Programs & Examples On #Automount

For questions regarding the auto-mounting of filesystems, for example, automatic reading of usb storage, enabled in many operating systems.

How to select label for="XYZ" in CSS?

If the label immediately follows a specified input element:

input#example + label { ... }
input:checked + label { ... }

500.19 - Internal Server Error - The requested page cannot be accessed because the related configuration data for the page is invalid

I had this error with Visual Studion 2019, my project was NopCommerce 4.30 which is an ASP.Net Core 3.1 project. I added page "gouden-munten-buitenland" to be the starting page and I only got the error when going to that page. Turned out that Visual Studio generated an invalid applicationHost.config :

    <add name="gouden-munten-buitenland AppPool" autoStart="true" />
    <add name="gouden-munten-buitenland AppPool 2" autoStart="true" /> <!-- WRONG -->
    <add name="Nop.Web AppPool" managedRuntimeVersion="" />
    <applicationPoolDefaults managedRuntimeVersion="v4.0">
    <processModel loadUserProfile="true" setProfileEnvironment="false" />


    <site name="Nop.Web" id="2">
    <application path="/gouden-munten-buitenland/gouden-munten-buitenland" applicationPool="gouden-munten-buitenland AppPool">
        <virtualDirectory path="/" physicalPath="C:\Usr\Stephan\Wrk\Kevelam\kNop.430\Presentation\Nop.Web" />
    <application path="/gouden-munten-buitenland" applicationPool="gouden-munten-buitenland AppPool 2">
        <virtualDirectory path="/" physicalPath="C:\Usr\Stephan\Wrk\Kevelam\kNop.430\Presentation\Nop.Web" />
    </application> <!-- WRONG -->

I removed the nodes identified as 'WRONG' and then it worked.

Failed to load resource: the server responded with a status of 404 (Not Found) css

you have defined the public dir in app root/public

app.use(express.static(__dirname + '/public')); 

so you have to use:


Run CRON job everyday at specific time

Cron utility is an effective way to schedule a routine background job at a specific time and/or day on an on-going basis.

Linux Crontab Format


enter image description here

Example::Scheduling a Job For a Specific Time

The basic usage of cron is to execute a job in a specific time as shown below. This will execute the Full backup shell script (full-backup) on 10th June 08:30 AM.

Please note that the time field uses 24 hours format. So, for 8 AM use 8, and for 8 PM use 20.

30 08 10 06 * /home/yourname/full-backup
  • 30 – 30th Minute
  • 08 – 08 AM
  • 10 – 10th Day
  • 06 – 6th Month (June)
  • *– Every day of the week

In your case, for 2.30PM,

30 14 * * * YOURCMD
  1. 30 – 30th Minute
  2. 14 – 2PM
  3. *– Every day
  4. *– Every month
  5. *– Every day of the week

To know more about cron, visit this website.

Can I prevent text in a div block from overflowing?

overflow: scroll ? Or auto. in the style attribute.

mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists

When I used the code mysqld_safe --skip-grant-tables & but I get the error:

mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists.

$ systemctl stop  mysql.service
$ ps -eaf|grep mysql
$ mysqld_safe --skip-grant-tables &

I solved:

$ mkdir -p /var/run/mysqld
$ chown mysql:mysql /var/run/mysqld

Now I use the same code mysqld_safe --skip-grant-tables & and get

mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

If I use $ mysql -u root I'll get :

Server version: 5.7.18-0ubuntu0.16.04.1 (Ubuntu)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.


Now time to change password:

mysql> use mysql
mysql> describe user;

Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A

Database changed

mysql> SET PASSWORD FOR root@'localhost' = PASSWORD('newpwd');

or If you have a mysql root account that can connect from everywhere, you should also do:

UPDATE mysql.user SET Password=PASSWORD('newpwd') WHERE User='root';

Alternate Method:

   USE mysql
   UPDATE user SET Password = PASSWORD('newpwd')
   WHERE Host = 'localhost' AND User = 'root';

And if you have a root account that can access from everywhere:

 USE mysql
 UPDATE user SET Password = PASSWORD('newpwd')
 WHERE Host = '%' AND User = 'root';`enter code here

now need to quit from mysql and stop/start

sudo /etc/init.d/mysql stop
sudo /etc/init.d/mysql start

now again ` mysql -u root -p' and use the new password to get


Embed Youtube video inside an Android app

there is an official YouTube Android Player API wich you can use. This is a bit more complicated but it is working better than other solutions using webclients.

First you must register your app in Googles API Console. This is completely free until your app gets over 25k request a month (or something like that). There are complete anf great tutorials under the link. I hope you can understand them. If not, ask! :)

How do I format currencies in a Vue component?

I have created a filter. The filter can be used in any page.

Vue.filter('toCurrency', function (value) {
    if (typeof value !== "number") {
        return value;
    var formatter = new Intl.NumberFormat('en-US', {
        style: 'currency',
        currency: 'USD',
        minimumFractionDigits: 0
    return formatter.format(value);

Then I can use this filter like this:

        <td class="text-right">
            {{ invoice.fees | toCurrency }}

I used these related answers to help with the implementation of the filter:

Better way to Format Currency Input editText?

I change the class with implements TextWatcher to use Brasil currency formats and adjusting cursor position when editing the value.

public class MoneyTextWatcher implements TextWatcher {

    private EditText editText;

    private String lastAmount = "";

    private int lastCursorPosition = -1;

    public MoneyTextWatcher(EditText editText) {
        this.editText = editText;

    public void onTextChanged(CharSequence amount, int start, int before, int count) {

        if (!amount.toString().equals(lastAmount)) {

            String cleanString = clearCurrencyToNumber(amount.toString());

            try {

                String formattedAmount = transformToCurrency(cleanString);

                if (lastCursorPosition != lastAmount.length() && lastCursorPosition != -1) {
                    int lengthDelta = formattedAmount.length() - lastAmount.length();
                    int newCursorOffset = max(0, min(formattedAmount.length(), lastCursorPosition + lengthDelta));
            } catch (Exception e) {
               //log something

    public void afterTextChanged(Editable s) {

    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        String value = s.toString();
            String cleanString = clearCurrencyToNumber(value);
            String formattedAmount = transformToCurrency(cleanString);
            lastAmount = formattedAmount;
            lastCursorPosition = editText.getSelectionStart();

    public static String clearCurrencyToNumber(String currencyValue) {
        String result = null;

        if (currencyValue == null) {
            result = "";
        } else {
            result = currencyValue.replaceAll("[(a-z)|(A-Z)|($,. )]", "");
        return result;

    public static boolean isCurrencyValue(String currencyValue, boolean podeSerZero) {
        boolean result;

        if (currencyValue == null || currencyValue.length() == 0) {
            result = false;
        } else {
            if (!podeSerZero && currencyValue.equals("0,00")) {
                result = false;
            } else {
                result = true;
        return result;

    public static String transformToCurrency(String value) {
        double parsed = Double.parseDouble(value);
        String formatted = NumberFormat.getCurrencyInstance(new Locale("pt", "BR")).format((parsed / 100));
        formatted = formatted.replaceAll("[^(0-9)(.,)]", "");
        return formatted;

Entityframework Join using join method and lambdas

You can find a few examples here:

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;

DataTable contacts = ds.Tables["Contact"];
DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    order => order.Field<Int32>("ContactID"),
    contact => contact.Field<Int32>("ContactID"),
    (contact, order) => new
        ContactID = contact.Field<Int32>("ContactID"),
        SalesOrderID = order.Field<Int32>("SalesOrderID"),
        FirstName = contact.Field<string>("FirstName"),
        Lastname = contact.Field<string>("Lastname"),
        TotalDue = order.Field<decimal>("TotalDue")

foreach (var contact_order in query)
    Console.WriteLine("ContactID: {0} "
                    + "SalesOrderID: {1} "
                    + "FirstName: {2} "
                    + "Lastname: {3} "
                    + "TotalDue: {4}",

Or just google for 'linq join method syntax'.

How do I POST form data with UTF-8 encoding by using curl?

You CAN use UTF-8 in the POST request, all you need is to specify the charset in your request.

You should use this request:

curl -X POST -H "Content-Type: application/x-www-form-urlencoded; charset=utf-8" --data-ascii "content=derinhält&date=asdf"

What are POD types in C++?

The concept of POD and the type trait std::is_pod will be deprecated in C++20. See this question for further information.

How to remove entity with ManyToMany relationship in JPA (and corresponding join table rows)?

This is what I ended up doing. Hopefully someone might find it useful.

public void deleteGroup(Long groupId) {
    Group group = groupRepository.findById(groupId).orElseThrow();
    group.getUsers().forEach(u -> u.getGroups().remove(group));

Granting Rights on Stored Procedure to another user of Oracle

I'm not sure that I understand what you mean by "rights of ownership".

If User B owns a stored procedure, User B can grant User A permission to run the stored procedure

GRANT EXECUTE ON b.procedure_name TO a

User A would then call the procedure using the fully qualified name, i.e.

  b.procedure_name( <<list of parameters>> );

Alternately, User A can create a synonym in order to avoid having to use the fully qualified procedure name.

CREATE SYNONYM procedure_name FOR b.procedure_name;

  procedure_name( <<list of parameters>> );

C# DateTime to UTC Time without changing the time

Use the DateTime.ToUniversalTime method.

Calculating a directory's size using Python?

Using pathlib I came up this one-liner to get the size of a folder:

sum(file.stat().st_size for file in Path(folder).rglob('*'))

And this is what I came up with for a nicely formatted output:

from pathlib import Path

def get_folder_size(folder):
    return ByteSize(sum(file.stat().st_size for file in Path(folder).rglob('*')))

class ByteSize(int):

    _kB = 1024
    _suffixes = 'B', 'kB', 'MB', 'GB', 'PB'

    def __new__(cls, *args, **kwargs):
        return super().__new__(cls, *args, **kwargs)

    def __init__(self, *args, **kwargs):
        self.bytes = self.B = int(self)
        self.kilobytes = self.kB = self / self._kB**1
        self.megabytes = self.MB = self / self._kB**2
        self.gigabytes = self.GB = self / self._kB**3
        self.petabytes = self.PB = self / self._kB**4
        *suffixes, last = self._suffixes
        suffix = next((
            for suffix in suffixes
            if 1 < getattr(self, suffix) < self._kB
        ), last)
        self.readable = suffix, getattr(self, suffix)


    def __str__(self):
        return self.__format__('.2f')

    def __repr__(self):
        return '{}({})'.format(self.__class__.__name__, super().__repr__())

    def __format__(self, format_spec):
        suffix, val = self.readable
        return '{val:{fmt}} {suf}'.format(val=val, fmt=format_spec, suf=suffix)

    def __sub__(self, other):
        return self.__class__(super().__sub__(other))

    def __add__(self, other):
        return self.__class__(super().__add__(other))

    def __mul__(self, other):
        return self.__class__(super().__mul__(other))

    def __rsub__(self, other):
        return self.__class__(super().__sub__(other))

    def __radd__(self, other):
        return self.__class__(super().__add__(other))

    def __rmul__(self, other):
        return self.__class__(super().__rmul__(other))   


>>> size = get_folder_size("c:/users/tdavis/downloads")
>>> print(size)
5.81 GB
>>> size.GB
>>> size.gigabytes
>>> size.PB
>>> size.MB
>>> size

I also came across this question, which has some more compact and probably more performant strategies for printing file sizes.

Differences in string compare methods in C#

  • s1.CompareTo(s2): Do NOT use if primary purpose is to determine whether two strings are equivalent
  • s1 == s2: Cannot ignore case
  • s1.Equals(s2, StringComparison): Throws NullReferenceException if s1 is null
  • String.Equals(s2, StringComparison): By process of eliminiation, this static method is the WINNER (assuming a typical use case to determine whether two strings are equivalent)!

Angular2 If ngModel is used within a form tag, either the name attribute must be set or the form

I noticed that the Chrome developer tool sometimes only underlines the first element in swiggly red even if it is correctly set up with a name. This threw me off for a while.

One must be sure to add a name to every element on the form that contains ngModel regardless of which one is squiggly underlined.

Change Spinner dropdown icon

Try applying following style to your spinner using


//Spinner Style:

<style name="SpinnerTheme" parent="android:Widget.Spinner">
    <item name="android:background">@drawable/bg_spinner</item>

//bg_spinner.xml Replace the arrow_down_gray with your arrow

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="">



                    <gradient android:angle="90" android:endColor="#ffffff" android:startColor="#ffffff" android:type="linear" />

                    <stroke android:width="0.33dp" android:color="#0fb1fa" />

                    <corners android:radius="0dp" />

                    <padding android:bottom="3dp" android:left="3dp" android:right="3dp" android:top="3dp" />

            <item android:right="5dp">

                <bitmap android:gravity="center_vertical|right" android:src="@drawable/arrow_down_gray" />





How to retrieve all keys (or values) from a std::map and put them into a vector?

There is a boost range adaptor for this purpose:

#include <boost/range/adaptor/map.hpp>
#include <boost/range/algorithm/copy.hpp>
vector<int> keys;
boost::copy(m | boost::adaptors::map_keys, std::back_inserter(keys));

There is a similar map_values range adaptor for extracting the values.

Check that Field Exists with MongoDB

db.<COLLECTION NAME>.find({ "<FIELD NAME>": { $exists: true, $ne: null } })

Java error - "invalid method declaration; return type required"

Every method (other than a constructor) must have a return type.

public double diameter(){...

How to pass arguments within docker-compose?

This can now be done as of docker-compose v2+ as part of the build object;


version: '2'
            context: . #current dir as build context
                var1: 1
                var2: c

See the docker compose docs.

In the above example "var1" and "var2" will be sent to the build environment.

Note: any env variables (specified by using the environment block) which have the same name as args variable(s) will override that variable.

How to change the background color of the options menu?

Just ran into this issue too, on an App that had to be compatible with Gingerbread and still retain as much of the styling from Holo-enabled devices as possible.

I found a relatively clean solution, that worked OK for me.

In the theme I use a 9-patch drawable background to get a custom background color:

<style name="Theme.Styled" parent="Theme.Sherlock">
   <item name="android:panelFullBackground">@drawable/menu_hardkey_panel</item>

I gave up trying to style the text color, and just used a Spannable to set the text color for my item in code:

public boolean onCreateOptionsMenu(Menu menu) {
   MenuInflater inflater = getSupportMenuInflater();
   inflater.inflate(, menu);

   if (android.os.Build.VERSION.SDK_INT < 
        android.os.Build.VERSION_CODES.HONEYCOMB) {

        SpannableStringBuilder text = new SpannableStringBuilder();
        text.setSpan(new ForegroundColorSpan(Color.WHITE), 
                0, text.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

        MenuItem item1 = menu.findItem(;

   return true;

Constraint Layout Vertical Align Center

You can easily center multiple things by creating a chain. It works both vertically and horizontally

Link to official documentation about chains

Edit to answer comment :

<?xml version="1.0" encoding="utf-8"?>

This code gives this result

You have the horizontal chain : first_score <=> second_score <=> third_score. second_score is centered vertically. The other scores are centered vertically according to it.

You can definitely create a vertical chain first_score <=> subtitle and center it according to second_score

Two Radio Buttons ASP.NET C#

In order to make it work, you have to set property GroupName of both radio buttons to the same value:

<asp:RadioButton id="rbMetric" runat="server" GroupName="measurementSystem"></asp:RadioButton>
<asp:RadioButton id="rbUS" runat="server" GroupName="measurementSystem"></asp:RadioButton>

Personally, I prefer to use a RadioButtonList:

<asp:RadioButtonList ID="rblMeasurementSystem" runat="server">
    <asp:ListItem Text="Metric" Value="metric" />
    <asp:ListItem Text="US" Value="us" />

How to check for the type of a template parameter?

In C++17, we can use variants.

To use std::variant, you need to include the header:

#include <variant>

After that, you may add std::variant in your code like this:

using Type = std::variant<Animal, Person>;

template <class T>
void foo(Type type) {
    if (std::is_same_v<type, Animal>) {
        // Do stuff...
    } else {
        // Do stuff...

Is 'bool' a basic datatype in C++?

C is meant to be a step above assembly language. The C if-statement is really just syntactical sugar for "branch-if-zero", so the idea of booleans as an independent datatype was a foreign concept at the time. (1)

Even now, C/C++ booleans are usually little more than an alias for a single byte data type. As such, it's really more of a purposing label than an independent datatype.

(1) Of course, modern compilers are a bit more advanced in their handling of if statements. This is from the standpoint of C as a new language.

Download/Stream file from URL -

The accepted solution from Dallas was working for us if we use Load Balancer on the Citrix Netscaler (without WAF policy).

The download of the file doesn't work through the LB of the Netscaler when it is associated with WAF as the current scenario (Content-length not being correct) is a RFC violation and AppFW resets the connection, which doesn't happen when WAF policy is not associated.

So what was missing was:


See also: Trying to stream a PDF file with is producing a "damaged file"

Using the && operator in an if statement

So to make your expression work, changing && for -a will do the trick.

It is correct like this:

 if [ -f $VAR1 ] && [ -f $VAR2 ] && [ -f $VAR3 ]
 then  ....

or like

 if [[ -f $VAR1 && -f $VAR2 && -f $VAR3 ]]
 then  ....

or even

 if [ -f $VAR1 -a -f $VAR2 -a -f $VAR3 ]
 then  ....

You can find further details in this question bash : Multiple Unary operators in if statement and some references given there like What is the difference between test, [ and [[ ?.

Table 'performance_schema.session_variables' doesn't exist

The mysql_upgrade worked for me as well:

# mysql_upgrade -u root -p --force
# systemctl restart mysqld

Regards, MSz.

How do I create a new line in Javascript?

your solution is

var i;
for(i=10; i>=0; i= i-1){
   var s;
   for(s=0; s<i; s = s+1){
   //printing new line

Maven in Eclipse: step by step installation

Check This

instead to avoid this error:

Cannot complete the install because one or more required items could not be found. Software being installed: m2e - slf4j over logback logging (Optional) ( Missing requirement: Maven Integration for Eclipse (org.eclipse.m2e.core requires 'bundle [14.0.1,16.0.0)' but it could not be found Missing requirement: Maven Integration for Eclipse (org.eclipse.m2e.core requires 'bundle org.eclipse.osgi 3.10.0' but it could not be found Cannot satisfy dependency: From: Maven Integration for Eclipse (org.eclipse.m2e.core.ui To: bundle org.eclipse.m2e.core [1.6.0,1.7.0) Cannot satisfy dependency: From: Maven Integration for Eclipse (org.eclipse.m2e.core.ui To: bundle org.eclipse.m2e.core [1.6.0,1.7.0) Cannot satisfy dependency: From: m2e logback appender (org.eclipse.m2e.logback.appender To: bundle org.eclipse.m2e.core.ui [1.6.0,1.7.0) Cannot satisfy dependency: From: m2e - slf4j over logback logging (Optional) ( To: org.eclipse.m2e.logback.appender []


Error : java.lang.NoSuchMethodError: org.objectweb.asm.ClassWriter.<init>(I)V

You have an incompatibility between the version of ASM required by Hibernate (asm-1.5.3.jar) and the one required by Spring. But, actually, I wonder why you have asm-2.2.3.jar on your classpath (ASM is bundled in spring.jar and spring-core.jar to avoid such problems AFAIK). See HHH-2222.

Angular and debounce

HTML file:

<input [ngModel]="filterValue"
       (ngModelChange)="filterValue = $event ; search($event)"

TS file:

timer = null;
time = 250;
  search(searchStr : string) : void {
    this.timer = setTimeout(()=>{
    }, time)

How do I insert values into a Map<K, V>?

There are two issues here.

Firstly, you can't use the [] syntax like you may be able to in other languages. Square brackets only apply to arrays in Java, and so can only be used with integer indexes.

data.put is correct but that is a statement and so must exist in a method block. Only field declarations can exist at the class level. Here is an example where everything is within the local scope of a method:

public class Data {
     public static void main(String[] args) {
         Map<String, String> data = new HashMap<String, String>();
         data.put("John", "Taxi Driver");
         data.put("Mark", "Professional Killer");

If you want to initialize a map as a static field of a class then you can use Map.of, since Java 9:

public class Data {
    private static final Map<String, String> DATA = Map.of("John", "Taxi Driver");

Before Java 9, you can use a static initializer block to accomplish the same thing:

public class Data {
    private static final Map<String, String> DATA = new HashMap<>();

    static {
        DATA.put("John", "Taxi Driver");

Import error No module named skimage

For python 3.5 in case you have multiple python versions and want to install with python3.5:

pip3 install scikit-image --user

How to see the actual Oracle SQL statement that is being executed

On the data dictionary side there are a lot of tools you can use to such as Schema Spy

To look at what queries are running look at views sys.v_$sql and sys.v_$sqltext. You will also need access to sys.all_users

One thing to note that queries that use parameters will show up once with entries like

and TABLETYPE=’:b16’

while others that dont will show up multiple times such as:


An example of these tables in action is the following SQL to find the top 20 diskread hogs. You could change this by removing the WHERE rownum <= 20 and maybe add ORDER BY module. You often find the module will give you a bog clue as to what software is running the query (eg: "TOAD", "JDBC Thin Client", "runcbl@somebox (TNS V1-V3)" etc)

   sql_text , 
   u.username , 
   round((s.disk_reads/decode(s.executions,0,1, s.executions)),2)  disk_reads_per_exec, 
   s.disk_reads , 
   s.buffer_gets , 
   s.parse_calls , 
   s.sorts , 
   s.executions , 
   s.rows_processed , 
   100 - round(100 *  s.disk_reads/greatest(s.buffer_gets,1),2) hit_ratio, 
   s.first_load_time , 
   sharable_mem , 
   persistent_mem , 
   sys.v_$sql s, 
   sys.all_users u 
   and UPPER(u.username) not in ('SYS','SYSTEM') 
   4 desc) 
 rownum <= 20;

Note that if the query is long .. you will have to query v_$sqltext. This stores the whole query. You will have to look up the ADDRESS and HASH_VALUE and pick up all the pieces. Eg:

 address = 'C0000000372B3C28'
 and hash_value = '1272580459'
 address, hash_value, command_type, piece

How to set bot's status

Use this:

client.user.setActivity("with depression", {
  type: "STREAMING",
  url: ""

Android XML Percent Symbol

To allow the app using formatted strings from resources you should correct your xml. So, for example

<string name="app_name">Your App name, ver.%d</string>

should be replaced with

<string name="app_name">Your App name, ver.%1$d</string>

You can see this for details.

python date of the previous month

There is a high level library dateparser that can determine the past date given natural language, and return the corresponding Python datetime object

from dateparser import parse
parse('4 months ago')

How can I create a text box for a note in markdown?

The following methods work on GitHub, on GitLab... and on Stackoverflow, which now uses CommonMark!

> One-Line Box made with Blockquote

One-Line Box made with Blockquote

`One-Line Box made with Backticks`

One-Line Box made with Backticks

Box made with Triple Backticks

Box made with Triple Backticks  

~ ~ ~
Box made with Triple Tildes
(remove the spaces between the tildes to make this work)
~ ~ ~

Box made with Triple Tildes

Box made with Four Spaces at the start of each line:

    “Sometimes we must let go of our pride and do what is requested of us.”
    Padmé Amidala

... or use horizontal lines?

Three dashes (---) make a horizontal line:

Note: “ Your focus determines your reality.” – Qui-Gon Jinn.

For more configurations, I strongly advise the excellent GitLab Markdown Guide.
You can also check the less detailed GitHub basic formatting syntax.
You can compare Markdown implementations using Babelmark.

Useful hints :

  • to force a newline, put two spaces at the end of the line;

  • to escape special characters, use \.

MSOnline can't be imported on PowerShell (Connect-MsolService error)

I'm using a newer version of the SPO Management Shell. For me to get the error to go away, I changed my Import-Module statement to use:

Import-Module Microsoft.Online.SharePoint.PowerShell -DisableNameChecking;

I also use the newer command:


Check if value exists in enum in TypeScript

TypeScript v3.7.3

export enum YourEnum {
   enum1 = 'enum1',
   enum2 = 'enum2',
   enum3 = 'enum3',

const status = 'enumnumnum';

if (!(status in YourEnum)) {
     throw new UnprocessableEntityResponse('Invalid enum val');

Convert floats to ints in Pandas?

Considering the following data frame:

>>> df = pd.DataFrame(10*np.random.rand(3, 4), columns=list("ABCD"))
>>> print(df)
...           A         B         C         D
... 0  8.362940  0.354027  1.916283  6.226750
... 1  1.988232  9.003545  9.277504  8.522808
... 2  1.141432  4.935593  2.700118  7.739108

Using a list of column names, change the type for multiple columns with applymap():

>>> cols = ['A', 'B']
>>> df[cols] = df[cols].applymap(np.int64)
>>> print(df)
...    A  B         C         D
... 0  8  0  1.916283  6.226750
... 1  1  9  9.277504  8.522808
... 2  1  4  2.700118  7.739108

Or for a single column with apply():

>>> df['C'] = df['C'].apply(np.int64)
>>> print(df)
...    A  B  C         D
... 0  8  0  1  6.226750
... 1  1  9  9  8.522808
... 2  1  4  2  7.739108

AttributeError: 'str' object has no attribute

The problem is in your playerMovement method. You are creating the string name of your room variables (ID1, ID2, ID3):

letsago = "ID" + str(self.dirDesc.values())

However, what you create is just a str. It is not the variable. Plus, I do not think it is doing what you think its doing:


If you REALLY needed to find the variable this way, you could use the eval function:

>>>foo = 'Hello World!'
'Hello World!'

or the globals function:

class Foo(object):
    def __init__(self):
        super(Foo, self).__init__()
    def test(self, name):

foo = Foo()
bar = 'Hello World!'

However, instead I would strongly recommend you rethink you class(es). Your userInterface class is essentially a Room. It shouldn't handle player movement. This should be within another class, maybe GameManager or something like that.

Round up to Second Decimal Place in Python

def round_up(number, ndigits=None):
    # start by just rounding the number, as sometimes this rounds it up
    result = round(number, ndigits if ndigits else 0)
    if result < number:
        # whoops, the number was rounded down instead, so correct for that
        if ndigits:
            # use the type of number provided, e.g. float, decimal, fraction
            Numerical = type(number)
            # add the digit 1 in the correct decimal place
            result += Numerical(10) ** -ndigits
            # may need to be tweaked slightly if the addition was inexact
            result = round(result, ndigits)
            result += 1 # same as 10 ** -0 for precision of zero digits
    return result

assert round_up(0.022499999999999999, 2) == 0.03
assert round_up(0.1111111111111000, 2) == 0.12

assert round_up(1.11, 2) == 1.11
assert round_up(1e308, 2) == 1e308

"This SqlTransaction has completed; it is no longer usable."... configuration error?

I have recently ran across similar situation. To debug in any VS IDE version, open exceptions from Debug (Ctrl + D, E) - check all checkboxes against the column "Thrown", and run the application in debug mode. I have realized that one of the tables was not imported properly in the new database, so internal Sql Exception was killing the connection, thus results into this error.

Gist of the story is, If Previously working code returns this error on a new database, this could be database schema missing issue, realize by above debugging tip,

Hope It Helps, HydTechie

How to prevent form from submitting multiple times from client side?

<form action='' id='theform' >
<div class='row'>
    <div class="form-group col-md-4">
            <label for="name">Name:</label>
            <input type='text' name='name' class='form-control'/>
<div class='row'>
    <div class="form-group col-md-4">
            <label for="email">Email:</label>
            <input type='text' name='email' class='form-control'/>
<div class='row'>
    <div class="form-group col-md-4">
         <input class='btn btn-primary pull-right' type="button" value="Submit" id='btnsubmit' />   


        $(this).val('Please wait ...')


Why are elementwise additions much faster in separate loops than in a combined loop?

OK, the right answer definitely has to do something with the CPU cache. But to use the cache argument can be quite difficult, especially without data.

There are many answers, that led to a lot of discussion, but let's face it: Cache issues can be very complex and are not one dimensional. They depend heavily on the size of the data, so my question was unfair: It turned out to be at a very interesting point in the cache graph.

@Mysticial's answer convinced a lot of people (including me), probably because it was the only one that seemed to rely on facts, but it was only one "data point" of the truth.

That's why I combined his test (using a continuous vs. separate allocation) and @James' Answer's advice.

The graphs below shows, that most of the answers and especially the majority of comments to the question and answers can be considered completely wrong or true depending on the exact scenario and parameters used.

Note that my initial question was at n = 100.000. This point (by accident) exhibits special behavior:

  1. It possesses the greatest discrepancy between the one and two loop'ed version (almost a factor of three)

  2. It is the only point, where one-loop (namely with continuous allocation) beats the two-loop version. (This made Mysticial's answer possible, at all.)

The result using initialized data:

Enter image description here

The result using uninitialized data (this is what Mysticial tested):

Enter image description here

And this is a hard-to-explain one: Initialized data, that is allocated once and reused for every following test case of different vector size:

Enter image description here


Every low-level performance related question on Stack Overflow should be required to provide MFLOPS information for the whole range of cache relevant data sizes! It's a waste of everybody's time to think of answers and especially discuss them with others without this information.

Change NULL values in Datetime format to empty string

Select isnull(date_column_name,cast('1900-01-01' as DATE)) from table name

Git pull command from different user

Your question is a little unclear, but if what you're doing is trying to get your friend's latest changes, then typically what your friend needs to do is to push those changes up to a remote repo (like one hosted on GitHub), and then you fetch or pull those changes from the remote:

  1. Your friend pushes his changes to GitHub:

    git push origin <branch>
  2. Clone the remote repository if you haven't already:

    git clone https://[email protected]/abc/theproject.git
  3. Fetch or pull your friend's changes (unnecessary if you just cloned in step #2 above):

    git fetch origin
    git merge origin/<branch>

    Note that git pull is the same as doing the two steps above:

    git pull origin <branch>

See Also

Can you overload controller methods in ASP.NET MVC?

No,No and No. Go and try the controller code below where we have the "LoadCustomer" overloaded.

public class CustomerController : Controller
        // GET: /Customer/

        public ActionResult LoadCustomer()
            return Content("LoadCustomer");
        public ActionResult LoadCustomer(string str)
            return Content("LoadCustomer with a string");

If you try to invoke the "LoadCustomer" action you will get error as shown in the below figure.

enter image description here

Polymorphism is a part of C# programming while HTTP is a protocol. HTTP does not understand polymorphism. HTTP works on the concept's or URL and URL can only have unique name's. So HTTP does not implement polymorphism.

In order to fix the same we need to use "ActionName" attribute.

public class CustomerController : Controller
        // GET: /Customer/

        public ActionResult LoadCustomer()
            return Content("LoadCustomer");

        public ActionResult LoadCustomer(string str)
            return Content("LoadCustomer with a string");

So now if you make a call to URL "Customer/LoadCustomer" the "LoadCustomer" action will be invoked and with URL structure "Customer/LoadCustomerByName" the "LoadCustomer(string str)" will be invoked.

enter image description here

enter image description here

The above answer i have taken from this codeproject article --> MVC Action overloading

Cannot declare instance members in a static class in C#

Have you tried using the 'static' storage class similar to?:

public static class employee
    static NameValueCollection appSetting = ConfigurationManager.AppSettings;    

How to delete a cookie using jQuery?

To delete a cookie with JQuery, set the value to null:

$.cookie("name", null, { path: '/' });

Edit: The final solution was to explicitly specify the path property whenever accessing the cookie, because the OP accesses the cookie from multiple pages in different directories, and thus the default paths were different (this was not described in the original question). The solution was discovered in discussion below, which explains why this answer was accepted - despite not being correct.

For some versions jQ cookie the solution above will set the cookie to string null. Thus not removing the cookie. Use the code as suggested below instead.

$.removeCookie('the_cookie', { path: '/' });

Make file echo displaying "$PATH" string

In the manual for GNU make, they talk about this specific example when describing the value function:

The value function provides a way for you to use the value of a variable without having it expanded. Please note that this does not undo expansions which have already occurred; for example if you create a simply expanded variable its value is expanded during the definition; in that case the value function will return the same result as using the variable directly.

The syntax of the value function is:

 $(value variable)

Note that variable is the name of a variable; not a reference to that variable. Therefore you would not normally use a ‘$’ or parentheses when writing it. (You can, however, use a variable reference in the name if you want the name not to be a constant.)

The result of this function is a string containing the value of variable, without any expansion occurring. For example, in this makefile:


         @echo $(FOO)
         @echo $(value FOO)

The first output line would be ATH, since the “$P” would be expanded as a make variable, while the second output line would be the current value of your $PATH environment variable, since the value function avoided the expansion.

Why won't eclipse switch the compiler to Java 8?

Old question, but posting the answer incase it helps someone. Already build path was configured to use JDK 1.2.81 However, build was failing with the error below:

 lambda expressions are not supported in -source 1.5
[ERROR]   (use -source 8 or higher to enable lambda expressions)

In the latest Eclipse (Photon), adding the below entry to pom.xml worked.


SQL Server 100% CPU Utilization - One database shows high CPU usage than others

You can see some reports in SSMS:

Right-click the instance name / reports / standard / top sessions

You can see top CPU consuming sessions. This may shed some light on what SQL processes are using resources. There are a few other CPU related reports if you look around. I was going to point to some more DMVs but if you've looked into that already I'll skip it.

You can use sp_BlitzCache to find the top CPU consuming queries. You can also sort by IO and other things as well. This is using DMV info which accumulates between restarts.

This article looks promising.

Some stackoverflow goodness from Mr. Ozar.

edit: A little more advice... A query running for 'only' 5 seconds can be a problem. It could be using all your cores and really running 8 cores times 5 seconds - 40 seconds of 'virtual' time. I like to use some DMVs to see how many executions have happened for that code to see what that 5 seconds adds up to.

How do I open multiple instances of Visual Studio Code?

Multiple instances of the same project


You cannot open multiple instances of the same folder but a workaround I have found is to open different folders.


So, here I might open components, models and tests in different windows and then I can view them on my three monitors.

It sounds a bit simple but this has helped me a lot.

Java, How to get number of messages in a topic in apache kafka

Run the following (assuming is on the path):  --from-beginning \
--bootstrap-server yourbroker:9092 --property print.key=true  \
--property print.value=false --property print.partition \
--topic yourtopic --timeout-ms 5000 | tail -n 10|grep "Processed a total of"

Search for exact match of string in excel row using VBA Macro

Try this:

Sub GetColumns()

Dim lnRow As Long, lnCol As Long

lnRow = 3 'For testing

lnCol = Sheet1.Cells(lnRow, 1).EntireRow.Find(What:="sds", LookIn:=xlValues, LookAt:=xlPart, SearchOrder:=xlByColumns, SearchDirection:=xlNext, MatchCase:=False).Column

End Sub

Probably best not to use colIndex and rowIndex as variable names as they are already mentioned in the Excel Object Library.

The SELECT permission was denied on the object 'Users', database 'XXX', schema 'dbo'

I think the problem is with the user having deny privileges. This error comes when the user which you have created does not have the sufficient privileges to access your tables in the database. Do grant the privilege to the user in order to get what you want.

GRANT the user specific permissions such as SELECT, INSERT, UPDATE and DELETE on tables in that database.

Difference between variable declaration syntaxes in Javascript (including global variables)?

    var varDeclaration = true;
    noVarDeclaration = true;
    window.hungOnWindow = true;
    document.hungOnDocument = true;
<script src="external.js"></script>

/* external.js */ == true); // could be .log, alert etc
// returns false in IE8 == true); // could be .log, alert etc
// returns false in IE8 == true); // could be .log, alert etc
// returns true in IE8 == true); // could be .log, alert etc
// returns ??? in IE8 (untested!)  *I personally find this more clugy than hanging off window obj

Is there a global object that all vars are hung off of by default? eg: 'globals.noVar declaration'

HTML input time in 24 format

<!DOCTYPE html>_x000D_
        Time: <input type="time" id="myTime" value="16:32:55">_x000D_
 <p>Click the button to get the time of the time field.</p>_x000D_
 <button onclick="myFunction()">Try it</button>_x000D_
 <p id="demo"></p>_x000D_
     function myFunction() {_x000D_
         var x = document.getElementById("myTime").value;_x000D_
         document.getElementById("demo").innerHTML = x;_x000D_

I found that by setting value field (not just what is given below) time input will be internally converted into the 24hr format.


From [Hive Language Manual][1]:

COALESCE (T v1, T v2, ...)

Will return the first value that is not NULL, or NULL if all values's are NULL

How to check if dropdown is disabled?

Try following or check demo disabled and readonly

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

You can check jQuery FAQ .

Set the space between Elements in Row Flutter


start - Place the children as close to the start of the main axis as possible.

enter image description here

end - Place the children as close to the end of the main axis as possible.

enter image description here

center - Place the children as close to the middle of the main axis as possible.

enter image description here

spaceBetween - Place the free space evenly between the children.

enter image description here

spaceAround - Place the free space evenly between the children as well as half of that space before and after the first and last child.

enter image description here

spaceEvenly - Place the free space evenly between the children as well as before and after the first and last child.

enter image description here


  child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: <Widget>[

Write to file, but overwrite it if it exists

Despite NylonSmile's answer, which is "sort of" correct.. I was unable to overwrite files, in this manner..

echo "i know about Pipes, girlfriend" > thatAnswer

zsh: file exists: thatAnswer

to solve my issues.. I had to use... >!, á la..

[[ $FORCE_IT == 'YES' ]] && echo "$@" >! "$X" || echo "$@" > "$X"

Obviously, be careful with this...

How can I check if a URL exists via PHP?

function URLIsValid($URL)
    $exists = true;
    $file_headers = @get_headers($URL);
    $InvalidHeaders = array('404', '403', '500');
    foreach($InvalidHeaders as $HeaderVal)
            if(strstr($file_headers[0], $HeaderVal))
                    $exists = false;
    return $exists;

Maximum concurrent connections to MySQL

I can assure you that raw speed ultimately lies in the non-standard use of Indexes for blazing speed using large tables.

How do I check the operating system in Python?

More detailed information are available in the platform module.

How to open a new window on form submit doesn't work across all browsers, Google it and you will find a way of detecting the correct dialog type.

Also, move the onclick call to the input button for it to only fire when the user submits.

How do I find the data directory for a SQL Server instance?

Even though this is a very old thread, I feel like I need to contribute a simple solution. Any time that you know where in Management Studio a parameter is located that you want to access for any sort of automated script, the easiest way is to run a quick profiler trace on a standalone test system and capture what Management Studio is doing on the backend.

In this instance, assuming you are interested in finding the default data and log locations you can do the following:

     SERVERPROPERTY('instancedefaultdatapath') AS [DefaultFile],
     SERVERPROPERTY('instancedefaultlogpath') AS [DefaultLog]

JavaScript: set dropdown selected item based on option text

This works in latest Chrome, FireFox and Edge, but not IE11:

document.evaluate('//option[text()="Yahoo"]', document).iterateNext().selected = 'selected';

And if you want to ignore spaces around the title:

document.evaluate('//option[normalize-space(text())="Yahoo"]', document).iterateNext().selected = 'selected'

Laravel 4: how to run a raw SQL?

Laravel raw sql – Insert query:

lets create a get link to insert data which is accessible through url . so our link name is ‘insertintodb’ and inside that function we use db class . db class helps us to interact with database . we us db class static function insert . Inside insert function we will write our PDO query to insert data in database . in below query we will insert ‘ my title ‘ and ‘my content’ as data in posts table .

put below code in your web.php file inside routes directory :

DB::insert('insert into posts(title,content) values (?,?)',['my title','my content']);

Now fire above insert query from browser link below :


You can see output of above insert query by going into your database table .you will find a record with id 1 .

Laravel raw sql – Read query :

Now , lets create a get link to read data , which is accessible through url . so our link name is ‘readfromdb’. we us db class static function read . Inside read function we will write our PDO query to read data from database . in below query we will read data of id ‘1’ from posts table .

put below code in your web.php file inside routes directory :

Route::get('/readfromdb',function() {
    $result =  DB::select('select * from posts where id = ?', [1]);

now fire above read query from browser link below :


Return from lambda forEach() in java

You can also throw an exception:


For the sake of readability each step of stream should be listed in new line.
       .filter(player -> player.getName().contains(name))

if your logic is loosely "exception driven" such as there is one place in your code that catches all exceptions and decides what to do next. Only use exception driven development when you can avoid littering your code base with multiples try-catch and throwing these exceptions are for very special cases that you expect them and can be handled properly.)

setTimeout / clearTimeout problems

A way to use this in react:

class Timeout extends Component {

    this.state = {
      timeout: null


    const { timeout } = this.state;
      timeout: setTimeout(() => {this.callAPI()}, 250)


Helpful if you'd like to only call an API after the user has stopped typing for instance. The userTimeout function could be bound via onKeyUp to an input.

How to find the Git commit that introduced a string in any branch?

--reverse is also helpful since you want the first commit that made the change:

git log --all -p --reverse --source -S 'needle'

This way older commits will appear first.

How to check if a date is in a given range?

$startDatedt = strtotime($start_date)
$endDatedt = strtotime($end_date)
$usrDatedt = strtotime($date_from_user)

if( $usrDatedt >= $startDatedt && $usrDatedt <= $endDatedt)
   //..falls within range

How to set a variable to current date and date-1 in linux?

you should man date first

date +%Y-%m-%d
date +%Y-%m-%d -d yesterday

Underline text in UIlabel

People, who do not want to subclass the view (UILabel/UIButton) etc... 'forgetButton' can be replace by any lable too.

-(void) drawUnderlinedLabel {
    NSString *string = [forgetButton titleForState:UIControlStateNormal];
    CGSize stringSize = [string sizeWithFont:forgetButton.titleLabel.font];
    CGRect buttonFrame = forgetButton.frame;
    CGRect labelFrame = CGRectMake(buttonFrame.origin.x + buttonFrame.size.width - stringSize.width, 
            buttonFrame.origin.y + stringSize.height + 1 , 
            stringSize.width, 2);
    UILabel *lineLabel = [[UILabel alloc] initWithFrame:labelFrame];
    lineLabel.backgroundColor = [UIColor blackColor];
    //[forgetButton addSubview:lineLabel];
    [self.view addSubview:lineLabel];

Iterator Loop vs index loop

It always depends on what you need.

You should use operator[] when you need direct access to elements in the vector (when you need to index a specific element in the vector). There is nothing wrong in using it over iterators. However, you must decide for yourself which (operator[] or iterators) suits best your needs.

Using iterators would enable you to switch to other container types without much change in your code. In other words, using iterators would make your code more generic, and does not depend on a particular type of container.

Find records from one table which don't exist in another

SELECT Call.ID,, Call.phone_number 
FROM Call 
  ON (Call.phone_number=Phone_book.phone_number) 
  WHERE Phone_book.phone_number IS NULL

Should remove the subquery, allowing the query optimiser to work its magic.

Also, avoid "SELECT *" because it can break your code if someone alters the underlying tables or views (and it's inefficient).

Using Python's ftplib to get a directory listing, portably

I found my way here while trying to get filenames, last modified stamps, file sizes etc and wanted to add my code. It only took a few minutes to write a loop to parse the ftp.dir(dir_list.append) making use of python std lib stuff like strip() (to clean up the line of text) and split() to create an array.

ftp = FTP('sick.domain.bro')

dir_list = []

# main thing is identifing which char marks start of good stuff
# '-rw-r--r--   1 ppsrt    ppsrt      545498 Jul 23 12:07 FILENAME.FOO
#                               ^  (that is line[29])

for line in dir_list:
   print line[29:].strip().split(' ') # got yerself an array there bud!
   # EX ['545498', 'Jul', '23', '12:07', 'FILENAME.FOO']

How to POST a FORM from HTML to ASPX page

This is very possible. I mocked up 3 pages which should give you a proof of concept:

.aspx page:

<form id="form1" runat="server">
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <asp:TextBox TextMode="password" ID="TextBox2" runat="server"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" Text="Button" />

code behind:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    For Each s As String In Request.Form.AllKeys
        Response.Write(s & ": " & Request.Form(s) & "<br />")
End Sub

Separate HTML page:

<form action="http://localhost/MyTestApp/Default.aspx" method="post">
    <input name="TextBox1" type="text" value="" id="TextBox1" />
    <input name="TextBox2" type="password" id="TextBox2" />
    <input type="submit" name="Button1" value="Button" id="Button1" />

...and it regurgitates the form values as expected. If this isn't working, as others suggested, use a traffic analysis tool (fiddler, ethereal), because something probably isn't going where you're expecting.

Confirm button before running deleting routine from website

You can do it with an confirm() message using Javascript.

How to empty a list in C#?

You can use the clear method

List<string> test = new List<string>();

Is it possible to CONTINUE a loop from an exception?

How about the ole goto statement (i know, i know, but it works just fine here ;)

   v_attr char(88);
    FOR user_rec IN SELECT_USERS LOOP    
            SELECT attr INTO v_attr 
            WHERE user_id =;            
               -- user does not have attribute, continue loop to next record.
               goto end_loop;


Just put end_loop at very end of loop of course. The null can be substituted with a commit maybe or a counter increment maybe, up to you.

ASP.NET - How to write some html in the page? With Response.Write?

Use a literal control and write your html like this:

literal1.text = "<h2><p>Notify:</p> alert</h2>";

How to print float to n decimal places including trailing 0s?

I guess this is essentially putting it in a string, but this avoids the rounding error:

import decimal

def display(x):
    digits = 15
    temp = str(decimal.Decimal(str(x) + '0' * digits))
    return temp[:temp.find('.') + digits + 1]

How to comment/uncomment in HTML code

I find this to be the bane of XML style document commenting too. There are XML editors like eclipse that can perform block commenting. Basically automatically add extra per line and remove them. May be they made it purposefully hard to comment that style of document it was supposed to be self explanatory with the tags after all.

Bundler: Command not found

I think bundle executable is on :

/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/bin and it's not in your $PATH

How does PHP 'foreach' actually work?

foreach supports iteration over three different kinds of values:

In the following, I will try to explain precisely how iteration works in different cases. By far the simplest case is Traversable objects, as for these foreach is essentially only syntax sugar for code along these lines:

foreach ($it as $k => $v) { /* ... */ }

/* translates to: */

if ($it instanceof IteratorAggregate) {
    $it = $it->getIterator();
for ($it->rewind(); $it->valid(); $it->next()) {
    $v = $it->current();
    $k = $it->key();
    /* ... */

For internal classes, actual method calls are avoided by using an internal API that essentially just mirrors the Iterator interface on the C level.

Iteration of arrays and plain objects is significantly more complicated. First of all, it should be noted that in PHP "arrays" are really ordered dictionaries and they will be traversed according to this order (which matches the insertion order as long as you didn't use something like sort). This is opposed to iterating by the natural order of the keys (how lists in other languages often work) or having no defined order at all (how dictionaries in other languages often work).

The same also applies to objects, as the object properties can be seen as another (ordered) dictionary mapping property names to their values, plus some visibility handling. In the majority of cases, the object properties are not actually stored in this rather inefficient way. However, if you start iterating over an object, the packed representation that is normally used will be converted to a real dictionary. At that point, iteration of plain objects becomes very similar to iteration of arrays (which is why I'm not discussing plain-object iteration much in here).

So far, so good. Iterating over a dictionary can't be too hard, right? The problems begin when you realize that an array/object can change during iteration. There are multiple ways this can happen:

  • If you iterate by reference using foreach ($arr as &$v) then $arr is turned into a reference and you can change it during iteration.
  • In PHP 5 the same applies even if you iterate by value, but the array was a reference beforehand: $ref =& $arr; foreach ($ref as $v)
  • Objects have by-handle passing semantics, which for most practical purposes means that they behave like references. So objects can always be changed during iteration.

The problem with allowing modifications during iteration is the case where the element you are currently on is removed. Say you use a pointer to keep track of which array element you are currently at. If this element is now freed, you are left with a dangling pointer (usually resulting in a segfault).

There are different ways of solving this issue. PHP 5 and PHP 7 differ significantly in this regard and I'll describe both behaviors in the following. The summary is that PHP 5's approach was rather dumb and lead to all kinds of weird edge-case issues, while PHP 7's more involved approach results in more predictable and consistent behavior.

As a last preliminary, it should be noted that PHP uses reference counting and copy-on-write to manage memory. This means that if you "copy" a value, you actually just reuse the old value and increment its reference count (refcount). Only once you perform some kind of modification a real copy (called a "duplication") will be done. See You're being lied to for a more extensive introduction on this topic.


Internal array pointer and HashPointer

Arrays in PHP 5 have one dedicated "internal array pointer" (IAP), which properly supports modifications: Whenever an element is removed, there will be a check whether the IAP points to this element. If it does, it is advanced to the next element instead.

While foreach does make use of the IAP, there is an additional complication: There is only one IAP, but one array can be part of multiple foreach loops:

// Using by-ref iteration here to make sure that it's really
// the same array in both loops and not a copy
foreach ($arr as &$v1) {
    foreach ($arr as &$v) {
        // ...

To support two simultaneous loops with only one internal array pointer, foreach performs the following shenanigans: Before the loop body is executed, foreach will back up a pointer to the current element and its hash into a per-foreach HashPointer. After the loop body runs, the IAP will be set back to this element if it still exists. If however the element has been removed, we'll just use wherever the IAP is currently at. This scheme mostly-kinda-sort of works, but there's a lot of weird behavior you can get out of it, some of which I'll demonstrate below.

Array duplication

The IAP is a visible feature of an array (exposed through the current family of functions), as such changes to the IAP count as modifications under copy-on-write semantics. This, unfortunately, means that foreach is in many cases forced to duplicate the array it is iterating over. The precise conditions are:

  1. The array is not a reference (is_ref=0). If it's a reference, then changes to it are supposed to propagate, so it should not be duplicated.
  2. The array has refcount>1. If refcount is 1, then the array is not shared and we're free to modify it directly.

If the array is not duplicated (is_ref=0, refcount=1), then only its refcount will be incremented (*). Additionally, if foreach by reference is used, then the (potentially duplicated) array will be turned into a reference.

Consider this code as an example where duplication occurs:

function iterate($arr) {
    foreach ($arr as $v) {}

$outerArr = [0, 1, 2, 3, 4];

Here, $arr will be duplicated to prevent IAP changes on $arr from leaking to $outerArr. In terms of the conditions above, the array is not a reference (is_ref=0) and is used in two places (refcount=2). This requirement is unfortunate and an artifact of the suboptimal implementation (there is no concern of modification during iteration here, so we don't really need to use the IAP in the first place).

(*) Incrementing the refcount here sounds innocuous, but violates copy-on-write (COW) semantics: This means that we are going to modify the IAP of a refcount=2 array, while COW dictates that modifications can only be performed on refcount=1 values. This violation results in user-visible behavior change (while a COW is normally transparent) because the IAP change on the iterated array will be observable -- but only until the first non-IAP modification on the array. Instead, the three "valid" options would have been a) to always duplicate, b) do not increment the refcount and thus allowing the iterated array to be arbitrarily modified in the loop or c) don't use the IAP at all (the PHP 7 solution).

Position advancement order

There is one last implementation detail that you have to be aware of to properly understand the code samples below. The "normal" way of looping through some data structure would look something like this in pseudocode:

while (get_current_data(arr, &data) == SUCCESS) {

However foreach, being a rather special snowflake, chooses to do things slightly differently:

while (get_current_data(arr, &data) == SUCCESS) {

Namely, the array pointer is already moved forward before the loop body runs. This means that while the loop body is working on element $i, the IAP is already at element $i+1. This is the reason why code samples showing modification during iteration will always unset the next element, rather than the current one.

Examples: Your test cases

The three aspects described above should provide you with a mostly complete impression of the idiosyncrasies of the foreach implementation and we can move on to discuss some examples.

The behavior of your test cases is simple to explain at this point:

  • In test cases 1 and 2 $array starts off with refcount=1, so it will not be duplicated by foreach: Only the refcount is incremented. When the loop body subsequently modifies the array (which has refcount=2 at that point), the duplication will occur at that point. Foreach will continue working on an unmodified copy of $array.

  • In test case 3, once again the array is not duplicated, thus foreach will be modifying the IAP of the $array variable. At the end of the iteration, the IAP is NULL (meaning iteration has done), which each indicates by returning false.

  • In test cases 4 and 5 both each and reset are by-reference functions. The $array has a refcount=2 when it is passed to them, so it has to be duplicated. As such foreach will be working on a separate array again.

Examples: Effects of current in foreach

A good way to show the various duplication behaviors is to observe the behavior of the current() function inside a foreach loop. Consider this example:

foreach ($array as $val) {
/* Output: 2 2 2 2 2 */

Here you should know that current() is a by-ref function (actually: prefer-ref), even though it does not modify the array. It has to be in order to play nice with all the other functions like next which are all by-ref. By-reference passing implies that the array has to be separated and thus $array and the foreach-array will be different. The reason you get 2 instead of 1 is also mentioned above: foreach advances the array pointer before running the user code, not after. So even though the code is at the first element, foreach already advanced the pointer to the second.

Now lets try a small modification:

$ref = &$array;
foreach ($array as $val) {
/* Output: 2 3 4 5 false */

Here we have the is_ref=1 case, so the array is not copied (just like above). But now that it is a reference, the array no longer has to be duplicated when passing to the by-ref current() function. Thus current() and foreach work on the same array. You still see the off-by-one behavior though, due to the way foreach advances the pointer.

You get the same behavior when doing by-ref iteration:

foreach ($array as &$val) {
/* Output: 2 3 4 5 false */

Here the important part is that foreach will make $array an is_ref=1 when it is iterated by reference, so basically you have the same situation as above.

Another small variation, this time we'll assign the array to another variable:

$foo = $array;
foreach ($array as $val) {
/* Output: 1 1 1 1 1 */

Here the refcount of the $array is 2 when the loop is started, so for once we actually have to do the duplication upfront. Thus $array and the array used by foreach will be completely separate from the outset. That's why you get the position of the IAP wherever it was before the loop (in this case it was at the first position).

Examples: Modification during iteration

Trying to account for modifications during iteration is where all our foreach troubles originated, so it serves to consider some examples for this case.

Consider these nested loops over the same array (where by-ref iteration is used to make sure it really is the same one):

foreach ($array as &$v1) {
    foreach ($array as &$v2) {
        if ($v1 == 1 && $v2 == 1) {
        echo "($v1, $v2)\n";

// Output: (1, 1) (1, 3) (1, 4) (1, 5)

The expected part here is that (1, 2) is missing from the output because element 1 was removed. What's probably unexpected is that the outer loop stops after the first element. Why is that?

The reason behind this is the nested-loop hack described above: Before the loop body runs, the current IAP position and hash is backed up into a HashPointer. After the loop body it will be restored, but only if the element still exists, otherwise the current IAP position (whatever it may be) is used instead. In the example above this is exactly the case: The current element of the outer loop has been removed, so it will use the IAP, which has already been marked as finished by the inner loop!

Another consequence of the HashPointer backup+restore mechanism is that changes to the IAP through reset() etc. usually do not impact foreach. For example, the following code executes as if the reset() were not present at all:

$array = [1, 2, 3, 4, 5];
foreach ($array as &$value) {
// output: 1, 2, 3, 4, 5

The reason is that, while reset() temporarily modifies the IAP, it will be restored to the current foreach element after the loop body. To force reset() to make an effect on the loop, you have to additionally remove the current element, so that the backup/restore mechanism fails:

$array = [1, 2, 3, 4, 5];
$ref =& $array;
foreach ($array as $value) {
// output: 1, 1, 3, 4, 5

But, those examples are still sane. The real fun starts if you remember that the HashPointer restore uses a pointer to the element and its hash to determine whether it still exists. But: Hashes have collisions, and pointers can be reused! This means that, with a careful choice of array keys, we can make foreach believe that an element that has been removed still exists, so it will jump directly to it. An example:

$array = ['EzEz' => 1, 'EzFY' => 2, 'FYEz' => 3];
$ref =& $array;
foreach ($array as $value) {
    $array['FYFY'] = 4;
// output: 1, 4

Here we should normally expect the output 1, 1, 3, 4 according to the previous rules. How what happens is that 'FYFY' has the same hash as the removed element 'EzFY', and the allocator happens to reuse the same memory location to store the element. So foreach ends up directly jumping to the newly inserted element, thus short-cutting the loop.

Substituting the iterated entity during the loop

One last odd case that I'd like to mention, it is that PHP allows you to substitute the iterated entity during the loop. So you can start iterating on one array and then replace it with another array halfway through. Or start iterating on an array and then replace it with an object:

$arr = [1, 2, 3, 4, 5];
$obj = (object) [6, 7, 8, 9, 10];

$ref =& $arr;
foreach ($ref as $val) {
    echo "$val\n";
    if ($val == 3) {
        $ref = $obj;
/* Output: 1 2 3 6 7 8 9 10 */

As you can see in this case PHP will just start iterating the other entity from the start once the substitution has happened.


Hashtable iterators

If you still remember, the main problem with array iteration was how to handle removal of elements mid-iteration. PHP 5 used a single internal array pointer (IAP) for this purpose, which was somewhat suboptimal, as one array pointer had to be stretched to support multiple simultaneous foreach loops and interaction with reset() etc. on top of that.

PHP 7 uses a different approach, namely, it supports creating an arbitrary amount of external, safe hashtable iterators. These iterators have to be registered in the array, from which point on they have the same semantics as the IAP: If an array element is removed, all hashtable iterators pointing to that element will be advanced to the next element.

This means that foreach will no longer use the IAP at all. The foreach loop will be absolutely no effect on the results of current() etc. and its own behavior will never be influenced by functions like reset() etc.

Array duplication

Another important change between PHP 5 and PHP 7 relates to array duplication. Now that the IAP is no longer used, by-value array iteration will only do a refcount increment (instead of duplication the array) in all cases. If the array is modified during the foreach loop, at that point a duplication will occur (according to copy-on-write) and foreach will keep working on the old array.

In most cases, this change is transparent and has no other effect than better performance. However, there is one occasion where it results in different behavior, namely the case where the array was a reference beforehand:

$array = [1, 2, 3, 4, 5];
$ref = &$array;
foreach ($array as $val) {
    $array[2] = 0;
/* Old output: 1, 2, 0, 4, 5 */
/* New output: 1, 2, 3, 4, 5 */

Previously by-value iteration of reference-arrays was special cases. In this case, no duplication occurred, so all modifications of the array during iteration would be reflected by the loop. In PHP 7 this special case is gone: A by-value iteration of an array will always keep working on the original elements, disregarding any modifications during the loop.

This, of course, does not apply to by-reference iteration. If you iterate by-reference all modifications will be reflected by the loop. Interestingly, the same is true for by-value iteration of plain objects:

$obj = new stdClass;
$obj->foo = 1;
$obj->bar = 2;
foreach ($obj as $val) {
    $obj->bar = 42;
/* Old and new output: 1, 42 */

This reflects the by-handle semantics of objects (i.e. they behave reference-like even in by-value contexts).


Let's consider a few examples, starting with your test cases:

  • Test cases 1 and 2 retain the same output: By-value array iteration always keep working on the original elements. (In this case, even refcounting and duplication behavior is exactly the same between PHP 5 and PHP 7).

  • Test case 3 changes: Foreach no longer uses the IAP, so each() is not affected by the loop. It will have the same output before and after.

  • Test cases 4 and 5 stay the same: each() and reset() will duplicate the array before changing the IAP, while foreach still uses the original array. (Not that the IAP change would have mattered, even if the array was shared.)

The second set of examples was related to the behavior of current() under different reference/refcounting configurations. This no longer makes sense, as current() is completely unaffected by the loop, so its return value always stays the same.

However, we get some interesting changes when considering modifications during iteration. I hope you will find the new behavior saner. The first example:

$array = [1, 2, 3, 4, 5];
foreach ($array as &$v1) {
    foreach ($array as &$v2) {
        if ($v1 == 1 && $v2 == 1) {
        echo "($v1, $v2)\n";

// Old output: (1, 1) (1, 3) (1, 4) (1, 5)
// New output: (1, 1) (1, 3) (1, 4) (1, 5)
//             (3, 1) (3, 3) (3, 4) (3, 5)
//             (4, 1) (4, 3) (4, 4) (4, 5)
//             (5, 1) (5, 3) (5, 4) (5, 5) 

As you can see, the outer loop no longer aborts after the first iteration. The reason is that both loops now have entirely separate hashtable iterators, and there is no longer any cross-contamination of both loops through a shared IAP.

Another weird edge case that is fixed now, is the odd effect you get when you remove and add elements that happen to have the same hash:

$array = ['EzEz' => 1, 'EzFY' => 2, 'FYEz' => 3];
foreach ($array as &$value) {
    $array['FYFY'] = 4;
// Old output: 1, 4
// New output: 1, 3, 4

Previously the HashPointer restore mechanism jumped right to the new element because it "looked" like it's the same as the removed element (due to colliding hash and pointer). As we no longer rely on the element hash for anything, this is no longer an issue.

How to get number of rows using SqlDataReader in C#

You can't get a count of rows directly from a data reader because it's what is known as a firehose cursor - which means that the data is read on a row by row basis based on the read being performed. I'd advise against doing 2 reads on the data because there's the potential that the data has changed between doing the 2 reads, and thus you'd get different results.

What you could do is read the data into a temporary structure, and use that in place of the second read. Alternatively, you'll need to change the mechanism by which you retrieve the data and use something like a DataTable instead.

Defining custom attrs

Currently the best documentation is the source. You can take a look at it here (attrs.xml).

You can define attributes in the top <resources> element or inside of a <declare-styleable> element. If I'm going to use an attr in more than one place I put it in the root element. Note, all attributes share the same global namespace. That means that even if you create a new attribute inside of a <declare-styleable> element it can be used outside of it and you cannot create another attribute with the same name of a different type.

An <attr> element has two xml attributes name and format. name lets you call it something and this is how you end up referring to it in code, e.g., R.attr.my_attribute. The format attribute can have different values depending on the 'type' of attribute you want.

  • reference - if it references another resource id (e.g, "@color/my_color", "@layout/my_layout")
  • color
  • boolean
  • dimension
  • float
  • integer
  • string
  • fraction
  • enum - normally implicitly defined
  • flag - normally implicitly defined

You can set the format to multiple types by using |, e.g., format="reference|color".

enum attributes can be defined as follows:

<attr name="my_enum_attr">
  <enum name="value1" value="1" />
  <enum name="value2" value="2" />

flag attributes are similar except the values need to be defined so they can be bit ored together:

<attr name="my_flag_attr">
  <flag name="fuzzy" value="0x01" />
  <flag name="cold" value="0x02" />

In addition to attributes there is the <declare-styleable> element. This allows you to define attributes a custom view can use. You do this by specifying an <attr> element, if it was previously defined you do not specify the format. If you wish to reuse an android attr, for example, android:gravity, then you can do that in the name, as follows.

An example of a custom view <declare-styleable>:

<declare-styleable name="MyCustomView">
  <attr name="my_custom_attribute" />
  <attr name="android:gravity" />

When defining your custom attributes in XML on your custom view you need to do a few things. First you must declare a namespace to find your attributes. You do this on the root layout element. Normally there is only xmlns:android="". You must now also add xmlns:whatever="".


<?xml version="1.0" encoding="utf-8"?>

      whatever:my_custom_attribute="Hello, world!" />

Finally, to access that custom attribute you normally do so in the constructor of your custom view as follows.

public MyCustomView(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);

  TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.MyCustomView, defStyle, 0);

  String str = a.getString(R.styleable.MyCustomView_my_custom_attribute);

  //do something with str


The end. :)

How can I disable selected attribute from select2() dropdown Jquery?

As the question seems unclear, I'm sorry if this answer is not directly related to the original intent.

For those using Select2 version 4+ and according to official plugin documentation, .select2("enable")is not the way to go anymore for disabling the select box (not a single option of it). It will even be completely removed from version 4.1 onward.

Quoted directy from the documentation (see

Select2 will respect the disabled property of the underlying select element. In order to enable or disable Select2, you should call .prop('disabled', true/false) on the element. Support for the old methods will be completely removed in Select2 4.1.

So in the previous answer's example, it should be: $('select').prop(disabled,true);

Angular.js and HTML5 date input value -- how to get Firefox to show a readable date value in a date input?

I've used ng-change:

Date.prototype.addDays = function(days) {_x000D_
  var dat = new Date(this.valueOf());_x000D_
  dat.setDate(dat.getDate() + days);_x000D_
  return dat;_x000D_
var app = angular.module('myApp', []);_x000D_
app.controller('DateController', ['$rootScope', '$scope',_x000D_
  function($rootScope, $scope) {_x000D_
    function init() {_x000D_
      $scope.startDate = new Date();_x000D_
      $scope.endDate = $scope.startDate.addDays(14);_x000D_
    function load() {_x000D_
    // public methods_x000D_
    $scope.load = load;_x000D_
    $scope.setStart = function(date) {_x000D_
      $scope.startDate = date;_x000D_
    $scope.setEnd = function(date) {_x000D_
      $scope.endDate = date;_x000D_
<script src=""></script>_x000D_
<div data-ng-controller="DateController">_x000D_
  <label class="item-input"> <span class="input-label">Start</span>_x000D_
    <input type="date" data-ng-model="startDate" ng-change="setStart(startDate)" required validatedateformat calendar>_x000D_
  <label class="item-input"> <span class="input-label">End</span>_x000D_
    <input type="date" data-ng-model="endDate" ng-change="setEnd(endDate)" required validatedateformat calendar>_x000D_
  <button button="button" ng-disabled="planningForm.$invalid" ng-click="load()" class="button button-positive">_x000D_
</div <label class="item-input"> <span class="input-label">Start</span>_x000D_
<input type="date" data-ng-model="startDate" ng-change="setStart(startDate)" required validatedateformat calendar>_x000D_
<label class="item-input"> <span class="input-label">End</span>_x000D_
  <input type="date" data-ng-model="endDate" ng-change="setEnd(endDate)" required validatedateformat calendar>_x000D_

git ignore all files of a certain type, except those in a specific subfolder

An optional prefix ! which negates the pattern; any matching file excluded by a previous pattern will become included again. If a negated pattern matches, this will override lower precedence patterns sources.


Use of for_each on map elements

It's unfortunate that you don't have Boost however if your STL implementation has the extensions then you can compose mem_fun_ref and select2nd to create a single functor suitable for use with for_each. The code would look something like this:

#include <algorithm>
#include <map>
#include <ext/functional>   // GNU-specific extension for functor classes missing from standard STL

using namespace __gnu_cxx;  // for compose1 and select2nd

class MyClass
    void Method() const;

std::map<int, MyClass> Map;

int main(void)
    std::for_each(Map.begin(), Map.end(), compose1(std::mem_fun_ref(&MyClass::Method), select2nd<std::map<int, MyClass>::value_type>()));

Note that if you don't have access to compose1 (or the unary_compose template) and select2nd, they are fairly easy to write.

Using CSS td width absolute, position

Try this it work.

<td width="300">need 300px</td>

Favicon: .ico or .png / correct tags?

For compatibility with all browsers stick with .ico.

.png is getting more and more support though as it is easier to create using multiple programs.

for .ico

<link rel="shortcut icon" href="" />

for .png, you need to specify the type

<link rel="icon" type="image/png" href="" />

iOS9 Untrusted Enterprise Developer with no option to trust

Device: iPad Mini

OS: iOS 9 Beta 3

App downloaded from: Hockey App

Provisioning profile with Trust issues: Enterprise

In my case, when I navigate to Settings > General > Profiles, I could not see on any Apple provisioning profile. All I could see is a Configuration Profile which is HockeyApp Config.


Here are the steps that I followed:

  1. Connect the Device
  2. Open Xcode
  3. Navigate to Window > Devices
  4. Right click on the Device and select Show Provisioning Profiles...
  5. Delete your Enterprise provisioning profile. Hit Done. Window>Device>Provisioning Profile
  6. Open HockeyApp. Install your app.
  7. Once the app finished installing, go back to Settings>General>Profiles. You should now be able to see your Enterprise provisioning profile. enter image description here
  8. Click Trust enter image description here

That's it! You're done! You can now go back to your app and open it successfully. Hope this helped. :)

How can I generate a random number in a certain range?

You can use If Random. For example, this generates a random number between 75 to 100.

final int random = new Random().nextInt(26) + 75;

Converting from longitude\latitude to Cartesian coordinates

Coordinate[] coordinates = new Coordinate[3];
coordinates[0] = new Coordinate(102, 26);
coordinates[1] = new Coordinate(103, 25.12);
coordinates[2] = new Coordinate(104, 16.11);
CoordinateSequence coordinateSequence = new CoordinateArraySequence(coordinates);

Geometry geo = new LineString(coordinateSequence, geometryFactory);

CoordinateReferenceSystem wgs84 = DefaultGeographicCRS.WGS84;
CoordinateReferenceSystem cartesinaCrs = DefaultGeocentricCRS.CARTESIAN;

MathTransform mathTransform = CRS.findMathTransform(wgs84, cartesinaCrs, true);

Geometry geo1 = JTS.transform(geo, mathTransform);

C# Lambda expressions: Why should I use them?

This is just one way of using a lambda expression. You can use a lambda expression anywhere you can use a delegate. This allows you to do things like this:

List<string> strings = new List<string>();

strings.Find(s => s == "hello");

This code will search the list for an entry that matches the word "hello". The other way to do this is to actually pass a delegate to the Find method, like this:

List<string> strings = new List<string>();

private static bool FindHello(String s)
    return s == "hello";



In C# 2.0, this could be done using the anonymous delegate syntax:

  strings.Find(delegate(String s) { return s == "hello"; });

Lambda's significantly cleaned up that syntax.

Pass variables from servlet to jsp

You can also use RequestDispacher and pass on the data along with the jsp page you want.

request.setAttribute("MyData", data);
RequestDispatcher rd = request.getRequestDispatcher("page.jsp");
rd.forward(request, response);

Java - How to access an ArrayList of another class?

You can do this by providing in class numbers:

  • A method that returns the ArrayList object itself.
  • A method that returns a non-modifiable wrapper of the ArrayList. This prevents modification to the list without the knowledge of the class numbers.
  • Methods that provide the set of operations you want to support from class numbers. This allows class numbers to control the set of operations supported.

By the way, there is a strong convention that Java class names are uppercased.

Case 1 (simple getter):

public class Numbers {
      private List<Integer> list;
      public List<Integer> getList() { return list; }

Case 2 (non-modifiable wrapper):

public class Numbers {
      private List<Integer> list;
      public List<Integer> getList() { return Collections.unmodifiableList( list ); }

Case 3 (specific methods):

public class Numbers {
      private List<Integer> list;
      public void addToList( int i ) { list.add(i); }
      public int getValueAtIndex( int index ) { return list.get( index ); }

How to run multiple DOS commands in parallel?

I suggest you to see "How do I run a bat file in the background from another bat file?"

Also, good answer (of using start command) was given in "Parallel execution of shell processes" question page here;

But my recommendation is to use PowerShell. I believe it will perfectly suit your needs.

SyntaxError: unexpected EOF while parsing

This can simply also mean you are missing or have too many parentheses. For example this has too many, and will result in unexpected EOF:

print(9, not (a==7 and b==6)

Flatten List in LINQ

With query syntax:

var values =
from inner in outer
from value in inner
select value;

Delete all the queues from RabbitMQ?

In Rabbit version 3.7.10 you can run below command with root permission:

rabbitmqctl list_queues | awk '{ print $1 }' | xargs -L1 rabbitmqctl delete_queue

Getting Exception(org.apache.poi.openxml4j.exception - no content type [M1.13]) when reading xlsx file using Apache POI?

Cleaned up the code (commented out the logger mostly) to make it run in my Eclipse environment.

import java.util.Iterator;

import org.apache.poi.hssf.usermodel.HSSFDateUtil;
import org.apache.poi.xssf.usermodel.*;

public class ReadXLSX {
private String filepath;
private XSSFWorkbook workbook;
// private static Logger logger=null;
private InputStream resourceAsStream;

public ReadXLSX(String filePath) {
    // logger=LoggerFactory.getLogger("ReadXLSX");
    this.filepath = filePath;
    resourceAsStream = ClassLoader.getSystemResourceAsStream(filepath);

public ReadXLSX(InputStream fileStream) {
    // logger=LoggerFactory.getLogger("ReadXLSX");
    this.resourceAsStream = fileStream;

private void loadFile() throws FileNotFoundException,
        NullObjectFoundException {

    if (resourceAsStream == null)
        throw new FileNotFoundException("Unable to locate give file..");
    else {
        try {
            workbook = new XSSFWorkbook(resourceAsStream);

        } catch (IOException ex) {


}// end loadxlsFile

public String[] getSheetsName() {
    int totalsheet = 0;
    int i = 0;
    String[] sheetName = null;

    try {
        totalsheet = workbook.getNumberOfSheets();
        sheetName = new String[totalsheet];
        while (i < totalsheet) {
            sheetName[i] = workbook.getSheetName(i);

    } catch (FileNotFoundException ex) {
        // logger.error(ex);
    } catch (NullObjectFoundException ex) {
        // logger.error(ex);

    return sheetName;

public int[] getSheetsIndex() {
    int totalsheet = 0;
    int i = 0;
    int[] sheetIndex = null;
    String[] sheetname = getSheetsName();
    try {
        totalsheet = workbook.getNumberOfSheets();
        sheetIndex = new int[totalsheet];
        while (i < totalsheet) {
            sheetIndex[i] = workbook.getSheetIndex(sheetname[i]);

    } catch (FileNotFoundException ex) {
        // logger.error(ex);
    } catch (NullObjectFoundException ex) {
        // logger.error(ex);

    return sheetIndex;

private boolean validateIndex(int index) {
    if (index < getSheetsIndex().length && index >= 0)
        return true;
        return false;

public int getNumberOfSheet() {
    int totalsheet = 0;
    try {
        totalsheet = workbook.getNumberOfSheets();

    } catch (FileNotFoundException ex) {
        // logger.error(ex.getMessage());
    } catch (NullObjectFoundException ex) {
        // logger.error(ex.getMessage());

    return totalsheet;

public int getNumberOfColumns(int SheetIndex) {
    int NO_OF_Column = 0;
    XSSFCell cell = null;
    XSSFSheet sheet = null;
    try {
        loadFile(); // load give Excel
        if (validateIndex(SheetIndex)) {
            sheet = workbook.getSheetAt(SheetIndex);
            Iterator<Row> rowIter = sheet.rowIterator();
            XSSFRow firstRow = (XSSFRow);
            Iterator<Cell> cellIter = firstRow.cellIterator();
            while (cellIter.hasNext()) {
                cell = (XSSFCell);
        } else
            throw new InvalidSheetIndexException("Invalid sheet index.");
    } catch (Exception ex) {
        // logger.error(ex.getMessage());


    return NO_OF_Column;

public int getNumberOfRows(int SheetIndex) {
    int NO_OF_ROW = 0;
    XSSFSheet sheet = null;

    try {
        loadFile(); // load give Excel
        if (validateIndex(SheetIndex)) {
            sheet = workbook.getSheetAt(SheetIndex);
            NO_OF_ROW = sheet.getLastRowNum();
        } else
            throw new InvalidSheetIndexException("Invalid sheet index.");
    } catch (Exception ex) {
        // logger.error(ex);

    return NO_OF_ROW;

public String[] getSheetHeader(int SheetIndex) {
    int noOfColumns = 0;
    XSSFCell cell = null;
    int i = 0;
    String columns[] = null;
    XSSFSheet sheet = null;

    try {
        loadFile(); // load give Excel
        if (validateIndex(SheetIndex)) {
            sheet = workbook.getSheetAt(SheetIndex);
            noOfColumns = getNumberOfColumns(SheetIndex);
            columns = new String[noOfColumns];
            Iterator<Row> rowIter = sheet.rowIterator();
            XSSFRow Row = (XSSFRow);
            Iterator<Cell> cellIter = Row.cellIterator();

            while (cellIter.hasNext()) {
                cell = (XSSFCell);
                columns[i] = cell.getStringCellValue();
        } else
            throw new InvalidSheetIndexException("Invalid sheet index.");

    catch (Exception ex) {
        // logger.error(ex);

    return columns;
}// end of method

public String[][] getSheetData(int SheetIndex) {
    int noOfColumns = 0;
    XSSFRow row = null;
    XSSFCell cell = null;
    int i = 0;
    int noOfRows = 0;
    int j = 0;
    String[][] data = null;
    XSSFSheet sheet = null;

    try {
        loadFile(); // load give Excel
        if (validateIndex(SheetIndex)) {
            sheet = workbook.getSheetAt(SheetIndex);
            noOfColumns = getNumberOfColumns(SheetIndex);
            noOfRows = getNumberOfRows(SheetIndex) + 1;
            data = new String[noOfRows][noOfColumns];
            Iterator<Row> rowIter = sheet.rowIterator();
            while (rowIter.hasNext()) {
                row = (XSSFRow);
                Iterator<Cell> cellIter = row.cellIterator();
                j = 0;
                while (cellIter.hasNext()) {
                    cell = (XSSFCell);
                    if (cell.getCellType() == Cell.CELL_TYPE_STRING) {
                        data[i][j] = cell.getStringCellValue();
                    } else if (cell.getCellType() == Cell.CELL_TYPE_NUMERIC) {
                        if (HSSFDateUtil.isCellDateFormatted(cell)) {
                            String formatCellValue = new DataFormatter()
                            data[i][j] = formatCellValue;
                        } else {
                            data[i][j] = Double.toString(cell

                    } else if (cell.getCellType() == Cell.CELL_TYPE_BOOLEAN) {
                        data[i][j] = Boolean.toString(cell

                    else if (cell.getCellType() == Cell.CELL_TYPE_FORMULA) {
                        data[i][j] = cell.getCellFormula().toString();


            } // outer while

        } else
            throw new InvalidSheetIndexException("Invalid sheet index.");

    } catch (Exception ex) {
        // logger.error(ex);
    return data;

public String[][] getSheetData(int SheetIndex, int noOfRows) {
    int noOfColumns = 0;
    XSSFRow row = null;
    XSSFCell cell = null;
    int i = 0;
    int j = 0;
    String[][] data = null;
    XSSFSheet sheet = null;

    try {
        loadFile(); // load give Excel

        if (validateIndex(SheetIndex)) {
            sheet = workbook.getSheetAt(SheetIndex);
            noOfColumns = getNumberOfColumns(SheetIndex);
            data = new String[noOfRows][noOfColumns];
            Iterator<Row> rowIter = sheet.rowIterator();
            while (i < noOfRows) {

                row = (XSSFRow);
                Iterator<Cell> cellIter = row.cellIterator();
                j = 0;
                while (cellIter.hasNext()) {
                    cell = (XSSFCell);
                    if (cell.getCellType() == Cell.CELL_TYPE_STRING) {
                        data[i][j] = cell.getStringCellValue();
                    } else if (cell.getCellType() == Cell.CELL_TYPE_NUMERIC) {
                        if (HSSFDateUtil.isCellDateFormatted(cell)) {
                            String formatCellValue = new DataFormatter()
                            data[i][j] = formatCellValue;
                        } else {
                            data[i][j] = Double.toString(cell


            } // outer while
        } else
            throw new InvalidSheetIndexException("Invalid sheet index.");
    } catch (Exception ex) {
        // logger.error(ex);

    return data;

Created this little testcode:


public class ReadXLSXTest {

 * @param args
 * @throws FileNotFoundException 
public static void main(String[] args) throws FileNotFoundException {
    // TODO Auto-generated method stub

    ReadXLSX test = new ReadXLSX(new FileInputStream(new File("./sample.xlsx")));




All this ran like a charm, so my guess is you have an XLSX file that is 'corrupt' in one way or another. Try testing with other data.

Cheers, Wim

SQL Server Output Clause into a scalar variable

You need a table variable and it can be this simple.

declare @ID table (ID int)

insert into MyTable2(ID)
output inserted.ID into @ID
values (1)

How to print binary tree diagram?

See also these answers.

In particular it wasn't too difficult to use abego TreeLayout to produce results shown below with the default settings.

If you try that tool, note this caveat: It prints children in the order they were added. For a BST where left vs right matters I found this library to be inappropriate without modification.

Also, the method to add children simply takes a parent and child node as parameters. (So to process a bunch of nodes, you must take the first one separately to create a root.)

I ended up using this solution above, modifying it to take in the type <Node> so as to have access to Node's left and right (children).

tree created with abego TreeLayout

how to convert binary string to decimal?

Another implementation just for functional JS practicing could be

var bin2int = s =>, (p,c) => p*2 + +c)_x000D_
_x000D_ where +c coerces String type c to a Number type value for proper addition.

List Git aliases

Another alternative (purely something I find easy to remember):

git config --list | grep alias

jQuery table sort

@Nick Grealy's answer is great, but it does not take into account possible rowspan attributes of the table header cells (and probably the other answers don't do it either). Here is an improvement of the @Nick Grealy's answer which fixes that. Based on this answer too (thanks @Andrew Orlov).

I've also replaced the $.isNumeric function with a custom one (thanks @zad) to make it work with older jQuery versions.

To activate it, add class="sortable" to the <table> tag.

$(document).ready(function() {

    $('table.sortable th').click(function(){
        var table = $(this).parents('table').eq(0);
        var column_index = get_column_index(this);
        var rows = table.find('tbody tr').toArray().sort(comparer(column_index));
        this.asc = !this.asc;
        if (!this.asc){rows = rows.reverse()};
        for (var i = 0; i < rows.length; i++){table.append(rows[i])};


function comparer(index) {
    return function(a, b) {
        var valA = getCellValue(a, index), valB = getCellValue(b, index);
        return isNumber(valA) && isNumber(valB) ? valA - valB : valA.localeCompare(valB);
function getCellValue(row, index){ return $(row).children('td').eq(index).html() };

function isNumber(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);

function get_column_index(element) {
    var clickedEl = $(element);
    var myCol = clickedEl.closest("th").index();
    var myRow = clickedEl.closest("tr").index();
    var rowspans = $("th[rowspan]");
    rowspans.each(function () {
        var rs = $(this);
        var rsIndex = rs.closest("tr").index();
        var rsQuantity = parseInt(rs.attr("rowspan"));
        if (myRow > rsIndex && myRow <= rsIndex + rsQuantity - 1) {
    // alert('Row: ' + myRow + ', Column: ' + myCol);
    return myCol;

MySQL LIMIT on DELETE statement

simply use


Unable to launch the IIS Express Web server

I had a similar problem when running my solution from VS2012:

Unable to launch the IIS Express Web server.  
The start URL specified is not valid. https://localhost:44301/

I had the incorrect project selected as Startup Project. I made the Cloud project the Startup (right click on project -> Set as Startup Project) and everything started working fine.

Find (and kill) process locking port 3000 on Mac

To forcefully kill a process like that, use the following command

lsof -n -i4TCP:3000 

Where 3000 is the port number the process is running at

this returns the process id(PID) and run

kill -9 "PID"

Replace PID with the number you get after running the first command

For Instance, if I want kill the process running on port 8080

how to convert `content://media/external/images/media/Y` to `file:///storage/sdcard0/Pictures/X.jpg` in android?

Will something like this work for you? What this does is query the content resolver to find the file path data that is stored for that content entry

public static String getRealPathFromUri(Context context, Uri contentUri) {
    Cursor cursor = null;
    try {
        String[] proj = { MediaStore.Images.Media.DATA };
        cursor = context.getContentResolver().query(contentUri, proj, null, null, null);
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        return cursor.getString(column_index);
    } finally {
        if (cursor != null) {

This will end up giving you an absolute file path that you can construct a file uri from

GCC dump preprocessor defines

While working in a big project which has complex build system and where it is hard to get (or modify) the gcc/g++ command directly there is another way to see the result of macro expansion. Simply redefine the macro, and you will get output similiar to following:

file.h: note: this is the location of the previous definition
#define MACRO current_value

How do I add a foreign key to an existing SQLite table?

Basically you cannot but you can bypass the situation.

The correct way to add the foreign key constraint to an existing table is the following command.

db.execSQL("alter table child add column newCol integer REFERENCES parent(parent_Id)");

Then copy the parent_Id data to the newCol and then delete the Parent_Id column. Hence, no need for temporary table.

Displaying output of a remote command with Ansible

Prints pubkey and avoid the changed status by adding changed_when: False to cat task:

- name: Generate SSH keys for vagrant user   
  user: name=vagrant generate_ssh_key=yes ssh_key_bits=2048

- name: Check SSH public key   
  command: /bin/cat $home_directory/.ssh/
  register: cat
  changed_when: False

- name: Print SSH public key
  debug: var=cat.stdout

- name: Wait for user to copy SSH public key   
  pause: prompt="Please add the SSH public key above to your GitHub account"

How does Zalgo text work?

Zalgo text works because of combining characters. These are special characters that allow to modify character that comes before.

enter image description here


y + ̆ = y̆ which actually is

y + &#x0306; = y&#x0306;

Since you can stack them one atop the other you can produce the following:


which actually is:


The same goes for putting stuff underneath:


that in fact is:


In Unicode, the main block of combining diacritics for European languages and the International Phonetic Alphabet is U+0300–U+036F.

More about it here

To produce a list of combining diacritical marks you can use the following script (since links keep on dying)

for(var i=768; i<879; i++){console.log(new DOMParser().parseFromString("&#"+i+";", "text/html").documentElement.textContent +"  "+"&#"+i+";");}

Also check em out

Mͣͭͣ̾ Vͣͥͭ͛ͤͮͥͨͥͧ̾

How do I set the size of an HTML text box?

Elements can be sized with the height and width attributes.

Spring Data JPA - "No Property Found for Type" Exception

You should have that property defined in your model or entity class.

Handler vs AsyncTask vs Thread

It depends which one to chose is based on the requirement

Handler is mostly used to switch from other thread to main thread, Handler is attached to a looper on which it post its runnable task in queue. So If you are already in other thread and switch to main thread then you need handle instead of async task or other thread

If Handler created in other than main thread which is not a looper is will not give error as handle is created the thread, that thread need to be made a lopper

AsyncTask is used to execute code for few seconds which run on background thread and gives its result to main thread ** *AsyncTask Limitations 1. Async Task is not attached to life cycle of activity and it keeps run even if its activity destroyed whereas loader doesn't have this limitation 2. All Async Tasks share the same background thread for execution which also impact the app performance

Thread is used in app for background work also but it doesn't have any call back on main thread. If requirement suits some threads instead of one thread and which need to give task many times then thread pool executor is better option.Eg Requirement of Image loading from multiple url like glide.

How to print in C

The first argument to printf() is always a string value, known as a format control string. This string may be regular text, such as

printf("Hello, World\n"); // \n indicates a newline character


char greeting[] = "Hello, World\n";

This string may also contain one or more conversion specifiers; these conversion specifiers indicate that additional arguments have been passed to printf(), and they specify how to format those arguments for output. For example, I can change the above to

char greeting[] = "Hello, World";
printf("%s\n", greeting);

The "%s" conversion specifier expects a pointer to a 0-terminated string, and formats it as text.

For signed decimal integer output, use either the "%d" or "%i" conversion specifiers, such as

printf("%d\n", addNumber(a,b));

You can mix regular text with conversion specifiers, like so:

printf("The result of addNumber(%d, %d) is %d\n", a, b, addNumber(a,b));

Note that the conversion specifiers in the control string indicate the number and types of additional parameters. If the number or types of additional arguments passed to printf() don't match the conversion specifiers in the format string then the behavior is undefined. For example:

printf("The result of addNumber(%d, %d) is %d\n", addNumber(a,b));

will result in anything from garbled output to an outright crash.

There are a number of additional flags for conversion specifiers that control field width, precision, padding, justification, and types. Check your handy C reference manual for a complete listing.

What is the purpose of willSet and didSet in Swift?

The many well-written existing answers cover the question well, but I'll mention, in some detail, an addition that I believe is worth covering.

The willSet and didSet property observers can be used to call delegates, e.g., for class properties that are only ever updated by user interaction, but where you want to avoid calling the delegate at object initialization.

I'll cite Klaas up-voted comment to the accepted answer:

willSet and didSet observers are not called when a property is first initialized. They are only called when the property’s value is set outside of an initialization context.

This is a quite neat as it means e.g. the didSet property is a good choice of launch point for delegate callbacks & functions, for your own custom classes.

As an example, consider some custom user control object, with some key property value (e.g. position in rating control), implemented as a subclass of UIView:

// CustomUserControl.swift
protocol CustomUserControlDelegate {
    func didChangeValue(value: Int)
    // func didChangeValue(newValue: Int, oldValue: Int)
    // func didChangeValue(customUserControl: CustomUserControl)
    // ... other more sophisticated delegate functions

class CustomUserControl: UIView {

    // Properties
    // ...
    private var value = 0 {
        didSet {
            // Possibly do something ...

            // Call delegate.
            // delegate?.didChangeValue(value, oldValue: oldValue)
            // delegate?.didChangeValue(self)

    var delegate: CustomUserControlDelegate?

    // Initialization
    required init?(...) { 
        // Initialise something ...

        // E.g. 'value = 1' would not call didSet at this point

    // ... some methods/actions associated with your user control.

After which your delegate functions can be used in, say, some view controller to observe key changes in the model for CustomViewController, much like you'd use the inherent delegate functions of the UITextFieldDelegate for UITextField objects (e.g. textFieldDidEndEditing(...)).

For this simple example, use a delegate callback from the didSet of the class property value to tell a view controller that one of it's outlets have had associated model update:

// ViewController.swift
Import UIKit
// ...

class ViewController: UIViewController, CustomUserControlDelegate {

    // Properties
    // ...
    @IBOutlet weak var customUserControl: CustomUserControl!

    override func viewDidLoad() {
        // ...

        // Custom user control, handle through delegate callbacks.
        customUserControl = self

    // ...

    // CustomUserControlDelegate
    func didChangeValue(value: Int) {
        // do some stuff with 'value' ...

    // func didChangeValue(newValue: Int, oldValue: Int) {
        // do some stuff with new as well as old 'value' ...
        // custom transitions? :)

    //func didChangeValue(customUserControl: CustomUserControl) {
    //    // Do more advanced stuff ...

Here, the value property has been encapsulated, but generally: in situations like these, be careful not to update the value property of the customUserControl object in the scope of the associated delegate function (here: didChangeValue()) in the view controller, or you'll end up with infinite recursion.

How to dismiss keyboard iOS programmatically when pressing return

//Hide keyBoard by touching background in view

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [[self view] endEditing:YES];

Attempt to set a non-property-list object as an NSUserDefaults

Swift 5 Very Easy way

//MARK:- First you need to encoded your arr or what ever object you want to save in UserDefaults
//in my case i want to save Picture (NMutableArray) in the User Defaults in
//in this array some objects are UIImage & Strings

//first i have to encoded the NMutableArray 
let encodedData = NSKeyedArchiver.archivedData(withRootObject: yourArrayName)
//MARK:- Array save in UserDefaults
defaults.set(encodedData, forKey: "YourKeyName")

//MARK:- When you want to retreive data from UserDefaults
let decoded  = defaults.object(forKey: "YourKeyName") as! Data
yourArrayName = NSKeyedUnarchiver.unarchiveObject(with: decoded) as! NSMutableArray

//MARK: Enjoy this arrry "yourArrayName"

What is "string[] args" in Main class for?

From the C# programming guide on MSDN:

The parameter of the Main method is a String array that represents the command-line arguments

So, if I had a program (MyApp.exe) like this:

class Program
  static void Main(string[] args)
    foreach (var arg in args)

That I started at the command line like this:

MyApp.exe Arg1 Arg2 Arg3

The Main method would be passed an array that contained three strings: "Arg1", "Arg2", "Arg3".

If you need to pass an argument that contains a space then wrap it in quotes. For example:

MyApp.exe "Arg 1" "Arg 2" "Arg 3"

Command line arguments commonly get used when you need to pass information to your application at runtime. For example if you were writing a program that copies a file from one location to another you would probably pass the two locations as command line arguments. For example:

Copy.exe C:\file1.txt C:\file2.txt

error NG6002: Appears in the NgModule.imports of AppModule, but could not be resolved to an NgModule class

I got this error when I added the service class. I was using Angular 9 Went for several solutions, nothing helped me to resolve this issue. If U tried everything make sure u added ng module reference in core lib inside service. See Img

Date validation with ASP.NET validator

I think the following is the easiest way to do it.

<asp:TextBox ID="DateControl" runat="server" Visible="False"></asp:TextBox>
<asp:RangeValidator ID ="rvDate" runat ="server" ControlToValidate="DateControl" ErrorMessage="Invalid Date" Type="Date" MinimumValue="01/01/1900" MaximumValue="01/01/2100" Display="Dynamic"></asp:RangeValidator>

Error: Node Sass version 5.0.0 is incompatible with ^4.0.0

Small update: Incase if you get below error in regard to node-sass follow the steps given below.

code EPERM
npm ERR! syscall unlink

steps to solve the issue:

  1. close visual studio
  2. manually remove .node-sass.DELETE from node_modules
  3. open visual studio
  4. npm cache verify
  5. npm install [email protected]

H.264 file size for 1 hr of HD video

If you know the bitrate, it's simply bitrate (bits per second) multiplied by number of seconds. Given that HDV is 25 Mbit/s and one hour has 3,600 seconds, non-transcoded it would be:

25 Mbit/s * 3,600 s/hr  =  3.125 MB/s * 3,600 s/hr  =  11,250 MB/hr  ˜  11 GB/hr

Google's calculator can confirm

The same applies with H.264 footage, although the above might not be as accurate (being variable bitrate and such).

I want to archive approximately 100 hours of such content and want to figure out whether I'm looking at a big hard drive, a multi-drive unit like a Drobo, or an enterprise-level storage system.

First, do not buy an "enterprise-level" storage system (you almost certainly don't need things like hot-swap drives and the same level of support - given the costs)..

I would suggest buying two big drives: One would be your main drive, another in a USB enclosure, and would be connected daily and mirror the primary system (as a backup).

Drives are incredibly cheap, using the above calculation of ~11 GB/hour, that's only 1.1 TB of data (for 100 hours, uncompressed). and you can buy 2 TB drives now.

Drobo, or a machine with a few drives and software RAID is an option, but a single large drive plus backups would be simpler.

Storage is almost a non-issue now, but encode time can still be an issue. Encoding H.264 is very resource-intensive. On a quad-core ~2.5 GHz Xeon, I think I got around 60 fps encoding standard-def (DVD) to H.264 (compared to around 300 fps with MPEG 4). I suppose that's only about 50 hours, but it's something worth considering. Also, assuming the HDV is on tapes, it's a 1:1 capture time, so that's 150 hours of straight processing, never mind things like changing tapes, entering metadata, and general delays (sleep) and errors ("opps, wrong tape").

How to merge a specific commit in Git

The leading answers describe how to apply the changes from a specific commit to the current branch. If that's what you mean by "how to merge," then just use cherry-pick as they suggest.

But if you actually want a merge, i.e. you want a new commit with two parents -- the existing commit on the current branch, and the commit you wanted to apply changes from -- then a cherry-pick will not accomplish that.

Having true merge history may be desirable, for example, if your build process takes advantage of git ancestry to automatically set version strings based on the latest tag (using git describe).

Instead of cherry-pick, you can do an actual git merge --no-commit, and then manually adjust the index to remove any changes you don't want.

Suppose you're on branch A and you want to merge the commit at the tip of branch B:

git checkout A
git merge --no-commit B

Now you're set up to create a commit with two parents, the current tip commits of A and B. However you may have more changes applied than you want, including changes from earlier commits on the B branch. You need to undo these unwanted changes, then commit.

(There may be an easy way to set the state of the working directory and the index back to way it was before the merge, so that you have a clean slate onto which to cherry-pick the commit you wanted in the first place. But I don't know how to achieve that clean slate. git checkout HEAD and git reset HEAD will both remove the merge state, defeating the purpose of this method.)

So manually undo the unwanted changes. For example, you could

git revert --no-commit 012ea56

for each unwanted commit 012ea56.

When you're finished adjusting things, create your commit:

git commit -m "Merge in commit 823749a from B which tweaked the timeout code"

Now you have only the change you wanted, and the ancestry tree shows that you technically merged from B.

Python conversion between coordinates

The existing answers can be simplified:

from numpy import exp, abs, angle

def polar2z(r,theta):
    return r * exp( 1j * theta )

def z2polar(z):
    return ( abs(z), angle(z) )

Or even:

polar2z = lambda r,?: r * exp( 1j * ? )
z2polar = lambda z: ( abs(z), angle(z) )

Note these also work on arrays!

rS, thetaS = z2polar( [z1,z2,z3] )
zS = polar2z( rS, thetaS )

Run bash script from Windows PowerShell

If you add the extension .SH to the environment variable PATHEXT, you will be able to run shell scripts from PowerShell by only using the script name with arguments:

PS> .\ args

If you store your scripts in a directory that is included in your PATH environment variable, you can run it from anywhere, and omit the extension and path:

PS> script args

Note: sh.exe or another *nix shell must be associated with the .sh extension.

Why doesn't Mockito mock static methods?

Mockito returns objects but static means "class level,not object level"So mockito will give null pointer exception for static.

Timer function to provide time in nano seconds using C++

plf::nanotimer is a lightweight option for this, works in Windows, Linux, Mac and BSD etc. Has ~microsecond accuracy depending on OS:

  #include "plf_nanotimer.h"
  #include <iostream>

  int main(int argc, char** argv)
      plf::nanotimer timer;


      // Do something here

      double results = timer.get_elapsed_ns();
      std::cout << "Timing: " << results << " nanoseconds." << std::endl;    
      return 0;

How to convert DateTime to a number with a precision greater than days in T-SQL?

You can use T-SQL to convert the date before it gets to your .NET program. This often is simpler if you don't need to do additional date conversion in your .NET program.

DECLARE @Date DATETIME = Getdate()
DECLARE @DateInt INT = CONVERT(VARCHAR(30), @Date, 112)
DECLARE @TimeInt INT = REPLACE(CONVERT(VARCHAR(30), @Date, 108), ':', '')
DECLARE @DateTimeInt BIGINT = CONVERT(VARCHAR(30), @Date, 112) + REPLACE(CONVERT(VARCHAR(30), @Date, 108), ':', '')
SELECT @Date as Date, @DateInt DateInt, @TimeInt TimeInt, @DateTimeInt DateTimeInt

Date                    DateInt     TimeInt     DateTimeInt
------------------------- ----------- ----------- --------------------
2013-01-07 15:08:21.680 20130107    150821      20130107150821

How to reload current page without losing any form data?

I usually submit automatically my own form to the server and reload the page with filled arguments. Replace the placeholder arguments with the params your server received.

Add the loading screen in starting of the android application

If the application is not doing anything in that 10 seconds, this will form a bad design only to make the user wait for 10 seconds doing nothing.

If there is something going on in that, or if you wish to implement 10 seconds delay splash screen,Here is the Code :

ProgressDialog pd;
pd =,"Please Wait...", "Loading Application..", false, true);
Thread t = new Thread()
      public void run()
                    sleep(10000)  //Delay of 10 seconds
        catch (Exception e) {}
} ;

//Handles the thread result of the Backup being executed.
private Handler handler = new Handler()
    public void handleMessage(Message msg) 
        //Start the Next Activity here...


I want to get the type of a variable at runtime

i have tested that and it worked

val x = 9
def printType[T](x:T) :Unit = {println(x.getClass.toString())}

OnClickListener in Android Studio

    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(, menu);
        return true;

    public boolean onOptionsItemSelected(MenuItem item) {
         int id = item.getItemId();
         if (id == {
            startActivity(new Intent(MainActivity.this,StandingsActivity.class));
            return true;
        return super.onOptionsItemSelected(item);

Ruby: How to convert a string to boolean

Although I like the hash approach (I've used it in the past for similar stuff), given that you only really care about matching truthy values - since - everything else is false - you can check for inclusion in an array:

value = [true, 'true'].include?(value)

or if other values could be deemed truthy:

value = [1, true, '1', 'true'].include?(value)

you'd have to do other stuff if your original value might be mixed case:

value = value.to_s.downcase == 'true'

but again, for your specific description of your problem, you could get away with that last example as your solution.

Pandas KeyError: value not in index

I had a very similar issue. I got the same error because the csv contained spaces in the header. My csv contained a header "Gender " and I had it listed as:


If it's easy enough for you to access your csv, you can use the excel formula trim() to clip any spaces of the cells.

or remove it like this

df.columns = df.columns.to_series().apply(lambda x: x.strip())

Right to Left support for Twitter Bootstrap 3

If you want Bootstrap 3 support for RTL and LTR on your site, you can modify CSS rules "on the fly", attached here is a function, it modifies the major classes for Bootstrap 3 like col-(xs|sm|md|lg)-(1-12), col-(xs|sm|md|lg)-push-(1-12), col-(xs|sm|md|lg)-pull-(1-12), col-(xs|sm|md|lg)-offset-(1-12), there are many more classes to be modified but i needed only those.

All you need to do is call the function layout.setDirection('rtl') or layout.setDirection('ltr') and it will change the CSS Rules for Bootstrap 3 grid system.

Should work on all browsers (IE>=9).

        var layout = {};
        layout.setDirection = function (direction) {
            layout.rtl = (direction === 'rtl');
            document.getElementsByTagName("html")[0].style.direction = direction;
            var styleSheets = document.styleSheets;
            var modifyRule = function (rule) {
                if ( ? 'left' : 'right') && rule.selectorText.match(/\.col-(xs|sm|md|lg)-push-\d\d*/)) {
           ? 'right' : 'left'), ? 'left' : 'right')));
           ? 'left' : 'right'));
                if ( ? 'right' : 'left') && rule.selectorText.match(/\.col-(xs|sm|md|lg)-pull-\d\d*/)) {
           ? 'left' : 'right'), ? 'right' : 'left')));
           ? 'right' : 'left'));
                if ( ? 'margin-left' : 'margin-right') && rule.selectorText.match(/\.col-(xs|sm|md|lg)-offset-\d\d*/)) {
           ? 'margin-right' : 'margin-left'), ? 'margin-left' : 'margin-right')));
           ? 'margin-left' : 'margin-right'));
                if ('float') && rule.selectorText.match(/\.col-(xs|sm|md|lg)-\d\d*/)) {
          'float', (layout.rtl ? 'right' : 'left'));
            try {
                for (var i = 0; i < styleSheets.length; i++) {
                    var rules = styleSheets[i].cssRules || styleSheets[i].rules;
                    if (rules) {
                        for (var j = 0; j < rules.length; j++) {
                            if (rules[j].type === 4) {
                                var mediaRules = rules[j].cssRules || rules[j].rules
                                for (var y = 0; y < mediaRules.length; y++) {
                            if (rules[j].type === 1) {

            } catch (e) {
                // Firefox might throw a SecurityError exception but it will work
                if ( !== 'SecurityError') {
                    throw e;

Convert file path to a file URI?

At least in .NET 4.5+ you can also do:

var uri = new System.Uri("C:\\foo", UriKind.Absolute);

Instagram how to get my user id from username?

Most of these answers are invalid after the 6/1/2016 Instagram API changes. The best solution now is here. Go to your feed on, copy the link address for any of your pictures, and paste it into the textbox on that page. Worked like a charm.

What is SOA "in plain english"?

A traditional application architecture is:

  • A user interface
  • Undefined stuff (implementation) that's encapsulated/hidden behind the user interface

If you want to access the data programmatically, you might need to resort to screen-scraping.

SOA seems to me to be an architecture which focus on exposing machine-readable data and/or APIs, instead of on exposing UIs.

How to tell if a JavaScript function is defined


if (typeof(callback) == 'function')

C++11 introduced a standardized memory model. What does it mean? And how is it going to affect C++ programming?

It means that the standard now defines multi-threading, and it defines what happens in the context of multiple threads. Of course, people used varying implementations, but that's like asking why we should have a std::string when we could all be using a home-rolled string class.

When you're talking about POSIX threads or Windows threads, then this is a bit of an illusion as actually you're talking about x86 threads, as it's a hardware function to run concurrently. The C++0x memory model makes guarantees, whether you're on x86, or ARM, or MIPS, or anything else you can come up with.

Hide Text with CSS, Best Practice?

you can simply make it transparent

   width: 20px;
   height: 20px;
   overflow: hidden; 

Servlet for serving static content

To serve all requests from a Spring app as well as /favicon.ico and the JSP files from /WEB-INF/jsp/* that Spring's AbstractUrlBasedView will request you can just remap the jsp servlet and default servlet:





We can't rely on the *.jsp url-pattern on the standard mapping for the jsp servlet because the path pattern '/*' is matched before any extension mapping is checked. Mapping the jsp servlet to a deeper folder means it's matched first. Matching '/favicon.ico' exactly happens before path pattern matching. Deeper path matches will work, or exact matches, but no extension matches can make it past the '/*' path match. Mapping '/' to default servlet doesn't appear to work. You'd think the exact '/' would beat the '/*' path pattern on springapp.

The above filter solution doesn't work for forwarded/included JSP requests from the application. To make it work I had to apply the filter to springapp directly, at which point the url-pattern matching was useless as all requests that go to the application also go to its filters. So I added pattern matching to the filter and then learned about the 'jsp' servlet and saw that it doesn't remove the path prefix like the default servlet does. That solved my problem, which was not exactly the same but common enough.

How to group dataframe rows into list in pandas groupby

Building upon @B.M answer, here is a more general version and updated to work with newer library version: (numpy version 1.19.2, pandas version 1.2.1) And this solution can also deal with multi-indices:

However this is not heavily tested, use with caution.

If performance is important go down to numpy level:

import pandas as pd
import numpy as np

df = pd.DataFrame({'a': np.random.randint(0, 10, 90), 'b': [1,2,3]*30, 'c':list('abcefghij')*10, 'd': list('hij')*30})

def f_multi(df,col_names):
    if not isinstance(col_names,list):
        col_names = [col_names]
    values = df.sort_values(col_names).values.T

    col_idcs = [df.columns.get_loc(cn) for cn in col_names]
    other_col_names = [name for idx, name in enumerate(df.columns) if idx not in col_idcs]
    other_col_idcs = [df.columns.get_loc(cn) for cn in other_col_names]

    # split df into indexing colums(=keys) and data colums(=vals)
    keys = values[col_idcs,:]
    vals = values[other_col_idcs,:]
    # list of tuple of key pairs
    multikeys = list(zip(*keys))
    # remember unique key pairs and ther indices
    ukeys, index = np.unique(multikeys, return_index=True, axis=0)
    # split data columns according to those indices
    arrays = np.split(vals, index[1:], axis=1)

    # resulting list of subarrays has same number of subarrays as unique key pairs
    # each subarray has the following shape:
    #    rows = number of non-grouped data columns
    #    cols = number of data points grouped into that unique key pair
    # prepare multi index
    idx = pd.MultiIndex.from_arrays(ukeys.T, names=col_names) 

    list_agg_vals = dict()
    for tup in zip(*arrays, other_col_names):
        col_vals = tup[:-1] # first entries are the subarrays from above 
        col_name = tup[-1]  # last entry is data-column name
        list_agg_vals[col_name] = col_vals

    df2 = pd.DataFrame(data=list_agg_vals, index=idx)
    return df2


In [227]: %timeit f_multi(df, ['a','d'])

2.54 ms ± 64.7 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

In [228]: %timeit df.groupby(['a','d']).agg(list)

4.56 ms ± 61.5 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)


for the random seed 0 one would get:

enter image description here

AngularJs - ng-model in a SELECT

You dont need to define option tags, you can do this using the ngOptions directive:

<select class="form-control" ng-change="unitChanged()" ng-model="data.unit" ng-options=" as unit.label for unit in units"></select>

Difference between maven scope compile and provided for JAR packaging

If you're planning to generate a single JAR file with all of its dependencies (the typical xxxx-all.jar), then provided scope matters, because the classes inside this scope won't be package in the resulting JAR.

See maven-assembly-plugin for more information

Return from a promise then()

When you return something from a then() callback, it's a bit magic. If you return a value, the next then() is called with that value. However, if you return something promise-like, the next then() waits on it, and is only called when that promise settles (succeeds/fails).


How to select a node of treeview programmatically in c#?

yourNode.Toggle(); //use that function on your node, it toggles it

position fixed header in html

  padding:0 0 0 0;
@media screen{
   position: fixed;
* html body{
* html div#content{

How to alter SQL in "Edit Top 200 Rows" in SSMS 2008

You can also change the pop-up options themselves, to be more convenient for your normal use. Summary:

  1. Run the SQL Management Studio Express 2008
  2. Click the Tools -> Options
  3. Select SQL Server Object Explorer . Now you should be able to see the options

    • Value for Edit Top Rows Command
    • Value for Select Top Rows Command
  4. Give the Values 0 here to select/ Edit all the Records

Full Instructions with screenshots are here:

Multiple inheritance for an anonymous class

An anonymous class usually implements an interface:

new Runnable() { // implements Runnable!
   public void run() {}

JFrame.addWindowListener( new WindowAdapter() { // extends  class
} );

If you mean whether you can implement 2 or more interfaces, than I think that's not possible. You can then make a private interface which combines the two. Though I cannot easily imagine why you would want an anonymous class to have that:

 public class MyClass {
   private interface MyInterface extends Runnable, WindowListener { 

   Runnable r = new MyInterface() {
    // your anonymous class which implements 2 interaces


Global Events in Angular

There is no equivalent to $scope.emit() or $scope.broadcast() from AngularJS. EventEmitter inside of a component comes close, but as you mentioned, it will only emit an event to the immediate parent component.

In Angular, there are other alternatives which I'll try to explain below.

@Input() bindings allows the application model to be connected in a directed object graph (root to leaves). The default behavior of a component's change detector strategy is to propagate all changes to an application model for all bindings from any connected component.

Aside: There are two types of models: View Models and Application Models. An application model is connected through @Input() bindings. A view model is a just a component property (not decorated with @Input()) which is bound in the component's template.

To answer your questions:

What if I need to communicate between sibling components?

  1. Shared Application Model: Siblings can communicate through a shared application model (just like angular 1). For example, when one sibling makes a change to a model, the other sibling that has bindings to the same model is automatically updated.

  2. Component Events: Child components can emit an event to the parent component using @Output() bindings. The parent component can handle the event, and manipulate the application model or it's own view model. Changes to the Application Model are automatically propagated to all components that directly or indirectly bind to the same model.

  3. Service Events: Components can subscribe to service events. For example, two sibling components can subscribe to the same service event and respond by modifying their respective models. More on this below.

How can I communicate between a Root component and a component nested several levels deep?

  1. Shared Application Model: The application model can be passed from the Root component down to deeply nested sub-components through @Input() bindings. Changes to a model from any component will automatically propagate to all components that share the same model.
  2. Service Events: You can also move the EventEmitter to a shared service, which allows any component to inject the service and subscribe to the event. That way, a Root component can call a service method (typically mutating the model), which in turn emits an event. Several layers down, a grand-child component which has also injected the service and subscribed to the same event, can handle it. Any event handler that changes a shared Application Model, will automatically propagate to all components that depend on it. This is probably the closest equivalent to $scope.broadcast() from Angular 1. The next section describes this idea in more detail.

Example of an Observable Service that uses Service Events to Propagate Changes

Here is an example of an observable service that uses service events to propagate changes. When a TodoItem is added, the service emits an event notifying its component subscribers.

export class TodoItem {
    constructor(public name: string, public done: boolean) {
export class TodoService {
    public itemAdded$: EventEmitter<TodoItem>;
    private todoList: TodoItem[] = [];

    constructor() {
        this.itemAdded$ = new EventEmitter();

    public list(): TodoItem[] {
        return this.todoList;

    public add(item: TodoItem): void {

Here is how a root component would subscribe to the event:

export class RootComponent {
    private addedItem: TodoItem;
    constructor(todoService: TodoService) {
        todoService.itemAdded$.subscribe(item => this.onItemAdded(item));

    private onItemAdded(item: TodoItem): void {
        // do something with added item
        this.addedItem = item;

A child component nested several levels deep would subscribe to the event in the same way:

export class GrandChildComponent {
    private addedItem: TodoItem;
    constructor(todoService: TodoService) {
        todoService.itemAdded$.subscribe(item => this.onItemAdded(item));

    private onItemAdded(item: TodoItem): void {
        // do something with added item
        this.addedItem = item;

Here is the component that calls the service to trigger the event (it can reside anywhere in the component tree):

    selector: 'todo-list',
    template: `
            <li *ngFor="#item of model"> {{ }}
        <br />
        Add Item <input type="text" #txt /> <button (click)="add(txt.value); txt.value='';">Add</button>
export class TriggeringComponent{
    private model: TodoItem[];

    constructor(private todoService: TodoService) {
        this.model = todoService.list();

    add(value: string) {
        this.todoService.add(new TodoItem(value, false));

Reference: Change Detection in Angular

Delete dynamically-generated table row using jQuery

I know this is old but I've used a function similar to this...

deleteRow: function (ctrl) {

    //remove the row from the table


... with markup like this ...

<td><span id="spDeleteRow" onclick="deleteRow(this)">X</td>
<td> blah blah </td>

...and it works fine

ADB Android Device Unauthorized

Try forcing ADB to create new keys.

  • On Linux:

    $ mv ~/.android/adbkey ~/.android/adbkey.old
    $ mv ~/.android/ ~/.android/
    $ adb kill-server
    $ adb start-server
  • On Windows 10 (thank you, Pau Coma Ramirez, Naveen and d4c0d312!):

    • Go to %HOMEPATH%\Android\.android\
    • Look for files called adbkey or
    • Delete these files. Or, if you want to be on the safe side, move them to another directory.
    • Repeat the above steps in %USERPROFILE%\.android\
    • Try again

After this I didn't even need to unplug my phone: the authorization prompt was already there. Good luck!

Equivalent of LIMIT for DB2

Developed this method:

You NEED a table that has an unique value that can be ordered.

If you want rows 10,000 to 25,000 and your Table has 40,000 rows, first you need to get the starting point and total rows:

int start = 40000 - 10000;

int total = 25000 - 10000;

And then pass these by code to the query:

(SELECT * FROM schema.mytable 
ORDER BY userId DESC fetch first {start} rows only ) AS mini 
ORDER BY mini.userId ASC fetch first {total} rows only

AngularJs .$setPristine to reset form

Had a similar problem, where I had to set the form back to pristine, but also to untouched, since $invalid and $error were both used to show error messages. Only using setPristine() was not enough to clear the error messages.

I solved it by using setPristine() and setUntouched(). (See Angular's documentation:

So, in my controller, I used:


These two functions reset the complete form to $pristine and back to $untouched, so that all error messages were cleared.

ASP.NET Background image

Use this Code in code behind

Div_Card.Style["background-image"] = Page.ResolveUrl(Session["Img_Path"].ToString());

[] and {} vs list() and dict(), which is better?

A box bracket pair denotes one of a list object, or an index subscript, my_List[x].

A curly brace pair denotes a dictionary object.

a_list = ['on', 'off', 1, 2]

a_dict = { on: 1, off: 2 }

Why does NULL = NULL evaluate to false in SQL server

To quote the Christmas analogy again:

In SQL, NULL basically means "closed box" (unknown). So, the result of comparing two closed boxes will also be unknown (null).

I understand, for a developer, this is counter-intuitive, because in programming languages, often NULL rather means "empty box" (known). And comparing two empty boxes will naturally yield true / equal.

This is why JavaScript for example distinguishes between null and undefined.

What is the difference between "Form Controls" and "ActiveX Control" in Excel 2010?

It's also worth noting that ActiveX controls only work in Windows, whereas Form Controls will work on both Windows and MacOS versions of Excel.

Java 8: How do I work with exception throwing methods in streams?

If all you want is to invoke foo, and you prefer to propagate the exception as is (without wrapping), you can also just use Java's for loop instead (after turning the Stream into an Iterable with some trickery):

for (A a : (Iterable<A>) as::iterator) {;

This is, at least, what I do in my JUnit tests, where I don't want to go through the trouble of wrapping my checked exceptions (and in fact prefer my tests to throw the unwrapped original ones)

Margin between items in recycler view Android

I faced similar issue, with RelativeLayout as the root element for each row in the recyclerview.

To solve the issue, find the xml file that holds each row and make sure that the root element's height is wrap_content NOT match_parent.

Is Spring annotation @Controller same as @Service?

@Service vs @Controller

@Service : class is a "Business Service Facade" (in the Core J2EE patterns sense), or something similar.

@Controller : Indicates that an annotated class is a "Controller" (e.g. a web controller).

----------Find Usefull notes on Major Stereotypes

@interface Component

    public @interface Component

Indicates that an annotated class is a component. Such classes are considered as candidates for auto-detection when using annotation-based configuration and classpath scanning.

Other class-level annotations may be considered as identifying a component as well, typically a special kind of component: e.g. the @Repository annotation or AspectJ's @Aspect annotation.

@interface Controller

public @interface Controller

Indicates that an annotated class is a "Controller" (e.g. a web controller).

This annotation serves as a specialization of @Component, allowing for implementation classes to be autodetected through classpath scanning. It is typically used in combination with annotated handler methods based on the RequestMapping annotation.

@interface Service

public @interface Service

Indicates that an annotated class is a "Service", originally defined by Domain-Driven Design (Evans, 2003) as "an operation offered as an interface that stands alone in the model, with no encapsulated state." May also indicate that a class is a "Business Service Facade" (in the Core J2EE patterns sense), or something similar. This annotation is a general-purpose stereotype and individual teams may narrow their semantics and use as appropriate.

This annotation serves as a specialization of @Component, allowing for implementation classes to be autodetected through classpath scanning.

@interface Repository

public @interface Repository

Indicates that an annotated class is a "Repository", originally defined by Domain-Driven Design (Evans, 2003) as "a mechanism for encapsulating storage, retrieval, and search behavior which emulates a collection of objects". Teams implementing traditional J2EE patterns such as "Data Access Object" may also apply this stereotype to DAO classes, though care should be taken to understand the distinction between Data Access Object and DDD-style repositories before doing so. This annotation is a general-purpose stereotype and individual teams may narrow their semantics and use as appropriate.

A class thus annotated is eligible for Spring DataAccessException translation when used in conjunction with a PersistenceExceptionTranslationPostProcessor. The annotated class is also clarified as to its role in the overall application architecture for the purpose of tooling, aspects, etc.

As of Spring 2.5, this annotation also serves as a specialization of @Component, allowing for implementation classes to be autodetected through classpath scanning.

SQL: how to select a single id ("row") that meets multiple criteria from a single column

brute force (and only tested on an Oracle system, but I think this is pretty standard):

select distinct usr_id from users where user_id in (
    select user_id from (
      Select user_id, Count(User_Id) As Cc
      From users 
      GROUP BY user_id
    ) Where Cc =3
  and ancestry in ('England', 'France', 'Germany')

edit: I like @HuckIt's answer even better.

How to prevent scrollbar from repositioning web page?

Expanding on the answer using this:

body {
    width: calc(100vw - 17px);

One commentor suggested adding left-padding as well to maintain the centering:

body {
    padding-left: 17px;
    width: calc(100vw - 17px);

But then things don't look correct if your content is wider than the viewport. To fix that, you can use media queries, like this:

@media screen and (min-width: 1058px) {
    body {
        padding-left: 17px;
        width: calc(100vw - 17px);

Where the 1058px = content width + 17 * 2

This lets a horizontal scrollbar handle the x overflow and keeps the centered content centered when the viewport is wide enough to contain your fixed-width content

Are there .NET implementation of TLS 1.2?

as mentioned here you can just add this line

ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;

Is it possible to import modules from all files in a directory, using a wildcard?

The current answers suggest a workaround but it's bugged me why this doesn't exist, so I've created a babel plugin which does this.

Install it using:

npm i --save-dev babel-plugin-wildcard

then add it to your .babelrc with:

    "plugins": ["wildcard"]

see the repo for detailed install info

This allows you to do this:

import * as Things from './lib/things';

// Do whatever you want with these :D

again, the repo contains further information on what exactly it does, but doing it this way avoids creating index.js files and also happens at compile-time to avoid doing readdirs at runtime.

Also with a newer version you can do exactly like your example:

 import { ThingsA, ThingsB, ThingsC } from './lib/things/*';

works the same as the above.

How can I connect to MySQL in Python 3 on Windows?


import pymysql

open database connection

db = pymysql.connect("localhost","root","","ornament")

prepare a cursor object using cursor() method

cursor = db.cursor()

sql = "SELECT * FROM item"


Fetch all the rows in a list of lists.

results = cursor.fetchall()
for row in results:
   item_title = row[1]
   comment = row[2]
   print ("Title of items are the following  = %s,Comments are the following = %s" % \
          (item_title, comment))

Python requests library how to pass Authorization header with single token

Requests natively supports basic auth only with user-pass params, not with tokens.

You could, if you wanted, add the following class to have requests support token based basic authentication:

import requests
from base64 import b64encode

class BasicAuthToken(requests.auth.AuthBase):
    def __init__(self, token):
        self.token = token
    def __call__(self, r):
        authstr = 'Basic ' + b64encode(('token:' + self.token).encode('utf-8')).decode('utf-8')
        r.headers['Authorization'] = authstr
        return r

Then, to use it run the following request :

r = requests.get(url, auth=BasicAuthToken(api_token))

An alternative would be to formulate a custom header instead, just as was suggested by other users here.

Change the background color of a pop-up dialog

Credit goes to Sushil

Create your AlertDialog as usual:

AlertDialog.Builder dialog = new AlertDialog.Builder(getContext());
Dialog dialog = dialog.create();;

After calling show() on your dialog, set the background color like this:


Given two directory trees, how can I find out which files differ by content?

The command I use is:

diff -qr dir1/ dir2/

It is exactly the same as Mark's :) But his answer bothered me as it uses different types of flags, and it made me look twice. Using Mark's more verbose flags it would be:

diff  --brief --recursive dir1/ dir2/

I apologise for posting when the other answer is perfectly acceptable. Could not stop myself... working on being less pedantic.

Is it possible to declare two variables of different types in a for loop?

You can't declare multiple types in the initialization, but you can assign to multiple types E.G.

   int i;
   char x;
   for(i = 0, x = 'p'; ...){

Just declare them in their own scope.

How to install Visual Studio 2015 on a different drive

After trying to manually uninstall, and then downloading another copy of the VS 2015 community installer for use with the force uninstall command line argument (Original answer by Michael Schuchardt), I was still unable to modify the install directory.

After testing further, I found that Unity (which integrates with Visual Studio as of Unity 5.2) also had to be removed. At this point Visual Studio Uninstaller (link to latest release on Github) can be used for the final removal of remaining any remaining components.

You will now be able to run the Visual Studio Installer and select a directory or, alternatively, run the install from command line using the "/CustomInstallPath ..." argument.

Detect touch press vs long press vs movement?

If you need to distniguish between a click, longpress and a scroll use GestureDetector

Activity implements GestureDetector.OnGestureListener

then create detector in onCreate for example

mDetector = new GestureDetectorCompat(getActivity().getApplicationContext(),this);

then optionally setOnTouchListener on your View (for example webview) where

onTouch(View v, MotionEvent event) {
return mDetector.onTouchEvent(event);

and now you can use Override onScroll, onFling, showPress( detect long press) or onSingleTapUp (detect a click)

How to access static resources when mapping a global front controller servlet on /*

The best way to handle this is using some kind of URL re-writing. In this way, you can have clean restful URLs, and NOT with any extensions i.e as opposed to

I use Tuckey URL which is pretty cool.

It's got instructions on how to set up your web app.I have set it up with my Spring MVC web app. Of course, everything was fine until I wanted to use annotations for Spring 3 validations like @Email or @Null for domain objects.

When I add the Spring mvc directives:

< mvc:annotation-driven  /> 
< mvc:default-servlet-handler />

.. it breaks the good ol Tuckey code. Apparently, < mvc:default-servlet-handler /> replaces Tuckey, which I'm still trying to solve.

Counting lines, words, and characters within a text file using Python

file__IO = input('\nEnter file name here to analize with path:: ')
with open(file__IO, 'r') as f:
    data =
    line = data.splitlines()
    words = data.split()
    spaces = data.split(" ")
    charc = (len(data) - len(spaces))

    print('\n Line number ::', len(line), '\n Words number ::', len(words), '\n Spaces ::', len(spaces), '\n Charecters ::', (len(data)-len(spaces)))

I tried this code & it works as expected.

How to wrap text in textview in Android

Use app:breakStrategy="simple" in AppCompatTextView, it will control over paragraph layout.

It has three constant values

  • balanced
  • high_quality
  • simple

Designing in your TextView xml

        android:text="Your Question Display Hear....Your Question Display Hear....Your Question Display Hear....Your Question Display Hear...."
        app:breakStrategy="simple" />

If your current minimum api level is 23 or more then in Coding


For more refrence refer this BreakStrategy

Textview breakStrategy image

What is a 'Closure'?

Variable scope

When you declare a local variable, that variable has a scope. Generally, local variables exist only within the block or function in which you declare them.

function() {
  var a = 1;
  console.log(a); // works
console.log(a); // fails

If I try to access a local variable, most languages will look for it in the current scope, then up through the parent scopes until they reach the root scope.

var a = 1;
function() {
  console.log(a); // works
console.log(a); // works

When a block or function is done with, its local variables are no longer needed and are usually blown out of memory.

This is how we normally expect things to work.

A closure is a persistent local variable scope

A closure is a persistent scope which holds on to local variables even after the code execution has moved out of that block. Languages which support closure (such as JavaScript, Swift, and Ruby) will allow you to keep a reference to a scope (including its parent scopes), even after the block in which those variables were declared has finished executing, provided you keep a reference to that block or function somewhere.

The scope object and all its local variables are tied to the function and will persist as long as that function persists.

This gives us function portability. We can expect any variables that were in scope when the function was first defined to still be in scope when we later call the function, even if we call the function in a completely different context.

For example

Here's a really simple example in JavaScript that illustrates the point:

outer = function() {
  var a = 1;
  var inner = function() {
  return inner; // this returns a function

var fnc = outer(); // execute outer to get inner 

Here I have defined a function within a function. The inner function gains access to all the outer function's local variables, including a. The variable a is in scope for the inner function.

Normally when a function exits, all its local variables are blown away. However, if we return the inner function and assign it to a variable fnc so that it persists after outer has exited, all of the variables that were in scope when inner was defined also persist. The variable a has been closed over -- it is within a closure.

Note that the variable a is totally private to fnc. This is a way of creating private variables in a functional programming language such as JavaScript.

As you might be able to guess, when I call fnc() it prints the value of a, which is "1".

In a language without closure, the variable a would have been garbage collected and thrown away when the function outer exited. Calling fnc would have thrown an error because a no longer exists.

In JavaScript, the variable a persists because the variable scope is created when the function is first declared and persists for as long as the function continues to exist.

a belongs to the scope of outer. The scope of inner has a parent pointer to the scope of outer. fnc is a variable which points to inner. a persists as long as fnc persists. a is within the closure.

ORA-01461: can bind a LONG value only for insert into a LONG column-Occurs when querying

This ORA-01461 does not occur only while inserting into a Long column. This error can occur when binding a long string for insert into a VARCHAR2 column and most commonly occurs when there is a multi byte(means single char can take more than one byte space in oracle) character conversion issue.

If the database is UTF-8 then, because of the fact that each character can take up to 3 bytes, conversion of 3 applied to check and so actually limited to use 1333 characters to insert into varchar2(4000).

Another solution would be change the datatype from varchar2(4000) to CLOB.

How to stop Python closing immediately when executed in Microsoft Windows

In Python 3, add the following to the end of your code:

input('Press ENTER to exit')

This will cause the program to wait for user input, with pressing ENTER causing the program to finish.

You can double click on your file in Windows conveniently this way.

How to force garbage collection in Java?

YES it is almost possible to forced you have to call to methods in the same order and at the same time this ones are:

System.gc ();
System.runFinalization ();

even if is just one object to clean the use of this two methods at the same time force the garbage collector to use the finalise() method of unreachable object freeing the memory assigned and doing what the finalize() method states.

HOWEVER it is a terrible practice to use the garbage collector because the use of it could introduce an over load to the software that may be even worst than on the memory, the garbage collector has his own thread which is not possible to control plus depending on the algorithm used by the gc could take more time and is consider very inefficient, you should check your software if it worst with the help of the gc because it is definitely broke, a good solution must not depend on the gc.

NOTE: just to keep on mind this will works only if in the finalize method is not a reassignment of the object, if this happens the object will keep alive an it will have a resurrection which is technically possible.

Calculate a MD5 hash from a string

I suppose it is better to use UTF-8 encoding in the string MD5.

public static string MD5(this string s)
    using (var provider = System.Security.Cryptography.MD5.Create())
        StringBuilder builder = new StringBuilder();                           

        foreach (byte b in provider.ComputeHash(Encoding.UTF8.GetBytes(s)))

        return builder.ToString();

How can I get the intersection, union, and subset of arrays in Ruby?

If Multiset extends from the Array class

x = [1, 1, 2, 4, 7]
y = [1, 2, 2, 2]
z = [1, 1, 3, 7]


x.union(y)           # => [1, 2, 4, 7]      (ONLY IN RUBY 2.6)
x.union(y, z)        # => [1, 2, 4, 7, 3]   (ONLY IN RUBY 2.6)
x | y                # => [1, 2, 4, 7]


x.difference(y)      # => [4, 7] (ONLY IN RUBY 2.6)
x.difference(y, z)   # => [4] (ONLY IN RUBY 2.6)
x - y                # => [4, 7]


x & y                # => [1, 2]

For more info about the new methods in Ruby 2.6, you can check this blog post about its new features

Combine two arrays

If you are using PHP 7.4 or above, you can use the spread operator ... as the following examples from the PHP Docs:

$arr1 = [1, 2, 3];
$arr2 = [...$arr1]; //[1, 2, 3]
$arr3 = [0, ...$arr1]; //[0, 1, 2, 3]
$arr4 = array(...$arr1, ...$arr2, 111); //[1, 2, 3, 1, 2, 3, 111]
$arr5 = [...$arr1, ...$arr1]; //[1, 2, 3, 1, 2, 3]

function getArr() {
  return ['a', 'b'];
$arr6 = [...getArr(), 'c']; //['a', 'b', 'c']

$arr7 = [ ArrayIterator(['a', 'b', 'c'])]; //['a', 'b', 'c']

function arrGen() {
    for($i = 11; $i < 15; $i++) {
        yield $i;
$arr8 = [...arrGen()]; //[11, 12, 13, 14]

It works like in JavaScript ES6.

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