Programs & Examples On #Radgrid

RadGrid is an ASP.NET based grid control by Telerik that provides many advanced functions.

How to change the buttons text using javascript

I know this question has been answered but I also see there is another way missing which I would like to cover it.There are multiple ways to achieve this.

1- innerHTML

document.getElementById("ShowButton").innerHTML = 'Show Filter';

You can insert HTML into this. But the disadvantage of this method is, it has cross site security attacks. So for adding text, its better to avoid this for security reasons.

2- innerText

document.getElementById("ShowButton").innerText = 'Show Filter';

This will also achieve the result but its heavy under the hood as it requires some layout system information, due to which the performance decreases. Unlike innerHTML, you cannot insert the HTML tags with this. Check Performance Here

3- textContent

document.getElementById("ShowButton").textContent = 'Show Filter';

This will also achieve the same result but it doesn't have security issues like innerHTML as it doesn't parse HTML like innerText. Besides, it is also light due to which performance increases.

So if a text has to be added like above, then its better to use textContent.

Google maps Marker Label with multiple characters

First of all, Thanks to code author!

I found the below link while googling and it is very simple and works best. Would never fail unless SVG is deprecated.

There is some js loading error in the code here but its perfectly working on the link provided.

var mapOptions = {_x000D_
    zoom: 16,_x000D_
    center: new google.maps.LatLng(-37.808846, 144.963435)_x000D_
  map = new google.maps.Map(document.getElementById('map-canvas'),_x000D_
var pinz = [_x000D_
            'lat' : -37.807817,_x000D_
            'lon' : 144.958377_x000D_
        'lable' : 2_x000D_
            'lat' : -37.807885,_x000D_
            'lon' : 144.965415_x000D_
        'lable' : 42_x000D_
            'lat' : -37.811377,_x000D_
            'lon' : 144.956596_x000D_
        'lable' : 87_x000D_
            'lat' : -37.811293,_x000D_
            'lon' : 144.962883_x000D_
        'lable' : 145_x000D_
            'lat' : -37.808089,_x000D_
            'lon' : 144.962089_x000D_
        'lable' : 999_x000D_
for(var i = 0; i <= pinz.length; i++){_x000D_
   var image = 'data:image/svg+xml,' + pinz[i].lable + '%3C%2Ftext%3E%3C%2Fsvg%3E';_x000D_
   var myLatLng = new google.maps.LatLng(pinz[i], pinz[i].location.lon);_x000D_
   var marker = new google.maps.Marker({_x000D_
      position: myLatLng,_x000D_
      map: map,_x000D_
      icon: image_x000D_
html, body, #map-canvas {_x000D_
  height: 100%;_x000D_
  margin: 0px;_x000D_
  padding: 0px_x000D_
<div id="map-canvas"></div>_x000D_
<script async defer src=",places"></script>

You just need to uri-encode your SVG html and replace the one in the image variable after "data:image/svg+xml" in the for loop.

For uri encoding you can use uri-encoder-decoder

You can decode the existing svg code first to get a better understanding of what is written.

How to get the latest file in a folder?

Whatever is assigned to the files variable is incorrect. Use the following code.

import glob
import os

list_of_files = glob.glob('/path/to/folder/*') # * means all if need specific format then *.csv
latest_file = max(list_of_files, key=os.path.getctime)

Making a Bootstrap table column fit to content

Kind of an old question, but I arrived here looking for this. I wanted the table to be as small as possible, fitting to it's contents. The solution was to simply set the table width to an arbitrary small number (1px for example). I even created a CSS class to handle it:

.table-fit {
    width: 1px;

And use it like so:

<table class="table table-fit">

Example: JSFiddle

Differences between Lodash and Underscore.js

I just found one difference that ended up being important for me. The non-Underscore.js-compatible version of Lodash's _.extend() does not copy over class-level-defined properties or methods.

I've created a Jasmine test in CoffeeScript that demonstrates this:

Fortunately, lodash.underscore.js preserves Underscore.js's behaviour of copying everything, which for my situation was the desired behaviour.

Most efficient way to check if a file is empty in Java on Windows

Stolen from

FileInputStream fis = new FileInputStream(new File("file_name"));  
int b =;  
if (b == -1)  
  System.out.println("!!File " + file_name + " emty!!");  

Updated: My first answer was premature and contained a bug.

How to find out which processes are using swap space in Linux?

Here's a version that outputs the same as the script by @loolotux, but is much faster(while less readable). That loop takes about 10 secs on my machine, my version takes 0.019 s, which mattered to me because I wanted to make it into a cgi page.

    join -t / -1 3 -2 3 \
    <(grep VmSwap /proc/*/status  |egrep -v '/proc/self|thread-self' | sort -k3,3 --field-separator=/ ) \
    <(grep -H  '' --binary-files=text /proc/*/cmdline |tr '\0' ' '|cut -c 1-200|egrep -v '/proc/self|/thread-self'|sort -k3,3 --field-separator=/ ) \
    | cut -d/ -f1,4,7- \
    | sed 's/status//; s/cmdline//' \
    | sort -h -k3,3 --field-separator=:\
    | tee >(awk -F: '{s+=$3} END {printf "\nTotal Swap Usage = %.0f kB\n",s}') /dev/null

How to compress an image via Javascript in the browser?

In short:

  • Read the files using the HTML5 FileReader API with .readAsArrayBuffer
  • Create a Blob with the file data and get its url with window.URL.createObjectURL(blob)
  • Create new Image element and set it's src to the file blob url
  • Send the image to the canvas. The canvas size is set to desired output size
  • Get the scaled-down data back from canvas via canvas.toDataURL("image/jpeg",0.7) (set your own output format and quality)
  • Attach new hidden inputs to the original form and transfer the dataURI images basically as normal text
  • On backend, read the dataURI, decode from Base64, and save it

Source: code.

Difference between git stash pop and git stash apply

Seeing it in action might help you better understanding the difference.

Assuming we're working on master branch and have a file hello.txt that contains "Hello" string.

Let's modify the file and add " world" string to it. Now you want to move to a different branch to fix a minor bug you've just found, so you need to stash your changes:

git stash

You moved to the other branch, fixed the bug and now you're ready to continue working on your master branch, so you pop the changes:

git stash pop

Now if you try to review the stash content you'll get:

$ git stash show -p
No stash found.

However, if you use git stash apply instead, you'll get the stashed content but you'll also keep it:

$ git stash show -p
diff --git a/hello.txt b/hello.txt
index e965047..802992c 100644
--- a/hello.txt
+++ b/hello.txt
@@ -1 +1 @@
+Hello world

So pop is just like stack's pop - it actually removes the element once it's popped, while apply is more like peek.

Showing line numbers in IPython/Jupyter Notebooks

For me, ctrl + m is used to save the webpage as png, so it does not work properly. But I find another way.

On the toolbar, there is a bottom named open the command paletee, you can click it and type in the line, and you can see the toggle cell line number here.

Rename multiple files by replacing a particular pattern in the filenames using a shell script

You can use rename utility to rename multiple files by a pattern. For example following command will prepend string MyVacation2011_ to all the files with jpg extension.

rename 's/^/MyVacation2011_/g' *.jpg


rename <pattern> <replacement> <file-list>

How do I encode and decode a base64 string?

    using System;
    using System.Text;

    public static class Base64Conversions
        public static string EncodeBase64(this string text, Encoding encoding = null)
            if (text == null) return null;

            encoding = encoding ?? Encoding.UTF8;
            var bytes = encoding.GetBytes(text);
            return Convert.ToBase64String(bytes);

        public static string DecodeBase64(this string encodedText, Encoding encoding = null)
            if (encodedText == null) return null;

            encoding = encoding ?? Encoding.UTF8;
            var bytes = Convert.FromBase64String(encodedText);
            return encoding.GetString(bytes);


    var text = "Sample Text";
    var base64 = text.EncodeBase64();
    base64 = text.EncodeBase64(Encoding.UTF8); //or with Encoding

What is The Rule of Three?

What does copying an object mean? There are a few ways you can copy objects--let's talk about the 2 kinds you're most likely referring to--deep copy and shallow copy.

Since we're in an object-oriented language (or at least are assuming so), let's say you have a piece of memory allocated. Since it's an OO-language, we can easily refer to chunks of memory we allocate because they are usually primitive variables (ints, chars, bytes) or classes we defined that are made of our own types and primitives. So let's say we have a class of Car as follows:

class Car //A very simple class just to demonstrate what these definitions mean.
//It's pseudocode C++/Javaish, I assume strings do not need to be allocated.
private String sPrintColor;
private String sModel;
private String sMake;

public changePaint(String newColor)
   this.sPrintColor = newColor;

public Car(String model, String make, String color) //Constructor
   this.sPrintColor = color;
   this.sModel = model;
   this.sMake = make;

public ~Car() //Destructor
//Because we did not create any custom types, we aren't adding more code.
//Anytime your object goes out of scope / program collects garbage / etc. this guy gets called + all other related destructors.
//Since we did not use anything but strings, we have nothing additional to handle.
//The assumption is being made that the 3 strings will be handled by string's destructor and that it is being called automatically--if this were not the case you would need to do it here.

public Car(const Car &other) // Copy Constructor
   this.sPrintColor = other.sPrintColor;
   this.sModel = other.sModel;
   this.sMake = other.sMake;
public Car &operator =(const Car &other) // Assignment Operator
   if(this != &other)
      this.sPrintColor = other.sPrintColor;
      this.sModel = other.sModel;
      this.sMake = other.sMake;
   return *this;


A deep copy is if we declare an object and then create a completely separate copy of the object...we end up with 2 objects in 2 completely sets of memory.

Car car1 = new Car("mustang", "ford", "red");
Car car2 = car1; //Call the copy constructor
//car2 is now green but car1 is still red.

Now let's do something strange. Let's say car2 is either programmed wrong or purposely meant to share the actual memory that car1 is made of. (It's usually a mistake to do this and in classes is usually the blanket it's discussed under.) Pretend that anytime you ask about car2, you're really resolving a pointer to car1's memory space...that's more or less what a shallow copy is.

//Shallow copy example
//Assume we're in C++ because it's standard behavior is to shallow copy objects if you do not have a constructor written for an operation.
//Now let's assume I do not have any code for the assignment or copy operations like I do above...with those now gone, C++ will use the default.

 Car car1 = new Car("ford", "mustang", "red"); 
 Car car2 = car1; 
 car2.changePaint("green");//car1 is also now green 
 delete car2;/*I get rid of my car which is also really your car...I told C++ to resolve 
 the address of where car2 exists and delete the memory...which is also
 the memory associated with your car.*/
 car1.changePaint("red");/*program will likely crash because this area is
 no longer allocated to the program.*/

So regardless of what language you're writing in, be very careful about what you mean when it comes to copying objects because most of the time you want a deep copy.

What are the copy constructor and the copy assignment operator? I have already used them above. The copy constructor is called when you type code such as Car car2 = car1; Essentially if you declare a variable and assign it in one line, that's when the copy constructor is called. The assignment operator is what happens when you use an equal sign--car2 = car1;. Notice car2 isn't declared in the same statement. The two chunks of code you write for these operations are likely very similar. In fact the typical design pattern has another function you call to set everything once you're satisfied the initial copy/assignment is legitimate--if you look at the longhand code I wrote, the functions are nearly identical.

When do I need to declare them myself? If you are not writing code that is to be shared or for production in some manner, you really only need to declare them when you need them. You do need to be aware of what your program language does if you choose to use it 'by accident' and didn't make one--i.e. you get the compiler default. I rarely use copy constructors for instance, but assignment operator overrides are very common. Did you know you can override what addition, subtraction, etc. mean as well?

How can I prevent my objects from being copied? Override all of the ways you're allowed to allocate memory for your object with a private function is a reasonable start. If you really don't want people copying them, you could make it public and alert the programmer by throwing an exception and also not copying the object.

How to send email to multiple address using System.Net.Mail

StewieFG suggestion is valid but if you want to add the recipient name use this, with what Marco has posted above but is email address first and display name second:

msg.To.Add(new MailAddress("[email protected]","Your name 1"));
msg.To.Add(new MailAddress("[email protected]","Your name 2"));

How can I specify a [DllImport] path at runtime?

Even better than Ran's suggestion of using GetProcAddress, simply make the call to LoadLibrary before any calls to the DllImport functions (with only a filename without a path) and they'll use the loaded module automatically.

I've used this method to choose at runtime whether to load a 32-bit or 64-bit native DLL without having to modify a bunch of P/Invoke-d functions. Stick the loading code in a static constructor for the type that has the imported functions and it'll all work fine.

How to add an action to a UIAlertView button using Swift iOS

Swift 3.0 Version of Jake's Answer

// Create the alert controller

let alertController = UIAlertController(title: "Alert!", message: "There is no items for the current user", preferredStyle: .alert)

            // Create the actions
            let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default) {
                UIAlertAction in
                NSLog("OK Pressed")
            let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel) {
                UIAlertAction in
                NSLog("Cancel Pressed")

            // Add the actions

            // Present the controller
            self.present(alertController, animated: true, completion: nil)

ng: command not found while creating new project using angular-cli

In my case, I was simply running the wrong node version.

I had just previously installed a new node version to play around with Angular (2). At work we use 6.x so that is my default in nvm. After restarting the laptop ng stopped working simply because I was running node 6.x again. So for me it was simply a matter of using the version with which I was installing the Angular CLI:

nvm use node // with the node alias pointing to the right version


nvm use v8.11.3 // if you happen to know the version

Check your installed versions and aliases with

nvm list 

How to increase executionTimeout for a long-running query?

in my case, I need to have my wcf running for more than 2 hours. Setting and did not work at all. The wcf did not execute longer than maybe 20~30 minutes. So I changed the idle timeout setting of application pool in IIS manager then it worked! In IIS manager, choose your application pool and right click on it and choose advanced settings then change the idle timeout setting to any minutes you want. So, I think setting the web.config and setting the application pool are both needed.

How to upgrade all Python packages with pip

This seems more concise.

pip list --outdated | cut -d ' ' -f1 | xargs -n1 pip install -U


pip list --outdated gets lines like these

urllib3 (1.7.1) - Latest: 1.15.1 [wheel]
wheel (0.24.0) - Latest: 0.29.0 [wheel]

In cut -d ' ' -f1, -d ' ' sets "space" as the delimiter, -f1 means to get the first column.

So the above lines becomes:


then pass them to xargs to run the command, pip install -U, with each line as appending arguments

-n1 limits the number of arguments passed to each command pip install -U to be 1

Replace new line/return with space using regex

This should take care of space, tab and newline:

data = data.replaceAll("[ \t\n\r]*", " ");

Writing files in Node.js

You can write in a file by the following code example:

var data = [{ 'test': '123', 'test2': 'Lorem Ipsem ' }]; + '/data/topplayers.json', 'wx', function (error, fileDescriptor) {
  if (!error && fileDescriptor) {
    var stringData = JSON.stringify(data);
    fs.writeFile(fileDescriptor, stringData, function (error) {
      if (!error) {
        fs.close(fileDescriptor, function (error) {
          if (!error) {
          } else {
            callback('Error in close file');
      } else {
        callback('Error in writing file.');

Difference between static and shared libraries?

A static library is like a bookstore, and a shared library is like... a library. With the former, you get your own copy of the book/function to take home; with the latter you and everyone else go to the library to use the same book/function. So anyone who wants to use the (shared) library needs to know where it is, because you have to "go get" the book/function. With a static library, the book/function is yours to own, and you keep it within your home/program, and once you have it you don't care where or when you got it.

Using $_POST to get select option value from HTML

<select name="taskOption">
<option value="1">First</option>
<option value="2">Second</option>
<option value="3">Third</option>

try this

$var = $_POST['taskOption']
if($var == "1"){
echo"your data here";

Set default time in bootstrap-datetimepicker

This works for me after a long hours of search , This solution is for Bootstrap datetimepicker version 4. when you have to set the default date in input field.


"input type='text' class="form-control" id='datetimepicker5' placeholder="Select to date" value='<?php echo $myDate?>'// $myDate is having value '2016-02-23' "

Note- If You are coding in php then you can set the value of the input datefield using php, but datetimepicker sets it back to current date when you apply datetimepicker() function to it. So in order to prevent it, use the given JS code


           useCurrent: false //this is important as the functions sets the default date value to the current value 
           ,format: 'YYYY-MM-DD'

Use index in pandas to plot data

Marius's answer worked perfectly for me:

df.reset_index() sets the index as the first column, with the column label "index." You can now use the index as an axis for plotting, as described in his answer:

monthly_mean.reset_index().plot(x='index', y='A')

However, this does not change the original dataframe. The original dataframe will be unchanged unless it is set using df = df.reset_index().


        COF    TSF    PSF
3.0   0.946  0.914  0.966
4.0   0.963  0.940  0.976
6.0   0.978  0.965  0.987
8.0   0.989  0.984  0.995
10.0  1.000  1.000  1.000
12.0  1.004  1.013  1.009
15.0  1.013  1.026  1.012
17.0  1.019  1.037  1.017
20.0  1.024  1.045  1.020
25.0  1.030  1.057  1.026
30.0  1.034  1.065  1.030
35.0  1.037  1.069  1.031
40.0  1.037  1.068  1.030
60.0  1.037  1.068  1.030
df = df.reset_index()
    index    COF    TSF    PSF
0     3.0  0.946  0.914  0.966
1     4.0  0.963  0.940  0.976
2     6.0  0.978  0.965  0.987
3     8.0  0.989  0.984  0.995
4    10.0  1.000  1.000  1.000
5    12.0  1.004  1.013  1.009
6    15.0  1.013  1.026  1.012
7    17.0  1.019  1.037  1.017
8    20.0  1.024  1.045  1.020
9    25.0  1.030  1.057  1.026
10   30.0  1.034  1.065  1.030
11   35.0  1.037  1.069  1.031
12   40.0  1.037  1.068  1.030
13   60.0  1.037  1.068  1.030

See: DataFrame.reset_index and DataFrame.set_index

Force index use in Oracle

You can use optimizer hints

select /*+ INDEX(table_name index_name) */ from table etc...

More on using optimizer hints:

C# difference between == and Equals()

Firstly, there is a difference. For numbers

> 2 == 2.0

> 2.Equals(2.0)

And for strings

> string x = null;
> x == null

> x.Equals(null)

In both cases, == behaves more usefully than .Equals

Android - Activity vs FragmentActivity?

If you use the Eclipse "New Android Project" wizard in a recent ADT bundle, you'll automatically get tabs implemented as a Fragments. This makes the conversion of your application to the tablet format much easier in the future.

For simple single screen layouts you may still use Activity.

An existing connection was forcibly closed by the remote host

I got the same issue while using .NET Framework 4.5. However, when I update the .NET version to 4.7.2 connection issue was resolved. Maybe this is due to SecurityProtocol support issue.

Java : Comparable vs Comparator

Comparator provides a way for you to provide custom comparison logic for types that you have no control over.

Comparable allows you to specify how objects that you are implementing get compared.

Obviously, if you don't have control over a class (or you want to provide multiple ways to compare objects that you do have control over) then use Comparator.

Otherwise you can use Comparable.

How can I execute Python scripts using Anaconda's version of Python?

The instructions in the official Python documentation worked for me:

  1. Launch a command prompt.

  2. Associate the correct file group with .py scripts:

    assoc .py=Python.File

Redirect all Python files to the new executable:

    ftype Python.File=C:\Path\to\pythonw.exe "%1" %*

The example shows how to associate the .py extension with the .pyw executable, but it works if you want to associate the .py extension with the Anaconda Python executable. You need administrative rights. The name "Python.File" could be anything, you just have to make sure is the same name in the ftype command. When you finish and before you try double-clicking the .py file, you must change the "Open with" in the file properties. The file type will be now ".py" and it is opened with the Anaconda python.exe.

The PowerShell -and conditional operator

Another option:

if( ![string]::IsNullOrEmpty($user_sam) -and ![string]::IsNullOrEmpty($user_case) )

How do DATETIME values work in SQLite?

SQlite does not have a specific datetime type. You can use TEXT, REAL or INTEGER types, whichever suits your needs.

Straight from the DOCS

SQLite does not have a storage class set aside for storing dates and/or times. Instead, the built-in Date And Time Functions of SQLite are capable of storing dates and times as TEXT, REAL, or INTEGER values:

  • TEXT as ISO8601 strings ("YYYY-MM-DD HH:MM:SS.SSS").
  • REAL as Julian day numbers, the number of days since noon in Greenwich on November 24, 4714 B.C. according to the proleptic Gregorian calendar.
  • INTEGER as Unix Time, the number of seconds since 1970-01-01 00:00:00 UTC.

Applications can chose to store dates and times in any of these formats and freely convert between formats using the built-in date and time functions.

SQLite built-in Date and Time functions can be found here.

Play sound file in a web-page in the background

With me the problem was solved by removing the type attribute:

<embed name="myMusic" loop="true" hidden="true" src="Music.mp3"></embed>

Cerntainly not the cleanest way.

If you're using HTML5: MP3 isn't supported by Firefox. Wav and Ogg are though. Here you can find an overview of which browser support which type of audio:

Boxplot in R showing the mean

Based on the answers by @James and @Jyotirmoy Bhattacharya I came up with this solution:

zx <- replicate (5, rnorm(50))
zx_means <- (colMeans(zx, na.rm = TRUE))
boxplot(zx, horizontal = FALSE, outline = FALSE)
points(zx_means, pch = 22, col = "darkgrey", lwd = 7)

(See this post for more details)

If you would like to add points to horizontal box plots, please see this post.

Why would you use String.Equals over ==?

There is practical difference between string.Equals and ==

bool result = false;

object obj = "String";    
string str2 = "String";
string str3 = typeof(string).Name;
string str4 = "String";
object obj2 = str3;

// Comparision between object obj and string str2 -- Com 1
result = string.Equals(obj, str2);// true
result = String.ReferenceEquals(obj, str2); // true
result = (obj == str2);// true

// Comparision between object obj and string str3 -- Com 2
result = string.Equals(obj, str3);// true
result = String.ReferenceEquals(obj, str3); // false
result = (obj == str3);// false

// Comparision between object obj and string str4 -- Com 3
result = string.Equals(obj, str4);// true
result = String.ReferenceEquals(obj, str4); // true
result = (obj == str4);// true

// Comparision between string str2 and string str3 -- Com 4
result = string.Equals(str2, str3);// true
result = String.ReferenceEquals(str2, str3); // false
result = (str2 == str3);// true

// Comparision between string str2 and string str4 -- Com 5
result = string.Equals(str2, str4);// true
result = String.ReferenceEquals(str2, str4); // true
result = (str2 == str4);// true

// Comparision between string str3 and string str4 -- Com 6
result = string.Equals(str3, str4);// true
result = String.ReferenceEquals(str3, str4); // false
result = (str3 == str4);// true

// Comparision between object obj and object obj2 -- Com 7
result = String.Equals(obj, obj2);// true
result = String.ReferenceEquals(obj, obj2); // false
result = (obj == obj2);// false

Adding Watch

obj     "String" {1#}   object {string}
str2    "String" {1#}   string
str3    "String" {5#}   string
str4    "String" {1#}   string
obj2    "String" {5#}   object {string}

Now look at {1#} and {5#}

obj, str2, str4 and obj2 references are same.

obj and obj2 are object type and others are string type


  1. com1: result = (obj == str2);// true
    • compares object and string so performs a reference equality check
    • obj and str2 point to the same reference so the result is true
  2. com2: result = (obj == str3);// false
    • compares object and string so performs a reference equality check
    • obj and str3 point to the different references so the result is false
  3. com3: result = (obj == str4);// true
    • compares object and string so performs a reference equality check
    • obj and str4 point to the same reference so the result is true
  4. com4: result = (str2 == str3);// true
    • compares string and string so performs a string value check
    • str2 and str3 are both "String" so the result is true
  5. com5: result = (str2 == str4);// true
    • compares string and string so performs a string value check
    • str2 and str4 are both "String" so the result is true
  6. com6: result = (str3 == str4);// true
    • compares string and string so performs a string value check
    • str3 and str4 are both "String" so the result is true
  7. com7: result = (obj == obj2);// false  - compares object and object so performs a reference equality check      - obj and obj2 point to the different references so the result is false

How to debug in Android Studio using adb over WiFi

You can find the adb tool in /platform-tools/

cd Library/Android/sdk/platform-tools/

You can check your devices using:

./adb devices

My result:

List of devices attached
XXXXXXXXX   device

Set a TCP port:

./adb shell setprop service.adb.tcp.port 4444

./adb tcpip 4444

Result message:

restarting in TCP mode port: 4444

To init a wifi connection you have to check your device IP and execute:

./adb connect

Good luck!

"Unable to locate tools.jar" when running ant

  1. Try to check it once more according to this tutorial:

  2. Try to reboot your system.

  3. If nothing, try to run "cmd" and type there "java", does it print anything?

Python import csv to list

As said already in the comments you can use the csv library in python. csv means comma separated values which seems exactly your case: a label and a value separated by a comma.

Being a category and value type I would rather use a dictionary type instead of a list of tuples.

Anyway in the code below I show both ways: d is the dictionary and l is the list of tuples.

import csv

file_name = "test.txt"
    csvfile = open(file_name, 'rt')
    print("File not found")
csvReader = csv.reader(csvfile, delimiter=",")
d = dict()
l =  list()
for row in csvReader:
    d[row[1]] = row[0]
    l.append((row[0], row[1]))

Check if int is between two numbers

The inconvenience of typing 10 < x && x < 20 is minimal compared to the increase in language complexity if one would allow 10 < x < 20, so the designers of the Java language decided against supporting it.

take(1) vs first()

There's one really important difference which is not mentioned anywhere.

take(1) emits 1, completes, unsubscribes

first() emits 1, completes, but doesn't unsubscribe.

It means that your upstream observable will still be hot after first() which is probably not expected behavior.

UPD: This referes to RxJS 5.2.0. This issue might be already fixed.

switch() statement usage

In short, yes. But there are times when you might favor one vs. the other. Google "case switch vs. if else". There are some discussions already on SO too. Also, here is a good video that talks about it in the context of MATLAB:

Personally, when I have 3 or more cases, I usually just go with case/switch.

PyLint "Unable to import" error - how to set PYTHONPATH?

Maybe by manually appending the dir inside the PYTHONPATH?


Class has no member named

Maybe I am 6.5 years late. But I'm answering because others maybe searching still now. I faced the same problem and was searching everywhere. But then I realized I had written my code in an empty file. If you create a project and write your code in there, there won't be this error.

Trim to remove white space

Why not try this?


  a b c



What does '--set-upstream' do?

git branch --set-upstream <<origin/branch>> is officially not supported anymore and is replaced by git branch --set-upstream-to <<origin/branch>>

twitter bootstrap autocomplete dropdown / combobox with Knockoutjs

Select2 for Bootstrap 3 native plugin

this plugin uses select2 jquery plugin


PM> Install-Package Select2-Bootstrap

Joining three tables using MySQL

Simply use:

select "Student", "Course"
from student s, bridge b, course c
where b.sid = s.sid and b.cid = c.cid 

How to Automatically Close Alerts using Twitter Bootstrap

After going over some of the answers here an in another thread, here's what I ended up with:

I created a function named showAlert() that would dynamically add an alert, with an optional type and closeDealy. So that you can, for example, add an alert of type danger (i.e., Bootstrap's alert-danger) that will close automatically after 5 seconds like so:

showAlert("Warning message", "danger", 5000);

To achieve that, add the following Javascript function:

function showAlert(message, type, closeDelay) {

    if ($("#alerts-container").length == 0) {
        // alerts-container does not exist, add it
            .append( $('<div id="alerts-container" style="position: fixed;
                width: 50%; left: 25%; top: 10%;">') );

    // default to alert-info; other options include success, warning, danger
    type = type || "info";    

    // create the alert div
    var alert = $('<div class="alert alert-' + type + ' fade in">')
            $('<button type="button" class="close" data-dismiss="alert">')

    // add the alert div to top of alerts-container, use append() to add to bottom

    // if closeDelay was passed - set a timeout to close the alert
    if (closeDelay)
        window.setTimeout(function() { alert.alert("close") }, closeDelay);     

What is tail call optimization?

TCO (Tail Call Optimization) is the process by which a smart compiler can make a call to a function and take no additional stack space. The only situation in which this happens is if the last instruction executed in a function f is a call to a function g (Note: g can be f). The key here is that f no longer needs stack space - it simply calls g and then returns whatever g would return. In this case the optimization can be made that g just runs and returns whatever value it would have to the thing that called f.

This optimization can make recursive calls take constant stack space, rather than explode.

Example: this factorial function is not TCOptimizable:

def fact(n):
    if n == 0:
        return 1
    return n * fact(n-1)

This function does things besides call another function in its return statement.

This below function is TCOptimizable:

def fact_h(n, acc):
    if n == 0:
        return acc
    return fact_h(n-1, acc*n)

def fact(n):
    return fact_h(n, 1)

This is because the last thing to happen in any of these functions is to call another function.

DATEDIFF function in Oracle

We can directly subtract dates to get difference in Days.

        V_VAR NUMBER;
         V_VAR:=TO_DATE('2000-01-02', 'YYYY-MM-DD') - TO_DATE('2000-01-01', 'YYYY-MM-DD') ;

What is the most compatible way to install python modules on a Mac?

You may already have pip3 pre-installed, so just try it!

Mysql: Select all data between two dates

You can use a concept that is frequently referred to as 'calendar tables'. Here is a good guide on how to create calendar tables in MySql:

-- create some infrastructure
INSERT INTO ints VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9);

-- only works for 100 days, add more ints joins for more
    SELECT '2009-06-25' + INTERVAL a.i * 10 + b.i DAY as date
    FROM ints a JOIN ints b
    ORDER BY a.i * 10 + b.i
) cal LEFT JOIN tbl ON =
WHERE BETWEEN '2009-06-25' AND '2009-07-01';

You might want to create table cal instead of the subselect.

I want to use CASE statement to update some records in sql server 2005

This is also an alternate use of case-when...

UPDATE [dbo].[JobTemplates]
SET [CycleId] = 
    CASE [Id]
        WHEN 1376 THEN 44   --ACE1 FX1
        WHEN 1385 THEN 44   --ACE1 FX2
        WHEN 1574 THEN 43   --ACE1 ELEM1
        WHEN 1576 THEN 43   --ACE1 ELEM2
        WHEN 1581 THEN 41   --ACE1 FS1
        WHEN 1585 THEN 42   --ACE1 HS1
        WHEN 1588 THEN 43   --ACE1 RS1
        WHEN 1589 THEN 44   --ACE1 RM1
        WHEN 1590 THEN 43   --ACE1 ELEM3
        WHEN 1591 THEN 43   --ACE1 ELEM4
        WHEN 1595 THEN 44   --ACE1 SSTn     
        ELSE 0  
    [Id] IN (1376,1385,1574,1576,1581,1585,1588,1589,1590,1591,1595)

I like the use of the temporary tables in cases where duplicate values are not permitted and your update may create them. For example:

    ,CASE [CycleId]
        WHEN  29 THEN 44
        WHEN  30 THEN 43
        WHEN  31 THEN 43
        WHEN 101 THEN 41
        WHEN 102 THEN 43
        WHEN 116 THEN 42
        WHEN 120 THEN 44
        WHEN 127 THEN 44
        WHEN 129 THEN 44
        ELSE    0
     END                AS [CycleId]
    [QueueId] = 3
    [BaseDimensionId], [ElastomerTypeId], [Id];
---- (403 row(s) affected)

UPDATE [dbo].[ProductionQueueProcessAutoclaveNominals]
    [CycleId] = X.[CycleId]
        MIN([Id]) AS [Id],[QueueId],[BaseDimensionId],[ElastomerTypeId],[CycleId] 
    GROUP BY    
) AS X
    [dbo].[ProductionQueueProcessAutoclaveNominals].[Id] = X.[Id];
----(375 row(s) affected)

Excel Macro - Select all cells with data and format as table

Try this one for current selection:

Sub A_SelectAllMakeTable2()
    Dim tbl As ListObject
    Set tbl = ActiveSheet.ListObjects.Add(xlSrcRange, Selection, , xlYes)
    tbl.TableStyle = "TableStyleMedium15"
End Sub

or equivalent of your macro (for Ctrl+Shift+End range selection):

Sub A_SelectAllMakeTable()
    Dim tbl As ListObject
    Dim rng As Range

    Set rng = Range(Range("A1"), Range("A1").SpecialCells(xlLastCell))
    Set tbl = ActiveSheet.ListObjects.Add(xlSrcRange, rng, , xlYes)
    tbl.TableStyle = "TableStyleMedium15"
End Sub

Convert array to JSON

If you have only 1 object like the one you asked, the following will work.

var x = [{'a':'b'}];
var b= JSON.stringify(x);
var c = b.substring(1,b.length-1);

CRON job to run on the last day of the month

You can just connect all answers in one cron line and use only date command.

Just check the difference between day of the month which is today and will be tomorrow:

0 23 * * * root [ $(expr $(date +\%d -d '1 days') - $(date +\%d)  ) -le 0 ]  && echo true

If these difference is below 0 it means that we change the month and there is last day of the month.

How do I limit the number of returned items?

models.Post.find({published: true}, {sort: {'date': -1}, limit: 20}, function(err, posts) {
 // `posts` with sorted length of 20

Find duplicates and delete all in notepad++

You could use

Click TextFX ? Click TextFX Tools ? Click Sort lines case insensitive (at column) Duplicates and blank lines have been removed and the data has been sorted alphabetically.

as indicated above. However, the way I did it because I need to replace the duplicates by blank lines and not just remove the lines, once sorted alphabetically:




This will convert:

Shorts Two Pack
Shorts Two Pack
Signature Braces
Signature Braces
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers
Signature Cotton Trousers



Shorts Two Pack

Signature Braces

Signature Cotton Trousers

That's how I did it because I specifically needed those lines.

Getting PEAR to work on XAMPP (Apache/MySQL stack on Windows)

You need to fix your include_path system variable to point to the correct location.

To fix it edit the php.ini file. In that file you will find a line that says, "include_path = ...". (You can find out what the location of php.ini by running phpinfo() on a page.) Fix the part of the line that says, "\xampplite\php\pear\PEAR" to read "C:\xampplite\php\pear". Make sure to leave the semi-colons before and/or after the line in place.

Restart PHP and you should be good to go. To restart PHP in IIS you can restart the application pool assigned to your site or, better yet, restart IIS all together.

How do I make a PHP form that submits to self?

  1. change
    <input type="submit" value="Submit" />
    <input type="submit" value="Submit" name='submit'/>

  2. change
    <form method="post" action="<?php echo $PHP_SELF;?>">
    <form method="post" action="">

  3. It will perform the code in if only when it is submitted.
  4. It will always show the form (html code).
  5. what exactly is your question?

CSS Div stretch 100% page height

I had a similar problem and the solution was to do this:


I wanted a page-centered div with height 100% of page height, so my total solution was:

    width: XXXpx; /*otherwise div defaults to page width*/
    margin: 0 auto; /*horizontally centers div*/

You might need to make a parent element (or simply 'body') have position: relative;

Determining 32 vs 64 bit in C++

I'm adding this answer as a use case and complete example for the runtime-check described in another answer.

This is the approach I've been taking for conveying to the end-user whether the program was compiled as 64-bit or 32-bit (or other, for that matter):


#ifndef MY_VERSION
#define MY_VERSION

#include <string>

const std::string version = "0.09";
const std::string arch = (std::to_string(sizeof(void*) * 8) + "-bit");


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

int main()
    std::cerr << "My App v" << version << " [" << arch << "]" << std::endl;

Compile and Test

g++ -g
My App v0.09 [64-bit]

Skipping Incompatible Libraries at compile

Normally, that is not an error per se; it is a warning that the first file it found that matches the -lPI-Http argument to the compiler/linker is not valid. The error occurs when no other library can be found with the right content.

So, you need to look to see whether /dvlpmnt/libPI-Http.a is a library of 32-bit object files or of 64-bit object files - it will likely be 64-bit if you are compiling with the -m32 option. Then you need to establish whether there is an alternative libPI-Http.a or file somewhere else that is 32-bit. If so, ensure that the directory that contains it is listed in a -L/some/where argument to the linker. If not, then you will need to obtain or build a 32-bit version of the library from somewhere.

To establish what is in that library, you may need to do:

mkdir junk
cd junk
ar x /dvlpmnt/libPI-Http.a
file *.o
cd ..
rm -fr junk

The 'file' step tells you what type of object files are in the archive. The rest just makes sure you don't make a mess that can't be easily cleaned up.

Android new Bottom Navigation bar or BottomNavigationView

You can also use Tab Layout with custom tab view to achieve this.


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

        android:src="@drawable/ic_recents_selector" />



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


        android:layout_weight="1" />

        android:background="?attr/colorPrimary" />


public class MainActivity extends AppCompatActivity {
    private TabLayout mTabLayout;

    private int[] mTabsIcons = {

    protected void onCreate(Bundle savedInstanceState) {

        // Setup the viewPager
        ViewPager viewPager = (ViewPager) findViewById(;
        MyPagerAdapter pagerAdapter = new MyPagerAdapter(getSupportFragmentManager());

        mTabLayout = (TabLayout) findViewById(;

        for (int i = 0; i < mTabLayout.getTabCount(); i++) {
            TabLayout.Tab tab = mTabLayout.getTabAt(i);


    private class MyPagerAdapter extends FragmentPagerAdapter {

        public final int PAGE_COUNT = 3;

        private final String[] mTabsTitle = {"Recents", "Favorites", "Nearby"};

        public MyPagerAdapter(FragmentManager fm) {

        public View getTabView(int position) {
            // Given you have a custom layout in `res/layout/custom_tab.xml` with a TextView and ImageView
            View view = LayoutInflater.from(MainActivity.this).inflate(R.layout.custom_tab, null);
            TextView title = (TextView) view.findViewById(;
            ImageView icon = (ImageView) view.findViewById(;
            return view;

        public Fragment getItem(int pos) {
            switch (pos) {

                case 0:
                    return PageFragment.newInstance(1);

                case 1:
                    return PageFragment.newInstance(2);
                case 2:
                    return PageFragment.newInstance(3);

            return null;

        public int getCount() {
            return PAGE_COUNT;

        public CharSequence getPageTitle(int position) {
            return mTabsTitle[position];


Download Complete Sample Project

Executing <script> elements inserted with .innerHTML

@phidah... Here is a very interesting solution to your problem:

So it would look like this instead:

<img src="empty.gif" onload="alert('test');this.parentNode.removeChild(this);" />

Linux: copy and create destination dir if it does not exist

This is very late but it may help a rookie somewhere. If you need to 'auto' create folders rsync should be your best friend. rsync /path/to/sourcefile /path/to/tragetdir/thatdoestexist/

Is key-value pair available in Typescript?

You can also consider using Record, like this:

const someArray: Record<string, string>[] = [
    {'first': 'one'},
    {'second': 'two'}

Or write something like this:

const someArray: {key: string, value: string}[] = [
    {key: 'first', value: 'one'},
    {key: 'second', value: 'two'}

Web API Put Request generates an Http 405 Method Not Allowed error

This simple problem can cause a real headache!

I can see your controller EDIT (PUT) method expects 2 parameters: a) an int id, and b) a department object.

It is the default code when you generate this from VS > add controller with read/write options. However, you have to remember to consume this service using the two parameters, otherwise you will get the error 405.

In my case, I did not need the id parameter for PUT, so I just dropped it from the header... after a few hours of not noticing it there! If you keep it there, then the name must also be retained as id, unless you go on to make necessary changes to your configurations.

How do I import .sql files into SQLite 3?

Use sqlite3 database.sqlite3 < db.sql. You'll need to make sure that your files contain valid SQL for SQLite.

What's the best way to convert a number to a string in JavaScript?

The only valid solution for almost all possible existing and future cases (input is number, null, undefined, Symbol, anything else) is String(x). Do not use 3 ways for simple operation, basing on value type assumptions, like "here I convert definitely number to string and here definitely boolean to string".


String(x) handles nulls, undefined, Symbols, [anything] and calls .toString() for objects.

'' + x calls .valueOf() on x (casting to number), throws on Symbols, can provide implementation dependent results.

x.toString() throws on nulls and undefined.

Note: String(x) will still fail on prototype-less objects like Object.create(null).

If you don't like strings like 'Hello, undefined' or want to support prototype-less objects, use the following type conversion function:

 * Safely casts any value to string. Null and undefined are converted to ''.
 * @param  {*} value
 * @return {string}
function string (str) {
  return value == null ? '' : (typeof value === 'object' && !value.toString ? '[object]' : String(value));

T-SQL split string

ALTER FUNCTION [dbo].func_split_string
    @input as varchar(max),
    @delimiter as varchar(10) = ";"

    id smallint identity(1,1),
    csv_value varchar(max) not null
    DECLARE @pos AS INT;
    DECLARE @string AS VARCHAR(MAX) = '';

    WHILE LEN(@input) > 0
        SELECT @pos = CHARINDEX(@delimiter,@input);

            select @pos = len(@input)

        IF(@pos <> LEN(@input))
            SELECT @string = SUBSTRING(@input, 1, @pos-1);
            SELECT @string = SUBSTRING(@input, 1, @pos);

        INSERT INTO @result SELECT @string

        SELECT @input = SUBSTRING(@input, @pos+len(@delimiter), LEN(@input)-@pos)       

How do you create a dictionary in Java?

You'll want a Map<String, String>. Classes that implement the Map interface include (but are not limited to):

Each is designed/optimized for certain situations (go to their respective docs for more info). HashMap is probably the most common; the go-to default.

For example (using a HashMap):

Map<String, String> map = new HashMap<String, String>();
map.put("dog", "type of animal");
type of animal

Calling a JSON API with Node.js

Problems with other answers:

  • unsafe JSON.parse
  • no response code checking

All of the answers here use JSON.parse() in an unsafe way. You should always put all calls to JSON.parse() in a try/catch block especially when you parse JSON coming from an external source, like you do here.

You can use request to parse the JSON automatically which wasn't mentioned here in other answers. There is already an answer using request module but it uses JSON.parse() to manually parse JSON - which should always be run inside a try {} catch {} block to handle errors of incorrect JSON or otherwise the entire app will crash. And incorrect JSON happens, trust me.

Other answers that use http also use JSON.parse() without checking for exceptions that can happen and crash your application.

Below I'll show few ways to handle it safely.

All examples use a public GitHub API so everyone can try that code safely.

Example with request

Here's a working example with request that automatically parses JSON:

'use strict';
var request = require('request');

var url = '';

    url: url,
    json: true,
    headers: {'User-Agent': 'request'}
  }, (err, res, data) => {
    if (err) {
      console.log('Error:', err);
    } else if (res.statusCode !== 200) {
      console.log('Status:', res.statusCode);
    } else {
      // data is already parsed as JSON:

Example with http and try/catch

This uses https - just change https to http if you want HTTP connections:

'use strict';
var https = require('https');

var options = {
    host: '',
    path: '/users/rsp',
    headers: {'User-Agent': 'request'}

https.get(options, function (res) {
    var json = '';
    res.on('data', function (chunk) {
        json += chunk;
    res.on('end', function () {
        if (res.statusCode === 200) {
            try {
                var data = JSON.parse(json);
                // data is available here:
            } catch (e) {
                console.log('Error parsing JSON!');
        } else {
            console.log('Status:', res.statusCode);
}).on('error', function (err) {
      console.log('Error:', err);

Example with http and tryjson

This example is similar to the above but uses the tryjson module. (Disclaimer: I am the author of that module.)

'use strict';
var https = require('https');
var tryjson = require('tryjson');

var options = {
    host: '',
    path: '/users/rsp',
    headers: {'User-Agent': 'request'}

https.get(options, function (res) {
    var json = '';

    res.on('data', function (chunk) {
        json += chunk;

    res.on('end', function () {
        if (res.statusCode === 200) {
            var data = tryjson.parse(json);
            console.log(data ? data.html_url : 'Error parsing JSON!');
        } else {
            console.log('Status:', res.statusCode);
}).on('error', function (err) {
      console.log('Error:', err);


The example that uses request is the simplest. But if for some reason you don't want to use it then remember to always check the response code and to parse JSON safely.

Android - SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length

in my case i click on recent apps shortcut on my cell phone and close all apps. This solution always work for me, because this error not related to code.

How to specify multiple conditions in an if statement in javascript

if((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')) {

        PageCount= document.getElementById('<%=hfPageCount.ClientID %>').value;

This could be one of possible solutions, so 'or' is || not !!

How to initialize HashSet values by construction?

I feel the most readable is to simply use google Guava:

Set<String> StringSet = Sets.newSet("a", "b", "c");

Unable to resolve dependency for ':app@debug/compileClasspath': Could not resolve

For me the cause was incorrect url for jcenter. To solve it I simply changed url for app and proect level build.gradle


jcenter { url ""}



TypeError: worker() takes 0 positional arguments but 1 was given

Your worker method needs 'self' as a parameter, since it is a class method and not a function. Adding that should make it work fine.

Why doesn't importing java.util.* include Arrays and Lists?

The difference between

import java.util.*;


import java.util.*;
import java.util.List;
import java.util.Arrays;

becomes apparent when the code refers to some other List or Arrays (for example, in the same package, or also imported generally). In the first case, the compiler will assume that the Arrays declared in the same package is the one to use, in the latter, since it is declared specifically, the more specific java.util.Arrays will be used.

Various ways to remove local Git changes

Reason for adding an answer at this moment:

So far I was adding the conclusion and ‘answers’ to my initial question itself, making the question very lengthy, hence moving to separate answer.

I have also added more frequently used git commands that helps me on git, to help someone else too.

Basically to clean all local commits $ git reset --hard and $ git clean -d -f

First step before you do any commits is to configure your username and email that appears along with your commit.

#Sets the name you want attached to your commit transactions

$ git config --global "[name]"

#Sets the email you want atached to your commit transactions

$ git config --global "[email address]"

#List the global config

$ git config --list

#List the remote URL

$ git remote show origin

#check status

git status

#List all local and remote branches

git branch -a

#create a new local branch and start working on this branch

git checkout -b "branchname" 

or, it can be done as a two step process

create branch: git branch branchname work on this branch: git checkout branchname

#commit local changes [two step process:- Add the file to the index, that means adding to the staging area. Then commit the files that are present in this staging area]

git add <path to file>

git commit -m "commit message"

#checkout some other local branch

git checkout "local branch name"

#remove all changes in local branch [Suppose you made some changes in local branch like adding new file or modifying existing file, or making a local commit, but no longer need that] git clean -d -f and git reset --hard [clean all local changes made to the local branch except if local commit]

git stash -u also removes all changes

Note: It's clear that we can use either (1) combination of git clean –d –f and git reset --hard OR (2) git stash -u to achieve the desired result.

Note 1: Stashing, as the word means 'Store (something) safely and secretly in a specified place.' This can always be retreived using git stash pop. So choosing between the above two options is developer's call.

Note 2: git reset --hard will delete working directory changes. Be sure to stash any local changes you want to keep before running this command.

# Switch to the master branch and make sure you are up to date.

git checkout master

git fetch [this may be necessary (depending on your git config) to receive updates on origin/master ]

git pull

# Merge the feature branch into the master branch.

git merge feature_branch

# Reset the master branch to origin's state.

git reset origin/master

#Accidentally deleted a file from local , how to retrieve it back? Do a git status to get the complete filepath of the deleted resource

git checkout branchname <file path name>

that's it!

#Merge master branch with someotherbranch

git checkout master
git merge someotherbranchname

#rename local branch

git branch -m old-branch-name new-branch-name

#delete local branch

git branch -D branch-name

#delete remote branch

git push origin --delete branchname


git push origin :branch-name

#revert a commit already pushed to a remote repository

git revert hgytyz4567

#branch from a previous commit using GIT

git branch branchname <sha1-of-commit>

#Change commit message of the most recent commit that's already been pushed to remote

git commit --amend -m "new commit message"
git push --force origin <branch-name>

# Discarding all local commits on this branch [Removing local commits]

In order to discard all local commits on this branch, to make the local branch identical to the "upstream" of this branch, simply run

git reset --hard @{u}

Reference: or do git reset --hard origin/master [if local branch is master]

# Revert a commit already pushed to a remote repository?

$ git revert ab12cd15

#Delete a previous commit from local branch and remote branch

Use-Case: You just commited a change to your local branch and immediately pushed to the remote branch, Suddenly realized , Oh no! I dont need this change. Now do what?

git reset --hard HEAD~1 [for deleting that commit from local branch. 1 denotes the ONE commit you made]

git push origin HEAD --force [both the commands must be executed. For deleting from remote branch]. Currently checked out branch will be referred as the branch where you are making this operation.

#Delete some of recent commits from local and remote repo and preserve to the commit that you want. ( a kind of reverting commits from local and remote)

Let's assume you have 3 commits that you've pushed to remote branch named 'develop'

commitid-1 done at 9am
commitid-2 done at 10am
commitid-3 done at 11am. // latest commit. HEAD is current here.

To revert to old commit ( to change the state of branch)

git log --oneline --decorate --graph // to see all your commitids

git clean -d -f // clean any local changes

git reset --hard commitid-1 // locally reverting to this commitid

git push -u origin +develop // push this state to remote. + to do force push

# Remove local git merge: Case: I am on master branch and merged master branch with a newly working branch phase2

$ git status

On branch master

$ git merge phase2 $ git status

On branch master

Your branch is ahead of 'origin/master' by 8 commits.

Q: How to get rid of this local git merge? Tried git reset --hard and git clean -d -f Both didn't work. The only thing that worked are any of the below ones:

$ git reset --hard origin/master


$ git reset --hard HEAD~8


$ git reset --hard 9a88396f51e2a068bb7 [sha commit code - this is the one that was present before all your merge commits happened]

#create gitignore file

touch .gitignore // create the file in mac or unix users

sample .gitignore contents:


Reference link to GIT cheat sheet:

Regular expression for validating names and surnames?

You could use the following regex code to validate 2 names separeted by a space with the following regex code:

^[A-Za-zÀ-ú]+ [A-Za-zÀ-ú]+$

or just use:

[[:lower:]] = [a-zà-ú]

[[:upper:]] =[A-ZÀ-Ú]

[[:alpha:]] = [A-Za-zÀ-ú]

[[:alnum:]] = [A-Za-zÀ-ú0-9]

CSS: How to align vertically a "label" and "input" inside a "div"?

This works cross-browser, provides more accessibility and comes with less markup. ditch the div. Wrap the label

     display: block; 
     height: 35px; 
     line-height: 35px; 
     border: 1px solid #000; 

input{margin-top:15px; height:20px}

<label for="name">Name: <input type="text" id="name" /></label>

C++ Returning reference to local variable

This code snippet:

int& func1()
    int i;
    i = 1;
    return i;

will not work because you're returning an alias (a reference) to an object with a lifetime limited to the scope of the function call. That means once func1() returns, int i dies, making the reference returned from the function worthless because it now refers to an object that doesn't exist.

int main()
    int& p = func1();
    /* p is garbage */

The second version does work because the variable is allocated on the free store, which is not bound to the lifetime of the function call. However, you are responsible for deleteing the allocated int.

int* func2()
    int* p;
    p = new int;
    *p = 1;
    return p;

int main()
    int* p = func2();
    /* pointee still exists */
    delete p; // get rid of it

Typically you would wrap the pointer in some RAII class and/or a factory function so you don't have to delete it yourself.

In either case, you can just return the value itself (although I realize the example you provided was probably contrived):

int func3()
    return 1;

int main()
    int v = func3();
    // do whatever you want with the returned value

Note that it's perfectly fine to return big objects the same way func3() returns primitive values because just about every compiler nowadays implements some form of return value optimization:

class big_object 
    big_object(/* constructor arguments */);
    big_object(const big_object& rhs);
    big_object& operator=(const big_object& rhs);
    /* public methods */
    /* data members */

big_object func4()
    return big_object(/* constructor arguments */);

int main()
     // no copy is actually made, if your compiler supports RVO
    big_object o = func4();    

Interestingly, binding a temporary to a const reference is perfectly legal C++.

int main()
    // This works! The returned temporary will last as long as the reference exists
    const big_object& o = func4();    
    // This does *not* work! It's not legal C++ because reference is not const.
    // big_object& o = func4();  

Set Background cell color in PHPExcel

        'fill' => array(
            'type' => PHPExcel_Style_Fill::FILL_SOLID,
            'color' => array('rgb' => 'FF0000')


What is the difference between Serialization and Marshaling?

Marshalling is usually between relatively closely associated processes; serialization does not necessarily have that expectation. So when marshalling data between processes, for example, you may wish to merely send a REFERENCE to potentially expensive data to recover, whereas with serialization, you would wish to save it all, to properly recreate the object(s) when deserialized.

Sort a list of numerical strings in ascending order

The recommended approach in this case is to sort the data in the database, adding an ORDER BY at the end of the query that fetches the results, something like this:

SELECT temperature FROM temperatures ORDER BY temperature ASC;  -- ascending order
SELECT temperature FROM temperatures ORDER BY temperature DESC; -- descending order

If for some reason that is not an option, you can change the sorting order like this in Python:

templist = [25, 50, 100, 150, 200, 250, 300, 33]
sorted(templist, key=int)               # ascending order
> [25, 33, 50, 100, 150, 200, 250, 300]
sorted(templist, key=int, reverse=True) # descending order
> [300, 250, 200, 150, 100, 50, 33, 25]

As has been pointed in the comments, the int key (or float if values with decimals are being stored) is required for correctly sorting the data if the data received is of type string, but it'd be very strange to store temperature values as strings, if that is the case, go back and fix the problem at the root, and make sure that the temperatures being stored are numbers.

How to access the content of an iframe with jQuery?

If iframe's source is an external domain, browsers will hide the iframe contents (Same Origin Policy). A workaround is saving the external contents in a file, for example (in PHP):

    $contents = file_get_contents($external_url);
    $res = file_put_contents($filename, $contents);

then, get the new file content (string) and parse it to html, for example (in jquery):

$.get(file_url, function(string){
    var html = $.parseHTML(string);
    var contents = $(html).contents();

matplotlib error - no module named tkinter

For the poor guys like me using python 3.7. You need the python3.7-tk package.

sudo apt install python3.7-tk

$ python
Python 3.7.4 (default, Sep  2 2019, 20:44:09)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import tkinter
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'tkinter'
>>> exit()

Note. python3-tk is installed. But not python3.7-tk.

$ sudo apt install python3.7-tk
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  tix python3.7-tk-dbg
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 34 not upgraded.
Need to get 143 kB of archives.
After this operation, 534 kB of additional disk space will be used.
Get:1 xenial/main amd64 python3.7-tk amd64 3.7.4-1+xenial2 [143
Fetched 143 kB in 0s (364 kB/s)
Selecting previously unselected package python3.7-tk:amd64.
(Reading database ... 256375 files and directories currently installed.)
Preparing to unpack .../python3.7-tk_3.7.4-1+xenial2_amd64.deb ...
Unpacking python3.7-tk:amd64 (3.7.4-1+xenial2) ...
Setting up python3.7-tk:amd64 (3.7.4-1+xenial2) ...

After installing it, all good.

$ python3
Python 3.7.4 (default, Sep  2 2019, 20:44:09)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import tkinter
>>> exit()

Override browser form-filling and input highlighting with HTML/CSS

Autocomplete off is not supported by modern browsers. The easiest way to solve autocomplete I found was a little track with HTML and JS. The first thing to do is change the type of the input in HTML from 'password' to 'text'.

<input class="input input-xxl input-watery" type="text" name="password"/>

Autocomplete starts after window loaded. That's OK. But when the type of your field is not 'password', browser didn`t know what fields it must complete. So, there will be no autocomplete on form fields.

After that, bind event focusin to password field, for ex. in Backbone:

'focusin input[name=password]': 'onInputPasswordFocusIn',

In onInputPasswordFocusIn, just change the type of your field to password, by simple check:

if (e.currentTarget.value === '') {
    $(e.currentTarget).attr('type', 'password');

That`s it!

UPD: this thing doesn't work with disabled JavaSciprt

UPD in 2018. Also found some funny trick. Set readonly attribute to the input field, and remove it on the focus event. First prevent browser from autofilling fields, second will allow to input data.

What is difference between CrudRepository and JpaRepository interfaces in Spring Data JPA?

All the answers provide sufficient details to the question. However, let me add something more.

Why are we using these Interfaces:

  • They allow Spring to find your repository interfaces and create proxy objects for them.
  • It provides you with methods that allow you to perform some common operations (you can also define your custom method as well). I love this feature because creating a method (and defining query and prepared statements and then execute the query with connection object) to do a simple operation really sucks !

Which interface does what:

  • CrudRepository: provides CRUD functions
  • PagingAndSortingRepository: provides methods to do pagination and sort records
  • JpaRepository: provides JPA related methods such as flushing the persistence context and delete records in a batch

When to use which interface:

According to

Generally the best idea is to use CrudRepository or PagingAndSortingRepository depending on whether you need sorting and paging or not.

The JpaRepository should be avoided if possible, because it ties you repositories to the JPA persistence technology, and in most cases you probably wouldn’t even use the extra methods provided by it.

The application has stopped unexpectedly: How to Debug?

  1. From the Home screen, press the Menu key.
  2. List item
  3. Touch Settings.
  4. Touch Applications.
  5. Touch Manage Applications.
  6. Touch All.
  7. Select the application that is having issues.
  8. Touch Clear data and Clear cache if they are available. This resets the app as if it was new, and may delete personal data stored in the app.

What is the difference between canonical name, simple name and class name in Java Class?

If you're unsure about something, try writing a test first.

I did this:

class ClassNameTest {
    public static void main(final String... arguments) {
            "int.class (primitive)");
            "String.class (ordinary class)");
            "java.util.HashMap.SimpleEntry.class (nested class)");
            "new{}.getClass() (anonymous inner class)");

    private static void printNamesForClass(final Class<?> clazz, final String label) {
        System.out.println(label + ":");
        System.out.println("    getName():          " + clazz.getName());
        System.out.println("    getCanonicalName(): " + clazz.getCanonicalName());
        System.out.println("    getSimpleName():    " + clazz.getSimpleName());
        System.out.println("    getTypeName():      " + clazz.getTypeName()); // added in Java 8


int.class (primitive):
    getName():          int
    getCanonicalName(): int
    getSimpleName():    int
    getTypeName():      int

String.class (ordinary class):
    getName():          java.lang.String
    getCanonicalName(): java.lang.String
    getSimpleName():    String
    getTypeName():      java.lang.String

java.util.HashMap.SimpleEntry.class (nested class):
    getName():          java.util.AbstractMap$SimpleEntry
    getCanonicalName(): java.util.AbstractMap.SimpleEntry
    getSimpleName():    SimpleEntry
    getTypeName():      java.util.AbstractMap$SimpleEntry

new{}.getClass() (anonymous inner class):
    getName():          ClassNameTest$1
    getCanonicalName(): null
    getTypeName():      ClassNameTest$1

There's an empty entry in the last block where getSimpleName returns an empty string.

The upshot looking at this is:

  • the name is the name that you'd use to dynamically load the class with, for example, a call to Class.forName with the default ClassLoader. Within the scope of a certain ClassLoader, all classes have unique names.
  • the canonical name is the name that would be used in an import statement. It might be useful during toString or logging operations. When the javac compiler has complete view of a classpath, it enforces uniqueness of canonical names within it by clashing fully qualified class and package names at compile time. However JVMs must accept such name clashes, and thus canonical names do not uniquely identify classes within a ClassLoader. (In hindsight, a better name for this getter would have been getJavaName; but this method dates from a time when the JVM was used solely to run Java programs.)
  • the simple name loosely identifies the class, again might be useful during toString or logging operations but is not guaranteed to be unique.
  • the type name returns "an informative string for the name of this type", "It's like toString: it's purely informative and has no contract value". (as written by sir4ur0n)

How to config Tomcat to serve images from an external folder outside webapps?

Instead of configuring Tomcat to redirect requests, use Apache as a frontend with the Apache Tomcat connector so that Apache is only serving static content, while asking tomcat for dynamic content.

Using the JKmount directive (or others) you could specify exactly which requests are sent to Tomcat.

Requests for static content, such as images, would be served directly by Apache, using a standard virtual host configuration, while other requests, defined in the JKMount directive will be sent to Tomcat workers.

I think this implementation would give you the most flexibility and control on the overall application.

SCRIPT5: Access is denied in IE9 on xmlhttprequest

This error message (SCRIPT5: Access is denied.) can also be encountered if the target page of a .replace method is not found (I had entered the page name incorrectly). I know because it just happened to me, which is why I went searching for some more information about the meaning of the error message.

How do I get a python program to do nothing?

The pass command is what you are looking for. Use pass for any construct that you want to "ignore". Your example uses a conditional expression but you can do the same for almost anything.

For your specific use case, perhaps you'd want to test the opposite condition and only perform an action if the condition is false:

if num2 != num5:

This will be the same as this:

if num2 == num5:

That way you won't even have to use pass and you'll also be closer to adhering to the "Flatter is better than nested" convention in PEP20.

You can read more about the pass statement in the documentation:

The pass statement does nothing. It can be used when a statement is required syntactically but the program requires no action.

if condition:
except Exception:
    pass # do nothing
class Foo():
    pass # an empty class definition
def bar():
    pass # an empty function definition

Set equal width of columns in table layout in Android

Try this.

It boils down to adding android:stretchColumns="*" to your TableLayout root and setting android:layout_width="0dp" to all the children in your TableRows.

    android:stretchColumns="*"   // Optionally use numbered list "0,1,2,3,..."

Extract the maximum value within each group in a dataframe

Using sqldf and standard sql to get the maximum values grouped by another variable

sqldf("select max(Value),Gene from df1 group by Gene")


Using the excellent Hmisc package for a groupby application of function (max)


Warning: DOMDocument::loadHTML(): htmlParseEntityRef: expecting ';' in Entity,

I would bet that if you looked at the source of you would find special characters that haven't been converted to HTML. Maybe something like this:

<a href="/script.php?foo=bar&hello=world">link</a>

Should be

<a href="/script.php?foo=bar&amp;hello=world">link</a>

How to write "not in ()" sql query using join

I would opt for NOT EXISTS in this case.

SELECT D1.ShortCode
FROM Domain1 D1
    (SELECT 'X'
     FROM Domain2 D2
     WHERE D2.ShortCode = D1.ShortCode

Mockito verify order / sequence of method calls

Note that you can also use the InOrder class to verify that various methods are called in order on a single mock, not just on two or more mocks.

Suppose I have two classes Foo and Bar:

public class Foo {
  public void first() {}
  public void second() {}

public class Bar {
  public void firstThenSecond(Foo foo) {

I can then add a test class to test that Bar's firstThenSecond() method actually calls first(), then second(), and not second(), then first(). See the following test code:

public class BarTest {
  public void testFirstThenSecond() {
    Bar bar = new Bar();
    Foo mockFoo = Mockito.mock(Foo.class);

    InOrder orderVerifier = Mockito.inOrder(mockFoo);
    // These lines will PASS

    // These lines will FAIL
    // orderVerifier.verify(mockFoo).second();
    // orderVerifier.verify(mockFoo).first();

Format specifier %02x

%x is a format specifier that format and output the hex value. If you are providing int or long value, it will convert it to hex value.

%02x means if your provided value is less than two digits then 0 will be prepended.

You provided value 16843009 and it has been converted to 1010101 which a hex value.

Is there a way to get the source code from an APK file?

Simple way: use online tool, upload apk and get source code.

Procedure for decoding .apk files, step-by-step method:

Step 1:

  1. Make a new folder and copy over the .apk file that you want to decode.

  2. Now rename the extension of this .apk file to .zip (e.g. rename from filename.apk to and save it. Now you can access the classes.dex files, etc. At this stage you are able to see drawables but not xml and java files, so continue.

Step 2:

  1. Now extract this .zip file in the same folder (or NEW FOLDER).

  2. Download dex2jar and extract it to the same folder (or NEW FOLDER).

  3. Move the classes.dex file into the dex2jar folder.

  4. Now open command prompt and change directory to that folder (or NEW FOLDER). Then write d2j-dex2jar classes.dex (for mac terminal or ubuntu write ./ classes.dex) and press enter. You now have the classes.dex.dex2jar file in the same folder.

  5. Download java decompiler, double click on jd-gui, click on open file, and open classes.dex.dex2jar file from that folder: now you get class files.

  6. Save all of these class files (In jd-gui, click File -> Save All Sources) by src name. At this stage you get the java source but the .xml files are still unreadable, so continue.

Step 3:

Now open another new folder

  1. Put in the .apk file which you want to decode

  2. Download the latest version of apktool AND apktool install window (both can be downloaded from the same link) and place them in the same folder

  3. Open a command window

  4. Now run command like apktool if framework-res.apk (if you don't have it get it here)and next

  5. apktool d myApp.apk (where myApp.apk denotes the filename that you want to decode)

now you get a file folder in that folder and can easily read the apk's xml files.

Step 4:

It's not any step, just copy contents of both folders(in this case, both new folders) to the single one

and enjoy the source code...

How can I increase the JVM memory?

When calling java use the -Xmx Flag for example -Xmx512m for 512 megs for the heap size. You may also want to consider the -xms flag to start the heap larger if you are going to have it grow right from the start. The default size is 128megs.

How are POST and GET variables handled in Python?

Python is only a language, to get GET and POST data, you need a web framework or toolkit written in Python. Django is one, as Charlie points out, the cgi and urllib standard modules are others. Also available are Turbogears, Pylons, CherryPy,, mod_python, fastcgi, etc, etc.

In Django, your view functions receive a request argument which has request.GET and request.POST. Other frameworks will do it differently.

Better way to get type of a Javascript variable?

I guess the most universal solution here - is to check for undefined and null first, then just call

const getType = v =>
  v === undefined
    ? 'undefined'
    : v === null
      ? 'null'

console.log(getType(undefined)); // 'undefined'
console.log(getType(null)); // 'null'
console.log(getType('')); // 'string'
console.log(getType([])); // 'array'
console.log(getType({})); // 'object'
console.log(getType(new Set())); // `set'
console.log(getType(Promise.resolve())); // `promise'
console.log(getType(new Map())); // `map'

How can I check if a string only contains letters in Python?

(1) Use str.isalpha() when you print the string.

(2) Please check below program for your reference:-

 str = "this";  # No space & digit in this string
 print str.isalpha() # it gives return True

 str = "this is 2";
 print str.isalpha() # it gives return False

Note:- I checked above example in Ubuntu.

python: How do I know what type of exception occurred?

The actual exception can be captured in the following way:

    i = 1/0
except Exception as e:
    print e

You can learn more about exceptions from The Python Tutorial.

JavaScript set object key by variable

In ES6, you can do like this.

var key = "name";
var person = {[key]:"John"}; // same as var person = {"name" : "John"}
console.log(person); // should print  Object { name="John"}

    var key = "name";_x000D_
    var person = {[key]:"John"};_x000D_
    console.log(person); // should print  Object { name="John"}

Its called Computed Property Names, its implemented using bracket notation( square brackets) []

Example: { [variableName] : someValue }

Starting with ECMAScript 2015, the object initializer syntax also supports computed property names. That allows you to put an expression in brackets [], that will be computed and used as the property name.

For ES5, try something like this

var yourObject = {};

yourObject[yourKey] = "yourValue";

console.log(yourObject );


var person = {};
var key = "name";

person[key] /* this is same as */ = "John";

console.log(person); // should print  Object { name="John"}

    var person = {};_x000D_
    var key = "name";_x000D_
    person[key] /* this is same as */ = "John";_x000D_
    console.log(person); // should print  Object { name="John"}

List of installed gems?

There's been a method for this for ages:

ruby -e 'puts Gem::Specification.all_names'

Declare a variable in DB2 SQL

I imagine this forum posting, which I quote fully below, should answer the question.

Inside a procedure, function, or trigger definition, or in a dynamic SQL statement (embedded in a host program):

 DECLARE example VARCHAR(15) ;
 SET example = 'welcome' ;
 FROM   tablename
 WHERE  column1 = example ;

or (in any environment):

WITH t(example) AS (VALUES('welcome'))
FROM   tablename, t
WHERE  column1 = example

or (although this is probably not what you want, since the variable needs to be created just once, but can be used thereafter by everybody although its content will be private on a per-user basis):

SET example = 'welcome' ;
FROM   tablename
WHERE  column1 = example ;

JavaScript check if variable exists (is defined/initialized)

The highest answer is correct, use typeof.

However, what I wanted to point out was that in JavaScript undefined is mutable (for some ungodly reason). So simply doing a check for varName !== undefined has the potential to not always return as you expect it to, because other libs could have changed undefined. A few answers (@skalee's, for one), seem to prefer not using typeof, and that could get one into trouble.

The "old" way to handle this was declaring undefined as a var to offset any potential muting/over-riding of undefined. However, the best way is still to use typeof because it will ignore any overriding of undefined from other code. Especially if you are writing code for use in the wild where who knows what else could be running on the page...

Calling constructors in c++ without new

I assume with the second line you actually mean:

Thing *thing = new Thing("uiae");

which would be the standard way of creating new dynamic objects (necessary for dynamic binding and polymorphism) and storing their address to a pointer. Your code does what JaredPar described, namely creating two objects (one passed a const char*, the other passed a const Thing&), and then calling the destructor (~Thing()) on the first object (the const char* one).

By contrast, this:

Thing thing("uiae");

creates a static object which is destroyed automatically upon exiting the current scope.

append multiple values for one key in a dictionary

You would be best off using collections.defaultdict (added in Python 2.5). This allows you to specify the default object type of a missing key (such as a list).

So instead of creating a key if it doesn't exist first and then appending to the value of the key, you cut out the middle-man and just directly append to non-existing keys to get the desired result.

A quick example using your data:

>>> from collections import defaultdict
>>> data = [(2010, 2), (2009, 4), (1989, 8), (2009, 7)]
>>> d = defaultdict(list)
>>> d
defaultdict(<type 'list'>, {})
>>> for year, month in data:
...     d[year].append(month)
>>> d
defaultdict(<type 'list'>, {2009: [4, 7], 2010: [2], 1989: [8]})

This way you don't have to worry about whether you've seen a digit associated with a year or not. You just append and forget, knowing that a missing key will always be a list. If a key already exists, then it will just be appended to.

Loop through a Map with JSTL

You can loop through a hash map like this

ArrayList list = new ArrayList();
TreeMap itemList=new TreeMap();
itemList.put("test", "test");
pageContext.setAttribute("itemList", list);                            

  <c:forEach items="${itemList}" var="itemrow">
   <input  type="text"  value="<c:out value='${itemrow.test}'/>"/>

For more JSTL functionality look here

Labeling file upload button

You get your browser's language for your button. There's no way to change it programmatically.

global variable for all controller and views

Most popular answers here with BaseController didn't worked for me on Laravel 5.4, but they have worked on 5.3. No idea why.

I have found a way which works on Laravel 5.4 and gives variables even for views which are skipping controllers. And, of course, you can get variables from the database.

add in your app/Providers/AppServiceProvider.php

class AppServiceProvider extends ServiceProvider
    public function boot()
        // Using view composer to set following variables globally
        view()->composer('*',function($view) {
            $view->with('user', Auth::user());
            $view->with('social', Social::all()); 
            // if you need to access in controller and views:
            Config::set('something', $something); 


Advantages of std::for_each over for loop

Mostly you'll have to iterate over the whole collection. Therefore I suggest you write your own for_each() variant, taking only 2 parameters. This will allow you to rewrite Terry Mahaffey's example as:

for_each(container, [](int& i) {
    i += 10;

I think this is indeed more readable than a for loop. However, this requires the C++0x compiler extensions.

PermissionError: [Errno 13] Permission denied

Here is how I encountered the error:

import os

path = input("Input file path: ")

name, ext = os.path.basename(path).rsplit('.', 1)
dire = os.path.dirname(path)

with open(f"{dire}\\{name} temp.{ext}", 'wb') as file:

It works great if the user inputs a file path with more than one element, like


But I thought that it would work with an input like


as long as file.txt is in the same directory of the python file. But nope, it gave me that error, and I realized that the correct input should've been


Is there a job scheduler library for node.js?

I am the auhor of node-runnr . It have a very simple approach to create job. Also its very easy and clear to declare time and interval. For example, to execute a job at every 10min 20sec,

Runnr.addIntervalJob('10:20', function(){...}, 'myjob')

To do a job at 10am and 3pm daily,

Runnr.addDailyJob(['10:0:0', '15:0:0'], function(){...}, 'myjob')

Its that simple. For further detail:

Render basic HTML view?

For plain html you don't require any npm package or middleware

just use this:

app.get('/', function(req, res) {

What does LINQ return when the results are empty

It won't throw exception, you'll get an empty list.

Exception is never thrown in body of corresponding try statement

A catch-block in a try statement needs to catch exactly the exception that the code inside the try {}-block can throw (or a super class of that).

try {
    //do something that throws ExceptionA, e.g.
    throw new ExceptionA("I am Exception Alpha!");
catch(ExceptionA e) {
    //do something to handle the exception, e.g.
    System.out.println("Message: " + e.getMessage());

What you are trying to do is this:

try {
    throw new ExceptionB("I am Exception Bravo!");
catch(ExceptionA e) {
    System.out.println("Message: " + e.getMessage());

This will lead to an compiler error, because your java knows that you are trying to catch an exception that will NEVER EVER EVER occur. Thus you would get: exception ExceptionA is never thrown in body of corresponding try statement.

What USB driver should we use for the Nexus 5?

I installed the LG United Mobile Driver, and I was finally able to get ADB to recognize my device.

How can I print out just the index of a pandas dataframe?

You can access the index attribute of a df using df.index[i]

>> import pandas as pd
>> import numpy as np
>> df = pd.DataFrame({'a':np.arange(5), 'b':np.random.randn(5)})
   a         b
0  0  1.088998
1  1 -1.381735
2  2  0.035058
3  3 -2.273023
4  4  1.345342

>> df.index[1] ## Second index
>> df.index[-1] ## Last index

>> for i in xrange(len(df)):print df.index[i] ## Using loop

How to compare arrays in C#?

You can use the Enumerable.SequenceEqual() in the System.Linq to compare the contents in the array

bool isEqual = Enumerable.SequenceEqual(target1, target2);

What does "|=" mean? (pipe equal operator)

|= reads the same way as +=.

notification.defaults |= Notification.DEFAULT_SOUND;

is the same as

notification.defaults = notification.defaults | Notification.DEFAULT_SOUND;

where | is the bit-wise OR operator.

All operators are referenced here.

A bit-wise operator is used because, as is frequent, those constants enable an int to carry flags.

If you look at those constants, you'll see that they're in powers of two :

public static final int DEFAULT_SOUND = 1;
public static final int DEFAULT_VIBRATE = 2; // is the same than 1<<1 or 10 in binary
public static final int DEFAULT_LIGHTS = 4; // is the same than 1<<2 or 100 in binary

So you can use bit-wise OR to add flags

int myFlags = DEFAULT_SOUND | DEFAULT_VIBRATE; // same as 001 | 010, producing 011



simply means we add a flag.

And symmetrically, we test a flag is set using & :

boolean hasVibrate = (DEFAULT_VIBRATE & myFlags) != 0;

Pass array to mvc Action via AJAX

Quite a late, but different answer to the ones already present here:

If instead of $.ajax you'd like to use shorthand functions $.get or $.post, you can pass arrays this way:

Shorthand GET

var array = [1, 2, 3, 4, 5];
$.get('/controller/MyAction', $.param({ data: array }, true), function(data) {});

// Action Method
public void MyAction(List<int> data)
    // do stuff here

Shorthand POST

var array = [1, 2, 3, 4, 5];
$.post('/controller/MyAction', $.param({ data: array }, true), function(data) {});

// Action Method
public void MyAction(List<int> data)
    // do stuff here


  • The boolean parameter in $.param is for the traditional property, which MUST be true for this to work.

Enter key press behaves like a Tab in Javascript

$("#form input , select , textarea").keypress(function(e){
    if(e.keyCode == 13){
        var enter_position = $(this).index();
        $("#form input , select , textarea").eq(enter_position+1).focus();

File count from a folder

To get the count of certain type extensions using LINQ you could use this simple code:

Dim exts() As String = {".docx", ".ppt", ".pdf"}

Dim query = (From f As FileInfo In directory.GetFiles()).Where(Function(f) exts.Contains(f.Extension.ToLower()))


Flatten list of lists

Flatten the list to "remove the brackets" using a nested list comprehension. This will un-nest each list stored in your list of lists!

list_of_lists = [[180.0], [173.8], [164.2], [156.5], [147.2], [138.2]]
flattened = [val for sublist in list_of_lists for val in sublist]

Nested list comprehensions evaluate in the same manner that they unwrap (i.e. add newline and tab for each new loop. So in this case:

flattened = [val for sublist in list_of_lists for val in sublist]

is equivalent to:

flattened = []
for sublist in list_of_lists:
    for val in sublist:

The big difference is that the list comp evaluates MUCH faster than the unraveled loop and eliminates the append calls!

If you have multiple items in a sublist the list comp will even flatten that. ie

>>> list_of_lists = [[180.0, 1, 2, 3], [173.8], [164.2], [156.5], [147.2], [138.2]]
>>> flattened  = [val for sublist in list_of_lists for val in sublist]
>>> flattened 
[180.0, 1, 2, 3, 173.8, 164.2, 156.5, 147.2,138.2]

What's the difference between eval, exec, and compile?

  1. exec is not an expression: a statement in Python 2.x, and a function in Python 3.x. It compiles and immediately evaluates a statement or set of statement contained in a string. Example:

     exec('print(5)')           # prints 5.
     # exec 'print 5'     if you use Python 2.x, nor the exec neither the print is a function there
     exec('print(5)\nprint(6)')  # prints 5{newline}6.
     exec('if True: print(6)')  # prints 6.
     exec('5')                 # does nothing and returns nothing.
  2. eval is a built-in function (not a statement), which evaluates an expression and returns the value that expression produces. Example:

     x = eval('5')              # x <- 5
     x = eval('%d + 6' % x)     # x <- 11
     x = eval('abs(%d)' % -100) # x <- 100
     x = eval('x = 5')          # INVALID; assignment is not an expression.
     x = eval('if 1: x = 4')    # INVALID; if is a statement, not an expression.
  3. compile is a lower level version of exec and eval. It does not execute or evaluate your statements or expressions, but returns a code object that can do it. The modes are as follows:

  4. compile(string, '', 'eval') returns the code object that would have been executed had you done eval(string). Note that you cannot use statements in this mode; only a (single) expression is valid.

  5. compile(string, '', 'exec') returns the code object that would have been executed had you done exec(string). You can use any number of statements here.

  6. compile(string, '', 'single') is like the exec mode but expects exactly one expression/statement, eg compile('a=1 if 1 else 3', 'myf', mode='single')

Java naming convention for static final variables

The dialog on this seems to be the antithesis of the conversation on naming interface and abstract classes. I find this alarming, and think that the decision runs much deeper than simply choosing one naming convention and using it always with static final.

Abstract and Interface

When naming interfaces and abstract classes, the accepted convention has evolved into not prefixing or suffixing your abstract class or interface with any identifying information that would indicate it is anything other than a class.

public interface Reader {}
public abstract class FileReader implements Reader {}
public class XmlFileReader extends FileReader {}

The developer is said not to need to know that the above classes are abstract or an interface.

Static Final

My personal preference and belief is that we should follow similar logic when referring to static final variables. Instead, we evaluate its usage when determining how to name it. It seems the all uppercase argument is something that has been somewhat blindly adopted from the C and C++ languages. In my estimation, that is not justification to continue the tradition in Java.

Question of Intention

We should ask ourselves what is the function of static final in our own context. Here are three examples of how static final may be used in different contexts:

public class ChatMessage {
    //Used like a private variable
    private static final Logger logger = LoggerFactory.getLogger(XmlFileReader.class);

    //Used like an Enum
    public class Error {
        public static final int Success = 0;
        public static final int TooLong = 1;
        public static final int IllegalCharacters = 2;

    //Used to define some static, constant, publicly visible property
    public static final int MAX_SIZE = Integer.MAX_VALUE;

Could you use all uppercase in all three scenarios? Absolutely, but I think it can be argued that it would detract from the purpose of each. So, let's examine each case individually.

Purpose: Private Variable

In the case of the Logger example above, the logger is declared as private, and will only be used within the class, or possibly an inner class. Even if it were declared at protected or package visibility, its usage is the same:

public void send(final String message) {"Sending the following message: '" + message + "'.");
    //Send the message

Here, we don't care that logger is a static final member variable. It could simply be a final instance variable. We don't know. We don't need to know. All we need to know is that we are logging the message to the logger that the class instance has provided.

public class ChatMessage {
    private final Logger logger = LoggerFactory.getLogger(getClass());

You wouldn't name it LOGGER in this scenario, so why should you name it all uppercase if it was static final? Its context, or intention, is the same in both circumstances.

Note: I reversed my position on package visibility because it is more like a form of public access, restricted to package level.

Purpose: Enum

Now you might say, why are you using static final integers as an enum? That is a discussion that is still evolving and I'd even say semi-controversial, so I'll try not to derail this discussion for long by venturing into it. However, it would be suggested that you could implement the following accepted enum pattern:

public enum Error {

    private final int value;

    private Error(final int value) {
        this.value = value;

    public int value() {
        return value;

    public static Error fromValue(final int value) {
        switch (value) {
        case 0:
            return Error.Success;
        case 1:
            return Error.TooLong;
        case 2:
            return Error.IllegalCharacters;
            throw new IllegalArgumentException("Unknown Error value.");

There are variations of the above that achieve the same purpose of allowing explicit conversion of an enum->int and int->enum. In the scope of streaming this information over a network, native Java serialization is simply too verbose. A simple int, short, or byte could save tremendous bandwidth. I could delve into a long winded compare and contrast about the pros and cons of enum vs static final int involving type safety, readability, maintainability, etc.; fortunately, that lies outside the scope of this discussion.

The bottom line is this, sometimes static final int will be used as an enum style structure.

If you can bring yourself to accept that the above statement is true, we can follow that up with a discussion of style. When declaring an enum, the accepted style says that we don't do the following:

public enum Error {

Instead, we do the following:

public enum Error {

If your static final block of integers serves as a loose enum, then why should you use a different naming convention for it? Its context, or intention, is the same in both circumstances.

Purpose: Static, Constant, Public Property

This usage case is perhaps the most cloudy and debatable of all. The static constant size usage example is where this is most often encountered. Java removes the need for sizeof(), but there are times when it is important to know how many bytes a data structure will occupy.

For example, consider you are writing or reading a list of data structures to a binary file, and the format of that binary file requires that the total size of the data chunk be inserted before the actual data. This is common so that a reader knows when the data stops in the scenario that there is more, unrelated, data that follows. Consider the following made up file format:

File Format: MyFormat (MYFM) for example purposes only
[int filetype: MYFM]
[int version: 0] //0 - Version of MyFormat file format
[int dataSize: 325] //The data section occupies the next 325 bytes
[int checksumSize: 400] //The checksum section occupies 400 bytes after the data section (16 bytes each)
[byte[] data]
[byte[] checksum]

This file contains a list of MyObject objects serialized into a byte stream and written to this file. This file has 325 bytes of MyObject objects, but without knowing the size of each MyObject you have no way of knowing which bytes belong to each MyObject. So, you define the size of MyObject on MyObject:

public class MyObject {
    private final long id; //It has a 64bit identifier (+8 bytes)
    private final int value; //It has a 32bit integer value (+4 bytes)
    private final boolean special; //Is it special? (+1 byte)

    public static final int SIZE = 13; //8 + 4 + 1 = 13 bytes

The MyObject data structure will occupy 13 bytes when written to the file as defined above. Knowing this, when reading our binary file, we can figure out dynamically how many MyObject objects follow in the file:

int dataSize = buffer.getInt();
int totalObjects = dataSize / MyObject.SIZE;

This seems to be the typical usage case and argument for all uppercase static final constants, and I agree that in this context, all uppercase makes sense. Here's why:

Java doesn't have a struct class like the C language, but a struct is simply a class with all public members and no constructor. It's simply a data structure. So, you can declare a class in struct like fashion:

public class MyFile {
    public static final int MYFM = 0x4D59464D; //'MYFM' another use of all uppercase!

    //The struct
    public static class MyFileHeader {
        public int fileType = MYFM;
        public int version = 0;
        public int dataSize = 0;
        public int checksumSize = 0;

Let me preface this example by stating I personally wouldn't parse in this manner. I'd suggest an immutable class instead that handles the parsing internally by accepting a ByteBuffer or all 4 variables as constructor arguments. That said, accessing (setting in this case) this structs members would look something like:

MyFileHeader header = new MyFileHeader();
header.fileType     = buffer.getInt();
header.version      = buffer.getInt();
header.dataSize     = buffer.getInt();
header.checksumSize = buffer.getInt();

These aren't static or final, yet they are publicly exposed members that can be directly set. For this reason, I think that when a static final member is exposed publicly, it makes sense to uppercase it entirely. This is the one time when it is important to distinguish it from public, non-static variables.

Note: Even in this case, if a developer attempted to set a final variable, they would be met with either an IDE or compiler error.


In conclusion, the convention you choose for static final variables is going to be your preference, but I strongly believe that the context of use should heavily weigh on your design decision. My personal recommendation would be to follow one of the two methodologies:

Methodology 1: Evaluate Context and Intention [highly subjective; logical]

  • If it's a private variable that should be indistinguishable from a private instance variable, then name them the same. all lowercase
  • If it's intention is to serve as a type of loose enum style block of static values, then name it as you would an enum. pascal case: initial-cap each word
  • If it's intention is to define some publicly accessible, constant, and static property, then let it stand out by making it all uppercase

Methodology 2: Private vs Public [objective; logical]

Methodology 2 basically condenses its context into visibility, and leaves no room for interpretation.

  • If it's private or protected then it should be all lowercase.
  • If it's public or package then it should be all uppercase.


This is how I view the naming convention of static final variables. I don't think it is something that can or should be boxed into a single catch all. I believe that you should evaluate its intent before deciding how to name it.

However, the main objective should be to try and stay consistent throughout your project/package's scope. In the end, that is all you have control over.

(I do expect to be met with resistance, but also hope to gather some support from the community on this approach. Whatever your stance, please keep it civil when rebuking, critiquing, or acclaiming this style choice.)

How to combine GROUP BY and ROW_NUMBER?

;with C as
  select Rel.t2ID,
         row_number() over(partition by Rel.t2ID order by t1.Price desc) as rn
  from @t1 as T1
    inner join @relation as Rel
      on T1.ID = Rel.t1ID
select T2.ID as T2ID,
       T2.Name as T2Name,
       T1.ID as T1ID,
       T1.Name as T1Name,
from @t2 as T2
  inner join (
              select C1.t2ID,
                     sum(C1.Price) as Price,
              from C as C1
                inner join C as C2 
                  on C1.t2ID = C2.t2ID and
                     C2.rn = 1
              group by C1.t2ID, C2.t1ID
             ) as T1Sum
    on T2.ID = T1Sum.t2ID
  inner join @t1 as T1
    on T1.ID = T1Sum.t1ID

Parse String to Date with Different Format in Java

Suppose that you have a string like this :

String mDate="2019-09-17T10:56:07.827088"

Now we want to change this String format separate date and time in Java and Kotlin.


we have a method for extract date :

public String getDate() {
    try {
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
        Date date = dateFormat.parse(mDate);
        dateFormat = new SimpleDateFormat("MM/dd/yyyy", Locale.US);
        return dateFormat.format(date);
    } catch (ParseException e) {
    return null;

Return is this : 09/17/2019

And we have method for extract time :

public String getTime() {

    try {
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
        Date date = dateFormat.parse(mCreatedAt);
        dateFormat = new SimpleDateFormat("h:mm a", Locale.US);
        return dateFormat.format(date);
    } catch (ParseException e) {
    return null;

Return is this : 10:56 AM


we have a function for extract date :

fun getDate(): String? {

    var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
    val date = dateFormat.parse(mDate!!)
    dateFormat = SimpleDateFormat("MM/dd/yyyy", Locale.US)
    return dateFormat.format(date!!)

Return is this : 09/17/2019

And we have method for extract time :

fun getTime(): String {

    var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
    val time = dateFormat.parse(mDate!!)
    dateFormat = SimpleDateFormat("h:mm a", Locale.US)
    return dateFormat.format(time!!)

Return is this : 10:56 AM

How to add months to a date in JavaScript?

I would highly recommend taking a look at datejs. With it's api, it becomes drop dead simple to add a month (and lots of other date functionality):

var one_month_from_your_date = your_date_object.add(1).month();

What's nice about datejs is that it handles edge cases, because technically you can do this using the native Date object and it's attached methods. But you end up pulling your hair out over edge cases, which datejs has taken care of for you.

Plus it's open source!

Classes vs. Functions

Classes (or rather their instances) are for representing things. Classes are used to define the operations supported by a particular class of objects (its instances). If your application needs to keep track of people, then Person is probably a class; the instances of this class represent particular people you are tracking.

Functions are for calculating things. They receive inputs and produce an output and/or have effects.

Classes and functions aren't really alternatives, as they're not for the same things. It doesn't really make sense to consider making a class to "calculate the age of a person given his/her birthday year and the current year". You may or may not have classes to represent any of the concepts of Person, Age, Year, and/or Birthday. But even if Age is a class, it shouldn't be thought of as calculating a person's age; rather the calculation of a person's age results in an instance of the Age class.

If you are modelling people in your application and you have a Person class, it may make sense to make the age calculation be a method of the Person class. A method is basically a function which is defined as part of a class; this is how you "define the operations supported by a particular class of objects" as I mentioned earlier.

So you could create a method on your person class for calculating the age of the person (it would probably retrieve the birthday year from the person object and receive the current year as a parameter). But the calculation is still done by a function (just a function that happens to be a method on a class).

Or you could simply create a stand-alone function that receives arguments (either a person object from which to retrieve a birth year, or simply the birth year itself). As you note, this is much simpler if you don't already have a class where this method naturally belongs! You should never create a class simply to hold an operation; if that's all there is to the class then the operation should just be a stand-alone function.

How to attach a file using mail command on Linux?

Example using uuencode:

uuencode surfing.jpeg surfing.jpeg | mail [email protected]

and reference article:


you may apt install sharutils to have uuencode command

What's the difference between a null pointer and a void pointer?

Null pointers and void pointers are completely different from each other. If we request the operating system(through malloc() in c langauge) to allocate memory for a particular data type then the operating system allocates memory in heap (if space is available in heap) and sends the address of the memory which was allocated.

When memory is allocated by os in heap then we can assign this address value in any pointer type variable of that data type. This pointer is then called a void pointer until it is not taken for any process.

When the space is not available in heap then the operating system certainly allocates memory and sends an address value of that location but this memory is not allocated in heap by the os because there is no space in heap,in this case this memory is allocated by the os in the system memory.. This memory can not be accessed by the user hence when we assign this address value in a pointer then this pointer is known as null pointer, and we cannot use this pointer. In the case of void pointer we can use it for any process in any programming language.

Could not load file or assembly 'Newtonsoft.Json, Version=, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed'

I was getting same error and by adding below code error resolved on production.

Answer is too late but might help someone.

        <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
                <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
                <bindingRedirect oldVersion="" newVersion="" />

PHP MySQL Google Chart JSON - Complete Example

Some might encounter this error either locally or on the server:

syntax error var data = new google.visualization.DataTable(<?=$jsonTable?>);

This means that their environment does not support short tags the solution is to use this instead:

<?php echo $jsonTable; ?>

And everything should work fine!

How to connect access database in c#

You are building a DataGridView on the fly and set the DataSource for it. That's good, but then do you add the DataGridView to the Controls collection of the hosting form?


By the way the code is a bit confused

String connection = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\\Tables.accdb;Persist Security Info=True";
string sql  = "SELECT Clients  FROM Tables";
using(OleDbConnection conn = new OleDbConnection(connection))
     DataSet ds = new DataSet();
     DataGridView dataGridView1 = new DataGridView();
     using(OleDbDataAdapter adapter = new OleDbDataAdapter(sql,conn))
         dataGridView1.DataSource = ds;
         // Of course, before addint the datagrid to the hosting form you need to 
         // set position, location and other useful properties. 
         // Why don't you create the DataGrid with the designer and use that instance instead?

EDIT After the comments below it is clear that there is a bit of confusion between the file name (TABLES.ACCDB) and the name of the table CLIENTS.
The SELECT statement is defined (in its basic form) as

 SELECT field_names_list FROM _tablename_

so the correct syntax to use for retrieving all the clients data is

 string sql  = "SELECT * FROM Clients";

where the * means -> all the fields present in the table

Change Image of ImageView programmatically in Android

In XML Design


Drawable Image via code


Server image

  ## Dependency ##

  implementation 'com.github.bumptech.glide:glide:4.7.1'
  annotationProcessor 'com.github.bumptech.glide:compiler:4.7.1'

  Glide.with(context).load(url) .placeholder(R.drawable.image)

 ## dependency  ##
 implementation 'com.squareup.picasso:picasso:2.71828'

 Picasso.with(context).load(url) .placeholder(R.drawable.image)

Delete from a table based on date

Delete data that is 30 days and older

   WHERE DateColumn < GETDATE()- 30

How do you get a directory listing sorted by creation date in python?

# *** the shortest and best way ***
# getmtime --> sort by modified time
# getctime --> sort by created time

import glob,os

lst_files = glob.glob("*.txt")

Compare 2 JSON objects

Simply parsing the JSON and comparing the two objects is not enough because it wouldn't be the exact same object references (but might be the same values).

You need to do a deep equals.

From - which seems the use jQuery.

Object.extend(Object, {
   deepEquals: function(o1, o2) {
     var k1 = Object.keys(o1).sort();
     var k2 = Object.keys(o2).sort();
     if (k1.length != k2.length) return false;
     return, function(keyPair) {
       if(typeof o1[keyPair[0]] == typeof o2[keyPair[1]] == "object"){
         return deepEquals(o1[keyPair[0]], o2[keyPair[1]])
       } else {
         return o1[keyPair[0]] == o2[keyPair[1]];


var anObj = JSON.parse(jsonString1);
var anotherObj= JSON.parse(jsonString2);

if (Object.deepEquals(anObj, anotherObj))

ERROR 1064 (42000) in MySQL

I had this, and it was the create syntax, changed to --create-options and life was better

mysqldump -u [user] -p -create-options [DBNAME] >[DumpFile].sql

And that restored nicely.

Apply style to parent if it has child with css

It's not possible with CSS3. There is a proposed CSS4 selector, $, to do just that, which could look like this (Selecting the li element):

ul $li ul.sub { ... }

See the list of CSS4 Selectors here.

As an alternative, with jQuery, a one-liner you could make use of would be this:

$('ul li:has(ul.sub)').addClass('has_sub');

You could then go ahead and style the li.has_sub in your CSS.

SQL Server 2008 Insert with WHILE LOOP

Assuming that ID is an identity column:

INSERT INTO TheTable(HospitalID, Email, Description)
SELECT 32, Email, Description FROM TheTable
WHERE HospitalID <> 32

Try to avoid loops with SQL. Try to think in terms of sets instead.

How to convert Double to int directly?

If you really should use Double instead of double you even can get the int Value of Double by calling:

Double d = new Double(1.23);
int i = d.intValue();

Else its already described by Peter Lawreys answer.

Java socket API: How to tell if a connection has been closed?

On Linux when write()ing into a socket which the other side, unknown to you, closed will provoke a SIGPIPE signal/exception however you want to call it. However if you don't want to be caught out by the SIGPIPE you can use send() with the flag MSG_NOSIGNAL. The send() call will return with -1 and in this case you can check errno which will tell you that you tried to write a broken pipe (in this case a socket) with the value EPIPE which according to errno.h is equivalent to 32. As a reaction to the EPIPE you could double back and try to reopen the socket and try to send your information again.

Difference between return 1, return 0, return -1 and exit?

return n from your main entry function will terminate your process and report to the parent process (the one that executed your process) the result of your process. 0 means SUCCESS. Other codes usually indicates a failure and its meaning.

SQL Connection Error: System.Data.SqlClient.SqlException (0x80131904)

I had the same issue.

Make sure that In SQL Server configuration --> SQL Server Services --> SQL Server Agent is enable

This solved my problem

Disable ScrollView Programmatically?

I may be late but still...

This answer is based on removing and adding views dynamically

To disable scrolling:

View child = scoll.getChildAt(0);// since scrollView can only have one direct child
ViewGroup parent = (ViewGroup) scroll.getParent();
scroll.removeView(child); // remove child from scrollview
parent.addView(child,parent.indexOfChild(scroll));// add scroll child at the position of scrollview
parent.removeView(scroll);// remove scrollView from parent

To enable ScrollView just reverse the process

Why can't Python find shared objects that are in directories in sys.path?

Had the exact same issue. I installed curl 7.19 to /opt/curl/ to make sure that I would not affect current curl on our production servers. Once I linked to /usr/lib:

sudo ln -s /opt/curl/lib/ /usr/lib/

I still got the same error! Durf.

But running ldconfig make the linkage for me and that worked. No need to set the LD_RUN_PATH or LD_LIBRARY_PATH at all. Just needed to run ldconfig.

How to list all Git tags?

To list tags I prefer:

git tag -n

The -n flag displays the first line of the annotation message along with the tag, or the first commit message line if the tag is not annotated.

You can also do git tag -n5 to show the first 5 lines of the annotation.

How can I use LTRIM/RTRIM to search and replace leading/trailing spaces?

The LTrim function to remove leading spaces and the RTrim function to remove trailing spaces from a string variable. It uses the Trim function to remove both types of spaces and means before and after spaces of string.


How to start/stop/restart a thread in Java?

Sometimes if a Thread was started and it loaded a downside dynamic class which is processing with lots of Thread/currentThread sleep while ignoring interrupted Exception catch(es), one interrupt might not be enough to completely exit execution.

In that case, we can supply these loop-based interrupts:

    log.trace("Still processing Internally; Sending Interrupt;");
    try {
    } catch (InterruptedException e) {

How can I stop python.exe from closing immediately after I get an output?

Python files are executables, which means that you can run them directly from command prompt(assuming you have windows). You should be able to just enter in the directory, and then run the program. Also, (assuming you have python 3), you can write:

input("Press enter to close program")

and you can just press enter when you've read your results.

Case-insensitive search


let string="Stackoverflow is the BEST";
let searchstring="best";

let found = string.toLowerCase()

includes() returns true if searchString appears at one or more positions or false otherwise.

Reload content in modal (twitter bootstrap)

To unload the data when the modal is closed you can use this with Bootstrap 2.x:

$('#myModal').on('hidden', function() {

And in Bootstrap 3 (

$(document.body).on('', function () {

//Edit SL: more universal
$(document).on('', function (e) {

Should I use Java's String.format() if performance is important?

I just modified hhafez's test to include StringBuilder. StringBuilder is 33 times faster than String.format using jdk 1.6.0_10 client on XP. Using the -server switch lowers the factor to 20.

public class StringTest {

   public static void main( String[] args ) {

   private static void test() {
      int i = 0;
      long prev_time = System.currentTimeMillis();
      long time;

      for ( i = 0; i < 1000000; i++ ) {
         String s = "Blah" + i + "Blah";
      time = System.currentTimeMillis() - prev_time;

      System.out.println("Time after for loop " + time);

      prev_time = System.currentTimeMillis();
      for ( i = 0; i < 1000000; i++ ) {
         String s = String.format("Blah %d Blah", i);
      time = System.currentTimeMillis() - prev_time;
      System.out.println("Time after for loop " + time);

      prev_time = System.currentTimeMillis();
      for ( i = 0; i < 1000000; i++ ) {
         new StringBuilder("Blah").append(i).append("Blah");
      time = System.currentTimeMillis() - prev_time;
      System.out.println("Time after for loop " + time);

While this might sound drastic, I consider it to be relevant only in rare cases, because the absolute numbers are pretty low: 4 s for 1 million simple String.format calls is sort of ok - as long as I use them for logging or the like.

Update: As pointed out by sjbotha in the comments, the StringBuilder test is invalid, since it is missing a final .toString().

The correct speed-up factor from String.format(.) to StringBuilder is 23 on my machine (16 with the -server switch).

Name [jdbc/mydb] is not bound in this Context

You need a ResourceLink in your META-INF/context.xml file to make the global resource available to the web application.

 <ResourceLink name="jdbc/mydb"
              type="javax.sql.DataSource" />

PHP get domain name

To answer your question, these should work as long as:

  • Your HTTP server passes these values along to PHP (I don't know any that don't)
  • You're not accessing the script via command line (CLI)

But, if I remember correctly, these values can be faked to an extent, so it's best not to rely on them.

My personal preference is to set the domain name as an environment variable in the apache2 virtual host:

# Virtual host

And read it in PHP:

// PHP
echo getenv(DOMAIN_NAME);

This, however, isn't applicable in all circumstances.

New warnings in iOS 9: "all bitcode will be dropped"

If you are using CocoaPods and you want to disable Bitcode for all libraries, use the following command in the Podfile

post_install do |installer|
    installer.pods_project.targets.each do |target|
        target.build_configurations.each do |config|
            config.build_settings['ENABLE_BITCODE'] = 'NO'

Kill detached screen session

To kill all detached screen sessions, include this function in your .bash_profile:

killd () {
for session in $(screen -ls | grep -o '[0-9]\{5\}')
screen -S "${session}" -X quit;

to run it, call killd

How to run Gradle from the command line on Mac bash

Also, if you don't have the gradlew file in your current directory:

You can install gradle with homebrew with the following command:

$ brew install gradle

As mentioned in this answer. Then, you are not going to need to include it in your path (homebrew will take care of that) and you can just run (from any directory):

$ gradle test 

Overloading and overriding


Overloading is when you have multiple methods in the same scope, with the same name but different signatures.

public class test
    public void getStuff(int id)
    public void getStuff(string name)


Overriding is a principle that allows you to change the functionality of a method in a child class.

public class test
        public virtual void getStuff(int id)
            //Get stuff default location

public class test2 : test
        public override void getStuff(int id)
            //or - Get stuff new location

Does Django scale?

The largest django site I know of is the Washington Post, which would certainly indicate that it can scale well.

Good design decisions probably have a bigger performance impact than anything else. Twitter is often cited as a site which embodies the performance issues with another dynamic interpreted language based web framework, Ruby on Rails - yet Twitter engineers have stated that the framework isn't as much an issue as some of the database design choices they made early on.

Django works very nicely with memcached and provides some classes for managing the cache, which is where you would resolve the majority of your performance issues. What you deliver on the wire is almost more important than your backend in reality - using a tool like yslow is critical for a high performance web application. You can always throw more hardware at your backend, but you can't change your users bandwidth.

How to set a header for a HTTP GET request, and trigger file download?

I'm adding another option. The answers above were very useful for me, but I wanted to use jQuery instead of ic-ajax (it seems to have a dependency with Ember when I tried to install through bower). Keep in mind that this solution only works on modern browsers.

In order to implement this on jQuery I used jQuery BinaryTransport. This is a nice plugin to read AJAX responses in binary format.

Then you can do this to download the file and send the headers:

    url: url,
    type: 'GET',
    dataType: 'binary',
    headers: headers,
    processData: false,
    success: function(blob) {
        var windowUrl = window.URL || window.webkitURL;
        var url = windowUrl.createObjectURL(blob);
        anchor.prop('href', url);
        anchor.prop('download', fileName);

The vars in the above script mean:

  • url: the URL of the file
  • headers: a Javascript object with the headers to send
  • fileName: the filename the user will see when downloading the file
  • anchor: it is a DOM element that is needed to simulate the download that must be wrapped with jQuery in this case. For example $('').

How do I add one month to current date in Java?

Use calander and try this code.

Calendar calendar = Calendar.getInstance();         
calendar.add(Calendar.MONTH, 1);
calendar.set(Calendar.DATE, calendar.getActualMinimum(Calendar.DAY_OF_MONTH));
Date nextMonthFirstDay = calendar.getTime();
calendar.set(Calendar.DATE, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
Date nextMonthLastDay = calendar.getTime();

How do I get user IP address in django?

You can use django-ipware which supports Python 2 & 3 and handles IPv4 & IPv6.


pip install django-ipware

Simple Usage:

# In a view or a middleware where the `request` object is available

from ipware import get_client_ip
ip, is_routable = get_client_ip(request)
if ip is None:
    # Unable to get the client's IP address
    # We got the client's IP address
    if is_routable:
        # The client's IP address is publicly routable on the Internet
        # The client's IP address is private

# Order of precedence is (Public, Private, Loopback, None)

Advanced Usage:

  • Custom Header - Custom request header for ipware to look at:

    i, r = get_client_ip(request, request_header_order=['X_FORWARDED_FOR'])
    i, r = get_client_ip(request, request_header_order=['X_FORWARDED_FOR', 'REMOTE_ADDR'])
  • Proxy Count - Django server is behind a fixed number of proxies:

    i, r = get_client_ip(request, proxy_count=1)
  • Trusted Proxies - Django server is behind one or more known & trusted proxies:

    i, r = get_client_ip(request, proxy_trusted_ips=(''))
    # For multiple proxies, simply add them to the list
    i, r = get_client_ip(request, proxy_trusted_ips=('', ''))
    # For proxies with fixed sub-domain and dynamic IP addresses, use partial pattern
    i, r = get_client_ip(request, proxy_trusted_ips=('177.2.', '177.3.'))

Note: read this notice.

How to hide "Showing 1 of N Entries" with the dataTables.js library

Now, this seems to work:

  "info": false

it hides that div, altogether

How to set UITextField height?

An update for iOS 6 : using auto-layout, even though you still can't set the UITextField's height from the Size Inspector in the Interface Builder (as of Xcode 4.5 DP4 at least), it is now possible to set a Height constraint on it, which you can edit from the Interface Builder.

Also, if you're setting the frame's height by code, auto-layout may reset it depending on the other constraints your view may have.

How to implement class constants?

Angular 2 Provides a very nice feature called as Opaque Constants. Create a class & Define all the constants there using opaque constants.

import { OpaqueToken } from "@angular/core";

export let APP_CONFIG = new OpaqueToken("my.config");

export interface MyAppConfig {
    apiEndpoint: string;

export const AppConfig: MyAppConfig = {    
    apiEndpoint: "http://localhost:8080/api/"    

Inject it in providers in app.module.ts

You will be able to use it across every components.

EDIT for Angular 4 :

For Angular 4 the new concept is Injection Token & Opaque token is Deprecated in Angular 4.

Injection Token Adds functionalities on top of Opaque Tokens, it allows to attach type info on the token via TypeScript generics, plus Injection tokens, removes the need of adding @Inject

Example Code

Angular 2 Using Opaque Tokens

const API_URL = new OpaqueToken('apiUrl'); //no Type Check

providers: [
    provide: DataService,
    useFactory: (http, apiUrl) => {
      // create data service
    deps: [
      new Inject(API_URL) //notice the new Inject

Angular 4 Using Injection Tokens

const API_URL = new InjectionToken<string>('apiUrl'); // generic defines return value of injector

providers: [
    provide: DataService,
    useFactory: (http, apiUrl) => {
      // create data service
    deps: [
      API_URL // no `new Inject()` needed!

Injection tokens are designed logically on top of Opaque tokens & Opaque tokens are deprecated in Angular 4.

How to replace blank (null ) values with 0 for all records?

without 'where's and 'if's ...

Update Table Set MyField = Nz(MyField,0)

How to implement a simple scenario the OO way

The approach I would take is: when reading the chapters from the database, instead of a collection of chapters, use a collection of books. This will have your chapters organised into books and you'll be able to use information from both classes to present the information to the user (you can even present it in a hierarchical way easily when using this approach).

file_put_contents - failed to open stream: Permission denied

This can be resolved in resolved with the following steps :

1. $ php artisan cache:clear

2. $ sudo chmod -R 777 storage

3. $ composer dump-autoload

Hope it helps

What are my options for storing data when using React Native? (iOS and Android)

We dont need redux-persist we can simply use redux for persistance.

react-redux + AsyncStorage = redux-persist

so inside createsotre file simply add these lines

store.subscribe(async()=> await AsyncStorage.setItem("store", JSON.stringify(store.getState())))

this will update the AsyncStorage whenever there are some changes in the redux store.

Then load the json converted store. when ever the app loads. and set the store again.

Because redux-persist creates issues when using wix react-native-navigation. If that's the case then I prefer to use simple redux with above subscriber function

How to search for a string in an arraylist

List <String> list = new ArrayList();  

           List <String> listClone = new ArrayList<String>(); 
           Pattern pattern = Pattern.compile("bea",Pattern.CASE_INSENSITIVE); //incase u r not concerned about upper/lower case
           for (String string : list) {
               if(pattern.matcher(string).find()) {

What is the difference between conversion specifiers %i and %d in formatted IO functions (*printf / *scanf)

These are identical for printf but different for scanf. For printf, both %d and %i designate a signed decimal integer. For scanf, %d and %i also means a signed integer but %i inteprets the input as a hexadecimal number if preceded by 0x and octal if preceded by 0 and otherwise interprets the input as decimal.

How do I convert ticks to minutes?

You can do this way :

TimeSpan duration = new TimeSpan(tickCount)
double minutes = duration.TotalMinutes;

source command not found in sh shell

I found in a gnu Makefile on Ubuntu, (where /bin/sh -> bash)

I needed to use the . command, as well as specify the target script with a ./ prefix (see example below)

source did not work in this instance, not sure why since it should be calling /bin/bash..

My SHELL environment variable is also set to /bin/bash

    $(shell . ./my_script)

Note this sample does not include the tab character; had to format for stack exchange.

Stopping Docker containers by image name - Ubuntu

use: docker container stop $(docker container ls -q --filter ancestor=mongo)

    (base) :~ user$ docker ps
    CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                      NAMES
    d394144acf3a        mongo               "docker-entrypoint.s…"   15 seconds ago      Up 14 seconds>27017/tcp   magical_nobel
    (base) :~ user$ docker container stop $(docker container ls -q --filter ancestor=mongo)
    (base) :~ user$ docker ps
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
    (base) :~ user$

Element implicitly has an 'any' type because expression of type 'string' can't be used to index

I have made a simulation of the problem. looks like the issue is how we should Access Object Properties Dynamically Using Bracket Notation in Typescript

interface IUserProps {
  name: string;
  age: number;

export default class User {
  constructor(private data: IUserProps) {}

  get(propName: string): string | number {
    return[propName as keyof IUserProps];

I found a blog that might be helpful to understand this better.

here is a link

Setting Windows PowerShell environment variables

As Jonathan Leaders mentioned here, it is important to run the command/script elevated to be able to change environment variables for 'machine', but running some commands elevated doesn't have to be done with the Community Extensions, so I'd like to modify and extend JeanT's answer in a way, that changing machine variables also can be performed even if the script itself isn't run elevated:

function Set-Path ([string]$newPath, [bool]$permanent=$false, [bool]$forMachine=$false )
    $Env:Path += ";$newPath"

    $scope = if ($forMachine) { 'Machine' } else { 'User' }

    if ($permanent)
        $command = "[Environment]::SetEnvironmentVariable('PATH', $env:Path, $scope)"
        Start-Process -FilePath powershell.exe -ArgumentList "-noprofile -command $Command" -Verb runas


Moment.js with ReactJS (ES6)

I'm using moment in my react project

import moment from 'moment'

state = {
    startDate: moment()
render() {
    const selectedDate = this.state.startDate.format("Do MMMM YYYY");

Write HTML string in JSON

4 Things You Must Do When Putting HTML in JSON:

1) Escape quotation marks used around HTML attributes like so <img src=\"someimage.png\" />

2) Escape the forward slash in HTML end tags. <div>Hello World!<\/div>. This is an ancient artifact of an old HTML spec that didn't want HTML parsers to get confused when putting strings in a <SCRIPT> tag. For some reason, today’s browsers still like it.

3) This one was totally bizarre. You should include a space between the tag name and the slash on self-closing tags. I have no idea why this is, but on MOST modern browsers, if you try using javascript to append a <li> tag as a child of an unordered list that is formatted like so: <ul/>, it won't work. It gets added to the DOM after the ul tag. But, if the code looks like this: <ul /> (notice the space before the /), everything works fine. Very strange indeed.

4) Be sure to encode any quotation marks that might be included in (bad) HTML content. This is the only thing that would really break the JSON by accidentally terminating the string early. Any " characters should be encoded as &quot; if it is meant to be included as HTML content.


Gradle error: could not execute build using gradle distribution

I had this issue as well and jaywhy13 answer was good but not enough.

I had to change a setting: Settings -> Gradle -> MyProject

There you need to check the "auto import" and select "use customizable gradle wrapper". After that it should refresh gradle and you can build again. If not try a reboot of Android Studio.

How to clear textarea on click?

Your JavaScript:

function clearContents(element) {
  element.value = '';

And your HTML:

<textarea onfocus="clearContents(this);">Please describe why</textarea>

I assume you'll want to make this a little more robust, so as to not wipe user input when focusing a second time. Here are five related discussions & articles.

And here's the (much better) idea that David Dorward refers to in comments above:

<label for="explanation">Please describe why</label>
<textarea name="explanation" id="explanation"></textarea>

Google Authenticator available as a public service?

For C# user, run this simple Console App to understand how to verify the one time token code. Note that we need to install library Otp.Net from Nuget package first.

static string secretKey = "JBSWY3DPEHPK3PXP"; //add this key to your Google Authenticator app  

private static void Main(string[] args)
        var bytes = Base32Encoding.ToBytes(secretKey);

        var totp = new Totp(bytes);

        while (true)
            Console.Write("Enter your code from Google Authenticator app: ");
            string userCode = Console.ReadLine();

            //Generate one time token code
            string tokenInApp = totp.ComputeTotp();
            int remainingSeconds = totp.RemainingSeconds();

            if (userCode.Equals(tokenInApp)
                && remainingSeconds > 0)
                Console.WriteLine("Failed. Try again!");

Why "Data at the root level is invalid. Line 1, position 1." for XML Document?

I can give you two advices:

  1. It seems you are using "LoadXml" instead of "Load" method. In some cases, it helps me.
  2. You have an encoding problem. Could you check the encoding of the XML file and write it?

Declaring variable workbook / Worksheet vba

I had the same issue. I used Worksheet instead of Worksheets and it was resolved. Not sure what the difference is between them.

Create dataframe from a matrix

If you change your time column into row names, then you can use for simple cases like this.


data <- c(0.1, 0.2, 0.3, 0.3, 0.4, 0.5)
dimnames <- list(time=c(0, 0.5, 1), name=c("C_0", "C_1"))
mat <- matrix(data, ncol=2, nrow=3, dimnames=dimnames)
  time name Freq
1    0  C_0  0.1
2  0.5  C_0  0.2
3    1  C_0  0.3
4    0  C_1  0.3
5  0.5  C_1  0.4
6    1  C_1  0.5

In this case time and name are both factors. You may want to convert time back to numeric, or it may not matter.

how can the textbox width be reduced?

Is not nice to define textbox width without using CSS, be warned ;-)

<input type="text" name="d" value="4" size="4" />

How do I set the background color of Excel cells using VBA?

or alternatively you could not bother coding for it and use the 'conditional formatting' function in Excel which will set the background colour and font colour based on cell value.

There are only two variables here so set the default to yellow and then overwrite when the value is greater than or less than your threshold values.

How to copy files between two nodes using ansible

To copy remote-to-remote files you can use the synchronize module with 'delegate_to: source-server' keyword:

- hosts: serverB
   - name: Copy Remote-To-Remote (from serverA to serverB)
     synchronize: src=/copy/from_serverA dest=/copy/to_serverB
     delegate_to: serverA

This playbook can run from your machineC.