Programs & Examples On #Optional variables

How to install OpenSSL in windows 10?

If you have chocolatey installed you can install openssl via a single command i.e.

choco install openssl

What is the default scope of a method in Java?

Anything defined as package private can be accessed by the class itself, other classes within the same package, but not outside of the package, and not by sub-classes.

See this page for a handy table of access level modifiers...

How do you extract classes' source code from a dll file?

 public async void Decompile(string DllName)
     string destinationfilename = "";

     if (System.IO.File.Exists(DllName))
         destinationfilename = (@helperRoot + System.IO.Path.GetFileName(medRuleBook.Schemapath)).ToLower();
         if (System.IO.File.Exists(destinationfilename))

         System.IO.File.Copy(DllName, @destinationfilename);
        // use dll-> XSD
     var returnVal = await DoProcess(
            @helperRoot + "xsd.exe", "\"" + @destinationfilename + "\"");

     destinationfilename = destinationfilename.Replace(".dll", ".xsd");

     if (System.IO.File.Exists(@destinationfilename))
          // now use XSD
          returnVal =
            await DoProcess(
              @helperRoot + "xsd.exe", "/c /namespace:RuleBook /language:CS " + "\"" + @destinationfilename + "\"");

            if (System.IO.File.Exists(@destinationfilename.Replace(".xsd", ".cs")))
                string getXSD = System.IO.File.ReadAllText(@destinationfilename.Replace(".xsd", ".cs"));

declaring a priority_queue in c++ with a custom comparator

You have to define the compare first. There are 3 ways to do that:

  1. use class
  2. use struct (which is same as class)
  3. use lambda function.

It's easy to use class/struct because easy to declare just write this line of code above your executing code

struct compare{
  bool operator()(Node& a,Node& b) // overloading both operators 
      return a.w < b.w: // if you want increasing order;(i.e increasing for minPQ)
      return a.w > b.w // if you want reverse of default order;(i.e decreasing for minPQ)

Calling code:

priority_queue<Node,vector<Node>,compare> pq;

How to render an ASP.NET MVC view as a string?

Quick tip

For a strongly typed Model just add it to the ViewData.Model property before passing to RenderViewToString. e.g

this.ViewData.Model = new OrderResultEmailViewModel(order);
string myString = RenderViewToString(this.ControllerContext, "~/Views/Order/OrderResultEmail.aspx", "~/Views/Shared/Site.Master", this.ViewData, this.TempData);

Sublime Text 2 Code Formatting

I can't speak for the 2nd or 3rd, but if you install Node first, Sublime-HTMLPrettify works pretty well. You have to setup your own key shortcut once it is installed. One thing I noticed on Windows, you may need to edit your path for Node in the %PATH% variable if it is already long (I think the limit is 1024 for the %PATH% variable, and anything after that is ignored.)

There is a Windows bug, but in the issues there is a fix for it. You'll need to edit the file -

6 digits regular expression



\b    # word boundary - start
\d    # any digits between 0 to 9 (inclusive)
{1,6} # length - min 1 digit or max 6 digits
\b    # word boundary - end

How can I test that a variable is more than eight characters in PowerShell?

Use the length property of the [String] type:

if ($dbUserName.length -gt 8) {
    Write-Output "Please enter more than 8 characters."
    $dbUserName = Read-Host "Re-enter database username"

Please note that you have to use -gt instead of > in your if condition. PowerShell uses the following comparison operators to compare values and test conditions:

  • -eq = equals
  • -ne = not equals
  • -lt = less than
  • -gt = greater than
  • -le = less than or equals
  • -ge = greater than or equals

How to write a Unit Test?

  1. Define the expected and desired output for a normal case, with correct input.

  2. Now, implement the test by declaring a class, name it anything (Usually something like TestAddingModule), and add the testAdd method to it (i.e. like the one below) :

    • Write a method, and above it add the @Test annotation.
    • In the method, run your binary sum and assertEquals(expectedVal,calculatedVal).
    • Test your method by running it (in Eclipse, right click, select Run as ? JUnit test).

      //for normal addition 
      public void testAdd1Plus1() 
          int x  = 1 ; int y = 1;
          assertEquals(2, myClass.add(x,y));
  3. Add other cases as desired.

    • Test that your binary sum does not throw a unexpected exception if there is an integer overflow.
    • Test that your method handles Null inputs gracefully (example below).

      //if you are using 0 as default for null, make sure your class works in that case.
      public void testAdd1Plus1() 
          int y = 1;
          assertEquals(0, myClass.add(null,y));

Two's Complement in Python

in case someone needs the inverse direction too:

def num_to_bin(num, wordsize):
    if num < 0:
        num = 2**wordsize+num
    base = bin(num)[2:]
    padding_size = wordsize - len(base)
    return '0' * padding_size + base

for i in range(7, -9, -1):
    print num_to_bin(i, 4)

should output this: 0111 0110 0101 0100 0011 0010 0001 0000 1111 1110 1101 1100 1011 1010 1001 1000

How to make a JFrame Modal in Swing java

just replace JFrame to JDialog in class

public class MyDialog extends JFrame // delete JFrame and write JDialog

and then write setModal(true); in constructor

After that you will be able to construct your Form in netbeans and the form becomes modal

Why doesn't Mockito mock static methods?

As an addition to the Gerold Broser's answer, here an example of mocking a static method with arguments:

class Buddy {
  static String addHello(String name) {
    return "Hello " + name;


void testMockStaticMethods() {
  assertThat(Buddy.addHello("John")).isEqualTo("Hello John");

  try (MockedStatic<Buddy> theMock = Mockito.mockStatic(Buddy.class)) {
    theMock.when(() -> Buddy.addHello("John")).thenReturn("Guten Tag John");
    assertThat(Buddy.addHello("John")).isEqualTo("Guten Tag John");

  assertThat(Buddy.addHello("John")).isEqualTo("Hello John");

How do I tell Gradle to use specific JDK version?

If you are executing using gradle wrapper, you can run the command with JDK path like following


Removing duplicate values from a PowerShell array

In case you want to be fully bomb prove, this is what I would advice:

@('Apples', 'Apples ', 'APPLES', 'Banana') | 
    Sort-Object -Property @{Expression={$_.Trim()}} -Unique



This uses the Property parameter to first Trim() the strings, so extra spaces are removed and then selects only the -Unique values.

More info on Sort-Object:

Get-Help Sort-Object -ShowWindow

What is the recommended way to make a numeric TextField in JavaFX?

Starting with JavaFX 8u40, you can set a TextFormatter object on a text field:

UnaryOperator<Change> filter = change -> {
    String text = change.getText();

    if (text.matches("[0-9]*")) {
        return change;

    return null;
TextFormatter<String> textFormatter = new TextFormatter<>(filter);
fieldNport = new TextField();

This avoids both subclassing and duplicate change events which you will get when you add a change listener to the text property and modify the text in that listener.

How to drop a table if it exists?

Is it correct to do the following?

          FROM   dbo.Scores)
  DROP TABLE dbo.Scores

No. That will drop the table only if it contains any rows (and will raise an error if the table does not exist).

Instead, for a permanent table you can use

IF OBJECT_ID('dbo.Scores', 'U') IS NOT NULL 
  DROP TABLE dbo.Scores; 

Or, for a temporary table you can use

IF OBJECT_ID('tempdb.dbo.#TempTableName', 'U') IS NOT NULL
  DROP TABLE #TempTableName; 

SQL Server 2016+ has a better way, using DROP TABLE IF EXISTS …. See the answer by @Jovan.

Failing to run jar file from command line: “no main manifest attribute”

You can select the "Runnable JAR File" after you click on "Export".

You can specify your main driver in "Launch Configuration"

enter image description here enter image description here

How do I get the last day of a month?

If you want the date, given a month and a year, this seems about right:

public static DateTime GetLastDayOfMonth(this DateTime dateTime)
    return new DateTime(dateTime.Year, dateTime.Month, DateTime.DaysInMonth(dateTime.Year, dateTime.Month));

Load local HTML file in a C# WebBrowser

Update on @ghostJago answer above

for me it worked as the following lines in VS2017

string curDir = Directory.GetCurrentDirectory();
this.webBrowser1.Navigate(new Uri(String.Format("file:///{0}/my_html.html", curDir)));

How do I put variable values into a text string in MATLAB?

You can use fprintf/sprintf with familiar C syntax. Maybe something like:

fprintf('x = %d, y = %d \n x+y=%d \n x*y=%d \n x/y=%f\n', x,y,d,e,f)

reading your comment, this is how you use your functions from the main program:

x = 2;
y = 2;
[d e f] = answer(x,y);
fprintf('%d + %d = %d\n', x,y,d)
fprintf('%d * %d = %d\n', x,y,e)
fprintf('%d / %d = %f\n', x,y,f)

Also for the answer() function, you can assign the output values to a vector instead of three distinct variables:

function result=answer(x,y)

and call it simply as:

out = answer(x,y);

How to declare or mark a Java method as deprecated?

There are two things you can do:

  1. Add the @Deprecated annotation to the method, and
  2. Add a @deprecated tag to the javadoc of the method

You should do both!

Quoting the java documentation on this subject:

Starting with J2SE 5.0, you deprecate a class, method, or field by using the @Deprecated annotation. Additionally, you can use the @deprecated Javadoc tag tell developers what to use instead.

Using the annotation causes the Java compiler to generate warnings when the deprecated class, method, or field is used. The compiler suppresses deprecation warnings if a deprecated compilation unit uses a deprecated class, method, or field. This enables you to build legacy APIs without generating warnings.

You are strongly recommended to use the Javadoc @deprecated tag with appropriate comments explaining how to use the new API. This ensures developers will have a workable migration path from the old API to the new API

Getting "unixtime" in Java

Java 8 added a new API for working with dates and times. With Java 8 you can use

import java.time.Instant
long unixTimestamp =; returns an Instant that represents the current system time. With getEpochSecond() you get the epoch seconds (unix time) from the Instant.

Eclipse internal error while initializing Java tooling

Just change the following values at "eclipse.ini" file to the following:



  • You can find the "eclipse.ini" file by right click eclipse icon on and select "Open file location".
  • This error occurs because the eclipse is running out of memory, so we just increased the assigned memory for the eclipse application.

Set Windows process (or user) memory limit

Depending on your applications, it might be easier to limit the memory the language interpreter uses. For example with Java you can set the amount of RAM the JVM will be allocated.

Otherwise it is possible to set it once for each process with the windows API

SetProcessWorkingSetSize Function

Ifelse statement in R with multiple conditions

Very simple use of any

df <- <your structure>

df$Den <- apply(df,1,function(i) {ifelse(any( | any(i != 1), 0, 1)})

Section vs Article HTML5

My interpretation is: I think of YouTube it has a comment-section, and inside the comment-section there are multiple articles (in this case comments).

So a section is like a div-container that holds articles.

HTTP Error 401.2 - Unauthorized You are not authorized to view this page due to invalid authentication headers

Make sure Anonymous access is enabled on IIS -> Authentication.

But also right click on it, then click on Edit, and choose a domain\username and password. (With access to the physical folder of the application).

This Activity already has an action bar supplied by the window decor

I had toolbar added in my xml. Then in my activity i was adding this statement:


Removing this worked for me. I hope it helps someone.

pyplot scatter plot marker size

I also attempted to use 'scatter' initially for this purpose. After quite a bit of wasted time - I settled on the following solution.

import matplotlib.pyplot as plt
input_list = [{'x':100,'y':200,'radius':50, 'color':(0.1,0.2,0.3)}]    
output_list = []   
for point in input_list:
    output_list.append(plt.Circle((point['x'], point['y']), point['radius'], color=point['color'], fill=False))
ax = plt.gca(aspect='equal')
ax.set_xlim((0, 1000))
ax.set_ylim((0, 1000))
for circle in output_list:    

enter image description here

This is based on an answer to this question

Angular 5 Reactive Forms - Radio Button Group

I tried your code, you didn't assign/bind a value to your formControlName.

In HTML file:

<form [formGroup]="form">
     <input type="radio" value="Male" formControlName="gender">
     <input type="radio" value="Female" formControlName="gender">

In the TS file:

  form: FormGroup;
  constructor(fb: FormBuilder) { = 'Angular2'
    this.form ={
      gender: ['', Validators.required]

Make sure you use Reactive form properly: [formGroup]="form" and you don't need the name attribute.

In my sample. words male and female in span tags are the values display along the radio button and Male and Female values are bind to formControlName

See the screenshot: enter image description here

To make it shorter:

<form [formGroup]="form">
  <input type="radio" value='Male' formControlName="gender" >Male
  <input type="radio" value='Female' formControlName="gender">Female

enter image description here

Hope it helps:)

how to make a html iframe 100% width and height?

this code probable help you .

<iframe src="" onload="this.width=screen.width;this.height=screen.height;">

How to create a database from shell command?

cat filename.sql | mysql -u username -p # type mysql password when asked for it

Where filename.sql holds all the sql to create your database. Or...

echo "create database `database-name`" | mysql -u username -p

If you really only want to create a database.

Adding placeholder text to textbox

Wouldn't that just be something like this:

Textbox myTxtbx = new Textbox();
myTxtbx.Text = "Enter text here...";

myTxtbx.GotFocus += GotFocus.EventHandle(RemoveText);
myTxtbx.LostFocus += LostFocus.EventHandle(AddText);

public void RemoveText(object sender, EventArgs e)
    if (myTxtbx.Text == "Enter text here...") 
     myTxtbx.Text = "";

public void AddText(object sender, EventArgs e)
    if (string.IsNullOrWhiteSpace(myTxtbx.Text))
        myTxtbx.Text = "Enter text here...";

Thats just pseudocode but the concept is there.

Selenium wait until document is ready

Like Rubanov wrote for C#, i write it for Java, and it is:

    public void waitForPageLoaded() {
    ExpectedCondition<Boolean> expectation = new
            ExpectedCondition<Boolean>() {
                public Boolean apply(WebDriver driver) {
                    return (((JavascriptExecutor) driver).executeScript("return document.readyState").toString().equals("complete")&&((Boolean)((JavascriptExecutor)driver).executeScript("return == 0")));
    try {
        WebDriverWait waitForLoad = new WebDriverWait(driver, 30);
    } catch (Throwable error) {"Timeout waiting for Page Load Request to complete.");

Java properties UTF-8 encoding in Eclipse

Properties props = new Properties();
URL resource = getClass().getClassLoader().getResource("");         
props.load(new InputStreamReader(resource.openStream(), "UTF8"));

Works like a charm


How do you move a file?

i think in the svn browser in tortoisesvn you can just drag it from one place to another.

Why is visible="false" not working for a plain html table?

The reason that visible="false" does not work is because HTML is defined as a standard by a consortium group. The standard for the Table element does not have a visibility property defined.

You can see all the valid properties for a table by going to the standards web page for tables.

That page can be a bit hard to read, so here is a link to another page that makes it easier to read.

Find duplicate characters in a String and count the number of occurances using Java

 void Findrepeter(){
    String s="mmababctamantlslmag";
    int distinct = 0 ;

    for (int i = 0; i < s.length(); i++) {

        for (int j = 0; j < s.length(); j++) {


        String d=String.valueOf(s.charAt(i)).trim();
        distinct = 0;



How to iterate through table in Lua?

To iterate over all the key-value pairs in a table you can use pairs:

for k, v in pairs(arr) do
  print(k, v[1], v[2], v[3])


pears   2   p   green
apples  0   a   red
oranges 1   o   orange

Edit: Note that Lua doesn't guarantee any iteration order for the associative part of the table. If you want to access the items in a specific order, retrieve the keys from arr and sort it. Then access arr through the sorted keys:

local ordered_keys = {}

for k in pairs(arr) do
    table.insert(ordered_keys, k)

for i = 1, #ordered_keys do
    local k, v = ordered_keys[i], arr[ ordered_keys[i] ]
    print(k, v[1], v[2], v[3])


  apples  a   red     5
  oranges o   orange  12
  pears   p   green   7

How to normalize a NumPy array to within a certain range?

You are trying to min-max scale the values of audio between -1 and +1 and image between 0 and 255.

Using sklearn.preprocessing.minmax_scale, should easily solve your problem.


audio_scaled = minmax_scale(audio, feature_range=(-1,1))


shape = image.shape
image_scaled = minmax_scale(image.ravel(), feature_range=(0,255)).reshape(shape)

note: Not to be confused with the operation that scales the norm (length) of a vector to a certain value (usually 1), which is also commonly referred to as normalization.

AngularJS ng-click stopPropagation

ngClick directive (as well as all other event directives) creates $event variable which is available on same scope. This variable is a reference to JS event object and can be used to call stopPropagation():

  <tr ng-repeat="user in users" ng-click="showUser(user)">
      <button class="btn" ng-click="deleteUser(, $index); $event.stopPropagation();">


Adding iOS UITableView HeaderView (not section header)

You can do it pretty easy in Interface Builder. Just create a view with a table and drop another view onto the table. This will become the table header view. Add your labels and image to that view. See the pic below for the view hierarchy. View Hierarchy in Interface Builder

How to hide the soft keyboard from inside a fragment?

Use this:

Button loginBtn = view.findViewById(;
loginBtn.setOnClickListener(new View.OnClickListener() {
   public void onClick(View v) {
      InputMethodManager imm = (InputMethodManager) getActivity().getSystemService(getActivity().INPUT_METHOD_SERVICE);
      imm.hideSoftInputFromWindow(v.getWindowToken(), 0);

How to easily get network path to the file you are working on?

Here's how to get the filepath of the file in Excel 2010.

1) Right click on the Ribbon.
2) Click on "Customize the Ribbon"
3) On the right hand side, click "New Group." This will add a new tab to the Ribbon. If you want to, click on the "Rename" button the right side and name your tab. For example, I named the tab "Doc Path." This step is optional
4) Under "Choose Commands From" on the left hand side, choose "Commands Not in the Ribbon."
5) Select "Document Location" and "Add" it to your newly created group.
6) The filepath should now appear under the newly created tab on the ribbon.

Angular 2: How to style host element of the component?

Try the :host > /deep/ :

Add the following to the parent.component.less file

:host {
    /deep/ app-child-component {
       //your child style

Replace the app-child-component by your child selector

How to capture a list of specific type with mockito

Based on @tenshi's and @pkalinow's comments (also kudos to @rogerdpack), the following is a simple solution for creating a list argument captor that also disables the "uses unchecked or unsafe operations" warning:

final ArgumentCaptor<List<SomeType>> someTypeListArgumentCaptor =

Full example here and corresponding passing CI build and test run here.

Our team has been using this for some time in our unit tests and this looks like the most straightforward solution for us.

Error:Execution failed for task ':ProjectName:mergeDebugResources'. > Crunching Cruncher *some file* failed, see logs

Ok, I just faced this problem and tried all of the steps mentioned above but didn't help. So what I did, I checked what image extension it was before I renamed it to .png. In my case it was .jpeg. So I renamed it back to .jpeg and kept the same original file in drawable. And bingo, it just worked fine.

So the solution is, use the file without changing extension, be it .png or .jpeg, keep it the original way.

Thought to share if it helps anyone. Thanks.

font-family is inherit. How to find out the font-family in chrome developer pane?

Developer Tools > Elements > Computed > Rendered Fonts

The picture you attached to your question shows the Style tab. If you change to the next tab, Computed, you can check the Rendered Fonts, that shows the actual font-family rendered.

Developer Tools > Elements > Computed > Rendered Fonts

Foreach loop in C++ equivalent of C#

In C++0x you have

for(string str: strarr) { ... }

But till then use ordinary for loop.

How to respond to clicks on a checkbox in an AngularJS directive?

I prefer to use the ngModel and ngChange directives when dealing with checkboxes. ngModel allows you to bind the checked/unchecked state of the checkbox to a property on the entity:

<input type="checkbox" ng-model="entity.isChecked">

Whenever the user checks or unchecks the checkbox the entity.isChecked value will change too.

If this is all you need then you don't even need the ngClick or ngChange directives. Since you have the "Check All" checkbox, you obviously need to do more than just set the value of the property when someone checks a checkbox.

When using ngModel with a checkbox, it's best to use ngChange rather than ngClick for handling checked and unchecked events. ngChange is made for just this kind of scenario. It makes use of the ngModelController for data-binding (it adds a listener to the ngModelController's $viewChangeListeners array. The listeners in this array get called after the model value has been set, avoiding this problem).

<input type="checkbox" ng-model="entity.isChecked" ng-change="selectEntity()">

... and in the controller ...

var model = {};
$scope.model = model;

// This property is bound to the checkbox in the table header
model.allItemsSelected = false;

// Fired when an entity in the table is checked
$scope.selectEntity = function () {
    // If any entity is not checked, then uncheck the "allItemsSelected" checkbox
    for (var i = 0; i < model.entities.length; i++) {
        if (!model.entities[i].isChecked) {
            model.allItemsSelected = false;

    // ... otherwise ensure that the "allItemsSelected" checkbox is checked
    model.allItemsSelected = true;

Similarly, the "Check All" checkbox in the header:

    <input type="checkbox" ng-model="model.allItemsSelected" ng-change="selectAll()">

... and ...

// Fired when the checkbox in the table header is checked
$scope.selectAll = function () {
    // Loop through all the entities and set their isChecked property
    for (var i = 0; i < model.entities.length; i++) {
        model.entities[i].isChecked = model.allItemsSelected;


What is the best way to... add a CSS class to the <tr> containing the entity to reflect its selected state?

If you use the ngModel approach for the data-binding, all you need to do is add the ngClass directive to the <tr> element to dynamically add or remove the class whenever the entity property changes:

<tr ng-repeat="entity in model.entities" ng-class="{selected: entity.isChecked}">

See the full Plunker here.

What does void* mean and how to use it?

C is remarkable in this regard. One can say void is nothingness void* is everything (can be everything).

It's just this tiny * which makes the difference.

Rene has pointed it out. A void * is a Pointer to some location. What there is how to "interpret" is left to the user.

It's the only way to have opaque types in C. Very prominent examples can be found e.g in glib or general data structure libraries. It's treated very detailed in "C Interfaces and implementations".

I suggest you read the complete chapter and try to understand the concept of a pointer to "get it".

java howto ArrayList push, pop, shift, and unshift

I was facing with this problem some time ago and I found java.util.LinkedList is best for my case. It has several methods, with different namings, but they're doing what is needed:

push()    -> LinkedList.addLast(); // Or just LinkedList.add();
pop()     -> LinkedList.pollLast();
shift()   -> LinkedList.pollFirst();
unshift() -> LinkedList.addFirst();

CSS smooth bounce animation

In case you're already using the transform property for positioning your element (as I currently am), you can also animate the top margin:

.ball {
  animation: bounce 1s infinite alternate;
  -webkit-animation: bounce 1s infinite alternate;

@keyframes bounce {
  from {
    margin-top: 0;
  to {
    margin-top: -15px;

No plot window in matplotlib

Another possibility when using easy_install is that you need to require the most recent version of matplotlib. Try:

import pkg_resources

before you import matplotlib or any of its modules.

Java HashMap performance optimization / alternative

As pointed out, your hashcode implementation has too many collisions, and fixing it should result in decent performance. Moreover, caching hashCodes and implementing equals efficiently will help.

If you need to optimize even further:

By your description, there are only (52 * 51 / 2) * (52 * 51 * 50 / 6) = 29304600 different keys (of which 26000000, i.e. about 90%, will be present). Therefore, you can design a hash function without any collisions, and use a simple array rather than a hashmap to hold your data, reducing memory consumption and increasing lookup speed:

T[] array = new T[Key.maxHashCode];

void put(Key k, T value) {
    array[k.hashCode()] = value;

T get(Key k) {
    return array[k.hashCode()];

(Generally, it is impossible to design an efficient, collision-free hash function that clusters well, which is why a HashMap will tolerate collisions, which incurs some overhead)

Assuming a and b are sorted, you might use the following hash function:

public int hashCode() {
    assert a[0] < a[1]; 
    int ahash = a[1] * a[1] / 2 
              + a[0];

    assert b[0] < b[1] && b[1] < b[2];

    int bhash = b[2] * b[2] * b[2] / 6
              + b[1] * b[1] / 2
              + b[0];
    return bhash * 52 * 52 / 2 + ahash;

static final int maxHashCode = 52 * 52 / 2 * 52 * 52 * 52 / 6;  

I think this is collision-free. Proving this is left as an exercise for the mathematically inclined reader.

Is Java RegEx case-insensitive?

RegexBuddy is telling me if you want to include it at the beginning, this is the correct syntax:


Is there an exponent operator in C#?

The C# language doesn't have a power operator. However, the .NET Framework offers the Math.Pow method:

Returns a specified number raised to the specified power.

So your example would look like this:

float Result, Number1, Number2;

Number1 = 2;
Number2 = 2;

Result = Math.Pow(Number1, Number2);

How can I get terminal output in python?

You can use Popen in subprocess as they suggest.

with os, which is not recomment, it's like below:

import os
a  = os.popen('pwd').readlines()

Word wrapping in phpstorm

In PhpStorm 2019.1.3, it is possible to enable soft wrap for some file types only.

enter image description here

plot data from CSV file with matplotlib

According to the docs numpy.loadtxt is

a fast reader for simply formatted files. The genfromtxt function provides more sophisticated handling of, e.g., lines with missing values.

so there are only a few options to handle more complicated files. As mentioned numpy.genfromtxt has more options. So as an example you could use

import numpy as np
data = np.genfromtxt('e:\dir1\datafile.csv', delimiter=',', skip_header=10,
                     skip_footer=10, names=['x', 'y', 'z'])

to read the data and assign names to the columns (or read a header line from the file with names=True) and than plot it with

ax1.plot(data['x'], data['y'], color='r', label='the data')

I think numpy is quite well documented now. You can easily inspect the docstrings from within ipython or by using an IDE like spider if you prefer to read them rendered as HTML.

Different class for the last element in ng-repeat

It's easier and cleaner to do it with CSS.


<div ng-repeat="file in files" class="file">
  {{ }}


.file:last-of-type {
    color: #800;

The :last-of-type selector is currently supported by 98% of browsers

How to add a new line of text to an existing file in Java?

Starting from Java 7:

Define a path and the String containing the line separator at the beginning:

Path p = Paths.get("C:\\Users\\first.last\\test.txt");
String s = System.lineSeparator() + "New Line!";

and then you can use one of the following approaches:

  1. Using Files.write (small files):

    try {
        Files.write(p, s.getBytes(), StandardOpenOption.APPEND);
    } catch (IOException e) {
  2. Using Files.newBufferedWriter(text files):

    try (BufferedWriter writer = Files.newBufferedWriter(p, StandardOpenOption.APPEND)) {
    } catch (IOException ioe) {
        System.err.format("IOException: %s%n", ioe);
  3. Using Files.newOutputStream (interoperable with APIs):

    try (OutputStream out = new BufferedOutputStream(Files.newOutputStream(p, StandardOpenOption.APPEND))) {
    } catch (IOException e) {
  4. Using Files.newByteChannel (random access files):

    try (SeekableByteChannel sbc = Files.newByteChannel(p, StandardOpenOption.APPEND)) {
    } catch (IOException e) {
  5. Using (random access files):

    try (FileChannel sbc =, StandardOpenOption.APPEND)) {
    } catch (IOException e) {

Details about these methods can be found in the Oracle's tutorial.

Adding a newline character within a cell (CSV)

This question was answered well at Can you encode CR/LF in into CSV files?.

Consider also reverse engineering multiple lines in Excel. To embed a newline in an Excel cell, press Alt+Enter. Then save the file as a .csv. You'll see that the double-quotes start on one line and each new line in the file is considered an embedded newline in the cell.

SQL: How do I SELECT only the rows with a unique value on certain column?

Try this:

        max (activity) 
group by
         count (activity) = 1

Replace string within file contents

with open("Stud.txt", "rt") as fin:
    with open("out.txt", "wt") as fout:
        for line in fin:
            fout.write(line.replace('A', 'Orange'))

Is it possible to run an .exe or .bat file on 'onclick' in HTML

You can do it on Internet explorer with OCX component and on chrome browser using a chrome extension chrome document in any case need additional settings on the client system!

Important part of chrome extension source:

var port = chrome.runtime.connectNative(""); 
      port.postMessage("send some data to STDIO");

permission file:

      "name": "",
      "description": "Name of your extension",
      "path": "myapp.exe",
      "type": "stdio",
      "allowed_origins": [

and windows registry settings:

REG_EXPAND_SZ : c:\permissionsettings.json

Is there a way to access the "previous row" value in a SELECT statement?

SQL has no built in notion of order, so you need to order by some column for this to be meaningful. Something like this:

select t1.value - t2.value from table t1, table t2 
where t1.primaryKey = t2.primaryKey - 1

If you know how to order things but not how to get the previous value given the current one (EG, you want to order alphabetically) then I don't know of a way to do that in standard SQL, but most SQL implementations will have extensions to do it.

Here is a way for SQL server that works if you can order rows such that each one is distinct:

select  rank() OVER (ORDER BY id) as 'Rank', value into temp1 from t

select t1.value - t2.value from temp1 t1, temp1 t2 
where t1.Rank = t2.Rank - 1

drop table temp1

If you need to break ties, you can add as many columns as necessary to the ORDER BY.

How does C compute sin() and other math functions?

As many people pointed out, it is implementation dependent. But as far as I understand your question, you were interested in a real software implemetnation of math functions, but just didn't manage to find one. If this is the case then here you are:

  • Download glibc source code from
  • Look at file dosincos.c located in unpacked glibc root\sysdeps\ieee754\dbl-64 folder
  • Similarly you can find implementations of the rest of the math library, just look for the file with appropriate name

You may also have a look at the files with the .tbl extension, their contents is nothing more than huge tables of precomputed values of different functions in a binary form. That is why the implementation is so fast: instead of computing all the coefficients of whatever series they use they just do a quick lookup, which is much faster. BTW, they do use Tailor series to calculate sine and cosine.

I hope this helps.

Best practices with STDIN in Ruby?

Quick and simple:

STDIN.gets.chomp == 'YES'

How to change ReactJS styles dynamically?

Ok, finally found the solution.

Probably due to lack of experience with ReactJS and web development...

    var Task = React.createClass({
    render: function() {
      var percentage = this.props.children + '%';
        <div className="ui-progressbar-value ui-widget-header ui-corner-left" style={{width : percentage}}/>

I created the percentage variable outside in the render function.

Is JavaScript object-oriented?

it is a good thread. Here's some resources i like. Most people start out with prototype, jquery, or one of the top 6 libs(mootools, ExtJS, YUI), which have different object models. Prototype tries to replicate classical O-O as most people think of it

Here's a picture of prototypes and functions that i refer to a lot

How do I join two SQLite tables in my Android application?

"Ambiguous column" usually means that the same column name appears in at least two tables; the database engine can't tell which one you want. Use full table names or table aliases to remove the ambiguity.

Here's an example I happened to have in my editor. It's from someone else's problem, but should make sense anyway.

select P.* 
from product_has_image P
inner join highest_priority_images H 
        on (H.id_product = P.id_product and H.priority = p.priority)

Java: Best way to iterate through a Collection (here ArrayList)

The first option is better performance wise (As ArrayList implement RandomAccess interface). As per the java doc, a List implementation should implement RandomAccess interface if, for typical instances of the class, this loop:

 for (int i=0, n=list.size(); i < n; i++)

runs faster than this loop:

 for (Iterator i=list.iterator(); i.hasNext(); );

I hope it helps. First option would be slow for sequential access lists.

How to make a new line or tab in <string> XML (eclipse/android)?

Use \t to add tab and \n for new line, here is a simple example below.

<string name="list_with_tab_tag">\tbanana\torange\tblueberry\tmango</string>
<string name="sentence_with_new_line_tag">This is the first sentence\nThis is the second scentence\nThis is the third sentence</string>

Run MySQLDump without Locking Tables

When using MySQL Workbench, at Data Export, click in Advanced Options and uncheck the "lock-tables" options.

enter image description here

Ignore mapping one property with Automapper

You can do this:

conf.CreateMap<SourceType, DestinationType>()
   .ForSourceMember(x => x.SourceProperty, y => y.Ignore());

Or, in latest version of Automapper, you simply want to tell Automapper to not validate the field

conf.CreateMap<SourceType, DestinationType>()
   .ForSourceMember(x => x.SourceProperty, y => y.DoNotValidate());

How to run TypeScript files from command line?

This question was posted in 2015. In 2018, node recognizes both .js and .ts. So, running node file.ts will also run.

TypeError: 'str' does not support the buffer interface

For Python 3.x you can convert your text to raw bytes through:

bytes("my data", "encoding")

For example:

bytes("attack at dawn", "utf-8")

The object returned will work with outfile.write.

What is Java EE?

J2EE traditionally referred to products and standards released by Sun. For example if you were developing a standard J2EE web application, you would be using EJBs, Java Server Faces, and running in an application server that supports the J2EE standard. However since there is such a huge open source plethora of libraries and products that do the same jobs as well as (and many will argue better) then these Sun offerings, the day to day meaning of J2EE has migrated into referring to these as well (For instance a Spring/Tomcat/Hibernate solution) in many minds.

This is a great book in my opinion that discusses the 'open source' approach to J2EE

How to create JSON post to api using C#

Try using Web API HttpClient

    static async Task RunAsync()
        using (var client = new HttpClient())
            client.BaseAddress = new Uri("");
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            // HTTP POST
            var obj = new MyObject() { Str = "MyString"};
            response = await client.PostAsJsonAsync("POST URL GOES HERE?", obj );
            if (response.IsSuccessStatusCode)
                response.//.. Contains the returned content.

You can find more details here Web API Clients

ESLint - "window" is not defined. How to allow global variables in package.json

I found it on this page:

In package.json, this works:

"eslintConfig": {
  "globals": {
    "window": true

Calculating a directory's size using Python?

Admittedly, this is kind of hackish and only works on Unix/Linux.

It matches du -sb . because in effect this is a Python bash wrapper that runs the du -sb . command.

import subprocess

def system_command(cmd):
    """"Function executes cmd parameter as a bash command."""
    p = subprocess.Popen(cmd,
    stdout, stderr = p.communicate()
    return stdout, stderr

size = int(system_command('du -sb . ')[0].split()[0])

In Angular, how to add Validator to FormControl after control is created?

I think the selected answer is not correct, as the original question is "how to add a new validator after create the formControl".

As far as I know, that's not possible. The only thing you can do, is create the array of validators dynamicaly.

But what we miss is to have a function addValidator() to not override the validators already added to the formControl. If anybody has an answer for that requirement, would be nice to be posted here.

UNIX nonblocking I/O: O_NONBLOCK vs. FIONBIO

I believe fcntl() is a POSIX function. Where as ioctl() is a standard UNIX thing. Here is a list of POSIX io. ioctl() is a very kernel/driver/OS specific thing, but i am sure what you use works on most flavors of Unix. some other ioctl() stuff might only work on certain OS or even certain revs of it's kernel.

wp_nav_menu change sub-menu class name?

There is no option for this, but you can extend the 'walker' object that WordPress uses to create the menu HTML. Only one method needs to be overridden:

class My_Walker_Nav_Menu extends Walker_Nav_Menu {
  function start_lvl(&$output, $depth) {
    $indent = str_repeat("\t", $depth);
    $output .= "\n$indent<ul class=\"my-sub-menu\">\n";

Then you just pass an instance of your walker as an argument to wp_nav_menu like so:

'walker' => new My_Walker_Nav_Menu()

How do you copy and paste into Git Bash

In the properties of the console you can activate the "Quick Edit Mode" under "Edit Options", that way you can paste inside the console just right clicking. Or you can use 'Insert' as they say.

Drop all tables command

rm db/development.sqlite3

socket.emit() vs. socket.send()

socket.send is implemented for compatibility with vanilla WebSocket interface. socket.emit is feature of Socket.IO only. They both do the same, but socket.emit is a bit more convenient in handling messages.

return string with first match Regex

You shouldn't be using .findall() at all - .search() is what you want. It finds the leftmost match, which is what you want (or returns None if no match exists).

m =, text)
result = if m else ""

Whether you want to put that in a function is up to you. It's unusual to want to return an empty string if no match is found, which is why nothing like that is built in. It's impossible to get confused about whether .search() on its own finds a match (it returns None if it didn't, or an SRE_Match object if it did).

.htaccess - how to force "www." in a generic way?

RewriteEngine On

RewriteCond %{HTTP_HOST} ^[^.]+\.[^.]+$
RewriteRule ^ http://www.%{HTTP_HOST}%{REQUEST_URI} [NE,L,R=301]

This redirects to excluding subdomains.

jquery getting post action url

$('#signup').on("submit", function(event) {
    $form = $(this); //wrap this in jQuery

    alert('the action is: ' + $form.attr('action'));

Add primary key to existing table

There is already an primary key in your table. You can't just add primary key,otherwise will cause error. Because there is one primary key for sql table.

First, you have to drop your old primary key.



SQL Server / Oracle / MS Access:

DROP CONSTRAINT 'constraint name';

You have to find the constraint name in your table. If you had given constraint name when you created table,you can easily use the constraint name(ex:PK_Persion).

Second,Add primary key.

MySQL / SQL Server / Oracle / MS Access:


or the better one below


This can set constraint name by developer. It's more easily to maintain the table.

I got a little confuse when i have looked all answers. So I research some document to find every detail. Hope this answer can help other SQL beginner.


In Java, how do I get the difference in seconds between 2 dates?

That should do it:

Date a = ...;
Date b = ...;


Here the relevant documentation: Date.getTime(). Be aware that this will only work for dates after January 1, 1970, 00:00:00 GMT

ThreeJS: Remove object from scene

You can use this

function removeEntity(object) {
    var scene = document.querySelectorAll("scene");                               //clear the objects from the scene
    for (var i = 0; i < scene.length; i++) {                                    //loop through to get all object in the scene
    var scene =document.getElementById("scene");                                  
    scene.removeChild(scene.childNodes[0]);                                        //remove all specified objects

Execute a shell function with timeout

timeout is a command - so it is executing in a subprocess of your bash shell. Therefore it has no access to your functions defined in your current shell.

The command timeout is given is executed as a subprocess of timeout - a grand-child process of your shell.

You might be confused because echo is both a shell built-in and a separate command.

What you can do is put your function in it's own script file, chmod it to be executable, then execute it with timeout.

Alternatively fork, executing your function in a sub-shell - and in the original process, monitor the progress, killing the subprocess if it takes too long.

Best way to compare two complex objects

Thanks to the example of Jonathan. I expanded it for all cases (arrays, lists, dictionaries, primitive types).

This is a comparison without serialization and does not require the implementation of any interfaces for compared objects.

        /// <summary>Returns description of difference or empty value if equal</summary>
        public static string Compare(object obj1, object obj2, string path = "")
            string path1 = string.IsNullOrEmpty(path) ? "" : path + ": ";
            if (obj1 == null && obj2 != null)
                return path1 + "null != not null";
            else if (obj2 == null && obj1 != null)
                return path1 + "not null != null";
            else if (obj1 == null && obj2 == null)
                return null;

            if (!obj1.GetType().Equals(obj2.GetType()))
                return "different types: " + obj1.GetType() + " and " + obj2.GetType();

            Type type = obj1.GetType();
            if (path == "")
                path = type.Name;

            if (type.IsPrimitive || typeof(string).Equals(type))
                if (!obj1.Equals(obj2))
                    return path1 + "'" + obj1 + "' != '" + obj2 + "'";
                return null;
            if (type.IsArray)
                Array first = obj1 as Array;
                Array second = obj2 as Array;
                if (first.Length != second.Length)
                    return path1 + "array size differs (" + first.Length + " vs " + second.Length + ")";

                var en = first.GetEnumerator();
                int i = 0;
                while (en.MoveNext())
                    string res = Compare(en.Current, second.GetValue(i), path);
                    if (res != null)
                        return res + " (Index " + i + ")";
            else if (typeof(System.Collections.IEnumerable).IsAssignableFrom(type))
                System.Collections.IEnumerable first = obj1 as System.Collections.IEnumerable;
                System.Collections.IEnumerable second = obj2 as System.Collections.IEnumerable;

                var en = first.GetEnumerator();
                var en2 = second.GetEnumerator();
                int i = 0;
                while (en.MoveNext())
                    if (!en2.MoveNext())
                        return path + ": enumerable size differs";

                    string res = Compare(en.Current, en2.Current, path);
                    if (res != null)
                        return res + " (Index " + i + ")";
                foreach (PropertyInfo pi in type.GetProperties(BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public))
                        var val = pi.GetValue(obj1);
                        var tval = pi.GetValue(obj2);
                        if (path.EndsWith("." + pi.Name))
                            return null;
                        var pathNew = (path.Length == 0 ? "" : path + ".") + pi.Name;
                        string res = Compare(val, tval, pathNew);
                        if (res != null)
                            return res;
                    catch (TargetParameterCountException)
                        //index property
                foreach (FieldInfo fi in type.GetFields(BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public))
                    var val = fi.GetValue(obj1);
                    var tval = fi.GetValue(obj2);
                    if (path.EndsWith("." + fi.Name))
                        return null;
                    var pathNew = (path.Length == 0 ? "" : path + ".") + fi.Name;
                    string res = Compare(val, tval, pathNew);
                    if (res != null)
                        return res;
            return null;

For easy copying of the code created repository

const vs constexpr on variables

A constexpr symbolic constant must be given a value that is known at compile time. For example:

?constexpr int max = 100; 
void use(int n)
    constexpr int c1 = max+7; // OK: c1 is 107
    constexpr int c2 = n+7;   // Error: we don’t know the value of c2
    // ...

To handle cases where the value of a “variable” that is initialized with a value that is not known at compile time but never changes after initialization, C++ offers a second form of constant (a const). For Example:

?constexpr int max = 100; 
void use(int n)
    constexpr int c1 = max+7; // OK: c1 is 107
    const int c2 = n+7; // OK, but don’t try to change the value of c2
    // ...
    c2 = 7; // error: c2 is a const

Such “const variables” are very common for two reasons:

  1. C++98 did not have constexpr, so people used const.
  2. List item “Variables” that are not constant expressions (their value is not known at compile time) but do not change values after initialization are in themselves widely useful.

Reference : "Programming: Principles and Practice Using C++" by Stroustrup

no overload for matches delegate 'system.eventhandler'

Change the klik method as follows:

public void klik(object pea, EventArgs e)
    Bitmap c = this.DrawMandel();
    Button btn = pea as Button;
    Graphics gr = btn.CreateGraphics();
    gr.DrawImage(b, 150, 200);

Batch script to install MSI

This is how to install a normal MSI file silently:

msiexec.exe /i c:\setup.msi /QN /L*V "C:\Temp\msilog.log"

Quick explanation:

 /L*V "C:\Temp\msilog.log"= verbose logging at indicated path
 /QN = run completely silently
 /i = run install sequence 

The msiexec.exe command line is extensive with support for a variety of options. Here is another overview of the same command line interface. Here is an annotated versions (was broken, resurrected via way back machine).

It is also possible to make a batch file a lot shorter with constructs such as for loops as illustrated here for Windows Updates.

If there are check boxes that must be checked during the setup, you must find the appropriate PUBLIC PROPERTIES attached to the check box and set it at the command line like this:

msiexec.exe /i c:\setup.msi /QN /L*V "C:\Temp\msilog.log" STARTAPP=1 SHOWHELP=Yes

These properties are different in each MSI. You can find them via the verbose log file or by opening the MSI in Orca, or another appropriate tool. You must look either in the dialog control section or in the Property table for what the property name is. Try running the setup and create a verbose log file first and then search the log for messages ala "Setting property..." and then see what the property name is there. Then add this property with the value from the log file to the command line.

Also have a look at how to use transforms to customize the MSI beyond setting command line parameters: How to make better use of MSI files

How can I get the full/absolute URL (with domain) in Django?

In your view, just do this:

base_url =  "{0}://{1}{2}".format(request.scheme, request.get_host(), request.path)

How to compare only Date without Time in DateTime types in Linq to SQL with Entity Framework?

For a true comparison, you can use:


How to use a typescript enum value in an Angular2 ngSwitch statement

This's simple and works like a charm :) just declare your enum like this and you can use it on HTML template

  statusEnum: typeof StatusEnum = StatusEnum;

How do I update Homebrew?

  • cd /usr/local
  • git status
  • Discard all the changes (unless you actually want to try to commit to Homebrew - you probably don't)
  • git status til it's clean
  • brew update

Regex to remove letters, symbols except numbers

You can use \D which means non digits.

var removedText = self.val().replace(/\D+/g, '');


You could also use the HTML5 number input.

<input type="number" name="digit" />


How to sort a list of lists by a specific index of the inner list?

This is a job for itemgetter

>>> from operator import itemgetter
>>> L=[[0, 1, 'f'], [4, 2, 't'], [9, 4, 'afsd']]
>>> sorted(L, key=itemgetter(2))
[[9, 4, 'afsd'], [0, 1, 'f'], [4, 2, 't']]

It is also possible to use a lambda function here, however the lambda function is slower in this simple case

How to show full column content in a Spark Dataframe?,false) did the trick for me in Scala.

Error: Unable to run mksdcard SDK tool

For UBUNTU 15.04,15.10,16.04 LTS, Debian 8 & Debian 9 Try this command:

sudo apt-get install lib32stdc++6

PHP str_replace replace spaces with underscores

I'll suggest that you use this as it will check for both single and multiple occurrence of white space (as suggested by Lucas Green).

$journalName = preg_replace('/\s+/', '_', $journalName);

instead of:

$journalName = str_replace(' ', '_', $journalName);

Is `shouldOverrideUrlLoading` really deprecated? What can I use instead?


public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
    return shouldOverrideUrlLoading(view, request.getUrl().toString());

Proper way to exit command line program?

if you do ctrl-z and then type exit it will close background applications.

Ctrl+Q is another good way to kill the application.

Copying an array of objects into another array in javascript

If you want to keep reference:

Array.prototype.push.apply(destinationArray, sourceArray);

How to tell CRAN to install package dependencies automatically?

Another possibility is to select the Install Dependencies checkbox In the R package installer, on the bottom right:

enter image description here

How to get the name of a class without the package?


Returns the simple name of the underlying class as given in the source code. Returns an empty string if the underlying class is anonymous.

The simple name of an array is the simple name of the component type with "[]" appended. In particular the simple name of an array whose component type is anonymous is "[]".

It is actually stripping the package information from the name, but this is hidden from you.

File count from a folder

Try following code to get count of files in the folder

string strDocPath = Server.MapPath('Enter your path here'); 
int docCount = Directory.GetFiles(strDocPath, "*", 

How do I write JSON data to a file?

if you are trying to write a pandas dataframe into a file using a json format i'd recommend this

saveFile = open(destination, 'w')

Best practice for instantiating a new Android Fragment

The only benefit in using the newInstance() that I see are the following:

  1. You will have a single place where all the arguments used by the fragment could be bundled up and you don't have to write the code below everytime you instantiate a fragment.

    Bundle args = new Bundle();
    args.putInt("someInt", someInt);
    args.putString("someString", someString);
    // Put any other arguments
  2. Its a good way to tell other classes what arguments it expects to work faithfully(though you should be able to handle cases if no arguments are bundled in the fragment instance).

So, my take is that using a static newInstance() to instantiate a fragment is a good practice.

Python: instance has no attribute

Your class doesn't have a __init__(), so by the time it's instantiated, the attribute atoms is not present. You'd have to do C.setdata('something') so C.atoms becomes available.

>>> C = Residues()
>>> C.atoms.append('thing')

Traceback (most recent call last):
  File "<pyshell#84>", line 1, in <module>
AttributeError: Residues instance has no attribute 'atoms'

>>> C.setdata('something')
>>> C.atoms.append('thing')   # now it works

Unlike in languages like Java, where you know at compile time what attributes/member variables an object will have, in Python you can dynamically add attributes at runtime. This also implies instances of the same class can have different attributes.

To ensure you'll always have (unless you mess with it down the line, then it's your own fault) an atoms list you could add a constructor:

def __init__(self):
    self.atoms = []

MySQL Where DateTime is greater than today

FROM customer 
WHERE joiningdate >= NOW();

How to make a class JSON serializable

For more complex classes you could consider the tool jsonpickle:

jsonpickle is a Python library for serialization and deserialization of complex Python objects to and from JSON.

The standard Python libraries for encoding Python into JSON, such as the stdlib’s json, simplejson, and demjson, can only handle Python primitives that have a direct JSON equivalent (e.g. dicts, lists, strings, ints, etc.). jsonpickle builds on top of these libraries and allows more complex data structures to be serialized to JSON. jsonpickle is highly configurable and extendable–allowing the user to choose the JSON backend and add additional backends.

(link to jsonpickle on PyPi)

Php header location redirect not working

Pekka answered my question in the comments. He didn't post an answer, so I am now. Use the exit() method after the header redirect. For some reason the rest of the code of the page continues to execute after the header() method redirect. When the rest of the code executes, the echo statement is outputted to the page. And you can't redirect using the header function after you output to the page. To avoid rest of the code from executing, use exit(). Thanks Pekka.

UPDATE: When using the web browser Internet Explorer, I have noticed that $_POST['cancel'] is not reliable. I am not exactly sure why this is, but I suspect IE posts additional variables on a form submit, specifically the variable 'cancel' is posted. I solved this by using a variable name other than 'cancel'. The combination of using exit() and a unique variable name is working for me.

How to iterate through range of Dates in Java?

Why not use epoch and loop through easily.

long startDateEpoch = new java.text.SimpleDateFormat("dd/MM/yyyy").parse(startDate).getTime() / 1000;

    long endDateEpoch = new java.text.SimpleDateFormat("dd/MM/yyyy").parse(endDate).getTime() / 1000;

    long i;
    for(i=startDateEpoch ; i<=endDateEpoch; i+=86400){



Access denied for user 'root'@'localhost' with PHPMyAdmin

Edit your phpmyadmin file and if you have Password, insert that in front of Password in following code:

$cfg['Servers'][$i]['verbose'] = 'localhost';
$cfg['Servers'][$i]['host'] = 'localhost';
$cfg['Servers'][$i]['port'] = '3306';
$cfg['Servers'][$i]['socket'] = '';
$cfg['Servers'][$i]['connect_type'] = 'tcp';
$cfg['Servers'][$i]['extension'] = 'mysqli';
$cfg['Servers'][$i]['auth_type'] = 'config';
$cfg['Servers'][$i]['user'] = '**your-root-username**';
$cfg['Servers'][$i]['password'] = '**root-password**';
$cfg['Servers'][$i]['AllowNoPassword'] = true;

Spring CORS No 'Access-Control-Allow-Origin' header is present

Change the CorsMapping from registry.addMapping("/*") to registry.addMapping("/**") in addCorsMappings method.

Check out this Spring CORS Documentation .

From the documentation -

Enabling CORS for the whole application is as simple as:

public class WebConfig extends WebMvcConfigurerAdapter {

    public void addCorsMappings(CorsRegistry registry) {

You can easily change any properties, as well as only apply this CORS configuration to a specific path pattern:

public class WebConfig extends WebMvcConfigurerAdapter {
    public void addCorsMappings(CorsRegistry registry) {
            .allowedMethods("PUT", "DELETE")
            .allowedHeaders("header1", "header2", "header3")
            .exposedHeaders("header1", "header2")

Controller method CORS configuration

public class AccountController {
  public Account retrieve(@PathVariable Long id) {
    // ...

To enable CORS for the whole controller -

@CrossOrigin(origins = "", maxAge = 3600)
public class AccountController {

    public Account retrieve(@PathVariable Long id) {
        // ...

    @RequestMapping(method = RequestMethod.DELETE, path = "/{id}")
    public void remove(@PathVariable Long id) {
        // ...

You can even use both controller-level and method-level CORS configurations; Spring will then combine attributes from both annotations to create merged CORS configuration.

@CrossOrigin(maxAge = 3600)
public class AccountController {

    public Account retrieve(@PathVariable Long id) {
        // ...

    @RequestMapping(method = RequestMethod.DELETE, path = "/{id}")
    public void remove(@PathVariable Long id) {
        // ...

How to install a certificate in Xcode (preparing for app store submission)

These instructions are for XCode 6.4 (since I couldn't find the update for the recent versions even this was a bit outdated)

a) Part on the developers' website:

Sign in into:

Member Center

Certificates, Identifiers & Profiles


Click "+" to add, and then follow the instructions. You will need to open "Keychain", there under "Keychain Access" menu > "Certificate Assistant>", choose "Request a Certificate From a Certificate Authority" etc.

b) XCode part:

After all, you need to go to XCode, and open XCode>Preferences..., choose your Apple ID > View Details... > click that rounded arrow to update as well as "+" to check for iOS Distribution or iOS Developer Signing Identities.

MySQL Delete all rows from table and reset ID to zero

If you cannot use TRUNCATE (e.g. because of foreign key constraints) you can use an alter table after deleting all rows to restart the auto_increment:


Apache giving 403 forbidden errors

Check that :

  • Apache can physically access the file (the user that run apache, probably www-data or apache, can access the file in the filesystem)
  • Apache can list the content of the folder (read permission)
  • Apache has a "Allow" directive for that folder. There should be one for /var/www/, you can check default vhost for example.

Additionally, you can look at the error.log file (usually located at /var/log/apache2/error.log) which will describe why you get the 403 error exactly.

Finally, you may want to restart apache, just to be sure all that configuration is applied. This can be generally done with /etc/init.d/apache2 restart. On some system, the script will be called httpd. Just figure out.

java.sql.SQLException: Missing IN or OUT parameter at index:: 1

See the link below for information about how to use PreparedStatement. I have also quoted from the link.

You must supply values in place of the question mark placeholders (if there are any) before you can execute a PreparedStatement object. Do this by calling one of the setter methods defined in the PreparedStatement class. The following statements supply the two question mark placeholders in the PreparedStatement named updateSales:

updateSales.setInt(1, e.getValue().intValue()); updateSales.setString(2, e.getKey());

Step out of current function with GDB

You can use the finish command.

finish: Continue running until just after function in the selected stack frame returns. Print the returned value (if any). This command can be abbreviated as fin.

(See 5.2 Continuing and Stepping.)

How to use an existing database with an Android application

If you are having pre built data base than copy it in asset folder and create an new class as DataBaseHelper which implements SQLiteOpenHelper Than use following code:


import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DataBaseHelperClass extends SQLiteOpenHelper{
 //The Android's default system path of your application database.
private static String DB_PATH = "/data/data/package_name/databases/";
// Data Base Name.
private static final String DATABASE_NAME = "DBName.sqlite";
// Data Base Version.
private static final int DATABASE_VERSION = 1;
// Table Names of Data Base.
static final String TABLE_Name = "tableName";

public Context context;
static SQLiteDatabase sqliteDataBase;

 * Constructor
 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
 * @param context
 * Parameters of super() are    1. Context
 *                              2. Data Base Name.
 *                              3. Cursor Factory.
 *                              4. Data Base Version.
public DataBaseHelperClass(Context context) {       
    super(context, DATABASE_NAME, null ,DATABASE_VERSION);
    this.context = context;

 * Creates a empty database on the system and rewrites it with your own database.
 * By calling this method and empty database will be created into the default system path
 * of your application so we are gonna be able to overwrite that database with our database.
 * */
public void createDataBase() throws IOException{
    //check if the database exists
    boolean databaseExist = checkDataBase();

        // Do Nothing.
    }// end if else dbExist
} // end createDataBase().

 * Check if the database already exist to avoid re-copying the file each time you open the application.
 * @return true if it exists, false if it doesn't
public boolean checkDataBase(){
    File databaseFile = new File(DB_PATH + DATABASE_NAME);
    return databaseFile.exists();        

 * Copies your database from your local assets-folder to the just created empty database in the
 * system folder, from where it can be accessed and handled.
 * This is done by transferring byte stream.
 * */
private void copyDataBase() throws IOException{ 
    //Open your local db as the input stream
    InputStream myInput = context.getAssets().open(DATABASE_NAME); 
    // Path to the just created empty db
    String outFileName = DB_PATH + DATABASE_NAME; 
    //Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName); 
    //transfer bytes from the input file to the output file
    byte[] buffer = new byte[1024];
    int length;
    while ((length =>0){
        myOutput.write(buffer, 0, length);

    //Close the streams

 * This method opens the data base connection.
 * First it create the path up till data base of the device.
 * Then create connection with data base.
public void openDataBase() throws SQLException{      
    //Open the database
    String myPath = DB_PATH + DATABASE_NAME;
    sqliteDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);  

 * This Method is used to close the data base connection.
public synchronized void close() { 
    if(sqliteDataBase != null)

* Apply your methods and class to fetch data using raw or queries on data base using 
* following demo example code as:
public String getUserNameFromDB(){
    String query = "select User_First_Name From "+TABLE_USER_DETAILS;
    Cursor cursor = sqliteDataBase.rawQuery(query, null);
    String userName = null;
                userName = cursor.getString(0);
            }while (cursor.moveToNext());
    return userName;

public void onCreate(SQLiteDatabase db) {
    // No need to write the create table query.
    // As we are using Pre built data base.
    // Which is ReadOnly.

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // No need to write the update table query.
    // As we are using Pre built data base.
    // Which is ReadOnly.
    // We should not update it as requirements of application.

Hope this will help you...

What encoding/code page is cmd.exe using?

To answer your second query re. how encoding works, Joel Spolsky wrote a great introductory article on this. Strongly recommended.

file path Windows format to java format

Java 7 and up supports the Path class (in java.nio package). You can use this class to convert a string-path to one that works for your current OS.



on a Unix machine, will give you /folder/subfolder. Also works the other way around.

Compress files while reading data from STDIN

Yes, use gzip for this. The best way is to read data as input and redirect the compressed to output file i.e.

cat test.csv | gzip > test.csv.gz

cat test.csv will send the data as stdout and using pipe-sign gzip will read that data as stdin. Make sure to redirect the gzip output to some file as compressed data will not be written to the terminal.

Connect to SQL Server 2012 Database with C# (Visual Studio 2012)

I tested all the answers here, but for me, none worked. So I studied a bit the problem, and finally I found the connection string needed. To get this string, you do:
1. in you project name:
a. right click the project name,
b. click Add,
c. select SQL Server Database (obviously you can rename it as you wish).
Now the new desired database will be added to your project.
2. The database is visible in the Server Explorer window.
3. Left click the database name in the Server Explorer window; now check the Solution Explorer window, and you will find the "Connection String", along side with Provider, State, Type, Version.
4. Copy the connection string provided, and put it in the Page_Load method:

string source = @"Data Source=(LocalDB)\v11.0;AttachDbFilename=c:\x\x\documents\visual studio 2013\Projects\WebApplication3\WebApplication3\App_Data\Product.mdf;Integrated Security=True";
SqlConnection conn = new SqlConnection(source);
//your code here;

I renamed my database as Product. Also, in the "AttachDbFilename", you must replace "c:\x\x\documents\" with your path to the phisical address of the .mdf file.

It worked for me, but I must mention this method works for VS2012 and VS2013. Don't know about other versions.

Crystal Reports 13 And Asp.Net 3.5

I had faced the same issue because of some dll files were missing from References of VS13. I went to the location and installed the newest pack. It resolved the issue.

How to read a file line-by-line into a list?

I like to use the following. Reading the lines immediately.

contents = []
for line in open(filepath, 'r').readlines():

Or using list comprehension:

contents = [line.strip() for line in open(filepath, 'r').readlines()]

Entity Framework. Delete all rows in table

If you wish to clear your entire database.

Because of the foreign-key constraints it matters which sequence the tables are truncated. This is a way to bruteforce this sequence.

    public static void ClearDatabase<T>() where T : DbContext, new()
        using (var context = new T())
            var tableNames = context.Database.SqlQuery<string>("SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE' AND TABLE_NAME NOT LIKE '%Migration%'").ToList();
            foreach (var tableName in tableNames)
                foreach (var t in tableNames)

                        if (context.Database.ExecuteSqlCommand(string.Format("TRUNCATE TABLE [{0}]", tableName)) == 1)

                    catch (Exception ex)





remember to reinstantiate your DbContext after this.

Extracting extension from filename in Python

import os.path
extension = os.path.splitext(filename)[1]

TypeError: 'float' object not iterable

for i in count: means for i in 7:, which won't work. The bit after the in should be of an iterable type, not a number. Try this:

for i in range(count):

Add quotation at the start and end of each line in Notepad++

  • Place your cursor at the end of the text.
  • Press SHIFT and ->. The cursor will move to the next line.
  • Press CTRL-F and type , in "Replace with:" and press ENTER.

You will need to put a quote at the beginning of your first text and the end of your last.

Flask Python Buttons

The appropriate way for doing this:

def index():
    if form.validate_on_submit():
        if 'download' in request.form:
            pass # do something
        elif 'watch' in request.form:
            pass # do something else

Put watch and download buttons into your template:

<input type="submit" name="download" value="Download">
<input type="submit" name="watch" value="Watch">

How do I change the title of the "back" button on a Navigation Bar

Maybe I'm being over simplistic but From Apple's documentation the wording is:

If a custom bar button item is not specified by either of the view controllers, a default back button is used and its title is set to the value of the title property of the previous view controller—that is, the view controller one level down on the stack.

The solution marked correct above sets a default button item from the parent controller. It's the right answer, but I'm solving the issue by changing self.title property of the UIViewController right before pushing the new controller onto the NavigationController stack.

This automatically updates the back button's title on the next controller, and as long as you set self.title back to what it should be in viewWillAppear I can't see this method causing too many problems.

How to print a query string with parameter values when using Hibernate

Just for convenience, here is the same configuration example for Logback (SLF4J)

<appender name="SQLROLLINGFILE">
  <Pattern>%-4date | %msg %n</Pattern>

<logger name="org.hibernate.SQL" additivity="false" >   
 <level value="DEBUG" />    
 <appender-ref ref="SQLROLLINGFILE" />

<logger name="org.hibernate.type" additivity="false" >
 <level value="TRACE" />
 <appender-ref ref="SQLROLLINGFILE" />

The output in your sql.log (example) then looks like this:

2013-08-30 18:01:15,083 | update stepprovider set created_at=?, lastupdated_at=?, version=?, bundlelocation=?, category_id=?, customer_id=?, description=?, icon_file_id=?, name=?, shareStatus=?, spversion=?, status=?, title=?, type=?, num_used=? where id=?
2013-08-30 18:01:15,084 | binding parameter [1] as [TIMESTAMP] - 2012-07-11 09:57:32.0
2013-08-30 18:01:15,085 | binding parameter [2] as [TIMESTAMP] - Fri Aug 30 18:01:15 CEST 2013
2013-08-30 18:01:15,086 | binding parameter [3] as [INTEGER] -
2013-08-30 18:01:15,086 | binding parameter [4] as [VARCHAR] -
2013-08-30 18:01:15,087 | binding parameter [5] as [VARCHAR] -
2013-08-30 18:01:15,087 | binding parameter [6] as [VARCHAR] -
2013-08-30 18:01:15,087 | binding parameter [7] as [VARCHAR] - TODO
2013-08-30 18:01:15,087 | binding parameter [8] as [VARCHAR] -
2013-08-30 18:01:15,088 | binding parameter [9] as [VARCHAR] - [email protected]
2013-08-30 18:01:15,088 | binding parameter [10] as [VARCHAR] - PRIVATE
2013-08-30 18:01:15,088 | binding parameter [11] as [VARCHAR] - 1.0
2013-08-30 18:01:15,088 | binding parameter [12] as [VARCHAR] - 32
2013-08-30 18:01:15,088 | binding parameter [13] as [VARCHAR] - MatchingStep
2013-08-30 18:01:15,089 | binding parameter [14] as [VARCHAR] -
2013-08-30 18:01:15,089 | binding parameter [15] as [INTEGER] - 0
2013-08-30 18:01:15,089 | binding parameter [16] as [VARCHAR] - 053c2e65-5d51-4c09-85f3-2281a1024f64

How to handle iframe in Selenium WebDriver using java

Selenium Web Driver Handling Frames
It is impossible to click iframe directly through XPath since it is an iframe. First we have to switch to the frame and then we can click using xpath.

driver.switchTo().frame() has multiple overloads.

  1. driver.switchTo().frame(name_or_id)
    Here your iframe doesn't have id or name, so not for you.

  2. driver.switchTo().frame(index)
    This is the last option to choose, because using index is not stable enough as you could imagine. If this is your only iframe in the page, try driver.switchTo().frame(0)

  3. driver.switchTo().frame(iframe_element)
    The most common one. You locate your iframe like other elements, then pass it into the method.

driver.switchTo().defaultContent(); [parentFrame, defaultContent, frame]

// Based on index position:
int frameIndex = 0;
List<WebElement> listFrames = driver.findElements(By.tagName("iframe"));
System.out.println("list frames   "+listFrames.size());
driver.switchTo().frame(listFrames.get( frameIndex ));

// XPath|CssPath Element:
WebElement frameCSSPath = driver.findElement(By.cssSelector("iframe[title='Fill Quote']"));
WebElement frameXPath = driver.findElement(By.xpath(".//iframe[1]"));
WebElement frameTag = driver.findElement(By.tagName("iframe"));

driver.switchTo().frame( frameCSSPath ); // frameXPath, frameTag

driver.switchTo().frame("relative=up"); // focus to parent frame.
driver.switchTo().defaultContent(); // move to the most parent or main frame

// For alert's
Alert alert = driver.switchTo().alert(); // Switch to alert pop-up

XML Test:

    <IFame id='1'>...       parentFrame() « context remains unchanged. <IFame1>
     -> <IFrame id='2'>...  parentFrame() « Change focus to the parent context. <IFame1>

<frameset cols="50%,50%">
    <Fame id='11'>...     defaultContent() « driver focus to top window/first frame. <html>
     -> <Frame id='22'>... defaultContent() « driver focus to top window/first frame. <Fame11> 
                           frame("relative=up") « focus to parent frame. <Fame11>

Conversion of RC to Web-Driver Java commands. link.

<frame> is an HTML element which defines a particular area in which another HTML document can be displayed. A frame should be used within a <frameset>. « Deprecated. Not for use in new websites.

Error when trying vagrant up

Please run this in your terminal:

$ vagrant box list

You will see something like laravel/homestead(virtualbox,x.x.x)

Next locate your Vagrantfile and locate the line that says = "box"

replace box with the box name when you run vagrant box list.

Install IPA with iTunes 12

For iTunes and above you can install the apps by Copying the IPA file and Paste it (Cmd+V or Edit -> Paste in iTunes) in any categories as Music/Films/TV Programmes etc. The app will be installed automatically on your iPhone screen.

Tested on 29 Nov 2019.

Demo: enter image description here

Meaning of "n:m" and "1:n" in database design

1:n means 'one-to-many'; you have two tables, and each row of table A may be referenced by any number of rows in table B, but each row in table B can only reference one row in table A (or none at all).

n:m (or n:n) means 'many-to-many'; each row in table A can reference many rows in table B, and each row in table B can reference many rows in table A.

A 1:n relationship is typically modelled using a simple foreign key - one column in table A references a similar column in table B, typically the primary key. Since the primary key uniquely identifies exactly one row, this row can be referenced by many rows in table A, but each row in table A can only reference one row in table B.

A n:m relationship cannot be done this way; a common solution is to use a link table that contains two foreign key columns, one for each table it links. For each reference between table A and table B, one row is inserted into the link table, containing the IDs of the corresponding rows.

Importing data from a JSON file into R

First install the rjson package:



json_file <- ""
json_data <- fromJSON(paste(readLines(json_file), collapse=""))

Update: since version 0.2.1

json_data <- fromJSON(file=json_file)

Get the generated SQL statement from a SqlCommand object?

If you're using SQL Server, you could use SQL Server Profiler (if you have it) to view the command string that is actually executed. That would be useful for copy/paste testing purpuses but not for logging I'm afraid.

The service cannot be started, either because it is disabled or because it has no enabled devices associated with it

This error can occur on anything that requires elevated privileges in Windows.

It happens when the "Application Information" service is disabled in Windows services. There are a few viruses that use this as an attack vector to prevent people from removing the virus. It also prevents people from installing software to remove viruses.

The normal way to fix this would be to run services.msc, or to go into Administrative Tools and run "Services". However, you will not be able to do that if the "Application Information" service is disabled.

Instead, reboot your computer into Safe Mode (reboot and press F8 until the Windows boot menu appears, select Safe Mode with Networking). Then run services.msc and look for services that are designated as "Disabled" in the Startup Type column. Change these "Disabled" services to "Automatic".

Make sure the "Application Information" service is set to a Startup Type of "Automatic".

When you are done enabling your services, click Ok at the bottom of the tool and reboot your computer back into normal mode. The problem should be resolved when Windows reboots.

What is the difference between UNION and UNION ALL?

I add an example,

UNION, it is merging with distinct --> slower, because it need comparing (In Oracle SQL developer, choose query, press F10 to see cost analysis).

UNION ALL, it is merging without distinct --> faster.

SELECT to_date(sysdate, 'yyyy-mm-dd') FROM dual
SELECT to_date(sysdate, 'yyyy-mm-dd') FROM dual;


SELECT to_date(sysdate, 'yyyy-mm-dd') FROM dual
SELECT to_date(sysdate, 'yyyy-mm-dd') FROM dual;

How can I get just the first row in a result set AFTER ordering?

This question is similar to How do I limit the number of rows returned by an Oracle query after ordering?.

It talks about how to implement a MySQL limit on an oracle database which judging by your tags and post is what you are using.

The relevant section is:

select *
  ( select * 
  from emp 
  order by sal desc ) 
  where ROWNUM <= 5;

Gets byte array from a ByteBuffer in java

Note that the bb.array() doesn't honor the byte-buffers position, and might be even worse if the bytebuffer you are working on is a slice of some other buffer.


byte[] test = "Hello World".getBytes("Latin1");
ByteBuffer b1 = ByteBuffer.wrap(test);
byte[] hello = new byte[6];
b1.get(hello); // "Hello "
ByteBuffer b2 = b1.slice(); // position = 0, string = "World"
byte[] tooLong = b2.array(); // Will NOT be "World", but will be "Hello World".
byte[] world = new byte[5];
b2.get(world); // world = "World"

Which might not be what you intend to do.

If you really do not want to copy the byte-array, a work-around could be to use the byte-buffer's arrayOffset() + remaining(), but this only works if the application supports index+length of the byte-buffers it needs.

Get Month name from month number

You can get this in following way,

DateTimeFormatInfo mfi = new DateTimeFormatInfo();
string strMonthName = mfi.GetMonthName(8).ToString(); //August

Now, get first three characters

string shortMonthName = strMonthName.Substring(0, 3); //Aug

Access elements of parent window from iframe

I think you can just use window.parent from the iframe. window.parent returns the window object of the parent page, so you could do something like:


Then do whatever you want with that div.

Javascript set img src

Instances of the image constructor are not meant to be used anywhere. You simply set the src, and the image preloads...and that's it, show's over. You can discard the object and move on.

document["pic1"].src = "XXXX/YYYY/search.png"; 

is what you should be doing. You can still use the image constructor, and perform the second action in the onload handler of your searchPic. This ensures the image is loaded before you set the src on the real img object.

Like so:

function LoadImages() {
    searchPic = new Image();
    searchPic.onload=function () {
        document["pic1"].src = "XXXX/YYYY/search.png";
    searchPic.src = "XXXX/YYYY/search.png"; // This is correct and the path is correct

Python object.__repr__(self) should be an expression?

"but does that mean it should just be an example of the sort of expression you could use, or should it be an actual expression, that can be executed (eval etc..) to recreate the object? Or... should it be just a rehasing of the actual expression which was used, for pure information purposes?"

Wow, that's a lot of hand-wringing.

  1. An "an example of the sort of expression you could use" would not be a representation of a specific object. That can't be useful or meaningful.

  2. What is the difference between "an actual expression, that can ... recreate the object" and "a rehasing of the actual expression which was used [to create the object]"? Both are an expression that creates the object. There's no practical distinction between these. A repr call could produce either a new expression or the original expression. In many cases, they're the same.

Note that this isn't always possible, practical or desirable.

In some cases, you'll notice that repr() presents a string which is clearly not an expression of any kind. The default repr() for any class you define isn't useful as an expression.

In some cases, you might have mutual (or circular) references between objects. The repr() of that tangled hierarchy can't make sense.

In many cases, an object is built incrementally via a parser. For example, from XML or JSON or something. What would the repr be? The original XML or JSON? Clearly not, since they're not Python. It could be some Python expression that generated the XML. However, for a gigantic XML document, it might not be possible to write a single Python expression that was the functional equivalent of parsing XML.

jQuery pass more parameters into callback

When using doSomething(data, myDiv), you actually call the function and do not make a reference to it.

You can either pass the doStomething function directly but you must ensure it has the correct signature.

If you want to keep doSomething the way it is, you can wrap its call in an anonymous function.

function clicked() {
    var myDiv = $("#my-div");
    $.post("someurl.php",someData, function(data){ 
      doSomething(data, myDiv)

function doSomething(curData, curDiv) {

Inside the anonymous function code, you can use the variables defined in the enclosing scope. This is the way Javascript scoping works.

How to atomically delete keys matching a pattern using Redis

I tried most of methods mentioned above but they didn't work for me, after some searches I found these points:

  • if you have more than one db on redis you should determine the database using -n [number]
  • if you have a few keys use del but if there are thousands or millions of keys it's better to use unlink because unlink is non-blocking while del is blocking, for more information visit this page unlink vs del
  • also keys are like del and is blocking

so I used this code to delete keys by pattern:

 redis-cli -n 2 --scan --pattern '[your pattern]' | xargs redis-cli -n 2 unlink 

Find elements inside forms and iframe using Java and Selenium WebDriver

When using an iframe, you will first have to switch to the iframe, before selecting the elements of that iframe

You can do it using:

//do your stuff

In case if your frameId is dynamic, and you only have one iframe, you can use something like:


Best way to pass parameters to jQuery's .load()

In the first case, the data are passed to the script via GET, in the second via POST.

I don't think there are limits to the data size, but the completition of the remote call will of course take longer with great amount of data.

SQL how to make null values come last when sorting ascending

If your engine allows ORDER BY x IS NULL, x or ORDER BY x NULLS LAST use that. But if it doesn't these might help:

If you're sorting by a numeric type you can do this: (Borrowing the schema from another answer.)

SELECT *          
FROM Employees
ORDER BY ISNULL(DepartmentId*0,1), DepartmentId;

result showing sorted by DepartmentId with nulls last

Any non-null number becomes 0, and nulls become 1, which sorts nulls last because 0 < 1.

You can also do this for strings:

FROM Employees
ORDER BY ISNULL(LEFT(LastName,0),'a'), LastName

result showing sorted by LastName with nulls last

Any non-null string becomes '', and nulls become 'a', which sorts nulls last because '' < 'a'.

This even works with dates by coercing to a nullable int and using the method for ints above:

FROM Employees
ORDER BY ISNULL(CONVERT(INT, HireDate)*0, 1), HireDate

(Lets pretend the schema has HireDate.)

These methods avoid the issue of having to come up with or manage a "maximum" value of every type or fix queries if the data type (and the maximum) changes (both issues that other ISNULL solutions suffer). Plus they're much shorter than a CASE.

Efficiently convert rows to columns in sql server

This is rather a method than just a single script but gives you much more flexibility.

First of all There are 3 objects:

  1. User defined TABLE type [ColumnActionList] -> holds data as parameter
  2. SP [proc_PivotPrepare] -> prepares our data
  3. SP [proc_PivotExecute] -> execute the script

CREATE TYPE [dbo].[ColumnActionList] AS TABLE ( [ID] [smallint] NOT NULL, [ColumnName] nvarchar NOT NULL, [Action] nchar NOT NULL ); GO

    CREATE PROCEDURE [dbo].[proc_PivotPrepare] 
    @DB_Name        nvarchar(128),
    @TableName      nvarchar(128)
            SELECT @DB_Name = ISNULL(@DB_Name,db_name())
    DECLARE @SQL_Code nvarchar(max)

    DECLARE @MyTab TABLE (ID smallint identity(1,1), [Column_Name] nvarchar(128), [Type] nchar(1), [Set Action SQL] nvarchar(max));

    SELECT @SQL_Code        =   'SELECT [<| SQL_Code |>] = '' '' '
                                        + 'UNION ALL '
                                        + 'SELECT ''----------------------------------------------------------------------------------------------------'' '
                                        + 'UNION ALL '
                                        + 'SELECT ''-----| Declare user defined type [ID] / [ColumnName] / [PivotAction] '' '
                                        + 'UNION ALL '
                                        + 'SELECT ''----------------------------------------------------------------------------------------------------'' '
                                        + 'UNION ALL '
                                        + 'SELECT ''DECLARE @ColumnListWithActions ColumnActionList;'''
                                        + 'UNION ALL '
                                        + 'SELECT ''----------------------------------------------------------------------------------------------------'' '
                                        + 'UNION ALL '
                                        + 'SELECT ''-----| Set [PivotAction] (''''S'''' as default) to select dimentions and values '' '
                                        + 'UNION ALL '
                                        + 'SELECT ''-----|'''
                                        + 'UNION ALL '
                                        + 'SELECT ''-----| ''''S'''' = Stable column || ''''D'''' = Dimention column || ''''V'''' = Value column '' '
                                        + 'UNION ALL '
                                        + 'SELECT ''----------------------------------------------------------------------------------------------------'' '
                                        + 'UNION ALL '
                                        + 'SELECT ''INSERT INTO  @ColumnListWithActions VALUES ('' + CAST( ROW_NUMBER() OVER (ORDER BY [NAME]) as nvarchar(10)) + '', '' + '''''''' + [NAME] + ''''''''+ '', ''''S'''');'''
                                        + 'FROM [' + @DB_Name + '].sys.columns  '
                                        + 'WHERE object_id = object_id(''[' + @DB_Name + ']..[' + @TableName + ']'') '
                                        + 'UNION ALL '
                                        + 'SELECT ''----------------------------------------------------------------------------------------------------'' '
                                        + 'UNION ALL '
                                        + 'SELECT ''-----| Execute sp_PivotExecute with parameters: columns and dimentions and main table name'' '
                                        + 'UNION ALL '
                                        + 'SELECT ''----------------------------------------------------------------------------------------------------'' '
                                        + 'UNION ALL '
                                        + 'SELECT ''EXEC [dbo].[sp_PivotExecute] @ColumnListWithActions, ' + '''''' + @TableName + '''''' + ';'''
                                        + 'UNION ALL '
                                        + 'SELECT ''----------------------------------------------------------------------------------------------------'' '                            


CREATE PROCEDURE [dbo].[sp_PivotExecute]
@ColumnListWithActions  ColumnActionList ReadOnly
,@TableName                     nvarchar(128)

--###| Step 1 - Select our user-defined-table-variable into temp table

IF OBJECT_ID('tempdb.dbo.#ColumnListWithActions', 'U') IS NOT NULL DROP TABLE #ColumnListWithActions; 
SELECT * INTO #ColumnListWithActions FROM @ColumnListWithActions;

--###| Step 2 - Preparing lists of column groups as strings:

DECLARE @ColumnName                     nvarchar(128)
DECLARE @Destiny                        nchar(1)

DECLARE @ListOfColumns_Stable           nvarchar(max)
DECLARE @ListOfColumns_Dimension    nvarchar(max)
DECLARE @ListOfColumns_Variable     nvarchar(max)
--###| Cursor for List of Stable Columns

DECLARE ColumnListStringCreator_S CURSOR FOR
SELECT      [ColumnName]
FROM        #ColumnListWithActions
WHERE       [Action] = 'S'
OPEN ColumnListStringCreator_S;
FETCH NEXT FROM ColumnListStringCreator_S
INTO @ColumnName

        SELECT @ListOfColumns_Stable = ISNULL(@ListOfColumns_Stable, '') + ' [' + @ColumnName + '] ,';
        FETCH NEXT FROM ColumnListStringCreator_S INTO @ColumnName

CLOSE ColumnListStringCreator_S;
DEALLOCATE ColumnListStringCreator_S;

--###| Cursor for List of Dimension Columns

DECLARE ColumnListStringCreator_D CURSOR FOR
SELECT      [ColumnName]
FROM        #ColumnListWithActions
WHERE       [Action] = 'D'
OPEN ColumnListStringCreator_D;
FETCH NEXT FROM ColumnListStringCreator_D
INTO @ColumnName

        SELECT @ListOfColumns_Dimension = ISNULL(@ListOfColumns_Dimension, '') + ' [' + @ColumnName + '] ,';
        FETCH NEXT FROM ColumnListStringCreator_D INTO @ColumnName

CLOSE ColumnListStringCreator_D;
DEALLOCATE ColumnListStringCreator_D;

--###| Cursor for List of Variable Columns

DECLARE ColumnListStringCreator_V CURSOR FOR
SELECT      [ColumnName]
FROM        #ColumnListWithActions
WHERE       [Action] = 'V'
OPEN ColumnListStringCreator_V;
FETCH NEXT FROM ColumnListStringCreator_V
INTO @ColumnName

        SELECT @ListOfColumns_Variable = ISNULL(@ListOfColumns_Variable, '') + ' [' + @ColumnName + '] ,';
        FETCH NEXT FROM ColumnListStringCreator_V INTO @ColumnName

CLOSE ColumnListStringCreator_V;
DEALLOCATE ColumnListStringCreator_V;

SELECT @ListOfColumns_Variable      = LEFT(@ListOfColumns_Variable, LEN(@ListOfColumns_Variable) - 1);
SELECT @ListOfColumns_Dimension = LEFT(@ListOfColumns_Dimension, LEN(@ListOfColumns_Dimension) - 1);
SELECT @ListOfColumns_Stable            = LEFT(@ListOfColumns_Stable, LEN(@ListOfColumns_Stable) - 1);

--###| Step 3 - Preparing table with all possible connections between Dimension columns excluding NULLs
DECLARE @DIM_TAB TABLE ([DIM_ID] smallint, [ColumnName] nvarchar(128))
SELECT [DIM_ID] = ROW_NUMBER() OVER(ORDER BY [ColumnName]), [ColumnName] FROM #ColumnListWithActions WHERE [Action] = 'D';

DECLARE @DIM_ID smallint;
SELECT      @DIM_ID = 1;

DECLARE @SQL_Dimentions nvarchar(max);

IF OBJECT_ID('tempdb.dbo.##ALL_Dimentions', 'U') IS NOT NULL DROP TABLE ##ALL_Dimentions; 

SELECT @SQL_Dimentions      = 'SELECT [xxx_ID_xxx] = ROW_NUMBER() OVER (ORDER BY ' + @ListOfColumns_Dimension + '), ' + @ListOfColumns_Dimension
                                            + ' INTO ##ALL_Dimentions '
                                            + ' FROM (SELECT DISTINCT' + @ListOfColumns_Dimension + ' FROM  ' + @TableName
                                            + ' WHERE ' + (SELECT [ColumnName] FROM @DIM_TAB WHERE [DIM_ID] = @DIM_ID) + ' IS NOT NULL ';
                                            SELECT @DIM_ID = @DIM_ID + 1;
            SELECT @SQL_Dimentions = @SQL_Dimentions + 'AND ' + (SELECT [ColumnName] FROM @DIM_TAB WHERE [DIM_ID] = @DIM_ID) +  ' IS NOT NULL ';
            SELECT @DIM_ID = @DIM_ID + 1;

SELECT @SQL_Dimentions   = @SQL_Dimentions + ' )x';


--###| Step 4 - Preparing table with all possible connections between Stable columns excluding NULLs
DECLARE @StabPos_TAB TABLE ([StabPos_ID] smallint, [ColumnName] nvarchar(128))
SELECT [StabPos_ID] = ROW_NUMBER() OVER(ORDER BY [ColumnName]), [ColumnName] FROM #ColumnListWithActions WHERE [Action] = 'S';

DECLARE @StabPos_ID smallint;
SELECT      @StabPos_ID = 1;

DECLARE @SQL_MainStableColumnTable nvarchar(max);

IF OBJECT_ID('tempdb.dbo.##ALL_StableColumns', 'U') IS NOT NULL DROP TABLE ##ALL_StableColumns; 

SELECT @SQL_MainStableColumnTable       = 'SELECT xxx_ID_xxx = ROW_NUMBER() OVER (ORDER BY ' + @ListOfColumns_Stable + '), ' + @ListOfColumns_Stable
                                            + ' INTO ##ALL_StableColumns '
                                            + ' FROM (SELECT DISTINCT' + @ListOfColumns_Stable + ' FROM  ' + @TableName
                                            + ' WHERE ' + (SELECT [ColumnName] FROM @StabPos_TAB WHERE [StabPos_ID] = @StabPos_ID) + ' IS NOT NULL ';
                                            SELECT @StabPos_ID = @StabPos_ID + 1;
            WHILE @StabPos_ID <= (SELECT MAX([StabPos_ID]) FROM @StabPos_TAB)
            SELECT @SQL_MainStableColumnTable = @SQL_MainStableColumnTable + 'AND ' + (SELECT [ColumnName] FROM @StabPos_TAB WHERE [StabPos_ID] = @StabPos_ID) +  ' IS NOT NULL ';
            SELECT @StabPos_ID = @StabPos_ID + 1;

SELECT @SQL_MainStableColumnTable    = @SQL_MainStableColumnTable + ' )x';


--###| Step 5 - Preparing table with all options ID


DECLARE @i smallint

IF OBJECT_ID('tempdb.dbo.##FinalTab', 'U') IS NOT NULL DROP TABLE ##FinalTab; 

SELECT @FULL_SQL_1 = 'SELECT t.*, dim.[xxx_ID_xxx] '
                                    + ' INTO ##FinalTab '
                                    +   'FROM ' + @TableName + ' t '
                                    +   'JOIN ##ALL_Dimentions dim '
                                    +   'ON t.' + (SELECT [ColumnName] FROM @DIM_TAB WHERE [DIM_ID] = 1) + ' = dim.' + (SELECT [ColumnName] FROM @DIM_TAB WHERE [DIM_ID] = 1);
                                SELECT @i = 2                               
                                WHILE @i <= (SELECT MAX([DIM_ID]) FROM @DIM_TAB)
                                    SELECT @FULL_SQL_1 = @FULL_SQL_1 + ' AND t.' + (SELECT [ColumnName] FROM @DIM_TAB WHERE [DIM_ID] = @i) + ' = dim.' + (SELECT [ColumnName] FROM @DIM_TAB WHERE [DIM_ID] = @i)
                                    SELECT @i = @i +1

--###| Step 6 - Selecting final data
DECLARE @STAB_TAB TABLE ([STAB_ID] smallint, [ColumnName] nvarchar(128))
SELECT [STAB_ID] = ROW_NUMBER() OVER(ORDER BY [ColumnName]), [ColumnName]
FROM #ColumnListWithActions WHERE [Action] = 'S';

DECLARE @VAR_TAB TABLE ([VAR_ID] smallint, [ColumnName] nvarchar(128))
SELECT [VAR_ID] = ROW_NUMBER() OVER(ORDER BY [ColumnName]), [ColumnName]
FROM #ColumnListWithActions WHERE [Action] = 'V';

DECLARE @y smallint;
DECLARE @x smallint;
DECLARE @z smallint;

DECLARE @FinalCode nvarchar(max)

SELECT @FinalCode = ' SELECT ID1.*'
                                        SELECT @y = 1
                                        WHILE @y <= (SELECT MAX([xxx_ID_xxx]) FROM ##FinalTab)
                                                SELECT @z = 1
                                                WHILE @z <= (SELECT MAX([VAR_ID]) FROM @VAR_TAB)
                                                        SELECT @FinalCode = @FinalCode +    ', [ID' + CAST((@y) as varchar(10)) + '.' + (SELECT [ColumnName] FROM @VAR_TAB WHERE [VAR_ID] = @z) + '] =  ID' + CAST((@y + 1) as varchar(10)) + '.' + (SELECT [ColumnName] FROM @VAR_TAB WHERE [VAR_ID] = @z)
                                                        SELECT @z = @z + 1
                                                    SELECT @y = @y + 1
        SELECT @FinalCode = @FinalCode + 
                                        ' FROM ( SELECT * FROM ##ALL_StableColumns)ID1';
                                        SELECT @y = 1
                                        WHILE @y <= (SELECT MAX([xxx_ID_xxx]) FROM ##FinalTab)
                                            SELECT @x = 1
                                            SELECT @FinalCode = @FinalCode 
                                                                                + ' LEFT JOIN (SELECT ' +  @ListOfColumns_Stable + ' , ' + @ListOfColumns_Variable 
                                                                                + ' FROM ##FinalTab WHERE [xxx_ID_xxx] = ' 
                                                                                + CAST(@y as varchar(10)) + ' )ID' + CAST((@y + 1) as varchar(10))  
                                                                                + ' ON 1 = 1' 
                                                                                WHILE @x <= (SELECT MAX([STAB_ID]) FROM @STAB_TAB)
                                                                                    SELECT @FinalCode = @FinalCode + ' AND ID1.' + (SELECT [ColumnName] FROM @STAB_TAB WHERE [STAB_ID] = @x) + ' = ID' + CAST((@y+1) as varchar(10)) + '.' + (SELECT [ColumnName] FROM @STAB_TAB WHERE [STAB_ID] = @x)
                                                                                    SELECT @x = @x +1
                                            SELECT @y = @y + 1

SELECT * FROM ##ALL_Dimentions;

From executing the first query (by passing source DB and table name) you will get a pre-created execution query for the second SP, all you have to do is define is the column from your source: + Stable + Value (will be used to concentrate values based on that) + Dim (column you want to use to pivot by)

Names and datatypes will be defined automatically!

I cant recommend it for any production environments but does the job for adhoc BI requests.

How to check if an object implements an interface?

If you want a method like public void doSomething([Object implements Serializable]) you can just type it like this public void doSomething(Serializable serializableObject). You can now pass it any object that implements Serializable but using the serializableObject you only have access to the methods implemented in the object from the Serializable interface.

Are complex expressions possible in ng-hide / ng-show?

Some of these above answers didn't work for me but this did. Just in case someone else has the same issue.

ng-show="column != 'vendorid' && column !='billingMonth'"

What is a deadlock?

You can take a look at this wonderful articles, under section Deadlock. It is in C# but the idea is still the same for other platform. I quote here for easy reading

A deadlock happens when two threads each wait for a resource held by the other, so neither can proceed. The easiest way to illustrate this is with two locks:

object locker1 = new object();
object locker2 = new object();

new Thread (() => {
                    lock (locker1)
                      Thread.Sleep (1000);
                      lock (locker2);      // Deadlock
lock (locker2)
  Thread.Sleep (1000);
  lock (locker1);                          // Deadlock

Multiple conditions in an IF statement in Excel VBA

In VBA we can not use if jj = 5 or 6 then we must use if jj = 5 or jj = 6 then

maybe this:

If inputWks.Range("d9") > 0 And (inputWks.Range("d11") = "Restricted_Expenditure" Or inputWks.Range("d11") = "Unrestricted_Expenditure") Then

java.lang.NoClassDefFoundError: Could not initialize class XXX

I encounter the same problem. I inited a bean object in static block like below:

static {
        mqttConfiguration = SpringBootBeanUtils.<MqttConfiguration>getBean(MqttConfiguration.class);
    }catch (Throwable e){

Just because the process the my bean obejct inition caused a NPE, I get trouble into it. So I think you should check you static code block carefully.

Regex to match string containing two names in any order

Its short and sweet


Test Cases:

  "xxx james xxx jack xxx",
  "jack xxx james ",
  "jack xxx jam ",
  "  jam and jack",
.forEach(s => console.log(/(?=.*james)(?=.*jack)/.test(s)) )

What's the difference between `raw_input()` and `input()` in Python 3?

The difference is that raw_input() does not exist in Python 3.x, while input() does. Actually, the old raw_input() has been renamed to input(), and the old input() is gone, but can easily be simulated by using eval(input()). (Remember that eval() is evil. Try to use safer ways of parsing your input if possible.)

Check if the number is integer

Another alternative is to check the fractional part:


or, if you want to check within a certain tolerance:

min(abs(c(x%%1, x%%1-1))) < tol

Angular 6: saving data to local storage

You should define a key name while storing data to local storage which should be a string and value should be a string

 localStorage.setItem('dataSource', this.dataSource.length);

and to print, you should use getItem


Check if checkbox is checked with jQuery

Toggle checkbox checked

    $("input:checkbox").prop( 'checked',$(this).is(":checked") );

How to sort a file in-place

No answers about few files, so:

sort -u file1 file2 -o file1

Android; Check if file exists without creating a new one

When you say "in you package folder," do you mean your local app files? If so you can get a list of them using the Context.fileList() method. Just iterate through and look for your file. That's assuming you saved the original file with Context.openFileOutput().

Sample code (in an Activity):

public void onCreate(...) {
    String[] files = fileList();
    for (String file : files) {
        if (file.equals(myFileName)) {
            //file exits

Arduino Nano - "avrdude: ser_open():system can't open device "\\.\COM1": the system cannot find the file specified"

This is how I solved the problem. In Device Manager you will find the Arduino COM port.

Enter image description here

Go to the Advanced properties of the port

Enter image description here

Set the COM port number to COM1.

Enter image description here

Then replug the USB.

Read JSON data in a shell script


$ cat /tmp/so.json | underscore select '.Messages .Body' 

Javascript CLI tools

You can use Javascript CLI tools like


Select all name children of a addons:

underscore select ".addons > .name"

The underscore-cli provide others real world examples as well as the json:select() doc.

@Html.DropDownListFor how to set default value

Like this:

@Html.DropDownListFor(model => model.Status, new List<SelectListItem> 
       { new SelectListItem{Text="Active", Value="True"},
         new SelectListItem{Text="Deactive", Value="False"}},"Select One")

If you want Active to be selected by default then use Selected property of SelectListItem:

@Html.DropDownListFor(model => model.Status, new List<SelectListItem> 
           { new SelectListItem{Text="Active", Value="True",Selected=true},
             new SelectListItem{Text="Deactive", Value="False"}},"Select One")

If using SelectList, then you have to use this overload and specify SelectListItem Value property which you want to set selected:

@Html.DropDownListFor(model => model.title, 
                     new SelectList(new List<SelectListItem>
      new SelectListItem { Text = "Active" , Value = "True"},
      new SelectListItem { Text = "InActive", Value = "False" }
    "Value", // property to be set as Value of dropdown item
    "Text",  // property to be used as text of dropdown item
    "True"), // value that should be set selected of dropdown
     new { @class = "form-control" })

Add two textbox values and display the sum in a third textbox automatically

well I think the problem solved this below code works:

function sum() {
    var result=0;
       var txtFirstNumberValue = document.getElementById('txt1').value;
       var txtSecondNumberValue = document.getElementById('txt2').value;
    if (txtFirstNumberValue !="" && txtSecondNumberValue ==""){
        result = parseInt(txtFirstNumberValue);
    }else if(txtFirstNumberValue == "" && txtSecondNumberValue != ""){
        result= parseInt(txtSecondNumberValue);
    }else if (txtSecondNumberValue != "" && txtFirstNumberValue != ""){
        result = parseInt(txtFirstNumberValue) + parseInt(txtSecondNumberValue);
       if (!isNaN(result)) {
           document.getElementById('txt3').value = result;

Android load from URL to Bitmap

I Prefer these one:

Creates Bitmap from InputStream and returns it:

    public static  Bitmap downloadImage(String url) {
        Bitmap bitmap = null;
        InputStream stream = null;
        BitmapFactory.Options bmOptions = new BitmapFactory.Options();
        bmOptions.inSampleSize = 1;

        try {
            stream = getHttpConnection(url);
            bitmap = BitmapFactory.decodeStream(stream, null, bmOptions);
        catch (IOException e1) {
            System.out.println("downloadImage"+ e1.toString());
        return bitmap;

  // Makes HttpURLConnection and returns InputStream

 public static  InputStream getHttpConnection(String urlString)  throws IOException {

        InputStream stream = null;
        URL url = new URL(urlString);
        URLConnection connection = url.openConnection();

        try {
            HttpURLConnection httpConnection = (HttpURLConnection) connection;

            if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                stream = httpConnection.getInputStream();
        catch (Exception ex) {
            System.out.println("downloadImage" + ex.toString());
        return stream;


Android includes two HTTP clients: HttpURLConnection and Apache HTTP Client. For Gingerbread and later, HttpURLConnection is the best choice.

From Android 3.x Honeycomb or later, you cannot perform Network IO on the UI thread and doing this throws android.os.NetworkOnMainThreadException. You must use Asynctask instead as shown below

/**     AsyncTAsk for Image Bitmap  */
    private class AsyncGettingBitmapFromUrl extends AsyncTask<String, Void, Bitmap> {

        protected Bitmap doInBackground(String... params) {


            Bitmap bitmap = null;

            bitmap = AppMethods.downloadImage(params[0]);

            return bitmap;

        protected void onPostExecute(Bitmap bitmap) {

            System.out.println("bitmap" + bitmap);


Primitive type 'short' - casting in Java

Java always uses at least 32 bit values for calculations. This is due to the 32-bit architecture which was common 1995 when java was introduced. The register size in the CPU was 32 bit and the arithmetic logic unit accepted 2 numbers of the length of a cpu register. So the cpus were optimized for such values.

This is the reason why all datatypes which support arithmetic opperations and have less than 32-bits are converted to int (32 bit) as soon as you use them for calculations.

So to sum up it mainly was due to performance issues and is kept nowadays for compatibility.

npm - "Can't find Python executable "python", you can set the PYTHON env variable."

I installed python2.7 to solve this issue. I wish can help you.

Test for multiple cases in a switch, like an OR (||)

Since the other answers explained how to do it without actually explaining why it works:

When the switch executes, it finds the first matching case statement and then executes each line of code after the switch until it hits either a break statement or the end of the switch (or a return statement to leave the entire containing function). When you deliberately omit the break so that code under the next case gets executed too that's called a fall-through. So for the OP's requirement:

switch (pageid) {
   case "listing-page":
   case "home-page":

   case "details-page":

Forgetting to include break statements is a fairly common coding mistake and is the first thing you should look for if your switch isn't working the way you expected. For that reason some people like to put a comment in to say "fall through" to make it clear when break statements have been omitted on purpose. I do that in the following example since it is a bit more complicated and shows how some cases can include code to execute before they fall-through:

switch (someVar) {
   case 1:
      alert("It was 1");
      // fall through
   case 2:
      alert("The 2 case");
      // fall through
   case 3:
      // fall through
   case 4:
      // fall through
   case 5:
      alert("The 5 case");
      // fall through
   case 6:
      alert("The 6 case");

   case 7:
      alert("Something else");

   case 8:
      // fall through
      alert("The end");

You can also (optionally) include a default case, which will be executed if none of the other cases match - if you don't include a default and no cases match then nothing happens. You can (optionally) fall through to the default case.

So in my second example if someVar is 1 it would call someFunction() and then you would see four alerts as it falls through multiple cases some of which have alerts under them. Is someVar is 3, 4 or 5 you'd see two alerts. If someVar is 7 you'd see "Something else" and if it is 8 or any other value you'd see "The end".

Show a popup/message box from a Windows batch file

This will pop-up another Command Prompt window:

START CMD /C "ECHO My Popup Message && PAUSE"

Using BufferedReader.readLine() in a while loop properly

Concept returns particular character's int value so loop continue's until we won't get -1 as int value and Hence up to there it prints br.readLine() which returns a line into String form.

    //Way 1:
      //continues loop until we won't get int value as a -1

    //Way 2:

    //Way 3:
    for(String line=br.readLine();line!=null;line=br.readLine())

Way 4: It's an advance way to read file using collection and arrays concept How we iterate using for each loop. check it here

DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss") is returning AM time instead of PM time?

Use HH for 24 hour hours format:

DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")

Or the tt format specifier for the AM/PM part:

DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss tt")

Take a look at the custom Date and Time format strings documentation.

simple HTTP server in Java using only Java SE API

Since Java SE 6, there's a builtin HTTP server in Sun Oracle JRE. The package summary outlines the involved classes and contains examples.

Here's a kickoff example copypasted from their docs (to all people trying to edit it nonetheless, because it's an ugly piece of code, please don't, this is a copy paste, not mine, moreover you should never edit quotations unless they have changed in the original source). You can just copy'n'paste'n'run it on Java 6+.

package com.stackoverflow.q3732109;



public class Test {

    public static void main(String[] args) throws Exception {
        HttpServer server = HttpServer.create(new InetSocketAddress(8000), 0);
        server.createContext("/test", new MyHandler());
        server.setExecutor(null); // creates a default executor

    static class MyHandler implements HttpHandler {
        public void handle(HttpExchange t) throws IOException {
            String response = "This is the response";
            t.sendResponseHeaders(200, response.length());
            OutputStream os = t.getResponseBody();


Noted should be that the response.length() part in their example is bad, it should have been response.getBytes().length. Even then, the getBytes() method must explicitly specify the charset which you then specify in the response header. Alas, albeit misguiding to starters, it's after all just a basic kickoff example.

Execute it and go to http://localhost:8000/test and you'll see the following response:

This is the response

As to using com.sun.* classes, do note that this is, in contrary to what some developers think, absolutely not forbidden by the well known FAQ Why Developers Should Not Write Programs That Call 'sun' Packages. That FAQ concerns the sun.* package (such as sun.misc.BASE64Encoder) for internal usage by the Oracle JRE (which would thus kill your application when you run it on a different JRE), not the com.sun.* package. Sun/Oracle also just develop software on top of the Java SE API themselves like as every other company such as Apache and so on. Using com.sun.* classes is only discouraged (but not forbidden) when it concerns an implementation of a certain Java API, such as GlassFish (Java EE impl), Mojarra (JSF impl), Jersey (JAX-RS impl), etc.

Get int value from enum in C#

To ensure an enum value exists and then parse it, you can also do the following.

// Fake Day of Week
string strDOWFake = "SuperDay";

// Real Day of Week
string strDOWReal = "Friday";

// Will hold which ever is the real DOW.
DayOfWeek enmDOW;

// See if fake DOW is defined in the DayOfWeek enumeration.
if (Enum.IsDefined(typeof(DayOfWeek), strDOWFake))
    // This will never be reached since "SuperDay"
    // doesn't exist in the DayOfWeek enumeration.
    enmDOW = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), strDOWFake);
// See if real DOW is defined in the DayOfWeek enumeration.
else if (Enum.IsDefined(typeof(DayOfWeek), strDOWReal))
    // This will parse the string into it's corresponding DOW enum object.
    enmDOW = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), strDOWReal);

// Can now use the DOW enum object.
Console.Write("Today is " + enmDOW.ToString() + ".");

How can I change the version of npm using nvm?

What about npm i -g npm? Did you try to run this as well?

Parse JSON from HttpURLConnection object

The JSON string will just be the body of the response you get back from the URL you have called. So add this code

BufferedReader in = new BufferedReader(new InputStreamReader(
String inputLine;
while ((inputLine = in.readLine()) != null) 

That will allow you to see the JSON being returned to the console. The only missing piece you then have is using a JSON library to read that data and provide you with a Java representation.

Here's an example using JSON-LIB

Python Timezone conversion

For Python timezone conversions, I use the handy table from the PyCon 2012 presentation by Taavi Burns.

Where does mysql store data?

as @PhilHarvey said, you can use mysqld --verbose --help | grep datadir

Elasticsearch: Failed to connect to localhost port 9200 - Connection refused

I experienced a similar issue.

Here's how I solved it

Run the service command below to start ElasticSearch

sudo service elasticsearch start


sudo systemctl start elasticsearch

If you still get the error

curl: (7) Failed to connect to localhost port 9200: Connection refused

Run the service command below to check the status of ElasticSearch

sudo service elasticsearch status


sudo systemctl status elasticsearch

If you get a response (Active: active (running)) like the one below then you ElasticSearch is active and running

? elasticsearch.service - Elasticsearch Loaded: loaded (/usr/lib/systemd/system/elasticsearch.service; disabled; vendor preset: enabled) Active: active (running) since Sat 2019-09-21 11:22:21 WAT; 3s ago

You can then test that your Elasticsearch node is running by sending an HTTP request to port 9200 on localhost using the command below:

curl http://localhost:9200

Else, if you get a response a different response, you may have to debug further to fix it, but the running the command below, will help you detect what caveats are holding ElasticSearch service from starting.

sudo service elasticsearch status


sudo systemctl status elasticsearch

If you want to stop the ElasticSearch service, simply run the service command below;

sudo service elasticsearch stop


sudo systemctl stop elasticsearch

N/B: You may have to run the command sudo service elasticsearch status OR sudo systemctl status elasticsearch each time you encounter the error, in order to tell the state of the ElasticSearch service.

This also applies for Kibana, run the command sudo service kibana status OR sudo systemctl status kibana each time you encounter the error, in order to tell the state of the Kibana service.

That's all.

I hope this helps.

The difference between the Runnable and Callable interfaces in Java

Let us look at where one would use Runnable and Callable.

Runnable and Callable both run on a different thread than the calling thread. But Callable can return a value and Runnable cannot. So where does this really apply.

Runnable : If you have a fire and forget task then use Runnable. Put your code inside a Runnable and when the run() method is called, you can perform your task. The calling thread really does not care when you perform your task.

Callable : If you are trying to retrieve a value from a task, then use Callable. Now callable on its own will not do the job. You will need a Future that you wrap around your Callable and get your values on future.get (). Here the calling thread will be blocked till the Future comes back with results which in turn is waiting for Callable's call() method to execute.

So think about an interface to a target class where you have both Runnable and Callable wrapped methods defined. The calling class will randomly call your interface methods not knowing which is Runnable and which is Callable. The Runnable methods will execute asynchronously, till a Callable method is called. Here the calling class's thread will block since you are retrieving values from your target class.

NOTE : Inside your target class you can make the calls to Callable and Runnable on a single thread executor, making this mechanism similar to a serial dispatch queue. So as long as the caller calls your Runnable wrapped methods the calling thread will execute really fast without blocking. As soon as it calls a Callable wrapped in Future method it will have to block till all the other queued items are executed. Only then the method will return with values. This is a synchronization mechanism.

Postgresql 9.2 pg_dump version mismatch

Download the appropriate postgres version here:

Make sure to run the following commands (the URL will generate the specific URL for you to use; the one I use below is just an example for centos 7) as sudo:

sudo yum install
sudo yum install postgresql11-server

your pg_dump version should now be updated, verify with pg_dump -V

jquery $('.class').each() how many items?

If you are using a version of jQuery that is less than version 1.8 you can use the $('.class').size() which takes zero parameters. See documentation for more information on .size() method.

However if you are using (or plan to upgrade) to 1.8 or greater you can use $('.class').length property. See documentation for more information on .length property.