Programs & Examples On #Tree balancing

The best way to calculate the height in a binary search tree? (balancing an AVL-tree)

Here's where it gets confusing, the text states "If the balance factor of R is 1, it means the insertion occurred on the (external) right side of that node and a left rotation is needed". But from m understanding the text said (as I quoted) that if the balance factor was within [-1, 1] then there was no need for balancing?

Okay, epiphany time.

Consider what a rotation does. Let's think about a left rotation.

 P = parent
 O = ourself (the element we're rotating)
 RC = right child
 LC = left child (of the right child, not of ourself)

 P              10
  \               \
   O               15
    \                \
     RC               20
    /                /
   LC               18

 P              10
   \               \
     RC              20
   /               /
  O              15
   \               \
   LC              18

 basically, what happens is;

 1. our right child moves into our position
 2. we become the left child of our right child
 3. our right child's left child becomes our right

Now, the big thing you have to notice here - this left rotation HAS NOT CHANGED THE DEPTH OF THE TREE. We're no more balanced for having done it.

But - and here's the magic in AVL - if we rotated the right child to the right FIRST, what we'd have is this...


And NOW if we rotate O left, what we get is this...

    /  \
   O   RC

Magic! we've managed to get rid of a level of the tree - we've made the tree balanced.

Balancing the tree means getting rid of excess depth, and packing the upper levels more completely - which is exactly what we've just done.

That whole stuff about single/double rotations is simply that you have to have your subtree looking like this;


before you rotate - and you may have to do a right rotate to get into that state. But if you're already in that state, you only need to do the left rotate.

Remove large .pack file created by git

I am a little late for the show but in case the above answer didn't solve the query then I found another way. Simply remove the specific large file from .pack. I had this issue where I checked in a large 2GB file accidentally. I followed the steps explained in this link:

What is your favorite C programming trick?

fill in the blanks to print both 'correct' and 'wrong' below:


The answer is !printf("correct")

How to replace all double quotes to single quotes using jquery?

Use double quote to enclose the quote or escape it.

newTemp = mystring.replace(/"/g, "'");


newTemp = mystring.replace(/"/g, '\'');

How to get screen width without (minus) scrollbar?

I experienced a similar problem and doing width:100%; solved it for me. I came to this solution after trying an answer in this question and realizing that the very nature of an <iframe> will make these javascript measurement tools inaccurate without using some complex function. Doing 100% is a simple way to take care of it in an iframe. I don't know about your issue since I'm not sure of what HTML elements you are manipulating.

How to see if an object is an array without using reflection?

You can use Class.isArray()

public static boolean isArray(Object obj)
    return obj!=null && obj.getClass().isArray();

This works for both object and primitive type arrays.

For toString take a look at Arrays.toString. You'll have to check the array type and call the appropriate toString method.

How can I specify a branch/tag when adding a Git submodule?

(Git 2.22, Q2 2019, has introduced git submodule set-branch --branch aBranch -- <submodule_path>)

Note that if you have an existing submodule which isn't tracking a branch yet, then (if you have git 1.8.2+):

  • Make sure the parent repo knows that its submodule now tracks a branch:

      cd /path/to/your/parent/repo
      git config -f .gitmodules submodule.<path>.branch <branch>
  • Make sure your submodule is actually at the latest of that branch:

      cd path/to/your/submodule
      git checkout -b branch --track origin/branch
        # if the master branch already exist:
        git branch -u origin/master master

         (with 'origin' being the name of the upstream remote repo the submodule has been cloned from.
         A git remote -v inside that submodule will display it. Usually, it is 'origin')

  • Don't forget to record the new state of your submodule in your parent repo:

      cd /path/to/your/parent/repo
      git add path/to/your/submodule
      git commit -m "Make submodule tracking a branch"
  • Subsequent update for that submodule will have to use the --remote option:

      # update your submodule
      # --remote will also fetch and ensure that
      # the latest commit from the branch is used
      git submodule update --remote
      # to avoid fetching use
      git submodule update --remote --no-fetch 

Note that with Git 2.10+ (Q3 2016), you can use '.' as a branch name:

The name of the branch is recorded as submodule.<name>.branch in .gitmodules for update --remote.
A special value of . is used to indicate that the name of the branch in the submodule should be the same name as the current branch in the current repository.

But, as commented by LubosD

With git checkout, if the branch name to follow is ".", it will kill your uncommitted work!
Use git switch instead.

That means Git 2.23 (August 2019) or more.

See "Confused by git checkout"

If you want to update all your submodules following a branch:

    git submodule update --recursive --remote

Note that the result, for each updated submodule, will almost always be a detached HEAD, as Dan Cameron note in his answer.

(Clintm notes in the comments that, if you run git submodule update --remote and the resulting sha1 is the same as the branch the submodule is currently on, it won't do anything and leave the submodule still "on that branch" and not in detached head state.)

To ensure the branch is actually checked out (and that won't modify the SHA1 of the special entry representing the submodule for the parent repo), he suggests:

git submodule foreach -q --recursive 'branch="$(git config -f $toplevel/.gitmodules submodule.$name.branch)"; git switch $branch'

Each submodule will still reference the same SHA1, but if you do make new commits, you will be able to push them because they will be referenced by the branch you want the submodule to track.
After that push within a submodule, don't forget to go back to the parent repo, add, commit and push the new SHA1 for those modified submodules.

Note the use of $toplevel, recommended in the comments by Alexander Pogrebnyak.
$toplevel was introduced in git1.7.2 in May 2010: commit f030c96.

it contains the absolute path of the top level directory (where .gitmodules is).

dtmland adds in the comments:

The foreach script will fail to checkout submodules that are not following a branch.
However, this command gives you both:

 git submodule foreach -q --recursive 'branch="$(git config -f $toplevel/.gitmodules submodule.$name.branch)"; [ "$branch" = "" ] && git checkout master || git switch $branch' –

The same command but easier to read:

git submodule foreach -q --recursive \
    'branch="$(git config -f $toplevel/.gitmodules submodule.$name.branch)"; \
     [ "$branch" = "" ] && \
     git checkout master || git switch $branch' –

umläute refines dtmland's command with a simplified version in the comments:

git submodule foreach -q --recursive 'git switch $(git config -f $toplevel/.gitmodules submodule.$name.branch || echo master)'

multiple lines:

git submodule foreach -q --recursive \
  'git switch \
  $(git config -f $toplevel/.gitmodules submodule.$name.branch || echo master)'

Before Git 2.26 (Q1 2020), a fetch that is told to recursively fetch updates in submodules inevitably produces reams of output, and it becomes hard to spot error messages.

The command has been taught to enumerate submodules that had errors at the end of the operation.

See commit 0222540 (16 Jan 2020) by Emily Shaffer (nasamuffin).
(Merged by Junio C Hamano -- gitster -- in commit b5c71cc, 05 Feb 2020)

fetch: emphasize failure during submodule fetch

Signed-off-by: Emily Shaffer

In cases when a submodule fetch fails when there are many submodules, the error from the lone failing submodule fetch is buried under activity on the other submodules if more than one fetch fell back on fetch-by-oid.
Call out a failure late so the user is aware that something went wrong, and where.

Because fetch_finish() is only called synchronously by run_processes_parallel, mutexing is not required around submodules_with_errors.

Note that, with Git 2.28 (Q3 2020), Rewrite of parts of the scripted "git submodule" Porcelain command continues; this time it is "git submodule set-branch" subcommand's turn.

See commit 2964d6e (02 Jun 2020) by Shourya Shukla (periperidip).
(Merged by Junio C Hamano -- gitster -- in commit 1046282, 25 Jun 2020)

submodule: port subcommand 'set-branch' from shell to C

Mentored-by: Christian Couder
Mentored-by: Kaartic Sivaraam
Helped-by: Denton Liu
Helped-by: Eric Sunshine
Helped-by: Ðoàn Tr?n Công Danh
Signed-off-by: Shourya Shukla

Convert submodule subcommand 'set-branch' to a builtin and call it via git

Unpivot with column name

SELECT * FROM student

UNPIVOT(Marks FOR subjects in(Maths , Science , English));

Difference between View and Request scope in managed beans

A @ViewScoped bean lives exactly as long as a JSF view. It usually starts with a fresh new GET request, or with a navigation action, and will then live as long as the enduser submits any POST form in the view to an action method which returns null or void (and thus navigates back to the same view). Once you refresh the page, or return a non-null string (even an empty string!) navigation outcome, then the view scope will end.

A @RequestScoped bean lives exactly as long a HTTP request. It will thus be garbaged by end of every request and recreated on every new request, hereby losing all changed properties.

A @ViewScoped bean is thus particularly more useful in rich Ajax-enabled views which needs to remember the (changed) view state across Ajax requests. A @RequestScoped one would be recreated on every Ajax request and thus fail to remember all changed view state. Note that a @ViewScoped bean does not share any data among different browser tabs/windows in the same session like as a @SessionScoped bean. Every view has its own unique @ViewScoped bean.

See also:

String replace a Backslash

To Replace backslash at particular location:

if ((stringValue.contains("\\"))&&(stringValue.indexOf("\\", location-1)==(location-1))) {

macro - open all files in a folder

You have to add this line just before loop

    MyFile = Dir

jQuery autocomplete with callback ajax json

If you are returning a complex json object you need to modify you success function of your auto-complete as follows.

    url: "/Employees/SearchEmployees",
    dataType: "json",
    data: {
        searchText: request.term
    success: function (data) {
        response($.map(data.employees, function (item) {
            return {

Docker for Windows error: "Hardware assisted virtualization and data execution protection must be enabled in the BIOS"


I had Hyperv installed and virtualization enabled in my BIOS.

But SOLUTION A didn't work for me.

However, SOLUTION B worked like a charm.

SOLUTION B (If Hyper-V feature is already enabled but doesn't work)

Enable Hypervisor with

bcdedit /set hypervisorlaunchtype auto Now restart the system and try again.

Laravel 5.4 redirection to custom url after login

You should set $redirectTo value to route that you want redirect

$this->redirectTo = route('dashboard');

inside AuthController constructor.

 * Where to redirect users after login / registration.
 * @var string
protected $redirectTo = '/';

 * Create a new authentication controller instance.
 * @return void
public function __construct()
    $this->middleware($this->guestMiddleware(), ['except' => 'logout']);
    $this->redirectTo = route('dashboard');

Java, List only subdirectories from a directory, not files

@Mohamed Mansour you were almost there... the "dir" argument from that you were using is actually the curent path, so it will always return true. In order to see if the child is a subdirectory or not you need to test that child.

File file = new File("/path/to/directory");
String[] directories = file.list(new FilenameFilter() {
  public boolean accept(File current, String name) {
    return new File(current, name).isDirectory();

Android: how to get the current day of the week (Monday, etc...) in the user's language?

Hers's what I used to get the day names (0-6 means monday - sunday):

public static String getFullDayName(int day) {
    Calendar c = Calendar.getInstance();
    // date doesn't matter - it has to be a Monday
    // I new that first August 2011 is one ;-)
    c.set(2011, 7, 1, 0, 0, 0);
    c.add(Calendar.DAY_OF_MONTH, day);
    return String.format("%tA", c);

public static String getShortDayName(int day) {
    Calendar c = Calendar.getInstance();
    c.set(2011, 7, 1, 0, 0, 0);
    c.add(Calendar.DAY_OF_MONTH, day);
    return String.format("%ta", c);

Python math module

You need to say math.sqrt when you use it. Or, do from math import sqrt.

Hmm, I just read your question more thoroughly.... How are you importing math? I just tried import math and then math.sqrt which worked perfectly. Are you doing something like import math as m? If so, then you have to prefix the function with m (or whatever name you used after as).

pow is working because there are two versions: an always available version in __builtin__, and another version in math.

Delete last N characters from field in a SQL Server database

I got the answer to my own question, ant this is:

select reverse(stuff(reverse('a,b,c,d,'), 1, N, ''))

Where N is the number of characters to remove. This avoids to write the complex column/string twice

How do I get the current Date/time in DD/MM/YYYY HH:MM format?

The formatting can be done like this (I assumed you meant HH:MM instead of HH:SS, but it's easy to change):"%d/%m/%Y %H:%M")
#=> "14/09/2011 14:09"

Updated for the shifting:

d =
d.strftime("%d/%m/%Y %H:%M")
#=> "11/06/2017 18:11"
d.next_month.strftime("%d/%m/%Y %H:%M")
#=> "11/07/2017 18:11"

You need to require 'date' for this btw.

Reading int values from SqlDataReader

based on Sam Holder's answer, you could make an extension method for that

namespace adonet.extensions
  public static class AdonetExt
    public static int GetInt32(this SqlDataReader reader, string columnName)
      return reader.GetInt32(reader.GetOrdinal(columnName));

and use it like this

using adonet.extensions;


int farmsize = reader.GetInt32("farmsize");

assuming there is no GetInt32(string) already in SqlDataReader - if there is any, just use some other method name instead

Pass multiple optional parameters to a C# function

Use a parameter array with the params modifier:

public static int AddUp(params int[] values)
    int sum = 0;
    foreach (int value in values)
        sum += value;
    return sum;

If you want to make sure there's at least one value (rather than a possibly empty array) then specify that separately:

public static int AddUp(int firstValue, params int[] values)

(Set sum to firstValue to start with in the implementation.)

Note that you should also check the array reference for nullity in the normal way. Within the method, the parameter is a perfectly ordinary array. The parameter array modifier only makes a difference when you call the method. Basically the compiler turns:

int x = AddUp(4, 5, 6);

into something like:

int[] tmp = new int[] { 4, 5, 6 };
int x = AddUp(tmp);

You can call it with a perfectly normal array though - so the latter syntax is valid in source code as well.

How to add lines to end of file on Linux

The easiest way is to redirect the output of the echo by >>:

echo 'VNCSERVERS="1:root"' >> /etc/sysconfig/configfile
echo 'VNCSERVERARGS[1]="-geometry 1600x1200"' >> /etc/sysconfig/configfile

Epoch vs Iteration when training neural networks

I believe iteration is equivalent to a single batch forward+backprop in batch SGD. Epoch is going through the entire dataset once (as someone else mentioned).

How Do I 'git fetch' and 'git merge' from a Remote Tracking Branch (like 'git pull')

these are the commands:

git fetch origin
git merge origin/somebranch somebranch

if you do this on the second line:

git merge origin somebranch

it will try to merge the local master into your current branch.

The question, as I've understood it, was you fetched already locally and want to now merge your branch to the latest of the same branch.

How do I use .woff fonts for my website?

You need to declare @font-face like this in your stylesheet

@font-face {
  font-family: 'Awesome-Font';
  font-style: normal;
  font-weight: 400;
  src: local('Awesome-Font'), local('Awesome-Font-Regular'), url(path/Awesome-Font.woff) format('woff');

Now if you want to apply this font to a paragraph simply use it like this..

p {
font-family: 'Awesome-Font', Arial;

More Reference

How do you UrlEncode without using System.Web?

There's a client profile usable version, System.Net.WebUtility class, present in client profile System.dll. Here's the MSDN Link:


How to specify the port an ASP.NET Core application is hosted on?

In ASP.NET Core 3.1, there are 4 main ways to specify a custom port:

  • Using command line arguments, by starting your .NET application with --urls=[url]:
dotnet run --urls=http://localhost:5001/
  • Using appsettings.json, by adding a Urls node:
  "Urls": "http://localhost:5001"
  • Using environment variables, with ASPNETCORE_URLS=http://localhost:5001/.
  • Using UseUrls(), if you prefer doing it programmatically:
public static class Program
    public static void Main(string[] args) =>

    public static IHostBuilder CreateHostBuilder(string[] args) =>
            .ConfigureWebHostDefaults(builder =>

Or, if you're still using the web host builder instead of the generic host builder:

public class Program
    public static void Main(string[] args) =>
        new WebHostBuilder()

How I can check whether a page is loaded completely or not in web driver?

You can take a screenshot and save the rendered page in a location and you can check the screenshot if the page loaded completely without broken images

how to convert string to numerical values in mongodb

String can be converted to numbers in MongoDB v4.0 using $toInt operator. In this case

        $project: {
            _id: 0,
            moopNumber: { $toInt: "$moop" }


{ "moopNumber" : 1234 }

No assembly found containing an OwinStartupAttribute Error

Check if you have the Startup class created in your project. This is an example:

using Microsoft.Owin;
using Owin;

[assembly: OwinStartupAttribute(typeof({project_name}.Startup))]

namespace AuctionPortal
    public partial class Startup
        public void Configuration(IAppBuilder app)

PDF to image using Java

If GPL is fine you may have an additional look at jPodRenderer (SourceForge)

How to display image from URL on Android

You can simply use the Glide API. It avoids all the boilerplate code and the task can be achieved in two lines of code. You refer this link Enjoy

How to create file object from URL object (image)

You can convert the URL to a String and use it to create a new File. e.g.

URL url = new URL("");
File f = new File(url.getFile());

Spark SQL: apply aggregate functions to a list of columns

Another example of the same concept - but say - you have 2 different columns - and you want to apply different agg functions to each of them i.e

f.groupBy("col1").agg(sum("col2").alias("col2"), avg("col3").alias("col3"), ...)

Here is the way to achieve it - though I do not yet know how to add the alias in this case

See the example below - Using Maps

val Claim1 = StructType(Seq(StructField("pid", StringType, true),StructField("diag1", StringType, true),StructField("diag2", StringType, true), StructField("allowed", IntegerType, true), StructField("allowed1", IntegerType, true)))
val claimsData1 = Seq(("PID1", "diag1", "diag2", 100, 200), ("PID1", "diag2", "diag3", 300, 600), ("PID1", "diag1", "diag5", 340, 680), ("PID2", "diag3", "diag4", 245, 490), ("PID2", "diag2", "diag1", 124, 248))

val claimRDD1 = sc.parallelize(claimsData1)
val claimRDDRow1 = => Row(p._1, p._2, p._3, p._4, p._5))
val claimRDD2DF1 = sqlContext.createDataFrame(claimRDDRow1, Claim1)

val l = List("allowed", "allowed1")
val exprs = -> "sum")).toMap
claimRDD2DF1.groupBy("pid").agg(exprs) show false
val exprs = Map("allowed" -> "sum", "allowed1" -> "avg")

claimRDD2DF1.groupBy("pid").agg(exprs) show false

Alternate table with new not null Column in existing table in SQL

FROM syscolumns sc
JOIN sysobjects so
ON =
WHERE so.Name = 'Table1'
AND sc.Name = 'Col1')

Align vertically using CSS 3

You can vertically align by setting an element to display: inline-block, then setting vertical-align: middle;

What is Express.js?

  1. What is Express.js?

Express.js is a Node.js web application server framework, designed for building single-page, multi-page, and hybrid web applications. It is the de facto standard server framework for node.js.

Frameworks built on Express.

Several popular Node.js frameworks are built on Express:

LoopBack: Highly-extensible, open-source Node.js framework for quickly creating dynamic end-to-end REST APIs.

Sails: MVC framework for Node.js for building practical, production-ready apps.

Kraken: Secure and scalable layer that extends Express by providing structure and convention.

MEAN: Opinionated fullstack JavaScript framework that simplifies and accelerates web application development.

  1. What is the purpose of it with Node.js?
  2. Why do we actually need Express.js? How it is useful for us to use with Node.js?

Express adds dead simple routing and support for Connect middleware, allowing many extensions and useful features.

For example,

  • Want sessions? It's there
  • Want POST body / query string parsing? It's there
  • Want easy templating through jade, mustache, ejs, etc? It's there
  • Want graceful error handling that won't cause the entire server to crash?

How to disable SSL certificate checking with Spring RestTemplate?

@Bean(name = "restTemplateByPassSSL")
public RestTemplate restTemplateByPassSSL()
        throws KeyStoreException, NoSuchAlgorithmException, KeyManagementException {
    TrustStrategy acceptingTrustStrategy = (X509Certificate[] chain, String authType) -> true;
    HostnameVerifier hostnameVerifier = (s, sslSession) -> true;
    SSLContext sslContext = SSLContexts.custom().loadTrustMaterial(null, acceptingTrustStrategy).build();
    SSLConnectionSocketFactory csf = new SSLConnectionSocketFactory(sslContext, hostnameVerifier);
    CloseableHttpClient httpClient = HttpClients.custom().setSSLSocketFactory(csf).build();
    HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory();

    return new RestTemplate(requestFactory);

How to call code behind server method from a client side JavaScript function?

Try creating a new service and calling it. The processing can be done there, and returned back.

function makeCall(operation){
    var n1 = document.getElementById("num1").value;
    var n2 = document.getElementById("num2").value;
if(n1 && n2){

        // Instantiate a service proxy
        var proxy = new Service();

        // Call correct operation on vf cproxy       

            case "gridOne":
                proxy.Calculate(AjaxService.Operation.getWeather, n1, n2,
 onSuccess, onFail, null);

****HTML CODE****
<p>Major City: <input type="text" id="num1" onclick="return num1_onclick()"
<p>Country: <input type="text" id="num2" onclick="return num2_onclick()"
<input id="btnDivide" type="button" onclick="return makeCall('gridOne');" 

Fatal error: Uncaught Error: Call to undefined function mysql_connect()

mysql_* functions have been removed in PHP 7.

You now have two alternatives: MySQLi and PDO.

The following is a before (-) and after (+) comparison of a migration to the MySQLi alternative, taken straight out of working code:

-if (!$dbLink = mysql_connect($dbHost, $dbUser, $dbPass))
+if (!$dbLink = mysqli_connect($dbHost, $dbUser, $dbPass))

-if (!mysql_select_db($dbName, $dbLink))
+if (!mysqli_select_db($dbLink, $dbName))

-if (!$result = mysql_query($query, $dbLink)) {
+if (!$result = mysqli_query($dbLink, $query)) {

-if (mysql_num_rows($result) > 0) {
+if (mysqli_num_rows($result) > 0) {

-while ($row = mysql_fetch_array( $result, MYSQL_ASSOC )) {
+while ($row = mysqli_fetch_array( $result, MYSQLI_ASSOC )) {


Get screen width and height in Android

As an android official document said for the default display use Context#getDisplay() because this method was deprecated in API level 30.


This code given below is in kotlin and is written accodring to the latest version of Android help you determine width and height:

fun getWidth(context: Context): Int {
    var width:Int = 0
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
        val displayMetrics = DisplayMetrics()
        val display: Display? = context.getDisplay()
        return displayMetrics.widthPixels
        val displayMetrics = DisplayMetrics()
        width = displayMetrics.widthPixels
        return width

fun getHeight(context: Context): Int {
    var height: Int = 0
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
        val displayMetrics = DisplayMetrics()
        val display = context.display
        return displayMetrics.heightPixels
    }else {
        val displayMetrics = DisplayMetrics()
        height = displayMetrics.heightPixels
        return height

Trying to make bootstrap modal wider

If you need this solution for only few types of modals just use style="width:90%" attribute.


div class="modal-dialog modal-lg" style="width:90%"

note: this will change only this particular modal

How to fix: "You need to use a Theme.AppCompat theme (or descendant) with this activity"

Your application has an AppCompat theme


But, you overwrote the Activity (which extends AppCompatActivity) with a theme that isn't descendant of an AppCompat theme

<activity android:name=".MainActivity"
    android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >

You could define your own fullscreen theme like so (notice AppCompat in the parent=)

<style name="AppFullScreenTheme" parent="Theme.AppCompat.Light.NoActionBar">
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowActionBar">false</item>
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowContentOverlay">@null</item>

Then set that on the Activity.

<activity android:name=".MainActivity"
    android:theme="@style/AppFullScreenTheme" >

Note: There might be an AppCompat theme that's already full screen, but don't know immediately

How do I limit the number of decimals printed for a double?

Use the DecimalFormat class to format the double

How to fix "no valid 'aps-environment' entitlement string found for application" in Xcode 4.3?

Before deleting and regenerating AppIDs/Profiles, make sure your Library and Device have the same (and correct) profiles installed.

I started seeing this error after migrating to a new computer. Push had been working correctly prior to the migration.

The problem was (duh) that I hadn't imported the profiles to the Xcode library on the new machine (in Organizer/Devices under Library->Provisioning Profiles).

The confusing part was that the DEVICE already had the right profiles and they showed up as expected in build settings, so everything looked correct there, but the XCode LIBRARY didn't have them, so it was signing the app with...???

Excel VBA Run-time error '424': Object Required when trying to copy TextBox

The issue is with this line

 xlo.Worksheets(1).Cells(2, 2) = TextBox1.Text

You have the textbox defined at some other location which you are not using here. Excel is unable to find the textbox object in the current sheet while this textbox was defined in xlw.

Hence replace this with

 xlo.Worksheets(1).Cells(2, 2) = worksheets("xlw").TextBox1.Text 

MySQL error 2006: mysql server has gone away

MAMP 5.3, you will not find my.cnf and adding them does not work as that max_allowed_packet is stored in variables.

One solution can be:

  1. Go to http://localhost/phpmyadmin
  2. Go to SQL tab
  3. Run SHOW VARIABLES and check the values, if it is small then run with big values
  4. Run the following query, it set max_allowed_packet to 7gb:

    set global max_allowed_packet=268435456;

For some, you may need to increase the following values as well:

set global wait_timeout = 600;
set innodb_log_file_size =268435456;

How do I fix a "Expected Primary-expression before ')' token" error?

showInventory(player); is passing a type as parameter. That's illegal, you need to pass an object.

For example, something like:

player p;

I'm guessing you have something like this:

int main()
   player player;

which is awful. First, don't name the object the same as your type. Second, in order for the object to be visible inside the function, you'll need to pass it as parameter:

int main()
   player p;


std::string toDo(player& p) 

Visual Studio: Relative Assembly References Paths

I might be off here, but it seems that the answer is quite obvious: Look at reference paths in the project properties. In our setup I added our common repository folder, to the ref path GUI window, like so

Reference Paths in VS20xx

That way I can copy my dlls (ready for publish) to this folder and every developer now gets the updated DLL every time it builds from this folder.

If the dll is found in the Solution, the builder should prioritize the local version over the published team version.

How to sort a data frame by alphabetic order of a character variable in R?

#sort dataframe by col
sort.df <- with(df,  df[order(sortbythiscolumn) , ])

#can also sort by more than one variable: sort by col1 and then by col2
sort2.df <- with(df, df[order(col1, col2) , ])

#sort in reverse order
sort2.df <- with(df, df[order(col1, -col2) , ])

How can I determine the direction of a jQuery scroll event?

Keep it super simple:

jQuery Event Listener Way:

$(window).on('wheel', function(){

Vanilla JavaScript Event Listener Way:

  addEventListener('wheel', whichDirection, false);
} else if (window.attachEvent) {
  attachEvent('wheel', whichDirection, false);

Function Remains The Same:

function whichDirection(event){
  console.log(event + ' WheelEvent has all kinds of good stuff to work with');
  var scrollDirection = event.deltaY;
  if(scrollDirection === 1){
    console.log('meet me at the club, going down', scrollDirection);
  } else if(scrollDirection === -1) {
    console.log('Going up, on a tuesday', scrollDirection);

I wrote a more indepth post on it here ???????

Remove spaces from std::string in C++

If you want to do this with an easy macro, here's one:

#define REMOVE_SPACES(x) x.erase(std::remove(x.begin(), x.end(), ' '), x.end())

This assumes you have done #include <string> of course.

Call it like so:

std::string sName = " Example Name ";
printf("%s",sName.c_str()); // requires #include <stdio.h>

How to save a BufferedImage as a File

File outputfile = new File("image.jpg");
ImageIO.write(bufferedImage, "jpg", outputfile);

Site does not exist error for a2ensite

I have just upgraded the Ubuntu Server version from 12.04 LTS to 14.04 LTS.

Indeed, as said above, the .conf extension to Apache 2.4.x is needed to the websites vhost files that resides on sites-available directory.

Before read this question I did not have a clue what was going on with the server.

Pretty nice solution.

Just summarizing I did the following steps on Terminal:

1) Access sites-enabled folder

$ cd /etc/apache2/sites-enabled

2) Because the command a2dissite will not work with deprecated files (without .conf) remove the old website files that was published

$ sudo rm <my-old-website-without-.conf>

3) Rename the website vhost files changing its extension adding .conf to the end

$ sudo mv /etc/apache2/sites-available/mywebsite /etc/apache2/sites-available/mywebsite.conf

4) Republish the new and correct vhost file

$ sudo a2ensite mywebsite.conf

5) Check the website on browser and have fun! :)

#pragma once vs include guards?

If you're positive that you will never use this code in a compiler that doesn't support it (Windows/VS, GCC, and Clang are examples of compilers that do support it), then you can certainly use #pragma once without worries.

You can also just use both (see example below), so that you get portability and compilation speedup on compatible systems

#pragma once
#ifndef _HEADER_H_
#define _HEADER_H_



Using boolean values in C

Here is the version that I used:

typedef enum { false = 0, true = !false } bool;

Because false only has one value, but a logical true could have many values, but technique sets true to be what the compiler will use for the opposite of false.

This takes care of the problem of someone coding something that would come down to this:

if (true == !false)

I think we would all agree that that is not a good practice, but for the one time cost of doing "true = !false" we eliminate that problem.

[EDIT] In the end I used:

typedef enum { myfalse = 0, mytrue = !myfalse } mybool;

to avoid name collision with other schemes that were defining true and false. But the concept remains the same.

[EDIT] To show conversion of integer to boolean:

mybool somebool;
int someint = 5;
somebool = !!someint;

The first (right most) ! converts the non-zero integer to a 0, then the second (left most) ! converts the 0 to a myfalse value. I will leave it as an exercise for the reader to convert a zero integer.

[EDIT] It is my style to use the explicit setting of a value in an enum when the specific value is required even if the default value would be the same. Example: Because false needs to be zero I use false = 0, rather than false,

Global constants file in Swift


import Foundation

let kBaseURL = NSURL(string: "")


var manager = AFHTTPRequestOperationManager(baseURL: kBaseURL)

How to query values from xml nodes?

Try this:

SELECT RawXML.value('(/GrobXmlFile//Grob//ReportHeader//OrganizationReportReferenceIdentifier/node())[1]','varchar(50)') AS ReportIdentifierNumber,
       RawXML.value('(/GrobXmlFile//Grob//ReportHeader//OrganizationNumber/node())[1]','int') AS OrginazationNumber
FROM Batches

How to detect simple geometric shapes using OpenCV

You can also use template matching to detect shapes inside an image.

Generate random 5 characters string

It seems like str_shuffle would be a good use for this. Seed the shuffle with whichever characters you want.

$my_rand_strng = substr(str_shuffle("ABCDEFGHIJKLMNOPQRSTUVWXYZ"), -5);

Java: print contents of text file to screen

Before Java 7:

 BufferedReader br = new BufferedReader(new FileReader("foo.txt"));
 String line;
 while ((line = br.readLine()) != null) {
  • add exception handling
  • add closing the stream

Since Java 7, there is no need to close the stream, because it implements autocloseable

try (BufferedReader br = new BufferedReader(new FileReader("foo.txt"))) {
   String line;
   while ((line = br.readLine()) != null) {

How do I set the value property in AngularJS' ng-options?

It is always painful for developers to with ng-options. For example: Getting an empty/blank selected value in the select tag. Especially when dealing with JSON objects in ng-options, it becomes more tedious. Here I have done some exercises on that.

Objective: Iterate array of JSON objects through ng-option and set selected first element.


someNames = [{"id":"1", "someName":"xyz"}, {"id":"2", "someName":"abc"}]

In the select tag I had to show xyz and abc, where xyz must be selected without much effort.


<pre class="default prettyprint prettyprinted" style=""><code>
    &lt;select class="form-control" name="test" style="width:160px"    ng-options="name.someName for name in someNames" ng-model="testModel.test" ng-selected = "testModel.test = testModel.test || someNames[0]"&gt;

By above code sample, you might get out of this exaggeration.

Another reference:

R color scatter plot points based on values

Also it'd work to just specify ifelse() twice:

plot(pos,cn, col= ifelse(cn >= 3, "red", ifelse(cn <= 1,"blue", "black")), ylim = c(0, 10))

Django - Reverse for '' not found. '' is not a valid view function or pattern name

Give the same name in

 path('detail/<int:id>', views.detail, name="detail"),

changing iframe source with jquery

Should work.

Here's a working example:


function loadIframe(iframeName, url) {
    var $iframe = $('#' + iframeName);
    if ($iframe.length) {
        return false;
    return true;

How do I set a checkbox in razor view?

I had the same issue, luckily I found the below code

@Html.CheckBoxFor(model => model.As, htmlAttributes: new { @checked = true} )

Check Box Checked By Default - Razor Solution

jQuery issue - #<an Object> has no method

This usually has to do with a selector not being used properly. Check and make sure that you are using the jQuery selectors like intended. For example I had this problem when creating a click method:

$("[editButton]").click(function () {
    this.css("color", "red");

Because I was not using the correct selector method $(this) for jQuery it gave me the same error.

So simply enough, check your selectors!

How to append to the end of an empty list?

append actually changes the list. Also, it takes an item, not a list. Hence, all you need is

for i in range(n):

(By the way, note that you can use range(n), in this case.)

I assume your actual use is more complicated, but you may be able to use a list comprehension, which is more pythonic for this:

list1 = [i for i in range(n)]

Or, in this case, in Python 2.x range(n) in fact creates the list that you want already, although in Python 3.x, you need list(range(n)).

How to create byte array from HttpPostedFile

Use a BinaryReader object to return a byte array from the stream like:

byte[] fileData = null;
using (var binaryReader = new BinaryReader(Request.Files[0].InputStream))
    fileData = binaryReader.ReadBytes(Request.Files[0].ContentLength);

C# Create New T()

To get this i tried following code :

  protected T GetObject<T>()
        T obj = default(T);
        obj =Activator.CreateInstance<T>();
        return obj ;

Selecting multiple columns in a Pandas dataframe

Starting with 0.21.0, using .loc or [] with a list with one or more missing labels is deprecated in favor of .reindex. So, the answer to your question is:

df1 = df.reindex(columns=['b','c'])

In prior versions, using .loc[list-of-labels] would work as long as at least one of the keys was found (otherwise it would raise a KeyError). This behavior is deprecated and now shows a warning message. The recommended alternative is to use .reindex().

Read more at Indexing and Selecting Data.

How to delete a specific file from folder using

string sourceDir = @"c:\current";
string backupDir = @"c:\archives\2008";

    string[] picList = Directory.GetFiles(sourceDir, "*.jpg");
    string[] txtList = Directory.GetFiles(sourceDir, "*.txt");

    // Copy picture files. 
    foreach (string f in picList)
        // Remove path from the file name. 
        string fName = f.Substring(sourceDir.Length + 1);

        // Use the Path.Combine method to safely append the file name to the path. 
        // Will overwrite if the destination file already exists.
        File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName), true);

    // Copy text files. 
    foreach (string f in txtList)

        // Remove path from the file name. 
        string fName = f.Substring(sourceDir.Length + 1);

            // Will not overwrite if the destination file already exists.
            File.Copy(Path.Combine(sourceDir, fName), Path.Combine(backupDir, fName));

        // Catch exception if the file was already copied. 
        catch (IOException copyError)

    // Delete source files that were copied. 
    foreach (string f in txtList)
    foreach (string f in picList)

catch (DirectoryNotFoundException dirNotFound)

Laravel Eloquent - distinct() and count() not working properly together

Anyone else come across this post, and not finding the other suggestions to work?

Depending on the specific query, a different approach may be needed. In my case, I needed either count the results of a GROUP BY, e.g.




After some puzzling around, I realised there was no built-in Laravel function for either of these. So the simplest solution was to use use DB::raw with the count method.

$count = $builder->count(DB::raw('DISTINCT b'));

Remember, don't use groupBy before calling count. You can apply groupBy later, if you need it for getting rows.

How to use multiprocessing with multiple arguments?

The answer to this is version- and situation-dependent. The most general answer for recent versions of Python (since 3.3) was first described below by J.F. Sebastian.1 It uses the Pool.starmap method, which accepts a sequence of argument tuples. It then automatically unpacks the arguments from each tuple and passes them to the given function:

import multiprocessing
from itertools import product

def merge_names(a, b):
    return '{} & {}'.format(a, b)

if __name__ == '__main__':
    names = ['Brown', 'Wilson', 'Bartlett', 'Rivera', 'Molloy', 'Opie']
    with multiprocessing.Pool(processes=3) as pool:
        results = pool.starmap(merge_names, product(names, repeat=2))

# Output: ['Brown & Brown', 'Brown & Wilson', 'Brown & Bartlett', ...

For earlier versions of Python, you'll need to write a helper function to unpack the arguments explicitly. If you want to use with, you'll also need to write a wrapper to turn Pool into a context manager. (Thanks to muon for pointing this out.)

import multiprocessing
from itertools import product
from contextlib import contextmanager

def merge_names(a, b):
    return '{} & {}'.format(a, b)

def merge_names_unpack(args):
    return merge_names(*args)

def poolcontext(*args, **kwargs):
    pool = multiprocessing.Pool(*args, **kwargs)
    yield pool

if __name__ == '__main__':
    names = ['Brown', 'Wilson', 'Bartlett', 'Rivera', 'Molloy', 'Opie']
    with poolcontext(processes=3) as pool:
        results =, product(names, repeat=2))

# Output: ['Brown & Brown', 'Brown & Wilson', 'Brown & Bartlett', ...

In simpler cases, with a fixed second argument, you can also use partial, but only in Python 2.7+.

import multiprocessing
from functools import partial
from contextlib import contextmanager

def poolcontext(*args, **kwargs):
    pool = multiprocessing.Pool(*args, **kwargs)
    yield pool

def merge_names(a, b):
    return '{} & {}'.format(a, b)

if __name__ == '__main__':
    names = ['Brown', 'Wilson', 'Bartlett', 'Rivera', 'Molloy', 'Opie']
    with poolcontext(processes=3) as pool:
        results =, b='Sons'), names)

# Output: ['Brown & Sons', 'Wilson & Sons', 'Bartlett & Sons', ...

1. Much of this was inspired by his answer, which should probably have been accepted instead. But since this one is stuck at the top, it seemed best to improve it for future readers.

How to AUTO_INCREMENT in db2?

hi If you are still not able to make column as AUTO_INCREMENT while creating table. As a work around first create table that is:

create table student( sid integer NOT NULL sname varchar(30), PRIMARY KEY (sid) );

and then explicitly try to alter column bu using the following

alter table student alter column sid set GENERATED BY DEFAULT AS IDENTITY


alter table student alter column sid set GENERATED BY DEFAULT AS IDENTITY (start with 100)

How to install a Python module via its in Windows? is designed to be run from the command line. You'll need to open your command prompt (In Windows 7, hold down shift while right-clicking in the directory with the file. You should be able to select "Open Command Window Here").

From the command line, you can type

python --help get a list of commands. What you are looking to do is...

python install

Defining an abstract class without any abstract methods

Yes, you can declare a class you cannot instantiate by itself with only methods that already have implementations. This would be useful if you wanted to add abstract methods in the future, or if you did not want the class to be directly instantiated even though it has no abstract properties.

How to scroll to an element in jQuery?

Check out jquery-scrollintoview.

ScrollTo is fine, but oftentimes you just want to make sure a UI element is visible, not necessarily at the top. ScrollTo doesn't help you with this. From scrollintoview's README:

How does this plugin solve the user experience issue

This plugin scrolls a particular element into view similar to browser built-in functionality (DOM's scrollIntoView() function), but works differently (and arguably more user friendly):

  • it only scrolls to element when element is actually out of view; if element is in view (anywhere in visible document area), no scrolling will be performed;
  • it scrolls using animation effects; when scrolling is performed users know exactly they're not redirected anywhere, but actually see that they're simply moved somewhere else within the same page (as well as in which direction they moved);
  • there's always the smallest amount of scrolling being applied; when element is above the visible document area it will be scrolled to the top of visible area; when element is below the visible are it will be scrolled to the bottom of visible area; this is the most consistent way of scrolling - when scrolling would always be to top it sometimes couldn't scroll an element to top when it was close to the bottom of scrollable container (thus scrolling would be unpredictable);
  • when element's size exceeds the size of visible document area its top-left corner is the one that will be scrolled to;

isPrime Function for Python Language

Of many prime number tests floating around the Internet, consider the following Python function:

def is_prime(n):
  if n == 2 or n == 3: return True
  if n < 2 or n%2 == 0: return False
  if n < 9: return True
  if n%3 == 0: return False
  r = int(n**0.5)
  # since all primes > 3 are of the form 6n ± 1
  # start with f=5 (which is prime)
  # and test f, f+2 for being prime
  # then loop by 6. 
  f = 5
  while f <= r:
    if n % f == 0: return False
    if n % (f+2) == 0: return False
    f += 6
  return True    

Since all primes > 3 are of the form 6n ± 1, once we eliminate that n is:

  1. not 2 or 3 (which are prime) and
  2. not even (with n%2) and
  3. not divisible by 3 (with n%3) then we can test every 6th n ± 1.

Consider the prime number 5003:

print is_prime(5003)



The line r = int(n**0.5) evaluates to 70 (the square root of 5003 is 70.7318881411 and int() truncates this value)

Consider the next odd number (since all even numbers other than 2 are not prime) of 5005, same thing prints:


The limit is the square root since x*y == y*x The function only has to go 1 loop to find that 5005 is divisible by 5 and therefore not prime. Since 5 X 1001 == 1001 X 5 (and both are 5005), we do not need to go all the way to 1001 in the loop to know what we know at 5!

Now, let's look at the algorithm you have:

def isPrime(n):
    for i in range(2, int(n**0.5)+1):
        if n % i == 0:
            return False

    return True

There are two issues:

  1. It does not test if n is less than 2, and there are no primes less than 2;
  2. It tests every number between 2 and n**0.5 including all even and all odd numbers. Since every number greater than 2 that is divisible by 2 is not prime, we can speed it up a little by only testing odd numbers greater than 2.


def isPrime2(n):
    if n==2 or n==3: return True
    if n%2==0 or n<2: return False
    for i in range(3, int(n**0.5)+1, 2):   # only odd numbers
        if n%i==0:
            return False    

    return True

OK -- that speeds it up by about 30% (I benchmarked it...)

The algorithm I used is_prime is about 2x times faster still, since only every 6th integer is looping through the loop. (Once again, I benchmarked it.)

Side note: x**0.5 is the square root:

>>> import math
>>> math.sqrt(100)==100**0.5

Side note 2: primality testing is an interesting problem in computer science.

Java current machine name and logged in user?

To get the currently logged in user:


To get the host name of the machine:


To answer the last part of your question, the Java API says that getHostName() will return

the host name for this IP address, or if the operation is not allowed by the security check, the textual representation of the IP address.

How can one see the structure of a table in SQLite?

If you are using PHP you can get it this way:

    $dbname = 'base.db';
    $db = new SQLite3($dbname);
    $sturturequery = $db->query("SELECT sql FROM sqlite_master WHERE name='foo'");

    $table = $sturturequery->fetchArray();
    echo '<pre>' . $table['sql'] . '</pre>';


Can I extend a class using more than 1 class in PHP?

Not knowing exactly what you're trying to achieve, I would suggest looking into the possibility of redesigning you application to use composition rather than inheritance in this case.

How to add a border to a widget in Flutter?

Best way is using BoxDecoration()


  • You can set border of widget
  • You can set border Color or Width
  • You can set Rounded corner of border
  • You can add Shadow of widget


  • BoxDecoration only use with Container widget so you want to wrap your widget in Container()


      margin: EdgeInsets.all(10),
      padding: EdgeInsets.all(10),
      decoration: BoxDecoration(
        border: Border.all(
            color:[800],// set border color
            width: 3.0),   // set border width
        borderRadius: BorderRadius.all(
            Radius.circular(10.0)), // set rounded corner radius
        boxShadow: [BoxShadow(blurRadius: 10,color:,offset: Offset(1,3))]// make rounded corner of border
      child: Text("My demo styling"),

enter image description here

List attributes of an object

It's often mentioned that to list a complete list of attributes you should use dir(). Note however that contrary to popular belief dir() does not bring out all attributes. For example you might notice that __name__ might be missing from a class's dir() listing even though you can access it from the class itself. From the doc on dir() (Python 2, Python 3):

Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases. For example, metaclass attributes are not in the result list when the argument is a class.

A function like the following tends to be more complete, although there's no guarantee of completeness since the list returned by dir() can be affected by many factors including implementing the __dir__() method, or customizing __getattr__() or __getattribute__() on the class or one of its parents. See provided links for more details.

def dirmore(instance):
    visible = dir(instance)
    visible += [a for a in set(dir(type)).difference(visible)
                if hasattr(instance, a)]
    return sorted(visible)

Input text dialog Android

Sounds like a good opportunity to use an AlertDialog.

As basic as it seems, Android does not have a built-in dialog to do this (as far as I know). Fortunately, it's just a little extra work on top of creating a standard AlertDialog. You simply need to create an EditText for the user to input data, and set it as the view of the AlertDialog. You can customize the type of input allowed using setInputType, if you need.

If you're able to use a member variable, you can simply set the variable to the value of the EditText, and it will persist after the dialog has dismissed. If you can't use a member variable, you may need to use a listener to send the string value to the right place. (I can edit and elaborate more if this is what you need).

Within your class:

private String m_Text = "";

Within the OnClickListener of your button (or in a function called from there):

AlertDialog.Builder builder = new AlertDialog.Builder(this);

// Set up the input
final EditText input = new EditText(this);
// Specify the type of input expected; this, for example, sets the input as a password, and will mask the text

// Set up the buttons
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 
    public void onClick(DialogInterface dialog, int which) {
        m_Text = input.getText().toString();
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int which) {

When must we use NVARCHAR/NCHAR instead of VARCHAR/CHAR in SQL Server?

Unicode - (nchar, nvarchar, and ntext)
Non-unicode - (char, varchar, and text).


Collations in SQL Server provide sorting rules, case, and accent sensitivity properties for your data. Collations that are used with character data types such as char and varchar dictate the code page and corresponding characters that can be represented for that data type.

Assuming you are using default SQL collation SQL_Latin1_General_CP1_CI_AS then following script should print out all the symbols that you can fit in VARCHAR since it uses one byte to store one character (256 total) if you don't see it on the list printed - you need NVARCHAR.

declare @i int = 0;
while (@i < 256)
print cast(@i as varchar(3)) + '  '+  char(@i)  collate SQL_Latin1_General_CP1_CI_AS 
print cast(@i as varchar(3)) + '  '+ char(@i)  collate Japanese_90_CI_AS  
set @i = @i+1;

If you change collation to lets say japanese you will notice that all the weird European letters turned into normal and some symbols into ? marks.

Unicode is a standard for mapping code points to characters. Because it is designed to cover all the characters of all the languages of the world, there is no need for different code pages to handle different sets of characters. If you store character data that reflects multiple languages, always use Unicode data types (nchar, nvarchar, and ntext) instead of the non-Unicode data types (char, varchar, and text).

Otherwise your sorting will go weird.

entity object cannot be referenced by multiple instances of IEntityChangeTracker. while adding related objects to entity in Entity Framework 4.1

In this case, it turns out the error is very clear: Entity Framework cannot track an entity using multiple instances of IEntityChangeTracker or typically, multiple instances of DbContext. The solutions are: use one instance of DbContext; access all needed entities through a single repository (depending on one instance of DbContext); or turning off tracking for all entities accessed via a repository other than the one throwing this particular exception.

When following an inversion of control pattern in .Net Core Web API, I frequently find that I have controllers with dependencies such as:

private readonly IMyEntityRepository myEntityRepo; // depends on MyDbContext
private readonly IFooRepository fooRepo; // depends on MyDbContext
private readonly IBarRepository barRepo; // depends on MyDbContext
public MyController(
    IMyEntityRepository myEntityRepo, 
    IFooRepository fooRepo, 
    IBarRepository barRepo)
    this.fooRepo = fooRepo;
    this.barRepo = barRepo;
    this.myEntityRepo = myEntityRepo;

and usage like

myEntity.Foo = await this.fooRepository.GetFoos().SingleOrDefaultAsync(f => f.Id == model.FooId);
if (model.BarId.HasValue)
    myEntity.Foo.Bar = await this.barRepository.GetBars().SingleOrDefaultAsync(b => b.Id == model.BarId.Value);

await this.myEntityRepo.UpdateAsync(myEntity); // this throws an error!

Since all three repositories depend on different DbContext instances per request, I have two options to avoid the problem and maintain separate repositories: change the injection of the DbContext to create a new instance only once per call:

// services.AddTransient<DbContext, MyDbContext>(); <- one instance per ctor. bad
services.AddScoped<DbContext, MyDbContext>(); // <- one instance per call. good!

or, if the child entity is being used in a read-only manner, turning off tracking on that instance:

myEntity.Foo.Bar = await this.barRepo.GetBars().AsNoTracking().SingleOrDefault(b => b.Id == model.BarId);

How to compare LocalDate instances Java 8

Using equals() LocalDate does override equals:

int compareTo0(LocalDate otherDate) {
    int cmp = (year - otherDate.year);
    if (cmp == 0) {
        cmp = (month - otherDate.month);
        if (cmp == 0) {
            cmp = (day -;
    return cmp;

If you are not happy with the result of equals(), you are good using the predefined methods of LocalDate.

Notice that all of those method are using the compareTo0() method and just check the cmp value. if you are still getting weird result (which you shouldn't), please attach an example of input and output

Maximum concurrent connections to MySQL

You might have 10,000 users total, but that's not the same as concurrent users. In this context, concurrent scripts being run.

For example, if your visitor visits index.php, and it makes a database query to get some user details, that request might live for 250ms. You can limit how long those MySQL connections live even further by opening and closing them only when you are querying, instead of leaving it open for the duration of the script.

While it is hard to make any type of formula to predict how many connections would be open at a time, I'd venture the following:

You probably won't have more than 500 active users at any given time with a user base of 10,000 users. Of those 500 concurrent users, there will probably at most be 10-20 concurrent requests being made at a time.

That means, you are really only establishing about 10-20 concurrent requests.

As others mentioned, you have nothing to worry about in that department.

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

Note that the TIMEDIFF() solution only works when the datetimes are less than 35 days apart! TIMEDIFF() returns a TIME datatype, and the max value for TIME is 838:59:59 hours (=34,96 days)

Global variables in R

What about .GlobalEnv$a <- "new" ? I saw this explicit way of creating a variable in a certain environment here: It seems shorter than using the assign() function.

Git clone particular version of remote repository

If that version you need to obtain is either a branch or a tag then:

git clone -b branch_or_tag_name repo_address_or_path

Wait for Angular 2 to load/resolve model before rendering view/template

Implement the routerOnActivate in your @Component and return your promise:

EDIT: This explicitly does NOT work, although the current documentation can be a little hard to interpret on this topic. See Brandon's first comment here for more information:

EDIT: The related information on the otherwise-usually-accurate Auth0 site is not correct:

EDIT: The angular team is planning a @Resolve decorator for this purpose.

What is the memory consumption of an object in Java?

I've gotten very good results from the java.lang.instrument.Instrumentation approach mentioned in another answer. For good examples of its use, see the entry, Instrumentation Memory Counter from the JavaSpecialists' Newsletter and the java.sizeOf library on SourceForge.

Traverse all the Nodes of a JSON Object Tree with JavaScript

             var localdata = [{''}]// Your json array
              for (var j = 0; j < localdata.length; j++) 
                 $('#tbl').append('<tr><td>' + item.FirstName +'</td></tr>);

Using multiple property files (via PropertyPlaceholderConfigurer) in multiple projects/modules

I tried the solution below, it works on my machine.

<context:property-placeholder location="classpath*" ignore-unresolvable="true" order="1" />

<context:property-placeholder location="classpath*" order="2"/>

In case multiple elements are present in the Spring context, there are a few best practices that should be followed:

the order attribute needs to be specified to fix the order in which these are processed by Spring all property placeholders minus the last one (highest order) should have ignore-unresolvable=”true” to allow the resolution mechanism to pass to others in the context without throwing an exception


HTML-Tooltip position relative to mouse pointer

You can use jQuery UI plugin, following are reference URLs

Set track to TRUE for Tooltip position relative to mouse pointer eg.

$('.tooltip').tooltip({ track: true });

Excel how to find values in 1 column exist in the range of values in another

Use the formula by tigeravatar:

=COUNTIF($B$2:$B$5,A2)>0 – tigeravatar Aug 28 '13 at 14:50

as conditional formatting. Highlight column A. Choose conditional formatting by forumula. Enter the formula (above) - this finds values in col B that are also in A. Choose a format (I like to use FILL and a bold color).

To find all of those values, highlight col A. Data > Filter and choose Filter by color.

Loop Through All Subfolders Using VBA

And to complement Rich's recursive answer, a non-recursive method.

Public Sub NonRecursiveMethod()
    Dim fso, oFolder, oSubfolder, oFile, queue As Collection

    Set fso = CreateObject("Scripting.FileSystemObject")
    Set queue = New Collection
    queue.Add fso.GetFolder("your folder path variable") 'obviously replace

    Do While queue.Count > 0
        Set oFolder = queue(1)
        queue.Remove 1 'dequeue
        '...insert any folder processing code here...
        For Each oSubfolder In oFolder.SubFolders
            queue.Add oSubfolder 'enqueue
        Next oSubfolder
        For Each oFile In oFolder.Files
            '...insert any file processing code here...
        Next oFile

End Sub

You can use a queue for FIFO behaviour (shown above), or you can use a stack for LIFO behaviour which would process in the same order as a recursive approach (replace Set oFolder = queue(1) with Set oFolder = queue(queue.Count) and replace queue.Remove(1) with queue.Remove(queue.Count), and probably rename the variable...)

Scrollview can host only one direct child

Wrap all the children inside of another LinearLayout with wrap_content for both the width and the height as well as the vertical orientation.

CSS vertical alignment of inline/inline-block elements

Simply floating both elements left achieves the same result.

div {

a {
border:solid black 1px;

span {

Where can I find a list of keyboard keycodes?

I know this was asked awhile back, but I found a comprehensive list of the virtual keyboard key codes right in MSDN, for use in C/C++. This also includes the mouse events. Note it is different than the javascript key codes (I noticed it around the VK_OEM section).

Here's the link:

Can't start Eclipse - Java was started but returned exit code=13

If you install a 64-bit Eclipse version on a PC with a 32-bit JRE this is guaranteed to occur.

So the solution is quite straightforward: You need to synchronise them by updating either one. This shall happen when downloading Oracle Fusion middleware and Eclipse expects a 32-bit environment while your JRE is 64-bit and your JAVA home is pointing to a 64-bit JDK.

phpmyadmin "no data received to import" error, how to fix?

If you are using xampp you can find php.ini file by going into xampp control panel and and clicking config button in front of Apache.

How to change background and text colors in Sublime Text 3

For How do I change the overall colors (background and font)?

For MAC : goto Sublime text -> Preferences -> color scheme

How to export non-exportable private key from store

You might need to uninstall antivirus (in my case I had to get rid of Avast).

This makes sure that crypto::cng command will work. Otherwise it was giving me errors:

mimikatz $ crypto::cng
ERROR kull_m_patch_genericProcessOrServiceFromBuild ; OpenProcess (0x00000005)

After removing Avast:

mimikatz $ crypto::cng
"KeyIso" service patched

Magic. (:


Windows Defender is another program blocking the program to work, so you will need also to disable it for the time of using program at least.

JavaScript ES6 promise for loop

As you already hinted in your question, your code creates all promises synchronously. Instead they should only be created at the time the preceding one resolves.

Secondly, each promise that is created with new Promise needs to be resolved with a call to resolve (or reject). This should be done when the timer expires. That will trigger any then callback you would have on that promise. And such a then callback (or await) is a necessity in order to implement the chain.

With those ingredients, there are several ways to perform this asynchronous chaining:

  1. With a for loop that starts with an immediately resolving promise

  2. With Array#reduce that starts with an immediately resolving promise

  3. With a function that passes itself as resolution callback

  4. With ECMAScript2017's async / await syntax

  5. With ECMAScript2020's for await...of syntax

See a snippet and comments for each of these options below.

1. With for

You can use a for loop, but you must make sure it doesn't execute new Promise synchronously. Instead you create an initial immediately resolving promise, and then chain new promises as the previous ones resolve:

for (let i = 0, p = Promise.resolve(); i < 10; i++) {
    p = p.then(_ => new Promise(resolve =>
        setTimeout(function () {
        }, Math.random() * 1000)

2. With reduce

This is just a more functional approach to the previous strategy. You create an array with the same length as the chain you want to execute, and start out with an immediately resolving promise:

[...Array(10)].reduce( (p, _, i) => 
    p.then(_ => new Promise(resolve =>
        setTimeout(function () {
        }, Math.random() * 1000)
, Promise.resolve() );

This is probably more useful when you actually have an array with data to be used in the promises.

3. With a function passing itself as resolution-callback

Here we create a function and call it immediately. It creates the first promise synchronously. When it resolves, the function is called again:

(function loop(i) {
    if (i < 10) new Promise((resolve, reject) => {
        setTimeout( () => {
        }, Math.random() * 1000);
    }).then(loop.bind(null, i+1));

This creates a function named loop, and at the very end of the code you can see it gets called immediately with argument 0. This is the counter, and the i argument. The function will create a new promise if that counter is still below 10, otherwise the chaining stops.

The call to resolve() will trigger the then callback which will call the function again. loop.bind(null, i+1) is just a different way of saying _ => loop(i+1).

4. With async/await

Modern JS engines support this syntax:

(async function loop() {
    for (let i = 0; i < 10; i++) {
        await new Promise(resolve => setTimeout(resolve, Math.random() * 1000));

It may look strange, as it seems like the new Promise() calls are executed synchronously, but in reality the async function returns when it executes the first await. Every time an awaited promise resolves, the function's running context is restored, and proceeds after the await, until it encounters the next one, and so it continues until the loop finishes.

As it may be a common thing to return a promise based on a timeout, you could create a separate function for generating such a promise. This is called promisifying a function, in this case setTimeout. It may improve the readability of the code:

const delay = ms => new Promise(resolve => setTimeout(resolve, ms));

(async function loop() {
    for (let i = 0; i < 10; i++) {
        await delay(Math.random() * 1000);

5. With for await...of

With EcmaScript 2020, the for await...of found its way to modern JavaScript engines. Although it does not really reduce code in this case, it allows to isolate the definition of the random interval chain from the actual iteration of it:

const delay = ms => new Promise(resolve => setTimeout(resolve, ms));
async function * randomDelays(count ,max) {
    for (let i = 0; i < count; i++) yield delay(Math.random() * max).then(() => i);

(async function loop() {
    for await (let i of randomDelays(10, 1000)) console.log(i);

What exactly is an instance in Java?

The main differnece is when you say ClassName obj = null; you are just creating an object for that class. It's not an instance of that class.

This statement will just allot memory for the static meber variables, not for the normal member variables.

But when you say ClassName obj = new ClassName(); you are creating an instance of the class. This staement will allot memory all member variables.

How to get a Static property with Reflection

Ok so the key for me was to use the .FlattenHierarchy BindingFlag. I don't really know why I just added it on a hunch and it started working. So the final solution that allows me to get Public Instance or Static Properties is:

obj.GetType.GetProperty(propName, Reflection.BindingFlags.Public _
  Or Reflection.BindingFlags.Static Or Reflection.BindingFlags.Instance Or _

How to format a Java string with leading zero?

You can use this:

org.apache.commons.lang.StringUtils.leftPad("Apple", 8, "0")

Mysql - How to quit/exit from stored procedure

This works for me :

 CREATE DEFINER=`root`@`%` PROCEDURE `save_package_as_template`( IN package_id int , 
IN bus_fun_temp_id int  , OUT o_message VARCHAR (50) ,
            OUT o_number INT )

DECLARE  v_pkg_name  varchar(50) ;

DECLARE  v_pkg_temp_id  int(10)  ; 

DECLARE  v_workflow_count INT(10);

-- checking if workflow created for package
select count(*)  INTO v_workflow_count from workflow w where w.package_id = 
package_id ;

this_proc:BEGIN   -- this_proc block start here 

 IF  v_workflow_count = 0 THEN
   select 'no work flow ' as 'workflow_status' ;
    SET o_message ='Work flow is not created for this package.';
    SET  o_number = -2 ;
      LEAVE this_proc;

select 'work flow  created ' as 'workflow_status' ;
-- To  send some message
SET o_message ='SUCCESSFUL';
SET  o_number = 1 ;

  END ;-- this_proc block end here 


Failed to install *.apk on device 'emulator-5554': EOF

Neither above helped me, instead, I connected my phone through the back USB hubs (I used forward USB hubs previously), and this helped me!

Exit while loop by user hitting ENTER key

If you want your user to press enter, then the raw_input() will return "", so compare the User with "":

User = raw_input('Press enter to exit...')
running = 1
while running == 1:
    Run your program
if User == "":
    running == 1

Set width of a "Position: fixed" div relative to parent div

There is an easy solution for this.

I have used a fixed position for parent div and a max-width for the contents.

You don't need to think about too much about other containers because fixed position only relative to the browser window.

            background: red;_x000D_
        .fixed .content{_x000D_
            max-width: 500px;_x000D_
            margin: 0 auto;_x000D_
            text-align: center;_x000D_
            padding: 20px 0;_x000D_
<div class="fixed">_x000D_
  <div class="content">_x000D_
     This is my content_x000D_

UnsupportedClassVersionError unsupported major.minor version 51.0 unable to load class

Try adding the following to your eclipse.ini file:

C:\Program Files\Java\jdk1.7.0_01\bin\java.exe

You might also have to change the Dosgi.requiredJavaVersion to 1.7 in the same file.

Search all tables, all columns for a specific value SQL Server

I've just updated my blog post to correct the error in the script that you were having Jeff, you can see the updated script here: Search all fields in SQL Server Database

As requested, here's the script in case you want it but I'd recommend reviewing the blog post as I do update it from time to time

DECLARE @SearchStr nvarchar(100)
SET @SearchStr = '## YOUR STRING HERE ##'
-- Copyright © 2002 Narayana Vyas Kondreddi. All rights reserved.
-- Purpose: To search all columns of all tables for a given search string
-- Written by: Narayana Vyas Kondreddi
-- Site:
-- Updated and tested by Tim Gaunt
-- Tested on: SQL Server 7.0, SQL Server 2000, SQL Server 2005 and SQL Server 2010
-- Date modified: 03rd March 2011 19:00 GMT
CREATE TABLE #Results (ColumnName nvarchar(370), ColumnValue nvarchar(3630))
DECLARE @TableName nvarchar(256), @ColumnName nvarchar(128), @SearchStr2 nvarchar(110)
SET  @TableName = ''
SET @SearchStr2 = QUOTENAME('%' + @SearchStr + '%','''')
    SET @ColumnName = ''
    SET @TableName = 
        WHERE         TABLE_TYPE = 'BASE TABLE'
            AND    OBJECTPROPERTY(
                        QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME)
                         ), 'IsMSShipped'
                           ) = 0
    WHILE (@TableName IS NOT NULL) AND (@ColumnName IS NOT NULL)
        SET @ColumnName =
            WHERE         TABLE_SCHEMA    = PARSENAME(@TableName, 2)
                AND    TABLE_NAME    = PARSENAME(@TableName, 1)
                AND    DATA_TYPE IN ('char', 'varchar', 'nchar', 'nvarchar', 'int', 'decimal')
                AND    QUOTENAME(COLUMN_NAME) > @ColumnName
        IF @ColumnName IS NOT NULL
            INSERT INTO #Results
                'SELECT ''' + @TableName + '.' + @ColumnName + ''', LEFT(' + @ColumnName + ', 3630) FROM ' + @TableName + ' (NOLOCK) ' +
                ' WHERE ' + @ColumnName + ' LIKE ' + @SearchStr2
SELECT ColumnName, ColumnValue FROM #Results

How to generate the whole database script in MySQL Workbench?

there is data export option in MySQL workbech

enter image description here

What to do on TransactionTooLargeException

This exception is typically thrown when the app is being sent to the background.

So I've decided to use the data Fragment method to completely circumvent the onSavedInstanceStae lifecycle. My solution also handles complex instance states and frees memory ASAP.

First I've created a simple Fargment to store the data:

package info.peakapps.peaksdk.logic;
import android.os.Bundle;

 * A neat trick to avoid TransactionTooLargeException while saving our instance state

public class SavedInstanceFragment extends Fragment {

    private static final String TAG = "SavedInstanceFragment";
    private Bundle mInstanceBundle = null;

    public SavedInstanceFragment() { // This will only be called once be cause of setRetainInstance()
        setRetainInstance( true );

    public SavedInstanceFragment pushData( Bundle instanceState )
        if ( this.mInstanceBundle == null ) {
            this.mInstanceBundle = instanceState;
            this.mInstanceBundle.putAll( instanceState );
        return this;

    public Bundle popData()
        Bundle out = this.mInstanceBundle;
        this.mInstanceBundle = null;
        return out;

    public static final SavedInstanceFragment getInstance(FragmentManager fragmentManager )
        SavedInstanceFragment out = (SavedInstanceFragment) fragmentManager.findFragmentByTag( TAG );

        if ( out == null )
            out = new SavedInstanceFragment();
            fragmentManager.beginTransaction().add( out, TAG ).commit();
        return out;

Then on my main Activity I circumvent the saved instance cycle completely, and defer the respoinsibilty to my data Fragment. No need to use this on the Fragments themselves, sice their state is added to the Activity's state automatically):

protected void onSaveInstanceState(Bundle outState) {

    SavedInstanceFragment.getInstance( getFragmentManager() ).pushData( (Bundle) outState.clone() );
    outState.clear(); // We don't want a TransactionTooLargeException, so we handle things via the SavedInstanceFragment

What's left is simply to pop the saved instance:

protected void onCreate(Bundle savedInstanceState) {

protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState( SavedInstanceFragment.getInstance( getFragmentManager() ).popData() );

Full details:

Immediate exit of 'while' loop in C++

Yah Im pretty sure you just put


right where you want it to exit


    if (variable == 1)
    //do something

How/when to use ng-click to call a route?

You can use:

<a ng-href="#/about">About</a>

If you want some dynamic variable inside href you can do like this way:

<a ng-href="{{link + 123}}">Link to 123</a>

Where link is Angular scope variable.

Pandas DataFrame to List of Dictionaries

If you are interested in only selecting one column this will work.


The below will NOT work and produces a TypeError: unsupported type: . I believe this is because it is trying to convert a series to a dict and not a Data Frame to a dict.


I had a requirement to only select one column and convert it to a list of dicts with the column name as the key and was stuck on this for a bit so figured I'd share.

how to permit an array with strong parameters

when you want to permit multiple array fields you will have to list array fields at last while permitting ,as given -

params.require(:questions).permit(:question, :user_id, answers: [], selected_answer: [] )

(this works)

How do I write to a Python subprocess' stdin?

You can provide a file-like object to the stdin argument of

The documentation for the Popen object applies here.

To capture the output, you should instead use subprocess.check_output(), which takes similar arguments. From the documentation:

>>> subprocess.check_output(
...     "ls non_existent_file; exit 0",
...     stderr=subprocess.STDOUT,
...     shell=True)
'ls: non_existent_file: No such file or directory\n'

How do I tell if a variable has a numeric value in Perl?

I don't believe there is anything builtin to do it. For more than you ever wanted to see on the subject, see Perlmonks on Detecting Numeric

Saving numpy array to txt file row wise

If numpy >= 1.5, you can do:

# note that the filename is enclosed with double quotes,
# example "filename.txt"

numpy.savetxt("filename", a, newline=" ")


several 1D arrays with same length

a = numpy.array([1,2,3])
b = numpy.array([4,5,6])
numpy.savetxt(filename, (a,b), fmt="%d")

# gives:
# 1 2 3
# 4 5 6

several 1D arrays with variable length

a = numpy.array([1,2,3])
b = numpy.array([4,5])

with open(filename,"w") as f:
    f.write("\n".join(" ".join(map(str, x)) for x in (a,b)))

# gives:
# 1 2 3
# 4 5

Not equal to != and !== in PHP

$a !== $b TRUE if $a is not equal to $b, or they are not of the same type

Please Refer to

How does database indexing work?

Just a quick suggestion.. As indexing costs you additional writes and storage space, so if your application requires more insert/update operation, you might want to use tables without indexes, but if it requires more data retrieval operations, you should go for indexed table.

How to assert two list contain the same elements in Python?

Needs ensure library but you can compare list by:

ensure([1, 2]).contains_only([2, 1])

This will not raise assert exception. Documentation of thin is really thin so i would recommend to look at ensure's codes on github

Update Eclipse with Android development tools v. 23

This worked for me. I kept upgrading to version 23.02 (or 23.03 if presented) using a new install of ADT bundle, and migrating the your original workspace across and add the patches. This is the procedure for ADT Bundle only.

(Backup your workspace first)

1/ install latest adt bundle from google. (For some reason using Googles download page just goes around in a loop on Chrome!?!)

2/ download the patch from here:

3/ Apply the patch as per Googles (poorly described) instructions

...and copy over the following files:


Which means => Copy the file only of tools/hprof-conv
Which means => Copy the file only of tools/support/annotations.jar
Which means => Copy the directory and all contents for tools/proguard

3/ Point your old workspace to the new install on startup. (Projects will still come up with errors, don't worry)

4/ select Help-> Install new software, select update site, and select version 23.03 when prompted.

  • Check the update sites, and edit the one for google from https => http like this: Change to "http". This seems to make Eclipse Updater build a new update profile that avoided download errors. You might also get "unsigned" prompt warning prompts from Windoze but just "Allow Access" to prevent blocking.

5/ If you still get errors on references to "android.R", this is because you may not have the appropriate "platform build tools". Check the "Android SDK Manager" for which build tools you have like this: enter image description here Also check your "Android" build for the project to make sure you have the compatible Android API.

Version 23.02 should be downloaded, and your projects should now compile.

Google have abandoned all the UI trimmings for Eclipse ADT (ie you'll see the Juno splash). I thought this would be a problem but it seems ok. I think it shows how desperate Google were to get the fix out. Given that Android studio is not far away Google don't want invest any more time into ADT. I suppose this is what you get with "free" software. Hopefully the adults are back in charge now, and Google Studio won't be such a disaster.

What is "overhead"?

A concrete example of overhead is the difference between a "local" procedure call and a "remote" procedure call.

For example, with classic RPC (and many other remote frameworks, like EJB), a function or method call looks the same to a coder whether its a local, in memory call, or a distributed, network call.

For example:

service.function(param1, param2);

Is that a normal method, or a remote method? From what you see here you can't tell.

But you can imagine that the difference in execution times between the two calls are dramatic.

So, while the core implementation will "cost the same", the "overhead" involved is quite different.

Generate ER Diagram from existing MySQL database, created for CakePHP

Try MySQL Workbench. It packs in very nice data modeling tools. Check out their screenshots for EER diagrams (Enhanced Entity Relationships, which are a notch up ER diagrams).

This isn't CakePHP specific, but you can modify the options so that the foreign keys and join tables follow the conventions that CakePHP uses. This would simplify your data modeling process once you've put the rules in place.

What is the best way to clone/deep copy a .NET generic Dictionary<string, T>?

For .NET 2.0 you could implement a class which inherits from Dictionary and implements ICloneable.

public class CloneableDictionary<TKey, TValue> : Dictionary<TKey, TValue> where TValue : ICloneable
    public IDictionary<TKey, TValue> Clone()
        CloneableDictionary<TKey, TValue> clone = new CloneableDictionary<TKey, TValue>();

        foreach (KeyValuePair<TKey, TValue> pair in this)
            clone.Add(pair.Key, (TValue)pair.Value.Clone());

        return clone;

You can then clone the dictionary simply by calling the Clone method. Of course this implementation requires that the value type of the dictionary implements ICloneable, but otherwise a generic implementation isn't practical at all.

Tooltips with Twitter Bootstrap

Add this into your header

    $(function() {
        var tooltips = $( "[title]" ).tooltip();
        $(document)(function() {
            tooltips.tooltip( "open" );

Then just add the attribute title="your tooltip" to any element

Check if DataRow exists by column name in c#?

if (drMyRow.Table.Columns["ColNameToCheck"] != null)
else { return; }

Although the DataRow does not have a Columns property, it does have a Table that the column can be checked for.

Is div inside list allowed?

If you look at xhtml1-strict.dtd, you'll see

<!ELEMENT li %Flow;>
<!ENTITY % Flow "(#PCDATA | %block; | form | %inline; | %misc;)*">
<!ENTITY % block
     "p | %heading; | div | %lists; | %blocktext; | fieldset | table">

Thus div, p etc. can be inside li (according to XHTML 1.0 Strict DTD from

html/css buttons that scroll down to different div sections on a webpage

try this:

<input type="button" onClick="document.getElementById('middle').scrollIntoView();" />

How to handle Uncaught (in promise) DOMException: The play() request was interrupted by a call to pause()

Try using a callback like this with the catch block.

document.getElementById("audio").play().catch(function() {
    // do something

Oracle: how to add minutes to a timestamp?

SET DATE_FIELD = CURRENT_TIMESTAMP + interval '48' minute 
WHERE (...)

Where interval is one of

  • YEAR
  • DAY
  • HOUR

Unable to verify leaf signature

For Create React App (where this error occurs too and this question is the #1 Google result), you are probably using HTTPS=true npm start and a proxy (in package.json) which goes to some HTTPS API which itself is self-signed, when in development.

If that's the case, consider changing proxy like this:

"proxy": {
  "/api": {
    "target": "https://localhost:5001",
    "secure": false

secure decides whether the WebPack proxy checks the certificate chain or not and disabling that ensures the API self-signed certificate is not verified so that you get your data.

Disable automatic sorting on the first column when using jQuery DataTables

If any of other solution doesn't fix it, try to override the styles to hide the sort togglers:

.sorting_asc:after, .sorting_desc:after {
  content: "";

How to use Git?

Have a look at git for designers for great one page article/high level intro to the topic. (That link is broken: Here is a link to another Git for Designers )

I would start at, there are documents and great video presentations for non-software-developer/cs users. Git for beginners have some basic stuff.

javax.crypto.IllegalBlockSizeException : Input length must be multiple of 16 when decrypting with padded cipher

A few comments:

import sun.misc.*; Don't do this. It is non-standard and not guaranteed to be the same between implementations. There are other libraries with Base64 conversion available.

byte[] encVal = c.doFinal(Data.getBytes()); You are relying on the default character encoding here. Always specify what character encoding you are using: byte[] encVal = c.doFinal(Data.getBytes("UTF-8")); Defaults might be different in different places.

As @thegrinner pointed out, you need to explicitly check the length of your byte arrays. If there is a discrepancy, then compare them byte by byte to see where the difference is creeping in.

Can I avoid the native fullscreen video player with HTML5 on iPhone or android?

I don't know about android, but Safari on the iPhone or iPod touch will play all videos full screen because of the small screen size. On the iPad it will play the video on the page but allow the user to make it full screen.

multiple conditions for JavaScript .includes() method

How about ['hello', 'hi', 'howdy'].includes(str)?

How to initailize byte array of 100 bytes in java with all 0's

Actually the default value of byte is 0.

Python Threading String Arguments

from threading import Thread
from time import sleep
def run(name):
    for x in range(10):
        print("helo "+name)
def run1():
    for x in range(10):

Use xml.etree.ElementTree to print nicely formatted xml files

You can use the function toprettyxml() from xml.dom.minidom in order to do that:

def prettify(elem):
    """Return a pretty-printed XML string for the Element.
    rough_string = ElementTree.tostring(elem, 'utf-8')
    reparsed = minidom.parseString(rough_string)
    return reparsed.toprettyxml(indent="\t")

The idea is to print your Element in a string, parse it using minidom and convert it again in XML using the toprettyxml function.


How to install PHP mbstring on CentOS 6.2

If none of the above help you out, and you have the option, try obtaining one of the rpm files eg:


then using rpm, install it ignoring the depenecies like so:

rpm -i --nodeps php-mbstring-5.4.45-2.el6.remi.x86_64.rpm

Hope that helps out.

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

It's an array of the parameters/arguments (hence args) that you send to the program. For example ping -t -4

These arguments are passed to the program as an array of strings.

string[] args // Array of Strings containing arguments.

"for" vs "each" in Ruby

Your first example,

@collection.each do |item|
  # do whatever

is more idiomatic. While Ruby supports looping constructs like for and while, the block syntax is generally preferred.

Another subtle difference is that any variable you declare within a for loop will be available outside the loop, whereas those within an iterator block are effectively private.

Paste MS Excel data to SQL Server

The simplest way is to create a computed column in XLS that would generate the syntax of the insert statement. Then copy these insert into a text file and then execute on the SQL. The other alternatives are to buy database connectivity add-on's for Excel and write VBA code to accomplish the same.

SSL handshake alert: unrecognized_name error since upgrade to Java 1.7.0

Just to add a solution here. This might help for LAMP users

Options +FollowSymLinks -SymLinksIfOwnerMatch

The above mentioned line in the virtual host configuration was the culprit.

Virtual Host Configuration when error

<VirtualHost *:80>
    DocumentRoot /var/www/html/load/web
    <Directory "/var/www/html/load/web">
        Options +FollowSymLinks -SymLinksIfOwnerMatch
        AllowOverride All
        Require all granted
        Order Allow,Deny
        Allow from All
     RewriteEngine on
     RewriteCond %{SERVER_PORT} !^443$
     RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R=301,L]

Working Configuration

<VirtualHost *:80>
    DocumentRoot /var/www/html/load/web

   <Directory "/var/www/html/load/web">

        AllowOverride All

        Options All

        Order Allow,Deny

        Allow from All


    # To allow authorization header
    RewriteEngine On
    RewriteCond %{HTTP:Authorization} ^(.*)
    RewriteRule .* - [e=HTTP_AUTHORIZATION:%1]

   # RewriteCond %{SERVER_PORT} !^443$
   # RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R=301,L]


VBA ADODB excel - read data from Recordset

I am surprised that the connection string works for you, because it is missing a semi-colon. Set is only used with objects, so you would not say Set strNaam.

Set cn = CreateObject("ADODB.Connection")
With cn
 .Provider = "Microsoft.Jet.OLEDB.4.0"
  .ConnectionString = "Data Source=D:\test.xls " & _
  ";Extended Properties=""Excel 8.0;HDR=Yes;"""
End With
strQuery = "SELECT * FROM [Sheet1$E36:E38]"
Set rs = cn.Execute(strQuery)
Do While Not rs.EOF
  For i = 0 To rs.Fields.Count - 1
    Debug.Print rs.Fields(i).Name, rs.Fields(i).Value
    strNaam = rs.Fields(0).Value

There are other ways, depending on what you want to do, such as GetString (GetString Method Description).

Unable to create a constant value of type Only primitive types or enumeration types are supported in this context

It's worth adding, since the OP's code sample doesn't provide enough context to prove otherwise, but I received this error as well on the following code:

public RetailSale GetByRefersToRetailSaleId(Int32 refersToRetailSaleId)
    return GetQueryable()
        .FirstOrDefault(x => x.RefersToRetailSaleId.Equals(refersToRetailSaleId));

Apparently, I cannot use Int32.Equals in this context to compare an Int32 with a primitive int; I had to (safely) change to this:

public RetailSale GetByRefersToRetailSaleId(Int32 refersToRetailSaleId)
    return GetQueryable()
      .FirstOrDefault(x => x.RefersToRetailSaleId == refersToRetailSaleId);

Detecting installed programs via registry

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Compatibility Assistant\Persisted

Flutter Circle Design

I would use a to be able to freely position widgets.

To create circles

  new BoxDecoration(
    color: effectiveBackgroundColor,
    image: backgroundImage != null
      ? new DecorationImage(image: backgroundImage, fit: BoxFit.cover)
      : null,

and to position the white dots.

How to restore default perspective settings in Eclipse IDE

There is no keyboard shortcut for restoring the perspective directly AFAIK. To open the Window menu (where Reset Perspective resides), try Alt-W. If that does not work, I guess your Eclipse has hung for some reason. Another shortcut you might want to try is F10 (should open the main menu).

What does "both" mean in <div style="clear:both">

Clear:both gives you that space between them.

For example your code:

  <div style="float:left">Hello</div>
  <div style="float:right">Howdy dere pardner</div>

Will currently display as :

Hello  ...................   Howdy dere pardner

If you add the following to above snippet,

  <div style="clear:both"></div>

In between them it will display as:

Hello ................ 
                       Howdy dere pardner

giving you that space between hello and Howdy dere pardner.

Js fiiddle

javascript set cookie with expire time

Here's a function I wrote another application. Feel free to reuse:

function writeCookie (key, value, days) {
    var date = new Date();

    // Default at 365 days.
    days = days || 365;

    // Get unix milliseconds at current time plus number of days
    date.setTime(+ date + (days * 86400000)); //24 * 60 * 60 * 1000

    window.document.cookie = key + "=" + value + "; expires=" + date.toGMTString() + "; path=/";

    return value;

How to pass an array to a function in VBA?

This seems unnecessary, but VBA is a strange place. If you declare an array variable, then set it using Array() then pass the variable into your function, VBA will be happy.

Sub test()
    Dim fString As String
    Dim arr() As Variant
    arr = Array("foo", "bar")
    fString = processArr(arr)
End Sub

Also your function processArr() could be written as:

Function processArr(arr() As Variant) As String
    processArr = Replace(Join(arr()), " ", "")
End Function

If you are into the whole brevity thing.

When to use EntityManager.find() vs EntityManager.getReference() with JPA

This makes me wonder, when is it advisable to use the EntityManager.getReference() method instead of the EntityManager.find() method?

EntityManager.getReference() is really an error prone method and there is really very few cases where a client code needs to use it.
Personally, I never needed to use it.

EntityManager.getReference() and EntityManager.find() : no difference in terms of overhead

I disagree with the accepted answer and particularly :

If i call find method, JPA provider, behind the scenes, will call



If i call getReference method, JPA provider, behind the scenes, will call


It is not the behavior that I get with Hibernate 5 and the javadoc of getReference() doesn't say such a thing :

Get an instance, whose state may be lazily fetched. If the requested instance does not exist in the database, the EntityNotFoundException is thrown when the instance state is first accessed. (The persistence provider runtime is permitted to throw the EntityNotFoundException when getReference is called.) The application should not expect that the instance state will be available upon detachment, unless it was accessed by the application while the entity manager was open.

EntityManager.getReference() spares a query to retrieve the entity in two cases :

1) if the entity is stored in the Persistence context, that is the first level cache.
And this behavior is not specific to EntityManager.getReference(), EntityManager.find() will also spare a query to retrieve the entity if the entity is stored in the Persistence context.

You can check the first point with any example.
You can also rely on the actual Hibernate implementation.
Indeed, EntityManager.getReference() relies on the createProxyIfNecessary() method of the org.hibernate.event.internal.DefaultLoadEventListener class to load the entity.
Here is its implementation :

private Object createProxyIfNecessary(
        final LoadEvent event,
        final EntityPersister persister,
        final EntityKey keyToLoad,
        final LoadEventListener.LoadType options,
        final PersistenceContext persistenceContext) {
    Object existing = persistenceContext.getEntity( keyToLoad );
    if ( existing != null ) {
        // return existing object or initialized proxy (unless deleted)
        if ( traceEnabled ) {
            LOG.trace( "Entity found in session cache" );
        if ( options.isCheckDeleted() ) {
            EntityEntry entry = persistenceContext.getEntry( existing );
            Status status = entry.getStatus();
            if ( status == Status.DELETED || status == Status.GONE ) {
                return null;
        return existing;
    if ( traceEnabled ) {
        LOG.trace( "Creating new proxy for entity" );
    // return new uninitialized proxy
    Object proxy = persister.createProxy( event.getEntityId(), event.getSession() );
    persistenceContext.getBatchFetchQueue().addBatchLoadableEntityKey( keyToLoad );
    persistenceContext.addProxy( keyToLoad, proxy );
    return proxy;

The interesting part is :

Object existing = persistenceContext.getEntity( keyToLoad );

2) If we don't effectively manipulate the entity, echoing to the lazily fetched of the javadoc.
Indeed, to ensure the effective loading of the entity, invoking a method on it is required.
So the gain would be related to a scenario where we want to load a entity without having the need to use it ? In the frame of applications, this need is really uncommon and in addition the getReference() behavior is also very misleading if you read the next part.

Why favor EntityManager.find() over EntityManager.getReference()

In terms of overhead, getReference() is not better than find() as discussed in the previous point.
So why use the one or the other ?

Invoking getReference() may return a lazily fetched entity.
Here, the lazy fetching doesn't refer to relationships of the entity but the entity itself.
It means that if we invoke getReference() and then the Persistence context is closed, the entity may be never loaded and so the result is really unpredictable. For example if the proxy object is serialized, you could get a null reference as serialized result or if a method is invoked on the proxy object, an exception such as LazyInitializationException is thrown.

It means that the throw of EntityNotFoundException that is the main reason to use getReference() to handle an instance that does not exist in the database as an error situation may be never performed while the entity is not existing.

EntityManager.find() doesn't have the ambition of throwing EntityNotFoundException if the entity is not found. Its behavior is both simple and clear. You will never have surprise as it returns always a loaded entity or null (if the entity is not found) but never an entity under the shape of a proxy that may not be effectively loaded.
So EntityManager.find() should be favored in the very most of cases.

Get all child elements

Another veneration of find_elements_by_xpath(".//*") is:

from import By

find_elements(By.XPATH, ".//*")

Check if cookie exists else set cookie to Expire in 10 days

if (/(^|;)\s*visited=/.test(document.cookie)) {
    alert("Hello again!");
} else {
    document.cookie = "visited=true; max-age=" + 60 * 60 * 24 * 10; // 60 seconds to a minute, 60 minutes to an hour, 24 hours to a day, and 10 days.
    alert("This is your first time!");

is one way to do it. Note that document.cookie is a magic property, so you don't have to worry about overwriting anything, either.

There are also more convenient libraries to work with cookies, and if you don’t need the information you’re storing sent to the server on every request, HTML5’s localStorage and friends are convenient and useful.

Checkout old commit and make it a new commit

eloone did it file by file with

git checkout <commit-hash> <filename>

but you could checkout all files more easily by doing

git checkout <commit-hash> .

How to get the path of running java program

Try this code:

final File f = new File(MyClass.class.getProtectionDomain().getCodeSource().getLocation().getPath());

replace 'MyClass' with your class containing the main method.

Alternatively you can also use


Above mentioned System property provides

Path used to find directories and JAR archives containing class files. Elements of the class path are separated by a platform-specific character specified in the path.separator property.

REST API error return good practices

I know this is extremely late to the party, but now, in year 2013, we have a few media types to cover error handling in a common distributed (RESTful) fashion. See "vnd.error", application/vnd.error+json ( and "Problem Details for HTTP APIs", application/problem+json (

Unzip All Files In A Directory

Unzip all .zip files and store the content in a new folder with the same name and in the same folder as the .zip file:

find -name '*.zip' -exec sh -c 'unzip -d "${1%.*}" "$1"' _ {} \;

This is an extension of @phatmanace's answer and addresses @RishabhAgrahari's comment:

This will extract all the zip files in current directory, what if I want the zip files (present in subfolders) to be extracted in the respective subfolders ?

Environment.GetFolderPath(...CommonApplicationData) is still returning "C:\Documents and Settings\" on Vista

I was looking for a listing of macOS but found nothing, maybe this helps someone.

Output on macOS Catalina (10.15.7) using net5.0

# SpecialFolders (Only with value)
SpecialFolder.ApplicationData: /Users/$USER/.config
SpecialFolder.CommonApplicationData: /usr/share
SpecialFolder.Desktop: /Users/$USER/Desktop
SpecialFolder.DesktopDirectory: /Users/$USER/Desktop
SpecialFolder.Favorites: /Users/$USER/Library/Favorites
SpecialFolder.Fonts: /Users/$USER/Library/Fonts
SpecialFolder.InternetCache: /Users/$USER/Library/Caches
SpecialFolder.LocalApplicationData: /Users/$USER/.local/share
SpecialFolder.MyDocuments: /Users/$USER
SpecialFolder.MyMusic: /Users/$USER/Music
SpecialFolder.MyPictures: /Users/$USER/Pictures
SpecialFolder.ProgramFiles: /Applications
SpecialFolder.System: /System
SpecialFolder.UserProfile: /Users/$USER

# SpecialFolders (All)
SpecialFolder.ApplicationData: /Users/$USER/.config
SpecialFolder.CommonApplicationData: /usr/share
SpecialFolder.Desktop: /Users/$USER/Desktop
SpecialFolder.DesktopDirectory: /Users/$USER/Desktop
SpecialFolder.Favorites: /Users/$USER/Library/Favorites
SpecialFolder.Fonts: /Users/$USER/Library/Fonts
SpecialFolder.InternetCache: /Users/$USER/Library/Caches
SpecialFolder.LocalApplicationData: /Users/$USER/.local/share
SpecialFolder.MyDocuments: /Users/$USER
SpecialFolder.MyMusic: /Users/$USER/Music
SpecialFolder.MyPictures: /Users/$USER/Pictures
SpecialFolder.ProgramFiles: /Applications
SpecialFolder.System: /System
SpecialFolder.UserProfile: /Users/$USER

I have replaced my username with $USER.

Code Snippet from pogosama.

foreach(Environment.SpecialFolder f in Enum.GetValues(typeof(Environment.SpecialFolder)))
    string commonAppData = Environment.GetFolderPath(f);
    Console.WriteLine("{0}: {1}", f, commonAppData);

CSS: center element within a <div> element

Assign text-align: center; to the parent and display: inline-block; to the div.

Pass an array of integers to ASP.NET Web API?

I just added the Query key (Refit lib) in the property for the request.


public class ExampleRequest
        [FromQuery(Name = "name")]
        public string Name { get; set; }               
        public List<string> Categories { get; set; }

How can I show/hide component with JSF?

One obvious solution would be to use javascript (which is not JSF). To implement this by JSF you should use AJAX. In this example, I use a radio button group to show and hide two set of components. In the back bean, I define a boolean switch.

private boolean switchComponents;

public boolean isSwitchComponents() {
    return switchComponents;

public void setSwitchComponents(boolean switchComponents) {
    this.switchComponents = switchComponents;

When the switch is true, one set of components will be shown and when it is false the other set will be shown.

 <h:selectOneRadio value="#{backbean.switchValue}">
   <f:selectItem itemLabel="showComponentSetOne" itemValue='true'/>
   <f:selectItem itemLabel="showComponentSetTwo" itemValue='false'/>
   <f:ajax event="change" execute="@this" render="componentsRoot"/>

<H:panelGroup id="componentsRoot">
     <h:panelGroup rendered="#{backbean.switchValue}">
       <!--switchValue to be shown on switch value == true-->

   <h:panelGroup rendered="#{!backbean.switchValue}">
      <!--switchValue to be shown on switch value == false-->

Note: on the ajax event we render components root. because components which are not rendered in the first place can't be re-rendered on the ajax event.

Also, note that if the "componentsRoot" and radio buttons are under different component hierarchy. you should reference it from the root (form root).

Why is System.Web.Mvc not listed in Add References?

I solved this problem by searching "mvc". The System.Web.Mvc appeared in search results, despite it is not contained in the list.

How to check if a .txt file is in ASCII or UTF-8 format in Windows environment?

Open it in a hex editor and make sure that the first three bytes are a UTF8 BOM (EF BB BF)

Eclipse: Set maximum line length for auto formatting?

Take a look of following image:

Java->Code style->Formatter-> Edit

enter image description here

Android: I lost my android key store, what should I do?

As everyone has said, you definitely need the key. There's no workaround for that. However, you might be surprised at how good the data recovery software can be, and how long the key may linger on your systems -- it's a tiny, tiny file, after all, and may not yet be overwritten. I was pleasantly surprised on both counts.

I develop on an OSX machine. I unintentionally deleted my app key around 6 weeks ago. When I tried to update, I realized my schoolboy error. I tried all the recovery tools I could find for OSX, but none could find the file -- not because it wasn't there, but because these tools are optimized to find the sorts of files the majority of users want back (photos, Word docs, etc.). They're definitely not looking for a 1KB file with an unusual file signature.

Now this next part is going to sound like a plug, but it isn't -- I don't have any connection to the developers:

The only recover tool I found that worked was one called Data Rescue by Prosoft Engineering (which I believe works for other files systems as well -- not just HFS+). It worked because it has a feature which allows you to train it to look for any file type -- even an Android key. You give it several examples. (I generated a few keys, filling in the data fields in as like manner as possible to the original). You then tell it to "deep search". If you're lucky, you'll get your key back in the "custom files" section.

For me, it was a life saver.

It's $100 to purchase, so it's not cheap, but it's worth it if you've got a mass of users and no further means of feeding them updates.

I believe they allow you 1 free file recovery in demo mode, but, unfortunately, in my case, I had several keys and could not tell which one was the one I needed without recovering them all (file names are not preserved on HFS+).

Try it first in demo mode, you may get lucky and be able to recover the key without paying anything.

May this message help someone. It's a sickening feeling, I know, but there may be relief.

Proper usage of Java -D command-line parameters

I suspect the problem is that you've put the "-D" after the -jar. Try this:

java -Dtest="true" -jar myApplication.jar

From the command line help:

java [-options] -jar jarfile [args...]

In other words, the way you've got it at the moment will treat -Dtest="true" as one of the arguments to pass to main instead of as a JVM argument.

(You should probably also drop the quotes, but it may well work anyway - it probably depends on your shell.)

Remove part of string after "."

If the string should be of fixed length, then substr from base R can be used. But, we can get the position of the . with regexpr and use that in substr

substr(a, 1, regexpr("\\.", a)-1)
#[1] "NM_020506"    "NM_020519"    "NM_001030297" "NM_010281"    "NM_011419"    "NM_053155"   

How to set tint for an image view programmatically in android?

I found that we can use color selector for tint attr:



    android:tint="@color/section_arrowup_color" />


<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="">
    <item android:color="@android:color/white" android:state_enabled="true"/>
    <item android:color="@android:color/black" android:state_enabled="false"/>
    <item android:color="@android:color/white"/>

Predicate Delegates in C#

Simply -> they provide True/False values based on condition mostly used for querying. mostly used with delegates

consider example of list

List<Program> blabla= new List<Program>();
        blabla.Add(new Program("shubham", 1));
        blabla.Add(new Program("google", 3));
        blabla.Add(new Program("world",5));
        blabla.Add(new Program("hello", 5));
        blabla.Add(new Program("bye", 2));

contains names and ages. Now say we want to find names on condition So I Will use,

    Predicate<Program> test = delegate (Program p) { return p.age > 3; };
        List<Program> matches = blabla.FindAll(test);
        Action<Program> print = Console.WriteLine;

tried to Keep it Simple!

How to hide columns in HTML table?

You can also hide a column using the col element

To hide the second column in a table:

  <col />
  <col style="visibility:collapse"/>

Known issues: this won't work in Google Chrome. Please vote for the bug at

Bash foreach loop

If they all have the same extension (for example .jpg), you can use this:

for picture in  *.jpg ; do
    echo "the next file is $picture"

(This solution also works if the filename has spaces)

How to Execute a Python File in Notepad ++?

None of the previously proposed solutions worked for me. Slight modification needed.

After hitting F5 in Notepad++, type:

cmd /k "C:\Python27\python.exe $(FULL_CURRENT_PATH)"

The command prompt stays open so you can see the output of your script.

Match whitespace but not newlines

A variation on Greg’s answer that includes carriage returns too:


This regex is safer than /[^\S\n]/ with no \r. My reasoning is that Windows uses \r\n for newlines, and Mac OS 9 used \r. You’re unlikely to find \r without \n nowadays, but if you do find it, it couldn’t mean anything but a newline. Thus, since \r can mean a newline, we should exclude it too.

How to hide form code from view code/inspect element browser?

While I don't think there is a way to fully do this you can take a few measures to stop almost everyone from viewing the HTML.

You can first of all try and stop the inspect menu by doing the following:

I would also suggest using the method that Jonas gave of using his javascript and putting what you don't want people to see in a div with id="element-to-hide" and his given js script to furthermore stop people from inspecting.

I'm pretty sure that it's quite hard to get past that. But then someone can just type view-source

This will basically encrypt your HTML so if you view the source using the method I showed above you will just get encrypted HTML(that is also extremely difficult to unencrypt if you used the extended security option). But you can view the unencrypted HTML through inspecting but we have already blocked that(to a very reasonable extent)

Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

Difference between each annotation are :

¦                                       Feature                            ¦   Junit 4    ¦   Junit 5   ¦
¦ Execute before all test methods of the class are executed.               ¦ @BeforeClass ¦ @BeforeAll  ¦
¦ Used with static method.                                                 ¦              ¦             ¦
¦ For example, This method could contain some initialization code          ¦              ¦             ¦
¦ Execute after all test methods in the current class.                     ¦ @AfterClass  ¦ @AfterAll   ¦
¦ Used with static method.                                                 ¦              ¦             ¦
¦ For example, This method could contain some cleanup code.                ¦              ¦             ¦
¦ Execute before each test method.                                         ¦ @Before      ¦ @BeforeEach ¦
¦ Used with non-static method.                                             ¦              ¦             ¦
¦ For example, to reinitialize some class attributes used by the methods.  ¦              ¦             ¦
¦ Execute after each test method.                                          ¦ @After       ¦ @AfterEach  ¦
¦ Used with non-static method.                                             ¦              ¦             ¦
¦ For example, to roll back database modifications.                        ¦              ¦             ¦

Most of annotations in both versions are same, but few differs.


Order of Execution.

Dashed box -> optional annotation.

enter image description here

Problem in running .net framework 4.0 website on iis 7.0

Step 1: Open IIS and click the server name Step 2. Double click “ISAPI and CGI Restrictions” Step 3. Right click ASP.NET v4.0.30319 and select “allow”

After Stopping and Starting the World Wide Web Publishing Service

1.Go to Start > All Programs > Administrative Tools > Services. 2.In the services list, right-click World Wide Web Publishing Service, and then click Stop (to stop the service), Start (to start it after it has been stopped), or Restart (to restart the service when it is running).


How to undo last commit

Warning: Don't do this if you've already pushed

You want to do:

git reset HEAD~

If you don't want the changes and blow everything away:

git reset --hard HEAD~

Send email with PHP from html form on submit with the same script

You can also use mandrill app to send the mail in php. You will get the API from where you can find the complete details about emails sended and other details.

Python Git Module experiences?

I thought I would answer my own question, since I'm taking a different path than suggested in the answers. Nonetheless, thanks to those who answered.

First, a brief synopsis of my experiences with GitPython, PyGit, and Dulwich:

  • GitPython: After downloading, I got this imported and the appropriate object initialized. However, trying to do what was suggested in the tutorial led to errors. Lacking more documentation, I turned elsewhere.
  • PyGit: This would not even import, and I could find no documentation.
  • Dulwich: Seems to be the most promising (at least for what I wanted and saw). I made some progress with it, more than with GitPython, since its egg comes with Python source. However, after a while, I decided it may just be easier to try what I did.

Also, StGit looks interesting, but I would need the functionality extracted into a separate module and do not want wait for that to happen right now.

In (much) less time than I spent trying to get the three modules above working, I managed to get git commands working via the subprocess module, e.g.

def gitAdd(fileName, repoDir):
    cmd = ['git', 'add', fileName]
    p = subprocess.Popen(cmd, cwd=repoDir)

gitAdd('exampleFile.txt', '/usr/local/example_git_repo_dir')

This isn't fully incorporated into my program yet, but I'm not anticipating a problem, except maybe speed (since I'll be processing hundreds or even thousands of files at times).

Maybe I just didn't have the patience to get things going with Dulwich or GitPython. That said, I'm hopeful the modules will get more development and be more useful soon.

Using if elif fi in shell scripts

Josh Lee's answer works, but you can use the "&&" operator for better readability like this:

echo "You have provided the following arguments $arg1 $arg2 $arg3"
if [ "$arg1" = "$arg2" ] && [ "$arg1" != "$arg3" ]
    echo "Two of the provided args are equal."
    exit 3
elif [ $arg1 = $arg2 ] && [ $arg1 = $arg3 ]
    echo "All of the specified args are equal"
    exit 0
    echo "All of the specified args are different"
    exit 4 

Role/Purpose of ContextLoaderListener in Spring?

enter image description hereThis Bootstrap listener is to start up and shut down Spring's root WebApplicationContext. As a web application can have multiple dispatcher servlet and each having its own application context containing controllers, view resolver, handler mappings etc But you might want to have service beans, DAO beans in root application context and want to use in all child application context(application context created by dispatcher servlets).

2nd use of this listener is when you want to use spring security.

Convert Pandas Column to DateTime

Use the pandas to_datetime function to parse the column as DateTime. Also, by using infer_datetime_format=True, it will automatically detect the format and convert the mentioned column to DateTime.

import pandas as pd
raw_data['Mycol'] =  pd.to_datetime(raw_data['Mycol'], infer_datetime_format=True)

Lost httpd.conf file located apache

See for discussion of where you might find Apache httpd configuration files on various platforms, since this can vary from release to release and platform to platform. The most common answer, however, is either /etc/apache/conf or /etc/httpd/conf

Generically, you can determine the answer by running the command:

httpd -V

(That's a capital V). Or, on systems where httpd is renamed, perhaps apache2ctl -V

This will return various details about how httpd is built and configured, including the default location of the main configuration file.

One of the lines of output should look like:

-D SERVER_CONFIG_FILE="conf/httpd.conf"

which, combined with the line:

-D HTTPD_ROOT="/etc/httpd"

will give you a full path to the default location of the configuration file

One-liner if statements, how to convert this if-else-statement

All you'd need in your case is:

return expression;

The reason why is that the expression itself evaluates to a boolean value of true or false, so it's redundant to have an if block (or even a ?: operator).

Get current NSDate in timestamp format

Can also use


for timestamp in seconds.

How do I get the path of a process in Unix / Linux

You can find the exe easily by these ways, just try it yourself.

  • ll /proc/<PID>/exe
  • pwdx <PID>
  • lsof -p <PID> | grep cwd

Converting HTML to Excel?

Change the content type to ms-excel in the html and browser shall open the html in the Excel as xls. If you want control over the transformation of HTML to excel use POI libraries to do so.

Why do we need the "finally" clause in Python?

As explained in the documentation, the finally clause is intended to define clean-up actions that must be executed under all circumstances.

If finally is present, it specifies a ‘cleanup’ handler. The try clause is executed, including any except and else clauses. If an exception occurs in any of the clauses and is not handled, the exception is temporarily saved. The finally clause is executed. If there is a saved exception it is re-raised at the end of the finally clause.

An example:

>>> def divide(x, y):
...     try:
...         result = x / y
...     except ZeroDivisionError:
...         print("division by zero!")
...     else:
...         print("result is", result)
...     finally:
...         print("executing finally clause")
>>> divide(2, 1)
result is 2.0
executing finally clause
>>> divide(2, 0)
division by zero!
executing finally clause
>>> divide("2", "1")
executing finally clause
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in divide
TypeError: unsupported operand type(s) for /: 'str' and 'str'

As you can see, the finally clause is executed in any event. The TypeError raised by dividing two strings is not handled by the except clause and therefore re-raised after the finally clause has been executed.

In real world applications, the finally clause is useful for releasing external resources (such as files or network connections), regardless of whether the use of the resource was successful.