Programs & Examples On #Resource ref

What is resource-ref in web.xml used for?

You can always refer to resources in your application directly by their JNDI name as configured in the container, but if you do so, essentially you are wiring the container-specific name into your code. This has some disadvantages, for example, if you'll ever want to change the name later for some reason, you'll need to update all the references in all your applications, and then rebuild and redeploy them.

<resource-ref> introduces another layer of indirection: you specify the name you want to use in the web.xml, and, depending on the container, provide a binding in a container-specific configuration file.

So here's what happens: let's say you want to lookup the java:comp/env/jdbc/primaryDB name. The container finds that web.xml has a <resource-ref> element for jdbc/primaryDB, so it will look into the container-specific configuration, that contains something similar to the following:


Finally, it returns the object registered under the name of jdbc/PrimaryDBInTheContainer.

The idea is that specifying resources in the web.xml has the advantage of separating the developer role from the deployer role. In other words, as a developer, you don't have to know what your required resources are actually called in production, and as the guy deploying the application, you will have a nice list of names to map to real resources.

Mongoose, Select a specific field with find

I found a really good option in mongoose that uses distinct returns array all of a specific field in document.

User.find({}).distinct('email').then((err, emails) => { // do something })

How to Customize a Progress Bar In Android

For using custom drawable:

<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android=""
android:pivotY="50%" />

(add under res/drawable progress.xml). my_drawable may be xml, png

Then in your layout use


Hidden property of a button in HTML

It also works without jQuery if you do the following changes:

  1. Add type="button" to the edit button in order not to trigger submission of the form.

  2. Change the name of your function from change() to anything else.

  3. Don't use hidden="hidden", use CSS instead: style="display: none;".

The following code works for me:

<html xmlns="">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link rel="STYLESHEET" type="text/css" href="dba_style/buttons.css" />
<title>Untitled Document</title>
<script type="text/javascript">
function do_change(){
document.getElementById("save").style.display = "block";
document.getElementById("change").style.display = "block";
document.getElementById("cancel").style.display = "block";
<form name="form1" method="post" action="">
<div class="buttons">

<button type="button" class="regular" name="edit" id="edit" onclick="do_change(); return false;">
    <img src="dba_images/textfield_key.png" alt=""/>

<button type="submit" class="positive" name="save" id="save" style="display:none;">
    <img src="dba_images/apply2.png" alt=""/>

<button class="regular" name="change" id="change" style="display:none;">
    <img src="dba_images/textfield_key.png" alt=""/>

    <button class="negative" name="cancel" id="cancel" style="display:none;">
        <img src="dba_images/cross.png" alt=""/>

Execute PHP scripts within Node.js web server

You can run PHP as with any web-server, using the SPHP module for node.
It's compatible but not dependent on express.
It also supports websockets requests on the HTTP port.
Its biased for speed under small load, rather then saving resources.

To install in node:

npm install sphp

in you app:

var express = require('express');
var sphp = require('sphp');

var app = express();
var server = app.listen(8080);


For more information, look at

I'm slightly biased too because I'm the author :)

Java Code for calculating Leap Year

Your code, as it is, without an additional class, does not appear to work for universal java. Here is a simplified version that works anywhere, leaning more towards your code.

import java.util.*;
public class LeapYear {
    public static void main(String[] args) {
        int year;
            Scanner scan = new Scanner(;
            System.out.println("Enter year: ");
            year = scan.nextInt();

            if ((year % 4 == 0) && year % 100 != 0) {
                System.out.println(year + " is a leap year.");
            } else if ((year % 4 == 0) && (year % 100 == 0)
                    && (year % 400 == 0)) {
                System.out.println(year + " is a leap year.");
            } else {
                System.out.println(year + " is not a leap year.");

Your code, in context, works just as well, but note that book code always works, and is tested thoroughly. Not to say yours isn't. :)

Align button at the bottom of div using CSS

Goes to the right and can be used the same way for the left

   float: right;
   bottom: 0;

Mean filter for smoothing images in Matlab

and the convolution is defined through a multiplication in transform domain:

conv2(x,y) = fftshift(ifft2(fft2(x).*fft2(y)))

if one channel is considered... for more channels this has to be done every channel

cursor.fetchall() vs list(cursor) in Python

You could use list comprehensions to bring the item in your tuple into a list:

conn = mysql.connector.connect()
cursor = conn.cursor()
sql = "SELECT column_name FROM db.table_name;"

results = cursor.fetchall()
# bring the first item of the tuple in your results here
item_0_in_result = [_[0] for _ in results]

How to create a bash script to check the SSH connection?

To connect to a server with multiple interfaces

ssh -o ConnectTimeout=1 -q [email protected];[ $? = 1 ] || ssh -o ConnectTimeout=1 -q [email protected]

How to access a dictionary key value present inside a list?

First of all don't use 'list' as variable name.

If you have simple dictionaries with unique keys then you can do the following(note that new dictionary object with all items from sub-dictionaries will be created):

res  = {}
for line in listOfDicts:
>>> 4


getValues = lambda key,inputData: [subVal[key] for subVal in inputData if key in subVal]
getValues('d', listOfDicts)
>>> [4]

Or very base:

def get_value(listOfDicts, key):
    for subVal in listOfDicts:
        if key in subVal:
            return subVal[key]

Using python's eval() vs. ast.literal_eval()?

ast.literal_eval() only considers a small subset of Python's syntax to be valid:

The string or node provided may only consist of the following Python literal structures: strings, bytes, numbers, tuples, lists, dicts, sets, booleans, and None.

Passing __import__('os').system('rm -rf /a-path-you-really-care-about') into ast.literal_eval() will raise an error, but eval() will happily delete your files.

Since it looks like you're only letting the user input a plain dictionary, use ast.literal_eval(). It safely does what you want and nothing more.

Why Maven uses JDK 1.6 but my java -version is 1.7

You can also explicitly tell maven which java version to compile for. You can try adding the maven-compiler-plugin to your pom.


If you imported a maven project into an IDE, then there is probably a maven setting in your IDE for default compiler that your maven runner is using.

What is the suggested way to install brew, node.js, io.js, nvm, npm on OS X?

If you have previously installed node using brew, then you will have a bunch of extra files that you should clean up before installing node "the right way". Plus, I had to add a few settings to my startup script to make things work smoothly.

I wrote a script to make this easy.

# filename:  install-nvm-npm-node
# author:    Lex Sheehan
# purpose:   To cleanly install NVM, NODE and NPM
# dependencies:  brew

NOW=$(date +%x\ %H:%M:%S)
REV=$(tput rev)
OFF=$(tput sgr0)
MY_NAME=$(basename $0)
if [ "$NODE_VER_TO_INSTALL" == "" ]; then
if [ "`echo "$NODE_VER_TO_INSTALL" | cut -c1-1`" != "v" ]; then
    echo """$CR""Usage:   $ $MY_NAME <NODE_VERSION_TO_INSALL>"
    echo "Example: $ $MY_NAME v0.12.1"
    echo "Example: $ $MY_NAME $CR"
    exit 1
echo """$CR""First, run:  $ brew update"
echo "Likely, you'll need to do what it suggests."
echo "Likely, you'll need to run: $ brew update$CR"
echo "To install latest node version, run the following command to get the latest version:  $ nvm ls-remote"
echo "... and pass the version number you want as the only param to $MY_NAME. $CR"
echo "Are you ready to install the latest version of nvm and npm and node version $NODE_VER_TO_INSTALL ?$CR"
echo "Press CTL+C to exit --or-- Enter to continue..."
read x

echo """$REV""Uninstalling nvm...$CR$OFF"
# Making backups, but in all likelyhood you'll just reinstall them (and won't need these backups)
if [ ! -d "$BACKUP_DIR" ]; then 
    echo "Creating directory to store $HOME/.nvm .npm and .bower cache backups: $BACKUP_DIR"
    mkdir -p $BACKUP_DIR
set -x
mv $HOME/.nvm   $BACKUP_DIR  2>/dev/null
mv $HOME/.npm   $BACKUP_DIR  2>/dev/null
mv $HOME/.bower $BACKUP_DIR  2>/dev/null
{ set +x; } &>/dev/null

echo "$REV""$CR""Uninstalling node...$CR$OFF"
echo "Enter your password to remove user some node-related /usr/local directories"
set -x
sudo rm -rf /usr/local/lib/node_modules
rm -rf /usr/local/lib/node
rm -rf /usr/local/include/node
rm -rf /usr/local/include/node_modules
rm /usr/local/bin/npm
rm /usr/local/lib/dtrace/node.d
rm -rf $HOME/.node
rm -rf $HOME/.node-gyp
rm /opt/local/bin/node
rm /opt/local/include/node
rm -rf /opt/local/lib/node_modules
rm -rf /usr/local/Cellar/nvm
brew uninstall node 2>/dev/null
{ set +x; } &>/dev/null

echo "$REV""$CR""Installing nvm...$CR$OFF"

echo "++brew install nvm"
brew install nvm 
echo '$(brew --prefix nvm)/'
source $(brew --prefix nvm)/

echo "$REV""$CR""Insert the following line in your startup script (ex: $HOME/.bashrc):$CR$OFF"
echo "export NVM_DIR=\"\$(brew --prefix nvm)\"; [ -s \"\$NVM_DIR/\" ] && . \"\$NVM_DIR/\"$CR"
NVM_DIR="$(brew --prefix nvm)"

echo """$CR""Using nvm install node...$CR"
echo "++ nvm install $NODE_VER_TO_INSTALL"
nvm install $NODE_VER_TO_INSTALL
NODE_BINARY_PATH="`find /usr/local/Cellar/nvm -name node -type d|head -n 1`/$NODE_VER_TO_INSTALL/bin"
echo "$REV""$CR""Insert the following line in your startup script (ex: $HOME/.bashrc) and then restart your shell:$CR$OFF"
echo "export PATH=\$PATH:$NODE_BINARY_PATH:$HOME/.node/bin"

echo """$CR""Upgrading npm...$CR"
echo '++ install -g npm@latest'
npm install -g npm@latest
{ set +x; } &>/dev/null
echo "$REV""$CR""Insert following line in your $HOME/.npmrc file:$OFF"
echo """$CR""prefix=$HOME/.node$CR"
echo "Now, all is likley well if you can run the following without errors:  npm install -g grunt-cli$CR"
echo "Other recommended global installs: bower, gulp, yo, node-inspector$CR"

I wrote a short article here that details why this is "the right way".

If you need to install iojs, do so using nvm like this:

nvm install iojs-v1.7.1

To install brew, just see its home page.

See alexpods answer for the rest.

isset() and empty() - what to use

In your particular case: if ($var).

You need to use isset if you don't know whether the variable exists or not. Since you declared it on the very first line though, you know it exists, hence you don't need to, nay, should not use isset.

The same goes for empty, only that empty also combines a check for the truthiness of the value. empty is equivalent to !isset($var) || !$var and !empty is equivalent to isset($var) && $var, or isset($var) && $var == true.

If you only want to test a variable that should exist for truthiness, if ($var) is perfectly adequate and to the point.

What is an attribute in Java?

An abstract class is a type of class that can only be used as a base class for another class; such thus cannot be instantiated. To make a class abstract, the keyword abstract is used. Abstract classes may have one or more abstract methods that only have a header line (no method body). The method header line ends with a semicolon (;). Any class that is derived from the base class can define the method body in a way that is consistent with the header line using all the designated parameters and returning the correct data type (if the return type is not void). An abstract method acts as a place holder; all derived classes are expected to override and complete the method.

Example in Java

abstract public class Shape


double area;

public abstract double getArea();


What does yield mean in PHP?

This function is using yield:

function a($items) {
    foreach ($items as $item) {
        yield $item + 1;

It is almost the same as this one without:

function b($items) {
    $result = [];
    foreach ($items as $item) {
        $result[] = $item + 1;
    return $result;

The only one difference is that a() returns a generator and b() just a simple array. You can iterate on both.

Also, the first one does not allocate a full array and is therefore less memory-demanding.

Gradle's dependency cache may be corrupt (this sometimes occurs after a network connection timeout.)

You can try this

  1. first Open your Android Studio > open any project you're doing
  2. click on File > Settings > Build,Execution,Deployment > Gradle
  3. At Project-Level settings , there are 2 option to sync the gradle either usin the default or local.
  4. now change from default to a local gradle distribution > gradle Home

  5. select the path on your computer.

C:\Program Files\Android\Android Studio\gradle\gradle-4.1

  1. click on OK

  2. Now build starts again it should be solved.

Configuration with name 'default' not found. Android Studio

I also faced the same problem and the problem was that the libraries were missing in some of the following files.

settings.gradle, app/build.gradle, package.json,

Suppose the library is react-native-vector-icons then it should be mentioned in following files;

In app/build.gradle file under dependencies section add:

compile project(':react-native-vector-icons')

In settings.gradle file under android folder, add the following:

include ':react-native-vector-icons' project(':react-native-vector-icons').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-vector-icons/android')

In, add the following:

Import the dependency: import com.oblador.vectoricons.VectorIconsPackage;

and then add: new VectorIconsPackage() in getPackages() method.

How to increment a variable on a for loop in jinja template?

As Jeroen says there are scoping issues: if you set 'count' outside the loop, you can't modify it inside the loop.

You can defeat this behavior by using an object rather than a scalar for 'count':

{% set count = [1] %}

You can now manipulate count inside a forloop or even an %include%. Here's how I increment count (yes, it's kludgy but oh well):

{% if count.append(count.pop() + 1) %}{% endif %} {# increment count by 1 #}

Android Gradle 5.0 Update:Cause: org.jetbrains.plugins.gradle.tooling.util

For others who have the same problem in IntelliJ:

upgrading to the latest IDE version should resolve the issue.

In my case going from 2018.1 -> 2018.3.3

How to enable support of CPU virtualization on Macbook Pro?

CPU Virtualization is enabled by default on all MacBooks with compatible CPUs (i7 is compatible). You can try to reset PRAM if you think it was disabled somehow, but I doubt it.

I think the issue might be in the old version of OS. If your MacBook is i7, then you better upgrade OS to something newer.

How to return dictionary keys as a list in Python?

I can think of 2 ways in which we can extract the keys from the dictionary.

Method 1: - To get the keys using .keys() method and then convert it to list.

some_dict = {1: 'one', 2: 'two', 3: 'three'}
list_of_keys = list(some_dict.keys())

Method 2: - To create an empty list and then append keys to the list via a loop. You can get the values with this loop as well (use .keys() for just keys and .items() for both keys and values extraction)

list_of_keys = []
list_of_values = []
for key,val in some_dict.items():



How to dismiss notification after action has been clicked

When you called notify on the notification manager you gave it an id - that is the unique id you can use to access it later (this is from the notification manager:

notify(int id, Notification notification)

To cancel, you would call:

cancel(int id)

with the same id. So, basically, you need to keep track of the id or possibly put the id into a Bundle you add to the Intent inside the PendingIntent?

How do I edit an incorrect commit message in git ( that I've pushed )?

Suppose you have a tree like this:

dd2e86 - 946992 - 9143a9 - a6fd86 - 5a6057 [master]

First, checkout a temp branch:

git checkout -b temp

On temp branch, reset --hard to a commit that you want to change its message (for example, that commit is 946992):

git reset --hard 946992

Use amend to change the message:

git commit --amend -m "<new_message>"

After that the tree will look like this:

dd2e86 - 946992 - 9143a9 - a6fd86 - 5a6057 [master]
            b886a0 [temp]

Then, cherry-pick all the commit that is ahead of 946992 from master to temp and commit them, use amend if you want to change their messages as well:

git cherry-pick 9143a9
git commit --amend -m "<new_message>
git cherry-pick 5a6057
git commit --amend -m "<new_message>

The tree now looks like this:

dd2e86 - 946992 - 9143a9 - a6fd86 - 5a6057 [master]
                b886a0 - 41ab2c - 6c2a3s - 7c88c9 [temp]

Now force push the temp branch to remote:

git push --force origin temp:master

The final step, delete branch master on local, git fetch origin to pull branch master from the server, then switch to branch master and delete branch temp.

Now both your local and remote will have all the messages updated.

How do I get the real .height() of a overflow: hidden or overflow: scroll div?

For those that are not overflowing but hiding by negative margin:

$('#element').height() + -parseInt($('#element').css("margin-top"));

(ugly but only one that works so far)

How can I specify my .keystore file with Spring Boot and Tomcat?

For external keystores, prefix with "file:"


Multiple aggregate functions in HAVING clause

Something like this?

AND COUNT(caseID) < 4

Creating a left-arrow button (like UINavigationBar's "back" style) on a UIToolbar

    self.navigationItem.leftBarButtonItem = self.navigationItem.backBarButtonItem;

Works for me. I used this when I had more tabs then could fit on the tab bar, and a view controller pushed from the "More" overrode the leftBarButtonItem in its viewDidLoad.

How to save a pandas DataFrame table as a png

The following would need extensive customisation to format the table correctly, but the bones of it works:

import numpy as np
from PIL import Image, ImageDraw, ImageFont
import pandas as pd

df = pd.DataFrame({ 'A' : 1.,
                     'B' : pd.Series(1,index=list(range(4)),dtype='float32'),
                     'C' : np.array([3] * 4,dtype='int32'),
                     'D' : pd.Categorical(["test","train","test","train"]),
                     'E' : 'foo' })

class DrawTable():
    def __init__(self,_df):
        self.rows,self.cols = _df.shape
        img_size = (300,200)
        self.border = 50
        self.bg_col = (255,255,255)
        self.div_w = 1
        self.div_col = (128,128,128)
        self.head_w = 2
        self.head_col = (0,0,0)
        self.image ="RGBA", img_size,self.bg_col)
        self.draw = ImageDraw.Draw(self.image)
    def draw_grid(self):
        width,height = self.image.size
        row_step = (height-self.border*2)/(self.rows)
        col_step = (width-self.border*2)/(self.cols)
        for row in range(1,self.rows+1):
            for col in range(1,self.cols+1):
        self.row_step = row_step
        self.col_step = col_step
    def populate(self,_df2):
        font = ImageFont.load_default().font
        for row in range(self.rows):
            for col in range(self.cols):
                text = str(_df2.iloc[row,col])
                text_w, text_h = font.getsize(text)
                x_pos = self.border+self.col_step*(col+1)-text_w
                y_pos = self.border+self.row_step*row
        for col in range(self.cols):
            text = str(_df2.columns[col])
            text_w, text_h = font.getsize(text)
            x_pos = self.border+self.col_step*(col+1)-text_w
            y_pos = self.border - self.row_step//2
    def save(self,filename):
            print(filename," Saved.")
            print("Error saving:",filename)

table1 = DrawTable(df)'C:/Users/user/Pictures/table1.png')

The output looks like this:

enter image description here

Can't subtract offset-naive and offset-aware datetimes

The psycopg2 module has its own timezone definitions, so I ended up writing my own wrapper around utcnow:

def pg_utcnow():
    import psycopg2
    return datetime.utcnow().replace(, name=None))

and just use pg_utcnow whenever you need the current time to compare against a PostgreSQL timestamptz

How to convert ActiveRecord results into an array of hashes

May be?

If you need symbols keys: { |r| r.attributes.symbolize_keys }

How to get the number of threads in a Java process

ManagementFactory.getThreadMXBean().getThreadCount() doesn't limit itself to thread groups as Thread.activeCount() does.

Make new column in Panda dataframe by adding values from other columns

As of Pandas version 0.16.0 you can use assign as follows:

df = pd.DataFrame({"A": [1,2,3], "B": [4,6,9]})
df.assign(C = df.A + df.B)

# Out[383]: 
#    A  B   C
# 0  1  4   5
# 1  2  6   8
# 2  3  9  12

You can add multiple columns this way as follows:

df.assign(C = df.A + df.B,
          Diff = df.B - df.A,
          Mult = df.A * df.B)
# Out[379]: 
#    A  B   C  Diff  Mult
# 0  1  4   5     3     4
# 1  2  6   8     4    12
# 2  3  9  12     6    27

MySQL Multiple Where Clause

This might be what you are after, although depending on how many style_id's there are, it would be tricky to implement (not sure if those style_id's are static or not). If this is the case, then it is not really possible what you are wanting as the WHERE clause works on a row to row basis.

WITH cte as (
    max(decode(style_id,24,style_value)) AS style_colour,
    max(decode(style_id,25,style_value)) AS style_size,
    max(decode(style_id,27,style_value)) AS style_shape
  style_colour = 'red'
  and style_size = 'big'
  and style_shape = 'round'!4/fa5cf/18

ActionBar text color

you can change color of any text by use html <font> attribute directly in xml files. for example in strings.xml :

    <string name = "app_name">
        <html><font color="#001aff">Multi</font></html>
        <html><font color="#ff0044">color</font></html>
        <html><font color="#e9c309">Text </font></html>

enter image description here

Properties file with a list as the value for an individual key

Your logic is flawed... basically, you need to:

  1. get the list for the key
  2. if the list is null, create a new list and put it in the map
  3. add the word to the list

You're not doing step 2.

Here's the code you want:

Properties prop = new Properties();
prop.load(new FileInputStream("/"));
for (Map.Entry<Object, Object> entry : prop.entrySet())
    List<String> categoryList = categoryMap.get((String) entry.getKey());
    if (categoryList == null)
        categoryList = new ArrayList<String>();
        LogDisplayService.categoryMap.put((String) entry.getKey(), categoryList);
    categoryList.add((String) entry.getValue());

Note also the "correct" way to iterate over the entries of a map/properties - via its entrySet().

pip install - locale.Error: unsupported locale setting

[This answer is target on linux platform only]

The first thing you should know is most of the locale config file located path can be get from localedef --help :

$ localedef --help | tail -n 5
System's directory for character maps : /usr/share/i18n/charmaps
                       repertoire maps: /usr/share/i18n/repertoiremaps
                       locale path    : /usr/lib/locale:/usr/share/i18n
For bug reporting instructions, please see:

See the last /usr/share/i18n ? This is where your xx_XX.UTF-8 config file located:

$ ls /usr/share/i18n/locales/zh_*
/usr/share/i18n/locales/zh_CN  /usr/share/i18n/locales/zh_HK  /usr/share/i18n/locales/zh_SG  /usr/share/i18n/locales/zh_TW

Now what ? We need to compile them into archive binary. One of the way, e.g. assume I have /usr/share/i18n/locales/en_LOVE, I can add it into compile list, i.e. /etc/locale-gen file:

$ tail -1 /etc/locale.gen 

And compile it to binary with sudo locale-gen:

$ sudo locale-gen 
Generating locales (this might take a while)...
  en_AG.UTF-8... done
  en_AU.UTF-8... done
  en_BW.UTF-8... done
  en_LOVE.UTF-8... done
Generation complete.

And now update the system default locale with desired LANG, LC_ALL ...etc with this update-locale:

sudo update-locale LANG=en_LOVE.UTF-8

update-locale actually also means to update this /etc/default/locale file which will source by system on login to setup environment variables:

$ head /etc/default/locale 
#  File generated by update-locale

But we may not want to reboot to take effect, so we can just source it to environment variable in current shell session:

$ . /etc/default/locale

How about sudo dpkg-reconfigure locales ? If you play around it you will know this command basically act as GUI to simplify the above steps, i.e. Edit /etc/locale.gen -> sudo locale-gen -> sudo update-locale LANG=en_LOVE.UTF-8

For python, as long as /etc/locale.gen contains that locale candidate and locale.gen get compiled, setlocale(category, locale) should work without throws locale.Error: unsupoorted locale setting. You can check the correct string en_US.UTF-8/en_US/....etc to be set in setlocale(), by observing /etc/locale.gen file, and then uncomment and compile it as desired. zh_CN GB2312 without dot in that file means the correct string is zh_CN and zh_CN.GB2312.

What is a Windows Handle?

A HANDLE is a context-specific unique identifier. By context-specific, I mean that a handle obtained from one context cannot necessarily be used in any other aribtrary context that also works on HANDLEs.

For example, GetModuleHandle returns a unique identifier to a currently loaded module. The returned handle can be used in other functions that accept module handles. It cannot be given to functions that require other types of handles. For example, you couldn't give a handle returned from GetModuleHandle to HeapDestroy and expect it to do something sensible.

The HANDLE itself is just an integral type. Usually, but not necessarily, it is a pointer to some underlying type or memory location. For example, the HANDLE returned by GetModuleHandle is actually a pointer to the base virtual memory address of the module. But there is no rule stating that handles must be pointers. A handle could also just be a simple integer (which could possibly be used by some Win32 API as an index into an array).

HANDLEs are intentionally opaque representations that provide encapsulation and abstraction from internal Win32 resources. This way, the Win32 APIs could potentially change the underlying type behind a HANDLE, without it impacting user code in any way (at least that's the idea).

Consider these three different internal implementations of a Win32 API that I just made up, and assume that Widget is a struct.

Widget * GetWidget (std::string name)
    Widget *w;

    w = findWidget(name);

    return w;
void * GetWidget (std::string name)
    Widget *w;

    w = findWidget(name);

    return reinterpret_cast<void *>(w);
typedef void * HANDLE;

HANDLE GetWidget (std::string name)
    Widget *w;

    w = findWidget(name);

    return reinterpret_cast<HANDLE>(w);

The first example exposes the internal details about the API: it allows the user code to know that GetWidget returns a pointer to a struct Widget. This has a couple of consequences:

  • the user code must have access to the header file that defines the Widget struct
  • the user code could potentially modify internal parts of the returned Widget struct

Both of these consequences may be undesirable.

The second example hides this internal detail from the user code, by returning just void *. The user code doesn't need access to the header that defines the Widget struct.

The third example is exactly the same as the second, but we just call the void * a HANDLE instead. Perhaps this discourages user code from trying to figure out exactly what the void * points to.

Why go through this trouble? Consider this fourth example of a newer version of this same API:

typedef void * HANDLE;

HANDLE GetWidget (std::string name)
    NewImprovedWidget *w;

    w = findImprovedWidget(name);

    return reinterpret_cast<HANDLE>(w);

Notice that the function's interface is identical to the third example above. This means that user code can continue to use this new version of the API, without any changes, even though the "behind the scenes" implementation has changed to use the NewImprovedWidget struct instead.

The handles in these example are really just a new, presumably friendlier, name for void *, which is exactly what a HANDLE is in the Win32 API (look it up at MSDN). It provides an opaque wall between the user code and the Win32 library's internal representations that increases portability, between versions of Windows, of code that uses the Win32 API.

Remove Select arrow on IE

I would suggest mine solution that you can find in this GitHub repo. This works also for IE8 and IE9 with a custom arrow that comes from an icon font.

Examples of Custom Cross Browser Drop-down in action: check them with all your browsers to see the cross-browser feature.

Anyway, let's start with the modern browsers and then we will see the solution for the older ones.

Drop-down Arrow for Chrome, Firefox, Opera, Internet Explorer 10+

For these browser, it is easy to set the same background image for the drop-down in order to have the same arrow.

To do so, you have to reset the browser's default style for the select tag and set new background rules (like suggested before).

select {
    /* you should keep these firsts rules in place to maintain cross-browser behaviour */
    -webkit-appearance: none;
    -moz-appearance: none;
    -o-appearance: none;
    appearance: none;
    background-image: url('<custom_arrow_image_url_here>');
    background-position: 98% center;
    background-repeat: no-repeat;
    outline: none;

The appearance rules are set to none to reset browsers default ones, if you want to have the same aspect for each arrow, you should keep them in place.

The background rules in the examples are set with SVG inline images that represent different arrows. They are positioned 98% from left to keep some margin to the right border (you can easily modify the position as you wish).

In order to maintain the correct cross-browser behavior, the only other rule that have to be left in place is the outline. This rule resets the default border that appears (in some browsers) when the element is clicked. All the others rules can be easily modified if needed.

Drop-down Arrow for Internet Explorer 8 (IE8) and Internet Explorer 9 (IE9) using Icon Font

This is the harder part... Or maybe not.

There is no standard rule to hide the default arrows for these browsers (like the select::-ms-expand for IE10+). The solution is to hide the part of the drop-down that contains the default arrow and insert an arrow icon font (or a SVG, if you prefer) similar to the SVG that is used in the other browsers (see the select CSS rule for more details about the inline SVG used).

The very first step is to set a class that can recognize the browser: this is the reason why I have used the conditional IE IFs at the beginning of the code. These IFs are used to attach specific classes to the html tag to recognize the older IE browser.

After that, every select in the HTML have to be wrapped by a div (or whatever tag that can wraps an element). At this wrapper just add the class that contains the icon font.

<div class="selectTagWrapper prefix-icon-arrow-down-fill">

In easy words, this wrapper is used to simulate the select tag.

To act like a drop-down, the wrapper must have a border, because we hide the one that comes from the select.

Notice that we cannot use the select border because we have to hide the default arrow lengthening it 25% more than the wrapper. Consequently its right border should not be visible because we hide this 25% more by the overflow: hidden rule applied to the select itself.

The custom arrow icon-font is placed in the pseudo class :before where the rule content contains the reference for the arrow (in this case it is a right parenthesis).

We also place this arrow in an absolute position to center it as much as possible (if you use different icon fonts, remember to adjust them opportunely by changing top and left values and the font size).

.ie8 .prefix-icon-arrow-down-fill:before,
.ie9 .prefix-icon-arrow-down-fill:before {
    content: ")";
    position: absolute;
    top: 43%;
    left: 93%;
    font-size: 6px;

You can easily create and substitute the background arrow or the icon font arrow, with every one that you want simply changing it in the background-image rule or making a new icon font file by yourself.

When should I use File.separator and when File.pathSeparator?

You use separator when you are building a file path. So in unix the separator is /. So if you wanted to build the unix path /var/temp you would do it like this:

String path = File.separator + "var"+ File.separator + "temp"

You use the pathSeparator when you are dealing with a list of files like in a classpath. For example, if your app took a list of jars as argument the standard way to format that list on unix is: /path/to/jar1.jar:/path/to/jar2.jar:/path/to/jar3.jar

So given a list of files you would do something like this:

String listOfFiles = ...
String[] filePaths = listOfFiles.split(File.pathSeparator);

"Stack overflow in line 0" on Internet Explorer

My was "at line 1" instead but...

I got this problem when using jQuery's .clone method. I replaced these by using making jQuery objects from the html string: $($(selector).html()).

After updating Entity Framework model, Visual Studio does not see changes

I've also experienced this problem with none of the classes being generated under the file. In my case it was down to issues with how I had built the DB in SQL2012. I'd set a column in a table to nullable that was also a foreign key and although I think you should be able to do this it caused a problem in EF5.

As soon as this was cleared and the diagram updated from the database they reappeared.

EF5 VS2013

Remove characters from a string

Another method that no one has talked about so far is the substr method to produce strings out of another string...this is useful if your string has defined length and the characters your removing are on either end of the string...or within some "static dimension" of the string.

How to use XPath in Python?

If you want to have the power of XPATH combined with the ability to also use CSS at any point you can use parsel:

>>> from parsel import Selector
>>> sel = Selector(text=u"""<html>
            <h1>Hello, Parsel!</h1>
                <li><a href="">Link 1</a></li>
                <li><a href="">Link 2</a></li>
>>> sel.css('h1::text').extract_first()
'Hello, Parsel!'
>>> sel.xpath('//h1/text()').extract_first()
'Hello, Parsel!'

Shell script current directory?

To print the current working Directory i.e. pwd just type command like:

echo "the PWD is : ${pwd}"

Head and tail in one line

For O(1) complexity of head,tail operation you should use deque however.

Following way:

from collections import deque
l = deque([1,2,3,4,5,6,7,8,9])
head, tail = l.popleft(), l

It's useful when you must iterate through all elements of the list. For example in naive merging 2 partitions in merge sort.

get current date from [NSDate date] but set the time to 10:00 am

As with all date manipulation you have to use NSDateComponents and NSCalendar

NSDate *now = [NSDate date];
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier: NSCalendarIdentifierGregorian];
NSDateComponents *components = [calendar components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay fromDate:now];
[components setHour:10];
NSDate *today10am = [calendar dateFromComponents:components];

in iOS8 Apple introduced a convenience method that saves a few lines of code:

NSDate *d = [calendar dateBySettingHour:10 minute:0 second:0 ofDate:[NSDate date] options:0];


let calendar: NSCalendar! = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)
let now: NSDate! = NSDate()

let date10h = calendar.dateBySettingHour(10, minute: 0, second: 0, ofDate: now, options: NSCalendarOptions.MatchFirst)!

How do you convert WSDLs to Java classes using Eclipse?

In Eclipse Kepler it is very easy to generate Web Service Client classes,You can achieve this by following steps .

RightClick on any Project->Create New Other ->Web Services->Web Service Client->Then paste the wsdl url(or location) in Service Definition->Next->Finish

You will see the generated classes are inside your src folder.

NOTE :Without eclipse also you can generate client classes from wsdl file by using wsimport command utility which ships with JDK.

refer this link Create Web service client using wsdl

Table columns, setting both min and max width with css

Tables work differently; sometimes counter-intuitively.

The solution is to use width on the table cells instead of max-width.

Although it may sound like in that case the cells won't shrink below the given width, they will actually.
with no restrictions on c, if you give the table a width of 70px, the widths of a, b and c will come out as 16, 42 and 12 pixels, respectively.
With a table width of 400 pixels, they behave like you say you expect in your grid above.
Only when you try to give the table too small a size (smaller than a.min+b.min+the content of C) will it fail: then the table itself will be wider than specified.

I made a snippet based on your fiddle, in which I removed all the borders and paddings and border-spacing, so you can measure the widths more accurately.

table {_x000D_
  width: 70px;_x000D_
table, tbody, tr, td {_x000D_
  margin: 0;_x000D_
  padding: 0;_x000D_
  border: 0;_x000D_
  border-spacing: 0;_x000D_
.a, .c {_x000D_
  background-color: red;_x000D_
.b {_x000D_
  background-color: #F77;_x000D_
.a {_x000D_
  min-width: 10px;_x000D_
  width: 20px;_x000D_
  max-width: 20px;_x000D_
.b {_x000D_
  min-width: 40px;_x000D_
  width: 45px;_x000D_
  max-width: 45px;_x000D_
.c {}
    <td class="a">A</td>_x000D_
    <td class="b">B</td>_x000D_
    <td class="c">C</td>_x000D_

How to change the background color on a Java panel?

I think what he is trying to say is to use the getContentPane().setBackground(Color.the_Color_you_want_here)

but if u want to set the color to any other then the JFrame, you use the object.setBackground(Color.the_Color_you_want_here)



Bootstrap: How to center align content inside column?

Want to center an image? Very easy, Bootstrap comes with two classes, .center-block and text-center.

Use the former in the case of your image being a BLOCK element, for example, adding img-responsive class to your img makes the img a block element. You should know this if you know how to navigate in the web console and see applied styles to an element.

Don't want to use a class? No problem, here is the CSS bootstrap uses. You can make a custom class or write a CSS rule for the element to match the Bootstrap class.

 // In case you're dealing with a block element apply this to the element itself 
.center-block {

// In case you're dealing with a inline element apply this to the parent 
.text-center {

How can I generate a self-signed certificate with SubjectAltName using OpenSSL?

Can someone help me with the exact syntax?

It's a three-step process, and it involves modifying the openssl.cnf file. You might be able to do it with only command line options, but I don't do it that way.

Find your openssl.cnf file. It is likely located in /usr/lib/ssl/openssl.cnf:

$ find /usr/lib -name openssl.cnf

On my Debian system, /usr/lib/ssl/openssl.cnf is used by the built-in openssl program. On recent Debian systems it is located at /etc/ssl/openssl.cnf

You can determine which openssl.cnf is being used by adding a spurious XXX to the file and see if openssl chokes.

First, modify the req parameters. Add an alternate_names section to openssl.cnf with the names you want to use. There are no existing alternate_names sections, so it does not matter where you add it.

[ alternate_names ]

DNS.1        =
DNS.2        =
DNS.3        =
DNS.4        =

Next, add the following to the existing [ v3_ca ] section. Search for the exact string [ v3_ca ]:

subjectAltName      = @alternate_names

You might change keyUsage to the following under [ v3_ca ]:

keyUsage = digitalSignature, keyEncipherment

digitalSignature and keyEncipherment are standard fare for a server certificate. Don't worry about nonRepudiation. It's a useless bit thought up by computer science guys/gals who wanted to be lawyers. It means nothing in the legal world.

In the end, the IETF (RFC 5280), browsers and CAs run fast and loose, so it probably does not matter what key usage you provide.

Second, modify the signing parameters. Find this line under the CA_default section:

# Extension copying option: use with caution.
# copy_extensions = copy

And change it to:

# Extension copying option: use with caution.
copy_extensions = copy

This ensures the SANs are copied into the certificate. The other ways to copy the DNS names are broken.

Third, generate your self-signed certificate:

$ openssl genrsa -out private.key 3072
$ openssl req -new -x509 -key private.key -sha256 -out certificate.pem -days 730
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.

Finally, examine the certificate:

$ openssl x509 -in certificate.pem -text -noout
        Version: 3 (0x2)
        Serial Number: 9647297427330319047 (0x85e215e5869042c7)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, ST=MD, L=Baltimore, O=Test CA, Limited, CN=Test CA/[email protected]
            Not Before: Feb  1 05:23:05 2014 GMT
            Not After : Feb  1 05:23:05 2016 GMT
        Subject: C=US, ST=MD, L=Baltimore, O=Test CA, Limited, CN=Test CA/[email protected]
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (3072 bit)
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Key Identifier:
            X509v3 Authority Key Identifier:

            X509v3 Basic Constraints: critical
            X509v3 Key Usage:
                Digital Signature, Non Repudiation, Key Encipherment, Certificate Sign
            X509v3 Subject Alternative Name:
    Signature Algorithm: sha256WithRSAEncryption

Does height and width not apply to span?

Try using a div instead of the span or using the CSS display: block; or display: inline-block;span is by default an inline element which cannot take width and height properties.

Validate SSL certificates with Python

pyOpenSSL is an interface to the OpenSSL library. It should provide everything you need.

How do I add records to a DataGridView in VB.Net?

The function you're looking for is 'Insert'. It takes as its parameters the index you want to insert at, and an array of values to use for the new row values. Typical usage might include:

myDataGridView.Rows.Insert(4,new object[]{value1,value2,value3});

or something to that effect.

How to set environment variables in PyCharm?

This is what you can do to source an .env (and .flaskenv) file in the pycharm flask/django console. It would also work for a normal python console of course.

  1. Do pip install python-dotenv in your environment (the same as being pointed to by pycharm).

  2. Go to: Settings > Build ,Execution, Deployment > Console > Flask/django Console

  3. In "starting script" include something like this near the top:

    from dotenv import load_dotenv load_dotenv(verbose=True)

The .env file can look like this: export KEY=VALUE

It doesn't matter if one includes export or not for dotenv to read it.

As an alternative you could also source the .env file in the activate shell script for the respective virtual environement.

How to grep recursively, but only in files with certain extensions?

ag (the silver searcher) has pretty simple syntax for this

       -G --file-search-regex PATTERN
          Only search files whose names match PATTERN.


ag -G *.h -G *.cpp CP_Image <path>

React JS Error: is not defined react/jsx-no-undef

Here you have not specified class name to be imported from Map.js file. If Map is class exportable class name exist in the Map.js file, your code should be as follow.

import React, { Component } from 'react';
import Map from  './Map';
class App extends Component {
   render() {
     return (
         <div className="App">
export default App;

Matrix Multiplication in pure Python?

When I had to do some matrix arithmetic I defined a new class to help. Within such a class you can define magic methods like __add__, or, in your use-case, __matmul__, allowing you to define x = a @ b or a @= b rather than matrixMult(a,b). __matmul__ was added in Python 3.5 per PEP 465.

I have included some code which implements this below (I excluded the prohibitively long __init__ method, which essentially creates a two-dimensional list self.mat and a tuple self.order according to what is passed to it)

class Matrix:
    def __matmul__(self, multiplier):
        if self.order[1] != multiplier.order[0]:
            raise ValueError("The multiplier was non-conformable under multiplication.")
        return [[sum(a*b for a,b in zip(srow,mcol)) for mcol in zip(*multiplier.mat)] for srow in self.mat]

    def __imatmul__(self, multiplier):
        self.mat = self @ multiplier
        return self.mat

    def __rmatmul__(self, multiplicand):
        if multiplicand.order[1] != self.order[0]:
            raise ValueError("The multiplier was non-conformable under multiplication.")
        return [[sum(a*b for a,b in zip(mrow,scol)) for scol in zip(*self.mat)] for mrow in multiplicand.mat]


  • __rmatmul__ is used if b @ a is called and b does not implement __matmul__ (e.g. if I wanted to implement premultiplying by a 2D list)
  • __imatmul__ is required for a @= b to work correctly;
  • If a matrix is non-conformable under multiplication it means that it cannot be multiplied, usually because it has more or less rows than there are columns in the multiplicand

Java HttpRequest JSON & Response Handling

The simplest way is using libraries like google-http-java-client but if you want parse the JSON response by yourself you can do that in a multiple ways, you can use org.json, json-simple, Gson, minimal-json, jackson-mapper-asl (from 1.x)... etc

A set of simple examples:

Using Gson:


import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;

public class Gson {

    public static void main(String[] args) {

    public HttpResponse http(String url, String body) {

        try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {
            HttpPost request = new HttpPost(url);
            StringEntity params = new StringEntity(body);
            request.addHeader("content-type", "application/json");
            HttpResponse result = httpClient.execute(request);
            String json = EntityUtils.toString(result.getEntity(), "UTF-8");

   gson = new;
            Response respuesta = gson.fromJson(json, Response.class);


        } catch (IOException ex) {
        return null;

    public class Response{

        private String example;
        private String fr;

        public String getExample() {
            return example;
        public void setExample(String example) {
            this.example = example;
        public String getFr() {
            return fr;
        public void setFr(String fr) {
   = fr;

Using json-simple:


import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;

public class JsonSimple {

    public static void main(String[] args) {


    public HttpResponse http(String url, String body) {

        try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {
            HttpPost request = new HttpPost(url);
            StringEntity params = new StringEntity(body);
            request.addHeader("content-type", "application/json");
            HttpResponse result = httpClient.execute(request);

            String json = EntityUtils.toString(result.getEntity(), "UTF-8");
            try {
                JSONParser parser = new JSONParser();
                Object resultObject = parser.parse(json);

                if (resultObject instanceof JSONArray) {
                    JSONArray array=(JSONArray)resultObject;
                    for (Object object : array) {
                        JSONObject obj =(JSONObject)object;

                }else if (resultObject instanceof JSONObject) {
                    JSONObject obj =(JSONObject)resultObject;

            } catch (Exception e) {
                // TODO: handle exception

        } catch (IOException ex) {
        return null;


CSS3 Transition - Fade out effect

Since display is not one of the animatable CSS properties. One display:none fadeOut animation replacement with pure CSS3 animations, just set width:0 and height:0 at last frame, and use animation-fill-mode: forwards to keep width:0 and height:0 properties.

@-webkit-keyframes fadeOut {
    0% { opacity: 1;}
    99% { opacity: 0.01;width: 100%; height: 100%;}
    100% { opacity: 0;width: 0; height: 0;}
@keyframes fadeOut {
    0% { opacity: 1;}
    99% { opacity: 0.01;width: 100%; height: 100%;}
    100% { opacity: 0;width: 0; height: 0;}

    display: block;
    -webkit-animation: fadeOut 1s;
    animation: fadeOut 1s;
    animation-fill-mode: forwards;

Apache Tomcat Not Showing in Eclipse Server Runtime Environments

You may get more success if you do a "search" for the runtime env from the preferences screen instead of hitting "add" - see this demo on youtube. - When you hit search, you are prompted to point to the tomcat directory and then it SHOULD add it as a server runtime environment. Unfortunately for me, that is not the case (I get "no new server runtime environments were found") But you might have more success.

Multiline TextView in Android?

Why don't you declare a string instead of writing a long lines into the layout file. For this you have to declare a line of code into layout file 'android:text="@string/text"' and go to the \\app\src\main\res\values\strings.xml and add a line of code ' Your multiline text here' Also use '\n' to break the line from any point else the line will automatically be adjusted.

iterate through a map in javascript

I'd use standard javascript:

for (var m in myMap){
    for (var i=0;i<myMap[m].length;i++){
    ... do something with myMap[m][i] ...

Note the different ways of treating objects and arrays.

What should be the package name of android app?

Visit and try to fill "Android package name". In some cases it can write error: "Invalid Android package name".

In it is written:

And although the application ID looks like a traditional Java package name, the naming rules for the application ID are a bit more restrictive:

  • It must have at least two segments (one or more dots).
  • Each segment must start with a letter.
  • All characters must be alphanumeric or an underscore [a-zA-Z0-9_].

So, "" and "" are errors.

How can I keep a container running on Kubernetes?

You could use this CMD in your Dockerfile:

CMD exec /bin/bash -c "trap : TERM INT; sleep infinity & wait"

This will keep your container alive until it is told to stop. Using trap and wait will make your container react immediately to a stop request. Without trap/wait stopping will take a few seconds.

For busybox based images (used in alpine based images) sleep does not know about the infinity argument. This workaround gives you the same immediate response to a docker stop like in the above example:

CMD exec /bin/sh -c "trap : TERM INT; sleep 9999999999d & wait"

How do I add slashes to a string in Javascript?

To be sure, you need to not only replace the single quotes, but as well the already escaped ones:

"first ' and \' second".replace(/'|\\'/g, "\\'")

PHPExcel Make first row bold

The simple way to make bold headers:

$row = 1;
foreach($tittles as $index => $tittle) {
    $worksheet->getStyleByColumnAndRow($index + 1, $row)->getFont()->setBold(true);
    $worksheet->setCellValueByColumnAndRow($index + 1, $row, $tittle);

How to close a JavaFX application on window close?



this should terminate thread main and end the main program

VT-x is disabled in the BIOS for both all CPU modes (VERR_VMX_MSR_ALL_VMX_DISABLED)

For latest Windows 10 (HP & Intel motherboard/processor),

Follow the below steps, starting with :

Settings ->
Update & Security ->
Recovery ->
Advanced startUp -> Restart now

F10 (System Recovery) -> System Configuration tab -> Virtualization Technology


F10 to save and exit

Storing and Retrieving ArrayList values from hashmap

Our variable:

Map<String, List<Integer>> map = new HashMap<String, List<Integer>>();

To store:

map.put("mango", new ArrayList<Integer>(Arrays.asList(0, 4, 8, 9, 12)));

To add numbers one and one, you can do something like this:

String key = "mango";
int number = 42;
if (map.get(key) == null) {
    map.put(key, new ArrayList<Integer>());

In Java 8 you can use putIfAbsent to add the list if it did not exist already:

map.putIfAbsent(key, new ArrayList<Integer>());

Use the map.entrySet() method to iterate on:

for (Entry<String, List<Integer>> ee : map.entrySet()) {
    String key = ee.getKey();
    List<Integer> values = ee.getValue();
    // TODO: Do something.

What does "all" stand for in a makefile?

A build, as Makefile understands it, consists of a lot of targets. For example, to build a project you might need

  1. Build file1.o out of file1.c
  2. Build file2.o out of file2.c
  3. Build file3.o out of file3.c
  4. Build executable1 out of file1.o and file3.o
  5. Build executable2 out of file2.o

If you implemented this workflow with makefile, you could make each of the targets separately. For example, if you wrote

make file1.o

it would only build that file, if necessary.

The name of all is not fixed. It's just a conventional name; all target denotes that if you invoke it, make will build all what's needed to make a complete build. This is usually a dummy target, which doesn't create any files, but merely depends on the other files. For the example above, building all necessary is building executables, the other files being pulled in as dependencies. So in the makefile it looks like this:

all: executable1 executable2

all target is usually the first in the makefile, since if you just write make in command line, without specifying the target, it will build the first target. And you expect it to be all.

all is usually also a .PHONY target. Learn more here.

How do you fade in/out a background color using jquery?

Usually you can use the .animate() method to manipulate arbitrary CSS properties, but for background colors you need to use the color plugin. Once you include this plugin, you can use something like others have indicated $('div').animate({backgroundColor: '#f00'}) to change the color.

As others have written, some of this can be done using the jQuery UI library as well.

How do I clone a specific Git branch?

git --branch <branchname> <url>

But bash completion don't get this key: --branch

AcquireConnection method call to the connection manager <Excel Connection Manager> failed with error code 0xC0202009

In my case the problem was the 32/64 bit driver which I solved by configuring the properties of the sql server job:

enter image description here

What is the difference between Builder Design pattern and Factory Design pattern?

One striking difference between Builder & factory which I could make out was the following

suppose we have a car

class Car
  bool HasGPS;
  bool IsCityCar;
  bool IsSportsCar;
  int   Cylenders;
  int Seats;

     void Car(bool hasGPs=false,bool IsCityCar=false,bool IsSportsCar=false, int Cylender=2, int Seats=4);

In the above interface we can get car by the following way :

 int main()
    BadCar = new Car(false,false,true,4,4);

but what if, some exception happens while creating the Seats ??? YOU WILL NOT GET THE OBJECT AT ALL // BUT

suppose you have implementation like the following

class Car
    bool mHasGPS;
    bool mIsCityCar;
    bool mIsSportsCar;
    int mCylenders;
    int mSeats;

    void Car() : mHasGPs(false), mIsCityCar(false), mIsSportsCar(false), mCylender(2), mSeats(4) {}
    void SetGPS(bool hasGPs=false)  {mHasGPs = hasGPs;}
    void SetCity(bool CityCar)  {mIsCityCar = CityCar;}
    void SetSports(bool SportsCar)  {mIsSportsCar = SportsCar;}
    void SetCylender(int Cylender)  {mCylenders = Cylender;}    
    void SetSeats(int seat) {mSeats = seat;}    

 class CarBuilder 
    Car* mCar;
        CarBuilder():mCar(NULL) {   mCar* = new Car();  }
        ~CarBuilder()   {   if(mCar)    {   delete mCar;    }
        Car* GetCar()   {   return mCar; mCar=new Car();    }
        CarBuilder* SetSeats(int n) {   mCar->SetSeats(n); return this; }
        CarBuilder* SetCylender(int n)  {   mCar->SetCylender(n); return this;  }
        CarBuilder* SetSports(bool val) {   mCar->SetSports(val); return this;  }
        CarBuilder* SetCity(bool val)   {   mCar->SetCity(val); return this;    }
        CarBuilder* SetGPS(bool val)    {   mCar->SetGPS(val); return this; }

Now you can create like this

 int main()
   CarBuilder* bp =new CarBuilder;
    Car* NewCar  = bp->SetSeats(4)->SetSports(4)->SetCity(ture)->SetGPS(false)->SetSports(true)->GetCar();





     Car* Car_II=  bp->GetCar();


Here in the second case , even if one operation fails you would still get the Car.

May be that car does not works perfectly later but , you would have the object.

Because Factory Method gives you the Car in single call , whereas the Builder builds one by one.

Although, It depends on the needs of the deign which one to go for.

inject bean reference into a Quartz job in Spring?

I faced the similiar problem and came out from it with following approach:

<!-- Quartz Job -->
<bean name="JobA" class="org.springframework.scheduling.quartz.JobDetailFactoryBean">
    <!-- <constructor-arg ref="dao.DAOFramework" /> -->
     <property name="jobDataAsMap">
        <entry key="daoBean" value-ref="dao.DAOFramework" />
    <property name="jobClass" value="" />
    <property name="durability" value="true"/>

In above code I inject dao.DAOFramework bean into JobA bean and in inside ExecuteInternal method you can get injected bean like:

  daoFramework = (DAOFramework)context.getMergedJobDataMap().get("daoBean");

I hope it helps! Thank you.

Find the nth occurrence of substring in a string

Here's another re + itertools version that should work when searching for either a str or a RegexpObject. I will freely admit that this is likely over-engineered, but for some reason it entertained me.

import itertools
import re

def find_nth(haystack, needle, n = 1):
    Find the starting index of the nth occurrence of ``needle`` in \

    If ``needle`` is a ``str``, this will perform an exact substring
    match; if it is a ``RegexpObject``, this will perform a regex

    If ``needle`` doesn't appear in ``haystack``, return ``-1``. If
    ``needle`` doesn't appear in ``haystack`` ``n`` times,
    return ``-1``.

    * ``needle`` the substring (or a ``RegexpObject``) to find
    * ``haystack`` is a ``str``
    * an ``int`` indicating which occurrence to find; defaults to ``1``

    >>> find_nth("foo", "o", 1)
    >>> find_nth("foo", "o", 2)
    >>> find_nth("foo", "o", 3)
    >>> find_nth("foo", "b")
    >>> import re
    >>> either_o = re.compile("[oO]")
    >>> find_nth("foo", either_o, 1)
    >>> find_nth("FOO", either_o, 1)
    if (hasattr(needle, 'finditer')):
        matches = needle.finditer(haystack)
        matches = re.finditer(re.escape(needle), haystack)
    start_here = itertools.dropwhile(lambda x: x[0] < n, enumerate(matches, 1))
        return next(start_here)[1].start()
    except StopIteration:
        return -1

How to declare array of zeros in python (or an array of a certain size)

The question says "How to declare array of zeros ..." but then the sample code references the Python list:

buckets = []   # this is a list

However, if someone is actually wanting to initialize an array, I suggest:

from array import array

my_arr = array('I', [0] * count)

The Python purist might claim this is not pythonic and suggest:

my_arr = array('I', (0 for i in range(count)))

The pythonic version is very slow and when you have a few hundred arrays to be initialized with thousands of values, the difference is quite noticeable.

Getting all types that implement an interface

I got exceptions in the linq-code so I do it this way (without a complicated extension):

private static IList<Type> loadAllImplementingTypes(Type[] interfaces)
    IList<Type> implementingTypes = new List<Type>();

    // find all types
    foreach (var interfaceType in interfaces)
        foreach (var currentAsm in AppDomain.CurrentDomain.GetAssemblies())
                foreach (var currentType in currentAsm.GetTypes())
                    if (interfaceType.IsAssignableFrom(currentType) && currentType.IsClass && !currentType.IsAbstract)
            catch { }

    return implementingTypes;

How to update UI from another thread running in another class

Felt the need to add this better answer, as nothing except BackgroundWorker seemed to help me, and the answer dealing with that thus far was woefully incomplete. This is how you would update a XAML page called MainWindow that has an Image tag like this:

<Image Name="imgNtwkInd" Source="Images/network_on.jpg" Width="50" />

with a BackgroundWorker process to show if you are connected to the network or not:

using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;

public partial class MainWindow : Window
    private BackgroundWorker bw = new BackgroundWorker();

    public MainWindow()

        // Set up background worker to allow progress reporting and cancellation
        bw.WorkerReportsProgress = true;
        bw.WorkerSupportsCancellation = true;

        // This is your main work process that records progress
        bw.DoWork += new DoWorkEventHandler(SomeClass.DoWork);

        // This will update your page based on that progress
        bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged);

        // This starts your background worker and "DoWork()"

        // When this page closes, this will run and cancel your background worker
        this.Closing += new CancelEventHandler(Page_Unload);

    private void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
        BitmapImage bImg = new BitmapImage();
        bool connected = false;
        string response = e.ProgressPercentage.ToString(); // will either be 1 or 0 for true/false -- this is the result recorded in DoWork()

        if (response == "1")
            connected = true;

        // Do something with the result we got
        if (!connected)
            bImg.UriSource = new Uri("Images/network_off.jpg", UriKind.Relative);
            imgNtwkInd.Source = bImg;
            bImg.UriSource = new Uri("Images/network_on.jpg", UriKind.Relative);
            imgNtwkInd.Source = bImg;

    private void Page_Unload(object sender, CancelEventArgs e)
        bw.CancelAsync();  // stops the background worker when unloading the page

public class SomeClass
    public static bool connected = false;

    public void DoWork(object sender, DoWorkEventArgs e)
        BackgroundWorker bw = sender as BackgroundWorker;

        int i = 0;
            connected = CheckConn();  // do some task and get the result

            if (bw.CancellationPending == true)
                e.Cancel = true;
                // Record your result here
                if (connected)
        while (i == 0);

    private static bool CheckConn()
        bool conn = false;
        Ping png = new Ping();
        string host = "SomeComputerNameHere";

            PingReply pngReply = png.Send(host);
            if (pngReply.Status == IPStatus.Success)
                conn = true;
        catch (PingException ex)
            // write exception to log
        return conn;

For more information:

Want to download a Git repository, what do I need (windows machine)?

I don't want to start a "What's the best unix command line under Windows" war, but have you thought of Cygwin? Git is in the Cygwin package repository.

And you get a lot of beneficial side-effects! (:-)

How can I get the key value in a JSON object?

First off, you're not dealing with a "JSON object." You're dealing with a JavaScript object. JSON is a textual notation, but if your example code works ([0].amount), you've already deserialized that notation into a JavaScript object graph. (What you've quoted isn't valid JSON at all; in JSON, the keys must be in double quotes. What you've quoted is a JavaScript object literal, which is a superset of JSON.)

Here, length of this array is 2.

No, it's 3.

So, i need to get the name (like amount or job... totally four name) and also to count how many names are there?

If you're using an environment that has full ECMAScript5 support, you can use Object.keys (spec | MDN) to get the enumerable keys for one of the objects as an array. If not (or if you just want to loop through them rather than getting an array of them), you can use

var entry;
var name;
entry = array[0];
for (name in entry) {
    // here, `name` will be "amount", "job", "month", then "year" (in no defined order)

Full working example:

(function() {_x000D_
  var array = [_x000D_
      amount: 12185,_x000D_
      job: "GAPA",_x000D_
      month: "JANUARY",_x000D_
      year: "2010"_x000D_
      amount: 147421,_x000D_
      job: "GAPA",_x000D_
      month: "MAY",_x000D_
      year: "2010"_x000D_
      amount: 2347,_x000D_
      job: "GAPA",_x000D_
      month: "AUGUST",_x000D_
      year: "2010"_x000D_
  var entry;_x000D_
  var name;_x000D_
  var count;_x000D_
  entry = array[0];_x000D_
  display("Keys for entry 0:");_x000D_
  count = 0;_x000D_
  for (name in entry) {_x000D_
  display("Total enumerable keys: " + count);_x000D_
  // === Basic utility functions_x000D_
  function display(msg) {_x000D_
    var p = document.createElement('p');_x000D_
    p.innerHTML = msg;_x000D_

Since you're dealing with raw objects, the above loop is fine (unless someone has committed the sin of mucking about with Object.prototype, but let's assume not). But if the object you want the keys from may also inherit enumerable properties from its prototype, you can restrict the loop to only the object's own keys (and not the keys of its prototype) by adding a hasOwnProperty call in there:

for (name in entry) {
  if (entry.hasOwnProperty(name)) {

How to center HTML5 Videos?

I was having the same problem, until I realized that <video> elements are inline elements, not block elements. You need only set the container element to have text-align: center; in order to center the video horizontally on the page.

Laravel 4: Redirect to a given url

Both Redirect::to() and Redirect::away() should work.


Redirect::to() does additional URL checks and generations. Those additional steps are done in Illuminate\Routing\UrlGenerator and do the following, if the passed URL is not a fully valid URL (even with protocol):

Determines if URL is secure
rawurlencode() the URL
trim() URL

src :

How to update a record using sequelize for node?

Using async and await in a modern javascript Es6

const title = "title goes here";
const id = 1;

    const result = await Project.update(
          { title },
          { where: { id } }
    }.catch(err => console.log(err));

you can return result ...

How to find the duration of difference between two dates in java?

The date difference conversion could be handled in a better way using Java built-in class, TimeUnit. It provides utility methods to do that:

Date startDate = // Set start date
Date endDate   = // Set end date

long duration  = endDate.getTime() - startDate.getTime();

long diffInSeconds = TimeUnit.MILLISECONDS.toSeconds(duration);
long diffInMinutes = TimeUnit.MILLISECONDS.toMinutes(duration);
long diffInHours = TimeUnit.MILLISECONDS.toHours(duration);
long diffInDays = TimeUnit.MILLISECONDS.toDays(duration);

How can I compare strings in C using a `switch` statement?

I have published a header file to perform the switch on the strings in C. It contains a set of macro that hide the call to the strcmp() (or similar) in order to mimic a switch-like behaviour. I have tested it only with GCC in Linux, but I'm quite sure that it can be adapted to support other environment.

EDIT: added the code here, as requested

This is the header file you should include:

#ifndef __SWITCHS_H__
#define __SWITCHS_H__

#include <string.h>
#include <regex.h>
#include <stdbool.h>

/** Begin a switch for the string x */
#define switchs(x) \
    { char *__sw = (x); bool __done = false; bool __cont = false; \
        regex_t __regex; regcomp(&__regex, ".*", 0); do {

/** Check if the string matches the cases argument (case sensitive) */
#define cases(x)    } if ( __cont || !strcmp ( __sw, x ) ) \
                        { __done = true; __cont = true;

/** Check if the string matches the icases argument (case insensitive) */
#define icases(x)    } if ( __cont || !strcasecmp ( __sw, x ) ) { \
                        __done = true; __cont = true;

/** Check if the string matches the specified regular expression using regcomp(3) */
#define cases_re(x,flags) } regfree ( &__regex ); if ( __cont || ( \
                              0 == regcomp ( &__regex, x, flags ) && \
                              0 == regexec ( &__regex, __sw, 0, NULL, 0 ) ) ) { \
                                __done = true; __cont = true;

/** Default behaviour */
#define defaults    } if ( !__done || __cont ) {

/** Close the switchs */
#define switchs_end } while ( 0 ); regfree(&__regex); }

#endif // __SWITCHS_H__

And this is how you use it:

switchs(argv[1]) {
        printf("foo or bar (case sensitive)\n");

        printf("pi or Pi or pI or PI (case insensitive)\n");

        printf("Something that start with D (case sensitive)\n");

        printf("Something that start with E (case insensitive)\n");

        // break omitted on purpose

        printf("2 (or 1)\n");

        printf("No match\n");
} switchs_end;

Slick Carousel Uncaught TypeError: $(...).slick is not a function

I solve this by simply add 'https:' to slick cdn link gotfrom slick

Reading in double values with scanf in c

Using %lf will help you in solving this problem.

Use :


How to develop Android app completely using python?

You could try BeeWare - as described on their website:

Write your apps in Python and release them on iOS, Android, Windows, MacOS, Linux, Web, and tvOS using rich, native user interfaces. One codebase. Multiple apps.

Gives you want you want now to write Android Apps in Python, plus has the advantage that you won't need to learn yet another framework in future if you end up also wanting to do something on one of the other listed platforms.

Here's the Tutorial for Android Apps.

How to print a Groovy variable in Jenkins?

You shouldn't use ${varName} when you're outside of strings, you should just use varName. Inside strings you use it like this; echo "this is a string ${someVariable}";. Infact you can place an general java expression inside of ${...}; echo "this is a string ${func(arg1, arg2)}.

Why do I get a "Null value was assigned to a property of primitive type setter of" error message when using HibernateCriteriaBuilder in Grails

There are two way

  • Make sure that db column is not allowed null
  • User Wrapper classes for the primitive type variable like private int var; can be initialized as private Integer var;

How do you convert Html to plain text?

I think it has a simple answer:

public string RemoveHTMLTags(string HTMLCode)
    string str=System.Text.RegularExpressions.Regex.Replace(HTMLCode, "<[^>]*>", "");
    return str;

Error:Execution failed for task ':app:transformClassesWithJarMergingForDebug'

see if their duplicate jars or dependencies your adding remove it and your error will be gone: Eg: if you add android:supportv4 jar and also dependency you will get the error so remove the jar error will be gone

Plot size and resolution with R markdown, knitr, pandoc, beamer

Figure sizes are specified in inches and can be included as a global option of the document output format. For example:

title: "My Document"
    fig_width: 6
    fig_height: 4

And the plot's size in the graphic device can be increased at the chunk level:

```{r, fig.width=14, fig.height=12}          #Expand the plot width to 14 inches

ggplot(aes(x=mycolumn1, y=mycolumn2)) +     #specify the x and y aesthetic
geom_line(size=2) +                         #makes the line thicker
theme_grey(base_size = 25)                  #increases the size of the font

You can also use the out.width and out.height arguments to directly define the size of the plot in the output file:

```{r, out.width="200px", out.height="200px"} #Expand the plot width to 200 pixels

ggplot(aes(x=mycolumn1, y=mycolumn2)) +     #specify the x and y aesthetic
geom_line(size=2) +                         #makes the line thicker
theme_grey(base_size = 25)                  #increases the size of the font

Drop a temporary table if it exists

What you asked for is:


       CREATE TABLE ##CLIENTS_KEYWORD(client_id int)





Since you're always going to create the table, regardless of whether the table is deleted or not; a slightly optimised solution is:





How to refresh app upon shaking the device?

I have written a small example for detecting vertical and horizontal shakes and showing a Toast.

public class Accelerometerka2Activity extends Activity implements SensorEventListener { 
    private float mLastX, mLastY, mLastZ;
    private boolean mInitialized;
    private SensorManager mSensorManager;
    private Sensor mAccelerometer;
    private final float NOISE = (float) 8.0;

    public void onCreate(Bundle savedInstanceState) {
        mInitialized = false;
        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        mSensorManager.registerListener(this, mAccelerometer , SensorManager.SENSOR_DELAY_NORMAL);

    protected void onResume() {
        mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);

    protected void onPause() {

    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        // can be safely ignored for this demo

    public void onSensorChanged(SensorEvent event) {
        float x = event.values[0];
        float y = event.values[1];
        float z = event.values[2];
        if (!mInitialized) {
            mLastX = x;
            mLastY = y;
            mLastZ = z;
            mInitialized = true;
        } else {
            float deltaX = Math.abs(mLastX - x);
            float deltaY = Math.abs(mLastY - y);
            float deltaZ = Math.abs(mLastZ - z);
            if (deltaX < NOISE) deltaX = (float)0.0;
            if (deltaY < NOISE) deltaY = (float)0.0;
            if (deltaZ < NOISE) deltaZ = (float)0.0;
            mLastX = x;
            mLastY = y;
            mLastZ = z;
            if (deltaX > deltaY) {
                Toast.makeText(getBaseContext(), "Horizental", Toast.LENGTH_SHORT).show();
            } else if (deltaY > deltaX) {
                Toast.makeText(getBaseContext(), "Vertical", Toast.LENGTH_SHORT).show();

Cannot connect to the Docker daemon on macOS

Try this to create default.

docker-machine create default

Partition Function COUNT() OVER possible using DISTINCT

I use a solution that is similar to that of David above, but with an additional twist if some rows should be excluded from the count. This assumes that [UserAccountKey] is never null.

-- subtract an extra 1 if null was ranked within the partition,
-- which only happens if there were rows where [Include] <> 'Y'
dense_rank() over (
  partition by [Mth] 
  order by case when [Include] = 'Y' then [UserAccountKey] else null end asc
+ dense_rank() over (
  partition by [Mth] 
  order by case when [Include] = 'Y' then [UserAccountKey] else null end desc
- max(case when [Include] = 'Y' then 0 else 1 end) over (partition by [Mth])
- 1

An SQL Fiddle with an extended example can be found here.

DbEntityValidationException - How can I easily tell what caused the error?

Use try block in your code like

    // Your code...
    // Could also be before try if you know the exception occurs in SaveChanges

catch (DbEntityValidationException e)
    foreach (var eve in e.EntityValidationErrors)
        Console.WriteLine("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
            eve.Entry.Entity.GetType().Name, eve.Entry.State);
        foreach (var ve in eve.ValidationErrors)
            Console.WriteLine("- Property: \"{0}\", Error: \"{1}\"",
                ve.PropertyName, ve.ErrorMessage);

You can check the details here as well


  2. Validation failed for one or more entities. See 'EntityValidationErrors' property for more details


Configuration System Failed to Initialize

If you are dealing with an Azure WebJob - I had to remove the following after upgrading to the latest 4.6.1.

  <compilation debug="true" targetFramework="4.6.1">
      <add assembly="System.Runtime, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>

Hope this helps.

URL to load resources from the classpath in Java

Inspire by @Stephen and

To use

new URL("classpath:org/my/package/resource.extension").openConnection()

just create this class into package and run it into Oracle JVM implementation to work like a charm.



public class Handler extends URLStreamHandler {

    protected URLConnection openConnection(URL u) throws IOException {
        return Thread.currentThread().getContextClassLoader().getResource(u.getPath()).openConnection();

In case you are using another JVM implementation set the system property.


Laravel PHP Command Not Found

For those using Linux with Zsh:

1 - Add this line to your .zshrc file

export PATH="$HOME/.config/composer/vendor/bin:$PATH"

2 - Run

source ~/.zshrc
  • Linux path to composer folder is different from Mac
  • Use $HOME instead of ~ inside the path with Zsh
  • The .zshrc file is hidden in the Home folder
  • export PATH= exports the path in quotes so that the Laravel executable can be located by your system
  • The :$PATH is to avoid overriding what was already in the system path

numpy max vs amax vs maximum

np.maximum not only compares elementwise but also compares array elementwise with single value

>>>np.maximum([23, 14, 16, 20, 25], 18)
array([23, 18, 18, 20, 25])

How to search JSON tree with jQuery

You don't have to use jQuery. Plain JavaScript will do. I wouldn't recommend any library that ports XML standards onto JavaScript, and I was frustrated that no other solution existed for this so I wrote my own library.

I adapted regex to work with JSON.

First, stringify the JSON object. Then, you need to store the starts and lengths of the matched substrings. For example:

"matched".search("ch") // yields 3

For a JSON string, this works exactly the same (unless you are searching explicitly for commas and curly brackets in which case I'd recommend some prior transform of your JSON object before performing regex (i.e. think :, {, }).

Next, you need to reconstruct the JSON object. The algorithm I authored does this by detecting JSON syntax by recursively going backwards from the match index. For instance, the pseudo code might look as follows:

find the next key preceding the match index, call this theKey
then find the number of all occurrences of this key preceding theKey, call this theNumber
using the number of occurrences of all keys with same name as theKey up to position of theKey, traverse the object until keys named theKey has been discovered theNumber times
return this object called parentChain

With this information, it is possible to use regex to filter a JSON object to return the key, the value, and the parent object chain.

You can see the library and code I authored at

What is the difference between #import and #include in Objective-C?

There seems to be a lot of confusion regarding the preprocessor.

What the compiler does when it sees a #include that it replaces that line with the contents of the included files, no questions asked.

So if you have a file a.h with this contents:

typedef int my_number;

and a file b.c with this content:

#include "a.h"
#include "a.h"

the file b.c will be translated by the preprocessor before compilation to

typedef int my_number;
typedef int my_number;

which will result in a compiler error, since the type my_number is defined twice. Even though the definition is the same this is not allowed by the C language.

Since a header often is used in more than one place include guards usually are used in C. This looks like this:

 #ifndef _a_h_included_
 #define _a_h_included_

 typedef int my_number;


The file b.c still would have the whole contents of the header in it twice after being preprocessed. But the second instance would be ignored since the macro _a_h_included_ would already have been defined.

This works really well, but has two drawbacks. First of all the include guards have to be written, and the macro name has to be different in every header. And secondly the compiler has still to look for the header file and read it as often as it is included.

Objective-C has the #import preprocessor instruction (it also can be used for C and C++ code with some compilers and options). This does almost the same as #include, but it also notes internally which file has already been included. The #import line is only replaced by the contents of the named file for the first time it is encountered. Every time after that it is just ignored.

Check if MySQL table exists or not

Updated mysqli version:

if ($result = $mysqli->query("SHOW TABLES LIKE '".$table."'")) {
    if($result->num_rows == 1) {
        echo "Table exists";
else {
    echo "Table does not exist";

Original mysql version:

if(mysql_num_rows(mysql_query("SHOW TABLES LIKE '".$table."'"))==1) 
    echo "Table exists";
else echo "Table does not exist";

Referenced from the PHP docs.

Can you have if-then-else logic in SQL?

Please check whether this helps:

select TOP 1
    (project=1 OR Customer=2 OR company=3) AND
    price IS NOT NULL
ORDER BY company 

How to unlock android phone through ADB

Building on @Bhaskar's answer and others, here's a full command to unlock (tested on Pixel 3):

adb shell input keyevent 26 && adb shell input keyevent 82 && adb shell input text <password> && adb shell input keyevent 66

How to add white spaces in HTML paragraph

This can be done easily and cleanly with float.



    <li>Item 1 <span class="right">(1)</span></li>
    <li>Item 2 <span class="right">(2)</span></li>


ul {
    width: 10em
.right {
    float: right

Sort a list of tuples by 2nd item (integer value)

From python wiki:

>>> from operator import itemgetter, attrgetter    
>>> sorted(student_tuples, key=itemgetter(2))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]    
>>> sorted(student_objects, key=attrgetter('age'))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

No WebApplicationContext found: no ContextLoaderListener registered?

And if you would like to use an existing context, rather than a new context which would be loaded from xml configuration by org.springframework.web.context.ContextLoaderListener, then see ->

Does Python support short-circuiting?

Yes. Try the following in your python interpreter:


>>>False and 3/0
>>>True and 3/0
ZeroDivisionError: integer division or modulo by zero


>>>True or 3/0
>>>False or 3/0
ZeroDivisionError: integer division or modulo by zero

"Press Any Key to Continue" function in C

Use the C Standard Library function getchar() instead as getch() is not a standard function, being provided by Borland TURBO C for MS-DOS/Windows only.

printf("Let the Battle Begin!\n");
printf("Press Any Key to Continue\n");  

Here, getchar() expects you to press the return key so the printf statement should be press ENTER to continue. Even if you press another key, you still need to press ENTER:

printf("Let the Battle Begin!\n");
printf("Press ENTER key to Continue\n");  

If you are using Windows then you can use getch()

printf("Let the Battle Begin!\n");
printf("Press Any Key to Continue\n");
//if you press any character it will continue ,  
//but this is not a standard c function.

char ch;
printf("Let the Battle Begin!\n");
printf("Press ENTER key to Continue\n");    
//here also if you press any other key will wait till pressing ENTER
scanf("%c",&ch); //works as getchar() but here extra variable is required.      

What does "'') " mean in Flask

To answer to your second question. You can just hit the IP address of the machine that your flask app is running, e.g. in a browser on different machine on the same network and you are there. Though, you will not be able to access it if you are on a different network. Firewalls or VLans can cause you problems with reaching your application. If that computer has a public IP, then you can hit that IP from anywhere on the planet and you will be able to reach the app. Usually this might impose some configuration, since most of the public servers are behind some sort of router or firewall.

How to turn off the Eclipse code formatter for certain sections of Java code?

Instead of turning the formatting off, you can configure it not to join already wrapped lines. Similar to Jitter's response, here's for Eclipse STS:

Properties ? Java Code Style ? Formatter ? Enable project specific settings OR Configure Workspace Settings ? Edit ? Line Wrapping (tab) ? check "Never join already wrapped lines"

Save, apply.

enter image description here

How to word wrap text in HTML?

Use word-wrap:break-word attribute along with required width. Mainly, put the width in pixels, not in percentages.

width: 200px;
word-wrap: break-word;

Vertical align middle with Bootstrap responsive grid

.row {
    letter-spacing: -.31em;
    word-spacing: -.43em;
.col-md-4 {
    float: none;
    display: inline-block;
    vertical-align: middle;

Note: .col-md-4 could be any grid column, its just an example here.

Query for array elements inside JSON type

jsonb in Postgres 9.4+

You can use the same query as below, just with jsonb_array_elements().

But rather use the jsonb "contains" operator @> in combination with a matching GIN index on the expression data->'objects':

CREATE INDEX reports_data_gin_idx ON reports
USING gin ((data->'objects') jsonb_path_ops);

SELECT * FROM reports WHERE data->'objects' @> '[{"src":"foo.png"}]';

Since the key objects holds a JSON array, we need to match the structure in the search term and wrap the array element into square brackets, too. Drop the array brackets when searching a plain record.

More explanation and options:

json in Postgres 9.3+

Unnest the JSON array with the function json_array_elements() in a lateral join in the FROM clause and test for its elements:

SELECT data::text, obj
FROM   reports r, json_array_elements(>'{objects}') obj
WHERE  obj->>'src' = 'foo.png';

db<>fiddle here
Old sqlfiddle

The CTE (WITH query) just substitutes for a table reports.
Or, equivalent for just a single level of nesting:

FROM   reports r, json_array_elements(>'objects') obj
WHERE  obj->>'src' = 'foo.png';

->>, -> and #> operators are explained in the manual.

Both queries use an implicit JOIN LATERAL.

Closely related:

How to use subList()

To get the last element, simply use the size of the list as the second parameter. So for example, if you have 35 files, and you want the last five, you would do:

dataList.subList(30, 35);

A guaranteed safe way to do this is:

dataList.subList(Math.max(0, first), Math.min(dataList.size(), last) );

Member '<method>' cannot be accessed with an instance reference

No need to use static in this case as thoroughly explained. You might as well initialise your property without GetItem() method, example of both below:

namespace MyNamespace
    using System;

    public class MyType
        public string MyProperty { get; set; } = new string();
        public static string MyStatic { get; set; } = "I'm static";


using MyType;

public class Somewhere 
    public void Consuming(){

        // through instance of your type
        var myObject = new MyType(); 
        var alpha = myObject.MyProperty;

        // through your type 
        var beta = MyType.MyStatic;

Best practices for SQL varchar column length

I haven't checked this lately, but I know in the past with Oracle that the JDBC driver would reserve a chunk of memory during query execution to hold the result set coming back. The size of the memory chunk is dependent on the column definitions and the fetch size. So the length of the varchar2 columns affects how much memory is reserved. This caused serious performance issues for me years ago as we always used varchar2(4000) (the max at the time) and garbage collection was much less efficient than it is today.

Convert NSDate to String in iOS Swift

Something to keep in mind when creating formatters is to try to reuse the same instance if you can, as formatters are fairly computationally expensive to create. The following is a pattern I frequently use for apps where I can share the same formatter app-wide, adapted from NSHipster.

extension DateFormatter {

    static var sharedDateFormatter: DateFormatter = {
        let dateFormatter = DateFormatter()   
        // Add your formatter configuration here     
        dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
        return dateFormatter


let dateString = DateFormatter.sharedDateFormatter.string(from: Date())

applying css to specific li class

I believe it's because #ID styles trump .class styles when computing the final style of an element. Try changing your li from class to id, or you can try adding !important to your class, like this:

    color: #C1C1C1; !important

Is this a good way to clone an object in ES6?

EDIT: When this answer was posted, {...obj} syntax was not available in most browsers. Nowadays, you should be fine using it (unless you need to support IE 11).

Use Object.assign.

var obj = { a: 1 };
var copy = Object.assign({}, obj);
console.log(copy); // { a: 1 }

However, this won't make a deep clone. There is no native way of deep cloning as of yet.

EDIT: As @Mike 'Pomax' Kamermans mentioned in the comments, you can deep clone simple objects (ie. no prototypes, functions or circular references) using JSON.parse(JSON.stringify(input))

Xcode error - Thread 1: signal SIGABRT

You are trying to load a XIB named DetailViewController, but no such XIB exists or it's not member of your current target.

python, sort descending dataframe with pandas

For pandas 0.17 and above, use this :

test = df.sort_values('one', ascending=False)

Since 'one' is a series in the pandas data frame, hence pandas will not accept the arguments in the form of a list.

Call javascript from MVC controller action

For those that just used a standard form submit (non-AJAX), there's another way to fire some Javascript/JQuery code upon completion of your action.

First, create a string property on your Model.

public class MyModel 
    public string JavascriptToRun { get; set;}

Now, bind to your new model property in the Javascript of your view:

<script type="text/javascript">

Now, also in your view, create a Javascript function that does whatever you need to do:

<script type="text/javascript">

     function ShowErrorPopup() {
          alert('Sorry, we could not process your order.');


Finally, in your controller action, you need to call this new Javascript function:

public ActionResult PurchaseCart(MyModel model)
    // Do something useful

    if (success == false)
        model.JavascriptToRun= "ShowErrorPopup()";
        return View(model);
        return RedirectToAction("Success");

Iterating over dictionaries using 'for' loops

To iterate over keys, it is slower but better to use my_dict.keys(). If you tried to do something like this:

for key in my_dict:
    my_dict[key+"-1"] = my_dict[key]-1

it would create a runtime error because you are changing the keys while the program is running. If you are absolutely set on reducing time, use the for key in my_dict way, but you have been warned.

Can I run CUDA on Intel's integrated graphics processor?

At the present time, Intel graphics chips do not support CUDA. It is possible that, in the nearest future, these chips will support OpenCL (which is a standard that is very similar to CUDA), but this is not guaranteed and their current drivers do not support OpenCL either. (There is an Intel OpenCL SDK available, but, at the present time, it does not give you access to the GPU.)

Newest Intel processors (Sandy Bridge) have a GPU integrated into the CPU core. Your processor may be a previous-generation version, in which case "Intel(HD) graphics" is an independent chip.

Error: JavaFX runtime components are missing, and are required to run this application with JDK 11

This worked for me:

File >> Project Structure >> Modules >> Dependency >> + (on left-side of window)

clicking the "+" sign will let you designate the directory where you have unpacked JavaFX's "lib" folder.

Scope is Compile (which is the default.) You can then edit this to call it JavaFX by double-clicking on the line.

then in:

Run >> Edit Configurations

Add this line to VM Options:

--module-path /path/to/JavaFX/lib --add-modules=javafx.controls

(oh and don't forget to set the SDK)

How to stop C# console applications from closing automatically?

Those solutions mentioned change how your program work.

You can off course put #if DEBUG and #endif around the Console calls, but if you really want to prevent the window from closing only on your dev machine under Visual Studio or if VS isn't running only if you explicitly configure it, and you don't want the annoying 'Press any key to exit...' when running from the command line, the way to go is to use the System.Diagnostics.Debugger API's.

If you only want that to work in DEBUG, simply wrap this code in a [Conditional("DEBUG")] void BreakConditional() method.

// Test some configuration option or another
bool launch;
var env = Environment.GetEnvironmentVariable("LAUNCH_DEBUGGER_IF_NOT_ATTACHED");
if (!bool.TryParse(env, out launch))
    launch = false;

// Break either if a debugger is already attached, or if configured to launch
if (launch || Debugger.IsAttached) {
    if (Debugger.IsAttached || Debugger.Launch())

This also works to debug programs that need elevated privileges, or that need to be able to elevate themselves.

Websocket onerror - how to read error description?

The error Event the onerror handler receives is a simple event not containing such information:

If the user agent was required to fail the WebSocket connection or the WebSocket connection is closed with prejudice, fire a simple event named error at the WebSocket object.

You may have better luck listening for the close event, which is a CloseEvent and indeed has a CloseEvent.code property containing a numerical code according to RFC 6455 11.7 and a CloseEvent.reason string property.

Please note however, that CloseEvent.code (and CloseEvent.reason) are limited in such a way that network probing and other security issues are avoided.

How to browse localhost on Android device?

You can get a public URL for your server running on a specific port on localhost.

At my work place I could access the local server by using the local IP address of my machine in the app, as most of the other answers suggest. But at home I wasn't able to do that for some reason. After trying many answers and spending many hours, I came across It is pretty straight forward. Just download it from within the folder do:

ngrok portnumber

( from command prompt in windows)

./ngrok portnumber

(from terminal in linux)

This will give you a public URL for your local server running on that port number on localhost. You can include in your app and debug it using that URL.

You can securely expose a local web server to the internet and capture all traffic for detailed inspection. You can share the URL with your colleague developer also who might be working remotely and can debug the App/Server interaction.

Hope this saves someone's time someday.

List all files in one directory PHP

Check this out : readdir()

This bit of code should list all entries in a certain directory:

if ($handle = opendir('.')) {

    while (false !== ($entry = readdir($handle))) {

        if ($entry != "." && $entry != "..") {

            echo "$entry\n";


Edit: miah's solution is much more elegant than mine, you should use his solution instead.

C++: Where to initialize variables in constructor

Although it doesn't apply to this specific example, Option 1 allows you to initialize member variables of reference type (or const type, as pointed out below). Option 2 doesn't. In general, Option 1 is the more powerful approach.

How do I do an OR filter in a Django query?

It is worth to note that it's possible to add Q expressions.

For example:

from django.db.models import Q

query = Q(first_name='mark')
query.add(Q(email='[email protected]'), Q.OR)
query.add(Q(last_name='doe'), Q.AND)

queryset = User.objects.filter(query)

This ends up with a query like :

(first_name = 'mark' or email = '[email protected]') and last_name = 'doe'

This way there is no need to deal with or operators, reduce's etc.

Android: How to bind spinner to custom object list?

I think that the best solution is the "Simplest Solution" by Josh Pinter.

This worked for me:

//Code of the activity 
//get linearLayout
LinearLayout linearLayout = (LinearLayout ) view.findViewById(;       

LinearLayout linearLayout = new LinearLayout(getActivity());
//display css
RelativeLayout.LayoutParams params2 = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);

//create the spinner in a fragment activiy
Spinner spn = new Spinner(getActivity());

// create the adapter.
ArrayAdapter<ValorLista> spinner_adapter = new ArrayAdapter<ValorLista>(getActivity(), android.R.layout.simple_spinner_item, meta.getValorlistaList());

//set the default according to value

linearLayout.addView(spn, params2);
//Code of the class ValorLista

import java.util.List;

public class ValorLista implements Serializable{

    private static final long serialVersionUID = 4930195743192929192L;
    private int id; 
    private String valor;
    private List<Metadato> metadatoList;

    public ValorLista() {
        // TODO Auto-generated constructor stub

    public int getId() {
        return id;

    public void setId(int id) { = id;

    public String getValor() {
        return valor;
    public void setValor(String valor) {
        this.valor = valor;
    public List<Metadato> getMetadatoList() {
        return metadatoList;
    public void setMetadatoList(List<Metadato> metadatoList) {
        this.metadatoList = metadatoList;

    public String toString() {  
        return getValor();


How do I check if an element is hidden in jQuery?

You can do this:

isHidden = function(element){
    return ( === "none");

if(isHidden($("element")) == true){
    // Something

sqlplus how to find details of the currently connected database session

I know this is an old question but I did try all the above answers but didnt work in my case. What ultimately helped me out is

SHOW PARAMETER instance_name

How do I set a textbox's text to bold at run time?

 txtText.Font = new Font("Segoe UI", 8,FontStyle.Bold);
 //Font(Font Name,Font Size,Font.Style)

Adding options to a <select> using jQuery?

This did NOT work in IE8 (yet did in FF):

$("#selectList").append(new Option("option text", "value"));

This DID work:

var o = new Option("option text", "value");
/// jquerify the DOM object 'o' so we can use the html method
$(o).html("option text");

Set up DNS based URL forwarding in Amazon Route53


While my original answer below is still valid and might be helpful to understand the cause for DNS based URL forwarding not being available via Amazon Route 53 out of the box, I highly recommend checking out Vivek M. Chawla's utterly smart indirect solution via the meanwhile introduced Amazon S3 Support for Website Redirects and achieving a self contained server less and thus free solution within AWS only like so.

  • Implementing an automated solution to generate such redirects is left as an exercise for the reader, but please pay tribute to Vivek's epic answer by publishing your solution ;)

Original Answer

Nettica must be running a custom redirection solution for this, here is the problem:

You could create a CNAME alias like for, however, DNS provides no official support for aliasing a subdirectory like console in this example.

  • It's a pity that AWS doesn't appear to simply do this by default when hitting (I just tried), because it would solve you problem right away and make a lot of sense in the first place; besides, it should be pretty easy to configure on their end.

For that reason a few DNS providers have apparently implemented a custom solution to allow redirects to subdirectories; I venture the guess that they are basically facilitating a CNAME alias for a domain of their own and are redirecting again from there to the final destination via an immediate HTTP 3xx Redirection.

So to achieve the same result, you'd need to have a HTTP service running performing these redirects, which is not the simple solution one would hope for of course. Maybe/Hopefully someone can come up with a smarter approach still though.

How do I print the content of a .txt file in Python?

to input a file:

fin = open(filename) #filename should be a string type: e.g filename = 'file.txt'

to output this file you can do:

for element in fin:
    print element 

if the elements are a string you'd better add this before print:

element = element.strip()

strip() remove notations like this: /n

Build Maven Project Without Running Unit Tests

If you want to skip running and compiling tests:

mvn -Dmaven.test.skip=true install

If you want to compile but not run tests:

mvn install -DskipTests

How to insert an item into an array at a specific index (JavaScript)?

Another possible solution, with usage of Array#reduce.

const arr = ["apple", "orange", "raspberry"];
const arr2 = [1, 2, 4];

const insert = (arr, item, index) =>
  arr.reduce(function(s, a, i) {
    i === index ? s.push(item, a) : s.push(a);
    return s;
  }, []); 

console.log(insert(arr, "banana", 1));
console.log(insert(arr2, 3, 2))

Best way to add Gradle support to IntelliJ Project

Just as a future reference, if you already have a Maven project all you need to do is doing a gradle init in your project directory which will generates build.gradle and other dependencies, then do a gradle build in the same directory.

Rounded table corners CSS only

The best solution I've found for rounded corners and other CSS3 behavior for IE<9 can be found here:

Download the plug-in, copy to a directory in your solution structure. Then in your stylesheet make sure to have the behavior tag so that it pulls in the plug-in.

Simple example from my project which gives me rounded corners, color gradient, and box shadow for my table:

    -webkit-border-radius: 8px;
    -moz-border-radius: 8px;
    border-radius: 10px;
    -pie-background: linear-gradient(#ece9d8, #E5ECD8);   
    box-shadow: #666 0px 2px 3px;
    behavior: url(Include/;
    overflow: hidden;

Don't worry if your Visual Studio CSS intellisense gives you the green underline for unknown properites, it still works when you run it. Some of the elements are not very clearly documented, but the examples are pretty good, especially on the front page.

Setting default value for TypeScript object passed as argument

Without destructuring, you can create a defaults params and pass it in

interface Name {
   firstName: string;
   lastName: string;

export const defaultName extends Omit<Name, 'firstName'> {
    lastName: 'Smith'

sayName({ ...defaultName, firstName: 'Bob' })

Django set default form values

If you are creating modelform from POST values initial can be assigned this way:

form = SomeModelForm(request.POST, initial={"option": "10"})

How to get list of all installed packages along with version in composer?

Is there a way to get it via $event->getComposer()->getRepositoryManager()->getAllPackages()

Difference between /res and /assets directories

Both are pretty similar. The real main difference between the two is that in the res directory each file is given a pre-compiled ID which can be accessed easily through[res id]. This is useful to quickly and easily access images, sounds, icons...

The assets directory is more like a filesystem and provides more freedom to put any file you would like in there. You then can access each of the files in that system as you would when accessing any file in any file system through Java. This directory is good for things such as game details, dictionaries,...etc. Hope that helps.

How to set the matplotlib figure default size in ipython notebook?

I believe the following work in version 0.11 and above. To check the version:

$ ipython --version

It may be worth adding this information to your question.


You need to find the file Depending on your installation process this should be in somewhere like


where .config is in your home directory.

Once you have located this file find the following lines

# Subset of matplotlib rcParams that should be different for the inline backend.
# c.InlineBackend.rc = {'font.size': 10, 'figure.figsize': (6.0, 4.0), 'figure.facecolor': 'white', 'savefig.dpi': 72, 'figure.subplot.bottom': 0.125, 'figure.edgecolor': 'white'}

Uncomment this line c.InlineBack... and define your default figsize in the second dictionary entry.

Note that this could be done in a python script (and hence interactively in IPython) using

pylab.rcParams['figure.figsize'] = (10.0, 8.0)

How do I read the first line of a file using cat?

Adding one more obnoxious alternative to the list:

perl -pe'$.<=1||last' file
# or 
perl -pe'$.<=1||last' < file
# or
cat file | perl -pe'$.<=1||last'

Constructing pandas DataFrame from values in variables gives "ValueError: If using all scalar values, you must pass an index"

I had the same problem with numpy arrays and the solution is to flatten them:

data = {
    'b': array1.flatten(),
    'a': array2.flatten(),

df = pd.DataFrame(data)

C++ - How to append a char to char*?

Remove those char * ret declarations inside if blocks which hide outer ret. Therefor you have memory leak and on the other hand un-allocated memory for ret.

To compare a c-style string you should use strcmp(array,"") not array!="". Your final code should looks like below:

char* appendCharToCharArray(char* array, char a)
    size_t len = strlen(array);

    char* ret = new char[len+2];

    strcpy(ret, array);    
    ret[len] = a;
    ret[len+1] = '\0';

    return ret;

Note that, you must handle the allocated memory of returned ret somewhere by delete[] it.


Why you don't use std::string? it has .append method to append a character at the end of a string:

std::string str;

// or
str += x;

Query a parameter (postgresql.conf setting) like "max_connections"

You can use SHOW:

SHOW max_connections;

This returns the currently effective setting. Be aware that it can differ from the setting in postgresql.conf as there are a multiple ways to set run-time parameters in PostgreSQL. To reset the "original" setting from postgresql.conf in your current session:

RESET max_connections;

However, not applicable to this particular setting. The manual:

This parameter can only be set at server start.

To see all settings:


There is also pg_settings:

The view pg_settings provides access to run-time parameters of the server. It is essentially an alternative interface to the SHOW and SET commands. It also provides access to some facts about each parameter that are not directly available from SHOW, such as minimum and maximum values.

For your original request:

FROM   pg_settings
WHERE  name = 'max_connections';

Finally, there is current_setting(), which can be nested in DML statements:

SELECT current_setting('max_connections');


Printing one character at a time from a string, using the while loop

This will print each character in text

text = raw_input("Give some input:  ")
for i in range(0,len(text)):

Bootstrap modal appearing under background

I removed modal backdrop.

.modal-backdrop {

This is not better solution, but works for me.

True and False for && logic and || Logic table

I`d like to add to the already good answers:

The symbols '+', '*' and '-' are sometimes used as shorthand in some older textbooks for OR,? and AND,? and NOT,¬ logical operators in Bool`s algebra. In C/C++ of course we use "and","&&" and "or","||" and "not","!".

Watch out: "true + true" evaluates to 2 in C/C++ via internal representation of true and false as 1 and 0, and the implicit cast to int!

int main ()
  std::cout <<  "true - true = " << true - true << std::endl;
// This can be used as signum function:
// "(x > 0) - (x < 0)" evaluates to +1 or -1 for numbers.
  std::cout <<  "true - false = " << true - false << std::endl;
  std::cout <<  "false - true = " << false - true << std::endl;
  std::cout <<  "false - false = " << false - false << std::endl << std::endl;

  std::cout <<  "true + true = " << true + true << std::endl;
  std::cout <<  "true + false = " << true + false << std::endl;
  std::cout <<  "false + true = " << false + true << std::endl;
  std::cout <<  "false + false = " << false + false << std::endl << std::endl;

  std::cout <<  "true * true = " << true * true << std::endl;
  std::cout <<  "true * false = " << true * false << std::endl;
  std::cout <<  "false * true = " << false * true << std::endl;
  std::cout <<  "false * false = " << false * false << std::endl << std::endl;

  std::cout <<  "true / true = " << true / true << std::endl;
  //  std::cout <<  true / false << std::endl; ///-Wdiv-by-zero
  std::cout <<  "false / true = " << false / true << std::endl << std::endl;
  //  std::cout <<  false / false << std::endl << std::endl; ///-Wdiv-by-zero

  std::cout <<  "(true || true) = " << (true || true) << std::endl;
  std::cout <<  "(true || false) = " << (true || false) << std::endl;
  std::cout <<  "(false || true) = " << (false || true) << std::endl;
  std::cout <<  "(false || false) = " << (false || false) << std::endl << std::endl;

  std::cout <<  "(true && true) = " << (true && true) << std::endl;
  std::cout <<  "(true && false) = " << (true && false) << std::endl;
  std::cout <<  "(false && true) = " << (false && true) << std::endl;
  std::cout <<  "(false && false) = " << (false && false) << std::endl << std::endl;


yields :

true - true = 0
true - false = 1
false - true = -1
false - false = 0

true + true = 2
true + false = 1
false + true = 1
false + false = 0

true * true = 1
true * false = 0
false * true = 0
false * false = 0

true / true = 1
false / true = 0

(true || true) = 1
(true || false) = 1
(false || true) = 1
(false || false) = 0

(true && true) = 1
(true && false) = 0
(false && true) = 0
(false && false) = 0

Printf long long int in C with GCC?

If you are on windows and using mingw, gcc uses the win32 runtime, where printf needs %I64d for a 64 bit integer. (and %I64u for an unsinged 64 bit integer)

For most other platforms you'd use %lld for printing a long long. (and %llu if it's unsigned). This is standarized in C99.

gcc doesn't come with a full C runtime, it defers to the platform it's running on - so the general case is that you need to consult the documentation for your particular platform - independent of gcc.

How to make java delay for a few seconds?

 new Timer().schedule(new TimerTask() {
                public void run() {
                    if (getActivity() != null)
                        getActivity().runOnUiThread(() -> tvCovidAlert.startAnimation(animBounce));
            }, DELAY_TIME_MILI_SECONDS);

Git, fatal: The remote end hung up unexpectedly

I got this error when I had misspelt my remote branch name

Scala vs. Groovy vs. Clojure

Groovy is a dynamically typed language, whose syntax is very close to Java, with a number of syntax improvements that allow for lighter code and less boilerplate. It can run through an interpreter as well as being compiled, which makes it good for fast prototyping, scripts, and learning dynamic languages without having to learn a new syntax (assuming you know Java). As of Groovy 2.0, it also has growing support for static compilation. Groovy supports closures and has support for programming in a somewhat functional style, although it's still fairly far from the traditional definition of functional programming.

Clojure is a dialect of Lisp with a few advanced features like Software Transactional Memory. If you like Lisp and would like to use something like it under the JVM, Clojure is for you. It's possibly the most functional language running on the JVM, and certainly the most famous one. Also, it has a stronger emphasis on immutability than other Lisp dialects, which takes it closer to the heart of functional language enthusiasts.

Scala is a fully object oriented language, more so than Java, with one of the most advanced type systems available on non-research languages, and certainly the most advanced type system on the JVM. It also combines many concepts and features of functional languages, without compromising the object orientation, but its compromise on functional language characteristics put off some enthusiasts of the latter.

Groovy has good acceptance and a popular web framework in Grails. It also powers the Gradle build system, which is becoming a popular alternative to Maven. I personally think it is a language with limited utility, particularly as Jython and JRuby start making inroads on the JVM-land, compared to the others.

Clojure, even discounting some very interesting features, has a strong appeal just by being a Lisp dialect on JVM. It might limit its popularity, granted, but I expect it will have loyal community around it for a long time.

Scala can compete directly with Java, and give it a run for its money on almost all aspects. It can't compete in popularity at the moment, of course, and the lack of a strong corporate backing may hinder its acceptance on corporate environments. It's also a much more dynamic language than Java, in the sense of how the language evolves. From the perspective of the language, that's a good thing. From the perspective of users who plan on having thousands of lines of code written in it, not so.

As a final disclosure, I'm very familiar with Scala, and only acquainted with the other two.

What is a stored procedure?

"What is a stored procedure" is already answered in other posts here. What I will post is one less known way of using stored procedure. It is grouping stored procedures or numbering stored procedures.

Syntax Reference

enter image description here

; number as per this

An optional integer that is used to group procedures of the same name. These grouped procedures can be dropped together by using one DROP PROCEDURE statement


CREATE Procedure FirstTest 
    @InputA INT

CREATE Procedure FirstTest;2
    @InputA INT,
    @InputB INT


exec FirstTest 10
exec FirstTest;2 20,30


enter image description here

Another Attempt

CREATE Procedure SecondTest;2
     @InputA INT,
    @InputB INT


Msg 2730, Level 11, State 1, Procedure SecondTest, Line 1 [Batch Start Line 3] Cannot create procedure 'SecondTest' with a group number of 2 because a procedure with the same name and a group number of 1 does not currently exist in the database. Must execute CREATE PROCEDURE 'SecondTest';1 first.


  1. CREATE PROCEDURE with the syntax for number
  2. Numbered Stored Procedures in SQL Server -
  3. Grouping Stored Procedures - sqlmag


  1. After you group the procedures, you can't drop them individually.
  2. This feature may be removed in a future version of Microsoft SQL Server.

How to display two digits after decimal point in SQL Server

You can also Make use of the Following if you want to Cast and Round as well. That may help you or someone else.

SELECT CAST(ROUND(Column_Name, 2) AS DECIMAL(10,2), Name FROM Table_Name

NSString property: copy or retain?

Through this example copy and retain can be explained like:

NSMutableString *someName = [NSMutableString stringWithString:@"Chris"];

Person *p = [[[Person alloc] init] autorelease]; = someName;

[someName setString:@"Debajit"];

if the property is of type copy then ,

a new copy will be created for the [Person name] string that will hold the contents of someName string. Now any operation on someName string will have no effect on [Person name].

[Person name] and someName strings will have different memory addresses.

But in case of retain,

both the [Person name] will hold the same memory address as of somename string, just the retain count of somename string will be incremented by 1.

So any change in somename string will be reflected in [Person name] string.


It's true that some databases recognize the OUTER keyword. Some do not. Where it is recognized, it is usually an optional keyword. Almost always, FULL JOIN and FULL OUTER JOIN do exactly the same thing. (I can't think of an example where they do not. Can anyone else think of one?)

This may leave you wondering, "Why would it even be a keyword if it has no meaning?" The answer boils down to programming style.

In the old days, programmers strived to make their code as compact as possible. Every character meant longer processing time. We used 1, 2, and 3 letter variables. We used 2 digit years. We eliminated all unnecessary white space. Some people still program that way. It's not about processing time anymore. It's more about fast coding.

Modern programmers are learning to use more descriptive variables and put more remarks and documentation into their code. Using extra words like OUTER make sure that other people who read the code will have an easier time understanding it. There will be less ambiguity. This style is much more readable and kinder to the people in the future who will have to maintain that code.

Creating a dictionary from a CSV file

I'd suggest adding if rows in case there is an empty line at the end of the file

import csv
with open('coors.csv', mode='r') as infile:
    reader = csv.reader(infile)
    with open('coors_new.csv', mode='w') as outfile:
        writer = csv.writer(outfile)
        mydict = dict(row[:2] for row in reader if row)

Best way to create a temp table with same columns and type as a permanent table

This is a MySQL-specific answer, not sure where else it works --

You can create an empty table having the same column definitions with:


And you can create a populated copy of an existing table with:


And the following works in postgres; unfortunately the different RDBMS's don't seem very consistent here:


How to test a variable is null in python

You can do this in a try and catch block:

    if val is None:
except NameError:
    # throw an exception or do something else

How do you enable auto-complete functionality in Visual Studio C++ express edition?

Include the class that you are using Within your text file, then intelliSense will know where to look when you type within your text file. This works for me.

So it’s important to check the Unreal API to see where the included class is so that you have the path to type on the include line. Hope that makes sense.

Oracle - Why does the leading zero of a number disappear when converting it TO_CHAR

Seems like the only way to get decimal in a pretty (for me) form requires some ridiculous code.

The only solution I got so far:

CASE WHEN xy>0 and xy<1 then '0' || to_char(xy) else to_char(xy)

xy is a decimal.

xy             query result
0.8            0.8  --not sth like .80
10             10  --not sth like 10.00

How do I URL encode a string

Try to use stringByAddingPercentEncodingWithAllowedCharacters method with [NSCharacterSet URLUserAllowedCharacterSet] it will cover all the cases

Objective C

NSString *value = @"Test / Test";
value = [value stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLUserAllowedCharacterSet]];


var value = "Test / Test"



Extracting specific columns in numpy array

you can also use extractedData=data([:,1],[:,9])

How can I align the columns of tables in Bash?

printf is great, but people forget about it.

$ for num in 1 10 100 1000 10000 100000 1000000; do printf "%10s %s\n" $num "foobar"; done
         1 foobar
        10 foobar
       100 foobar
      1000 foobar
     10000 foobar
    100000 foobar
   1000000 foobar

$ for((i=0;i<array_size;i++));
    printf "%10s %10d %10s" stringarray[$i] numberarray[$i] anotherfieldarray[%i]

Notice I used %10s for strings. %s is the important part. It tells it to use a string. The 10 in the middle says how many columns it is to be. %d is for numerics (digits).

man 1 printf for more info.

Bind failed: Address already in use

You have a process that is already using that port. netstat -tulpn will enable one to find the process ID of that is using a particular port.

What is a "callable"?

In Python a callable is an object which type has a __call__ method:

>>> class Foo:
...  pass
>>> class Bar(object):
...  pass
>>> type(Foo).__call__(Foo)
<__main__.Foo instance at 0x711440>
>>> type(Bar).__call__(Bar)
<__main__.Bar object at 0x712110>
>>> def foo(bar):
...  return bar
>>> type(foo).__call__(foo, 42)

As simple as that :)

This of course can be overloaded:

>>> class Foo(object):
...  def __call__(self):
...   return 42
>>> f = Foo()
>>> f()

Convert HTML to NSAttributedString in iOS

Here is the Swift 5 version of Mobile Dan's answer:

public extension NSAttributedString {
    convenience init?(_ html: String) {
        guard let data = .unicode) else {
                return nil

        try? self.init(data: data, options: [.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil)

How to convert any Object to String?

If the class does not have toString() method, then you can use ToStringBuilder class from org.apache.commons:commons-lang3





What is the difference between baud rate and bit rate?

The bit rate is a measure of the number of bits that are transmitted per unit of time.

The baud rate, which is also known as symbol rate, measures the number of symbols that are transmitted per unit of time. A symbol typically consists of a fixed number of bits depending on what the symbol is defined as(for example 8bit or 9bit data). The baud rate is measured in symbols per second.

Take an example, where an ascii character 'R' is transmitted over a serial channel every one second.

The binary equivalent is 01010010.

So in this case, the baud rate is 1(one symbol transmitted per second) and the bit rate is 8 (eight bits are transmitted per second).

Maven does not find JUnit tests to run

Another thing that can cause Maven to not find the tests if if the module's packaging is not declared correctly.

In a recent case, someone had <packaging>pom</packaging> and my tests never ran. I changed it to <packaging>jar</packaging> and now it works fine.

How to silence output in a Bash script?

All output:

scriptname &>/dev/null


scriptname >/dev/null 2>&1


scriptname >/dev/null 2>/dev/null

For newer bash (no portable):

scriptname &>-

Could not load file or assembly 'xxx' or one of its dependencies. An attempt was made to load a program with an incorrect format

The BadImageFormatException on an application running on IIS (not running from VS, since visual studio fixes the problem by using the build for "Any CPU") can be caused by the following:

The site is one a server that is x64 and the Application Pool's default setting for Enable 32-Bit Applications was False. and you have 32-bit assemblies

On the level of Visual Studio, the fix is:

  1. Change the project setting "Target CPU" to "ANYCPU"

What is the proof of of (N–1) + (N–2) + (N–3) + ... + 1= N*(N–1)/2

Sum of arithmetical progression

(A1+AN)/2*N = (1 + (N-1))/2*(N-1) = N*(N-1)/2

How do I remove an object from an array with JavaScript?

If it's the last item in the array, you can do obj.pop()

Remove element by id

You can simply use


It works in all browsers, even on Internet Explorer.

Key Value Pair List

Using one of the subsets method in this question

var list = new List<KeyValuePair<string, int>>() { 
    new KeyValuePair<string, int>("A", 1),
    new KeyValuePair<string, int>("B", 0),
    new KeyValuePair<string, int>("C", 0),
    new KeyValuePair<string, int>("D", 2),
    new KeyValuePair<string, int>("E", 8),

int input = 11;
var items = SubSets(list).FirstOrDefault(x => x.Sum(y => y.Value)==input);


a full console application:

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApplication1
    class Program
        static void Main(string[] args)
            var list = new List<KeyValuePair<string, int>>() { 
                new KeyValuePair<string, int>("A", 1),
                new KeyValuePair<string, int>("B", 2),
                new KeyValuePair<string, int>("C", 3),
                new KeyValuePair<string, int>("D", 4),
                new KeyValuePair<string, int>("E", 5),
                new KeyValuePair<string, int>("F", 6),

            int input = 12;
            var alternatives = list.SubSets().Where(x => x.Sum(y => y.Value) == input);

            foreach (var res in alternatives)
                Console.WriteLine(String.Join(",", res.Select(x => x.Key)));

    public static class Extenions
        public static IEnumerable<IEnumerable<T>> SubSets<T>(this IEnumerable<T> enumerable)
            List<T> list = enumerable.ToList();
            ulong upper = (ulong)1 << list.Count;

            for (ulong i = 0; i < upper; i++)
                List<T> l = new List<T>(list.Count);
                for (int j = 0; j < sizeof(ulong) * 8; j++)
                    if (((ulong)1 << j) >= upper) break;

                    if (((i >> j) & 1) == 1)

                yield return l;

set gvim font in .vimrc file

I use the following (Uses Consolas size 11 on Windows, Menlo Regular size 14 on Mac OS X and Inconsolata size 12 everywhere else):

if has("gui_running")
  if has("gui_gtk2")
    set guifont=Inconsolata\ 12
  elseif has("gui_macvim")
    set guifont=Menlo\ Regular:h14
  elseif has("gui_win32")
    set guifont=Consolas:h11:cANSI

Edit: And while you're at it, you could take a look at Coding Horror's Programming Fonts blog post.

Edit²: Added MacVim.

How to prevent "The play() request was interrupted by a call to pause()" error?

Depending on how complex you want your solution, this may be useful:

var currentPromise=false;    //Keeps track of active Promise

function playAudio(n){
    if(!currentPromise){    //normal behavior
        n.currentTime = 0;
        currentPromise =;    //Calls play. Will store a Promise object in newer versions of chrome;
                                      //stores undefined in other browsers
        if(currentPromise){    //Promise exists
            currentPromise.then(function(){ //handle Promise completion
    }else{    //Wait for promise to complete
        //Store additional information to be called
        currentPromise.calledAgain = true;

function promiseComplete(n){
    var callAgain = currentPromise.calledAgain;    //get stored information
    currentPromise = false;    //reset currentPromise variable

This is a bit overkill, but helps when handling a Promise in unique scenarios.

Tkinter understanding mainloop

I'm using an MVC / MVA design pattern, with multiple types of "views". One type is a "GuiView", which is a Tk window. I pass a view reference to my window object which does things like link buttons back to view functions (which the adapter / controller class also calls).

In order to do that, the view object constructor needed to be completed prior to creating the window object. After creating and displaying the window, I wanted to do some initial tasks with the view automatically. At first I tried doing them post mainloop(), but that didn't work because mainloop() blocked!

As such, I created the window object and used tk.update() to draw it. Then, I kicked off my initial tasks, and finally started the mainloop.

import Tkinter as tk

class Window(tk.Frame):
    def __init__(self, master=None, view=None ):
        tk.Frame.__init__( self, master )
        self.view_ = view       
        """ Setup window linking it to the view... """

class GuiView( MyViewSuperClass ):

    def open( self ):
        self.tkRoot_ = tk.Tk()
        self.window_ = Window( master=None, view=self )

    def onOpen( self ):        
        """ Do some initial tasks... """

    def refresh( self ):        

How to find keys of a hash?

using jQuery you can get the keys like this:

var bobject =  {primary:"red",bg:"maroon",hilite:"green"};
var keys = [];
$.each(bobject, function(key,val){ keys.push(key); });
console.log(keys); // ["primary", "bg", "hilite"]


var bobject =  {primary:"red",bg:"maroon",hilite:"green"};
$.map(bobject, function(v,k){return k;});

thanks to @pimlottc

Servlet returns "HTTP Status 404 The requested resource (/servlet) is not available"

I removed the old web library such that are spring framework libraries. And build a new path of the libraries. Then it works.

how to make a div to wrap two float divs inside?

This should do it:

<div id="wrap">
  <div id="nav"></div>
  <div id="content"></div>
  <div style="clear:both"></div>

Visual Studio replace tab with 4 spaces?

For VS2010 and above (VS2010 needs a plugin). If you have checked/set the options of the tab size in Visual Studio but it still won't work. Then check if you have a .editorconfig file in your project! This will override the Visual Studio settings. Edit the tab-size in that file.

This can happen if you install an Angular application in your project with the Angular-Cli.

See MSDN blog

Control flow in T-SQL SP using IF..ELSE IF - are there other ways?

Also you can try to formulate your answer in the form of a SELECT CASE Statement. You can then later create simple if then's that use your results if needed as you have narrowed down the possibilities.

SELECT @Result =   
CASE @inputParam   
WHEN 1 THEN 1   
WHEN 2 THEN 2   
WHEN 3 THEN 1   
ELSE 4   

IF @Result = 1   

IF @Result = 2   

IF @Result = 4   
//Error handling code