experience to a user on a web page – you would need to execute the following query:

SELECT      Shop.*
        , ShopProduct.*
        , Product.*
FROM         Shop 
INNER JOIN  ShopProduct ON Shop.ShopID = ShopProduct.ShopID 
INNER JOIN  Product ON ShopProduct.ProductID = Product.ProductID
WHERE       Shop.ShopID=3

You will probably see the following results:

ShopID     ShopName                 ShopID  ProductID   Price   ProductID   ProductDescription
3          Europe Gaming Experience   3         1       259.99  1           PS3
3          Europe Gaming Experience   3         2       159.99  2           Wii
3          Europe Gaming Experience   3         3       199.99  3           XBOX360

Now for one last example, let's assume that your website has a feature which finds the cheapest price for a console. A user asks to find the cheapest prices for XBOX360.

You can execute the following query:

 SELECT     Shop.*
        , ShopProduct.*
        , Product.*
 FROM         Shop 
 INNER JOIN  ShopProduct ON Shop.ShopID = ShopProduct.ShopID 
 INNER JOIN  Product ON ShopProduct.ProductID = Product.ProductID
 WHERE      Product.ProductID =3  -- You can also use Product.ProductDescription = 'XBOX360'
 ORDER BY    Price ASC

This query will return a list of all shops which sells the XBOX360 with the cheapest shop first and so on.

You will notice that I have not added the Asian Games shop. As an exercise, add the Asian games shop to the mapping table with the following products: the Asian Games Emporium sells the Wii games console for $99.99 and the PS3 console for $159.99. If you work through this example you should now understand how to model a many-to-many relationship.

I hope this helps you in your travels with database design.

.Net picking wrong referenced assembly version

In my case i had 3 projects, 1 main project and 2 sub projects referenced by main project.. So i updated the main project, leaving out sub project. That's where the conflict was. After i updated all my project everything worked just fine.

Asynchronous Process inside a javascript for loop

Any recommendation on how to fix this?

Several. You can use bind:

for (i = 0; i < j; i++) {
    asycronouseProcess(function (i) {
        alert(i);
    }.bind(null, i));
}

Or, if your browser supports let (it will be in the next ECMAScript version, however Firefox already supports it since a while) you could have:

for (i = 0; i < j; i++) {
    let k = i;
    asycronouseProcess(function() {
        alert(k);
    });
}

Or, you could do the job of bind manually (in case the browser doesn't support it, but I would say you can implement a shim in that case, it should be in the link above):

for (i = 0; i < j; i++) {
    asycronouseProcess(function(i) {
        return function () {
            alert(i)
        }
    }(i));
}

I usually prefer let when I can use it (e.g. for Firefox add-on); otherwise bind or a custom currying function (that doesn't need a context object).

The Definitive C Book Guide and List

Beginner

Introductory, no previous programming experience

  • C++ Primer * (Stanley Lippman, Josée Lajoie, and Barbara E. Moo) (updated for C++11) Coming at 1k pages, this is a very thorough introduction into C++ that covers just about everything in the language in a very accessible format and in great detail. The fifth edition (released August 16, 2012) covers C++11. [Review]

    * Not to be confused with C++ Primer Plus (Stephen Prata), with a significantly less favorable review.

  • Programming: Principles and Practice Using C++ (Bjarne Stroustrup, 2nd Edition - May 25, 2014) (updated for C++11/C++14) An introduction to programming using C++ by the creator of the language. A good read, that assumes no previous programming experience, but is not only for beginners.

Introductory, with previous programming experience

  • A Tour of C++ (Bjarne Stroustrup) (2nd edition for C++17) The “tour” is a quick (about 180 pages and 14 chapters) tutorial overview of all of standard C++ (language and standard library, and using C++11) at a moderately high level for people who already know C++ or at least are experienced programmers. This book is an extended version of the material that constitutes Chapters 2-5 of The C++ Programming Language, 4th edition.

  • Accelerated C++ (Andrew Koenig and Barbara Moo, 1st Edition - August 24, 2000) This basically covers the same ground as the C++ Primer, but does so on a fourth of its space. This is largely because it does not attempt to be an introduction to programming, but an introduction to C++ for people who've previously programmed in some other language. It has a steeper learning curve, but, for those who can cope with this, it is a very compact introduction to the language. (Historically, it broke new ground by being the first beginner's book to use a modern approach to teaching the language.) Despite this, the C++ it teaches is purely C++98. [Review]

Best practices

  • Effective C++ (Scott Meyers, 3rd Edition - May 22, 2005) This was written with the aim of being the best second book C++ programmers should read, and it succeeded. Earlier editions were aimed at programmers coming from C, the third edition changes this and targets programmers coming from languages like Java. It presents ~50 easy-to-remember rules of thumb along with their rationale in a very accessible (and enjoyable) style. For C++11 and C++14 the examples and a few issues are outdated and Effective Modern C++ should be preferred. [Review]

  • Effective Modern C++ (Scott Meyers) This is basically the new version of Effective C++, aimed at C++ programmers making the transition from C++03 to C++11 and C++14.

  • Effective STL (Scott Meyers) This aims to do the same to the part of the standard library coming from the STL what Effective C++ did to the language as a whole: It presents rules of thumb along with their rationale. [Review]


Intermediate

  • More Effective C++ (Scott Meyers) Even more rules of thumb than Effective C++. Not as important as the ones in the first book, but still good to know.

  • Exceptional C++ (Herb Sutter) Presented as a set of puzzles, this has one of the best and thorough discussions of the proper resource management and exception safety in C++ through Resource Acquisition is Initialization (RAII) in addition to in-depth coverage of a variety of other topics including the pimpl idiom, name lookup, good class design, and the C++ memory model. [Review]

  • More Exceptional C++ (Herb Sutter) Covers additional exception safety topics not covered in Exceptional C++, in addition to discussion of effective object-oriented programming in C++ and correct use of the STL. [Review]

  • Exceptional C++ Style (Herb Sutter) Discusses generic programming, optimization, and resource management; this book also has an excellent exposition of how to write modular code in C++ by using non-member functions and the single responsibility principle. [Review]

  • C++ Coding Standards (Herb Sutter and Andrei Alexandrescu) “Coding standards” here doesn't mean “how many spaces should I indent my code?” This book contains 101 best practices, idioms, and common pitfalls that can help you to write correct, understandable, and efficient C++ code. [Review]

  • C++ Templates: The Complete Guide (David Vandevoorde and Nicolai M. Josuttis) This is the book about templates as they existed before C++11. It covers everything from the very basics to some of the most advanced template metaprogramming and explains every detail of how templates work (both conceptually and at how they are implemented) and discusses many common pitfalls. Has excellent summaries of the One Definition Rule (ODR) and overload resolution in the appendices. A second edition covering C++11, C++14 and C++17 has been already published. [Review]

  • C++ 17 - The Complete Guide (Nicolai M. Josuttis) This book describes all the new features introduced in the C++17 Standard covering everything from the simple ones like 'Inline Variables', 'constexpr if' all the way up to 'Polymorphic Memory Resources' and 'New and Delete with overaligned Data'. [Review]

  • C++ in Action (Bartosz Milewski). This book explains C++ and its features by building an application from ground up. [Review]

  • Functional Programming in C++ (Ivan Cukic). This book introduces functional programming techniques to modern C++ (C++11 and later). A very nice read for those who want to apply functional programming paradigms to C++.

  • Professional C++ (Marc Gregoire, 5th Edition - Feb 2021) Provides a comprehensive and detailed tour of the C++ language implementation replete with professional tips and concise but informative in-text examples, emphasizing C++20 features. Uses C++20 features, such as modules and std::format throughout all examples.


Advanced

  • Modern C++ Design (Andrei Alexandrescu) A groundbreaking book on advanced generic programming techniques. Introduces policy-based design, type lists, and fundamental generic programming idioms then explains how many useful design patterns (including small object allocators, functors, factories, visitors, and multi-methods) can be implemented efficiently, modularly, and cleanly using generic programming. [Review]

  • C++ Template Metaprogramming (David Abrahams and Aleksey Gurtovoy)

  • C++ Concurrency In Action (Anthony Williams) A book covering C++11 concurrency support including the thread library, the atomics library, the C++ memory model, locks and mutexes, as well as issues of designing and debugging multithreaded applications. A second edition covering C++14 and C++17 has been already published. [Review]

  • Advanced C++ Metaprogramming (Davide Di Gennaro) A pre-C++11 manual of TMP techniques, focused more on practice than theory. There are a ton of snippets in this book, some of which are made obsolete by type traits, but the techniques, are nonetheless useful to know. If you can put up with the quirky formatting/editing, it is easier to read than Alexandrescu, and arguably, more rewarding. For more experienced developers, there is a good chance that you may pick up something about a dark corner of C++ (a quirk) that usually only comes about through extensive experience.


Reference Style - All Levels

  • The C++ Programming Language (Bjarne Stroustrup) (updated for C++11) The classic introduction to C++ by its creator. Written to parallel the classic K&R, this indeed reads very much like it and covers just about everything from the core language to the standard library, to programming paradigms to the language's philosophy. [Review] Note: All releases of the C++ standard are tracked in the question "Where do I find the current C or C++ standard documents?".

  • C++ Standard Library Tutorial and Reference (Nicolai Josuttis) (updated for C++11) The introduction and reference for the C++ Standard Library. The second edition (released on April 9, 2012) covers C++11. [Review]

  • The C++ IO Streams and Locales (Angelika Langer and Klaus Kreft) There's very little to say about this book except that, if you want to know anything about streams and locales, then this is the one place to find definitive answers. [Review]

C++11/14/17/… References:

  • The C++11/14/17 Standard (INCITS/ISO/IEC 14882:2011/2014/2017) This, of course, is the final arbiter of all that is or isn't C++. Be aware, however, that it is intended purely as a reference for experienced users willing to devote considerable time and effort to its understanding. The C++17 standard is released in electronic form for 198 Swiss Francs.

  • The C++17 standard is available, but seemingly not in an economical form – directly from the ISO it costs 198 Swiss Francs (about $200 US). For most people, the final draft before standardization is more than adequate (and free). Many will prefer an even newer draft, documenting new features that are likely to be included in C++20.

  • Overview of the New C++ (C++11/14) (PDF only) (Scott Meyers) (updated for C++14) These are the presentation materials (slides and some lecture notes) of a three-day training course offered by Scott Meyers, who's a highly respected author on C++. Even though the list of items is short, the quality is high.

  • The C++ Core Guidelines (C++11/14/17/…) (edited by Bjarne Stroustrup and Herb Sutter) is an evolving online document consisting of a set of guidelines for using modern C++ well. The guidelines are focused on relatively higher-level issues, such as interfaces, resource management, memory management and concurrency affecting application architecture and library design. The project was announced at CppCon'15 by Bjarne Stroustrup and others and welcomes contributions from the community. Most guidelines are supplemented with a rationale and examples as well as discussions of possible tool support. Many rules are designed specifically to be automatically checkable by static analysis tools.

  • The C++ Super-FAQ (Marshall Cline, Bjarne Stroustrup and others) is an effort by the Standard C++ Foundation to unify the C++ FAQs previously maintained individually by Marshall Cline and Bjarne Stroustrup and also incorporating new contributions. The items mostly address issues at an intermediate level and are often written with a humorous tone. Not all items might be fully up to date with the latest edition of the C++ standard yet.

  • cppreference.com (C++03/11/14/17/…) (initiated by Nate Kohl) is a wiki that summarizes the basic core-language features and has extensive documentation of the C++ standard library. The documentation is very precise but is easier to read than the official standard document and provides better navigation due to its wiki nature. The project documents all versions of the C++ standard and the site allows filtering the display for a specific version. The project was presented by Nate Kohl at CppCon'14.


Classics / Older

Note: Some information contained within these books may not be up-to-date or no longer considered best practice.

  • The Design and Evolution of C++ (Bjarne Stroustrup) If you want to know why the language is the way it is, this book is where you find answers. This covers everything before the standardization of C++.

  • Ruminations on C++ - (Andrew Koenig and Barbara Moo) [Review]

  • Advanced C++ Programming Styles and Idioms (James Coplien) A predecessor of the pattern movement, it describes many C++-specific “idioms”. It's certainly a very good book and might still be worth a read if you can spare the time, but quite old and not up-to-date with current C++.

  • Large Scale C++ Software Design (John Lakos) Lakos explains techniques to manage very big C++ software projects. Certainly, a good read, if it only was up to date. It was written long before C++ 98 and misses on many features (e.g. namespaces) important for large-scale projects. If you need to work in a big C++ software project, you might want to read it, although you need to take more than a grain of salt with it. The first volume of a new edition is released in 2019.

  • Inside the C++ Object Model (Stanley Lippman) If you want to know how virtual member functions are commonly implemented and how base objects are commonly laid out in memory in a multi-inheritance scenario, and how all this affects performance, this is where you will find thorough discussions of such topics.

  • The Annotated C++ Reference Manual (Bjarne Stroustrup, Margaret A. Ellis) This book is quite outdated in the fact that it explores the 1989 C++ 2.0 version - Templates, exceptions, namespaces and new casts were not yet introduced. Saying that however, this book goes through the entire C++ standard of the time explaining the rationale, the possible implementations, and features of the language. This is not a book to learn programming principles and patterns on C++, but to understand every aspect of the C++ language.

  • Thinking in C++ (Bruce Eckel, 2nd Edition, 2000). Two volumes; is a tutorial style free set of intro level books. Downloads: vol 1, vol 2. Unfortunately they're marred by a number of trivial errors (e.g. maintaining that temporaries are automatically const), with no official errata list. A partial 3rd party errata list is available at http://www.computersciencelab.com/Eckel.htm, but it is apparently not maintained.

  • Scientific and Engineering C++: An Introduction to Advanced Techniques and Examples (John Barton and Lee Nackman) It is a comprehensive and very detailed book that tried to explain and make use of all the features available in C++, in the context of numerical methods. It introduced at the time several new techniques, such as the Curiously Recurring Template Pattern (CRTP, also called Barton-Nackman trick). It pioneered several techniques such as dimensional analysis and automatic differentiation. It came with a lot of compilable and useful code, ranging from an expression parser to a Lapack wrapper. The code is still available online. Unfortunately, the books have become somewhat outdated in the style and C++ features, however, it was an incredible tour-de-force at the time (1994, pre-STL). The chapters on dynamics inheritance are a bit complicated to understand and not very useful. An updated version of this classic book that includes move semantics and the lessons learned from the STL would be very nice.

Spring Boot java.lang.NoClassDefFoundError: javax/servlet/Filter

For Jar

Add pom.xml

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

When should I use a struct rather than a class in C#?

The source referenced by the OP has some credibility ...but what about Microsoft - what is the stance on struct usage? I sought some extra learning from Microsoft, and here is what I found:

Consider defining a structure instead of a class if instances of the type are small and commonly short-lived or are commonly embedded in other objects.

Do not define a structure unless the type has all of the following characteristics:

  1. It logically represents a single value, similar to primitive types (integer, double, and so on).
  2. It has an instance size smaller than 16 bytes.
  3. It is immutable.
  4. It will not have to be boxed frequently.

Microsoft consistently violates those rules

Okay, #2 and #3 anyway. Our beloved dictionary has 2 internal structs:

[StructLayout(LayoutKind.Sequential)]  // default for structs
private struct Entry  //<Tkey, TValue>
{
    //  View code at *Reference Source
}

[Serializable, StructLayout(LayoutKind.Sequential)]
public struct Enumerator : 
    IEnumerator<KeyValuePair<TKey, TValue>>, IDisposable, 
    IDictionaryEnumerator, IEnumerator
{
    //  View code at *Reference Source
}

*Reference Source

The 'JonnyCantCode.com' source got 3 out of 4 - quite forgivable since #4 probably wouldn't be an issue. If you find yourself boxing a struct, rethink your architecture.

Let's look at why Microsoft would use these structs:

  1. Each struct, Entry and Enumerator, represent single values.
  2. Speed
  3. Entry is never passed as a parameter outside of the Dictionary class. Further investigation shows that in order to satisfy implementation of IEnumerable, Dictionary uses the Enumerator struct which it copies every time an enumerator is requested ...makes sense.
  4. Internal to the Dictionary class. Enumerator is public because Dictionary is enumerable and must have equal accessibility to the IEnumerator interface implementation - e.g. IEnumerator getter.

Update - In addition, realize that when a struct implements an interface - as Enumerator does - and is cast to that implemented type, the struct becomes a reference type and is moved to the heap. Internal to the Dictionary class, Enumerator is still a value type. However, as soon as a method calls GetEnumerator(), a reference-type IEnumerator is returned.

What we don't see here is any attempt or proof of requirement to keep structs immutable or maintaining an instance size of only 16 bytes or less:

  1. Nothing in the structs above is declared readonly - not immutable
  2. Size of these struct could be well over 16 bytes
  3. Entry has an undetermined lifetime (from Add(), to Remove(), Clear(), or garbage collection);

And ... 4. Both structs store TKey and TValue, which we all know are quite capable of being reference types (added bonus info)

Hashed keys notwithstanding, dictionaries are fast in part because instancing a struct is quicker than a reference type. Here, I have a Dictionary<int, int> that stores 300,000 random integers with sequentially incremented keys.

Capacity: 312874
MemSize: 2660827 bytes
Completed Resize: 5ms
Total time to fill: 889ms

Capacity: number of elements available before the internal array must be resized.

MemSize: determined by serializing the dictionary into a MemoryStream and getting a byte length (accurate enough for our purposes).

Completed Resize: the time it takes to resize the internal array from 150862 elements to 312874 elements. When you figure that each element is sequentially copied via Array.CopyTo(), that ain't too shabby.

Total time to fill: admittedly skewed due to logging and an OnResize event I added to the source; however, still impressive to fill 300k integers while resizing 15 times during the operation. Just out of curiosity, what would the total time to fill be if I already knew the capacity? 13ms

So, now, what if Entry were a class? Would these times or metrics really differ that much?

Capacity: 312874
MemSize: 2660827 bytes
Completed Resize: 26ms
Total time to fill: 964ms

Obviously, the big difference is in resizing. Any difference if Dictionary is initialized with the Capacity? Not enough to be concerned with ... 12ms.

What happens is, because Entry is a struct, it does not require initialization like a reference type. This is both the beauty and the bane of the value type. In order to use Entry as a reference type, I had to insert the following code:

/*
 *  Added to satisfy initialization of entry elements --
 *  this is where the extra time is spent resizing the Entry array
 * **/
for (int i = 0 ; i < prime ; i++)
{
    destinationArray[i] = new Entry( );
}
/*  *********************************************** */  

The reason I had to initialize each array element of Entry as a reference type can be found at MSDN: Structure Design. In short:

Do not provide a default constructor for a structure.

If a structure defines a default constructor, when arrays of the structure are created, the common language runtime automatically executes the default constructor on each array element.

Some compilers, such as the C# compiler, do not allow structures to have default constructors.

It is actually quite simple and we will borrow from Asimov's Three Laws of Robotics:

  1. The struct must be safe to use
  2. The struct must perform its function efficiently, unless this would violate rule #1
  3. The struct must remain intact during its use unless its destruction is required to satisfy rule #1

...what do we take away from this: in short, be responsible with the use of value types. They are quick and efficient, but have the ability to cause many unexpected behaviors if not properly maintained (i.e. unintentional copies).

TNS Protocol adapter error while starting Oracle SQL*Plus

Ensure the OracleService is running. I keep running into this error, but when I go into Services, find OracleServiceXE and manually start it, the problem is resolved. I have it set to start automatically, but sometimes it just seems to stop on its own; at least, I can't find anything I am doing to stop it.

Iterator invalidation rules

Since this question draws so many votes and kind of becomes an FAQ, I guess it would be better to write a separate answer to mention one significant difference between C++03 and C++11 regarding the impact of std::vector's insertion operation on the validity of iterators and references with respect to reserve() and capacity(), which the most upvoted answer failed to notice.

C++ 03:

Reallocation invalidates all the references, pointers, and iterators referring to the elements in the sequence. It is guaranteed that no reallocation takes place during insertions that happen after a call to reserve() until the time when an insertion would make the size of the vector greater than the size specified in the most recent call to reserve().

C++11:

Reallocation invalidates all the references, pointers, and iterators referring to the elements in the sequence. It is guaranteed that no reallocation takes place during insertions that happen after a call to reserve() until the time when an insertion would make the size of the vector greater than the value of capacity().

So in C++03, it is not "unless the new container size is greater than the previous capacity (in which case all iterators and references are invalidated)" as mentioned in the other answer, instead, it should be "greater than the size specified in the most recent call to reserve()". This is one thing that C++03 differs from C++11. In C++03, once an insert() causes the size of the vector to reach the value specified in the previous reserve() call (which could well be smaller than the current capacity() since a reserve() could result a bigger capacity() than asked for), any subsequent insert() could cause reallocation and invalidate all the iterators and references. In C++11, this won't happen and you can always trust capacity() to know with certainty that the next reallocation won't take place before the size overpasses capacity().

In conclusion, if you are working with a C++03 vector and you want to make sure a reallocation won't happen when you perform insertion, it's the value of the argument you previously passed to reserve() that you should check the size against, not the return value of a call to capacity(), otherwise you may get yourself surprised at a "premature" reallocation.

How to solve error: "Clock skew detected"?

One of the reason may be improper date/time of your PC.

In Ubuntu PC to check the date and time using:

date

Example, One of the ways to update date and time is:

date -s "23 MAR 2017 17:06:00"

git ignore vim temporary files

I found this will have git ignore temporary files created by vim:

[._]*.s[a-w][a-z]
[._]s[a-w][a-z]
*.un~
Session.vim
.netrwhist
*~

It can also be viewed here.

Automatically enter SSH password with script

sshpass with better security

I stumbled on this thread while looking for a way to ssh into a bogged-down server -- it took over a minute to process the SSH connection attempt, and timed out before I could enter a password. In this case, I wanted to be able to supply my password immediately when the prompt was available.

(And if it's not painfully clear: with a server in this state, it's far too late to set up a public key login.)

sshpass to the rescue. However, there are better ways to go about this than sshpass -p.

My implementation skips directly to the interactive password prompt (no time wasted seeing if public key exchange can happen), and never reveals the password as plain text.

#!/bin/sh
# preempt-ssh.sh
# usage: same arguments that you'd pass to ssh normally
echo "You're going to run (with our additions) ssh $@"

# Read password interactively and save it to the environment
read -s -p "Password to use: " SSHPASS 
export SSHPASS

# have sshpass load the password from the environment, and skip public key auth
# all other args come directly from the input
sshpass -e ssh -o PreferredAuthentications=keyboard-interactive -o PubkeyAuthentication=no "$@"

# clear the exported variable containing the password
unset SSHPASS

Python: avoid new line with print command

Utilize a trailing comma to prevent a new line from being presented:

print "this should be"; print "on the same line"

Should be:

print "this should be", "on the same line"

In addition, you can just attach the variable being passed to the end of the desired string by:

print "Nope, that is not a two. That is a", x

You can also use:

print "Nope, that is not a two. That is a %d" % x #assuming x is always an int

You can access additional documentation regarding string formatting utilizing the % operator (modulo).

Simple http post example in Objective-C?

Thanks a lot it worked , please note I did a typo in php as it should be mysqli_query( $con2, $sql )

How to extract code of .apk file which is not working?

step 1:

enter image description hereDownload dex2jar here. Create a java project and paste (dex2jar-0.0.7.11-SNAPSHOT/lib ) jar files .

Copy apk file into java project

Run it and after refresh the project ,you get jar file .Using java decompiler you can view all java class files

step 2: Download java decompiler here

How to stretch children to fill cross-axis?

  • The children of a row-flexbox container automatically fill the container's vertical space.

  • Specify flex: 1; for a child if you want it to fill the remaining horizontal space:

_x000D_
_x000D_
.wrapper {_x000D_
  display: flex;_x000D_
  flex-direction: row;_x000D_
  align-items: stretch;_x000D_
  width: 100%;_x000D_
  height: 5em;_x000D_
  background: #ccc;_x000D_
}_x000D_
.wrapper > .left_x000D_
{_x000D_
  background: #fcc;_x000D_
}_x000D_
.wrapper > .right_x000D_
{_x000D_
  background: #ccf;_x000D_
  flex: 1; _x000D_
}
_x000D_
<div class="wrapper">_x000D_
  <div class="left">Left</div>_x000D_
  <div class="right">Right</div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

  • Specify flex: 1; for both children if you want them to fill equal amounts of the horizontal space:

_x000D_
_x000D_
.wrapper {_x000D_
  display: flex;_x000D_
  flex-direction: row;_x000D_
  align-items: stretch;_x000D_
  width: 100%;_x000D_
  height: 5em;_x000D_
  background: #ccc;_x000D_
}_x000D_
.wrapper > div _x000D_
{_x000D_
  flex: 1; _x000D_
}_x000D_
.wrapper > .left_x000D_
{_x000D_
  background: #fcc;_x000D_
}_x000D_
.wrapper > .right_x000D_
{_x000D_
  background: #ccf;_x000D_
}
_x000D_
<div class="wrapper">_x000D_
  <div class="left">Left</div>_x000D_
  <div class="right">Right</div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

PostgreSQL Exception Handling

To catch the error message and its code:

do $$       
begin

    create table yyy(a int);
    create table yyy(a int); -- this will cause an error

exception when others then 

    raise notice 'The transaction is in an uncommittable state. '
                 'Transaction was rolled back';

    raise notice '% %', SQLERRM, SQLSTATE;

end; $$ 
language 'plpgsql';

Haven't found the line number yet

UPDATE April, 16, 2019

As suggested by Diego Scaravaggi, for Postgres 9.2 and up, use GET STACKED DIAGNOSTICS:

do language plpgsql $$
declare
    v_state   TEXT;
    v_msg     TEXT;
    v_detail  TEXT;
    v_hint    TEXT;
    v_context TEXT;
begin

    create table yyy(a int);
    create table yyy(a int); -- this will cause an error

exception when others then 

    get stacked diagnostics
        v_state   = returned_sqlstate,
        v_msg     = message_text,
        v_detail  = pg_exception_detail,
        v_hint    = pg_exception_hint,
        v_context = pg_exception_context;

    raise notice E'Got exception:
        state  : %
        message: %
        detail : %
        hint   : %
        context: %', v_state, v_msg, v_detail, v_hint, v_context;

    raise notice E'Got exception:
        SQLSTATE: % 
        SQLERRM: %', SQLSTATE, SQLERRM;     

    raise notice '%', message_text; -- invalid. message_text is contextual to GET STACKED DIAGNOSTICS only

end; $$;

Result:

NOTICE:  Got exception:
        state  : 42P07
        message: relation "yyy" already exists
        detail : 
        hint   : 
        context: SQL statement "create table yyy(a int)"
PL/pgSQL function inline_code_block line 11 at SQL statement
NOTICE:  Got exception:
        SQLSTATE: 42P07 
        SQLERRM: relation "yyy" already exists

ERROR:  column "message_text" does not exist
LINE 1: SELECT message_text
               ^
QUERY:  SELECT message_text
CONTEXT:  PL/pgSQL function inline_code_block line 33 at RAISE
SQL state: 42703

Aside from GET STACKED DIAGNOSTICS is SQL standard-compliant, its diagnostics variables (e.g., message_text) are contextual to GSD only. So if you have a field named message_text in your table, there's no chance that GSD can interfere with your field's value.

Still no line number though.

Test if element is present using Selenium WebDriver?

You can make the code run faster by shorting the selenium timeout before your try catch statement.

I use the following code to check if an element is present.

protected boolean isElementPresent(By selector) {
    selenium.manage().timeouts().implicitlyWait(1, TimeUnit.SECONDS);
    logger.debug("Is element present"+selector);
    boolean returnVal = true;
    try{
        selenium.findElement(selector);
    } catch (NoSuchElementException e){
        returnVal = false;
    } finally {
        selenium.manage().timeouts().implicitlyWait(15, TimeUnit.SECONDS);
    }
    return returnVal;
}

Hiding table data using <div style="display:none">

Give all the rows you want to hide a class name that you can use for hiding. Use javascript to add/remove this class from the different rows.

<table>
<tr><th>Test Table</th><tr>
<tr class="toHide"><td>123456789</td><tr>
<tr class="toHide"><td>123456789</td><tr>
<tr class="toHide"><td>123456789</td><tr>
</table>

CSS:

.toHide
{
 display: none;
}

Cannot install packages using node package manager in Ubuntu

Try linking node to nodejs. First find out where nodejs is

whereis nodejs

Then soft link node to nodejs

ln -s [the path of nodejs] /usr/bin/node 

I am assuming /usr/bin is in your execution path. Then you can test by typing node or npm into your command line, and everything should work now.

How can I pad an integer with zeros on the left?

Check my code that will work for integer and String.

Assume our first number is 2. And we want to add zeros to that so the the length of final string will be 4. For that you can use following code

    int number=2;
    int requiredLengthAfterPadding=4;
    String resultString=Integer.toString(number);
    int inputStringLengh=resultString.length();
    int diff=requiredLengthAfterPadding-inputStringLengh;
    if(inputStringLengh<requiredLengthAfterPadding)
    {
        resultString=new String(new char[diff]).replace("\0", "0")+number;
    }        
    System.out.println(resultString);

C# DateTime.ParseExact

That's because you have the Date in American format in line[i] and UK format in the FormatString.

11/20/2011
M / d/yyyy

I'm guessing you might need to change the FormatString to:

"M/d/yyyy h:mm"

How to prevent column break within an element?

The correct way to do this is with the break-inside CSS property:

.x li {
    break-inside: avoid-column;
}

Unfortunately, as of October 2019, this is not supported in Firefox but it is supported by every other major browser. With Chrome, I was able to use the above code, but I couldn't make anything work for Firefox (See Bug 549114).

The workaround you can do for Firefox if necessary is to wrap your non-breaking content in a table but that is a really, really terrible solution if you can avoid it.

UPDATE

According to the bug report mentioned above, Firefox 20+ supports page-break-inside: avoid as a mechanism for avoiding column breaks inside an element but the below code snippet demonstrates it still not working with lists:

_x000D_
_x000D_
.x {_x000D_
    column-count: 3;_x000D_
    width: 30em;_x000D_
}_x000D_
_x000D_
.x ul {_x000D_
    margin: 0;_x000D_
}_x000D_
_x000D_
.x li {_x000D_
    -webkit-column-break-inside: avoid;_x000D_
    -moz-column-break-inside:avoid;_x000D_
    -moz-page-break-inside:avoid;_x000D_
    page-break-inside: avoid;_x000D_
    break-inside: avoid-column;_x000D_
}
_x000D_
<div class='x'>_x000D_
    <ul>_x000D_
        <li>Number one, one, one, one, one</li>_x000D_
        <li>Number two, two, two, two, two, two, two, two, two, two, two, two</li>_x000D_
        <li>Number three</li>_x000D_
    </ul>_x000D_
</div>
_x000D_
_x000D_
_x000D_

As others mention, you can do overflow: hidden or display: inline-block but this removes the bullets shown in the original question. Your solution will vary based on what your goals are.

UPDATE 2 Since Firefox does prevent breaking on display:table and display:inline-block a reliable but non-semantic solution would be to wrap each list item in its own list and apply the style rule there:

_x000D_
_x000D_
.x {_x000D_
    -moz-column-count: 3;_x000D_
    -webkit-column-count: 3;_x000D_
    column-count: 3;_x000D_
    width: 30em;_x000D_
}_x000D_
_x000D_
.x ul {_x000D_
    margin: 0;_x000D_
    -webkit-column-break-inside: avoid; /* Chrome, Safari */_x000D_
    page-break-inside: avoid;           /* Theoretically FF 20+ */_x000D_
    break-inside: avoid-column;         /* IE 11 */_x000D_
    display:table;                      /* Actually FF 20+ */_x000D_
}
_x000D_
<div class='x'>_x000D_
    <ul>_x000D_
        <li>Number one, one, one, one, one</li>_x000D_
    </ul>_x000D_
    <ul>_x000D_
        <li>Number two, two, two, two, two, two, two, two, two, two, two, two</li>_x000D_
    </ul>_x000D_
    <ul>_x000D_
        <li>Number three</li>_x000D_
    </ul>_x000D_
</div>
_x000D_
_x000D_
_x000D_

Difference between Dictionary and Hashtable

Simply, Dictionary<TKey,TValue> is a generic type, allowing:

  • static typing (and compile-time verification)
  • use without boxing

If you are .NET 2.0 or above, you should prefer Dictionary<TKey,TValue> (and the other generic collections)

A subtle but important difference is that Hashtable supports multiple reader threads with a single writer thread, while Dictionary offers no thread safety. If you need thread safety with a generic dictionary, you must implement your own synchronization or (in .NET 4.0) use ConcurrentDictionary<TKey, TValue>.

Using Java with Nvidia GPUs (CUDA)

First of all, you should be aware of the fact that CUDA will not automagically make computations faster. On the one hand, because GPU programming is an art, and it can be very, very challenging to get it right. On the other hand, because GPUs are well-suited only for certain kinds of computations.

This may sound confusing, because you can basically compute anything on the GPU. The key point is, of course, whether you will achieve a good speedup or not. The most important classification here is whether a problem is task parallel or data parallel. The first one refers, roughly speaking, to problems where several threads are working on their own tasks, more or less independently. The second one refers to problems where many threads are all doing the same - but on different parts of the data.

The latter is the kind of problem that GPUs are good at: They have many cores, and all the cores do the same, but operate on different parts of the input data.

You mentioned that you have "simple math but with huge amount of data". Although this may sound like a perfectly data-parallel problem and thus like it was well-suited for a GPU, there is another aspect to consider: GPUs are ridiculously fast in terms of theoretical computational power (FLOPS, Floating Point Operations Per Second). But they are often throttled down by the memory bandwidth.

This leads to another classification of problems. Namely whether problems are memory bound or compute bound.

The first one refers to problems where the number of instructions that are done for each data element is low. For example, consider a parallel vector addition: You'll have to read two data elements, then perform a single addition, and then write the sum into the result vector. You will not see a speedup when doing this on the GPU, because the single addition does not compensate for the efforts of reading/writing the memory.

The second term, "compute bound", refers to problems where the number of instructions is high compared to the number of memory reads/writes. For example, consider a matrix multiplication: The number of instructions will be O(n^3) when n is the size of the matrix. In this case, one can expect that the GPU will outperform a CPU at a certain matrix size. Another example could be when many complex trigonometric computations (sine/cosine etc) are performed on "few" data elements.

As a rule of thumb: You can assume that reading/writing one data element from the "main" GPU memory has a latency of about 500 instructions....

Therefore, another key point for the performance of GPUs is data locality: If you have to read or write data (and in most cases, you will have to ;-)), then you should make sure that the data is kept as close as possible to the GPU cores. GPUs thus have certain memory areas (referred to as "local memory" or "shared memory") that usually is only a few KB in size, but particularly efficient for data that is about to be involved in a computation.

So to emphasize this again: GPU programming is an art, that is only remotely related to parallel programming on the CPU. Things like Threads in Java, with all the concurrency infrastructure like ThreadPoolExecutors, ForkJoinPools etc. might give the impression that you just have to split your work somehow and distribute it among several processors. On the GPU, you may encounter challenges on a much lower level: Occupancy, register pressure, shared memory pressure, memory coalescing ... just to name a few.

However, when you have a data-parallel, compute-bound problem to solve, the GPU is the way to go.


A general remark: Your specifically asked for CUDA. But I'd strongly recommend you to also have a look at OpenCL. It has several advantages. First of all, it's an vendor-independent, open industry standard, and there are implementations of OpenCL by AMD, Apple, Intel and NVIDIA. Additionally, there is a much broader support for OpenCL in the Java world. The only case where I'd rather settle for CUDA is when you want to use the CUDA runtime libraries, like CUFFT for FFT or CUBLAS for BLAS (Matrix/Vector operations). Although there are approaches for providing similar libraries for OpenCL, they can not directly be used from Java side, unless you create your own JNI bindings for these libraries.


You might also find it interesting to hear that in October 2012, the OpenJDK HotSpot group started the project "Sumatra": http://openjdk.java.net/projects/sumatra/ . The goal of this project is to provide GPU support directly in the JVM, with support from the JIT. The current status and first results can be seen in their mailing list at http://mail.openjdk.java.net/mailman/listinfo/sumatra-dev


However, a while ago, I collected some resources related to "Java on the GPU" in general. I'll summarize these again here, in no particular order.

(Disclaimer: I'm the author of http://jcuda.org/ and http://jocl.org/ )

(Byte)code translation and OpenCL code generation:

https://github.com/aparapi/aparapi : An open-source library that is created and actively maintained by AMD. In a special "Kernel" class, one can override a specific method which should be executed in parallel. The byte code of this method is loaded at runtime using an own bytecode reader. The code is translated into OpenCL code, which is then compiled using the OpenCL compiler. The result can then be executed on the OpenCL device, which may be a GPU or a CPU. If the compilation into OpenCL is not possible (or no OpenCL is available), the code will still be executed in parallel, using a Thread Pool.

https://github.com/pcpratts/rootbeer1 : An open-source library for converting parts of Java into CUDA programs. It offers dedicated interfaces that may be implemented to indicate that a certain class should be executed on the GPU. In contrast to Aparapi, it tries to automatically serialize the "relevant" data (that is, the complete relevant part of the object graph!) into a representation that is suitable for the GPU.

https://code.google.com/archive/p/java-gpu/ : A library for translating annotated Java code (with some limitations) into CUDA code, which is then compiled into a library that executes the code on the GPU. The Library was developed in the context of a PhD thesis, which contains profound background information about the translation process.

https://github.com/ochafik/ScalaCL : Scala bindings for OpenCL. Allows special Scala collections to be processed in parallel with OpenCL. The functions that are called on the elements of the collections can be usual Scala functions (with some limitations) which are then translated into OpenCL kernels.

Language extensions

http://www.ateji.com/px/index.html : A language extension for Java that allows parallel constructs (e.g. parallel for loops, OpenMP style) which are then executed on the GPU with OpenCL. Unfortunately, this very promising project is no longer maintained.

http://www.habanero.rice.edu/Publications.html (JCUDA) : A library that can translate special Java Code (called JCUDA code) into Java- and CUDA-C code, which can then be compiled and executed on the GPU. However, the library does not seem to be publicly available.

https://www2.informatik.uni-erlangen.de/EN/research/JavaOpenMP/index.html : Java language extension for for OpenMP constructs, with a CUDA backend

Java OpenCL/CUDA binding libraries

https://github.com/ochafik/JavaCL : Java bindings for OpenCL: An object-oriented OpenCL library, based on auto-generated low-level bindings

http://jogamp.org/jocl/www/ : Java bindings for OpenCL: An object-oriented OpenCL library, based on auto-generated low-level bindings

http://www.lwjgl.org/ : Java bindings for OpenCL: Auto-generated low-level bindings and object-oriented convenience classes

http://jocl.org/ : Java bindings for OpenCL: Low-level bindings that are a 1:1 mapping of the original OpenCL API

http://jcuda.org/ : Java bindings for CUDA: Low-level bindings that are a 1:1 mapping of the original CUDA API

Miscellaneous

http://sourceforge.net/projects/jopencl/ : Java bindings for OpenCL. Seem to be no longer maintained since 2010

http://www.hoopoe-cloud.com/ : Java bindings for CUDA. Seem to be no longer maintained


How to run python script with elevated privilege on windows

Make sure you have python in path,if not,win key + r, type in "%appdata%"(without the qotes) open local directory, then go to Programs directory ,open python and then select your python version directory. Click on file tab and select copy path and close file explorer.

Then do win key + r again, type control and hit enter. search for environment variables. click on the result, you will get a window. In the bottom right corner click on environmental variables. In the system side find path, select it and click on edit. In the new window, click on new and paste the path in there. Click ok and then apply in the first window. Restart your PC. Then do win + r for the last time, type cmd and do ctrl + shift + enter. Grant the previliges and open file explorer, goto your script and copy its path. Go back into cmd , type in "python" and paste the path and hit enter. Done

Is it possible to clone html element objects in JavaScript / JQuery?

Using your code you can do something like this in plain JavaScript using the cloneNode() method:

// Create a clone of element with id ddl_1:
let clone = document.querySelector('#ddl_1').cloneNode( true );

// Change the id attribute of the newly created element:
clone.setAttribute( 'id', newId );

// Append the newly created element on element p 
document.querySelector('p').appendChild( clone );

Or using jQuery clone() method (not the most efficient):

$('#ddl_1').clone().attr('id', newId).appendTo('p'); // append to where you want

Angular2, what is the correct way to disable an anchor element?

I have used

tabindex="{{isEditedParaOrder?-1:0}}" 
[style.pointer-events]="isEditedParaOrder ?'none':'auto'" 

in my anchor tag so that they can not move to anchor tag by using tab to use "enter" key and also pointer itself we are setting to 'none' based on property 'isEditedParaO rder' whi

How to add and remove item from array in components in Vue 2

You can use Array.push() for appending elements to an array.

For deleting, it is best to use this.$delete(array, index) for reactive objects.

Vue.delete( target, key ): Delete a property on an object. If the object is reactive, ensure the deletion triggers view updates. This is primarily used to get around the limitation that Vue cannot detect property deletions, but you should rarely need to use it.

https://vuejs.org/v2/api/#Vue-delete

How to get margin value of a div in plain JavaScript?

The properties on the style object are only the styles applied directly to the element (e.g., via a style attribute or in code). So .style.marginTop will only have something in it if you have something specifically assigned to that element (not assigned via a style sheet, etc.).

To get the current calculated style of the object, you use either the currentStyle property (Microsoft) or the getComputedStyle function (pretty much everyone else).

Example:

var p = document.getElementById("target");
var style = p.currentStyle || window.getComputedStyle(p);

display("Current marginTop: " + style.marginTop);

Fair warning: What you get back may not be in pixels. For instance, if I run the above on a p element in IE9, I get back "1em".

Live Copy | Source

jQuery .val change doesn't change input value

For me the problem was that changing the value for this field didn`t work:

$('#cardNumber').val(maskNumber);

None of the solutions above worked for me so I investigated further and found:

According to DOM Level 2 Event Specification: The change event occurs when a control loses the input focus and its value has been modified since gaining focus. That means that change event is designed to fire on change by user interaction. Programmatic changes do not cause this event to be fired.

The solution was to add the trigger function and cause it to trigger change event like this:

$('#cardNumber').val(maskNumber).trigger('change');

How do I convert a date/time to epoch time (unix time/seconds since 1970) in Perl?

There are many Date manipulation modules on CPAN. My particular favourite is DateTime and you can use the strptime modules to parse dates in arbitrary formats. There are also many DateTime::Format modules on CPAN for handling specialised date formats, but strptime is the most generic.

How to remove gaps between subplots in matplotlib?

Another method is to use the pad keyword from plt.subplots_adjust(), which also accepts negative values:

import matplotlib.pyplot as plt

ax = [plt.subplot(2,2,i+1) for i in range(4)]

for a in ax:
    a.set_xticklabels([])
    a.set_yticklabels([])

plt.subplots_adjust(pad=-5.0)

Additionally, to remove the white at the outer fringe of all subplots (i.e. the canvas), always save with plt.savefig(fname, bbox_inches="tight").

How can I disable the Maven Javadoc plugin from the command line?

The Javadoc generation can be skipped by setting the property maven.javadoc.skip to true [1], i.e.

-Dmaven.javadoc.skip=true

(and not false)

jquery mobile background image

None of the above worked for me using JQM 1.2.0

This did work for me:

.ui-page.ui-body-c {
    background: url(bg.png);
    background-repeat:no-repeat;
    background-position:center center;
    background-size:cover;  
}

Error: Cannot access file bin/Debug/... because it is being used by another process

Run taskmanager.
Locate netcore and delete it.
You can then delete the file manually or by running Clean.

How to NodeJS require inside TypeScript file?

The correct syntax is:

import sampleModule = require('modulename');

or

import * as sampleModule from 'modulename';

Then compile your TypeScript with --module commonjs.

If the package doesn't come with an index.d.ts file and its package.json doesn't have a "typings" property, tsc will bark that it doesn't know what 'modulename' refers to. For this purpose you need to find a .d.ts file for it on http://definitelytyped.org/, or write one yourself.

If you are writing code for Node.js you will also want the node.d.ts file from http://definitelytyped.org/.

Laravel 4: how to run a raw SQL?

This is my simplified example of how to run RAW SELECT, get result and access the values.

$res = DB::select('
        select count(id) as c
        from prices p 
        where p.type in (2,3)
    ');
    if ($res[0]->c > 10)
    {
        throw new Exception('WOW');
    }

If you want only run sql script with no return resutl use this

DB::statement('ALTER TABLE products MODIFY COLUMN physical tinyint(1) AFTER points;');

Tested in laravel 5.1

Can you force Visual Studio to always run as an Administrator in Windows 8?

VSCommands didn't work for me and caused a problem when I installed Visual Studio 2010 aside of Visual Studio 2012.

After some experimentations I found the trick:

Go to HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers and add an entry with the name "C:\Program Files (x86)\Common Files\Microsoft Shared\MSEnv\VSLauncher.exe" and the value "RUNASADMIN".

This should solve your issue. I've also blogged about that.

Get underlined text with Markdown

The simple <u>some text</u> should work for you.