Programs & Examples On #Virtual memory

Virtual memory is a memory management technique developed for multitasking kernels.

Virtual Memory Usage from Java under Linux, too much memory used

The Sun JVM requires a lot of memory for HotSpot and it maps in the runtime libraries in shared memory.

If memory is an issue consider using another JVM suitable for embedding. IBM has j9, and there is the Open Source "jamvm" which uses GNU classpath libraries. Also Sun has the Squeak JVM running on the SunSPOTS so there are alternatives.

What are the differences between virtual memory and physical memory?

I am shamelessly copying the excerpts from man page of top

VIRT -- Virtual Image (kb) The total amount of virtual memory used by the task. It includes all code, data and shared libraries plus pages that have been swapped out and pages that have been mapped but not used.

SWAP -- Swapped size (kb) Memory that is not resident but is present in a task. This is memory that has been swapped out but could include additional non- resident memory. This column is calculated by subtracting physical memory from virtual memory

ERROR Source option 1.5 is no longer supported. Use 1.6 or later

You can specify maven source/target version by adding these properties to your pom.xml file


Class JavaLaunchHelper is implemented in both ... libinstrument.dylib. One of the two will be used. Which one is undefined

Well, after some struggling, what worked for me was completely removing the current JDK, as described here:

sudo rm -rf /Library/Java/JavaVirtualMachines/jdk1.7.0_80.jdk
sudo rm -rf /Library/PreferencePanes/JavaControlPanel.prefPane
sudo rm -rf /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
sudo rm -rf /Library/LaunchAgents/
sudo rm -rf /Library/PrivilegedHelperTools/
sudo rm -rf /Library/LaunchDaemons/
sudo rm -rf /Library/Preferences/

Then installed 1.7.0_21, which was downloaded from here.

Now java -version prompts:

java version "1.7.0_21"
Java(TM) SE Runtime Environment (build 1.7.0_21-b12)
Java HotSpot(TM) 64-Bit Server VM (build 23.21-b01, mixed mode)

Git commit in terminal opens VIM, but can't get back to terminal

This is in answer to your question...

I'd also like to know how to make it open up in Sublime Text 2 instead

For Windows:

git config --global core.editor "'C:/Program Files/Sublime Text 2/sublime_text.exe'"

Check that the path for sublime_text.exe is correct and adjust if needed.

For Mac/Linux:

git config --global core.editor "subl -n -w"

If you get an error message such as:

error: There was a problem with the editor 'subl -n -w'.

Create the alias for subl

sudo ln -s /Applications/Sublime\ /usr/local/bin/subl

Again check that the path matches for your machine.

For Sublime Text simply save cmd S and close the window cmd W to return to git.

How to make inline plots in Jupyter Notebook larger?

The question is about matplotlib, but for the sake of any R users that end up here given the language-agnostic title:

If you're using an R kernel, just use:

options(repr.plot.width=4, repr.plot.height=3)

Android image caching

Late answer but I think this library will help a lot with caching images :

Simply annotate the ImageView with @LoadCache(, "URL_to_downlaod_image_from) and it will take care of downloading the image and loading it into the image view. You can also specify a placeholder image and loading animation.

Detailed documentation of the annotation is present here :-

Parsing a JSON string in Ruby

Just to extend the answers a bit with what to do with the parsed object:

# JSON Parsing example
require "rubygems" # don't need this if you're Ruby v1.9.3 or higher
require "json"

string = '{"desc":{"someKey":"someValue","anotherKey":"value"},"main_item":{"stats":{"a":8,"b":12,"c":10}}}'
parsed = JSON.parse(string) # returns a hash

p parsed["desc"]["someKey"]
p parsed["main_item"]["stats"]["a"]

# Read JSON from a file, iterate over objects
file = open("shops.json")
json =

parsed = JSON.parse(json)

parsed["shop"].each do |shop|
  p shop["id"]

Get the data received in a Flask request

To get request.form as a normal dictionary , use request.form.to_dict(flat=False).

To return JSON data for an API, pass it to jsonify.

This example returns form data as JSON data.

@app.route('/form_to_json', methods=['POST'])
def form_to_json():
    data = request.form.to_dict(flat=False)
    return jsonify(data)

Here's an example of POST form data with curl, returning as JSON:

$ curl -d "name=ivanleoncz&role=Software Developer"
  "name": "ivanleoncz", 
  "role": "Software Developer"

How to send a compressed archive that contains executables so that Google's attachment filter won't reject it

To bypass google's check, which is what you really want, simply remove the extensions from the file when you send it, and add them back after you download it. For example:

  • tar czvf file.tar.gz directory
  • mv file.tar.gz filetargz
  • [send filetargz via gmail]
  • [download filetargz]
  • [rename filetargz to file.tar.gz and open]

React ignores 'for' attribute of the label element

The for attribute is called htmlFor for consistency with the DOM property API. If you're using the development build of React, you should have seen a warning in your console about this.

Python Save to file

file = open('', 'w')

Here is a more pythonic version, which automatically closes the file, even if there was an exception in the wrapped block:

with open('', 'w') as file:

Elasticsearch difference between MUST and SHOULD bool query

Since this is a popular question, I would like to add that in Elasticsearch version 2 things changed a bit.

Instead of filtered query, one should use bool query in the top level.

If you don't care about the score of must parts, then put those parts into filter key. No scoring means faster search. Also, Elasticsearch will automatically figure out, whether to cache them, etc. must_not is equally valid for caching.


Also, mind that "gte": "now" cannot be cached, because of millisecond granularity. Use two ranges in a must clause: one with now/1h and another with now so that the first can be cached for a while and the second for precise filtering accelerated on a smaller result set.

Oracle: SQL select date with timestamp

Answer provided by Nicholas Krasnov


How to remove specific elements in a numpy array

Use numpy.delete() - returns a new array with sub-arrays along an axis deleted

numpy.delete(a, index)

For your specific question:

import numpy as np

a = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9])
index = [2, 3, 6]

new_a = np.delete(a, index)

print(new_a) #Prints `[1, 2, 5, 6, 8, 9]`

Note that numpy.delete() returns a new array since array scalars are immutable, similar to strings in Python, so each time a change is made to it, a new object is created. I.e., to quote the delete() docs:

"A copy of arr with the elements specified by obj removed. Note that delete does not occur in-place..."

If the code I post has output, it is the result of running the code.

IOException: read failed, socket might closed - Bluetooth on Android 4.3

In case somebody is having issues with Kotlin, I had to follow the accepted answer with some variations:

fun print(view: View, text: String) {
    var adapter = BluetoothAdapter.getDefaultAdapter();
    var pairedDevices = adapter.getBondedDevices()
    var uuid = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")
    if (pairedDevices.size > 0) {
        for (device in pairedDevices) {
            var s =
            if (device.getName().equals(printerName, ignoreCase = true)) {
                Thread {
                    var socket = device.createInsecureRfcommSocketToServiceRecord(uuid)
                    var clazz = socket.remoteDevice.javaClass
                    var paramTypes = arrayOf<Class<*>>(Integer.TYPE)
                    var m = clazz.getMethod("createRfcommSocket", *paramTypes)
                    var fallbackSocket = m.invoke(socket.remoteDevice, Integer.valueOf(1)) as BluetoothSocket
                    try {
                        var stream = fallbackSocket.outputStream
                    } catch (e: Exception) {
                        Snackbar.make(view, "An error occurred", Snackbar.LENGTH_SHORT).show()

Hope it helps

Does dispatch_async(dispatch_get_main_queue(), ^{...}); wait until done?

You have to put your main queue dispatching in the block that runs the computation. For example (here I create a dispatch queue and don't use a global one):

dispatch_queue_t queue = dispatch_queue_create("com.example.MyQueue", NULL);
dispatch_async(queue, ^{
  // Do some computation here.

  // Update UI after computation.
  dispatch_async(dispatch_get_main_queue(), ^{
    // Update the UI on the main thread.

Of course, if you create a queue don't forget to dispatch_release if you're targeting an iOS version before 6.0.

Quickest way to convert a base 10 number to any base in .NET?

Convert.ToString can be used to convert a number to its equivalent string representation in a specified base.


string binary = Convert.ToString(5, 2); // convert 5 to its binary representation
Console.WriteLine(binary);              // prints 101

However, as pointed out by the comments, Convert.ToString only supports the following limited - but typically sufficient - set of bases: 2, 8, 10, or 16.

Update (to meet the requirement to convert to any base):

I'm not aware of any method in the BCL which is capable to convert numbers to any base so you would have to write your own small utility function. A simple sample would look like that (note that this surely can be made faster by replacing the string concatenation):

class Program
    static void Main(string[] args)
        // convert to binary
        string binary = IntToString(42, new char[] { '0', '1' });

        // convert to hexadecimal
        string hex = IntToString(42, 
            new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                         'A', 'B', 'C', 'D', 'E', 'F'});

        // convert to hexavigesimal (base 26, A-Z)
        string hexavigesimal = IntToString(42, 
            Enumerable.Range('A', 26).Select(x => (char)x).ToArray());

        // convert to sexagesimal
        string xx = IntToString(42, 
            new char[] { '0','1','2','3','4','5','6','7','8','9',

    public static string IntToString(int value, char[] baseChars)
        string result = string.Empty;
        int targetBase = baseChars.Length;

            result = baseChars[value % targetBase] + result;
            value = value / targetBase;
        while (value > 0);

        return result;

    /// <summary>
    /// An optimized method using an array as buffer instead of 
    /// string concatenation. This is faster for return values having 
    /// a length > 1.
    /// </summary>
    public static string IntToStringFast(int value, char[] baseChars)
        // 32 is the worst cast buffer size for base 2 and int.MaxValue
        int i = 32;
        char[] buffer = new char[i];
        int targetBase= baseChars.Length;

            buffer[--i] = baseChars[value % targetBase];
            value = value / targetBase;
        while (value > 0);

        char[] result = new char[32 - i];
        Array.Copy(buffer, i, result, 0, 32 - i);

        return new string(result);

Update 2 (Performance Improvement)

Using an array buffer instead of string concatenation to build the result string gives a performance improvement especially on large number (see method IntToStringFast). In the best case (i.e. the longest possible input) this method is roughly three times faster. However, for 1-digit numbers (i.e. 1-digit in the target base), IntToString will be faster.

Print multiple arguments in Python

There are many ways to do this. To fix your current code using %-formatting, you need to pass in a tuple:

  1. Pass it as a tuple:

    print("Total score for %s is %s" % (name, score))

A tuple with a single element looks like ('this',).

Here are some other common ways of doing it:

  1. Pass it as a dictionary:

    print("Total score for %(n)s is %(s)s" % {'n': name, 's': score})

There's also new-style string formatting, which might be a little easier to read:

  1. Use new-style string formatting:

    print("Total score for {} is {}".format(name, score))
  2. Use new-style string formatting with numbers (useful for reordering or printing the same one multiple times):

    print("Total score for {0} is {1}".format(name, score))
  3. Use new-style string formatting with explicit names:

    print("Total score for {n} is {s}".format(n=name, s=score))
  4. Concatenate strings:

    print("Total score for " + str(name) + " is " + str(score))

The clearest two, in my opinion:

  1. Just pass the values as parameters:

    print("Total score for", name, "is", score)

    If you don't want spaces to be inserted automatically by print in the above example, change the sep parameter:

    print("Total score for ", name, " is ", score, sep='')

    If you're using Python 2, won't be able to use the last two because print isn't a function in Python 2. You can, however, import this behavior from __future__:

    from __future__ import print_function
  2. Use the new f-string formatting in Python 3.6:

    print(f'Total score for {name} is {score}')

NoClassDefFoundError while trying to run my jar with java.exe -jar...what's wrong?

You can omit the -jar option and start the jar file like this:

java -cp MyJar.jar;C:\externalJars\* mainpackage.MyMainClass

Maven- No plugin found for prefix 'spring-boot' in the current project and in the plugin groups

If you are using Spring Boot for application, forgetting to add


can cause this issue, as well as missing these lines


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

For languages not specifying a memory model, you are writing code for the language and the memory model specified by the processor architecture. The processor may choose to re-order memory accesses for performance. So, if your program has data races (a data race is when it's possible for multiple cores / hyper-threads to access the same memory concurrently) then your program is not cross platform because of its dependence on the processor memory model. You may refer to the Intel or AMD software manuals to find out how the processors may re-order memory accesses.

Very importantly, locks (and concurrency semantics with locking) are typically implemented in a cross platform way... So if you are using standard locks in a multithreaded program with no data races then you don't have to worry about cross platform memory models.

Interestingly, Microsoft compilers for C++ have acquire / release semantics for volatile which is a C++ extension to deal with the lack of a memory model in C++ However, given that Windows runs on x86 / x64 only, that's not saying much (Intel and AMD memory models make it easy and efficient to implement acquire / release semantics in a language).

XAMPP installation on Win 8.1 with UAC Warning

You can solve this problem by installing xampp in different Drive .Instead of C Drive .

Importing the private-key/public-certificate pair in the Java KeyStore

A keystore needs a keystore file. The KeyStore class needs a FileInputStream. But if you supply null (instead of FileInputStream instance) an empty keystore will be loaded. Once you create a keystore, you can verify its integrity using keytool.

Following code creates an empty keystore with empty password

  KeyStore ks2 = KeyStore.getInstance("jks");
  FileOutputStream out = new FileOutputStream("C:\\mykeytore.keystore");, "".toCharArray());

Once you have the keystore, importing certificate is very easy. Checkout this link for the sample code.

ACCESS_FINE_LOCATION AndroidManifest Permissions Not Being Granted

just remove s from the permission you are using sss you have to use ss

Android basics: running code in the UI thread

use Handler

new Handler(Looper.getMainLooper()).post(new Runnable() {
    public void run() {
        // Code here will run in UI thread

Error in setting JAVA_HOME

You are pointing your JAVA_HOME to the JRE which is the Java Runtime Environment. The runtime environment doesn't have a java compiler in its bin folder. You should download the JDK which is the Java Development Kit. Once you've installed that, you can see in your bin folder that there's a file called javac.exe. That's your compiler.

Vba macro to copy row from table if value in table meets condition

Selects are slow and unnescsaary. The following code will be far faster:

Sub CopyRowsAcross() 
Dim i As Integer 
Dim ws1 As Worksheet: Set ws1 = ThisWorkbook.Sheets("Sheet1") 
Dim ws2 As Worksheet: Set ws2 = ThisWorkbook.Sheets("Sheet2") 

For i = 2 To ws1.Range("B65536").End(xlUp).Row 
    If ws1.Cells(i, 2) = "Your Critera" Then ws1.Rows(i).Copy ws2.Rows(ws2.Cells(ws2.Rows.Count, 2).End(xlUp).Row + 1) 
Next i 
End Sub 

Represent space and tab in XML tag

Illegal XML Tag Name Characters can be encoded using Unicode UCS-2. This works very nicely. I am using it to create XML that gets turned into json (JPath is weak compared to XPath). Notice the handling of spaces, (, ) characters. Unicode UCS-2 Code Chart:

        tag.Name = tag.Name.Replace(" ", "_x005F_x0020_");
        tag.Name = tag.Name.Replace("(", "_x005F_x0028_");
        tag.Name = tag.Name.Replace(")", "_x005F_x0029_");


  <Operator_x005F_x0020_or_x005F_x0020_Directly_x005F_x0020_Responsible_x005F_x0020_Individual_x005F_x0020__x005F_x0028_DRI_x005F_x0029_>[email protected]</Operator_x005F_x0020_or_x005F_x0020_Directly_x005F_x0020_Responsible_x005F_x0020_Individual_x005F_x0020__x005F_x0028_DRI_x005F_x0029_>

transformed to json via

    "Internal Chargeback ID": "{CHARGEBACKCODE}",
    "Bill To": "{CHARGEBACKCODE}",
    "Operator or Directly Responsible Individual (DRI)": "[email protected]",

Angular 4: How to include Bootstrap?

Run the following command in your project i.e npm install [email protected] --save

After installing the above dependency run the following npm command which will install the bootstrap module npm install --save @ng-bootstrap/ng-bootstrap

Check this out for the reference -

Add the following import into app.module import {NgbModule} from '@ng-bootstrap/ng-bootstrap'; and add NgbModule to the imports

In your stye.css @import "../node_modules/bootstrap/dist/css/bootstrap.min.css";

Negate if condition in bash script

Since you're comparing numbers, you can use an arithmetic expression, which allows for simpler handling of parameters and comparison:

wget -q --tries=10 --timeout=20 --spider
if (( $? != 0 )); then
    echo "Sorry you are Offline"
    exit 1

Notice how instead of -ne, you can just use !=. In an arithmetic context, we don't even have to prepend $ to parameters, i.e.,

(( var_a < var_b )) && echo "a is smaller"

works perfectly fine. This doesn't appply to the $? special parameter, though.

Further, since (( ... )) evaluates non-zero values to true, i.e., has a return status of 0 for non-zero values and a return status of 1 otherwise, we could shorten to

if (( $? )); then

but this might confuse more people than the keystrokes saved are worth.

The (( ... )) construct is available in Bash, but not required by the POSIX shell specification (mentioned as possible extension, though).

This all being said, it's better to avoid $? altogether in my opinion, as in Cole's answer and Steven's answer.

VBA paste range

I would try

Set Ticker = Range(Cells(2, 1), Cells(65, 1))


How to set only time part of a DateTime variable in C#

It isn't possible as DateTime is immutable. The same discussion is available here: How to change time in datetime?

How to align checkboxes and their labels consistently cross-browsers

Warning! This answer is too old and doesn't work on modern browsers.

I'm not the poster of this answer, but at the time of writing this, this is the most voted answer by far in both positive and negative votes (+1035 -17), and it's still marked as accepted answer (probably because the original poster of the question is the one who wrote this answer).

As already noted many times in the comments, this answer does not work on most browsers anymore (and seems to be failing to do that since 2013).

After over an hour of tweaking, testing, and trying different styles of markup, I think I may have a decent solution. The requirements for this particular project were:

  1. Inputs must be on their own line.
  2. Checkbox inputs need to align vertically with the label text similarly (if not identically) across all browsers.
  3. If the label text wraps, it needs to be indented (so no wrapping down underneath the checkbox).

Before I get into any explanation, I'll just give you the code:

label {
  display: block;
  padding-left: 15px;
  text-indent: -15px;
input {
  width: 13px;
  height: 13px;
  padding: 0;
  vertical-align: bottom;
  position: relative;
  top: -1px;
  *overflow: hidden;
    <label><input type="checkbox" /> Label text</label>

Here is the working example in JSFiddle.

This code assumes that you're using a reset like Eric Meyer's that doesn't override form input margins and padding (hence putting margin and padding resets in the input CSS). Obviously in a live environment you'll probably be nesting/overriding stuff to support other input elements, but I wanted to keep things simple.

Things to note:

  • The *overflow declaration is an inline IE hack (the star-property hack). Both IE 6 and 7 will notice it, but Safari and Firefox will properly ignore it. I think it might be valid CSS, but you're still better off with conditional comments; just used it for simplicity.
  • As best I can tell, the only vertical-align statement that was consistent across browsers was vertical-align: bottom. Setting this and then relatively positioning upwards behaved almost identically in Safari, Firefox and IE with only a pixel or two of discrepancy.
  • The major problem in working with alignment is that IE sticks a bunch of mysterious space around input elements. It isn't padding or margin, and it's damned persistent. Setting a width and height on the checkbox and then overflow: hidden for some reason cuts off the extra space and allows IE's positioning to act very similarly to Safari and Firefox.
  • Depending on your text sizing, you'll no doubt need to adjust the relative positioning, width, height, and so forth to get things looking right.

Hope this helps someone else! I haven't tried this specific technique on any projects other than the one I was working on this morning, so definitely pipe up if you find something that works more consistently.

Warning! This answer is too old and doesn't work on modern browsers.

How to compare files from two different branches?

Use commit hashes as this:

git diff <hash1> <hash2> <filename>

where hash1 can be any commit from any branch, the same for hash2.

Ascii/Hex convert in bash

I use:

> echo Aa | tr -d '\n' | xxd -p

> echo 414161 | tr -d '\n' | xxd -r -p

The tr -d '\n' will trim any possible newlines in your input

C++ Convert string (or char*) to wstring (or wchar_t*)

using Boost.Locale:

ws = boost::locale::conv::utf_to_utf<wchar_t>(s);

How to convert the following json string to java object?

Gson gson = new Gson();
JsonParser parser = new JsonParser();
JsonObject object = (JsonObject) parser.parse(response);// response will be the json String
YourPojo emp = gson.fromJson(object, YourPojo.class); 

Getting a Request.Headers value

Firstly you don't do this in your view. You do it in the controller and return a view model to the view so that the view doesn't need to care about custom HTTP headers but just displaying data on the view model:

public ActionResult Index()
    var xyzComponent = Request.Headers["xyzComponent"];
    var model = new MyModel 
        IsCustomHeaderSet = (xyzComponent != null)
    return View(model);

Hide particular div onload and then show div after click

Make sure to watch your selectors. You appear to have forgotten the # for div2. Additionally, you can toggle the visibility of many elements at once with .toggle():

// Short-form of `document.ready`
    $("#preview").on("click", function(){
        $("#div1, #div2").toggle();


Calling UserForm_Initialize() in a Module

From a module:


Just make sure that in your userform, you update the sub like so:

Public Sub UserForm_Initialize() so it can be called from outside the form.

Alternately, if the Userform hasn't been loaded:

UserFormName.Show will end up calling UserForm_Initialize because it loads the form.

Unable to Build using MAVEN with ERROR - Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile

For my situation, I switched the value of "fork" to false, such as <fork>false</fork>. I do not understand why, hope someone could explain to me. Thanks in advance.

Upload files from Java client to a HTTP server

You'd normally use to fire HTTP requests. You'd also normally use multipart/form-data encoding for mixed POST content (binary and character data). Click the link, it contains information and an example how to compose a multipart/form-data request body. The specification is in more detail described in RFC2388.

Here's a kickoff example:

String url = "";
String charset = "UTF-8";
String param = "value";
File textFile = new File("/path/to/file.txt");
File binaryFile = new File("/path/to/file.bin");
String boundary = Long.toHexString(System.currentTimeMillis()); // Just generate some unique random value.
String CRLF = "\r\n"; // Line separator required by multipart/form-data.

URLConnection connection = new URL(url).openConnection();
connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);

try (
    OutputStream output = connection.getOutputStream();
    PrintWriter writer = new PrintWriter(new OutputStreamWriter(output, charset), true);
) {
    // Send normal param.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"param\"").append(CRLF);
    writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF);

    // Send text file.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"textFile\"; filename=\"" + textFile.getName() + "\"").append(CRLF);
    writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF); // Text file itself must be saved in this charset!
    Files.copy(textFile.toPath(), output);
    output.flush(); // Important before continuing with writer!
    writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.

    // Send binary file.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"binaryFile\"; filename=\"" + binaryFile.getName() + "\"").append(CRLF);
    writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(binaryFile.getName())).append(CRLF);
    writer.append("Content-Transfer-Encoding: binary").append(CRLF);
    Files.copy(binaryFile.toPath(), output);
    output.flush(); // Important before continuing with writer!
    writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.

    // End of multipart/form-data.
    writer.append("--" + boundary + "--").append(CRLF).flush();

// Request is lazily fired whenever you need to obtain information about response.
int responseCode = ((HttpURLConnection) connection).getResponseCode();
System.out.println(responseCode); // Should be 200

This code is less verbose when you use a 3rd party library like Apache Commons HttpComponents Client.

The Apache Commons FileUpload as some incorrectly suggest here is only of interest in the server side. You can't use and don't need it at the client side.

See also

Return from lambda forEach() in java

This what helped me:

List<RepositoryFile> fileList = response.getRepositoryFileList();
RepositoryFile file1 = -> f.getName().contains("my-file.txt")).findFirst().orElse(null);

Taken from Java 8 Finding Specific Element in List with Lambda

What is the difference between DSA and RSA?

With reference to man ssh-keygen, the length of a DSA key is restricted to exactly 1024 bit to remain compliant with NIST's FIPS 186-2. Nonetheless, longer DSA keys are theoretically possible; FIPS 186-3 explicitly allows them. Furthermore, security is no longer guaranteed with 1024 bit long RSA or DSA keys.

In conclusion, a 2048 bit RSA key is currently the best choice.


Establishing a secure SSH connection entails more than selecting safe encryption key pair technology. In view of Edward Snowden's NSA revelations, one has to be even more vigilant than what previously was deemed sufficient.

To name just one example, using a safe key exchange algorithm is equally important. Here is a nice overview of current best SSH hardening practices.

How to convert List<string> to List<int>?

I know it's old post, but I thought this is a good addition: You can use List<T>.ConvertAll<TOutput>

List<int> integers = strings.ConvertAll(s => Int32.Parse(s));

Correct way to pause a Python program

Very simple:

raw_input("Press Enter to continue ...")

How to center a label text in WPF?

You have to use HorizontalContentAlignment="Center" and! Width="Auto".

How to create a HTML Table from a PHP array?

echo "<table><tr><th>Title</th><th>Price</th><th>Number</th></tr>";
foreach($shop as $v){
    echo "<tr>";
    foreach($v as $vv){
        echo "<td>{$vv}</td>";
    echo "<tr>";
echo "</table>";

What does the colon (:) operator do?

It is used in the new short hand for/loop

final List<String> list = new ArrayList<String>();
for (final String s : list)

and the ternary operator

list.isEmpty() ? true : false;

How to check if image exists with given url?

jQuery 3.0 removed .error. Correct syntax is now

$(this).on('error', function(){
    console.log('Image does not exist: ' +; 

How do you install an APK file in the Android emulator?

you write the command on terminal/cmd adb install FileName.apk.

Script to get the HTTP status code of a list of urls?

Curl has a specific option, --write-out, for this:

$ curl -o /dev/null --silent --head --write-out '%{http_code}\n' <url>
  • -o /dev/null throws away the usual output
  • --silent throws away the progress meter
  • --head makes a HEAD HTTP request, instead of GET
  • --write-out '%{http_code}\n' prints the required status code

To wrap this up in a complete Bash script:

while read LINE; do
  curl -o /dev/null --silent --head --write-out "%{http_code} $LINE\n" "$LINE"
done < url-list.txt

(Eagle-eyed readers will notice that this uses one curl process per URL, which imposes fork and TCP connection penalties. It would be faster if multiple URLs were combined in a single curl, but there isn't space to write out the monsterous repetition of options that curl requires to do this.)

how to find all indexes and their columns for tables, views and synonyms in oracle

SELECT * FROM user_cons_columns WHERE table_name = 'table_name';

How to select top n rows from a datatable/dataview in ASP.NET

If you want the number of rows to be flexible, you can add row_number in the SQL. For SQL server:


Then filter the datatable on row_number:

Dataview dv= new Dataview(dt, "ROW_NUMBER<=100", "", CurrentRows)

How do I lowercase a string in C?

If you need Unicode support in the lower case function see this question: Light C Unicode Library

Can't find @Nullable inside javax.annotation.*

You need to include a jar that this class exists in. You can find it here

If using Maven, you can add the following dependency declaration:


and for Gradle:

dependencies {
  testImplementation ''

How do I test which class an object is in Objective-C?

You also can use

NSString *className = [[myObject class] description]; 

on any NSObject

Numpy: find index of the elements within range

a = np.array([1, 3, 5, 6, 9, 10, 14, 15, 56])
np.argwhere((a>=6) & (a<=10))

Calculating the area under a curve given a set of coordinates, without knowing the function

If you have sklearn isntalled, a simple alternative is to use sklearn.metrics.auc

This computes the area under the curve using the trapezoidal rule given arbitrary x, and y array

import numpy as np
from sklearn.metrics import auc

dx = 5
xx = np.arange(1,100,dx)
yy = np.arange(1,100,dx)

print('computed AUC using sklearn.metrics.auc: {}'.format(auc(xx,yy)))
print('computed AUC using np.trapz: {}'.format(np.trapz(yy, dx = dx)))

both output the same area: 4607.5

the advantage of sklearn.metrics.auc is that it can accept arbitrarily-spaced 'x' array, just make sure it is ascending otherwise the results will be incorrect

Simple insecure two-way data "obfuscation"?

I changed this:

public string ByteArrToString(byte[] byteArr)
    byte val;
    string tempStr = "";
    for (int i = 0; i <= byteArr.GetUpperBound(0); i++)
        val = byteArr[i];
        if (val < (byte)10)
            tempStr += "00" + val.ToString();
        else if (val < (byte)100)
            tempStr += "0" + val.ToString();
            tempStr += val.ToString();
    return tempStr;

to this:

    public string ByteArrToString(byte[] byteArr)
        string temp = "";
        foreach (byte b in byteArr)
            temp += b.ToString().PadLeft(3, '0');
        return temp;

How can I copy a Python string?

Copying a string can be done two ways either copy the location a = "a" b = a or you can clone which means b wont get affected when a is changed which is done by a = 'a' b = a[:]

Navigation bar show/hide

This code will help you.

UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] 
initWithTarget:self action:@selector(showHideNavbar:)];
[self.view addGestureRecognizer:tapGesture];

-(void) showHideNavbar:(id) sender 
// write code to show/hide nav bar here 
// check if the Navigation Bar is shown
if (self.navigationController.navigationBar.hidden == NO)
// hide the Navigation Bar
[self.navigationController setNavigationBarHidden:YES animated:YES];
// if Navigation Bar is already hidden
else if (self.navigationController.navigationBar.hidden == YES)
// Show the Navigation Bar
[self.navigationController setNavigationBarHidden:NO animated:YES];

Use of the MANIFEST.MF file in Java

The content of the Manifest file in a JAR file created with version 1.0 of the Java Development Kit is the following.

Manifest-Version: 1.0

All the entries are as name-value pairs. The name of a header is separated from its value by a colon. The default manifest shows that it conforms to version 1.0 of the manifest specification. The manifest can also contain information about the other files that are packaged in the archive. Exactly what file information is recorded in the manifest will depend on the intended use for the JAR file. The default manifest file makes no assumptions about what information it should record about other files, so its single line contains data only about itself. Special-Purpose Manifest Headers

Depending on the intended role of the JAR file, the default manifest may have to be modified. If the JAR file is created only for the purpose of archival, then the MANIFEST.MF file is of no purpose. Most uses of JAR files go beyond simple archiving and compression and require special information to be in the manifest file. Summarized below are brief descriptions of the headers that are required for some special-purpose JAR-file functions

Applications Bundled as JAR Files: If an application is bundled in a JAR file, the Java Virtual Machine needs to be told what the entry point to the application is. An entry point is any class with a public static void main(String[] args) method. This information is provided in the Main-Class header, which has the general form:

Main-Class: classname

The value classname is to be replaced with the application's entry point.

Download Extensions: Download extensions are JAR files that are referenced by the manifest files of other JAR files. In a typical situation, an applet will be bundled in a JAR file whose manifest references a JAR file (or several JAR files) that will serve as an extension for the purposes of that applet. Extensions may reference each other in the same way. Download extensions are specified in the Class-Path header field in the manifest file of an applet, application, or another extension. A Class-Path header might look like this, for example:

Class-Path: servlet.jar infobus.jar acme/beans.jar

With this header, the classes in the files servlet.jar, infobus.jar, and acme/beans.jar will serve as extensions for purposes of the applet or application. The URLs in the Class-Path header are given relative to the URL of the JAR file of the applet or application.

Package Sealing: A package within a JAR file can be optionally sealed, which means that all classes defined in that package must be archived in the same JAR file. A package might be sealed to ensure version consistency among the classes in your software or as a security measure. To seal a package, a Name header needs to be added for the package, followed by a Sealed header, similar to this:

Name: myCompany/myPackage/
Sealed: true

The Name header's value is the package's relative pathname. Note that it ends with a '/' to distinguish it from a filename. Any headers following a Name header, without any intervening blank lines, apply to the file or package specified in the Name header. In the above example, because the Sealed header occurs after the Name: myCompany/myPackage header, with no blank lines between, the Sealed header will be interpreted as applying (only) to the package myCompany/myPackage.

Package Versioning: The Package Versioning specification defines several manifest headers to hold versioning information. One set of such headers can be assigned to each package. The versioning headers should appear directly beneath the Name header for the package. This example shows all the versioning headers:

Name: java/util/
Specification-Title: "Java Utility Classes" 
Specification-Version: "1.2"
Specification-Vendor: "Sun Microsystems, Inc.".
Implementation-Title: "java.util" 
Implementation-Version: "build57"
Implementation-Vendor: "Sun Microsystems, Inc."

Visual Studio build fails: unable to copy exe-file from obj\debug to bin\debug

For me this was being caused by having a command prompt open in the targeted folder (C:\users\username\source\repos\project\project\bin\debug\app.publish).

Not sure why DEBUGGING requires access to the publish folder, but closing the command window solved the issue for me.

Trigger insert old values- values that was updated

In SQL Server 2008 you can use Change Data Capture for this. Details of how to set it up on a table are here

How to start a Process as administrator mode in C#

Here is an example of run process as administrator without Windows Prompt

  Process p = new Process();
  p.StartInfo.FileName = Server.MapPath("process.exe");
  p.StartInfo.Arguments = "";
  p.StartInfo.UseShellExecute = false;
  p.StartInfo.CreateNoWindow = true;
  p.StartInfo.RedirectStandardOutput = true;
  p.StartInfo.Verb = "runas";

background: fixed no repeat not working on mobile

I found maybe best solution for parallax effect which work on all devices.

Main thing is to set all sections with z-index greater than parallax section.

And parallax image element to set fixed with max width and height

body, html { margin: 0px; }_x000D_
section {_x000D_
  position: relative; /* Important */_x000D_
  z-index: 1; /* Important */_x000D_
  width: 100%;_x000D_
  height: 100px;_x000D_
_x000D_ { background-color: blue; }_x000D_ { background-color: red; }_x000D_
section.parallax {_x000D_
  z-index: 0; /* Important */_x000D_
section.parallax .image {_x000D_
  position: fixed; /* Important */_x000D_
  top: 0; /* Important */_x000D_
  left: 0; /* Important */_x000D_
  width: 100%; /* Important */_x000D_
  height: 100%; /* Important */_x000D_
  background-image: url(;_x000D_
  background-repeat: no-repeat;_x000D_
  background-position: center;_x000D_
  -webkit-background-size: cover;_x000D_
  -moz-background-size: cover;_x000D_
  -o-background-size: cover;_x000D_
  background-size: cover;_x000D_
<section class="blue"></section>_x000D_
<section class="parallax">_x000D_
  <div class="image"></div>_x000D_
<section class="red"></section>

Error: Can't set headers after they are sent to the client

This type of error you will get when you pass statements after sending a response.

For example:

res.send("something response");
res.send("sopmething response");

Will result in the error you are seeing, because once the response has been sent, the following res.send will not be executed.

If you want do anything, you should do it before sending the response.

Don't understand why UnboundLocalError occurs (closure)

The reason of why your code throws an UnboundLocalError is already well explained in other answers.

But it seems to me that you're trying to build something that works like itertools.count().

So why don't you try it out, and see if it suits your case:

>>> from itertools import count
>>> counter = count(0)
>>> counter
>>> next(counter)
>>> counter
>>> next(counter)
>>> counter

Get Absolute Position of element within the window in wpf

Since .NET 3.0, you can simply use *yourElement*.TranslatePoint(new Point(0, 0), *theContainerOfYourChoice*).

This will give you the point 0, 0 of your button, but towards the container. (You can also give an other point that 0, 0)

Check here for the doc.

Facebook Javascript SDK Problem: "FB is not defined"

Try to load your scripts in Head section. Moreover, it will be better if you define your scripts under some call like: document.ready, if you defined these scripts in body section

Finding the id of a parent div using Jquery

To get the id of the parent div:


Also, you can refactor your code quite a bit:

$('button').click( function() {
 var correct = Number($(this).attr('rel'));
 validate(Number($(this).siblings('input').val()), correct);

Now there is no need for a button-class

eq(0), means that you will select one element from the jQuery object, in this case element 0, thus the first element.
$(selector).siblings(siblingsSelector) will select all siblings (elements with the same parent) that match the siblingsSelector
$(selector).parents(parentsSelector) will select all parents of the elements matched by selector that match the parent selector.
Thus: $(selector).parents('div:eq(0)'); will match the first parent div of the elements matched by selector.

You should have a look at the jQuery docs, particularly selectors and traversing:

How to split page into 4 equal parts?

I did not want to add style to <body> tag and <html> tag.

    width: 100%;
    height: 100vh;
    margin: 0;
    padding: 0;

    width: 100%;
    height: 50vh;

    display: inline;
    float: left;
    width: 50%;
    height: 100%;

    top: 0;
    left: 50vh;
    background-color: red;

    top: 0;
    left: 0;
    background-color: yellow;

    top: 50vw;
    left: 0;
    background-color: blue;

    top: 50vw;
    left: 50vh;
    background-color: green;
<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <link type="text/css" rel="stylesheet" href="main.css" />

<div class='quodrant'>
    <div class='qtop'>
        <div class='quodrant1'></div>
        <div class='quodrant2'></div>
    <div class='qbottom'>
        <div class='quodrant3'></div>
        <div class='quodrant4'></div>

<script type="text/javascript" src="main.js"></script>

Or making it looks nicer.

    width: 100%;
    height: 100vh;
    margin: 0;
    padding: 0;

    width: 96%;
    height: 46vh;

    display: inline;
    float: left;
    width: 46%;
    height: 96%;
    border-radius: 30px;
    margin: 2%;

    background-color: #948be5;

    background-color: #22e235;

    background-color: #086e75;

    background-color: #7cf5f9;
<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <link type="text/css" rel="stylesheet" href="main.css" />

<div class='quodrant'>
    <div class='qtop'>
        <div class='quodrant1'></div>
        <div class='quodrant2'></div>
    <div class='qbottom'>
        <div class='quodrant3'></div>
        <div class='quodrant4'></div>

<script type="text/javascript" src="main.js"></script>

How to make a checkbox checked with jQuery?

from jQuery v1.6 use prop

to check that is checkd or not

$('input:radio').prop('checked') // will return true or false

and to make it checkd use

$("input").prop("checked", true);

How to print Two-Dimensional Array like table

public static void main(String[] args) {
    int[][] matrix = { 
                       { 1, 2, 5 }, 
                       { 3, 4, 6 },
                       { 7, 8, 9 } 

    System.out.println(" ** Matrix ** ");

    for (int rows = 0; rows < 3; rows++) {
        for (int columns = 0; columns < matrix[rows].length; columns++) {
            System.out.print(matrix[rows][columns] + "\t");

This works,add a new line in for loop of the row. When the first row will be done printing the code will jump in new line.

Gradle - Move a folder from ABC to XYZ

Your task declaration is incorrectly combining the Copy task type and project.copy method, resulting in a task that has nothing to copy and thus never runs. Besides, Copy isn't the right choice for renaming a directory. There is no Gradle API for renaming, but a bit of Groovy code (leveraging Java's File API) will do. Assuming Project1 is the project directory:

task renABCToXYZ {     doLast {         file("ABC").renameTo(file("XYZ"))     } } 

Looking at the bigger picture, it's probably better to add the renaming logic (i.e. the doLast task action) to the task that produces ABC.

How to prevent form resubmission when page is refreshed (F5 / CTRL+R)

As others have said, it is not possible to out of using post/redirect/get. But at the same time it is quite easy to do what you want to do server side.

In your POST page you simply validate the user input but do not act on it, instead you copy it into a SESSION array. You then redirect back to the main submission page again. Your main submission page starts by checking to see if the SESSION array that you are using exists, and if so copy it into a local array and unset it. From there you can act on it.

This way you only do all your main work once, achieving what you want to do.

Auto Generate Database Diagram MySQL

Try MySQL Workbench, formerly DBDesigner 4:

This has a "Reverse Engineer Database" mode:

Database -> Reverse Engineer

enter image description here

Why my regexp for hyphenated words doesn't work?

A couple of things:

  1. Your regexes need to be anchored by separators* or you'll match partial words, as is the case now
  2. You're not using the proper syntax for a non-capturing group. It's (?: not (:?

If you address the first problem, you won't need groups at all.

*That is, a blank or beginning/end of string.

'const string' vs. 'static readonly string' in C#

Here is a good breakdown of the pros and cons:

So, it appears that constants should be used when it is very unlikely that the value will ever change, or if no external apps/libs will be using the constant. Static readonly fields should be used when run-time calculation is required, or if external consumers are a factor.

Moving Git repository content to another repository preserving history

There are a lot of complicated answers, here; however, if you are not concerned with branch preservation, all you need to do is reset the remote origin, set the upstream, and push.

This worked to preserve all the commit history for me.

cd <location of local repo.>
git remote set-url origin <url>
git push -u origin master

UNC path to a folder on my local computer

On Windows, you can also use the Win32 File Namespace prefixed with \\?\ to refer to your local directories:


See this answer for description.

Sending message through WhatsApp

Currently, the only official API that you may make a GET request to:

Anyways, there is a secret API program already being ran by WhatsApp

Javascript change font color

Don't use <font color=. It's a really old fashioned way to style text and some browsers even don't even support it anymore.

caniuse lists it as obsolete, and strongly recommends not using the <font> tag. The same is with MDN

Do not use this element! Though once normalized in HTML 3.2, it was deprecated in HTML 4.01, at the same time as all elements related to styling only, then obsoleted in HTML5.

Starting with HTML 4, HTML does not convey styling information anymore (outside the element or the style attribute of each element). For any new web development, styling should be written using CSS only.

The former behavior of the element can be achieved, and even better controlled using the CSS Fonts CSS properties.

If we look at when the 4.01 standard was published we see it was published in 1999

published html5 standard

where <font> was officially deprecated, meaning it is still supported but shouldn't be used anymore as it will go away in the newer standard.

And in the html5 standard released in August 2014 it was deemed obsolete and non conforming.

To achieve the desired effect use spans and css:

function givemecolor(thecolor,thetext)
    return '<span style="color:'+thecolor+'">'+thetext+'</span>';
document.write(givemecolor('green',"Hello, I'm green"));
document.write(givemecolor('red',"Hello, I'm red"));
body {
  background: #333;
  color: #eee;


This question and answer are from 2012 and now I wouldn't recommend using document.write as it needs to be executed when the document is rendered first time. I had used it back then because I assumed OP was wishing to use it in such a way. I'd recommend using a more conventional way to insert the custom elements you wish to use, at the place you wish to insert them, without relying on document rendering and when and where the script is executed.


function givemecolor(thecolor,thetext)
    var span = document.createElement('span'); = thecolor;
    span.innerText = thetext;
    return span;
var container = document.getElementById('textholder');
container.append(givemecolor('green', "Hello I'm green"));
container.append(givemecolor('red', "Hello I'm red"));
body {
 background: #333;
 color: #eee;
<h1> some title </h1>
<div id="textholder">
<p> some other text </p>


function givemecolor(thecolor, thetext)
    var $span = $("<span>");
    return $span;
var $container = $('#textholder');
$container.append(givemecolor('green', "Hello I'm green"));
$container.append(givemecolor('red', "Hello I'm red"));
body {
 background: #333;
 color: #eee;
<script src=""></script>
<h1> some title </h1>
<div id="textholder">
<p> some other text </p>

PHP Include for HTML?

First: what the others said. Forget the echo statement and just write your navbar.php as a regular HTML file.

Second: your include paths are probably messed up. To make sure you include files that are in the same directory as the current file, use __DIR__:

include __DIR__.'/navbar.php'; // PHP 5.3 and later
include dirname(__FILE__).'/navbar.php'; // PHP 5.2

Debugging the error "gcc: error: x86_64-linux-gnu-gcc: No such file or directory"

You just need to enter this command:

sudo apt-get install gcc

Error: "Could Not Find Installable ISAM"

Have you checked this In particular, whether you have Msrd3x40.dll.

You may also like to check that you have the latest version of Jet:

Iterating through populated rows

It looks like you just hard-coded the row and column; otherwise, a couple of small tweaks, and I think you're there:

Dim sh As Worksheet
Dim rw As Range
Dim RowCount As Integer

RowCount = 0

Set sh = ActiveSheet
For Each rw In sh.Rows

  If sh.Cells(rw.Row, 1).Value = "" Then
    Exit For
  End If

  RowCount = RowCount + 1

Next rw

MsgBox (RowCount)

load Js file in HTML

I had the same problem, and found the answer. If you use node.js with express, you need to give it its own function in order for the js file to be reached. For example:

const script = path.join(__dirname, 'script.js');
const server = express().get('/', (req, res) => res.sendFile(script))

Converting double to string with N decimals, dot as decimal separator, and no thousand separator

I prefer to use ToString() and IFormatProvider.

double value = 100000.3
Console.WriteLine(value.ToString("0,0.00", new CultureInfo("en-US", false)));

Output: 10,000.30

Dropdown select with images

I am a little to late on this, but you can do this using a simple bootstrap drop down and then do your code on select change event in any language or framework. (This is just a very basic solution, for other people like me who are just starting out and looking for a solution for a small simple project.)

<div class="dropdown">
    <button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown" aria-haspopup="true" aria-expanded="true">
        Select Image
        <span class="caret"></span>
    <ul class="dropdown-menu" aria-labelledby="dropdownMenu1">
        <li> <a style="background-image: url(../Content/Images/Backgrounds/background.png);height:100px;width:300px" class="img-thumbnail" href=""> </a></li>
        <li role="separator" class="divider"></li>
        <li> <a style="background-image: url(../Content/Images/Backgrounds/background.png);height:100px;width:300px" class="img-thumbnail" href=""> </a></li>

Make Bootstrap 3 Tabs Responsive

I have created a directive in agularJS supported with ng-bootStrap components!#tabs

here I share the code that I implemented



Using ExcelDataReader to read Excel data starting from a particular cell

To be more clear, I will begin at the beginning.

I will rely on the sample code found in, but with some modifications to avoid inconveniences.

The following code detects the file format, either xls or xlsx.

FileStream stream = File.Open(filePath, FileMode.Open, FileAccess.Read);
IExcelDataReader excelReader;

//1. Reading Excel file
if (Path.GetExtension(filePath).ToUpper() == ".XLS")
    //1.1 Reading from a binary Excel file ('97-2003 format; *.xls)
    excelReader = ExcelReaderFactory.CreateBinaryReader(stream);
    //1.2 Reading from a OpenXml Excel file (2007 format; *.xlsx)
    excelReader = ExcelReaderFactory.CreateOpenXmlReader(stream);

//2. DataSet - The result of each spreadsheet will be created in the result.Tables
DataSet result = excelReader.AsDataSet();

//3. DataSet - Create column names from first row
excelReader.IsFirstRowAsColumnNames = false;

Now we can access the file contents in a more convenient way. I use DataTable for this. The following is an example to access a specific cell, and print its value in the console:

DataTable dt = result.Tables[0];

If you do not want to do a DataTable, you can do the same as follows:


It is important not try to read beyond the limits of the table, for this you can see the number of rows and columns as follows:


Finally, when you're done, you should close the reader and free resources:

//5. Free resources (IExcelDataReader is IDisposable)

I hope you find it useful.

(I understand that the question is old, but I make this contribution to enhance the knowledge base, because there is little material about particular implementations of this library).

How to convert a string to character array in c (or) how to extract a single char form string?

In C, a string is actually stored as an array of characters, so the 'string pointer' is pointing to the first character. For instance,

char myString[] = "This is some text";

You can access any character as a simple char by using myString as an array, thus:

char myChar = myString[6];
printf("%c\n", myChar); // Prints s

Hope this helps! David

How do you overcome the HTML form nesting limitation?

Alternatively you could assign the form actiob on the fly...might not be the best solution, but sure does relieve the server-side logic...

<form name="frm" method="post">  
    <input type="submit" value="One" onclick="javascript:this.form.action='1.htm'" />  
    <input type="submit" value="Two" onclick="javascript:this.form.action='2.htm'" />  

Execute method on startup in Spring

If by "application startup" you mean "application context startup", then yes, there are many ways to do this, the easiest (for singletons beans, anyway) being to annotate your method with @PostConstruct. Take a look at the link to see the other options, but in summary they are:

  • Methods annotated with @PostConstruct
  • afterPropertiesSet() as defined by the InitializingBean callback interface
  • A custom configured init() method

Technically, these are hooks into the bean lifecycle, rather than the context lifecycle, but in 99% of cases, the two are equivalent.

If you need to hook specifically into the context startup/shutdown, then you can implement the Lifecycle interface instead, but that's probably unnecessary.

Tomcat is not deploying my web project from Eclipse

The only way I found which works for me is adding an entry into the "Web Deployment Assembly"

Project webapp > Properties > Deployment Assembly
Add ...
Source : "/target/classes"
Deploy Path : "WEB-INF/classes"

Apache 2.4 - Request exceeded the limit of 10 internal redirects due to probable configuration error

This problem can be caused by requests for certain files that don't exist. For example, requests for files in wp-content/uploads/ where the file does not exist.

If this is the situation you're seeing, you can solve the problem by going to .htaccess and changing this line:

RewriteRule ^(wp-(content|admin|includes).*) $1 [L]


RewriteRule ^(wp-(content|admin|includes).*) - [L]

The underlying issue is that the rule above triggers a rewrite to the exact same url with a slash in front and because there was a rewrite, the newly rewritten request goes back through the rules again and the same rule is triggered. By changing that line's "$1" to "-", no rewrite happens and so the rewriting process does not start over again with the same URL.

It's possible that there's a difference in how apache 2.2 and 2.4 handle this situation of only-difference-is-a-slash-in-front and that's why the default rules provided by WordPress aren't working perfectly.

Eclipse IDE for Java - Full Dark Theme

You can use this great theme from above and add predefined theme only for editor from this site:

(I use guari and retta and I think that looks real good :)

I hope that it will help someone :)

Header set Access-Control-Allow-Origin in .htaccess doesn't work

try this:

<IfModule mod_headers.c>
     Header set Access-Control-Allow-Credentials true
     Header set Access-Control-Allow-Origin "your domain"
     Header set Access-Control-Allow-Headers "X-Requested-With"

It's preferable to allow a list of know trusted host.

How can I find out which server hosts LDAP on my windows domain?

If you're using AD you can use serverless binding to locate a domain controller for the default domain, then use LDAP://rootDSE to get information about the directory server, as described in the linked article.

Python: How would you save a simple settings/config file?

try using cfg4py:

  1. Hierarchichal design, mulitiple env supported, so never mess up dev settings with production site settings.
  2. Code completion. Cfg4py will convert your yaml into a python class, then code completion is available while you typing your code.
  3. many more..

DISCLAIMER: I'm the author of this module

Choosing bootstrap vs material design

As far as I know you can use all mentioned technologies separately or together. It's up to you. I think you look at the problem from the wrong angle. Material Design is just the way particular elements of the page are designed, behave and put together. Material Design provides great UI/UX, but it relies on the graphic layout (HTML/CSS) rather than JS (events, interactions).

On the other hand, AngularJS and Bootstrap are front-end frameworks that can speed up your development by saving you from writing tons of code. For example, you can build web app utilizing AngularJS, but without Material Design. Or You can build simple HTML5 web page with Material Design without AngularJS or Bootstrap. Finally you can build web app that uses AngularJS with Bootstrap and with Material Design. This is the best scenario. All technologies support each other.

  1. Bootstrap = responsive page
  2. AngularJS = MVC
  3. Material Design = great UI/UX

You can check awesome material design components for AngularJS:

enter image description here

Demo: enter image description here

How to enable directory listing in apache web server

See if you are able to access/list the '/icons/' directory. This is useful to test the behavior of Directory in Apache.

for eg : You might be having below config by default in your httpd.conf file.So hit the url : IP:Port/icons/ and see if it list the icons or not.You can also try by putting the 'directory/folder' inside the 'var/www/icons'.

Alias /icons/ "/var/www/icons/"

<Directory "/var/www/icons">
    Options Indexes MultiViews
    AllowOverride None
    Require all granted

If it does works then you can crosscheck or modify your custom directory configuration with '' configuration.

AngularJS - Find Element with attribute

You haven't stated where you're looking for the element. If it's within the scope of a controller, it is possible, despite the chorus you'll hear about it not being the 'Angular Way'. The chorus is right, but sometimes, in the real world, it's unavoidable. (If you disagree, get in touch—I have a challenge for you.)

If you pass $element into a controller, like you would $scope, you can use its find() function. Note that, in the jQueryLite included in Angular, find() will only locate tags by name, not attribute. However, if you include the full-blown jQuery in your project, all the functionality of find() can be used, including finding by attribute.

So, for this HTML:

<div ng-controller='MyCtrl'>
        <div name='foo' class='myElementClass'>this one</div>

This AngularJS code should work:

angular.module('MyClient').controller('MyCtrl', [
    function ($scope, $element, $log) {

        // Find the element by its class attribute, within your controller's scope
        var myElements = $element.find('.myElementClass');

        // myElements is now an array of jQuery DOM elements

        if (myElements.length == 0) {
            // Not found. Are you sure you've included the full jQuery?
        } else {
            // There should only be one, and it will be element 0
            $log.debug(myElements[0].name); // "foo"


How to pass params with history.push/Link/Redirect in react-router v4?

If you need to pass URL params

theres a great post explanation by Tyler McGinnis on his site, Link to the post

here are code examples:

  1. on the history.push component:


  2. on the router component you define the route:

    <Route path='/home:myKey' component={Home} />

  3. on the Home component:

    const { myKey } = this.props.match.params
    console.log(myKey )

Best way to structure a tkinter application?

OOP should be the approach and frame should be a class variable instead of instance variable.

from Tkinter import *
class App:
  def __init__(self, master):
    frame = Frame(master)
    self.button = Button(frame, 
                         text="QUIT", fg="red",
    self.slogan = Button(frame,
  def write_slogan(self):
    print "Tkinter is easy to use!"

root = Tk()
app = App(root)

enter image description here


FAIL - Application at context path /Hello could not be started

Your web.xml ends with <web-app>, but must end with </web-app>

Which by the way is almost literally what the exception tells you.

How do I open workbook programmatically as read-only?

Check out the language reference:

expression.Open(FileName, UpdateLinks, ReadOnly, Format, Password, WriteResPassword, IgnoreReadOnlyRecommended, Origin, Delimiter, Editable, Notify, Converter, AddToMru, Local, CorruptLoad)

How to query MongoDB with "like"?

If using node.js, it says that you can write this:

db.collection.find( { field: /acme.*corp/i } );
db.collection.find( { field: { $regex: 'acme.*corp', $options: 'i' } } );

Also, you can write this:

db.collection.find( { field: new RegExp('acme.*corp', 'i') } );

How to vertically align <li> elements in <ul>?

You can use flexbox for this.

ul {
    display: flex;
    align-items: center;

A detailed explanation of how to use flexbox can be found here.

Detecting input change in jQuery?

This covers every change to an input using jQuery 1.7 and above:

$(".inputElement").on("input", null, null, callbackFunction);

How to check if a value exists in a dictionary (python)

In Python 3, you can use

"one" in d.values()

to test if "one" is among the values of your dictionary.

In Python 2, it's more efficient to use

"one" in d.itervalues()


Note that this triggers a linear scan through the values of the dictionary, short-circuiting as soon as it is found, so this is a lot less efficient than checking whether a key is present.

CURLOPT_RETURNTRANSFER set to true doesnt work on hosting server

Just try this line:

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);


curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

How to get file name from file path in android

FilenameUtils to the rescue:

String filename = FilenameUtils.getName("/storage/sdcard0/DCIM/Camera/1414240995236.jpg");

Get Android .apk file VersionName or VersionCode WITHOUT installing apk


var ver: String = packageManager.getPackageInfo(packageName, 0).versionName

Why does git say "Pull is not possible because you have unmerged files"?

There was same issue with me
In my case, steps are as below-

  1. Removed all file which was being start with U (unmerged) symbol. as-

U   project/app/pages/file1/file.ts
U   project/www/assets/file1/file-name.html
  1. Pull code from master

$ git pull origin master
  1. Checked for status

 $ git status

Here is the message which It appeared-
and have 2 and 1 different commit each, respectively.
(use "git pull" to merge the remote branch into yours)
You have unmerged paths.
(fix conflicts and run "git commit")

Unmerged paths:
(use "git add ..." to mark resolution)

both modified:   project/app/pages/file1/file.ts
both modified:   project/www/assets/file1/file-name.html
  1. Added all new changes -

    $ git add project/app/pages/file1/file.ts
  1. Commit changes on head-

$ git commit -am "resolved conflict of the app."
  1. Pushed the code -

$ git push origin master

Which turn may issue resolved with this image - enter image description here

Is there an easy way to check the .NET Framework version?

Something like this should do it. Just grab the value from the registry

For .NET 1-4:

Framework is the highest installed version, SP is the service pack for that version.

RegistryKey installed_versions = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\NET Framework Setup\NDP");
string[] version_names = installed_versions.GetSubKeyNames();
//version names start with 'v', eg, 'v3.5' which needs to be trimmed off before conversion
double Framework = Convert.ToDouble(version_names[version_names.Length - 1].Remove(0, 1), CultureInfo.InvariantCulture);
int SP = Convert.ToInt32(installed_versions.OpenSubKey(version_names[version_names.Length - 1]).GetValue("SP", 0));

For .NET 4.5+ (from official documentation):

using System;
using Microsoft.Win32;


private static void Get45or451FromRegistry()
    using (RegistryKey ndpKey = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry32).OpenSubKey("SOFTWARE\\Microsoft\\NET Framework Setup\\NDP\\v4\\Full\\")) {
        int releaseKey = Convert.ToInt32(ndpKey.GetValue("Release"));
        if (true) {
            Console.WriteLine("Version: " + CheckFor45DotVersion(releaseKey));


// Checking the version using >= will enable forward compatibility,  
// however you should always compile your code on newer versions of 
// the framework to ensure your app works the same. 
private static string CheckFor45DotVersion(int releaseKey)
    if (releaseKey >= 461808) {
        return "4.7.2 or later";
    if (releaseKey >= 461308) {
        return "4.7.1 or later";
    if (releaseKey >= 460798) {
        return "4.7 or later";
    if (releaseKey >= 394802) {
        return "4.6.2 or later";
    if (releaseKey >= 394254) {
        return "4.6.1 or later";
    if (releaseKey >= 393295) {
        return "4.6 or later";
    if (releaseKey >= 393273) {
        return "4.6 RC or later";
    if ((releaseKey >= 379893)) {
        return "4.5.2 or later";
    if ((releaseKey >= 378675)) {
        return "4.5.1 or later";
    if ((releaseKey >= 378389)) {
        return "4.5 or later";
    // This line should never execute. A non-null release key should mean 
    // that 4.5 or later is installed. 
    return "No 4.5 or later version detected";

Disable same origin policy in Chrome

  1. Create a new shortcut:

Create new shortcut

  1. Paste the following path:

"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" "C:\Program Files\Google\Chrome\Application\chrome.exe" --disable-web-security --user-data-dir="c:\temp\chrome"

Paste the path

  1. Name it:

Unsafe Chrome.exe

enter image description here

Now you have an unsafe version of Google Chrome on desktop to use it for debugging front-end applications without any CORS problems.

tomcat - CATALINA_BASE and CATALINA_HOME variables

That is the parent folder of bin which contains tomcat.exe file:

CATALINA_HOME='C:\Program Files\Apache Software Foundation\Tomcat 6.0'


SQL update trigger only when column is modified

One should check if QtyToRepair is updated at first.

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
    IF UPDATE (QtyToRepair) 
        SET modified = GETDATE()
           , ModifiedUser = SUSER_NAME()
           , ModifiedHost = HOST_NAME()
            ON S.OrderNo = I.OrderNo and S.PartNumber =    I.PartNumber
        WHERE S.QtyToRepair <> I.QtyToRepair

Android: remove left margin from actionbar's custom layout

Create toolbar like this:

< xmlns:android=""

please follow this link for more - Android Tips

Laravel Check If Related Model Exists

I prefer to use exists method:


to check if related model exists or not. It's working fine on Laravel 5.2

Type List vs type ArrayList in Java

It is considered good style to store a reference to a HashSet or TreeSet in a variable of type Set.

Set<String> names = new HashSet<String>();

This way, you have to change only one line if you decide to use a TreeSet instead.

Also, methods that operate on sets should specify parameters of type Set:

public static void print(Set<String> s)

Then the method can be used for all set implementations.

In theory, we should make the same recommendation for linked lists, namely to save LinkedList references in variables of type List. However, in the Java library, the List interface is common to both the ArrayList and the LinkedList class. In particular, it has get and set methods for random access, even though these methods are very inefficient for linked lists.

You can’t write efficient code if you don’t know whether random access is efficient or not.

This is plainly a serious design error in the standard library, and I cannot recommend using the List interface for that reason.

To see just how embarrassing that error is, have a look at the source code for the binarySearch method of the Collections class. That method takes a List parameter, but binary search makes no sense for a linked list. The code then clumsily tries to discover whether the list is a linked list, and then switches to a linear search!

The Set interface and the Map interface, are well designed, and you should use them.

Getting "Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?" when installing lxml through pip

set STATICBUILD=true && pip install lxml

run this command instead, must have VS C++ compiler installed first

It works for me with Python 3.5.2 and Windows 7

How to set up file permissions for Laravel?

We've run into many edge cases when setting up permissions for Laravel applications. We create a separate user account (deploy) for owning the Laravel application folder and executing Laravel commands from the CLI, and run the web server under www-data. One issue this causes is that the log file(s) may be owned by www-data or deploy, depending on who wrote to the log file first, obviously preventing the other user from writing to it in the future.

I've found that the only sane and secure solution is to use Linux ACLs. The goal of this solution is:

  1. To allow the user who owns/deploys the application read and write access to the Laravel application code (we use a user named deploy).
  2. To allow the www-data user read access to Laravel application code, but not write access.
  3. To prevent any other users from accessing the Laravel application code/data at all.
  4. To allow both the www-data user and the application user (deploy) write access to the storage folder, regardless of which user owns the file (so both deploy and www-data can write to the same log file for example).

We accomplish this as follows:

  1. All files within the application/ folder are created with the default umask of 0022, which results in folders having drwxr-xr-x permissions and files having -rw-r--r--.
  2. sudo chown -R deploy:deploy application/ (or simply deploy your application as the deploy user, which is what we do).
  3. chgrp www-data application/ to give the www-data group access to the application.
  4. chmod 750 application/ to allow the deploy user read/write, the www-data user read-only, and to remove all permissions to any other users.
  5. setfacl -Rdm u:www-data:rwx,u:deploy:rwx application/storage/ to set the default permissions on the storage/ folder and all subfolders. Any new folders/files created in the storage folder will inherit these permissions (rwx for both www-data and deploy).
  6. setfacl -Rm u:www-data:rwX,u:deploy:rwX application/storage/ to set the above permissions on any existing files/folders.

jQuery autoComplete view all on click?

You can also use search function without parameters:

jQuery("#id").autocomplete("search", "");

PHP cURL custom headers

Use the following Syntax

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,"");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,$vars);  //Post Fields
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$headers = [
    'X-Apple-Tz: 0',
    'X-Apple-Store-Front: 143444,12',
    'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
    'Accept-Encoding: gzip, deflate',
    'Accept-Language: en-US,en;q=0.5',
    'Cache-Control: no-cache',
    'Content-Type: application/x-www-form-urlencoded; charset=utf-8',
    'Referer:', //Your referrer address
    'User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:28.0) Gecko/20100101 Firefox/28.0',
    'X-MicrosoftAjax: Delta=true'

curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

$server_output = curl_exec ($ch);

curl_close ($ch);

print  $server_output ;

Can you do greater than comparison on a date in a Rails 3 search?

Rails 6.1 added a new 'syntax' for comparison operators in where conditions, for example:

Post.where('id >': 9)
Post.where('id >=': 9)
Post.where('id <': 3)
Post.where('id <=': 3)

So your query can be rewritten as follows:

  .where(user_id:, notetype: p[:note_type], 'date >', p[:date])
  .order(date: :asc, created_at: :asc)

Here is a link to PR where you can find more examples.

What's the difference between OpenID and OAuth?

OpenID is about authentication (ie. proving who you are), OAuth is about authorisation (ie. to grant access to functionality/data/etc.. without having to deal with the original authentication).

OAuth could be used in external partner sites to allow access to protected data without them having to re-authenticate a user.

The blog post "OpenID versus OAuth from the user’s perspective" has a simple comparison of the two from the user's perspective and "OAuth-OpenID: You’re Barking Up the Wrong Tree if you Think They’re the Same Thing" has more information about it.

What exactly is LLVM?

LLVM is basically a library used to build compilers and/or language oriented software. The basic gist is although you have gcc which is probably the most common suite of compilers, it is not built to be re-usable ie. it is difficult to take components from gcc and use it to build your own application. LLVM addresses this issue well by building a set of "modular and reusable compiler and toolchain technologies" which anyone could use to build compilers and language oriented software.

How do I write out a text file in C# with a code page other than UTF-8?

using System.IO;
using System.Text;

using (StreamWriter sw = new StreamWriter(File.Open(myfilename, FileMode.Create), Encoding.WhateverYouWant))
    sw.WriteLine("my text...");     

An alternate way of getting your encoding:

using System.IO;
using System.Text;

using (var sw  = new StreamWriter(File.Open(@"c:\myfile.txt", FileMode.CreateNew), Encoding.GetEncoding("iso-8859-1"))) {
    sw.WriteLine("my text...");             

Check out the docs for the StreamWriter constructor.

PadLeft function in T-SQL

This is what I normally use when I need to pad a value.

SET @PaddedValue = REPLICATE('0', @Length - LEN(@OrigValue)) + CAST(@OrigValue as VARCHAR)

iPhone X / 8 / 8 Plus CSS media queries

Here are some of the following media queries for iPhones. Here is the ref link

        /* iphone 3 */
        @media only screen and (min-device-width: 320px) and (max-device-height: 480px) and (-webkit-device-pixel-ratio: 1) { }
        /* iphone 4 */
        @media only screen and (min-device-width: 320px) and (max-device-height: 480px) and (-webkit-device-pixel-ratio: 2) { }
        /* iphone 5 */
        @media only screen and (min-device-width: 320px) and (max-device-height: 568px) and (-webkit-device-pixel-ratio: 2) { }
        /* iphone 6, 6s, 7, 8 */
        @media only screen and (min-device-width: 375px) and (max-device-height: 667px) and (-webkit-device-pixel-ratio: 2) { }
        /* iphone 6+, 6s+, 7+, 8+ */
        @media only screen and (min-device-width: 414px) and (max-device-height: 736px) and (-webkit-device-pixel-ratio: 3) { }
        /* iphone X , XS, 11 Pro, 12 Mini */
        @media only screen and (min-device-width: 375px) and (max-device-height: 812px) and (-webkit-device-pixel-ratio: 3) { }

        /* iphone 12, 12 Pro */
        @media only screen and (min-device-width: 390px) and (max-device-height: 844px) and (-webkit-device-pixel-ratio: 3) { }
        /* iphone XR, 11 */
        @media only screen and (min-device-width : 414px) and (max-device-height : 896px) and (-webkit-device-pixel-ratio : 2) { }
        /* iphone XS Max, 11 Pro Max */
        @media only screen and (min-device-width : 414px) and (max-device-height : 896px) and (-webkit-device-pixel-ratio : 3) { }

        /* iphone 12 Pro Max */
        @media only screen and (min-device-width : 428px) and (max-device-height : 926px) and (-webkit-device-pixel-ratio : 3) { }

Event handler not working on dynamic content

You have to add the selector parameter, otherwise the event is directly bound instead of delegated, which only works if the element already exists (so it doesn't work for dynamically loaded content).


Change your code to

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

The jQuery set receives the event then delegates it to elements matching the selector given as argument. This means that contrary to when using live, the jQuery set elements must exist when you execute the code.

As this answers receives a lot of attention, here are two supplementary advises :

1) When it's possible, try to bind the event listener to the most precise element, to avoid useless event handling.

That is, if you're adding an element of class b to an existing element of id a, then don't use

$(document.body).on('click', '#a .b', function(){

but use

$('#a').on('click', '.b', function(){

2) Be careful, when you add an element with an id, to ensure you're not adding it twice. Not only is it "illegal" in HTML to have two elements with the same id but it breaks a lot of things. For example a selector "#c" would retrieve only one element with this id.

android: how to change layout on button click?

The logcat shows the error, you should call super.onCreate(savedInstanceState) :

public void onCreate(Bundle savedInstanceState){
    //... your code

How to change plot background color?

One method is to manually set the default for the axis background color within your script (see Customizing matplotlib):

import matplotlib.pyplot as plt
plt.rcParams['axes.facecolor'] = 'black'

This is in contrast to Nick T's method which changes the background color for a specific axes object. Resetting the defaults is useful if you're making multiple different plots with similar styles and don't want to keep changing different axes objects.

Note: The equivalent for

fig = plt.figure()

from your question is:

plt.rcParams['figure.facecolor'] = 'black'

Setting a divs background image to fit its size?

You can achieve this with the background-size property, which is now supported by most browsers.

To scale the background image to fit inside the div:

background-size: contain;

To scale the background image to cover the whole div:

background-size: cover;

PHP page redirect

Simple way is to use:

  echo '<script>window.location.href = "the-target-page.php";</script>';

How can I change the color of AlertDialog title and the color of the line under it

Instead of using divider in dialog, use the view in the custom layout and set the layout as custom layout in dialog.


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

        android:textSize="20sp" />

        android:background="@color/txt_dark_grey" />


            android:layout_height="wrap_content" />

public void showPopUp(String title, String text) {

    LayoutInflater inflater = getLayoutInflater();
    View alertLayout = inflater.inflate(R.layout.custom_popup, null);

    TextView txtContent = alertLayout.findViewById(;

    TextView txtTitle = alertLayout.findViewById(;

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

    alert.setPositiveButton("Done", new DialogInterface.OnClickListener() {

        public void onClick(DialogInterface dialog, int which) {

    AlertDialog dialog = alert.create();;

Best way to "push" into C# array

Check out this documentation page:

The Add function is the first one under Methods.

Elevating process privilege programmatically?

You can indicate the new process should be started with elevated permissions by setting the Verb property of your startInfo object to 'runas', as follows:

startInfo.Verb = "runas";

This will cause Windows to behave as if the process has been started from Explorer with the "Run as Administrator" menu command.

This does mean the UAC prompt will come up and will need to be acknowledged by the user: if this is undesirable (for example because it would happen in the middle of a lengthy process), you'll need to run your entire host process with elevated permissions by Create and Embed an Application Manifest (UAC) to require the 'highestAvailable' execution level: this will cause the UAC prompt to appear as soon as your app is started, and cause all child processes to run with elevated permissions without additional prompting.

Edit: I see you just edited your question to state that "runas" didn't work for you. That's really strange, as it should (and does for me in several production apps). Requiring the parent process to run with elevated rights by embedding the manifest should definitely work, though.

How to add new column to MYSQL table?

Based on your comment it looks like your'e only adding the new column if: mysql_query("SELECT * FROM assessment"); returns false. That's probably not what you wanted. Try removing the '!' on front of $sql in the first 'if' statement. So your code will look like:

$sql=mysql_query("SELECT * FROM assessment");
if ($sql) {
 mysql_query("ALTER TABLE assessment ADD q6 INT(1) NOT NULL AFTER q5");
 echo 'Q6 created'; 

Android - How to regenerate R class?

I had a similar problem where the file was not being regenerated after I'd added some icons and layout files. I tried cleaning and rebuilding and things got worse since then the original file was gone and still wasn't regenerated. Eventually it dawned on me that there must be compiler errors for the compiler that generates and we aren't being shown those in the console. Fortunately, I had noticed earlier that

  1. it's an error if one .xml file refers to another which is non-existent and
  2. it's an error to have upper case letters in your file names (why is that forbidden, I LOVE camel case).

Anyways, after renaming my icons and .xml files to all lowercase and then fixing all the references inside the .xml files, voila, was regenerated. Just in time to feel good when I stopped for lunch :-)

How do I add a auto_increment primary key in SQL Server database?

You can also perform this action via SQL Server Management Studio.

Right click on your selected table -> Modify

Right click on the field you want to set as PK --> Set Primary Key

Under Column Properties set "Identity Specification" to Yes, then specify the starting value and increment value.

Then in the future if you want to be able to just script this kind of thing out you can right click on the table you just modified and select


so that you can see for yourself the correct syntax to perform this action.

How to read text file in JavaScript

Yeah it is possible with FileReader, I have already done an example of this, here's the code:

<!DOCTYPE html>
    <title>Read File (via User Input selection)</title>
    <script type="text/javascript">
    var reader; //GLOBAL File Reader object for demo purpose only

     * Check for the various File API support.
    function checkFileAPI() {
        if (window.File && window.FileReader && window.FileList && window.Blob) {
            reader = new FileReader();
            return true; 
        } else {
            alert('The File APIs are not fully supported by your browser. Fallback required.');
            return false;

     * read text input
    function readText(filePath) {
        var output = ""; //placeholder for text output
        if(filePath.files && filePath.files[0]) {           
            reader.onload = function (e) {
                output =;
            };//end onload()
        }//end if html5 filelist support
        else if(ActiveXObject && filePath) { //fallback to IE 6-8 support via ActiveX
            try {
                reader = new ActiveXObject("Scripting.FileSystemObject");
                var file = reader.OpenTextFile(filePath, 1); //ActiveX File Object
                output = file.ReadAll(); //text contents of file
                file.Close(); //close file "input stream"
            } catch (e) {
                if (e.number == -2146827859) {
                    alert('Unable to access local files due to browser security settings. ' + 
                     'To overcome this, go to Tools->Internet Options->Security->Custom Level. ' + 
                     'Find the setting for "Initialize and script ActiveX controls not marked as safe" and change it to "Enable" or "Prompt"'); 
        else { //this is where you could fallback to Java Applet, Flash or similar
            return false;
        return true;

     * display content using a basic HTML replacement
    function displayContents(txt) {
        var el = document.getElementById('main'); 
        el.innerHTML = txt; //display output in DOM
<body onload="checkFileAPI();">
    <div id="container">    
        <input type="file" onchange='readText(this)' />
        <h3>Contents of the Text file:</h3>
        <div id="main">

It's also possible to do the same thing to support some older versions of IE (I think 6-8) using the ActiveX Object, I had some old code which does that too but its been a while so I'll have to dig it up I've found a solution similar to the one I used courtesy of Jacky Cui's blog and edited this answer (also cleaned up code a bit). Hope it helps.

Lastly, I just read some other answers that beat me to the draw, but as they suggest, you might be looking for code that lets you load a text file from the server (or device) where the JavaScript file is sitting. If that's the case then you want AJAX code to load the document dynamically which would be something as follows:

<!DOCTYPE html>
<head><meta charset="utf-8" />
<title>Read File (via AJAX)</title>
<script type="text/javascript">
var reader = new XMLHttpRequest() || new ActiveXObject('MSXML2.XMLHTTP');

function loadFile() {'get', 'test.txt', true); 
    reader.onreadystatechange = displayContents;

function displayContents() {
    if(reader.readyState==4) {
        var el = document.getElementById('main');
        el.innerHTML = reader.responseText;

<div id="container">
    <input type="button" value="test.txt"  onclick="loadFile()" />
    <div id="main">

How to change XAMPP apache server port?

To answer the original question:

To change the XAMPP Apache server port here the procedure :

1. Choose a free port number

The default port used by Apache is 80.

Take a look to all your used ports with Netstat (integrated to XAMPP Control Panel).

Screenshot of xampp control netstat

Then you can see all used ports and here we see that the 80port is already used by System.

screenshot netstat port 80

Choose a free port number (8012, for this exemple).

2. Edit the file "httpd.conf"

This file should be found in C:\xampp\apache\conf on Windows or in bin/apache for Linux.:

Listen 80
ServerName localhost:80

Replace them by:

Listen 8012
ServerName localhost:8012

Save the file.

Access to : http://localhost:8012 for check if it's work.

If not, you must to edit the http-ssl.conf file as explain in step 3 below. ?

3. Edit the file "http-ssl.conf"

This file should be found in C:\xampp\apache\conf\extra on Windows or see this link for Linux.

Locate the following lines:

Listen 443
<VirtualHost _default_:443>
ServerName localhost:443

Replace them by with a other port number (8013 for this example) :

Listen 8013
<VirtualHost _default_:8013>
ServerName localhost:8013

Save the file.

Restart the Apache Server.

Access to : http://localhost:8012 for check if it's work.

4. Configure XAMPP Apache server settings

If your want to access localhost without specify the port number in the URL
http://localhost instead of http://localhost:8012.

  • Open Xampp Control Panel
  • Go to Config ? Service and Port Settings ? Apache
  • Replace the Main Port and SSL Port values ??with those chosen (e.g. 8012 and 8013).
  • Save Service settings
  • Save Configuration of Control Panel
  • Restart the Apache Server xampp apache setting port It should work now.

4.1. Web browser configuration

If this configuration isn't hiding port number in URL it's because your web browser is not configured for. See : Tools ? Options ? General ? Connection Settings... will allow you to choose different ports or change proxy settings.

4.2. For the rare cases of ultimate bad luck

If step 4 and Web browser configuration are not working for you the only way to do this is to change back to 80, or to install a listener on port 80 (like a proxy) that redirects all your traffic to port 8012.

To answer your problem :

If you still have this message in Control Panel Console :

Apache Started [Port 80]

  • Find location of xampp-control.exe file (probably in C:\xampp)
  • Create a file XAMPP.INI in that directory (so XAMPP.ini and xampp-control.exe are in the same directory)

Put following lines in the XAMPP.INI file:

apache = 8012

Now , you will always get:

Apache started [Port 8012]

Please note that, this is for display purpose only. It has no relation with your httpd.conf.

AttributeError: module 'cv2.cv2' has no attribute 'createLBPHFaceRecognizer'

if you are using python3.x and opencv==4.1.0 then use following commands First of all

python -m pip install --user opencv-contrib-python

after that use this in the python script


How to get an enum value from a string value in Java?

Use the pattern from Joshua Bloch, Effective Java:

(simplified for brevity)

enum MyEnum {

    private String name;

    private static final Map<String,MyEnum> ENUM_MAP;

    MyEnum (String name) { = name;

    public String getName() {

    // Build an immutable map of String name to enum pairs.
    // Any Map impl can be used.

    static {
        Map<String,MyEnum> map = new ConcurrentHashMap<String, MyEnum>();
        for (MyEnum instance : MyEnum.values()) {
        ENUM_MAP = Collections.unmodifiableMap(map);

    public static MyEnum get (String name) {
        return ENUM_MAP.get(name.toLowerCase());

Also see:

Oracle Java Example using Enum and Map of instances

Execution order of of static blocks in an Enum type

How can I lookup a Java enum from its String value

What's the CMake syntax to set and use variables?

Here are a couple basic examples to get started quick and dirty.

One item variable

Set variable:


Use variable:


Multi-item variable (ie. list)

Set variable:


Use variable:

add_executable(program "${PROGRAM_SRCS}")

CMake docs on variables

How to access the SMS storage on Android?

You are going to need to call the SmsManager class. You are probably going to need to use the STATUS_ON_ICC_READ constant and maybe put what you get there into your apps local db so that you can keep track of what you have already read vs the new stuff for your app to parse through. BUT bear in mind that you have to declare the use of the class in your manifest, so users will see that you have access to their SMS called out in the permissions dialogue they get when they install. Seeing SMS access is unusual and could put some users off. Good luck.

Here is the link that goes into depth on the Sms Manager

How to find out which package version is loaded in R?

To check the version of R execute : R --version

Or after you are in the R shell print the contents of version$version.string


To check the version of installed packages do the following.

After loading the library, you can execute sessionInfo ()

But to know the list of all installed packages:

packinfo <- installed.packages(fields = c("Package", "Version"))
packinfo[,c("Package", "Version")]

OR to extract a specific library version, once you have extracted the information using the installed.package function as above just use the name of the package in the first dimension of the matrix.

packinfo["RANN",c("Package", "Version")]
packinfo["graphics",c("Package", "Version")]

The above will print the versions of the RANN library and the graphics library.

How to detect tableView cell touched or clicked in swift

I screw up on the every time! Just make sure the tableView delegate and dataSource are declared in viewDidLoad. Then I normally populate a few arrays to simulate returned data and then take it from there!

//******** Populate Table with data ***********
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{

    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as? SetupCellView
    cell?.ControllerLbl.text = ViewContHeading[indexPath.row]
    cell?.DetailLbl.text = ViewContDetail[indexPath.row]
    cell?.StartupImageImg.image = UIImage(named: ViewContImages[indexPath.row])
    return cell!

How to clear a textbox using javascript

just set empty string

    <input type="text" id="textId" value="A new value">
    document.getElementById('textId').value = '';

How to create a simple http proxy in node.js?

Super simple and readable, here's how you create a local proxy server to a local HTTP server with just Node.js (tested on v8.1.0). I've found it particular useful for integration testing so here's my share:

 * Once this is running open your browser and hit http://localhost
 * You'll see that the request hits the proxy and you get the HTML back

'use strict';

const net = require('net');
const http = require('http');

const PROXY_PORT = 80;
const HTTP_SERVER_PORT = 8080;

let proxy = net.createServer(socket => {
    socket.on('data', message => {
        console.log('---PROXY- got message', message.toString());

        let serviceSocket = new net.Socket();

        serviceSocket.connect(HTTP_SERVER_PORT, 'localhost', () => {
            console.log('---PROXY- Sending message to server');

        serviceSocket.on('data', data => {
            console.log('---PROXY- Receiving message from server', data.toString();

let httpServer = http.createServer((req, res) => {
    switch (req.url) {
        case '/':
            res.writeHead(200, {'Content-Type': 'text/html'});
            res.writeHead(404, {'Content-Type': 'text/plain'});
            res.end('404 Not Found');


What is the { get; set; } syntax in C#?

A property is a like a layer that separates the private variable from other members of a class. From outside world it feels like a property is just a field, a property can be accessed using .Property

public class Person
    public string FirstName { get; set; }

    public string LastName { get; set; }

    public string FullName => $"{FirstName} {LastName}";

public class Person
    public string FirstName { get; set; }

    public string LastName { get; set; }

    public string FullName { get { return $"{FirstName} {LastName}"; } }

FullName is a Property. The one with arrow is a shortcut. From outside world, we can access FullName like this:

var person = new Person();

Callers do not care about how you implemented the FullName. But inside the class you can change FullName whatever you want.

Check out Microsoft Documentation for more detailed explanation:

How to add hyperlink in JLabel?

Use a JEditorPane with a HyperlinkListener.

ipynb import another ipynb file

Install ipynb from your command prompt

pip install import-ipynb

Import in your notebook file

import import_ipynb

Now use regular import command to import your file

import MyOtherNotebook

Dump all documents of Elasticsearch

The data itself is one or more lucene indices, since you can have multiple shards. What you also need to backup is the cluster state, which contains all sorts of information regarding the cluster, the available indices, their mappings, the shards they are composed of etc.

It's all within the data directory though, you can just copy it. Its structure is pretty intuitive. Right before copying it's better to disable automatic flush (in order to backup a consistent view of the index and avoiding writes on it while copying files), issue a manual flush, disable allocation as well. Remember to copy the directory from all nodes.

Also, next major version of elasticsearch is going to provide a new snapshot/restore api that will allow you to perform incremental snapshots and restore them too via api. Here is the related github issue:

Android Call an method from another class

Add this in MainActivity.

Intent intent = new Intent(getApplicationContext(), Heightimage.class);

Servlet Mapping using web.xml

It allows servlets to have multiple servlet mappings:


It allows filters to be mapped on the particular servlet:


Your proposal would support neither of them. Note that the web.xml is read and parsed only once during application's startup, not on every HTTP request as you seem to think.

Since Servlet 3.0, there's the @WebServlet annotation which minimizes this boilerplate:

public class Servlet1 extends HttpServlet {

See also:

How to change visibility of layout programmatically

this is a programatical approach:

 view.setVisibility(View.GONE); //For GONE
 view.setVisibility(View.INVISIBLE); //For INVISIBLE
 view.setVisibility(View.VISIBLE); //For VISIBLE

Should composer.lock be committed to version control?

After doing it both ways for a few projects my stance is that composer.lock should not be committed as part of the project.

composer.lock is build metadata which is not part of the project. The state of dependencies should be controlled through how you're versioning them (either manually or as part of your automated build process) and not arbitrarily by the last developer to update them and commit the lock file.

If you are concerned about your dependencies changing between composer updates then you have a lack of confidence in your versioning scheme. Versions (1.0, 1.1, 1.2, etc) should be immutable and you should avoid "dev-" and "X.*" wildcards outside of initial feature development.

Committing the lock file is a regression for your dependency management system as the dependency version has now gone back to being implicitly defined.

Also, your project should never have to be rebuilt or have its dependencies reacquired in each environment, especially prod. Your deliverable (tar, zip, phar, a directory, etc) should be immutable and promoted through environments without changing.

Paging UICollectionView by cells, not screen

Also you can create fake scroll view to handle scrolling.

Horizontal or Vertical

// === Defaults ===
let bannerSize = CGSize(width: 280, height: 170)
let pageWidth: CGFloat = 290 // ^ + paging
let insetLeft: CGFloat = 20
let insetRight: CGFloat = 20
// ================

var pageScrollView: UIScrollView!

override func viewDidLoad() {

    // Create fake scrollview to properly handle paging
    pageScrollView = UIScrollView(frame: CGRect(origin: .zero, size: CGSize(width: pageWidth, height: 100)))
    pageScrollView.isPagingEnabled = true
    pageScrollView.alwaysBounceHorizontal = true
    pageScrollView.showsVerticalScrollIndicator = false
    pageScrollView.showsHorizontalScrollIndicator = false
    pageScrollView.delegate = self
    pageScrollView.isHidden = true
    view.insertSubview(pageScrollView, belowSubview: collectionView)

    // Set desired gesture recognizers to the collection view
    for gr in pageScrollView.gestureRecognizers! {

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView == pageScrollView {
        // Return scrolling back to the collection view
        collectionView.contentOffset.x = pageScrollView.contentOffset.x

func refreshData() {


override func viewDidLayoutSubviews() {


/// Refresh fake scrolling view content size if content changes
func refreshScroll() {
    let w = collectionView.width - bannerSize.width - insetLeft - insetRight
    pageScrollView.contentSize = CGSize(width: pageWidth * CGFloat(banners.count) - w, height: 100)

How do I update the element at a certain position in an ArrayList?

 import java.util.ArrayList;
 import java.util.Iterator;

 public class javaClass {

public static void main(String args[]) {

    ArrayList<String> alstr = new ArrayList<>();

    for(String str : alstr) {
    // update value here
    alstr.set(3, "Ramveer");
    System.out.println("with Iterator");
    Iterator<String>  itr = alstr.iterator();

    while (itr.hasNext()) {
        Object obj =;


How to extract closed caption transcript from YouTube video?

You can download the streaming subtitles from YouTube with KeepSubs DownSub and SaveSubs.

You can choose from the Automatic Transcript or author supplied close captions. It also offers the possibility to automatically translate the English subtitles into other languages using Google Translate.

When to use RSpec let()?

Note to Joseph -- if you are creating database objects in a before(:all) they won't be captured in a transaction and you're much more likely to leave cruft in your test database. Use before(:each) instead.

The other reason to use let and its lazy evaluation is so you can take a complicated object and test individual pieces by overriding lets in contexts, as in this very contrived example:

context "foo" do
  let(:params) do
     { :foo => foo,  :bar => "bar" }
  let(:foo) { "foo" }
  it "is set to foo" do
    params[:foo].should eq("foo")
  context "when foo is bar" do
    let(:foo) { "bar" }
    # NOTE we didn't have to redefine params entirely!
    it "is set to bar" do
      params[:foo].should eq("bar")

jQuery datepicker set selected date, on the fly

$('.date-pick').datePicker().val(new Date()).trigger('change')

finally, that what i look for the last few hours! I need initiate changes, not just setup date in text field!

Mercurial — revert back to old version and continue from there

After using hg update -r REV it wasn't clear in the answer about how to commit that change so that you can then push.

If you just try to commit after the update, Mercurial doesn't think there are any changes.

I had to first make a change to any file (say in a README) so Mercurial recognized that I made a new change, then I could commit that.

This then created two heads as mentioned.

To get rid of the other head before pushing, I then followed the No-Op Merges step to remedy that situation.

I was then able to push.

selecting rows with id from another table

SELECT terms.*
FROM terms JOIN terms_relation ON id=term_id
WHERE taxonomy='categ'

qmake: could not find a Qt installation of ''

I have qt4 installed. I found that using the following path worked for me, despite 'which qmake' returning /usr/bin/qmake, which is just a link to qtchooser anyway.

The following path works for me, on a 64 bit system. Running from the full path of:


Convert JavaScript String to be all lower case?

Just an examples for toLowerCase(), toUpperCase() and prototype for not yet available toTitleCase() or toPropperCase()

String.prototype.toTitleCase = function() {_x000D_
  return this.split(' ').map(i => i[0].toUpperCase() + i.substring(1).toLowerCase()).join(' ');_x000D_
String.prototype.toPropperCase = function() {_x000D_
  return this.toTitleCase();_x000D_
var OriginalCase = 'Your Name';_x000D_
var lowercase = OriginalCase.toLowerCase();_x000D_
var upperCase = lowercase.toUpperCase();_x000D_
var titleCase = upperCase.toTitleCase();_x000D_
console.log('Original: ' + OriginalCase);_x000D_
console.log('toLowerCase(): ' + lowercase);_x000D_
console.log('toUpperCase(): ' + upperCase);_x000D_
console.log('toTitleCase(): ' + titleCase);

edited 2018

TypeError: 'str' does not support the buffer interface

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

bytes("my data", "encoding")

For example:

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

The object returned will work with outfile.write.

How to configure multi-module Maven + Sonar + JaCoCo to give merged coverage report?

You can call a ant task called merge on maven, to put all coverage files (*.exec) together in the same file.

If you are run unit tests use the phase prepare-package, if you run integration test so use post-integration-test.

This site has an example to how call jacoco ant task in maven project

You can use this merged file on sonar.

How to load property file from classpath?

final Properties properties = new Properties();
try (final InputStream stream =
           this.getClass().getResourceAsStream("")) {
    /* or properties.loadFromXML(...) */

How to get just the parent directory name of a specific file

If you have just String path and don't want to create new File object you can use something like:

public static String getParentDirPath(String fileOrDirPath) {
    boolean endsWithSlash = fileOrDirPath.endsWith(File.separator);
    return fileOrDirPath.substring(0, fileOrDirPath.lastIndexOf(File.separatorChar, 
            endsWithSlash ? fileOrDirPath.length() - 2 : fileOrDirPath.length() - 1));

Delete files in subfolder using batch script

You can use the /s switch for del to delete in subfolders as well.


del D:\test\*.* /s

Would delete all files under test including all files in all subfolders.

To remove folders use rd, same switch applies.

rd D:\test\folder /s /q

rd doesn't support wildcards * though so if you want to recursively delete all subfolders under the test directory you can use a for loop.

for /r /d D:\test %a in (*) do rd %a /s /q

If you are using the for option in a batch file remember to use 2 %'s instead of 1.

Get the client's IP address in

If you use an other server as reverse proxy all of the mentioned fields will contain localhost. The easiest workaround is to add headers for ip/port in the proxy server.

Example for nginx: add this after your proxy_pass:

proxy_set_header  X-Real-IP $remote_addr;
proxy_set_header  X-Real-Port $remote_port;

This will make the headers available in the node server:

var ip = socket.handshake.headers["x-real-ip"];
var port = socket.handshake.headers["x-real-port"];

Note that the header is internally converted to lower case.

If you are connecting the node server directly to the client,

var ip = socket.conn.remoteAddress;

works with version 1.4.6 for me.

Android custom dropdown/popup menu

First, create a folder named “menu” in the “res” folder.

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



Then, create your Activity Class:

public class PopupMenu1 extends Activity {
    protected void onCreate(Bundle savedInstanceState) {

    public void onPopupButtonClick(View button) {
        PopupMenu popup = new PopupMenu(this, button);
        popup.getMenuInflater().inflate(, popup.getMenu());

        popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
            public boolean onMenuItemClick(MenuItem item) {
                        "Clicked popup menu item " + item.getTitle(),
                return true;

How to delete duplicates on a MySQL table?

delete p from 
product p
inner join (
    select max(id) as id, url from product 
    group by url 
    having count(*) > 1
) unik on unik.url = p.url and !=;

Creating a search form in PHP to search a database?

Are you sure, that specified database and table exists? Did you try to look at your database using any database client? For example command-line MySQL client bundled with MySQL server. Or if you a developer newbie, there are dozens of a GUI and web interface clients (HeidiSQL, MySQL Workbench, phpMyAdmin and many more). So first check, if your table creation script was successful and had created what it have to.

BTW why do you have a script for creating the database structure? It's usualy a nonrecurring operation, so write the script to do this is unneeded. It's useful only in case of need of repeatedly creating and manipulating the database structure on the fly.

Is there a way to set background-image as a base64 encoded image?

Had the same problem with base64. For anyone in the future with the same problem:

url = "data:image/png;base64,iVBORw0KGgoAAAAAAAAyCAYAAAAUYybjAAAgAElE...";

This would work executed from console, but not from within a script:

$img.css("background-image", "url('" + url + "')");

But after playing with it a bit, I came up with this:

var img = new Image();
img.src = url;
$img.css("background-image", "url('" + img.src + "')");

No idea why it works with a proxy image, but it does. Tested on Firefox Dev 37 and Chrome 40.

Hope it helps someone.


Investigated a little bit further. It appears that sometimes base64 encoding (at least in my case) breaks with CSS because of line breaks present in the encoded value (in my case value was generated dynamically by ActionScript).

Simply using e.g.:

$img.css("background-image", "url('" + url.replace(/(\r\n|\n|\r)/gm, "") + "')");

works too, and even seems to be faster by a few ms than using a proxy image.

How to comment in Vim's config files: ".vimrc"?

Same as above. Use double quote to start the comment and without the closing quote.


set cul "Highlight current line

Angular and Typescript: Can't find names - Error: cannot find name

I had the same problem and I solved it using the lib option in tsconfig.json. As said by basarat in his answer, a .d.ts file is implicitly included by TypeScript depending on the compile targetoption but this behaviour can be changed with the lib option.

You can specify additional definition files to be included without changing the targeted JS version. For examples this is part of my current compilerOptions for [email protected] and it adds support for es2015 features without installing anything else:

"compilerOptions": {
    "experimentalDecorators": true,
    "lib": ["es5", "dom", "es6", "dom.iterable", "scripthost"],
    "module": "commonjs",
    "moduleResolution": "node",
    "noLib": false,
    "target": "es5",
    "types": ["node"]

For the complete list of available options check the official doc.

Note also that I added "types": ["node"] and installed npm install @types/node to support require('some-module') in my code.

Killing a process created with Python's subprocess.Popen()

In your code it should be


Both kill or terminate are methods of the Popen object which sends the signal signal.SIGKILL to the process.

How to do joins in LINQ on multiple fields in single join

Using the join operator you can only perform equijoins. Other types of joins can be constructed using other operators. I'm not sure whether the exact join you are trying to do would be easier using these methods or by changing the where clause. Documentation on the join clause can be found here. MSDN has an article on join operations with multiple links to examples of other joins, as well.

How to make in CSS an overlay over an image?

You can achieve this with this simple CSS/HTML:

.image-container {
    position: relative;
    width: 200px;
    height: 300px;
.image-container .after {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: none;
    color: #FFF;
.image-container:hover .after {
    display: block;
    background: rgba(0, 0, 0, .6);


<div class="image-container">
    <img src="" />
    <div class="after">This is some content</div>


UPD: Here is one nice final demo with some extra stylings.

.image-container {_x000D_
    position: relative;_x000D_
    display: inline-block;_x000D_
.image-container img {display: block;}_x000D_
.image-container .after {_x000D_
    position: absolute;_x000D_
    top: 0;_x000D_
    left: 0;_x000D_
    width: 100%;_x000D_
    height: 100%;_x000D_
    display: none;_x000D_
    color: #FFF;_x000D_
.image-container:hover .after {_x000D_
    display: block;_x000D_
    background: rgba(0, 0, 0, .6);_x000D_
.image-container .after .content {_x000D_
    position: absolute;_x000D_
    bottom: 0;_x000D_
    font-family: Arial;_x000D_
    text-align: center;_x000D_
    width: 100%;_x000D_
    box-sizing: border-box;_x000D_
    padding: 5px;_x000D_
.image-container .after .zoom {_x000D_
    color: #DDD;_x000D_
    font-size: 48px;_x000D_
    position: absolute;_x000D_
    top: 50%;_x000D_
    left: 50%;_x000D_
    margin: -30px 0 0 -19px;_x000D_
    height: 50px;_x000D_
    width: 45px;_x000D_
    cursor: pointer;_x000D_
.image-container .after .zoom:hover {_x000D_
    color: #FFF;_x000D_
<link href="//" rel="stylesheet"/>_x000D_
<div class="image-container">_x000D_
    <img src="" />_x000D_
    <div class="after">_x000D_
        <span class="content">This is some content. It can be long and span several lines.</span>_x000D_
        <span class="zoom">_x000D_
            <i class="fa fa-search"></i>_x000D_

A simple command line to download a remote maven2 artifact to the local repository?

Give them a trivial pom with these jars listed as dependencies and instructions to run:

mvn dependency:go-offline

This will pull the dependencies to the local repo.

A more direct solution is dependency:get, but it's a lot of arguments to type:

mvn dependency:get -DrepoUrl=something -Dartifact=group:artifact:version

Writing to CSV with Python adds blank lines

You need to open the file in binary b mode to take care of blank lines in Python 2. This isn't required in Python 3.

So, change open('test.csv', 'w') to open('test.csv', 'wb').

Codeigniter $this->input->post() empty while $_POST is working correctly

You are missing the parent constructor. When your controller is loaded you must Call the parent CI_Controller class constructor in your controller constructor

What is the difference between window, screen, and document in Javascript?

Window is the main JavaScript object root, aka the global object in a browser, also can be treated as the root of the document object model. You can access it as window

window.screen or just screen is a small information object about physical screen dimensions.

window.document or just document is the main object of the potentially visible (or better yet: rendered) document object model/DOM.

Since window is the global object you can reference any properties of it with just the property name - so you do not have to write down window. - it will be figured out by the runtime.

g++ ld: symbol(s) not found for architecture x86_64

I had a similar warning/error/failure when I was simply trying to make an executable from two different object files (main.o and add.o). I was using the command:

gcc -o exec main.o add.o

But my program is a C++ program. Using the g++ compiler solved my issue:

g++ -o exec main.o add.o

I was always under the impression that gcc could figure these things out on its own. Apparently not. I hope this helps someone else searching for this error.

Commands out of sync; you can't run this command now

I solved this problem in my C application - here's how I did it:

  1. Quoting from mysql forums:

    This error results when you terminate your query with a semicolon delimiter inside the application. While it is required to terminate a query with a semicolon delimiter when executing it from the command line or in the query browser, remove the delimiter from the query inside your application.

  2. After running my query and dealing with the results [C API: mysql_store_result()], I iterate over any further potentially pending results that occurs via multiple SQL statement execution such as two or more select statements (back to back without dealing with the results).

    The fact is that my procedures don't return multiple results but the database doesn't know that until I execute: [C API: mysql_next_result()]. I do this in a loop (for good measure) until it returns non-zero. That's when the current connection handler knows it's okay to execute another query (I cache my handlers to minimize connection overhead).

    This is the loop I use:

    for(; mysql_next_result(mysql_handler) == 0;) 
      /* do nothing */;

I don't know PHP but I'm sure it has something similar.

Android Emulator: Installation error: INSTALL_FAILED_VERSION_DOWNGRADE

You can also consider adding -d flag to adb install. It should ignore this error.

adb install -r -d abc.apk

Why is vertical-align: middle not working on my span or div?

In case you cannot rely on flexbox... Place .child into .parent's center. Works when pixel sizes are unknown (in other words, always) and no problems with IE9+ too.

.parent { position: relative; }_x000D_
.child {_x000D_
    position: absolute;_x000D_
    top : 50%;_x000D_
    left: 50%;_x000D_
    -ms-transform: translate(-50%, -50%);_x000D_
    transform    : translate(-50%, -50%);    _x000D_
<div class="parent" style="background:lightyellow; padding:6em"> _x000D_
  <div class="child" style="background:gold; padding:1em">&mdash;</div> _x000D_

How do I create an Excel (.XLS and .XLSX) file in C# without installing Microsoft Office?

I've used with success the following open source projects:

  • ExcelPackage for OOXML formats (Office 2007)

  • NPOI for .XLS format (Office 2003). NPOI 2.0 (Beta) also supports XLSX.

Take a look at my blog posts:

Creating Excel spreadsheets .XLS and .XLSX in C#

NPOI with Excel Table and dynamic Chart

What is the purpose of "&&" in a shell command?

command-line - what is the purpose of &&?

In shell, when you see

$ command one && command two

the intent is to execute the command that follows the && only if the first command is successful. This is idiomatic of Posix shells, and not only found in Bash.

It intends to prevent the running of the second process if the first fails.

You may notice I've used the word "intent" - that's for good reason. Not all programs have the same behavior, so for this to work, you need to understand what the program considers a "failure" and how it handles it by reading the documentation and, if necessary, the source code.

Your shell considers a return value of 0 for true, other positive numbers for false

Programs return a signal on exiting. They should return 0 if they exit successfully, or greater than zero if they do not. This allows a limited amount of communication between processes.

The && is referred to as AND_IF in the posix shell grammar, which is part of an and_or list of commands, which also include the || which is an OR_IF with similar semantics.

Grammar symbols, quoted from the documentation:

%token  AND_IF    OR_IF    DSEMI
/*      '&&'      '||'     ';;'    */

And the Grammar (also quoted from the documentation), which shows that any number of AND_IFs (&&) and/or OR_IFs (||) can be be strung together (as and_or is defined recursively):

and_or           :                         pipeline
                 | and_or AND_IF linebreak pipeline
                 | and_or OR_IF  linebreak pipeline

Both operators have equal precedence and are evaluated left to right (they are left associative). As the docs say:

An AND-OR list is a sequence of one or more pipelines separated by the operators "&&" and "||" .

A list is a sequence of one or more AND-OR lists separated by the operators ';' and '&' and optionally terminated by ';', '&', or .

The operators "&&" and "||" shall have equal precedence and shall be evaluated with left associativity. For example, both of the following commands write solely bar to standard output:

$ false && echo foo || echo bar
$ true || echo foo && echo bar
  1. In the first case, the false is a command that exits with the status of 1

    $ false
    $ echo $?

    which means echo foo does not run (i.e., shortcircuiting echo foo). Then the command echo bar is executed.

  2. In the second case, true exits with a code of 0

    $ true
    $ echo $?

    and therefore echo foo is not executed, then echo bar is executed.

Only get hash value using md5sum (without filename)

md5="$(md5sum "${my_iso_file}")"
md5="${md5%% *}" # remove the first space and everything after it
echo "${md5}"

What is the "continue" keyword and how does it work in Java?

If you think of the body of a loop as a subroutine, continue is sort of like return. The same keyword exists in C, and serves the same purpose. Here's a contrived example:

for(int i=0; i < 10; ++i) {
  if (i % 2 == 0) {

This will print out only the odd numbers.

How to emulate a do-while loop in Python?

Quick hack:

def dowhile(func = None, condition = None):
    if not func or not condition:
        while condition():

Use like so:

>>> x = 10
>>> def f():
...     global x
...     x = x - 1
>>> def c():
        global x
        return x > 0
>>> dowhile(f, c)
>>> print x