Programs & Examples On #Boinc

Berkeley Open Infrastructure for Network Computing (BOINC) is a middleware system for volunteer and Grid computing

Apache: "AuthType not set!" 500 Error

Alternatively, this solution works with both Apache2 version < 2.4 as well as >= 2.4. Make sure that the "version" module is enabled:

a2enmod version

And then use this code instead:

<IfVersion < 2.4>
    Allow from all
</IfVersion>
<IfVersion >= 2.4>
    Require all granted
</IfVersion>

Python causing: IOError: [Errno 28] No space left on device: '../results/32766.html' on disk with lots of space

  1. Show where memory is allocated sudo du -x -h / | sort -h | tail -40
  2. Delete from either your /tmp or /home/user_name/.cache folder if these are taking up a lot of memory. You can do this by running sudo rm -R /path/to/folder

Step 2 outlines fairly common folders to delete from (/tmp and /home/user_name/.cache). If you get back other results when running the first command showing you have lots of memory being used elsewhere, I advise being a bit more cautious when deleting from those locations.

Best way to find os name and version in Unix/Linux platform

The "lsb_release" command provides certain Linux Standard Base and distribution-specific information. So using the below command we can get Operating system name and operating system version.

"lsb_release -a"

Write HTML file using Java

It really depends on the type of HTML file you're creating.

For such tasks, I use to create an object, serialize it to XML, then transform it with XSL. The pros of this approach are:

  • The strict separation between source code and HTML template,
  • The possibility to edit HTML without having to recompile the application,
  • The ability to serve different HTML in different cases based on the same XML, or even serve XML directly when needed (for a further deserialization for example),
  • The shorter amount of code to write.

The cons are:

  • You must know XSLT and know how to implement it in Java.
  • You must write XSLT (and it's torture for many developers).
  • When transforming XML to HTML with XSLT, some parts may be tricky. Few examples: <textarea/> tags (which make the page unusable), XML declaration (which can cause problems with IE), whitespace (with <pre></pre> tags etc.), HTML entities (&nbsp;), etc.
  • The performance will be reduced, since serialization to XML wastes lots of CPU resources and XSL transformation is very costly too.

Now, if your HTML is very short or very repetitive or if the HTML has a volatile structure which changes dynamically, this approach must not be taken in account. On the other hand, if you serve HTML files which have all a similar structure and you want to reduce the amount of Java code and use templates, this approach may work.

Simple CSS: Text won't center in a button

You can bootstrap. Now a days, almost all websites are developed using bootstrap. You can simply add bootstrap link in head of html file. Now simply add class="btn btn-primary" and your button will look like a normal button. Even you can use btn class on a tag as well, it will look like button on UI.

Is there a "theirs" version of "git merge -s ours"?

Add the -X option to theirs. For example:

git checkout branchA
git merge -X theirs branchB

Everything will merge in the desired way.

The only thing I've seen cause problems is if files were deleted from branchB. They show up as conflicts if something other than git did the removal.

The fix is easy. Just run git rm with the name of any files that were deleted:

git rm {DELETED-FILE-NAME}

After that, the -X theirs should work as expected.

Of course, doing the actual removal with the git rm command will prevent the conflict from happening in the first place.


Note: A longer form option also exists.

To use it, replace:

-X theirs

with:

--strategy-option=theirs

Splitting comma separated string in a PL/SQL stored proc

Here is a good solution:

FUNCTION comma_to_table(iv_raw IN VARCHAR2) RETURN dbms_utility.lname_array IS
   ltab_lname dbms_utility.lname_array;
   ln_len     BINARY_INTEGER;
BEGIN
   dbms_utility.comma_to_table(list   => iv_raw
                              ,tablen => ln_len
                              ,tab    => ltab_lname);
   FOR i IN 1 .. ln_len LOOP
      dbms_output.put_line('element ' || i || ' is ' || ltab_lname(i));
   END LOOP;
   RETURN ltab_lname;
END;

Source: CSV - comma separated values - and PL/SQL (link no longer valid)

Hash Map in Python

Here is the implementation of the Hash Map using python For the simplicity hash map is of a fixed size 16. This can be changed easily. Rehashing is out of scope of this code.

class Node:
    def __init__(self, key, value):
        self.key = key
        self.value = value
        self.next = None

class HashMap:
    def __init__(self):
        self.store = [None for _ in range(16)]
    def get(self, key):
        index = hash(key) & 15
        if self.store[index] is None:
            return None
        n = self.store[index]
        while True:
            if n.key == key:
                return n.value
            else:
                if n.next:
                    n = n.next
                else:
                    return None
    def put(self, key, value):
        nd = Node(key, value)
        index = hash(key) & 15
        n = self.store[index]
        if n is None:
            self.store[index] = nd
        else:
            if n.key == key:
                n.value = value
            else:
                while n.next:
                    if n.key == key:
                        n.value = value
                        return
                    else:
                        n = n.next
                n.next = nd

hm = HashMap()
hm.put("1", "sachin")
hm.put("2", "sehwag")
hm.put("3", "ganguly")
hm.put("4", "srinath")
hm.put("5", "kumble")
hm.put("6", "dhoni")
hm.put("7", "kohli")
hm.put("8", "pandya")
hm.put("9", "rohit")
hm.put("10", "dhawan")
hm.put("11", "shastri")
hm.put("12", "manjarekar")
hm.put("13", "gupta")
hm.put("14", "agarkar")
hm.put("15", "nehra")
hm.put("16", "gawaskar")
hm.put("17", "vengsarkar")
print(hm.get("1"))
print(hm.get("2"))
print(hm.get("3"))
print(hm.get("4"))
print(hm.get("5"))
print(hm.get("6"))
print(hm.get("7"))
print(hm.get("8"))
print(hm.get("9"))
print(hm.get("10"))
print(hm.get("11"))
print(hm.get("12"))
print(hm.get("13"))
print(hm.get("14"))
print(hm.get("15"))
print(hm.get("16"))
print(hm.get("17"))

Output:

sachin
sehwag
ganguly
srinath
kumble
dhoni
kohli
pandya
rohit
dhawan
shastri
manjarekar
gupta
agarkar
nehra
gawaskar
vengsarkar

Set background colour of cell to RGB value of data in cell

Cells cannot be changed from within a VBA function used as a worksheet formula. Except via this workaround...

Put this function into a new module:

Function SetRGB(x As Range, R As Byte, G As Byte, B As Byte)
  On Error Resume Next
  x.Interior.Color = RGB(R, G, B)
  x.Font.Color = IIf(0.299 * R + 0.587 * G + 0.114 * B < 128, vbWhite, vbBlack)
End Function

Then use this formula in your sheet, for example in cell D2:

=HYPERLINK(SetRGB(D2;A2;B2;C2);"HOVER!")

Once you hover the mouse over the cell (try it!), the background color updates to the RGB taken from cells A2 to C2. The font color is a contrasting white or black.

String "true" and "false" to boolean

There isn't any built-in way to handle this (although actionpack might have a helper for that). I would advise something like this

def to_boolean(s)
  s and !!s.match(/^(true|t|yes|y|1)$/i)
end

# or (as Pavling pointed out)

def to_boolean(s)
  !!(s =~ /^(true|t|yes|y|1)$/i)
end

What works as well is to use 0 and non-0 instead of false/true literals:

def to_boolean(s)
  !s.to_i.zero?
end

What is the difference between atomic / volatile / synchronized?

You are specifically asking about how they internally work, so here you are:

No synchronization

private int counter;

public int getNextUniqueIndex() {
  return counter++; 
}

It basically reads value from memory, increments it and puts back to memory. This works in single thread but nowadays, in the era of multi-core, multi-CPU, multi-level caches it won't work correctly. First of all it introduces race condition (several threads can read the value at the same time), but also visibility problems. The value might only be stored in "local" CPU memory (some cache) and not be visible for other CPUs/cores (and thus - threads). This is why many refer to local copy of a variable in a thread. It is very unsafe. Consider this popular but broken thread-stopping code:

private boolean stopped;

public void run() {
    while(!stopped) {
        //do some work
    }
}

public void pleaseStop() {
    stopped = true;
}

Add volatile to stopped variable and it works fine - if any other thread modifies stopped variable via pleaseStop() method, you are guaranteed to see that change immediately in working thread's while(!stopped) loop. BTW this is not a good way to interrupt a thread either, see: How to stop a thread that is running forever without any use and Stopping a specific java thread.

AtomicInteger

private AtomicInteger counter = new AtomicInteger();

public int getNextUniqueIndex() {
  return counter.getAndIncrement();
}

The AtomicInteger class uses CAS (compare-and-swap) low-level CPU operations (no synchronization needed!) They allow you to modify a particular variable only if the present value is equal to something else (and is returned successfully). So when you execute getAndIncrement() it actually runs in a loop (simplified real implementation):

int current;
do {
  current = get();
} while(!compareAndSet(current, current + 1));

So basically: read; try to store incremented value; if not successful (the value is no longer equal to current), read and try again. The compareAndSet() is implemented in native code (assembly).

volatile without synchronization

private volatile int counter;

public int getNextUniqueIndex() {
  return counter++; 
}

This code is not correct. It fixes the visibility issue (volatile makes sure other threads can see change made to counter) but still has a race condition. This has been explained multiple times: pre/post-incrementation is not atomic.

The only side effect of volatile is "flushing" caches so that all other parties see the freshest version of the data. This is too strict in most situations; that is why volatile is not default.

volatile without synchronization (2)

volatile int i = 0;
void incIBy5() {
  i += 5;
}

The same problem as above, but even worse because i is not private. The race condition is still present. Why is it a problem? If, say, two threads run this code simultaneously, the output might be + 5 or + 10. However, you are guaranteed to see the change.

Multiple independent synchronized

void incIBy5() {
  int temp;
  synchronized(i) { temp = i }
  synchronized(i) { i = temp + 5 }
}

Surprise, this code is incorrect as well. In fact, it is completely wrong. First of all you are synchronizing on i, which is about to be changed (moreover, i is a primitive, so I guess you are synchronizing on a temporary Integer created via autoboxing...) Completely flawed. You could also write:

synchronized(new Object()) {
  //thread-safe, SRSLy?
}

No two threads can enter the same synchronized block with the same lock. In this case (and similarly in your code) the lock object changes upon every execution, so synchronized effectively has no effect.

Even if you have used a final variable (or this) for synchronization, the code is still incorrect. Two threads can first read i to temp synchronously (having the same value locally in temp), then the first assigns a new value to i (say, from 1 to 6) and the other one does the same thing (from 1 to 6).

The synchronization must span from reading to assigning a value. Your first synchronization has no effect (reading an int is atomic) and the second as well. In my opinion, these are the correct forms:

void synchronized incIBy5() {
  i += 5 
}

void incIBy5() {
  synchronized(this) {
    i += 5 
  }
}

void incIBy5() {
  synchronized(this) {
    int temp = i;
    i = temp + 5;
  }
}

Is there a method to generate a UUID with go language

The go-uuid library is NOT RFC4122 compliant. The variant bits are not set correctly. There have been several attempts by community members to have this fixed but pull requests for the fix are not being accepted.

You can generate UUIDs using the Go uuid library I rewrote based on the go-uuid library. There are several fixes and improvements. This can be installed with:

go get github.com/twinj/uuid

You can generate random (version 4) UUIDs with:

import "github.com/twinj/uuid"

u := uuid.NewV4()

The returned UUID type is an interface and the underlying type is an array.

The library also generates v1 UUIDs and correctly generates v3 and 5 UUIDs. There are several new methods to help with printing and formatting and also new general methods to create UUIDs based off of existing data.

ASP.NET postback with JavaScript

First, don't use update panels. They are the second most evil thing that Microsoft has ever created for the web developer.

Second, if you must use update panels, try setting the UpdateMode property to Conditional. Then add a trigger to an Asp:Hidden control that you add to the page. Assign the change event as the trigger. In your dragstop event, change the value of the hidden control.

This is untested, but the theory seems sound... If this does not work, you could try the same thing with an asp:button, just set the display:none style on it and use the click event instead of the change event.

Best way to specify whitespace in a String.Split operation

If repeating the same code is the issue, write an extension method on the String class that encapsulates the splitting logic.

Operand type clash: uniqueidentifier is incompatible with int

The reason is that the data doesn't match the datatype. I have come across the same issues that I forgot to make the fields match. Though my case is not same as yours, but it shows the similar error message.

The situation is that I copy a table, but accidently I misspell one field, so I change it using the ALTER after creating the database. And the order of fields in both table is not identical. so when I use the INSERT INTO TableName SELECT * FROM TableName, the result showed the similar errors: Operand type clash: datetime is incompatible with uniqueidentifier

This is a simiple example:

use example
go
create table Test1 (
    id int primary key,
    item uniqueidentifier,
    inserted_at datetime
    )
go
create table Test2 (
    id int primary key,
    inserted_at datetime
    )
go
alter table Test2 add item uniqueidentifier;
go

--insert into Test1 (id, item, inserted_at) values (1, newid(), getdate()), (2, newid(), getdate());


insert into Test2 select * from Test1;

select * from Test1;
select * from Test2;


The error message is:

Msg 206, Level 16, State 2, Line 24
Operand type clash: uniqueidentifier is incompatible with datetime

LINQ-to-SQL vs stored procedures?

I think you need to go with procs for anything real.

A) Writing all your logic in linq means your database is less useful because only your application can consume it.

B) I'm not convinced that object modelling is better than relational modelling anyway.

C) Testing and developing a stored procedure in SQL is a hell of a lot faster than a compile edit cycle in any Visual Studio environment. You just edit, F5 and hit select and you are off to the races.

D) It's easier to manage and deploy stored procedures than assemblies.. you just put the file on the server, and press F5...

E) Linq to sql still writes crappy code at times when you don't expect it.

Honestly, I think the ultimate thing would be for MS to augment t-sql so that it can do a join projection impliclitly the way linq does. t-sql should know if you wanted to do order.lineitems.part, for example.

database vs. flat files

Don't build it if you can buy it.

I heard this quote recently, and it really seems fitting as a guide line. Ask yourself this... How much time was spent working on the file handling portion of your app? I suspect a fair amount of time was spent optimizing this code for performance. If you had been using a relational database all along, you would have spent considerably less time handling this portion of your application. You would have had more time for the true "business" aspect of your app.

Is JavaScript guaranteed to be single-threaded?

JavaScript/ECMAScript is designed to live within a host environment. That is, JavaScript doesn't actually do anything unless the host environment decides to parse and execute a given script, and provide environment objects that let JavaScript actually be useful (such as the DOM in browsers).

I think a given function or script block will execute line-by-line and that is guaranteed for JavaScript. However, perhaps a host environment could execute multiple scripts at the same time. Or, a host environment could always provide an object that provides multi-threading. setTimeout and setInterval are examples, or at least pseudo-examples, of a host environment providing a way to do some concurrency (even if it's not exactly concurrency).

Programmatically change the height and width of a UIImageView Xcode Swift

imageView is a subview of the main view. It works this way

image.frame = CGRectMake(0 , 0, super.view.frame.width, super.view.frame.height * 0.2)

How to add a line to a multiline TextBox?

I would go with the System.Environment.NewLine or a StringBuilder

Then you could add lines with a string builder like this:

StringBuilder sb = new StringBuilder();
sb.AppendLine("brown");
sb.AppendLine("brwn");

textbox1.Text += sb.ToString();

or NewLine like this:

textbox1.Text += System.Environment.NewLine + "brown";

Better:

StringBuilder sb = new StringBuilder(textbox1.Text);
sb.AppendLine("brown");
sb.AppendLine("brwn");

textbox1.Text = sb.ToString();

What is an optional value in Swift?

From https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/OptionalChaining.html:

Optional chaining is a process for querying and calling properties, methods, and subscripts on an optional that might currently be nil. If the optional contains a value, the property, method, or subscript call succeeds; if the optional is nil, the property, method, or subscript call returns nil. Multiple queries can be chained together, and the entire chain fails gracefully if any link in the chain is nil.

To understand deeper, read the link above.

CodeIgniter - accessing $config variable in view

You can do something like that:

$ci = get_instance(); // CI_Loader instance
$ci->load->config('email');
echo $ci->config->item('name');

Restricting input to textbox: allowing only numbers and decimal point

_x000D_
_x000D_
<HTML>_x000D_
  <HEAD>_x000D_
    <SCRIPT language=Javascript>_x000D_
       <!--_x000D_
       function isNumberKey(evt)_x000D_
       {_x000D_
          var charCode = (evt.which) ? evt.which : evt.keyCode;_x000D_
          if (charCode != 46 && charCode > 31 _x000D_
            && (charCode < 48 || charCode > 57))_x000D_
             return false;_x000D_
_x000D_
          return true;_x000D_
       }_x000D_
       //-->_x000D_
    </SCRIPT>_x000D_
  </HEAD>_x000D_
  <BODY>_x000D_
    <INPUT id="txtChar" onkeypress="return isNumberKey(event)" _x000D_
           type="text" name="txtChar">_x000D_
  </BODY>_x000D_
</HTML>
_x000D_
_x000D_
_x000D_

This really works!

Automatic prune with Git fetch or pull

git config --global fetch.prune true

To always --prune for git fetch and git pull in all your Git repositories:

git config --global fetch.prune true

This above command appends in your global Git configuration (typically ~/.gitconfig) the following lines. Use git config -e --global to view your global configuration.

[fetch]
    prune = true

git config remote.origin.prune true

To always --prune but from one single repository:

git config remote.origin.prune true
                 #^^^^^^
                 #replace with your repo name

This above command adds in your local Git configuration (typically .git/config) the below last line. Use git config -e to view your local configuration.

[remote "origin"]
    url = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    fetch = +refs/heads/*:refs/remotes/origin/*
    prune = true

You can also use --global within the second command or use instead --local within the first command.


git config --global gui.pruneDuringFetch true

If you use git gui you may also be interested by:

git config --global gui.pruneDuringFetch true

that appends:

[gui]
    pruneDuringFetch = true

References

The corresponding documentations from git help config:

--global

  For writing options: write to global ~/.gitconfig file rather than the repository .git/config, write to $XDG_CONFIG_HOME/git/config file if this file exists and the ~/.gitconfig file doesn’t.

 

--local

  For writing options: write to the repository .git/config file. This is the default behavior.

 

fetch.prune

  If true, fetch will automatically behave as if the --prune option was given on the command line. See also remote.<name>.prune.

 

gui.pruneDuringFetch

  "true" if git-gui should prune remote-tracking branches when performing a fetch. The default value is "false".

 

remote.<name>.prune

  When set to true, fetching from this remote by default will also remove any remote-tracking references that no longer exist on the remote (as if the --prune option was given on the command line). Overrides fetch.prune settings, if any.

Find the server name for an Oracle database

The query below demonstrates use of the package and some of the information you can get.

select sys_context ( 'USERENV', 'DB_NAME' ) db_name,
sys_context ( 'USERENV', 'SESSION_USER' ) user_name,
sys_context ( 'USERENV', 'SERVER_HOST' ) db_host,
sys_context ( 'USERENV', 'HOST' ) user_host
from dual

NOTE: The parameter ‘SERVER_HOST’ is available in 10G only.

Any Oracle User that can connect to the database can run a query against “dual”. No special permissions are required and SYS_CONTEXT provides a greater range of application-specific information than “sys.v$instance”.

Difference between thread's context class loader and normal classloader

This does not answer the original question, but as the question is highly ranked and linked for any ContextClassLoader query, I think it is important to answer the related question of when the context class loader should be used. Short answer: never use the context class loader! But set it to getClass().getClassLoader() when you have to call a method that is missing a ClassLoader parameter.

When code from one class asks to load another class, the correct class loader to use is the same class loader as the caller class (i.e., getClass().getClassLoader()). This is the way things work 99.9% of the time because this is what the JVM does itself the first time you construct an instance of a new class, invoke a static method, or access a static field.

When you want to create a class using reflection (such as when deserializing or loading a configurable named class), the library that does the reflection should always ask the application which class loader to use, by receiving the ClassLoader as a parameter from the application. The application (which knows all the classes that need constructing) should pass it getClass().getClassLoader().

Any other way to obtain a class loader is incorrect. If a library uses hacks such as Thread.getContextClassLoader(), sun.misc.VM.latestUserDefinedLoader(), or sun.reflect.Reflection.getCallerClass() it is a bug caused by a deficiency in the API. Basically, Thread.getContextClassLoader() exists only because whoever designed the ObjectInputStream API forgot to accept the ClassLoader as a parameter, and this mistake has haunted the Java community to this day.

That said, many many JDK classes use one of a few hacks to guess some class loader to use. Some use the ContextClassLoader (which fails when you run different apps on a shared thread pool, or when you leave the ContextClassLoader null), some walk the stack (which fails when the direct caller of the class is itself a library), some use the system class loader (which is fine, as long as it is documented to only use classes in the CLASSPATH) or bootstrap class loader, and some use an unpredictable combination of the above techniques (which only makes things more confusing). This has resulted in much weeping and gnashing of teeth.

When using such an API, first, try to find an overload of the method that accepts the class loader as a parameter. If there is no sensible method, then try setting the ContextClassLoader before the API call (and resetting it afterwards):

ClassLoader originalClassLoader = Thread.currentThread().getContextClassLoader();
try {
    Thread.currentThread().setContextClassLoader(getClass().getClassLoader());
    // call some API that uses reflection without taking ClassLoader param
} finally {
    Thread.currentThread().setContextClassLoader(originalClassLoader);
}

How do I disable form fields using CSS?

The practical solution is to use CSS to actually hide the input.

To take this to its natural conclusion, you can write two html inputs for each actual input (one enabled, and one disabled) and then use javascript to control the CSS to show and hide them.

Printing tuple with string formatting in Python

I think the best way to do this is:

t = (1,2,3)

print "This is a tuple: %s" % str(t)

If you're familiar with printf style formatting, then Python supports its own version. In Python, this is done using the "%" operator applied to strings (an overload of the modulo operator), which takes any string and applies printf-style formatting to it.

In our case, we are telling it to print "This is a tuple: ", and then adding a string "%s", and for the actual string, we're passing in a string representation of the tuple (by calling str(t)).

If you're not familiar with printf style formatting, I highly suggest learning, since it's very standard. Most languages support it in one way or another.

React native text going off my screen, refusing to wrap. What to do?

This is a known bug. flexWrap: 'wrap' didn't work for me but this solution seems to work for most people

Code

<View style={styles.container}>
    <Text>Some text</Text>
</View>

Styles

export default StyleSheet.create({
    container: {
        width: 0,
        flexGrow: 1,
        flex: 1,
    }
});

Parsing JSON array with PHP foreach

You need to tell it which index in data to use, or double loop through all.

E.g., to get the values in the 4th index in the outside array.:

foreach($user->data[3]->values as $values)
{
     echo $values->value . "\n";
}

To go through all:

foreach($user->data as $mydata)
{
    foreach($mydata->values as $values) {
        echo $values->value . "\n";
    }

}   

Python requests - print entire http request (raw)?

import requests

response = requests.post('http://httpbin.org/post', data={'key1':'value1'})
print(response.request.url)
print(response.request.body)
print(response.request.headers)

Response objects have a .request property which is the original PreparedRequest object that was sent.

NodeJS: How to decode base64 encoded string back to binary?

As of Node.js v6.0.0 using the constructor method has been deprecated and the following method should instead be used to construct a new buffer from a base64 encoded string:

var b64string = /* whatever */;
var buf = Buffer.from(b64string, 'base64'); // Ta-da

For Node.js v5.11.1 and below

Construct a new Buffer and pass 'base64' as the second argument:

var b64string = /* whatever */;
var buf = new Buffer(b64string, 'base64'); // Ta-da

If you want to be clean, you can check whether from exists :

if (typeof Buffer.from === "function") {
    // Node 5.10+
    buf = Buffer.from(b64string, 'base64'); // Ta-da
} else {
    // older Node versions, now deprecated
    buf = new Buffer(b64string, 'base64'); // Ta-da
}

Is multiplication and division using shift operators in C actually faster?

Shifting is generally a lot faster than multiplying at an instruction level but you may well be wasting your time doing premature optimisations. The compiler may well perform these optimisations at compiletime. Doing it yourself will affect readability and possibly have no effect on performance. It's probably only worth it to do things like this if you have profiled and found this to be a bottleneck.

Actually the division trick, known as 'magic division' can actually yield huge payoffs. Again you should profile first to see if it's needed. But if you do use it there are useful programs around to help you figure out what instructions are needed for the same division semantics. Here is an example : http://www.masm32.com/board/index.php?topic=12421.0

An example which I have lifted from the OP's thread on MASM32:

include ConstDiv.inc
...
mov eax,9999999
; divide eax by 100000
cdiv 100000
; edx = quotient

Would generate:

mov eax,9999999
mov edx,0A7C5AC47h
add eax,1
.if !CARRY?
    mul edx
.endif
shr edx,16

How to hide keyboard in swift on pressing return key?

Here's the Swift 3.0 update to peacetype's comment:

textField.addTarget(nil, action:Selector(("firstResponderAction:")), for:.editingDidEndOnExit)

How to hide column of DataGridView when using custom DataSource?

If you want to use the BrowsableAttribute, then you can look for it at runtime on the model and hide the column accordingly:

private void Form_Load(object sender, EventArgs e)
{
    //add this line after your DataGridView initialization
    HideColumns<MyModel>(myDvg);
}

private void HideColumns<T>(DataGridView dvg)
{
    var type = typeof(T);
    foreach (var column in dvg.Columns.Cast<DataGridViewColumn>())
        column.Visible = IsBrowsable(type.GetProperty(column.Name));
}

private bool IsBrowsable(PropertyInfo propertyInfo)
{
    var attribute = propertyInfo.GetCustomAttributes(true).FirstOrDefault(att => att.GetType() == typeof(BrowsableAttribute));
    return attribute == null || (attribute as BrowsableAttribute).Browsable;
}

How do I make an editable DIV look like a text field?

I would suggest this for matching Chrome's style, extended from Jarish's example. Notice the cursor property which previous answers have omitted.

cursor: text;
border: 1px solid #ccc;
font: medium -moz-fixed;
font: -webkit-small-control;
height: 200px;
overflow: auto;
padding: 2px;
resize: both;
-moz-box-shadow: inset 0px 1px 2px #ccc;
-webkit-box-shadow: inset 0px 1px 2px #ccc;
box-shadow: inset 0px 1px 2px #ccc;

Creating a BLOB from a Base64 string in JavaScript

For image data, I find it simpler to use canvas.toBlob (asynchronous)

function b64toBlob(b64, onsuccess, onerror) {
    var img = new Image();

    img.onerror = onerror;

    img.onload = function onload() {
        var canvas = document.createElement('canvas');
        canvas.width = img.width;
        canvas.height = img.height;

        var ctx = canvas.getContext('2d');
        ctx.drawImage(img, 0, 0, canvas.width, canvas.height);

        canvas.toBlob(onsuccess);
    };

    img.src = b64;
}

var base64Data = 'data:image/jpg;base64,/9j/4AAQSkZJRgABAQA...';
b64toBlob(base64Data,
    function(blob) {
        var url = window.URL.createObjectURL(blob);
        // do something with url
    }, function(error) {
        // handle error
    });

Unknown URL content://downloads/my_downloads

For those who are getting Error Unknown URI: content://downloads/public_downloads. I managed to solve this by getting a hint given by @Commonsware in this answer. I found out the class FileUtils on GitHub. Here InputStream methods are used to fetch file from Download directory.

 // DownloadsProvider
            else if (isDownloadsDocument(uri)) {

                final String id = DocumentsContract.getDocumentId(uri);

                if (id != null && id.startsWith("raw:")) {
                    return id.substring(4);
                }

                String[] contentUriPrefixesToTry = new String[]{
                        "content://downloads/public_downloads",
                        "content://downloads/my_downloads",
                        "content://downloads/all_downloads"
                };

                for (String contentUriPrefix : contentUriPrefixesToTry) {
                    Uri contentUri = ContentUris.withAppendedId(Uri.parse(contentUriPrefix), Long.valueOf(id));
                    try {
                        String path = getDataColumn(context, contentUri, null, null);
                        if (path != null) {
                            return path;
                        }
                    } catch (Exception e) {}
                }

                // path could not be retrieved using ContentResolver, therefore copy file to accessible cache using streams
                String fileName = getFileName(context, uri);
                File cacheDir = getDocumentCacheDir(context);
                File file = generateFileName(fileName, cacheDir);
                String destinationPath = null;
                if (file != null) {
                    destinationPath = file.getAbsolutePath();
                    saveFileFromUri(context, uri, destinationPath);
                }

                return destinationPath;
            }

vertical-align with Bootstrap 3

I just did this and it does what I want it to do.

.align-middle {
  margin-top: 25%;
  margin-bottom: 25%;
}

And now my page looks like

<div class='container-fluid align-middle'>
    content

 +--------------------------------+
 |                                |
 |  +--------------------------+  |
 |  |                          |  |
 |  |                          |  |
 |  |                          |  |
 |  |                          |  |
 |  |                          |  |
 |  +--------------------------+  |
 |                                |
 +--------------------------------+

How can I set the default timezone in node.js?

just set environment variable in your main file like index.js or app.js or main.js or whatever your file name is:

process.env.TZ = "Asia/Tehran";

this will set the timezone which will be used in your entire node application

How to compare types

If your instance is a Type:

Type typeFiled;
if (typeField == typeof(string))
{ 
    ... 
}

but if your instance is an object and not a Type use the as operator:

object value;
string text = value as string;
if (text != null)
{
    // value is a string and you can do your work here
}

this has the advantage to convert value only once into the specified type.

Importing a CSV file into a sqlite3 database table using Python

My 2 cents (more generic):

import csv, sqlite3
import logging

def _get_col_datatypes(fin):
    dr = csv.DictReader(fin) # comma is default delimiter
    fieldTypes = {}
    for entry in dr:
        feildslLeft = [f for f in dr.fieldnames if f not in fieldTypes.keys()]
        if not feildslLeft: break # We're done
        for field in feildslLeft:
            data = entry[field]

            # Need data to decide
            if len(data) == 0:
                continue

            if data.isdigit():
                fieldTypes[field] = "INTEGER"
            else:
                fieldTypes[field] = "TEXT"
        # TODO: Currently there's no support for DATE in sqllite

    if len(feildslLeft) > 0:
        raise Exception("Failed to find all the columns data types - Maybe some are empty?")

    return fieldTypes


def escapingGenerator(f):
    for line in f:
        yield line.encode("ascii", "xmlcharrefreplace").decode("ascii")


def csvToDb(csvFile, outputToFile = False):
    # TODO: implement output to file

    with open(csvFile,mode='r', encoding="ISO-8859-1") as fin:
        dt = _get_col_datatypes(fin)

        fin.seek(0)

        reader = csv.DictReader(fin)

        # Keep the order of the columns name just as in the CSV
        fields = reader.fieldnames
        cols = []

        # Set field and type
        for f in fields:
            cols.append("%s %s" % (f, dt[f]))

        # Generate create table statement:
        stmt = "CREATE TABLE ads (%s)" % ",".join(cols)

        con = sqlite3.connect(":memory:")
        cur = con.cursor()
        cur.execute(stmt)

        fin.seek(0)


        reader = csv.reader(escapingGenerator(fin))

        # Generate insert statement:
        stmt = "INSERT INTO ads VALUES(%s);" % ','.join('?' * len(cols))

        cur.executemany(stmt, reader)
        con.commit()

    return con

How to build an APK file in Eclipse?

Just right click on your project and then go to

*Export -> Android -> Export Android Application -> YOUR_PROJECT_NAME -> Create new key store path -> Fill the detail -> Set the .apk location -> Now you can get your .apk file*

Install it in your mobile.

Python constructor and default value

I would try:

self.wordList = list(wordList)

to force it to make a copy instead of referencing the same object.

Focus Next Element In Tab Index

There is the tabindex property that can be set on component. It specifies in which order the input components should be iterated when selecting one and pressing tab. Values above 0 are reserved for custom navigation, 0 is "in natural order" (so would behave differently if set for the first element), -1 means not keyboard focusable:

<!-- navigate with tab key: -->
<input tabindex="1" type="text"/>
<input tabindex="2" type="text"/>

It can also be set for something else than the text input fields but it is not very obvious what it would do there, if anything at all. Even if the navigation works, maybe better to use "natural order" for anything else than the very obvious user input elements.

No, you do not need JQuery or any scripting at all to support this custom path of navigation. You can implement it on the server side without any JavaScript support. From the other side, the property also works fine in React framework but does not require it.

CURRENT_TIMESTAMP in milliseconds

To get the Unix timestamp in seconds in MySQL:

select UNIX_TIMESTAMP();

Details: http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_unix-timestamp

Not tested PostgreSQL, but according to this site it should work: http://www.raditha.com/postgres/timestamp.php

select round( date_part( 'epoch', now() ) );

align an image and some text on the same line without using div width?

I was working on a different project when I saw this question, this is the solution I used and it seems to work.

#[image id] , p {
        vertical-align: middle;
        display: inline-block;
    }

if it doesn't, just try :

float:right;

float:left;

or display: inline instead of inline-block

This worked for me, hope this helped!

Autocompletion of @author in Intellij

Check Enable Live Templates and leave the cursor at the position desired and click Apply then OK

enter image description here

How to silence output in a Bash script?

Note: This answer is related to the question "How to turn off echo while executing a shell script Linux" which was in turn marked as duplicated to this one.

To actually turn off the echo the command is:

stty -echo

(this is, for instance; when you want to enter a password and you don't want it to be readable. Remember to turn echo on at the end of your script, otherwise the person that runs your script won't see what he/she types in from then on. To turn echo on run:

stty echo

Test if a variable is a list or tuple

Go ahead and use isinstance if you need it. It is somewhat evil, as it excludes custom sequences, iterators, and other things that you might actually need. However, sometimes you need to behave differently if someone, for instance, passes a string. My preference there would be to explicitly check for str or unicode like so:

import types
isinstance(var, types.StringTypes)

N.B. Don't mistake types.StringType for types.StringTypes. The latter incorporates str and unicode objects.

The types module is considered by many to be obsolete in favor of just checking directly against the object's type, so if you'd rather not use the above, you can alternatively check explicitly against str and unicode, like this:

isinstance(var, (str, unicode)):

Edit:

Better still is:

isinstance(var, basestring)

End edit

After either of these, you can fall back to behaving as if you're getting a normal sequence, letting non-sequences raise appropriate exceptions.

See the thing that's "evil" about type checking is not that you might want to behave differently for a certain type of object, it's that you artificially restrict your function from doing the right thing with unexpected object types that would otherwise do the right thing. If you have a final fallback that is not type-checked, you remove this restriction. It should be noted that too much type checking is a code smell that indicates that you might want to do some refactoring, but that doesn't necessarily mean you should avoid it from the getgo.

List all kafka topics

Kafka requires zookeeper and indeed the list of topics is stored there, hence the kafka-topics tool needs to connect to zookeeper too. kafka-clients apis in the newer versions no longer talk to zookeeper directly, perhaps that's why you're under the impression a setup without zookeeper is possible. It is not, as kafka relies on it internally. For reference see: http://kafka.apache.org/documentation.html#quickstart Step 2:

Kafka uses ZooKeeper so you need to first start a ZooKeeper server if you don't already have one

PHP: HTTP or HTTPS?

You should be able to do this by checking the value of $_SERVER['HTTPS'] (it should only be set when using https).

See http://php.net/manual/en/reserved.variables.server.php.

How do I time a method's execution in Java?

In Java 8 a new class named Instant is introduced. As per doc:

Instant represents the start of a nanosecond on the time line. This class is useful for generating a time stamp to represent machine time. The range of an instant requires the storage of a number larger than a long. To achieve this, the class stores a long representing epoch-seconds and an int representing nanosecond-of-second, which will always be between 0 and 999,999,999. The epoch-seconds are measured from the standard Java epoch of 1970-01-01T00:00:00Z where instants after the epoch have positive values, and earlier instants have negative values. For both the epoch-second and nanosecond parts, a larger value is always later on the time-line than a smaller value.

This can be used as:

Instant start = Instant.now();
try {
    Thread.sleep(7000);
} catch (InterruptedException e) {
    e.printStackTrace();
}
Instant end = Instant.now();
System.out.println(Duration.between(start, end));

It prints PT7.001S.

Test a string for a substring

There are several other ways, besides using the in operator (easiest):

index()

>>> try:
...   "xxxxABCDyyyy".index("test")
... except ValueError:
...   print "not found"
... else:
...   print "found"
...
not found

find()

>>> if "xxxxABCDyyyy".find("ABCD") != -1:
...   print "found"
...
found

re

>>> import re
>>> if re.search("ABCD" , "xxxxABCDyyyy"):
...  print "found"
...
found

No 'Access-Control-Allow-Origin' header is present on the requested resource - Resteasy

After facing a similar issue, below is what I did :

  • Created a class extending javax.ws.rs.core.Application and added a Cors Filter to it.

To the CORS filter, I added corsFilter.getAllowedOrigins().add("http://localhost:4200");.

Basically, you should add the URL which you want to allow Cross-Origin Resource Sharing. Ans you can also use "*" instead of any specific URL to allow any URL.

public class RestApplication
    extends Application
{
    private Set<Object> singletons = new HashSet<Object>();

    public MessageApplication()
    {
        singletons.add(new CalculatorService()); //CalculatorService is your specific service you want to add/use.
        CorsFilter corsFilter = new CorsFilter();
        // To allow all origins for CORS add following, otherwise add only specific urls.
        // corsFilter.getAllowedOrigins().add("*");
        System.out.println("To only allow restrcited urls ");
        corsFilter.getAllowedOrigins().add("http://localhost:4200");
        singletons = new LinkedHashSet<Object>();
        singletons.add(corsFilter);
    }

    @Override
    public Set<Object> getSingletons()
    {
        return singletons;
    }
}
  • And here is my web.xml:
<web-app id="WebApp_ID" version="2.4"
    xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <display-name>Restful Web Application</display-name>

    <!-- Auto scan rest service -->
    <context-param>
        <param-name>resteasy.scan</param-name>
        <param-value>true</param-value>
    </context-param>

    <context-param>
        <param-name>resteasy.servlet.mapping.prefix</param-name>
        <param-value>/rest</param-value>
    </context-param>

    <listener>
        <listener-class>
            org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap
        </listener-class>
    </listener>

    <servlet>
        <servlet-name>resteasy-servlet</servlet-name>
        <servlet-class>
            org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher
        </servlet-class>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>com.app.RestApplication</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>resteasy-servlet</servlet-name>
        <url-pattern>/rest/*</url-pattern>
    </servlet-mapping>

</web-app>

The most important code which I was missing when I was getting this issue was, I was not adding my class extending javax.ws.rs.Application i.e RestApplication to the init-param of <servlet-name>resteasy-servlet</servlet-name>

   <init-param>
        <param-name>javax.ws.rs.Application</param-name>
        <param-value>com.app.RestApplication</param-value>
    </init-param>

And therefore my Filter was not able to execute and thus the application was not allowing CORS from the URL specified.

Benefits of inline functions in C++?

Generally speaking, these days with any modern compiler worrying about inlining anything is pretty much a waste of time. The compiler should actually optimize all of these considerations for you through its own analysis of the code and your specification of the optimization flags passed to the compiler. If you care about speed, tell the compiler to optimize for speed. If you care about space, tell the compiler to optimize for space. As another answer alluded to, a decent compiler will even inline automatically if it really makes sense.

Also, as others have stated, using inline does not guarantee inline of anything. If you want to guarantee it, you will have to define a macro instead of an inline function to do it.

When to inline and/or define a macro to force inclusion? - Only when you have a demonstrated and necessary proven increase in speed for a critical section of code that is known to have an affect on the overall performance of the application.

WCF error: The caller was not authenticated by the service

I was able to resolve the shared issue by following below steps:

  1. Go to IIS-->Sites-->Your Site-->
  2. Features View Pane-->Authentication
  3. Set Anonymous Authentication to Disabled
  4. Set Windows Authentication to Enabled

enter image description here

SQLite - getting number of rows in a database

In SQL, NULL = NULL is false, you usually have to use IS NULL:

SELECT CASE WHEN MAX(id) IS NULL THEN 0 ELSE (MAX(id) + 1) END FROM words

But, if you want the number of rows, you should just use count(id) since your solution will give 10 if your rows are (0,1,3,5,9) where it should give 5.

If you can guarantee you will always ids from 0 to N, max(id)+1 may be faster depending on the index implementation (it may be faster to traverse the right side of a balanced tree rather than traversing the whole tree, counting.

But that's very implementation-specific and I would advise against relying on it, not least because it locks your performance to a specific DBMS.

HTTP GET with request body

Which server will ignore it? – fijiaaron Aug 30 '12 at 21:27

Google for instance is doing worse than ignoring it, it will consider it an error!

Try it yourself with a simple netcat:

$ netcat www.google.com 80
GET / HTTP/1.1
Host: www.google.com
Content-length: 6

1234

(the 1234 content is followed by CR-LF, so that is a total of 6 bytes)

and you will get:

HTTP/1.1 400 Bad Request
Server: GFE/2.0
(....)
Error 400 (Bad Request)
400. That’s an error.
Your client has issued a malformed or illegal request. That’s all we know.

You do also get 400 Bad Request from Bing, Apple, etc... which are served by AkamaiGhost.

So I wouldn't advise using GET requests with a body entity.

Good examples using java.util.logging

I'd use minlog, personally. It's extremely simple, as the logging class is a few hundred lines of code.

How to save public key from a certificate in .pem format

if it is a RSA key

openssl rsa  -pubout -in my_rsa_key.pem

if you need it in a format for openssh , please see Use RSA private key to generate public key?

Note that public key is generated from the private key and ssh uses the identity file (private key file) to generate and send public key to server and un-encrypt the encrypted token from the server via the private key in identity file.

How to avoid java.util.ConcurrentModificationException when iterating through and removing elements from an ArrayList

Use Iterator instead of Array List

Have a set be converted to iterator with type match

And move to the next element and remove

Iterator<Insured> itr = insuredSet.iterator();
while (itr.hasNext()) { 
    itr.next();
    itr.remove();
}

Moving to the next is important here as it should take the index to remove element.

Boolean checking in the 'if' condition

The first one. But just another point, the following would also make your code more readable:

if (!status) {
    // do false logic
} else {
    // do true logic
}

Note that there are extra spaces between if and the (, and also before the else statement.

EDIT

As noted by @Mudassir, if there is NO other shared code in the method using the logic, then the better style would be:

if (!status) {
    // do false logic
}

// do true logic

What is w3wp.exe?

An Internet Information Services (IIS) worker process is a windows process (w3wp.exe) which runs Web applications, and is responsible for handling requests sent to a Web Server for a specific application pool.

It is the worker process for IIS. Each application pool creates at least one instance of w3wp.exe and that is what actually processes requests in your application. It is not dangerous to attach to this, that is just a standard windows message.

Java way to check if a string is palindrome

public static boolean istPalindrom(char[] word){
int i1 = 0;
int i2 = word.length - 1;
while (i2 > i1) {
    if (word[i1] != word[i2]) {
        return false;
    }
    ++i1;
    --i2;
}
return true;
}

How do you print in a Go test using the "testing" package?

t.Log() will not show up until after the test is complete, so if you're trying to debug a test that is hanging or performing badly it seems you need to use fmt.

Yes: that was the case up to Go 1.13 (August 2019) included.

And that was followed in golang.org issue 24929

Consider the following (silly) automated tests:

func TestFoo(t *testing.T) {
    t.Parallel()

  for i := 0; i < 15; i++ {
        t.Logf("%d", i)
        time.Sleep(3 * time.Second)
    }
}

func TestBar(t *testing.T) {
    t.Parallel()

  for i := 0; i < 15; i++ {
        t.Logf("%d", i)
        time.Sleep(2 * time.Second)
    }
}

func TestBaz(t *testing.T) {
    t.Parallel()

  for i := 0; i < 15; i++ {
        t.Logf("%d", i)
        time.Sleep(1 * time.Second)
    }
}

If I run go test -v, I get no log output until all of TestFoo is done, then no output until all of TestBar is done, and again no more output until all of TestBaz is done.
This is fine if the tests are working, but if there is some sort of bug, there are a few cases where buffering log output is problematic:

  • When iterating locally, I want to be able to make a change, run my tests, see what's happening in the logs immediately to understand what's going on, hit CTRL+C to shut the test down early if necessary, make another change, re-run the tests, and so on.
    If TestFoo is slow (e.g., it's an integration test), I get no log output until the very end of the test. This significantly slows down iteration.
  • If TestFoo has a bug that causes it to hang and never complete, I'd get no log output whatsoever. In these cases, t.Log and t.Logf are of no use at all.
    This makes debugging very difficult.
  • Moreover, not only do I get no log output, but if the test hangs too long, either the Go test timeout kills the test after 10 minutes, or if I increase that timeout, many CI servers will also kill off tests if there is no log output after a certain amount of time (e.g., 10 minutes in CircleCI).
    So now my tests are killed and I have nothing in the logs to tell me what happened.

But for (possibly) Go 1.14 (Q1 2020): CL 127120

testing: stream log output in verbose mode

The output now is:

=== RUN   TestFoo
=== PAUSE TestFoo
=== RUN   TestBar
=== PAUSE TestBar
=== RUN   TestGaz
=== PAUSE TestGaz
=== CONT  TestFoo
    TestFoo: main_test.go:14: hello from foo
=== CONT  TestGaz
=== CONT  TestBar
    TestGaz: main_test.go:38: hello from gaz
    TestBar: main_test.go:26: hello from bar
    TestFoo: main_test.go:14: hello from foo
    TestBar: main_test.go:26: hello from bar
    TestGaz: main_test.go:38: hello from gaz
    TestFoo: main_test.go:14: hello from foo
    TestGaz: main_test.go:38: hello from gaz
    TestBar: main_test.go:26: hello from bar
    TestFoo: main_test.go:14: hello from foo
    TestGaz: main_test.go:38: hello from gaz
    TestBar: main_test.go:26: hello from bar
    TestGaz: main_test.go:38: hello from gaz
    TestFoo: main_test.go:14: hello from foo
    TestBar: main_test.go:26: hello from bar
--- PASS: TestFoo (1.00s)
--- PASS: TestGaz (1.00s)
--- PASS: TestBar (1.00s)
PASS
ok      dummy/streaming-test    1.022s

It is indeed in Go 1.14, as Dave Cheney attests in "go test -v streaming output":

In Go 1.14, go test -v will stream t.Log output as it happens, rather than hoarding it til the end of the test run.

Under Go 1.14 the fmt.Println and t.Log lines are interleaved, rather than waiting for the test to complete, demonstrating that test output is streamed when go test -v is used.

Advantage, according to Dave:

This is a great quality of life improvement for integration style tests that often retry for long periods when the test is failing.
Streaming t.Log output will help Gophers debug those test failures without having to wait until the entire test times out to receive their output.

Sorting arraylist in alphabetical order (case insensitive)

Based on the above mentioned answers, I managed to compare my custom Class Objects like this:

ArrayList<Item> itemList = new ArrayList<>();
...
Collections.sort(itemList, new Comparator<Item>() {
            @Override
            public int compare(Item item, Item t1) {
                String s1 = item.getTitle();
                String s2 = t1.getTitle();
                return s1.compareToIgnoreCase(s2);
            }

        });

Get just the filename from a path in a Bash script

basename and dirname solutions are more convenient. Those are alternative commands:

FILE_PATH="/opt/datastores/sda2/test.old.img"
echo "$FILE_PATH" | sed "s/.*\///"

This returns test.old.img like basename.

This is salt filename without extension:

echo "$FILE_PATH" | sed -r "s/.+\/(.+)\..+/\1/"

It returns test.old.

And following statement gives the full path like dirname command.

echo "$FILE_PATH" | sed -r "s/(.+)\/.+/\1/"

It returns /opt/datastores/sda2

How do I set Java's min and max heap size through environment variables?

I think your only option is to wrap java in a script that substitutes the environment variables into the command line

How to replace (or strip) an extension from a filename in Python?

I'm surprised nobody has mentioned pathlib's with_name. This solution works with multiple extensions (i.e. it replaces all of the extensions.)

import pathlib

p = pathlib.Path('/some/path/somefile.txt')
p = p.with_name(p.stem).with_suffix('.jpg')

How do I detect if I am in release or debug mode?

Build.IS_DEBUGGABLE could be all right. It comes from "ro.debuggable"

Detect when browser receives file download

One possible solution uses JavaScript on the client.

The client algorithm:

  1. Generate a random unique token.
  2. Submit the download request, and include the token in a GET/POST field.
  3. Show the "waiting" indicator.
  4. Start a timer, and every second or so, look for a cookie named "fileDownloadToken" (or whatever you decide).
  5. If the cookie exists, and its value matches the token, hide the "waiting" indicator.

The server algorithm:

  1. Look for the GET/POST field in the request.
  2. If it has a non-empty value, drop a cookie (e.g. "fileDownloadToken"), and set its value to the token's value.

Client source code (JavaScript):

function getCookie( name ) {
  var parts = document.cookie.split(name + "=");
  if (parts.length == 2) return parts.pop().split(";").shift();
}

function expireCookie( cName ) {
    document.cookie = 
        encodeURIComponent(cName) + "=deleted; expires=" + new Date( 0 ).toUTCString();
}

function setCursor( docStyle, buttonStyle ) {
    document.getElementById( "doc" ).style.cursor = docStyle;
    document.getElementById( "button-id" ).style.cursor = buttonStyle;
}

function setFormToken() {
    var downloadToken = new Date().getTime();
    document.getElementById( "downloadToken" ).value = downloadToken;
    return downloadToken;
}

var downloadTimer;
var attempts = 30;

// Prevents double-submits by waiting for a cookie from the server.
function blockResubmit() {
    var downloadToken = setFormToken();
    setCursor( "wait", "wait" );

    downloadTimer = window.setInterval( function() {
        var token = getCookie( "downloadToken" );

        if( (token == downloadToken) || (attempts == 0) ) {
            unblockSubmit();
        }

        attempts--;
    }, 1000 );
}

function unblockSubmit() {
  setCursor( "auto", "pointer" );
  window.clearInterval( downloadTimer );
  expireCookie( "downloadToken" );
  attempts = 30;
}

Example server code (PHP):

$TOKEN = "downloadToken";

// Sets a cookie so that when the download begins the browser can
// unblock the submit button (thus helping to prevent multiple clicks).
// The false parameter allows the cookie to be exposed to JavaScript.
$this->setCookieToken( $TOKEN, $_GET[ $TOKEN ], false );

$result = $this->sendFile();

Where:

public function setCookieToken(
    $cookieName, $cookieValue, $httpOnly = true, $secure = false ) {

    // See: http://stackoverflow.com/a/1459794/59087
    // See: http://shiflett.org/blog/2006/mar/server-name-versus-http-host
    // See: http://stackoverflow.com/a/3290474/59087
    setcookie(
        $cookieName,
        $cookieValue,
        2147483647,            // expires January 1, 2038
        "/",                   // your path
        $_SERVER["HTTP_HOST"], // your domain
        $secure,               // Use true over HTTPS
        $httpOnly              // Set true for $AUTH_COOKIE_NAME
    );
}

Failed to resolve: com.android.support:appcompat-v7:28.0

Ensure that your buildToolsVersion version tallies with your app compact version.

In order to find both installed compileSdkVersion and buildToolsVersion go to Tools > SDK Manager. This will pull up a window that will allow you to manage your compileSdkVersion and your buildToolsVersion.

To see the exact version breakdowns ensure you have the Show Package Details checkbox checked.

android {
    compileSdkVersion 28
    buildToolsVersion "28.0.3" (HERE)
    defaultConfig {
        applicationId "com.example.truecitizenquiz"
        minSdkVersion 14
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0' (HERE)
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

How to add some non-standard font to a website?

See the article 50 Useful Design Tools For Beautiful Web Typography for alternative methods.

I have only used Cufon. I have found it reliable and very easy to use, so I've stuck with it.

MySQL Stored procedure variables from SELECT statements

Corrected a few things and added an alternative select - delete as appropriate.

DELIMITER |

CREATE PROCEDURE getNearestCities
(
IN p_cityID INT -- should this be int unsigned ?
)
BEGIN

DECLARE cityLat FLOAT; -- should these be decimals ?
DECLARE cityLng FLOAT;

    -- method 1
    SELECT lat,lng into cityLat, cityLng FROM cities WHERE cities.cityID = p_cityID;

    SELECT 
     b.*, 
     HAVERSINE(cityLat,cityLng, b.lat, b.lng) AS dist 
    FROM 
     cities b 
    ORDER BY 
     dist 
    LIMIT 10;

    -- method 2
    SELECT   
      b.*, 
      HAVERSINE(a.lat, a.lng, b.lat, b.lng) AS dist
    FROM     
      cities AS a
    JOIN cities AS b on a.cityID = p_cityID
    ORDER BY 
      dist
    LIMIT 10;

END |

delimiter ;

How to sort a list/tuple of lists/tuples by the element at a given index?

sorted_by_second = sorted(data, key=lambda tup: tup[1])

or:

data.sort(key=lambda tup: tup[1])  # sorts in place

Set Label Text with JQuery

You can try:

<label id ="label_id"></label>
 $("#label_id").html('value');

Is it possible to make a Tree View with Angular?

Not complicated.

<div ng-app="Application" ng-controller="TreeController">
    <table>
        <thead>
            <tr>
                <th>col 1</th>
                <th>col 2</th>
                <th>col 3</th>
            </tr>
        </thead>
        <tbody ng-repeat="item in tree">
            <tr>
                <td>{{item.id}}</td>
                <td>{{item.fname}}</td>
                <td>{{item.lname}}</td>
            </tr>
            <tr ng-repeat="children in item.child">
                <td style="padding-left:15px;">{{children.id}}</td>
                <td>{{children.fname}}</td>
            </tr>
        </tbody>
     </table>
</div>

controller code:

angular.module("myApp", []).
controller("TreeController", ['$scope', function ($scope) {
    $scope.tree = [{
        id: 1,
        fname: "tree",
        child: [{
            id: 1,
            fname: "example"
        }],
        lname: "grid"
    }];


}]);

Text not wrapping inside a div element

The problem in the jsfiddle is that your dummy text is all one word. If you use your lorem ipsum given in the question, then the text wraps fine.

If you want large words to be broken mid-word and wrap around, add this to your .title css:

word-wrap: break-word;

Change EditText hint color when using TextInputLayout

A lot answers but need only a line for this:

android:textColorHint="#000000"

    <EditText
        android:id="@+id/edtEmail"
        android:textColorHint="#000000"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

Why does CSV file contain a blank line in between each data line when outputting with Dictwriter in Python

Changing the 'w' (write) in this line:

output = csv.DictWriter(open('file3.csv','w'), delimiter=',', fieldnames=headers)

To 'wb' (write binary) fixed this problem for me:

output = csv.DictWriter(open('file3.csv','wb'), delimiter=',', fieldnames=headers)

Python v2.75: Open()

Credit to @dandrejvv for the solution in the comment on the original post above.

PHP - regex to allow letters and numbers only

  • Missing end anchor $
  • Missing multiplier
  • Missing end delimiter

So it should fail anyway, but if it may work, it matches against just one digit at the beginning of the string.

/^[a-z0-9]+$/i

Looping through GridView rows and Checking Checkbox Control

Loop like

foreach (GridViewRow row in grid.Rows)
{
   if (((CheckBox)row.FindControl("chkboxid")).Checked)
   {
    //read the label            
   }            
}

Regular expression to extract text between square brackets

If someone wants to match and select a string containing one or more dots inside square brackets like "[fu.bar]" use the following:

(?<=\[)(\w+\.\w+.*?)(?=\])

Regex Tester

Angular ui-grid dynamically calculate height of the grid

tony's approach does work for me but when do a console.log, the function getTableHeight get called too many time(sort, menu click...)

I modify it so the height is recalculated only when i add/remove rows. Note: tableData is the array of rows

$scope.getTableHeight = function() {
   var rowHeight = 30; // your row height
   var headerHeight = 30; // your header height
   return {
      height: ($scope.gridData.data.length * rowHeight + headerHeight) + "px"
   };
};

$scope.$watchCollection('tableData', function (newValue, oldValue) {
    angular.element(element[0].querySelector('.grid')).css($scope.getTableHeight());
});

Html

<div id="grid1" ui-grid="gridData" class="grid" ui-grid-auto-resize"></div>

<script> tag vs <script type = 'text/javascript'> tag

Douglas Crockford says:

type="text/javascript"

This attribute is optional. Since Netscape 2, the default programming language in all browsers has been JavaScript. In XHTML, this attribute is required and unnecessary. In HTML, it is better to leave it out. The browser knows what to do.

In HTML 4.01 and XHTML 1(.1), the type attribute for <script> elements is required.

Php - testing if a radio button is selected and get the value

<?php
if (isset($_POST['submit']) and ! empty($_POST['submit'])) {
    if (isset($_POST['radio'])) {
        $radio_input = $_POST['radio'];
        echo $radio_input;
    }
} else {

}
?>
<form action="radio.php" method="post">
   <input type="radio" name="radio" value="v1"/>
   <input type="radio" name="radio" value="v2"/>
   <input type="radio" name="radio" value="v3"/>
   <input type="radio" name="radio" value="v4"/>
   <input type="radio" name="radio" value="v5"/>
   <input type= "submit" name="submit"value="submit"/>
</form>

Sort a list of tuples by 2nd item (integer value)

For a lambda-avoiding method, first define your own function:

def MyFn(a):
    return a[1]

then:

sorted([('abc', 121),('abc', 231),('abc', 148), ('abc',221)], key=MyFn)

How to enable CORS in AngularJs

we can enable CORS in the frontend by using the ngResourse module. But most importantly, we should have this piece of code while making the ajax request in the controller,

$scope.weatherAPI = $resource(YOUR API,
     {callback: "JSON_CALLBACK"}, {get: {method: 'JSONP'}});
 $scope.weatherResult = $scope.weatherAPI.get(YOUR REQUEST DATA, if any);

Also, you must add ngResourse CDN in the script part and add as a dependency in the app module.

<script src="https://code.angularjs.org/1.2.16/angular-resource.js"></script>

Then use "ngResourse" in the app module dependency section

var routerApp = angular.module("routerApp", ["ui.router", 'ngResource']);

Difference between "@id/" and "@+id/" in Android

you refer to Android resources , which are already defined in Android system, with @android:id/.. while to access resources that you have defined/created in your project, you use @id/..

More Info

As per your clarifications in the chat, you said you have a problem like this :

If we use android:id="@id/layout_item_id" it doesn't work. Instead @+id/ works so what's the difference here? And that was my original question.

Well, it depends on the context, when you're using the XML attribute of android:id, then you're specifying a new id, and are instructing the parser (or call it the builder) to create a new entry in R.java, thus you have to include a + sign.

While in the other case, like android:layout_below="@id/myTextView" , you're referring to an id that has already been created, so parser links this to the already created id in R.java.

More Info Again

As you said in your chat, note that android:layout_below="@id/myTextView" won't recognize an element with id myTextViewif it is written after the element you're using it in.

Open popup and refresh parent page on close popup

You can access parent window using 'window.opener', so, write something like the following in the child window:

<script>
    window.onunload = refreshParent;
    function refreshParent() {
        window.opener.location.reload();
    }
</script>

Is it possible to run selenium (Firefox) web driver without a GUI?

Install & run containerized Firefox:

docker pull selenium/standalone-firefox
docker run --rm -d -p 4444:4444 --shm-size=2g selenium/standalone-firefox

Connect using webdriver.Remote:

driver = webdriver.Remote('http://localhost:4444/wd/hub', DesiredCapabilities.FIREFOX)
driver.set_window_size(1280, 1024)
driver.get('https://www.google.com')

System.BadImageFormatException An attempt was made to load a program with an incorrect format

i have same problem what i did i just downloaded 32-bit dll and added it to my bin folder this is solved my problem

How to generate different random numbers in a loop in C++?

Move the srand call to the start of the program. As you have it now, the time might be the same between two consecutive calls, so the random number generator will start again at the same spot.

How can I create a marquee effect?

Based on the previous reply, mainly @fcalderan, this marquee scrolls when hovered, with the advantage that the animation scrolls completely even if the text is shorter than the space within it scrolls, also any text length takes the same amount of time (this may be a pros or a cons) when not hovered the text return in the initial position.

No hardcoded value other than the scroll time, best suited for small scroll spaces

_x000D_
_x000D_
.marquee {_x000D_
    width: 100%;_x000D_
    margin: 0 auto;_x000D_
    white-space: nowrap;_x000D_
    overflow: hidden;_x000D_
    box-sizing: border-box;_x000D_
    display: inline-flex;    _x000D_
}_x000D_
_x000D_
.marquee span {_x000D_
    display: flex;        _x000D_
    flex-basis: 100%;_x000D_
    animation: marquee-reset;_x000D_
    animation-play-state: paused;                _x000D_
}_x000D_
_x000D_
.marquee:hover> span {_x000D_
    animation: marquee 2s linear infinite;_x000D_
    animation-play-state: running;_x000D_
}_x000D_
_x000D_
@keyframes marquee {_x000D_
    0% {_x000D_
        transform: translate(0%, 0);_x000D_
    }    _x000D_
    50% {_x000D_
        transform: translate(-100%, 0);_x000D_
    }_x000D_
    50.001% {_x000D_
        transform: translate(100%, 0);_x000D_
    }_x000D_
    100% {_x000D_
        transform: translate(0%, 0);_x000D_
    }_x000D_
}_x000D_
@keyframes marquee-reset {_x000D_
    0% {_x000D_
        transform: translate(0%, 0);_x000D_
    }  _x000D_
}
_x000D_
<span class="marquee">_x000D_
    <span>This is the marquee text</span>_x000D_
</span>
_x000D_
_x000D_
_x000D_

How to identify object types in java

You forgot the .class:

if (value.getClass() == Integer.class) {
    System.out.println("This is an Integer");
} 
else if (value.getClass() == String.class) {
    System.out.println("This is a String");
}
else if (value.getClass() == Float.class) {
    System.out.println("This is a Float");
}

Note that this kind of code is usually the sign of a poor OO design.

Also note that comparing the class of an object with a class and using instanceof is not the same thing. For example:

"foo".getClass() == Object.class

is false, whereas

"foo" instanceof Object

is true.

Whether one or the other must be used depends on your requirements.

How to undo "git commit --amend" done instead of "git commit"

None of these answers with the use of HEAD@{1} worked out for me, so here's my solution:

git reflog

d0c9f22 HEAD@{0}: commit (amend): [Feature] - ABC Commit Description 
c296452 HEAD@{1}: commit: [Feature] - ABC Commit Description 

git reset --soft c296452

Your staging environment will now contain all of the changes that you accidentally merged with the c296452 commit.

How to get line count of a large file cheaply in Python?

This is a meta-comment on some of the other answers.

  • The line-reading and buffered \n-counting techniques won't return the same answer for every file, because some text files have no newline at the end of the last line. You can work around this by checking the last byte of the last nonempty buffer and adding 1 if it's not b'\n'.

  • In Python 3, opening the file in text mode and in binary mode can yield different results, because text mode by default recognizes CR, LF, and CRLF as line endings (converting them all to '\n'), while in binary mode only LF and CRLF will be counted if you count b'\n'. This applies whether you read by lines or into a fixed-size buffer. The classic Mac OS used CR as a line ending; I don't know how common those files are these days.

  • The buffer-reading approach uses a bounded amount of RAM independent of file size, while the line-reading approach could read the entire file into RAM at once in the worst case (especially if the file uses CR line endings). In the worst case it may use substantially more RAM than the file size, because of overhead from dynamic resizing of the line buffer and (if you opened in text mode) Unicode decoding and storage.

  • You can improve the memory usage, and probably the speed, of the buffered approach by pre-allocating a bytearray and using readinto instead of read. One of the existing answers (with few votes) does this, but it's buggy (it double-counts some bytes).

  • The top buffer-reading answer uses a large buffer (1 MiB). Using a smaller buffer can actually be faster because of OS readahead. If you read 32K or 64K at a time, the OS will probably start reading the next 32K/64K into the cache before you ask for it, and each trip to the kernel will return almost immediately. If you read 1 MiB at a time, the OS is unlikely to speculatively read a whole megabyte. It may preread a smaller amount but you will still spend a significant amount of time sitting in the kernel waiting for the disk to return the rest of the data.

Move branch pointer to different commit without checkout

The recommended solution git branch -f branch-pointer-to-move new-pointer in TortoiseGit:

  • "Git Show log"
  • Check "All Branches"
  • On the line you want the branch pointer to move to (new-pointer):
    • Right click, "Create Branch at this version"
    • Beside "Branch", enter the name of the branch to move (branch-pointer-to-move)
    • Under "Base On", check that the new pointer is correct
    • Check "Force"
    • Ok

enter image description here

enter image description here

JavaScript backslash (\) in variables is causing an error

The jsfiddle link to where i tried out your query http://jsfiddle.net/A8Dnv/1/ its working fine @Imrul as mentioned you are using C# on server side and you dont mind that either: http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex.escape.aspx

How do you do relative time in Rails?

Something like this would work.

def relative_time(start_time)
  diff_seconds = Time.now - start_time
  case diff_seconds
    when 0 .. 59
      puts "#{diff_seconds} seconds ago"
    when 60 .. (3600-1)
      puts "#{diff_seconds/60} minutes ago"
    when 3600 .. (3600*24-1)
      puts "#{diff_seconds/3600} hours ago"
    when (3600*24) .. (3600*24*30) 
      puts "#{diff_seconds/(3600*24)} days ago"
    else
      puts start_time.strftime("%m/%d/%Y")
  end
end

JavaScript private methods

If you want the full range of public and private functions with the ability for public functions to access private functions, layout code for an object like this:

function MyObject(arg1, arg2, ...) {
  //constructor code using constructor arguments...
  //create/access public variables as 
  // this.var1 = foo;

  //private variables

  var v1;
  var v2;

  //private functions
  function privateOne() {
  }

  function privateTwon() {
  }

  //public functions

  MyObject.prototype.publicOne = function () {
  };

  MyObject.prototype.publicTwo = function () {
  };
}

How to restore the dump into your running mongodb

I have been through a lot of trouble so I came up with my own solution, I created this script, just set the path inside script and db name and run it, it will do the trick

#!/bin/bash

FILES= #absolute or relative path to dump directory
DB=`db` #db name
for file in $FILES
do

    name=$(basename $file)
    collection="${name%.*}"
    echo `mongoimport --db "$DB" --file "$name" --collection "$collection"`

done

Less than or equal to

There is no => for if.
Use if %energy% GEQ %m2enc%

See if /? for some other details.

How to get first character of string?

var str="stack overflow";

firstChar  = str.charAt(0);

secondChar = str.charAt(1);

Tested in IE6+, FF, Chrome, safari.

Size of character ('a') in C/C++

In C language, character literal is not a char type. C considers character literal as integer. So, there is no difference between sizeof('a') and sizeof(1).

So, the sizeof character literal is equal to sizeof integer in C.

In C++ language, character literal is type of char. The cppreference say's:

1) narrow character literal or ordinary character literal, e.g. 'a' or '\n' or '\13'. Such literal has type char and the value equal to the representation of c-char in the execution character set. If c-char is not representable as a single byte in the execution character set, the literal has type int and implementation-defined value.

So, in C++ character literal is a type of char. so, size of character literal in C++ is one byte.

Alos, In your programs, you have used wrong format specifier for sizeof operator.

C11 §7.21.6.1 (P9) :

If a conversion specification is invalid, the behavior is undefined.275) If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined.

So, you should use %zu format specifier instead of %d, otherwise it is undefined behaviour in C.

Error using eclipse for Android - No resource found that matches the given name

Accidentally moved the "values" folder outside of the "res" folder. Moved it back and it fired up!

Trying to get property of non-object - CodeIgniter

To get the value:

$query = $this->db->query("YOUR QUERY");

Then, for single row from(in controller):

$query1 = $query->row();
$data['product'] = $query1;

In view, you can use your own code (above code)

Adding a new entry to the PATH variable in ZSH

Here, add this line to .zshrc:

export PATH=/home/david/pear/bin:$PATH

EDIT: This does work, but ony's answer below is better, as it takes advantage of the structured interface ZSH provides for variables like $PATH. This approach is standard for bash, but as far as I know, there is no reason to use it when ZSH provides better alternatives.

bitwise XOR of hex numbers in python

here's a better function

def strxor(a, b):     # xor two strings of different lengths
    if len(a) > len(b):
        return "".join([chr(ord(x) ^ ord(y)) for (x, y) in zip(a[:len(b)], b)])
    else:
        return "".join([chr(ord(x) ^ ord(y)) for (x, y) in zip(a, b[:len(a)])])

Running MSBuild fails to read SDKToolsPath

One of your projects use sgen.exe (Server Generator) to generate web service. you need install SDKs to Build Server or remove Web Service references from the project.

ReactJS Two components communicating

Oddly nobody mentioned mobx. The idea is similar to redux. If I have a piece of data that multiple components are subscribed to it, then I can use this data to drive multiple components.

How does functools partial do what it does?

partials are incredibly useful.

For instance, in a 'pipe-lined' sequence of function calls (in which the returned value from one function is the argument passed to the next).

Sometimes a function in such a pipeline requires a single argument, but the function immediately upstream from it returns two values.

In this scenario, functools.partial might allow you to keep this function pipeline intact.

Here's a specific, isolated example: suppose you want to sort some data by each data point's distance from some target:

# create some data
import random as RND
fnx = lambda: RND.randint(0, 10)
data = [ (fnx(), fnx()) for c in range(10) ]
target = (2, 4)

import math
def euclid_dist(v1, v2):
    x1, y1 = v1
    x2, y2 = v2
    return math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

To sort this data by distance from the target, what you would like to do of course is this:

data.sort(key=euclid_dist)

but you can't--the sort method's key parameter only accepts functions that take a single argument.

so re-write euclid_dist as a function taking a single parameter:

from functools import partial

p_euclid_dist = partial(euclid_dist, target)

p_euclid_dist now accepts a single argument,

>>> p_euclid_dist((3, 3))
  1.4142135623730951

so now you can sort your data by passing in the partial function for the sort method's key argument:

data.sort(key=p_euclid_dist)

# verify that it works:
for p in data:
    print(round(p_euclid_dist(p), 3))

    1.0
    2.236
    2.236
    3.606
    4.243
    5.0
    5.831
    6.325
    7.071
    8.602

Or for instance, one of the function's arguments changes in an outer loop but is fixed during iteration in the inner loop. By using a partial, you don't have to pass in the additional parameter during iteration of the inner loop, because the modified (partial) function doesn't require it.

>>> from functools import partial

>>> def fnx(a, b, c):
      return a + b + c

>>> fnx(3, 4, 5)
      12

create a partial function (using keyword arg)

>>> pfnx = partial(fnx, a=12)

>>> pfnx(b=4, c=5)
     21

you can also create a partial function with a positional argument

>>> pfnx = partial(fnx, 12)

>>> pfnx(4, 5)
      21

but this will throw (e.g., creating partial with keyword argument then calling using positional arguments)

>>> pfnx = partial(fnx, a=12)

>>> pfnx(4, 5)
      Traceback (most recent call last):
      File "<pyshell#80>", line 1, in <module>
      pfnx(4, 5)
      TypeError: fnx() got multiple values for keyword argument 'a'

another use case: writing distributed code using python's multiprocessing library. A pool of processes is created using the Pool method:

>>> import multiprocessing as MP

>>> # create a process pool:
>>> ppool = MP.Pool()

Pool has a map method, but it only takes a single iterable, so if you need to pass in a function with a longer parameter list, re-define the function as a partial, to fix all but one:

>>> ppool.map(pfnx, [4, 6, 7, 8])

Calling a Variable from another Class

I would suggest to use a variable instead of a public field:

public class Variables
{
   private static string name = "";

   public static string Name
   { 
        get { return name; }
        set { name = value; }

   }
}

From another class, you call your variable like this:

public class Main
{
    public void DoSomething()
    {
         string var = Variables.Name;
    }
}

Getting "Cannot call a class as a function" in my React Project

Mostly these issues occur when you miss extending Component from react:

import React, {Component} from 'react'

export default class TimePicker extends Component {
    render() {
        return();     
    }
}

The type initializer for 'CrystalDecisions.CrystalReports.Engine.ReportDocument' threw an exception

if you are using visual studio , enable the build property "Prefer 32-bit". see image below.

enter image description here

How to show image using ImageView in Android

shoud be @drawable/image where image could have any extension like: image.png, image.xml, image.gif. Android will automatically create a reference in R class with its name, so you cannot have in any drawable folder image.png and image.gif.

How to re-render flatlist?

I have replaced FlatList with SectionList and it is updates properly on state change.

<SectionList
  keyExtractor={(item) => item.entry.entryId} 
  sections={section}
  renderItem={this.renderEntries.bind(this)}
  renderSectionHeader={() => null}
/>

The only thing need to keep in mind is that section have diff structure:

const section = [{
  id: 0,
  data: this.state.data,
}]

Quicksort with Python

The algorithm contains two boundaries, one having elements less than the pivot (tracked by index "j") and the other having elements greater than the pivot (tracked by index "i").

In each iteration, a new element is processed by incrementing j.

Invariant:-

  1. all elements between pivot and i are less than the pivot, and
  2. all elements between i and j are greater than the pivot.

If the invariant is violated, ith and jth elements are swapped, and i is incremented.

After all elements have been processed, and everything after the pivot has been partitioned, the pivot element is swapped with the last element smaller than it.

The pivot element will now be in its correct place in the sequence. The elements before it will be less than it and the ones after it will be greater than it, and they will be unsorted.

def quicksort(sequence, low, high):
    if low < high:    
        pivot = partition(sequence, low, high)
        quicksort(sequence, low, pivot - 1)
        quicksort(sequence, pivot + 1, high)

def partition(sequence, low, high):
    pivot = sequence[low]
    i = low + 1
    for j in range(low + 1, high + 1):
        if sequence[j] < pivot:
            sequence[j], sequence[i] = sequence[i], sequence[j]
            i += 1
    sequence[i-1], sequence[low] = sequence[low], sequence[i-1]
    return i - 1

def main(sequence):
    quicksort(sequence, 0, len(sequence) - 1)
    return sequence

if __name__ == '__main__':
    sequence = [-2, 0, 32, 1, 56, 99, -4]
    print(main(sequence))

Selecting a pivot

A "good" pivot will result in two sub-sequences of roughly the same size. Deterministically, a pivot element can either be selected in a naive manner or by computing the median of the sequence.

A naive implementation of selecting a pivot will be the first or last element. The worst-case runtime in this case will be when the input sequence is already sorted or reverse sorted, as one of the subsequences will be empty which will cause only one element to be removed per recursive call.

A perfectly balanced split is achieved when the pivot is the median element of the sequence. There are an equal number of elements greater than it and less than it. This approach guarantees a better overall running time, but is much more time-consuming.

A non-deterministic/random way of selecting the pivot would be to pick an element uniformly at random. This is a simple and lightweight approach that will minimize worst-case scenario and also lead to a roughly balanced split. This will also provide a balance between the naive approach and the median approach of selecting the pivot.

function to remove duplicate characters in a string

I understand that this is a Java question, but since I have a nice solution which could inspire someone to convert this into Java, by all means. Also I like answers where multiple language submissions are available to common problems.

So here is a Python solution which is O(n) and also supports the whole ASCII range. Of course it does not treat 'a' and 'A' as the same:

I am using 8 x 32 bits as the hashmap:

Also input is a string array using dedup(list('some string'))

def dedup(str):
    map = [0,0,0,0,0,0,0,0]
    for i in range(len(str)):
        ascii = ord(str[i])
        slot = ascii / 32
        bit = ascii % 32
        bitOn = map[slot] & (1 << bit)
        if bitOn:
            str[i] = ''
        else:
            map[slot] |= 1 << bit

    return ''.join(str)

also a more pythonian way to do this is by using a set:

def dedup(s):
    return ''.join(list(set(s)))

JPA Query selecting only specific columns without using Criteria Query?

I suppose you could look at this link if I understood your question correctly http://www.javacodegeeks.com/2012/07/ultimate-jpa-queries-and-tips-list-part_09.html

For example they created a query like:

 select id, name, age, a.id as ADDRESS_ID, houseNumber, streetName ' +
 20' from person p join address a on a.id = p.address_id where p.id = 1'

Executing multiple SQL queries in one statement with PHP

Pass 65536 to mysql_connect as 5th parameter.

Example:

$conn = mysql_connect('localhost','username','password', true, 65536 /* here! */) 
    or die("cannot connect");
mysql_select_db('database_name') or die("cannot use database");
mysql_query("
    INSERT INTO table1 (field1,field2) VALUES(1,2);

    INSERT INTO table2 (field3,field4,field5) VALUES(3,4,5);

    DELETE FROM table3 WHERE field6 = 6;

    UPDATE table4 SET field7 = 7 WHERE field8 = 8;

    INSERT INTO table5
       SELECT t6.field11, t6.field12, t7.field13
       FROM table6 t6
       INNER JOIN table7 t7 ON t7.field9 = t6.field10;

    -- etc
");

When you are working with mysql_fetch_* or mysql_num_rows, or mysql_affected_rows, only the first statement is valid.

For example, the following codes, the first statement is INSERT, you cannot execute mysql_num_rows and mysql_fetch_*. It is okay to use mysql_affected_rows to return how many rows inserted.

$conn = mysql_connect('localhost','username','password', true, 65536) or die("cannot connect");
mysql_select_db('database_name') or die("cannot use database");
mysql_query("
    INSERT INTO table1 (field1,field2) VALUES(1,2);
    SELECT * FROM table2;
");

Another example, the following codes, the first statement is SELECT, you cannot execute mysql_affected_rows. But you can execute mysql_fetch_assoc to get a key-value pair of row resulted from the first SELECT statement, or you can execute mysql_num_rows to get number of rows based on the first SELECT statement.

$conn = mysql_connect('localhost','username','password', true, 65536) or die("cannot connect");
mysql_select_db('database_name') or die("cannot use database");
mysql_query("
    SELECT * FROM table2;
    INSERT INTO table1 (field1,field2) VALUES(1,2);
");

How do you get centered content using Twitter Bootstrap?

If you use Bootstrap 3, it also has built-in CSS class named .text-center. That's what you want.

<div class="text-left">
    left
</div>

<div class="text-center">
    center
</div>

<div class="text-right">
    right
</div>

Please see the example in jsfiddle. http://jsfiddle.net/ucheng/Q4Fue/

How do I query using fields inside the new PostgreSQL JSON datatype?

With Postgres 9.3+, just use the -> operator. For example,

SELECT data->'images'->'thumbnail'->'url' AS thumb FROM instagram;

see http://clarkdave.net/2013/06/what-can-you-do-with-postgresql-and-json/ for some nice examples and a tutorial.

401 Unauthorized: Access is denied due to invalid credentials

I had a similar issue today. For some reason, my GET request was fine, but PUT request was failing for my WCF WebHttp Service

Adding the following to the Web.config solved the issue

 <system.web>
  <authentication mode="Forms" />
 </system.web>

How to change indentation in Visual Studio Code?

Setting the indentation in preferences isn't allways the solution. Most of the time the indentation is right except you happen to copy some code code from other sources or your collegue make something for you and has different settings. Then you want to just quickly convert the indentation from 2 to 4 or the other way round.

That's what this vscode extension is doing for you

enter image description here

Check if a string contains another string

There is also the InStrRev function which does the same type of thing, but starts searching from the end of the text to the beginning.

Per @rene's answer...

Dim pos As Integer
pos = InStrRev("find the comma, in the string", ",")

...would still return 15 to pos, but if the string has more than one of the search string, like the word "the", then:

Dim pos As Integer
pos = InStrRev("find the comma, in the string", "the")

...would return 20 to pos, instead of 6.

jQuery position DIV fixed at top on scroll

instead of doing it like that, why not just make the flyout position:fixed, top:0; left:0; once your window has scrolled pass a certain height:

jQuery

  $(window).scroll(function(){
      if ($(this).scrollTop() > 135) {
          $('#task_flyout').addClass('fixed');
      } else {
          $('#task_flyout').removeClass('fixed');
      }
  });

css

.fixed {position:fixed; top:0; left:0;}

Example

break out of if and foreach

foreach($equipxml as $equip) {
    $current_device = $equip->xpath("name");
    if ( $current_device[0] == $device ) {
        // found a match in the file            
        $nodeid = $equip->id;
        break;
    }
}

Simply use break. That will do it.

BACKUP LOG cannot be performed because there is no current database backup

You can use following SQL to restore if you've already created database

RESTORE DATABASE [YourDB]
FROM DISK = 'C:\YourDB.bak'
WITH MOVE 'YourDB' TO 'C:\YourDB.mdf',
MOVE 'YourDB_Log' TO 'C:\YourDB.ldf', REPLACE

Which characters make a URL invalid?

I came up with a couple regular expressions for PHP that will convert urls in text to anchor tags. (First it converts all www. urls to http:// then converts all urls with https?:// to a href=... html links

$string = preg_replace('/(https?:\/\/)([!#$&-;=?\-\[\]_a-z~%]+)/sim', '<a href="$1$2">$2</a>', preg_replace('/(\s)((www\.)([!#$&-;=?\-\[\]_a-z~%]+))/sim', '$1http://$2', $string) );

How can I disable ARC for a single file in a project?

use -fno-objc-arc for each file in build phases

Spring Boot, Spring Data JPA with multiple DataSources

There is another way to have multiple dataSources by using @EnableAutoConfiguration and application.properties.

Basically put multiple dataSource configuration info on application.properties and generate default setup (dataSource and entityManagerFactory) automatically for first dataSource by @EnableAutoConfiguration. But for next dataSource, create dataSource, entityManagerFactory and transactionManager all manually by the info from property file.

Below is my example to setup two dataSources. First dataSource is setup by @EnableAutoConfiguration which can be assigned only for one configuration, not multiple. And that will generate 'transactionManager' by DataSourceTransactionManager, that looks default transactionManager generated by the annotation. However I have seen the transaction not beginning issue on the thread from scheduled thread pool only for the default DataSourceTransactionManager and also when there are multiple transaction managers. So I create transactionManager manually by JpaTransactionManager also for the first dataSource with assigning 'transactionManager' bean name and default entityManagerFactory. That JpaTransactionManager for first dataSource surely resolves the weird transaction issue on the thread from ScheduledThreadPool.

Update for Spring Boot 1.3.0.RELEASE

I found my previous configuration with @EnableAutoConfiguration for default dataSource has issue on finding entityManagerFactory with Spring Boot 1.3 version. Maybe default entityManagerFactory is not generated by @EnableAutoConfiguration, once after I introduce my own transactionManager. So now I create entityManagerFactory by myself. So I don't need to use @EntityScan. So it looks I'm getting more and more out of the setup by @EnableAutoConfiguration.

Second dataSource is setup without @EnableAutoConfiguration and create 'anotherTransactionManager' by manual way.

Since there are multiple transactionManager extends from PlatformTransactionManager, we should specify which transactionManager to use on each @Transactional annotation

Default Repository Config

@Configuration
@EnableTransactionManagement
@EnableAutoConfiguration
@EnableJpaRepositories(
        entityManagerFactoryRef = "entityManagerFactory",
        transactionManagerRef = "transactionManager",
        basePackages = {"com.mysource.repository"})
public class RepositoryConfig {
    @Autowired
    JpaVendorAdapter jpaVendorAdapter;

    @Autowired
    DataSource dataSource;

    @Bean(name = "entityManager")
    public EntityManager entityManager() {
        return entityManagerFactory().createEntityManager();
    }

    @Primary
    @Bean(name = "entityManagerFactory")
    public EntityManagerFactory entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean emf = new LocalContainerEntityManagerFactoryBean();
        emf.setDataSource(dataSource);
        emf.setJpaVendorAdapter(jpaVendorAdapter);
        emf.setPackagesToScan("com.mysource.model");
        emf.setPersistenceUnitName("default");   // <- giving 'default' as name
        emf.afterPropertiesSet();
        return emf.getObject();
    }

    @Bean(name = "transactionManager")
    public PlatformTransactionManager transactionManager() {
        JpaTransactionManager tm = new JpaTransactionManager();
        tm.setEntityManagerFactory(entityManagerFactory());
        return tm;
    }
}

Another Repository Config

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef = "anotherEntityManagerFactory",
        transactionManagerRef = "anotherTransactionManager",
        basePackages = {"com.mysource.anothersource.repository"})
public class AnotherRepositoryConfig {
    @Autowired
    JpaVendorAdapter jpaVendorAdapter;

    @Value("${another.datasource.url}")
    private String databaseUrl;

    @Value("${another.datasource.username}")
    private String username;

    @Value("${another.datasource.password}")
    private String password;

    @Value("${another.dataource.driverClassName}")
    private String driverClassName;

    @Value("${another.datasource.hibernate.dialect}")
    private String dialect;

    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource(databaseUrl, username, password);
        dataSource.setDriverClassName(driverClassName);
        return dataSource;
    }

    @Bean(name = "anotherEntityManager")
    public EntityManager entityManager() {
        return entityManagerFactory().createEntityManager();
    }

    @Bean(name = "anotherEntityManagerFactory")
    public EntityManagerFactory entityManagerFactory() {
        Properties properties = new Properties();
        properties.setProperty("hibernate.dialect", dialect);

        LocalContainerEntityManagerFactoryBean emf = new LocalContainerEntityManagerFactoryBean();
        emf.setDataSource(dataSource());
        emf.setJpaVendorAdapter(jpaVendorAdapter);
        emf.setPackagesToScan("com.mysource.anothersource.model");   // <- package for entities
        emf.setPersistenceUnitName("anotherPersistenceUnit");
        emf.setJpaProperties(properties);
        emf.afterPropertiesSet();
        return emf.getObject();
    }

    @Bean(name = "anotherTransactionManager")
    public PlatformTransactionManager transactionManager() {
        return new JpaTransactionManager(entityManagerFactory());
    }
}

application.properties

# database configuration
spring.datasource.url=jdbc:h2:file:~/main-source;AUTO_SERVER=TRUE
spring.datasource.username=sa
spring.datasource.password=
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.continueOnError=true
spring.datasource.initialize=false

# another database configuration
another.datasource.url=jdbc:sqlserver://localhost:1433;DatabaseName=another;
another.datasource.username=username
another.datasource.password=
another.datasource.hibernate.dialect=org.hibernate.dialect.SQLServer2008Dialect 
another.datasource.driverClassName=com.microsoft.sqlserver.jdbc.SQLServerDriver

Choose proper transactionManager for @Transactional annotation

Service for first datasource

@Service("mainService")
@Transactional("transactionManager")
public class DefaultDataSourceServiceImpl implements DefaultDataSourceService       
{

   //

}

Service for another datasource

@Service("anotherService")
@Transactional("anotherTransactionManager")
public class AnotherDataSourceServiceImpl implements AnotherDataSourceService 
{

   //

}

How to ping multiple servers and return IP address and Hostnames using batch script?

Try this

$servers = Get-Content test.txt

$reg=""

foreach ($server in $servers) 

{

$reg=$reg+$server+"`t"+([System.Net.Dns]::GetHostAddresses($server) | foreach {echo $_.IPAddressToString})+"`n"

 }
$reg >reg.csv

Error while retrieving information from the server RPC:s-7:AEC-0 in Google play?

The same problem Error while retrieving information from server. [RPC:S-5:AEC-0] was resolved after these steps:

  1. Change password of your Google account via web.
  2. Wait for a Sign-in error notification on your device.
  3. Type new password and problem should disappeared.

Actually, this helps me.

length and length() in Java

.length is a one-off property of Java. It's used to find the size of a single dimensional array.

.length() is a method. It's used to find the length of a String. It avoids duplicating the value.

How to fix System.NullReferenceException: Object reference not set to an instance of an object

During debug, break on all exceptions thrown. Debug->Exceptions

Check all 'Thrown' exceptions. F5, the code will stop on the offending line.

MySQL: how to get the difference between two timestamps in seconds

You could use the TIMEDIFF() and the TIME_TO_SEC() functions as follows:

SELECT TIME_TO_SEC(TIMEDIFF('2010-08-20 12:01:00', '2010-08-20 12:00:00')) diff;
+------+
| diff |
+------+
|   60 |
+------+
1 row in set (0.00 sec)

You could also use the UNIX_TIMESTAMP() function as @Amber suggested in an other answer:

SELECT UNIX_TIMESTAMP('2010-08-20 12:01:00') - 
       UNIX_TIMESTAMP('2010-08-20 12:00:00') diff;
+------+
| diff |
+------+
|   60 |
+------+
1 row in set (0.00 sec)

If you are using the TIMESTAMP data type, I guess that the UNIX_TIMESTAMP() solution would be slightly faster, since TIMESTAMP values are already stored as an integer representing the number of seconds since the epoch (Source). Quoting the docs:

When UNIX_TIMESTAMP() is used on a TIMESTAMP column, the function returns the internal timestamp value directly, with no implicit “string-to-Unix-timestamp” conversion.

Keep in mind that TIMEDIFF() return data type of TIME. TIME values may range from '-838:59:59' to '838:59:59' (roughly 34.96 days)

creating Hashmap from a JSON String

Best way to parse Json to HashMap

public static HashMap<String, String> jsonToMap(JSONObject json) throws JSONException {
            HashMap<String, String> map = new HashMap<>();
            try {
                Iterator<String> iterator = json.keys();

                while (iterator.hasNext()) {
                    String key = iterator.next();
                    String value = json.getString(key);
                    map.put(key, value);
                }

                return map;
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;
        }

How do I remove the old history from a git repository?

This method is easy to understand and works fine. The argument to the script ($1) is a reference (tag, hash, ...) to the commit starting from which you want to keep your history.

#!/bin/bash
git checkout --orphan temp $1 # create a new branch without parent history
git commit -m "Truncated history" # create a first commit on this branch
git rebase --onto temp $1 master # now rebase the part of master branch that we want to keep onto this branch
git branch -D temp # delete the temp branch

# The following 2 commands are optional - they keep your git repo in good shape.
git prune --progress # delete all the objects w/o references
git gc --aggressive # aggressively collect garbage; may take a lot of time on large repos

NOTE that old tags will still remain present; so you might need to remove them manually

remark: I know this is almost the same aswer as @yoyodin, but there are some important extra commands and informations here. I tried to edit the answer, but since it is a substantial change to @yoyodin's answer, my edit was rejected, so here's the information!

Download data url file

Ideas:

  • Try a <a href="data:...." target="_blank"> (Untested)

  • Use downloadify instead of data URLs (would work for IE as well)

how to measure running time of algorithms in python

The module timeit is useful for this and is included in the standard Python distribution.

Example:

import timeit
timeit.Timer('for i in xrange(10): oct(i)').timeit()

Centering a background image, using CSS

Try this background-position: center top;

This will do the trick for you.

while installing vc_redist.x64.exe, getting error "Failed to configure per-machine MSU package."

In my case and while installing VS 2015 on Windows7 64x SP1, I experienced the same so tried to cancel and download/install the KBKB2999226 separately and for some reason the standalone update installer also get stuck searching for updates.

enter image description here

Here what I did:

  1. When the VS installer stuck at the KB2999226 update I clicked cancel.
  2. Installer took me back to confirm cancellation, waited for a while then opened the windows task manager and ended the process of wuse.exe (windows standalone update installer)
  3. On the VS installer clicked "No" to return to installation process. The process was completed without errors.

Search for value in DataGridView in a column

Why you are using row.Cells[row.Index]. You need to specify index of column you want to search (Problem #2). For example, you need to change row.Cells[row.Index] to row.Cells[2] where 2 is index of your column:

private void btnSearch_Click(object sender, EventArgs e)
{
    string searchValue = textBox1.Text;

    dgvProjects.SelectionMode = DataGridViewSelectionMode.FullRowSelect;
    try
    {
        foreach (DataGridViewRow row in dgvProjects.Rows)
        {
            if (row.Cells[2].Value.ToString().Equals(searchValue))
            {
                row.Selected = true;
                break;
            }
        }
    }
    catch (Exception exc)
    {
        MessageBox.Show(exc.Message);
    }
}

How to delete an SMS from the inbox in Android programmatically?

Using suggestions from others, I think I got it to work:

(using SDK v1 R2)

It's not perfect, since i need to delete the entire conversation, but for our purposes, it's a sufficient compromise as we will at least know all messages will be looked at and verified. Our flow will probably need to then listen for the message, capture for the message we want, do a query to get the thread_id of the recently inbounded message and do the delete() call.

In our Activity:

Uri uriSms = Uri.parse("content://sms/inbox");
Cursor c = getContentResolver().query(uriSms, null,null,null,null); 
int id = c.getInt(0);
int thread_id = c.getInt(1); //get the thread_id
getContentResolver().delete(Uri.parse("content://sms/conversations/" + thread_id),null,null);

Note: I wasn't able to do a delete on content://sms/inbox/ or content://sms/all/

Looks like the thread takes precedence, which makes sense, but the error message only emboldened me to be angrier. When trying the delete on sms/inbox/ or sms/all/, you will probably get:

java.lang.IllegalArgumentException: Unknown URL
    at com.android.providers.telephony.SmsProvider.delete(SmsProvider.java:510)
    at android.content.ContentProvider$Transport.delete(ContentProvider.java:149)
    at android.content.ContentProviderNative.onTransact(ContentProviderNative.java:149)

For additional reference too, make sure to put this into your manifest for your intent receiver:

<receiver android:name=".intent.MySmsReceiver">
    <intent-filter>
        <action android:name="android.provider.Telephony.SMS_RECEIVED"></action>
    </intent-filter>
</receiver>

Note the receiver tag does not look like this:

<receiver android:name=".intent.MySmsReceiver" 
    android:permission="android.permission.RECEIVE_SMS">

When I had those settings, android gave me some crazy permissions exceptions that didn't allow android.phone to hand off the received SMS to my intent. So, DO NOT put that RECEIVE_SMS permission attribute in your intent! Hopefully someone wiser than me can tell me why that was the case.

PHP Unset Session Variable

unset is a function, not an operator. Use it like unset($_SESSION['key']); to unset that session key. You can, however, use session_destroy(); as well. (Make sure to start the session with session_start(); as well)

How to check "hasRole" in Java Code with Spring Security?

User Roles can be checked using following ways:

  1. Using call static methods in SecurityContextHolder:

    Authentication auth = SecurityContextHolder.getContext().getAuthentication(); if (auth != null && auth.getAuthorities().stream().anyMatch(role -> role.getAuthority().equals("ROLE_NAME"))) { //do something}

  2. Using HttpServletRequest

_x000D_
_x000D_
@GetMapping("/users")
public String getUsers(HttpServletRequest request) {
    if (request.isUserInRole("ROLE_NAME")) {
      
    }
_x000D_
_x000D_
_x000D_

"A referral was returned from the server" exception when accessing AD from C#

A referral was returned from the server error usually means that the IP address is not hosted by the domain that is provided on the connection string. For more detail, see this link:

Referral was returned AD Provider

To illustrate the problem, we define two IP addresses hosted on different domains:

IP Address DC Name Notes

172.1.1.10 ozkary.com Production domain

172.1.30.50 ozkaryDev.com Development domain

If we defined a LDAP connection string with this format:

LDAP://172.1.1.10:389/OU=USERS,DC=OZKARYDEV,DC=COM

This will generate the error because the IP is actually on the OZKARY DC not the OZKARYDEV DC. To correct the problem, we would need to use the IP address that is associated to the domain.

Cannot insert explicit value for identity column in table 'table' when IDENTITY_INSERT is set to OFF

I'm not sure what the use for the "Insert Table" is, but if you're just trying to insert some values try:

Insert Into [tablename] (OpDescription,FilterID)
values ('Hierachy Update',1);

I had the same error message come up, but I think this should work. The ID should auto-increment automatically as long as it's a primary key.

Recyclerview inside ScrollView not scrolling smoothly

You can use this way either :

Add this line to your recyclerView xml file :

android:nestedScrollingEnabled="false"

Or in java code :

RecyclerView.setNestedScrollingEnabled(false);

Hope this helped .

HttpServlet cannot be resolved to a type .... is this a bug in eclipse?

It happened for me also and the reason was selecting inappropriate combination of tomcat and Dynamic web module version while creating project in eclipse. I selected Tomcat v9.0 along with Dynamic web module version 3.1 and eclipse was not able to resolve the HttpServlet type. When used Tomcat 7.0 along with Dynamic web module version 7.0, eclipse was automatically able to resolve the HttpServlet type.

Related question Dynamic Web Module option in Eclipse

To check which version of tomcat should be used along with different versions of the Servlet and JSP specifications refer http://tomcat.apache.org/whichversion.html

Why doesn't Java offer operator overloading?

There are a lot of posts complaining about operator overloading.

I felt I had to clarify the "operator overloading" concepts, offering an alternative viewpoint on this concept.

#Code obfuscating?

This argument is a fallacy.

##Obfuscating is possible in all languages...

It is as easy to obfuscate code in C or Java through functions/methods as it is in C++ through operator overloads:

// C++
T operator + (const T & a, const T & b) // add ?
{
   T c ;
   c.value = a.value - b.value ; // subtract !!!
   return c ;
}

// Java
static T add (T a, T b) // add ?
{
   T c = new T() ;
   c.value = a.value - b.value ; // subtract !!!
   return c ;
}

/* C */
T add (T a, T b) /* add ? */
{
   T c ;
   c.value = a.value - b.value ; /* subtract !!! */
   return c ;
}

##...Even in Java's standard interfaces

For another example, let's see the Cloneable interface in Java:

You are supposed to clone the object implementing this interface. But you could lie. And create a different object. In fact, this interface is so weak you could return another type of object altogether, just for the fun of it:

class MySincereHandShake implements Cloneable
{
    public Object clone()
    {
       return new MyVengefulKickInYourHead() ;
    }
}

As the Cloneable interface can be abused/obfuscated, should it be banned on the same grounds C++ operator overloading is supposed to be?

We could overload the toString() method of a MyComplexNumber class to have it return the stringified hour of the day. Should the toString() overloading be banned, too? We could sabotage MyComplexNumber.equals to have it return a random value, modify the operands... etc. etc. etc..

In Java, as in C++, or whatever language, the programmer must respect a minimum of semantics when writing code. This means implementing a add function that adds, and Cloneable implementation method that clones, and a ++ operator than increments.

#What's obfuscating anyway?

Now that we know that code can be sabotaged even through the pristine Java methods, we can ask ourselves about the real use of operator overloading in C++?

##Clear and natural notation: methods vs. operator overloading?

We'll compare below, for different cases, the "same" code in Java and C++, to have an idea of which kind of coding style is clearer.

###Natural comparisons:

// C++ comparison for built-ins and user-defined types
bool    isEqual          = A == B ;
bool    isNotEqual       = A != B ;
bool    isLesser         = A <  B ;
bool    isLesserOrEqual  = A <= B ;

// Java comparison for user-defined types
boolean isEqual          = A.equals(B) ;
boolean isNotEqual       = ! A.equals(B) ;
boolean isLesser         = A.comparesTo(B) < 0 ;
boolean isLesserOrEqual  = A.comparesTo(B) <= 0 ;

Please note that A and B could be of any type in C++, as long as the operator overloads are provided. In Java, when A and B are not primitives, the code can become very confusing, even for primitive-like objects (BigInteger, etc.)...

###Natural array/container accessors and subscripting:

// C++ container accessors, more natural
value        = myArray[25] ;         // subscript operator
value        = myVector[25] ;        // subscript operator
value        = myString[25] ;        // subscript operator
value        = myMap["25"] ;         // subscript operator
myArray[25]  = value ;               // subscript operator
myVector[25] = value ;               // subscript operator
myString[25] = value ;               // subscript operator
myMap["25"]  = value ;               // subscript operator

// Java container accessors, each one has its special notation
value        = myArray[25] ;         // subscript operator
value        = myVector.get(25) ;    // method get
value        = myString.charAt(25) ; // method charAt
value        = myMap.get("25") ;     // method get
myArray[25]  = value ;               // subscript operator
myVector.set(25, value) ;            // method set
myMap.put("25", value) ;             // method put

In Java, we see that for each container to do the same thing (access its content through an index or identifier), we have a different way to do it, which is confusing.

In C++, each container uses the same way to access its content, thanks to operator overloading.

###Natural advanced types manipulation

The examples below use a Matrix object, found using the first links found on Google for "Java Matrix object" and "C++ Matrix object":

// C++ YMatrix matrix implementation on CodeProject
// http://www.codeproject.com/KB/architecture/ymatrix.aspx
// A, B, C, D, E, F are Matrix objects;
E =  A * (B / 2) ;
E += (A - B) * (C + D) ;
F =  E ;                  // deep copy of the matrix

// Java JAMA matrix implementation (seriously...)
// http://math.nist.gov/javanumerics/jama/doc/
// A, B, C, D, E, F are Matrix objects;
E = A.times(B.times(0.5)) ;
E.plusEquals(A.minus(B).times(C.plus(D))) ;
F = E.copy() ;            // deep copy of the matrix

And this is not limited to matrices. The BigInteger and BigDecimal classes of Java suffer from the same confusing verbosity, whereas their equivalents in C++ are as clear as built-in types.

###Natural iterators:

// C++ Random Access iterators
++it ;                  // move to the next item
--it ;                  // move to the previous item
it += 5 ;               // move to the next 5th item (random access)
value = *it ;           // gets the value of the current item
*it = 3.1415 ;          // sets the value 3.1415 to the current item
(*it).foo() ;           // call method foo() of the current item

// Java ListIterator<E> "bi-directional" iterators
value = it.next() ;     // move to the next item & return the value
value = it.previous() ; // move to the previous item & return the value
it.set(3.1415) ;        // sets the value 3.1415 to the current item

###Natural functors:

// C++ Functors
myFunctorObject("Hello World", 42) ;

// Java Functors ???
myFunctorObject.execute("Hello World", 42) ;

###Text concatenation:

// C++ stream handling (with the << operator)
                    stringStream   << "Hello " << 25 << " World" ;
                    fileStream     << "Hello " << 25 << " World" ;
                    outputStream   << "Hello " << 25 << " World" ;
                    networkStream  << "Hello " << 25 << " World" ;
anythingThatOverloadsShiftOperator << "Hello " << 25 << " World" ;

// Java concatenation
myStringBuffer.append("Hello ").append(25).append(" World") ;

Ok, in Java you can use MyString = "Hello " + 25 + " World" ; too... But, wait a second: This is operator overloading, isn't it? Isn't it cheating???

:-D

##Generic code?

The same generic code modifying operands should be usable both for built-ins/primitives (which have no interfaces in Java), standard objects (which could not have the right interface), and user-defined objects.

For example, calculating the average value of two values of arbitrary types:

// C++ primitive/advanced types
template<typename T>
T getAverage(const T & p_lhs, const T & p_rhs)
{
   return (p_lhs + p_rhs) / 2 ;
}

int     intValue     = getAverage(25, 42) ;
double  doubleValue  = getAverage(25.25, 42.42) ;
complex complexValue = getAverage(cA, cB) ; // cA, cB are complex
Matrix  matrixValue  = getAverage(mA, mB) ; // mA, mB are Matrix

// Java primitive/advanced types
// It won't really work in Java, even with generics. Sorry.

#Discussing operator overloading

Now that we have seen fair comparisons between C++ code using operator overloading, and the same code in Java, we can now discuss "operator overloading" as a concept.

##Operator overloading existed since before computers

Even outside of computer science, there is operator overloading: For example, in mathematics, operators like +, -, *, etc. are overloaded.

Indeed, the signification of +, -, *, etc. changes depending on the types of the operands (numerics, vectors, quantum wave functions, matrices, etc.).

Most of us, as part of our science courses, learned multiple significations for operators, depending on the types of the operands. Did we find them confusing, them?

##Operator overloading depends on its operands

This is the most important part of operator overloading: Like in mathematics, or in physics, the operation depends on its operands' types.

So, know the type of the operand, and you will know the effect of the operation.

##Even C and Java have (hard-coded) operator overloading

In C, the real behavior of an operator will change according to its operands. For example, adding two integers is different than adding two doubles, or even one integer and one double. There is even the whole pointer arithmetic domain (without casting, you can add to a pointer an integer, but you cannot add two pointers...).

In Java, there is no pointer arithmetic, but someone still found string concatenation without the + operator would be ridiculous enough to justify an exception in the "operator overloading is evil" creed.

It's just that you, as a C (for historical reasons) or Java (for personal reasons, see below) coder, you can't provide your own.

##In C++, operator overloading is not optional...

In C++, operator overloading for built-in types is not possible (and this is a good thing), but user-defined types can have user-defined operator overloads.

As already said earlier, in C++, and to the contrary to Java, user-types are not considered second-class citizens of the language, when compared to built-in types. So, if built-in types have operators, user types should be able to have them, too.

The truth is that, like the toString(), clone(), equals() methods are for Java (i.e. quasi-standard-like), C++ operator overloading is so much part of C++ that it becomes as natural as the original C operators, or the before mentioned Java methods.

Combined with template programming, operator overloading becomes a well known design pattern. In fact, you cannot go very far in STL without using overloaded operators, and overloading operators for your own class.

##...but it should not be abused

Operator overloading should strive to respect the semantics of the operator. Do not subtract in a + operator (as in "do not subtract in a add function", or "return crap in a clone method").

Cast overloading can be very dangerous because they can lead to ambiguities. So they should really be reserved for well defined cases. As for && and ||, do not ever overload them unless you really know what you're doing, as you'll lose the the short circuit evaluation that the native operators && and || enjoy.

#So... Ok... Then why it is not possible in Java?

Because James Gosling said so:

I left out operator overloading as a fairly personal choice because I had seen too many people abuse it in C++.

James Gosling. Source: http://www.gotw.ca/publications/c_family_interview.htm

Please compare Gosling's text above with Stroustrup's below:

Many C++ design decisions have their roots in my dislike for forcing people to do things in some particular way [...] Often, I was tempted to outlaw a feature I personally disliked, I refrained from doing so because I did not think I had the right to force my views on others.

Bjarne Stroustrup. Source: The Design and Evolution of C++ (1.3 General Background)

##Would operator overloading benefit Java?

Some objects would greatly benefit from operator overloading (concrete or numerical types, like BigDecimal, complex numbers, matrices, containers, iterators, comparators, parsers etc.).

In C++, you can profit from this benefit because of Stroustrup's humility. In Java, you're simply screwed because of Gosling's personal choice.

##Could it be added to Java?

The reasons for not adding operator overloading now in Java could be a mix of internal politics, allergy to the feature, distrust of developers (you know, the saboteur ones that seem to haunt Java teams...), compatibility with the previous JVMs, time to write a correct specification, etc..

So don't hold your breath waiting for this feature...

##But they do it in C#!!!

Yeah...

While this is far from being the only difference between the two languages, this one never fails to amuse me.

Apparently, the C# folks, with their "every primitive is a struct, and a struct derives from Object", got it right at first try.

##And they do it in other languages!!!

Despite all the FUD against used defined operator overloading, the following languages support it: Kotlin, Scala, Dart, Python, F#, C#, D, Algol 68, Smalltalk, Groovy, Perl 6, C++, Ruby, Haskell, MATLAB, Eiffel, Lua, Clojure, Fortran 90, Swift, Ada, Delphi 2005...

So many languages, with so many different (and sometimes opposing) philosophies, and yet they all agree on that point.

Food for thought...

How to reference static assets within vue javascript

It works for me by using require syntax like this:

$('.eventSlick').slick({
    dots: true,
    slidesToShow: 3,
    slidesToScroll: 1,
    autoplay: false,
    autoplaySpeed: 2000,
    arrows: true,
    draggable: false,
    prevArrow: '<button type="button" data-role="none" class="slick-prev"><img src="' + require("@/assets/img/icon/Arrow_Left.svg")+'"></button>',

Excel 2010 VBA - Close file No Save without prompt

If you're not wanting to save changes set savechanges to false

    Sub CloseBook2()
        ActiveWorkbook.Close savechanges:=False
    End Sub

for more examples, http://support.microsoft.com/kb/213428 and i believe in the past I've just used

    ActiveWorkbook.Close False

How to convert a string to a date in sybase

102 is the rule of thumb, convert (varchar, creat_tms, 102) > '2011'

How can I check if a string represents an int, without using try/except?

The proper RegEx solution would combine the ideas of Greg Hewgill and Nowell, but not use a global variable. You can accomplish this by attaching an attribute to the method. Also, I know that it is frowned upon to put imports in a method, but what I'm going for is a "lazy module" effect like http://peak.telecommunity.com/DevCenter/Importing#lazy-imports

edit: My favorite technique so far is to use exclusively methods of the String object.

#!/usr/bin/env python

# Uses exclusively methods of the String object
def isInteger(i):
    i = str(i)
    return i=='0' or (i if i.find('..') > -1 else i.lstrip('-+').rstrip('0').rstrip('.')).isdigit()

# Uses re module for regex
def isIntegre(i):
    import re
    if not hasattr(isIntegre, '_re'):
        print("I compile only once. Remove this line when you are confident in that.")
        isIntegre._re = re.compile(r"[-+]?\d+(\.0*)?$")
    return isIntegre._re.match(str(i)) is not None

# When executed directly run Unit Tests
if __name__ == '__main__':
    for obj in [
                # integers
                0, 1, -1, 1.0, -1.0,
                '0', '0.','0.0', '1', '-1', '+1', '1.0', '-1.0', '+1.0',
                # non-integers
                1.1, -1.1, '1.1', '-1.1', '+1.1',
                '1.1.1', '1.1.0', '1.0.1', '1.0.0',
                '1.0.', '1..0', '1..',
                '0.0.', '0..0', '0..',
                'one', object(), (1,2,3), [1,2,3], {'one':'two'}
            ]:
        # Notice the integre uses 're' (intended to be humorous)
        integer = ('an integer' if isInteger(obj) else 'NOT an integer')
        integre = ('an integre' if isIntegre(obj) else 'NOT an integre')
        # Make strings look like strings in the output
        if isinstance(obj, str):
            obj = ("'%s'" % (obj,))
        print("%30s is %14s is %14s" % (obj, integer, integre))

And for the less adventurous members of the class, here is the output:

I compile only once. Remove this line when you are confident in that.
                             0 is     an integer is     an integre
                             1 is     an integer is     an integre
                            -1 is     an integer is     an integre
                           1.0 is     an integer is     an integre
                          -1.0 is     an integer is     an integre
                           '0' is     an integer is     an integre
                          '0.' is     an integer is     an integre
                         '0.0' is     an integer is     an integre
                           '1' is     an integer is     an integre
                          '-1' is     an integer is     an integre
                          '+1' is     an integer is     an integre
                         '1.0' is     an integer is     an integre
                        '-1.0' is     an integer is     an integre
                        '+1.0' is     an integer is     an integre
                           1.1 is NOT an integer is NOT an integre
                          -1.1 is NOT an integer is NOT an integre
                         '1.1' is NOT an integer is NOT an integre
                        '-1.1' is NOT an integer is NOT an integre
                        '+1.1' is NOT an integer is NOT an integre
                       '1.1.1' is NOT an integer is NOT an integre
                       '1.1.0' is NOT an integer is NOT an integre
                       '1.0.1' is NOT an integer is NOT an integre
                       '1.0.0' is NOT an integer is NOT an integre
                        '1.0.' is NOT an integer is NOT an integre
                        '1..0' is NOT an integer is NOT an integre
                         '1..' is NOT an integer is NOT an integre
                        '0.0.' is NOT an integer is NOT an integre
                        '0..0' is NOT an integer is NOT an integre
                         '0..' is NOT an integer is NOT an integre
                         'one' is NOT an integer is NOT an integre
<object object at 0x103b7d0a0> is NOT an integer is NOT an integre
                     (1, 2, 3) is NOT an integer is NOT an integre
                     [1, 2, 3] is NOT an integer is NOT an integre
                {'one': 'two'} is NOT an integer is NOT an integre

Do Swift-based applications work on OS X 10.9/iOS 7 and lower?

Apple has announced that Swift apps will be backward compatible with iOS 7 and OS X Mavericks. The WWDC app is written in Swift.

What does localhost:8080 mean?

the localhost:8080 means your explicitly targeting port 8080.

UICollectionView Self Sizing Cells with Auto Layout

To whomever it may help,

I had that nasty crash if estimatedItemSize was set. Even if I returned 0 in numberOfItemsInSection. Therefore, the cells themselves and their auto-layout were not the cause of the crash... The collectionView just crashed, even when empty, just because estimatedItemSize was set for self-sizing.

In my case I reorganized my project, from a controller containing a collectionView to a collectionViewController, and it worked.

Go figure.

This project references NuGet package(s) that are missing on this computer

In my case it happened after I moved my solution folder from one location to another, re-organized it a bit and in the process its relative folder structure changed.

So I had to edit all entries similar to the following one in my .csproj file from

  <Import Project="..\packages\Microsoft.Bcl.Build.1.0.14\tools\Microsoft.Bcl.Build.targets" Condition="Exists('..\packages\Microsoft.Bcl.Build.1.0.14\tools\Microsoft.Bcl.Build.targets')" />

to

  <Import Project="packages\Microsoft.Bcl.Build.1.0.14\tools\Microsoft.Bcl.Build.targets" Condition="Exists('packages\Microsoft.Bcl.Build.1.0.14\tools\Microsoft.Bcl.Build.targets')" />

(Note the change from ..\packages\ to packages\. It might be a different relative structure in your case, but you get the idea.)

How to identify unused CSS definitions from multiple CSS files in a project

Chrome Developer Tools has an Audits tab which can show unused CSS selectors.

Run an audit, then, under Web Page Performance see Remove unused CSS rules

enter image description here

Understanding Spring @Autowired usage

Yes, you can configure the Spring servlet context xml file to define your beans (i.e., classes), so that it can do the automatic injection for you. However, do note, that you have to do other configurations to have Spring up and running and the best way to do that, is to follow a tutorial ground up.

Once you have your Spring configured probably, you can do the following in your Spring servlet context xml file for Example 1 above to work (please replace the package name of com.movies to what the true package name is and if this is a 3rd party class, then be sure that the appropriate jar file is on the classpath) :

<beans:bean id="movieFinder" class="com.movies.MovieFinder" />

or if the MovieFinder class has a constructor with a primitive value, then you could something like this,

<beans:bean id="movieFinder" class="com.movies.MovieFinder" >
    <beans:constructor-arg value="100" />
</beans:bean>

or if the MovieFinder class has a constructor expecting another class, then you could do something like this,

<beans:bean id="movieFinder" class="com.movies.MovieFinder" >
    <beans:constructor-arg ref="otherBeanRef" />
</beans:bean>

...where 'otherBeanRef' is another bean that has a reference to the expected class.

document.getElementById(id).focus() is not working for firefox or chrome

One more thing to add to this list to check:

Make sure the element you are trying to focus is not itself nor is contained in an element with "display: none" at the time you are trying to focus it.

Case insensitive access for generic dictionary

For you LINQers out there that never use a regular dictionary constructor

myCollection.ToDictionary(x => x.PartNumber, x => x.PartDescription, StringComparer.OrdinalIgnoreCase)

JPA CriteriaBuilder - How to use "IN" comparison operator

If I understand well, you want to Join ScheduleRequest with User and apply the in clause to the userName property of the entity User.

I'd need to work a bit on this schema. But you can try with this trick, that is much more readable than the code you posted, and avoids the Join part (because it handles the Join logic outside the Criteria Query).

List<String> myList = new ArrayList<String> ();
for (User u : usersList) {
    myList.add(u.getUsername());
}
Expression<String> exp = scheduleRequest.get("createdBy");
Predicate predicate = exp.in(myList);
criteria.where(predicate);

In order to write more type-safe code you could also use Metamodel by replacing this line:

Expression<String> exp = scheduleRequest.get("createdBy");

with this:

Expression<String> exp = scheduleRequest.get(ScheduleRequest_.createdBy);

If it works, then you may try to add the Join logic into the Criteria Query. But right now I can't test it, so I prefer to see if somebody else wants to try.


Not a perfect answer though may be code snippets might help.

public <T> List<T> findListWhereInCondition(Class<T> clazz,
            String conditionColumnName, Serializable... conditionColumnValues) {
        QueryBuilder<T> queryBuilder = new QueryBuilder<T>(clazz);
        addWhereInClause(queryBuilder, conditionColumnName,
                conditionColumnValues);
        queryBuilder.select();
        return queryBuilder.getResultList();

    }


private <T> void addWhereInClause(QueryBuilder<T> queryBuilder,
            String conditionColumnName, Serializable... conditionColumnValues) {

        Path<Object> path = queryBuilder.root.get(conditionColumnName);
        In<Object> in = queryBuilder.criteriaBuilder.in(path);
        for (Serializable conditionColumnValue : conditionColumnValues) {
            in.value(conditionColumnValue);
        }
        queryBuilder.criteriaQuery.where(in);

    }

How can I explicitly free memory in Python?

I had a similar problem in reading a graph from a file. The processing included the computation of a 200 000x200 000 float matrix (one line at a time) that did not fit into memory. Trying to free the memory between computations using gc.collect() fixed the memory-related aspect of the problem but it resulted in performance issues: I don't know why but even though the amount of used memory remained constant, each new call to gc.collect() took some more time than the previous one. So quite quickly the garbage collecting took most of the computation time.

To fix both the memory and performance issues I switched to the use of a multithreading trick I read once somewhere (I'm sorry, I cannot find the related post anymore). Before I was reading each line of the file in a big for loop, processing it, and running gc.collect() every once and a while to free memory space. Now I call a function that reads and processes a chunk of the file in a new thread. Once the thread ends, the memory is automatically freed without the strange performance issue.

Practically it works like this:

from dask import delayed  # this module wraps the multithreading
def f(storage, index, chunk_size):  # the processing function
    # read the chunk of size chunk_size starting at index in the file
    # process it using data in storage if needed
    # append data needed for further computations  to storage 
    return storage

partial_result = delayed([])  # put into the delayed() the constructor for your data structure
# I personally use "delayed(nx.Graph())" since I am creating a networkx Graph
chunk_size = 100  # ideally you want this as big as possible while still enabling the computations to fit in memory
for index in range(0, len(file), chunk_size):
    # we indicates to dask that we will want to apply f to the parameters partial_result, index, chunk_size
    partial_result = delayed(f)(partial_result, index, chunk_size)

    # no computations are done yet !
    # dask will spawn a thread to run f(partial_result, index, chunk_size) once we call partial_result.compute()
    # passing the previous "partial_result" variable in the parameters assures a chunk will only be processed after the previous one is done
    # it also allows you to use the results of the processing of the previous chunks in the file if needed

# this launches all the computations
result = partial_result.compute()

# one thread is spawned for each "delayed" one at a time to compute its result
# dask then closes the tread, which solves the memory freeing issue
# the strange performance issue with gc.collect() is also avoided

Save Dataframe to csv directly to s3 Python

I use AWS Data Wrangler. For example:

import awswrangler as wr
import pandas as pd

# read a local dataframe
df = pd.read_parquet('my_local_file.gz')

# upload to S3 bucket
wr.s3.to_parquet(df=df, path='s3://mys3bucket/file_name.gz')

The same applies to csv files. Instead of read_parquet and to_parquet, use read_csv and to_csv with the proper file extension.

How to avoid the need to specify the WSDL location in a CXF or JAX-WS generated webservice client?

@Martin Devillers solution works fine. For completeness, providing the steps below:

  1. Put your wsdl to resource directory like : src/main/resource
  2. In pom file, add both wsdlDirectory and wsdlLocation(don't miss / at the beginning of wsdlLocation), like below. While wsdlDirectory is used to generate code and wsdlLocation is used at runtime to create dynamic proxy.

    <wsdlDirectory>src/main/resources/mydir</wsdlDirectory>
    <wsdlLocation>/mydir/my.wsdl</wsdlLocation>
    
  3. Then in your java code(with no-arg constructor):

    MyPort myPort = new MyPortService().getMyPort();
    
  4. Here is the full code generation part in pom file, with fluent api in generated code.

    <plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>jaxws-maven-plugin</artifactId>
    <version>2.5</version>
    
    <dependencies>
        <dependency>
            <groupId>org.jvnet.jaxb2_commons</groupId>
            <artifactId>jaxb2-fluent-api</artifactId>
            <version>3.0</version>
        </dependency>
        <dependency>
            <groupId>com.sun.xml.ws</groupId>
            <artifactId>jaxws-tools</artifactId>
            <version>2.3.0</version>
        </dependency>
    </dependencies>
    
    <executions>
        <execution>
            <id>wsdl-to-java-generator</id>
            <goals>
                <goal>wsimport</goal>
            </goals>
            <configuration>
                <xjcArgs>
                    <xjcArg>-Xfluent-api</xjcArg>
                </xjcArgs>
                <keep>true</keep>
                <wsdlDirectory>src/main/resources/package</wsdlDirectory>
                <wsdlLocation>/package/my.wsdl</wsdlLocation>
                <sourceDestDir>${project.build.directory}/generated-sources/annotations/jaxb</sourceDestDir>
                <packageName>full.package.here</packageName>
            </configuration>
        </execution>
    </executions>
    

Possible reasons for timeout when trying to access EC2 instance

I had the same problem and I solved it by adding a rule to the security Groups

Inbound SSH 0.0.0.0/0

Or you can add your IP address only

Setting Windows PATH for Postgres tools

Set path For PostgreSQL in Windows:

  1. Searching for env will show Edit environment variables for your account
  2. Select Environment Variables
  3. From the System Variables box select PATH
  4. Click New (to add new path)

Change the PATH variable to include the bin directory of your PostgreSQL installation.
then add new path their....[for example]

C:\Program Files\PostgreSQL\12\bin

After that click OK

Open CMD/Command Prompt. Type this to open psql

psql -U username database_name

For Example psql -U postgres test

Now, you will be prompted to give Password for the User. (It will be hidden as a security measure).

Then you are good to go.

how to display none through code behind

if(displayit){
  login_div.Style["display"]="inline"; //the default display mode
}else{
  login_div.Style["display"]="none";
}

Adding this code into Page_Load should work. (if doing it at Page_Init you'll have to contend with viewstate changing what you put in it)

What is web.xml file and what are all things can I do with it?

Deployment descriptor file "web.xml" : Through the proper use of the deployment descriptor file, web.xml, you can control many aspects of the Web application behavior, from preloading servlets, to restricting resource access, to controlling session time-outs.

web.xml : is used to control many facets of a Web application. Using web.xml, you can assign custom URLs for invoking servlets, specify initialization parameters for the entire application as well as for specific servlets, control session timeouts, declare filters, declare security roles, restrict access to Web resources based on declared security roles, and so on.

configuring project ':app' failed to find Build Tools revision

also try to increase gradle version in your project's build.gradle. It helped me

React - How to force a function component to render?

This can be done without explicitly using hooks provided you add a prop to your component and a state to the stateless component's parent component:

const ParentComponent = props => {
  const [updateNow, setUpdateNow] = useState(true)

  const updateFunc = () => {
    setUpdateNow(!updateNow)
  }

  const MyComponent = props => {
    return (<div> .... </div>)
  }

  const MyButtonComponent = props => {
    return (<div> <input type="button" onClick={props.updateFunc} />.... </div>)
  }

  return (
    <div> 
      <MyComponent updateMe={updateNow} />
      <MyButtonComponent updateFunc={updateFunc}/>
    </div>
  )
}

How to get the first column of a pandas DataFrame as a Series?

Isn't this the simplest way?

By column name:

In [20]: df = pd.DataFrame({'x' : [1, 2, 3, 4], 'y' : [4, 5, 6, 7]})
In [21]: df
Out[21]:
    x   y
0   1   4
1   2   5
2   3   6
3   4   7

In [23]: df.x
Out[23]:
0    1
1    2
2    3
3    4
Name: x, dtype: int64

In [24]: type(df.x)
Out[24]:
pandas.core.series.Series

Reverse ip, find domain names on ip address

You can use nslookup on the IP. Reverse DNS is defined with the .in-addr.arpa domain.

Example:

nslookup somedomain.com

yields 123.21.2.3, and then you do:

nslookup 123.21.2.3

this will ask 3.2.21.123.in-addr.arpa and yield the domain name (if there is one defined for reverse DNS).

Live Video Streaming with PHP

I am not saying that you have to abandon PHP, but you need different technologies here.

Let's start off simple (without Akamai :-)) and think about the implications here. Video, chat, etc. - it's all client-side in the beginning. The user has a webcam, you want to grab the signal somehow and send it to the server. There is no PHP so far.

I know that Flash supports this though (check this tutorial on webcams and flash) so you could use Flash to transport the content to the server. I think if you'll stay with Flash, then Flex (flex and webcam tutorial) is probably a good idea to look into.

So those are just the basics, maybe it gives you an idea of where you need to research because obviously this won't give you a full video chat inside your app yet. For starters, you will need some sort of way to record the streams and re-publish them so others see other people from the chat, etc..

I'm also not sure how much traffic and bandwidth this is gonna consume though and generally, you will need way more than a Stackoverflow question to solve this issue. Best would be to do a full spec of your app and then hire some people to help you build it.

HTH!

Redirect HTTP to HTTPS on default virtual host without ServerName

Try adding this in your vhost config:

RewriteEngine On
RewriteRule ^(.*)$ https://%{HTTP_HOST}$1 [R=301,L]

android EditText - finished typing event

I had the same problem when trying to implement 'now typing' on chat app. try to extend EditText as follows:

public class TypingEditText extends EditText implements TextWatcher {

private static final int TypingInterval = 2000;


public interface OnTypingChanged {
    public void onTyping(EditText view, boolean isTyping);
}
private OnTypingChanged t;
private Handler handler;
{
    handler = new Handler();
}
public TypingEditText(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    this.addTextChangedListener(this);
}

public TypingEditText(Context context, AttributeSet attrs) {
    super(context, attrs);
    this.addTextChangedListener(this);
}

public TypingEditText(Context context) {
    super(context);
    this.addTextChangedListener(this);
}

public void setOnTypingChanged(OnTypingChanged t) {
    this.t = t;
}

@Override
public void afterTextChanged(Editable s) {
    if(t != null){
        t.onTyping(this, true);
        handler.removeCallbacks(notifier);
        handler.postDelayed(notifier, TypingInterval);
    }

}

private Runnable notifier = new Runnable() {

    @Override
    public void run() {
        if(t != null)
            t.onTyping(TypingEditText.this, false);
    }
};

@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) { }


@Override
public void onTextChanged(CharSequence text, int start, int lengthBefore, int lengthAfter) { }

}

How does Java deal with multiple conditions inside a single IF statement

Yes,that is called short-circuiting.

Please take a look at this wikipedia page on short-circuiting

How to create a pivot query in sql server without aggregate function

SELECT *
FROM
(
SELECT [Period], [Account], [Value]
FROM TableName
) AS source
PIVOT
(
    MAX([Value])
    FOR [Period] IN ([2000], [2001], [2002])
) as pvt

Another way,

SELECT ACCOUNT,
      MAX(CASE WHEN Period = '2000' THEN Value ELSE NULL END) [2000],
      MAX(CASE WHEN Period = '2001' THEN Value ELSE NULL END) [2001],
      MAX(CASE WHEN Period = '2002' THEN Value ELSE NULL END) [2002]
FROM tableName
GROUP BY Account

How to implement debounce in Vue2?

Very simple without lodash

  handleScroll: function() {
    if (this.timeout) 
      clearTimeout(this.timeout); 

    this.timeout = setTimeout(() => {
      // your action
    }, 200); // delay
  }

Symfony2 and date_default_timezone_get() - It is not safe to rely on the system's timezone settings

add this code to Your AppKernel Class:

public function init()
{
    date_default_timezone_set('Asia/Tehran');
    parent::init();
}

Global and local variables in R

<- does assignment in the current environment.

When you're inside a function R creates a new environment for you. By default it includes everything from the environment in which it was created so you can use those variables as well but anything new you create will not get written to the global environment.

In most cases <<- will assign to variables already in the global environment or create a variable in the global environment even if you're inside a function. However, it isn't quite as straightforward as that. What it does is checks the parent environment for a variable with the name of interest. If it doesn't find it in your parent environment it goes to the parent of the parent environment (at the time the function was created) and looks there. It continues upward to the global environment and if it isn't found in the global environment it will assign the variable in the global environment.

This might illustrate what is going on.

bar <- "global"
foo <- function(){
    bar <- "in foo"
    baz <- function(){
        bar <- "in baz - before <<-"
        bar <<- "in baz - after <<-"
        print(bar)
    }
    print(bar)
    baz()
    print(bar)
}
> bar
[1] "global"
> foo()
[1] "in foo"
[1] "in baz - before <<-"
[1] "in baz - after <<-"
> bar
[1] "global"

The first time we print bar we haven't called foo yet so it should still be global - this makes sense. The second time we print it's inside of foo before calling baz so the value "in foo" makes sense. The following is where we see what <<- is actually doing. The next value printed is "in baz - before <<-" even though the print statement comes after the <<-. This is because <<- doesn't look in the current environment (unless you're in the global environment in which case <<- acts like <-). So inside of baz the value of bar stays as "in baz - before <<-". Once we call baz the copy of bar inside of foo gets changed to "in baz" but as we can see the global bar is unchanged. This is because the copy of bar that is defined inside of foo is in the parent environment when we created baz so this is the first copy of bar that <<- sees and thus the copy it assigns to. So <<- isn't just directly assigning to the global environment.

<<- is tricky and I wouldn't recommend using it if you can avoid it. If you really want to assign to the global environment you can use the assign function and tell it explicitly that you want to assign globally.

Now I change the <<- to an assign statement and we can see what effect that has:

bar <- "global"
foo <- function(){
    bar <- "in foo"   
    baz <- function(){
        assign("bar", "in baz", envir = .GlobalEnv)
    }
    print(bar)
    baz()
    print(bar)
}
bar
#[1] "global"
foo()
#[1] "in foo"
#[1] "in foo"
bar
#[1] "in baz"

So both times we print bar inside of foo the value is "in foo" even after calling baz. This is because assign never even considered the copy of bar inside of foo because we told it exactly where to look. However, this time the value of bar in the global environment was changed because we explicitly assigned there.

Now you also asked about creating local variables and you can do that fairly easily as well without creating a function... We just need to use the local function.

bar <- "global"
# local will create a new environment for us to play in
local({
    bar <- "local"
    print(bar)
})
#[1] "local"
bar
#[1] "global"

Android MediaPlayer Stop and Play

just in case someone comes to this question, I have the easier version.

public static MediaPlayer mp;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button b = (Button) findViewById(R.id.button);
        Button b2 = (Button) findViewById(R.id.button2);


        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                mp = MediaPlayer.create(MainActivity.this, R.raw.game);
                mp.start();
            }
        });

        b2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mp.stop();
               // mp.start();
            }
        });
    }

Passing dynamic javascript values using Url.action()

The easiest way is:

  onClick= 'location.href="/controller/action/"+paramterValue'

Spring Boot - inject map from application.yml

Solution for pulling Map using @Value from application.yml property coded as multiline

application.yml

other-prop: just for demo 

my-map-property-name: "{\
         key1: \"ANY String Value here\", \  
         key2: \"any number of items\" , \ 
         key3: \"Note the Last item does not have comma\" \
         }"

other-prop2: just for demo 2 

Here the value for our map property "my-map-property-name" is stored in JSON format inside a string and we have achived multiline using \ at end of line

myJavaClass.java

import org.springframework.beans.factory.annotation.Value;

public class myJavaClass {

@Value("#{${my-map-property-name}}") 
private Map<String,String> myMap;

public void someRandomMethod (){
    if(myMap.containsKey("key1")) {
            //todo...
    } }

}

More explanation

  • \ in yaml it is Used to break string into multiline

  • \" is escape charater for "(quote) in yaml string

  • {key:value} JSON in yaml which will be converted to Map by @Value

  • #{ } it is SpEL expresion and can be used in @Value to convert json int Map or Array / list Reference

Tested in a spring boot project

How do browser cookie domains work?

For an extensive coverage review the contents of RFC2965. Of course that doesn't necessarily mean that all browsers behave exactly the same way.

However in general the rule for default Path if none specified in the cookie is the path in the URL from which the Set-Cookie header arrived. Similarly the default for the Domain is the full host name in the URL from which the Set-Cookie arrived.

Matching rules for the domain require the cookie Domain to match the host to which the request is being made. The cookie can specify a wider domain match by include *. in the domain attribute of Set-Cookie (this one area that browsers may vary). Matching the path (assuming the domain matches) is a simple matter that the requested path must be inside the path specified on the cookie. Typically session cookies are set with path=/ or path=/applicationName/ so the cookie is available to all requests into the application.


Response to Added:

  • Will a cookie for .example.com be available for www.example.com? Yes
  • Will a cookie for .example.com be available for example.com? Don't Know
  • Will a cookie for example.com be available for www.example.com? Shouldn't but... *
  • Will a cookie for example.com be available for anotherexample.com? No
  • Will www.example.com be able to set cookie for example.com? Yes
  • Will www.example.com be able to set cookie for www2.example.com? No (Except via .example.com)
  • Will www.example.com be able to set cookie for .com? No (Can't set a cookie this high up the namespace nor can you set one for something like .co.uk).

* I'm unable to test this right now but I have an inkling that at least IE7/6 would treat the path example.com as if it were .example.com.

JUnit Testing private variables?

Reflection e.g.:

public class PrivateObject {

  private String privateString = null;

  public PrivateObject(String privateString) {
    this.privateString = privateString;
  }
}
PrivateObject privateObject = new PrivateObject("The Private Value");

Field privateStringField = PrivateObject.class.
            getDeclaredField("privateString");

privateStringField.setAccessible(true);

String fieldValue = (String) privateStringField.get(privateObject);
System.out.println("fieldValue = " + fieldValue);

How do I get whole and fractional parts from double in JSP/Java?

Since the fmt:formatNumber tag doesn't always yield the correct result, here is another JSP-only approach: It just formats the number as string and does the rest of the computation on the string, since that is easier and doesn't involve further floating point arithmetics.

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>

<%
  double[] numbers = { 0.0, 3.25, 3.75, 3.5, 2.5, -1.5, -2.5 };
  pageContext.setAttribute("numbers", numbers);
%>

<html>
  <body>
    <ul>
      <c:forEach var="n" items="${numbers}">
        <li>${n} = ${fn:substringBefore(n, ".")} + ${n - fn:substringBefore(n, ".")}</li>
      </c:forEach>
    </ul>
  </body>
</html>

Table is marked as crashed and should be repaired

Connect to your server via SSH

then connect to your mysql console

and

USE user_base
REPAIR TABLE TABLE;

-OR-

If there are a lot of broken tables in current database:

mysqlcheck -uUSER -pPASSWORD  --repair --extended user_base

If there are a lot of broken tables in a lot of databases:

mysqlcheck -uUSER -pPASSWORD  --repair --extended -A

How can I hide a checkbox in html?

You need to add the element type to the class, otherwise it will not work.

_x000D_
_x000D_
.hide-checkbox { display: none }        /* This will not work! */_x000D_
input.hide-checkbox { display: none }   /* But this will. */ 
_x000D_
<input class="hide-checkbox" id="checkbox" />_x000D_
<label for="checkbox">Checkbox</label>
_x000D_
_x000D_
_x000D_

It looks too simple, but try it out!

MongoDB: Server has startup warnings ''Access control is not enabled for the database''

Mongodb v3.4

You need to do the following to create a secure database:

Make sure the user starting the process has permissions and that the directories exist (/data/db in this case).

1) Start MongoDB without access control.

mongod --port 27017 --dbpath /data/db

2) Connect to the instance.

mongo --port 27017

3) Create the user administrator (in the admin authentication database).

use admin
db.createUser(
  {
    user: "myUserAdmin",
    pwd: "abc123",
    roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]
  }
)

4) Re-start the MongoDB instance with access control.

mongod --auth --port 27017 --dbpath /data/db

5) Connect and authenticate as the user administrator.

mongo --port 27017 -u "myUserAdmin" -p "abc123" --authenticationDatabase "admin"

6) Create additional users as needed for your deployment (e.g. in the test authentication database).

use test
db.createUser(
  {
    user: "myTester",
    pwd: "xyz123",
    roles: [ { role: "readWrite", db: "test" },
             { role: "read", db: "reporting" } ]
  }
)

7) Connect and authenticate as myTester.

mongo --port 27017 -u "myTester" -p "xyz123" --authenticationDatabase "test"

I basically just explained the short version of the official docs here: https://docs.mongodb.com/master/tutorial/enable-authentication/

How much RAM is SQL Server actually using?

Go to management studio and run sp_helpdb <db_name>, it will give detailed disk usage for the specified database. Running it without any parameter values will list high level information for all databases in the instance.

Using custom std::set comparator

1. Modern C++20 solution

auto cmp = [](int a, int b) { return ... };
std::set<int, decltype(cmp)> s;

We use lambda function as comparator. As usual, comparator should return boolean value, indicating whether the element passed as first argument is considered to go before the second in the specific strict weak ordering it defines.

Online demo

2. Modern C++11 solution

auto cmp = [](int a, int b) { return ... };
std::set<int, decltype(cmp)> s(cmp);

Before C++20 we need to pass lambda as argument to set constructor

Online demo

3. Similar to first solution, but with function instead of lambda

Make comparator as usual boolean function

bool cmp(int a, int b) {
    return ...;
}

Then use it, either this way:

std::set<int, decltype(cmp)*> s(cmp);

Online demo

or this way:

std::set<int, decltype(&cmp)> s(&cmp);

Online demo

4. Old solution using struct with () operator

struct cmp {
    bool operator() (int a, int b) const {
        return ...
    }
};

// ...
// later
std::set<int, cmp> s;

Online demo

5. Alternative solution: create struct from boolean function

Take boolean function

bool cmp(int a, int b) {
    return ...;
}

And make struct from it using std::integral_constant

#include <type_traits>
using Cmp = std::integral_constant<decltype(&cmp), &cmp>;

Finally, use the struct as comparator

std::set<X, Cmp> set;

Online demo

How to set environment variables in Jenkins?

We use groovy job file:

description('')
steps {
    environmentVariables {
        envs(PUPPETEER_SKIP_CHROMIUM_DOWNLOAD: true)
    }
}

Angular 2 declaring an array of objects

public mySentences:Array<Object> = [
    {id: 1, text: 'Sentence 1'},
    {id: 2, text: 'Sentence 2'},
    {id: 3, text: 'Sentence 3'},
    {id: 4, text: 'Sentenc4 '},
];

Or rather,

export interface type{
    id:number;
    text:string;
}

public mySentences:type[] = [
    {id: 1, text: 'Sentence 1'},
    {id: 2, text: 'Sentence 2'},
    {id: 3, text: 'Sentence 3'},
    {id: 4, text: 'Sentenc4 '},
];

In a Bash script, how can I exit the entire script if a certain condition occurs?

Use set -e

#!/bin/bash

set -e

/bin/command-that-fails
/bin/command-that-fails2

The script will terminate after the first line that fails (returns nonzero exit code). In this case, command-that-fails2 will not run.

If you were to check the return status of every single command, your script would look like this:

#!/bin/bash

# I'm assuming you're using make

cd /project-dir
make
if [[ $? -ne 0 ]] ; then
    exit 1
fi

cd /project-dir2
make
if [[ $? -ne 0 ]] ; then
    exit 1
fi

With set -e it would look like:

#!/bin/bash

set -e

cd /project-dir
make

cd /project-dir2
make

Any command that fails will cause the entire script to fail and return an exit status you can check with $?. If your script is very long or you're building a lot of stuff it's going to get pretty ugly if you add return status checks everywhere.