Programs & Examples On #Drive letter

__init__() missing 1 required positional argument

Your constructor is expecting one parameter (data). You're not passing it in the call. I guess you wanted to initialise a field in the object. That would look like this:

class DHT:
    def __init__(self): = {}['one'] = '1'['two'] = '2'['three'] = '3'
    def showData(self):

if __name__ == '__main__':

Or even just:

class DHT:
    def __init__(self): = {'one': '1', 'two': '2', 'three': '3'}
    def showData(self):

When should I use GET or POST method? What's the difference between them?

You should use POST if there is a lot of data, or sort-of sensitive information (really sensitive stuff needs a secure connection as well).

Use GET if you want people to be able to bookmark your page, because all the data is included with the bookmark.

Just be careful of people hitting REFRESH with the GET method, because the data will be sent again every time without warning the user (POST sometimes warns the user about resending data).

How do you uninstall the package manager "pip", if installed from source?

I was using above command but it was not working. This command worked for me:

python -m pip uninstall pip setuptools

How to go to each directory and execute a command?

for folder_to_go in $(find . -mindepth 1 -maxdepth 1 -type d \( -name "*" \) ) ; 
                                    # you can add pattern insted of * , here it goes to any folder 
                                    #-mindepth / maxdepth 1 means one folder depth   
cd $folder_to_go
  echo $folder_to_go "########################################## "
  whatever you want to do is here

cd ../ # if maxdepth/mindepath = 2,  cd ../../

#you can try adding many internal for loops with many patterns, this will sneak anywhere you want

JAVA_HOME and PATH are set but java -version still shows the old one


The java executable is not found with your JAVA_HOME, it only depends on your PATH.

update-java-alternatives is a good way to manage it for the entire system is through:

update-java-alternatives -l

Sample output:

java-7-oracle 1 /usr/lib/jvm/java-7-oracle
java-8-oracle 2 /usr/lib/jvm/java-8-oracle

Choose one of the alternatives:

sudo update-java-alternatives -s java-7-oracle

Like update-alternatives, it works through symlink management. The advantage is that is manages symlinks to all the Java utilities at once: javac, java, javap, etc.

I am yet to see a JAVA_HOME effect on the JDK. So far, I have only seen it used in third-party tools, e.g. Maven.

plot data from CSV file with matplotlib

According to the docs numpy.loadtxt is

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

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

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

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

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

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

How to strip a specific word from a string?

A bit 'lazy' way to do this is to use startswith- it is easier to understand this rather regexps. However regexps might work faster, I haven't measured.

>>> papa = "papa is a good man"
>>> app = "app is important"
>>> strip_word = 'papa'
>>> papa[len(strip_word):] if papa.startswith(strip_word) else papa
' is a good man'
>>> app[len(strip_word):] if app.startswith(strip_word) else app
'app is important'

WCF Error "This could be due to the fact that the server certificate is not configured properly with HTTP.SYS in the HTTPS case"

I had this issue when running older XP SP3 boxes against both IIS and glassfish on Amazon AWS. Amazon changed their default load balancer settings to NOT enable the DES-CBC3-SHA cipher. You have to enable that on amazon ELB if you want to allow older XP TLS 1.0 to work against ELB for HTTPS otherwise you get this error. Ciphers can be changed on ELB by going to the listener tab in the console and clicking on cipher next to the particular listener you are trying to make work.

Assembly Language - How to do Modulo?

If you don't care too much about performance and want to use the straightforward way, you can use either DIV or IDIV.

DIV or IDIV takes only one operand where it divides a certain register with this operand, the operand can be register or memory location only.

When operand is a byte: AL = AL / operand, AH = remainder (modulus).


MOV AL,31h ; Al = 31h

DIV BL ; Al (quotient)= 08h, Ah(remainder)= 01h

when operand is a word: AX = (AX) / operand, DX = remainder (modulus).


MOV AX,9031h ; Ax = 9031h

DIV BX ; Ax=1808h & Dx(remainder)= 01h

SQL join: selecting the last records in a one-to-many relationship

If you're using PostgreSQL you can use DISTINCT ON to find the first row in a group.

SELECT customer.*, purchase.*
FROM customer
   SELECT DISTINCT ON (customer_id) *
   FROM purchase
   ORDER BY customer_id, date DESC
) purchase ON purchase.customer_id =

PostgreSQL Docs - Distinct On

Note that the DISTINCT ON field(s) -- here customer_id -- must match the left most field(s) in the ORDER BY clause.

Caveat: This is a nonstandard clause.

NSRange from Swift Range?

For me this works perfectly:

let font = UIFont.systemFont(ofSize: 12, weight: .medium)
let text = "text"
let attString = NSMutableAttributedString(string: "exemple text :)")

attString.addAttributes([.font: font], range:(attString.string as NSString).range(of: text))

label.attributedText = attString

How do I convert from int to String?

This technique was taught in an undergraduate level introduction-to-Java class I took over a decade ago. However, I should note that, IIRC, we hadn't yet gotten to the String and Integer class methods.

The technique is simple and quick to type. If all I'm doing is printing something, I'll use it (for example, System.out.println("" + i);. However, I think it's not the best way to do a conversion, as it takes a second of thought to realize what's going on when it's being used this way. Also, if performance is a concern, it seems slower (more below, as well as in other answers).

Personally, I prefer Integer.toString(), as it is obvious what's happening. String.valueOf() would be my second choice, as it seems to be confusing (witness the comments after darioo's answer).

Just for grins :) I wrote up classes to test the three techniques: "" + i, Integer.toString, and String.ValueOf. Each test just converted the ints from 1 to 10000 to Strings. I then ran each through the Linux time command five times. Integer.toString() was slightly faster than String.valueOf() once, they tied three times, and String.valueOf() was faster once; however, the difference was never more than a couple of milliseconds.

The "" + i technique was slower than both on every test except one, when it was 1 millisecond faster than Integer.toString() and 1 millisecond slower than String.valueOf() (obviously on the same test where String.valueOf() was faster than Integer.toString()). While it was usually only a couple milliseconds slower, there was one test where it was about 50 milliseconds slower. YMMV.

Java Swing - how to show a panel on top of another panel?

I think LayeredPane is your best bet here. You would need a third panel though to contain A and B. This third panel would be the layeredPane and then panel A and B could still have a nice LayoutManagers. All you would have to do is center B over A and there is quite a lot of examples in the Swing trail on how to do this. Tutorial for positioning without a LayoutManager.

public class Main {
    private JFrame frame = new JFrame();
    private JLayeredPane lpane = new JLayeredPane();
    private JPanel panelBlue = new JPanel();
    private JPanel panelGreen = new JPanel();
    public Main()
        frame.setPreferredSize(new Dimension(600, 400));
        frame.setLayout(new BorderLayout());
        frame.add(lpane, BorderLayout.CENTER);
        lpane.setBounds(0, 0, 600, 400);
        panelBlue.setBounds(0, 0, 600, 400);
        panelGreen.setBounds(200, 100, 100, 100);
        lpane.add(panelBlue, new Integer(0), 0);
        lpane.add(panelGreen, new Integer(1), 0);

     * @param args the command line arguments
    public static void main(String[] args) {
        new Main();


You use setBounds to position the panels inside the layered pane and also to set their sizes.

Edit to reflect changes to original post You will need to add component listeners that detect when the parent container is being resized and then dynamically change the bounds of panel A and B.

Best way to do Version Control for MS Excel

It depends whether you are talking about data, or the code contained within a spreadsheet. While I have a strong dislike of Microsoft's Visual Sourcesafe and normally would not recommended it, it does integrate easily with both Access and Excel, and provides source control of modules.

[In fact the integration with Access, includes queries, reports and modules as individual objects that can be versioned]

The MSDN link is here.

ggplot2: sorting a plot

I don't know why this question was reopened but here is a tidyverse option.

x %>% 
  arrange(desc(value)) %>%
  mutate(variable=fct_reorder(variable,value)) %>% 
ggplot(aes(variable,value,fill=variable)) + geom_bar(stat="identity") + 
  scale_y_continuous("",label=scales::percent) + coord_flip() 

How can I run PowerShell with the .NET 4 runtime?

If you don't want to modify the registry or app.config files, an alternate way is to create a simple .NET 4 console app that mimicks what PowerShell.exe does and hosts the PowerShell ConsoleShell.

See Option 2 – Hosting Windows PowerShell yourself

First, add a reference to the System.Management.Automation and Microsoft.PowerShell.ConsoleHost assemblies which can be found under %programfiles%\Reference Assemblies\Microsoft\WindowsPowerShell\v1.0

Then use the following code:

using System;
using System.Management.Automation.Runspaces;
using Microsoft.PowerShell;

namespace PSHostCLRv4
    class Program
        static int Main(string[] args)
            var config = RunspaceConfiguration.Create();
                return ConsoleShell.Start(
                "Windows PowerShell - Hosted on CLR v4\nCopyright (C) 2010 Microsoft Corporation. All rights reserved.",

Should I use != or <> for not equal in T-SQL?

Technically they function the same if you’re using SQL Server AKA T-SQL. If you're using it in stored procedures there is no performance reason to use one over the other. It then comes down to personal preference. I prefer to use <> as it is ANSI compliant.

You can find links to the various ANSI standards at...

Initialize a string variable in Python: "" or None?

empty_string = ""

if not empty_string:

    print "Empty string is not set"

=>Empty string is not set

if empty_string is not None:
    print "Empty string is not None"

=>Empty string is not None

Tensorflow: Using Adam optimizer

run init after AdamOptimizer,and without define init before or run init


websocket.send() parameter

As I understand it, you want the server be able to send messages through from client 1 to client 2. You cannot directly connect two clients because one of the two ends of a WebSocket connection needs to be a server.

This is some pseudocodish JavaScript:


var websocket = new WebSocket("server address");

websocket.onmessage = function(str) {
  console.log("Someone sent: ", str);

// Tell the server this is client 1 (swap for client 2 of course)
  id: "client1"

// Tell the server we want to send something to the other client
  to: "client2",
  data: "foo"


var clients = {};

server.on("data", function(client, str) {
  var obj = JSON.parse(str);

  if("id" in obj) {
    // New client, add it to the id/client object
    clients[] = client;
  } else {
    // Send data to the client requested

Tomcat 7 is not running on browser(http://localhost:8080/ )

You may face two errors while testing tomcat server startup.

  1. Error in the Eclipse inbuilt browser - This page can’t be displayed Turn on TLS 1.0, TLS 1.1, and TLS 1.2 in Advanced settings and try connecting to https://localhost:8080 again. If this error persists, it is possible that this site uses an unsupported protocol. Please contact the site administrator.
  2. 404 error in the normal browsers.

Fixes -

  1. For the eclipse browser error, check whether you are using secured URL - https://localhost:8080. This should be http://localhost:8080
  2. For the 404 error: Go to Tomcat server in the console. Do a right click, select properties. In the properties window, Click "Switch location" and then click OK. Followed by that, Go to Tomcat server in the console, double click it, Under "server locations" select "Use Tomcat installation" radio button. Save it.

The reason for choosing this option is, When the default option is given as eclipse location, we will see 404 error as it changes Catalina parameters (sometimes). But if we change it to Tomcat location, it works fine.

Git: add vs push vs commit

  • git add adds files to the Git index, which is a staging area for objects prepared to be commited.
  • git commit commits the files in the index to the repository, git commit -a is a shortcut to add all the modified tracked files to the index first.
  • git push sends all the pending changes to the remote repository to which your branch is mapped (eg. on GitHub).

In order to understand Git you would need to invest more effort than just glancing over the documentation, but it's definitely worth it. Just don't try to map Git commands directly to Subversion, as most of them don't have a direct counterpart.

How is Docker different from a virtual machine?

There are many answers which explain more detailed on the differences, but here is my very brief explanation.

One important difference is that VMs use a separate kernel to run the OS. That's the reason it is heavy and takes time to boot, consuming more system resources.

In Docker, the containers share the kernel with the host; hence it is lightweight and can start and stop quickly.

In Virtualization, the resources are allocated in the beginning of set up and hence the resources are not fully utilized when the virtual machine is idle during many of the times. In Docker, the containers are not allocated with fixed amount of hardware resources and is free to use the resources depending on the requirements and hence it is highly scalable.

Docker uses UNION File system .. Docker uses a copy-on-write technology to reduce the memory space consumed by containers. Read more here

Could not connect to React Native development server on Android

After trying all the most upvoted answers and failing to make it work, I figured that my Android Simulator was on Airplane mode. Quite silly but posting this so it could save some time.

P.S. I had a safe reboot on my Simulator before this, which is probably the cause why my simulator booted in Airplane mode

Getting String Value from Json Object Android

You just need to get the JSONArray and iterate the JSONObject inside the Array using a loop though in your case its only one JSONObject but you may have more.

JSONArray mArray;
        try {
            mArray = new JSONArray(responseString);
             for (int i = 0; i < mArray.length(); i++) {
                    JSONObject mJsonObject = mArray.getJSONObject(i);
                    Log.d("OutPut", mJsonObject.getString("NeededString"));
        } catch (JSONException e) {

How can I plot a confusion matrix?

enter image description here

you can use plt.matshow() instead of plt.imshow() or you can use seaborn module's heatmap (see documentation) to plot the confusion matrix

import seaborn as sn
import pandas as pd
import matplotlib.pyplot as plt
array = [[33,2,0,0,0,0,0,0,0,1,3], 
df_cm = pd.DataFrame(array, index = [i for i in "ABCDEFGHIJK"],
                  columns = [i for i in "ABCDEFGHIJK"])
plt.figure(figsize = (10,7))
sn.heatmap(df_cm, annot=True)

sed edit file in place

Like Moneypenny said in Skyfall: "Sometimes the old ways are best." Kincade said something similar later on.

$ printf ',s/false/true/g\nw\n' | ed {YourFileHere}

Happy editing in place. Added '\nw\n' to write the file. Apologies for delay answering request.

Check if number is decimal

$lat = '-25.3654';

if(preg_match('/./',$lat)) {
    echo "\nYes its a decimal value\n";
    echo 'No its not a decimal value';

Explanation of <script type = "text/template"> ... </script>

Those script tags are a common way to implement templating functionality (like in PHP) but on the client side.

By setting the type to "text/template", it's not a script that the browser can understand, and so the browser will simply ignore it. This allows you to put anything in there, which can then be extracted later and used by a templating library to generate HTML snippets.

Backbone doesn't force you to use any particular templating library - there are quite a few out there: Mustache, Haml, Eco,Google Closure template, and so on (the one used in the example you linked to is underscore.js). These will use their own syntax for you to write within those script tags.

How to change the color of a button?

You can change the colour two ways; through XML or through coding. I would recommend XML since it's easier to follow for beginners.



You can also use hex values ex.



//btn represents your button object


Can you recommend a free light-weight MySQL GUI for Linux?

Try Adminer. The whole application is in one PHP file, which means that the deployment is as easy as it can get. It's more powerful than phpMyAdmin; it can edit views, procedures, triggers, etc.

Adminer is also a universal tool, it can connect to MySQL, PostgreSQL, SQLite, MS SQL, Oracle, SimpleDB, Elasticsearch and MongoDB.

You should definitely give it a try.

enter image description here

You can install on Ubuntu with sudo apt-get install adminer or you can also download the latest version from

Encoding an image file with base64

The first answer will print a string with prefix b'. That means your string will be like this b'your_string' To solve this issue please add the following line of code.

encoded_string= base64.b64encode(

How to display activity indicator in middle of the iphone screen?

For Swift 3 you can use the following:

 func setupSpinner(){
    spinner = UIActivityIndicatorView(frame: CGRect(x: 0, y: 0, width: 40, height:40))
    spinner.color = UIColor(Colors.Accent) = CGPoint(x:UIScreen.main.bounds.size.width / 2, y:UIScreen.main.bounds.size.height / 2)
    spinner.hidesWhenStopped = true

How to sort a HashSet?

Use java.util.TreeSet as the actual object. When you iterate over this collection, the values come back in a well-defined order.

If you use java.util.HashSet then the order depends on an internal hash function which is almost certainly not lexicographic (based on content).

Random alpha-numeric string in JavaScript?

When I saw this question I thought of when I had to generate UUIDs. I can't take credit for the code, as I am sure I found it here on stackoverflow. If you dont want the dashes in your string then take out the dashes. Here is the function:

function generateUUID() {
    var d = new Date().getTime();
    var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g,function(c) {
        var r = (d + Math.random()*16)%16 | 0;
        d = Math.floor(d/16);
        return (c=='x' ? r : (r&0x7|0x8)).toString(16);
    return uuid.toUpperCase();


Split Div Into 2 Columns Using CSS

For whatever reason I've never liked the clearing approaches, I rely on floats and percentage widths for things like this.

Here's something that works in simple cases:

#content { 
  width: 600px; 
  background: gray; 

#left, #right { 
  width: 40%; 
  padding: 1em; 
  background: white; 

#left  { float:left;  }
#right { float:right; } 

If you put some content in you'll see that it works:

<div id="content">
  <div id="left">
     <div id="object1">some stuff</div>
     <div id="object2">some more stuff</div>

  <div id="right">
     <div id="object3">unas cosas</div>
     <div id="object4">mas cosas para ti</div>

You can see it here:

Can you call Directory.GetFiles() with multiple filters?

I wonder why there are so many "solutions" posted?

If my rookie-understanding on how GetFiles works is right, there are only two options and any of the solutions above can be brought down to these:

  1. GetFiles, then filter: Fast, but a memory killer due to storing overhead untill the filters are applied

  2. Filter while GetFiles: Slower the more filters are set, but low memory usage as no overhead is stored.
    This is explained in one of the above posts with an impressive benchmark: Each filter option causes a seperate GetFile-operation so the same part of the harddrive gets read several times.

In my opinion Option 1) is better, but using the SearchOption.AllDirectories on folders like C:\ would use huge amounts of memory.
Therefor i would just make a recursive sub-method that goes through all subfolders using option 1)

This should cause only 1 GetFiles-operation on each folder and therefor be fast (Option 1), but use only a small amount of memory as the filters are applied afters each subfolders' reading -> overhead is deleted after each subfolder.

Please correct me if I am wrong. I am as i said quite new to programming but want to gain deeper understanding of things to eventually become good at this :)

How can I get new selection in "select" in Angular 2?

In Angular 5 I did with the following way. get the object $event.value instead of $

<mat-form-field color="warn">
   <mat-select (ngModelChange)="onChangeTown($event)" class="form-width" formControlName="branch" [(ngModel)]="branch" placeholder="Enter branch">
     <mat-option *ngFor="let branch of branchs" [value]="branch.value">
                  {{ }}

onChangeTown(event): void {
  const selectedTown = event;
  console.log('selectedTown: ', selectedTown);

How do I delete all messages from a single queue using the CLI?

RabbitMQ implements the Advanced Message Queuing Protocol (AMQP) so you can use generic tools for stuff like this.

On Debian/Ubuntu or similar system, do:

sudo apt-get install amqp-tools
amqp-delete-queue -q celery  # where celery is the name of the queue to delete

Succeeded installing but could not start apache 2.4 on my windows 7 system

Sorry for the belabored question. To solve my problem I just told apache 2.4 to listen to a different port in httpd.conf. Since System was using pid 4 which was listening on port 80, I did not want to explore this any further.

I put the following into httpd.conf. Listen

Using CookieContainer with WebClient class

Yes. IMHO, overriding GetWebRequest() is the best solution to WebClient's limited functionalty. Before I knew about this option, I wrote lots of really painful code at the HttpWebRequest layer because WebClient almost, but not quite, did what I needed. Derivation is much easier.

Another option is to use the regular WebClient class, but manually populate the Cookie header before making the request and then pull out the Set-Cookies header on the response. There are helper methods on the CookieContainer class which make creating and parsing these headers easier: CookieContainer.SetCookies() and CookieContainer.GetCookieHeader(), respectively.

I prefer the former approach since it's easier for the caller and requires less repetitive code than the second option. Also, the derivation approach works the same way for multiple extensibility scenarios (e.g. cookies, proxies, etc.).

Error when trying to access XAMPP from a network

This answer is for XAMPP on Ubuntu.

The manual for installation and download is on (site official)

After to start XAMPP simply call this command:

sudo /opt/lampp/lampp start

You should now see something like this on your screen:

Starting XAMPP 1.8.1...
LAMPP: Starting Apache...
LAMPP: Starting MySQL...
LAMPP started.

If you have this

Starting XAMPP for Linux 1.8.1...                                                             
XAMPP: Another web server daemon is already running.                                          
XAMPP: Another MySQL daemon is already running.                                               
XAMPP: Starting ProFTPD...                                                                    
XAMPP for Linux started

. The solution is

sudo /etc/init.d/apache2 stop
sudo /etc/init.d/mysql stop

And the restast with sudo //opt/lampp/lampp restart

You to fix most of the security weaknesses simply call the following command:

/opt/lampp/lampp security

After the change this file

sudo kate //opt/lampp/etc/extra/httpd-xampp.conf

Find and replace on

# New XAMPP security concept
<LocationMatch "^/(?i:(?:xampp|security|licenses|phpmyadmin|webalizer|server-status|server-info))">
    Order deny,allow
    Deny from all
    Allow from ::1 
    Allow from all
    #   fc00::/7 \
    #   fe80::/10

    ErrorDocument 403 /error/XAMPP_FORBIDDEN.html.var

What is the difference between "Rollback..." and "Back Out Submitted Changelist #####" in Perforce P4V

Backout restores or undoes our changes. The way it does this is that, P4 undoes the changes in a changelist (default or new) on our local workspace. We then have to submit/commit this backedout changelist as we do other changeslists. The second part is important here, as it doesn't automatically backout the changelist on the server, we have to submit the backedout changelist (which makes sense after you do it, but i was initially assuming it does that automatically).

As pointed by others, Rollback has greater powers - It can restore changes to a specific date, changelist or a revision#

Which browsers support <script async="async" />?

The async is currently supported by all latest versions of the major browsers. It has been supported for some years now on most browsers.

You can keep track of which browsers support async (and defer) in the MDN website here:

If statement for strings in python?

You want:

answer = str(raw_input("Is the information correct? Enter Y for yes or N for no"))
if answer == "y" or answer == "Y":
  print("this will do the calculation")


answer = str(raw_input("Is the information correct? Enter Y for yes or N for no"))
if answer in ["y","Y"]:
  print("this will do the calculation")


  1. It's "if", not "If". Python is case sensitive.
  2. Indentation is important.
  3. There is no colon or semi-colon at the end of python commands.
  4. You want raw_input not input; input evals the input.
  5. "or" gives you the first result if it evaluates to true, and the second result otherwise. So "a" or "b" evaluates to "a", whereas 0 or "b" evaluates to "b". See The Peculiar Nature of and and or.

How do I make the method return type generic?

You could define callFriend this way:

public <T extends Animal> T callFriend(String name, Class<T> type) {
    return type.cast(friends.get(name));

Then call it as such:

jerry.callFriend("spike", Dog.class).bark();
jerry.callFriend("quacker", Duck.class).quack();

This code has the benefit of not generating any compiler warnings. Of course this is really just an updated version of casting from the pre-generic days and doesn't add any additional safety.

What is Express.js?

  1. Express.js is a modular web framework for Node.js
  2. It is used for easier creation of web applications and services
  3. Express.js simplifies development and makes it easier to write secure, modular and fast applications. You can do all that in plain old Node.js, but some bugs can (and will) surface, including security concerns (eg. not escaping a string properly)
  4. Redis is an in-memory database system known for its fast performance. No, but you can use it with Express.js using a redis client

I couldn't be more concise than this. For all your other needs and information, Google is your friend.

Is it possible to set a timeout for an SQL query on Microsoft SQL server?

If you have just one query I don't know how to set timeout on T-SQL level.

However if you have a few queries (i.e. collecting data into temporary tables) inside stored procedure you can just control time of execution with GETDATE(), DATEDIFF() and a few INT variables storing time of execution of each part.

Conversion hex string into ascii in bash command line

You can use xxd:

$cat hex.txt
68 65 6c 6c 6f
$cat hex.txt | xxd -r -p

Python list of dictionaries search

You have to go through all elements of the list. There is not a shortcut!

Unless somewhere else you keep a dictionary of the names pointing to the items of the list, but then you have to take care of the consequences of popping an element from your list.

get user timezone

This will get you the timezone as a PHP variable. I wrote a function using jQuery and PHP. This is tested, and does work!

On the PHP page where you are want to have the timezone as a variable, have this snippet of code somewhere near the top of the page:

    $timezone = $_SESSION['time'];

This will read the session variable "time", which we are now about to create.

On the same page, in the <head> section, first of all you need to include jQuery:

<script type="text/javascript" src=""></script>

Also in the <head> section, paste this jQuery:

<script type="text/javascript">
    $(document).ready(function() {
        if("<?php echo $timezone; ?>".length==0){
            var visitortime = new Date();
            var visitortimezone = "GMT " + -visitortime.getTimezoneOffset()/60;
                type: "GET",
                url: "",
                data: 'time='+ visitortimezone,
                success: function(){

You may or may not have noticed, but you need to change the url to your actual domain.

One last thing. You are probably wondering what the heck timezone.php is. Well, it is simply this: (create a new file called timezone.php and point to it with the above url)

    $_SESSION['time'] = $_GET['time'];

If this works correctly, it will first load the page, execute the JavaScript, and reload the page. You will then be able to read the $timezone variable and use it to your pleasure! It returns the current UTC/GMT time zone offset (GMT -7) or whatever timezone you are in.

You can read more about this on my blog

How to synchronize or lock upon variables in Java?

Use the synchronized keyword.

class sample {
    private String msg=null;

    public synchronized void newmsg(String x){

    public synchronized string getmsg(){
        String temp=msg;
        return msg;

Using the synchronized keyword on the methods will require threads to obtain a lock on the instance of sample. Thus, if any one thread is in newmsg(), no other thread will be able to get a lock on the instance of sample, even if it were trying to invoke getmsg().

On the other hand, using synchronized methods can become a bottleneck if your methods perform long-running operations - all threads, even if they want to invoke other methods in that object that could be interleaved, will still have to wait.

IMO, in your simple example, it's ok to use synchronized methods since you actually have two methods that should not be interleaved. However, under different circumstances, it might make more sense to have a lock object to synchronize on, as shown in Joh Skeet's answer.

Is there a Google Chrome-only CSS hack?

You could use javascript. The other answers to date seem to also target Safari.

if (navigator.userAgent.toLowerCase().indexOf('chrome') > -1) {
    alert("You'll only see this in Chrome");
    $('#someID').css('background-position', '10px 20px');

Is there an opposite to display:none?

The best "opposite" would be to return it to the default value which is:

display: inline

how to put image in a bundle and pass it to another activity

So you can do it like this, but the limitation with the Parcelables is that the payload between activities has to be less than 1MB total. It's usually better to save the Bitmap to a file and pass the URI to the image to the next activity.

 protected void onCreate(Bundle savedInstanceState) {     setContentView(R.layout.my_layout);     Bitmap bitmap = getIntent().getParcelableExtra("image");     ImageView imageView = (ImageView) findViewById(;     imageView.setImageBitmap(bitmap);  } 

How does #include <bits/stdc++.h> work in C++?

Unfortunately that approach is not portable C++ (so far).

All standard names are in namespace std and moreover you cannot know which names are NOT defined by including and header (in other words it's perfectly legal for an implementation to declare the name std::string directly or indirectly when using #include <vector>).

Despite this however you are required by the language to know and tell the compiler which standard header includes which part of the standard library. This is a source of portability bugs because if you forget for example #include <map> but use std::map it's possible that the program compiles anyway silently and without warnings on a specific version of a specific compiler, and you may get errors only later when porting to another compiler or version.

In my opinion there are no valid technical excuses because this is necessary for the general user: the compiler binary could have all standard namespace built in and this could actually increase the performance even more than precompiled headers (e.g. using perfect hashing for lookups, removing standard headers parsing or loading/demarshalling and so on).

The use of standard headers simplifies the life of who builds compilers or standard libraries and that's all. It's not something to help users.

However this is the way the language is defined and you need to know which header defines which names so plan for some extra neurons to be burnt in pointless configurations to remember that (or try to find and IDE that automatically adds the standard headers you use and removes the ones you don't... a reasonable alternative).

How to to send mail using gmail in Laravel?

Working for me after trying various combinations.

[email protected]

It is necessary to generate application password and us it as MAIL_PASSWORD environment variable.

I found about about this by checking error code from google server, which was use-full and lead me to this webpage.

Colouring plot by factor in R

plot(data$Sepal.Length, data$Sepal.Width, col=data$Species)

should do it for you. But I prefer ggplot2 and would suggest that for better graphics in R.

Dynamically update values of a chartjs chart

You can check instance of Chart by using Chart.instances. This will give you all the charts instances. Now you can iterate on that instances and and change the data, which is present inside config. suppose you have only one chart in your page.

for (var _chartjsindex in Chart.instances) {
 * Here in the config your actual data and options which you have given at the 
   time of creating chart so no need for changing option only you can change data
 Chart.instances[_chartjsindex] = [];
 // here you can give add your data
 // update will rewrite your whole chart with new value

What's the best practice to round a float to 2 decimals?

Let's test 3 methods:

public static double round1(double value, int scale) {
    return Math.round(value * Math.pow(10, scale)) / Math.pow(10, scale);


public static float round2(float number, int scale) {
    int pow = 10;
    for (int i = 1; i < scale; i++)
        pow *= 10;
    float tmp = number * pow;
    return ( (float) ( (int) ((tmp - (int) tmp) >= 0.5f ? tmp + 1 : tmp) ) ) / pow;


public static float round3(float d, int decimalPlace) {
    return BigDecimal.valueOf(d).setScale(decimalPlace, BigDecimal.ROUND_HALF_UP).floatValue();

Number is 0.23453f
We'll test 100,000 iterations each method.

Time 1 - 18 ms
Time 2 - 1 ms
Time 3 - 378 ms

Tested on laptop
Intel i3-3310M CPU 2.4GHz

Create hive table using "as select" or "like" and also specify delimiter

Both the answers provided above work fine.

  1. CREATE TABLE person AS select * from employee;
  2. CREATE TABLE person LIKE employee;

How to check if an app is installed from a web-page on an iPhone?

As of 2017, it seems there's no reliable way to detect an app is installed, and the redirection trick won't work everywhere.

For those like me who needs to deep link directly from emails (quite common), it is worth noting the following:

  • Sending emails with appScheme:// won't work fine because the links will be filtered in Gmail

  • Redirecting automatically to appScheme:// is blocked by Chrome: I suspect Chrome requires the redirection to be synchronous to an user interaction (like a click)

  • You can now deep link without appScheme:// and it's better but it requires a modern platform and additional setup. Android iOS

It is worth noting that other people already thought about this in depth. If you look at how Slack implements his "magic link" feature, you can notice that:

  • It sends an email with a regular http link (ok with Gmail)
  • The web page have a big button that links to appScheme:// (ok with Chrome)

How to Change Margin of TextView

        TextView tv = (TextView)findViewById(;
        RelativeLayout.LayoutParams mRelativelp = (RelativeLayout.LayoutParams) tv
        mRelativelp.setMargins(DptoPxConvertion(15), 0, DptoPxConvertion (15), 0);

    private int DptoPxConvertion(int dpValue)
       return (int)((dpValue * mContext.getResources().getDisplayMetrics().density) + 0.5);

getLayoutParams() of textview should be casted to the corresponding Params based on the Parent of the textview in xml.


To render the same real size on different devices use DptoPxConvertion() method which I have used above. setMargin(left,top,right,bottom) params will take values in pixel not in dp. For further reference see this Link Answer

The data-toggle attributes in Twitter Bootstrap

The presence of this data-attribute tells Bootstrap to switch between visual or a logical states of another element on user interaction.

It is used to show modals, tab content, tooltips and popover menus as well as setting a pressed-state for a toggle-button. It is used in multiple ways without a clear documentation.

Trigger a keypress/keydown/keyup event in JS/jQuery?

You can trigger any of the events with a direct call to them, like this:

$(function() {

Does that do what you're trying to do?

You should probably also trigger .focus() and potentially .change()

If you want to trigger the key-events with specific keys, you can do so like this:

$(function() {
    var e = $.Event('keypress');
    e.which = 65; // Character 'A'

There is some interesting discussion of the keypress events here: jQuery Event Keypress: Which key was pressed?, specifically regarding cross-browser compatability with the .which property.

How to convert string to Date in Angular2 \ Typescript?

You can use date filter to convert in date and display in specific format.

In .ts file (typescript):

let dateString = '1968-11-16T00:00:00' 
let newDate = new Date(dateString);


{{dateString |  date:'MM/dd/yyyy'}}

Below are some formats which you can implement :


public todayDate = new Date();


<option value=""></option>
<option value="MM/dd/yyyy">[{{todayDate | date:'MM/dd/yyyy'}}]</option>
<option value="EEEE, MMMM d, yyyy">[{{todayDate | date:'EEEE, MMMM d, yyyy'}}]</option>
<option value="EEEE, MMMM d, yyyy h:mm a">[{{todayDate | date:'EEEE, MMMM d, yyyy h:mm a'}}]</option>
<option value="EEEE, MMMM d, yyyy h:mm:ss a">[{{todayDate | date:'EEEE, MMMM d, yyyy h:mm:ss a'}}]</option>
<option value="MM/dd/yyyy h:mm a">[{{todayDate | date:'MM/dd/yyyy h:mm a'}}]</option>
<option value="MM/dd/yyyy h:mm:ss a">[{{todayDate | date:'MM/dd/yyyy h:mm:ss a'}}]</option>
<option value="MMMM d">[{{todayDate | date:'MMMM d'}}]</option>   
<option value="yyyy-MM-ddTHH:mm:ss">[{{todayDate | date:'yyyy-MM-ddTHH:mm:ss'}}]</option>
<option value="h:mm a">[{{todayDate | date:'h:mm a'}}]</option>
<option value="h:mm:ss a">[{{todayDate | date:'h:mm:ss a'}}]</option>      
<option value="EEEE, MMMM d, yyyy hh:mm:ss a">[{{todayDate | date:'EEEE, MMMM d, yyyy hh:mm:ss a'}}]</option>
<option value="MMMM yyyy">[{{todayDate | date:'MMMM yyyy'}}]</option> 

What is the difference between server side cookie and client side cookie?

You probably mean the difference between Http Only cookies and their counter part?

Http Only cookies cannot be accessed (read from or written to) in client side JavaScript, only server side. If the Http Only flag is not set, or the cookie is created in (client side) JavaScript, the cookie can be read from and written to in (client side) JavaScript as well as server side.

Tkinter: How to use threads to preventing main event loop from "freezing"

When you join the new thread in the main thread, it will wait until the thread finishes, so the GUI will block even though you are using multithreading.

If you want to place the logic portion in a different class, you can subclass Thread directly, and then start a new object of this class when you press the button. The constructor of this subclass of Thread can receive a Queue object and then you will be able to communicate it with the GUI part. So my suggestion is:

  1. Create a Queue object in the main thread
  2. Create a new thread with access to that queue
  3. Check periodically the queue in the main thread

Then you have to solve the problem of what happens if the user clicks two times the same button (it will spawn a new thread with each click), but you can fix it by disabling the start button and enabling it again after you call self.prog_bar.stop().

import Queue

class GUI:
    # ...

    def tb_click(self):
        self.queue = Queue.Queue()
        self.master.after(100, self.process_queue)

    def process_queue(self):
            msg = self.queue.get(0)
            # Show result of the task if needed
        except Queue.Empty:
            self.master.after(100, self.process_queue)

class ThreadedTask(threading.Thread):
    def __init__(self, queue):
        self.queue = queue
    def run(self):
        time.sleep(5)  # Simulate long running process
        self.queue.put("Task finished")

Unit testing with mockito for constructors

I believe, it is not possible to mock constructors using mockito. Instead, I suggest following approach

Class First {

   private Second second;

   public First(int num, String str) {
     if(second== null)
       //when junit runs, you get the mocked object(not null), hence don't 
       second = new Second(str);
     this.num = num;

   ... // some other methods

And, for test:

class TestFirst{
    First first;//inject mock the real testable class
    Second second


        //now you can play around with any method of the Second class using its 
        //mocked object(second),like:


WHERE clause introduces a condition on individual rows; HAVING clause introduces a condition on aggregations, i.e. results of selection where a single result, such as count, average, min, max, or sum, has been produced from multiple rows. Your query calls for a second kind of condition (i.e. a condition on an aggregation) hence HAVING works correctly.

As a rule of thumb, use WHERE before GROUP BY and HAVING after GROUP BY. It is a rather primitive rule, but it is useful in more than 90% of the cases.

While you're at it, you may want to re-write your query using ANSI version of the join:

SELECT  L.LectID, Fname, Lname
FROM Lecturers L
JOIN Lecturers_Specialization S ON L.LectID=S.LectID
GROUP BY L.LectID, Fname, Lname
(SELECT COUNT(Expertise) FROM Lecturers_Specialization GROUP BY LectID)

This would eliminate WHERE that was used as a theta join condition.

How to fix Subversion lock error

I have faced same problem. I solved this by Right click on project --->Team----> Refresh/cleanup

Build a simple HTTP server in C

Look at nweb (Nigel's Web Server), "a tiny, safe web server [...] with only 200 lines of C source code":

The article includes pseudocode, explanations, and comments.

EDIT: IBM's link has died. I have saved a PDF of the webpage to Google Drive. Here is the code download:

@ankushagarwal has made a few changes and uploaded his version on GitHub:

Is String.Contains() faster than String.IndexOf()?

Probably, it will not matter at all. Read this post on Coding Horror ;):

Add line break to ::after or ::before pseudo-element content

Nice article explaining the basics (does not cover line breaks, however).

A Whole Bunch of Amazing Stuff Pseudo Elements Can Do

If you need to have two inline elements where one breaks into the next line within another element, you can accomplish this by adding a pseudo-element :after with content:'\A' and white-space: pre


    <span class="label">This is the main label</span>
    <span class="secondary-label">secondary label</span>


.label:after {
    content: '\A';
    white-space: pre;

How to upsert (update or insert) in SQL Server 2005

Try to check for existence:


    INSERT INTO dbo.Employee(Col1, ..., ColN)
    VALUES(Val1, .., ValN)


    UPDATE dbo.Employee
    SET Col1 = Val1, Col2 = Val2, ...., ColN = ValN
    WHERE ID = @SomeID

You could easily wrap this into a stored procedure and just call that stored procedure from the outside (e.g. from a programming language like C# or whatever you're using).

Update: either you can just write this entire statement in one long string (doable - but not really very useful) - or you can wrap it into a stored procedure:

CREATE PROCEDURE dbo.InsertOrUpdateEmployee
       @ID INT,
       @Name VARCHAR(50),
       @ItemName VARCHAR(50),  
       @ItemCatName VARCHAR(50),
       @ItemQty DECIMAL(15,2)
       INSERT INTO dbo.Table1(ID, Name, ItemName, ItemCatName, ItemQty)
       VALUES(@ID, @Name, @ItemName, @ItemCatName, @ItemQty)
       UPDATE dbo.Table1
       SET Name = @Name,
           ItemName = @ItemName,
           ItemCatName = @ItemCatName,
           ItemQty = @ItemQty
       WHERE ID = @ID

and then just call that stored procedure from your ADO.NET code

How to align checkboxes and their labels consistently cross-browsers

Maybe some folk are making the same mistake I did? Which was... I had set a width for the input boxes, because they were mostly of type 'text' , but then forgotten to over-ride that width for checkboxes - so my checkbox was trying to occupy a lot of excess width and so it was tough to align a label beside it.

.checkboxlabel {
    width: 100%;
    vertical-align: middle;
.checkbox {
    width: 20px !important;
<label for='acheckbox' class='checkboxlabel'>
    <input name="acheckbox" id='acheckbox' type="checkbox" class='checkbox'>Contact me</label>

Gives clickable labels and and proper alignment as far back as IE6 (using a class selector) and in late versions of Firefox, Safari and Chrome

How do I trim a file extension from a String in Java?

The best what I can write trying to stick to the Path class:

Path removeExtension(Path path) {
    return path.resolveSibling(path.getFileName().toString().replaceFirst("\\.[^.]*$", ""));

How do I make JavaScript beep?

It's not possible to do directly in JavaScript. You'll need to embed a short WAV file in the HTML, and then play that via code.

An Example:

function PlaySound(soundObj) {
  var sound = document.getElementById(soundObj);

<embed src="success.wav" autostart="false" width="0" height="0" id="sound1"

You would then call it from JavaScript code as such:


This should do exactly what you want - you'll just need to find/create the beep sound yourself, which should be trivial.

Java unsupported major minor version 52.0

I assumed openjdk8 would work with tomcat8 but I had to remove it and keep openjdk7 only, this fixed the issue in my case. I really don't know why or if there is something else I could have done.

Interop type cannot be embedded

I ran into this issue when pulling down a TFS project to my local machine. Allegedly, it was working fine on the guy's machine who wrote it. I simply changed this...

WshShellClass shellClass = new WshShellClass();

To this...

WshShell shellClass = new WshShell();

Now, it is working like a champ!

Connection timeout for SQL server

Yes, you could append ;Connection Timeout=30 to your connection string and specify the value you wish.

The timeout value set in the Connection Timeout property is a time expressed in seconds. If this property isn't set, the timeout value for the connection is the default value (15 seconds).

Moreover, setting the timeout value to 0, you are specifying that your attempt to connect waits an infinite time. As described in the documentation, this is something that you shouldn't set in your connection string:

A value of 0 indicates no limit, and should be avoided in a ConnectionString because an attempt to connect waits indefinitely.

Invoke a second script with arguments from a script

Much simpler actually:

Method 1:

Invoke-Expression $scriptPath $argumentList

Method 2:

& $scriptPath $argumentList

Method 3:

$scriptPath $argumentList

If you have spaces in your scriptPath, don't forget to escape them `"$scriptPath`"

"commence before first target. Stop." error

It's a simple Mistake while adding a new file you just have to make sure that \ is added to the file before and the new file remain as it is eg.

Check Out what to do if i want to add a new file named

How to add a href link in PHP?

There is no need to invoke PHP for this. Just put it directly into the HTML:

<a href="">...

how to detect search engine bots with php?

You can checkout if it's a search engine with this function :

function crawlerDetect($USER_AGENT)
$crawlers = array(
'Google' => 'Google',
'MSN' => 'msnbot',
      'Rambler' => 'Rambler',
      'Yahoo' => 'Yahoo',
      'AbachoBOT' => 'AbachoBOT',
      'accoona' => 'Accoona',
      'AcoiRobot' => 'AcoiRobot',
      'ASPSeek' => 'ASPSeek',
      'CrocCrawler' => 'CrocCrawler',
      'Dumbot' => 'Dumbot',
      'FAST-WebCrawler' => 'FAST-WebCrawler',
      'GeonaBot' => 'GeonaBot',
      'Gigabot' => 'Gigabot',
      'Lycos spider' => 'Lycos',
      'MSRBOT' => 'MSRBOT',
      'Altavista robot' => 'Scooter',
      'AltaVista robot' => 'Altavista',
      'ID-Search Bot' => 'IDBot',
      'eStyle Bot' => 'eStyle',
      'Scrubby robot' => 'Scrubby',
      'Facebook' => 'facebookexternalhit',
  // to get crawlers string used in function uncomment it
  // it is better to save it in string than use implode every time
  // global $crawlers
   $crawlers_agents = implode('|',$crawlers);
  if (strpos($crawlers_agents, $USER_AGENT) === false)
      return false;
    else {
    return TRUE;

Then you can use it like :

  if(crawlerDetect($USER_AGENT)) return "no need to lang redirection";?>

Internet Explorer 11 disable "display intranet sites in compatibility view" via meta tag not working

I solved this issue by redirecting the user to the FQDN of the server hosting the intranet.

IE probably uses the world's worst algorithm for detecting "intranet" sites ... indeed, specifying server.domain.tld solves the problem for me.

Yes, you read that correctly, IE detects intranet sites not by private IP address, like any dev who has heard of TCP/IP would do, no, by the "host" part of the URL, if it has no domain part, must be internal.

Scary to know the IE devs do not understand the most basic TCP/IP concepts.

Note that this was at a BIG enterprise customer, getting them to change GPO for you is like trying to move the Alps east by 4 meters, not gonna happen.

Oracle 11g SQL to get unique values in one column of a multi-column query

Eric Petroelje almost has it right:


Note: using ROWID (row unique id), not ROWNUM (which gives the row number within the result set)

Wrapping long text without white space inside of a div

You can't wrap that text as it's unbroken without any spaces. You need a JavaScript or server side solution which splits the string after a few characters.


You need to add this property in CSS.

word-wrap: break-word;

Removing elements from an array in C

There are really two separate issues. The first is keeping the elements of the array in proper order so that there are no "holes" after removing an element. The second is actually resizing the array itself.

Arrays in C are allocated as a fixed number of contiguous elements. There is no way to actually remove the memory used by an individual element in the array but the elements can be shifted to fill the hole made by removing an element. For example:

void remove_element(array_type *array, int index, int array_length)
   int i;
   for(i = index; i < array_length - 1; i++) array[i] = array[i + 1];

Statically allocated arrays can not be resized. Dynamically allocated arrays can be resized with realloc(). This will potentially move the entire array to another location in memory, so all pointers to the array or to its elements will have to be updated. For example:

remove_element(array, index, array_length);  /* First shift the elements, then reallocate */
array_type *tmp = realloc(array, (array_length - 1) * sizeof(array_type) );
if (tmp == NULL && array_length > 1) {
   /* No memory available */
array_length = array_length - 1;
array = tmp;

realloc will return a NULL pointer if the requested size is 0, or if there is an error. Otherwise it returns a pointer to the reallocated array. The temporary pointer is used to detect errors when calling realloc because instead of exiting it is also possible to just leave the original array as it was. When realloc fails to reallocate an array it does not alter the original array.

Note that both of these operations will be fairly slow if the array is large or if a lot of elements are removed. There are other data structures like linked lists and hashes that can be used if efficient insertion and deletion is a priority.

Python: Adding element to list while iterating

well, according to

It is not safe to modify the sequence being iterated over in the loop (this can only happen for mutable sequence types, such as lists). If you need to modify the list you are iterating over (for example, to duplicate selected items) you must iterate over a copy.

How to create a unique index on a NULL column?

The calculated column trick is widely known as a "nullbuster"; my notes credit Steve Kass:

pk int identity(1,1) primary key,
X  int NULL,
nullbuster as (case when X is null then pk else 0 end),
CONSTRAINT dupNulls_uqX UNIQUE (X,nullbuster)

load json into variable

<input  class="pull-right" id="currSpecID" name="currSpecID" value="">

   $.get("http://localhost:8080/HIS_API/rest/MriSpecimen/getMaxSpecimenID", function(data, status){
       alert("Data: " + data + "\nStatus: " + status);

enter image description here enter image description here

Why is textarea filled with mysterious white spaces?

Please make sure there is no linebreak or space after , it's to make sure there is no whitespace or tab, just copy and paste this code :) I had fix it for you

<textarea style="width:350px; height:80px;" cols="42" rows="5" name="sitelink"><?php if($siteLink_val) echo trim($siteLink_val);?></textarea>

Absolute vs relative URLs

In general, it is considered best-practice to use relative URLs, so that your website will not be bound to the base URL of where it is currently deployed. For example, it will be able to work on localhost, as well as on your public domain, without modifications.

How to disable <br> tags inside <div> by css?

You could alter your CSS to render them less obtrusively, e.g.

div p,
div br {
    display: inline;

or - as my commenter points out:

div br {
    display: none;

but then to achieve the example of what you want, you'll need to trim the p down, so:

div br {
    display: none;
div p {
    padding: 0;
    margin: 0;

Get selected option from select element

Using the selectedOptions property (HTML5) you can get the selected option(s)


With JQuery can be achieved by doing this




The property contains an HTMLCollection array similitar to this one selected option

[<option value=?"1">?ABC</option>]

or multiple selections

[<option value=?"1">?ABC</option>, <option value=?"2">?DEF</option> ...]

Android widget: How to change the text of a button

I had a button in my layout.xml that was defined as a View as in:

final View myButton = findViewById(;

I was not able to change the text on it until I also defined it as a button:

final View vButton = findViewById(;
final Button bButton = (Button) findViewById(;

When I needed to change the text, I used the bButton.setText("Some Text"); and when I wanted to alter the view, I used the vButton.

Worked great!

Set UILabel line spacing

My solution was to patch the font file itself and fix its line height definitely.

I had to modify 'lineGap', 'ascender', 'descender' in the 'hhea' block (as in the blog example).

Is there a way to override class variables in Java?

Just Call super.variable in sub class constructor

public abstract class Beverage {

int cost;

int getCost() {

    return cost;



public class Coffee extends Beverage {

int cost = 10;
    super.cost = cost;


public class Driver {

public static void main(String[] args) {

    Beverage coffee = new Coffee();




Output is 10.

Create a data.frame with m columns and 2 rows

Does m really need to be a data.frame() or will a matrix() suffice?

m <- matrix(0, ncol = 30, nrow = 2)

You can wrap a data.frame() around that if you need to:

m <- data.frame(m)

or all in one line: m <- data.frame(matrix(0, ncol = 30, nrow = 2))

Compiling simple Hello World program on OS X via command line

The new version of this should read like so:

xcrun g++ hw.cpp

Errno 10061 : No connection could be made because the target machine actively refused it ( client - server )

I had errors 10060 and 10061. The reason was in my antivirus(Eset Nod 32). Try to turn off the Firewall of your antivirus as I did or just delete it for a time to test the program. If everything started to work properly, add that program to the exclusion or switch to another antivirus. Also, try to change the 'host' variable to an empty string:

host = ''

And add socket.AF_INET, socket.SOCK_STREAM to the 's' variable:

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

Is it possible to use Visual Studio on macOS?

There is no native version of Visual Studio for Mac OS X.

Almost all versions of Visual Studio have a Garbage rating on Wine's application database, so Wine isn't an option either, sadly.

How do I run a program with commandline arguments using GDB within a Bash script?

gdb -ex=r --args myprogram arg1 arg2

-ex=r is short for -ex=run and tells gdb to run your program immediately, rather than wait for you to type "run" at the prompt. Then --args says that everything that follows is the command and arguments, just as you'd normally type them at the commandline prompt.

How do I get total physical memory size using PowerShell without WMI?

Maybe not the best solution, but it worked for me.


how to re-format datetime string in php?

You could do it like this:

$datetime = "20130409163705"; 
$format = "YmdHis";

$date = date_parse_from_format ($format, $datetime);
print_r ($date);

You can look at date_parse_from_format() and the accepted format values.

Bootstrap modal not displaying

I tracked down the reason.

Just to give it some general usefulness to anyone coming to this question. If you can't figure out what's wrong, try doing a 'search all' for any classes of 'modal' 'fade' 'fade in' and 'hide' in any style sheets in your application.

I had a single instance of 'fade' being defined in a random css file, and that's what was stopping it displaying as it was overriding bootstrap. Once I deleted the reference, everything was ok.

How do I get the color from a hexadecimal color code using .NET?

    private Color FromHex(string hex)
        if (hex.StartsWith("#"))
            hex = hex.Substring(1);

        if (hex.Length != 6) throw new Exception("Color not valid");

        return Color.FromArgb(
            int.Parse(hex.Substring(0, 2), System.Globalization.NumberStyles.HexNumber),
            int.Parse(hex.Substring(2, 2), System.Globalization.NumberStyles.HexNumber),
            int.Parse(hex.Substring(4, 2), System.Globalization.NumberStyles.HexNumber));

Declare an array in TypeScript

Here are the different ways in which you can create an array of booleans in typescript:

let arr1: boolean[] = [];
let arr2: boolean[] = new Array();
let arr3: boolean[] = Array();

let arr4: Array<boolean> = [];
let arr5: Array<boolean> = new Array();
let arr6: Array<boolean> = Array();

let arr7 = [] as boolean[];
let arr8 = new Array() as Array<boolean>;
let arr9 = Array() as boolean[];

let arr10 = <boolean[]> [];
let arr11 = <Array<boolean>> new Array();
let arr12 = <boolean[]> Array();

let arr13 = new Array<boolean>();
let arr14 = Array<boolean>();

You can access them using the index:


and you add elements using push:


When creating the array you can supply the initial values:

let arr1: boolean[] = [true, false];
let arr2: boolean[] = new Array(true, false);

Convert to/from DateTime and Time in Ruby

You can use to_date, e.g.

> Event.last.starts_at
=> Wed, 13 Jan 2021 16:49:36.292979000 CET +01:00
> Event.last.starts_at.to_date
=> Wed, 13 Jan 2021

How to change href of <a> tag on button click through javascript

Without having a href, the click will reload the current page, so you need something like this:

<a href="#" onclick="f1()">jhhghj</a>

Or prevent the scroll like this:

<a href="#" onclick="f1(); return false;">jhhghj</a>

Or return false in your f1 function and:

<a href="#" onclick="return f1();">jhhghj</a>

....or, the unobtrusive way:

<a href="#" id="abc">jhg</a>
<a href="#" id="myLink">jhhghj</a>

<script type="text/javascript">
  document.getElementById("myLink").onclick = function() {
    return false;

How do you discover model attributes in Rails?


Source: blog

Populating a razor dropdownlist from a List<object> in MVC

You can separate out your business logic into a viewmodel, so your view has cleaner separation.

First create a viewmodel to store the Id the user will select along with a list of items that will appear in the DropDown.


public class UserRoleViewModel
    // Display Attribute will appear in the Html.LabelFor
    [Display(Name = "User Role")]
    public int SelectedUserRoleId { get; set; }
    public IEnumerable<SelectListItem> UserRoles { get; set; }


Inside the controller create a method to get your UserRole list and transform it into the form that will be presented in the view.


private IEnumerable<SelectListItem> GetRoles()
    var dbUserRoles = new DbUserRoles();
    var roles = dbUserRoles
                .Select(x =>
                        new SelectListItem
                                Value = x.UserRoleId.ToString(),
                                Text = x.UserRole

    return new SelectList(roles, "Value", "Text");

public ActionResult AddNewUser()
    var model = new UserRoleViewModel
                        UserRoles = GetRoles()
    return View(model);


Now that the viewmodel is created the presentation logic is simplified


@model UserRoleViewModel

@Html.LabelFor(m => m.SelectedUserRoleId)
@Html.DropDownListFor(m => m.SelectedUserRoleId, Model.UserRoles)


This will produce:

<label for="SelectedUserRoleId">User Role</label>
<select id="SelectedUserRoleId" name="SelectedUserRoleId">
    <option value="1">First Role</option>
    <option value="2">Second Role</option>
    <option value="3">Etc...</option>

How do I echo and send console output to a file in a bat script?

My option was this:

Create a subroutine that takes in the message and automates the process of sending it to both console and log file.

set logfile=logfile.log

call :screenandlog "%DATE% %TIME% This message goes to the screen and to the log"    

goto :eof

set message=%~1
echo %message% & echo %message% >> %logfile%
exit /b

If you add a variable to the message, be sure to remove the quotes in it before sending it to the subroutine or it can screw your batch. Of course this only works for echoing.

Download image from the site in .NET/C#

        private static void DownloadRemoteImageFile(string uri, string fileName)
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();

            if ((response.StatusCode == HttpStatusCode.OK ||
                response.StatusCode == HttpStatusCode.Moved ||
                response.StatusCode == HttpStatusCode.Redirect) &&
                response.ContentType.StartsWith("image", StringComparison.OrdinalIgnoreCase)) 
                using (Stream inputStream = response.GetResponseStream())
                using (Stream outputStream = File.OpenWrite(fileName))
                    byte[] buffer = new byte[4096];
                    int bytesRead;
                        bytesRead = inputStream.Read(buffer, 0, buffer.Length);
                        outputStream.Write(buffer, 0, bytesRead);
                    } while (bytesRead != 0);

How to extract img src, title and alt from html using php?

I have read the many comments on this page that complain that using a dom parser is unnecessary overhead. Well, it may be more expensive than a mere regex call, but the OP has stated that there is no control over the order of the attributes in the img tags. This fact leads to unnecessary regex pattern convolution. Beyond that, using a dom parser provides the additional benefits of readability, maintainability, and dom-awareness (regex is not dom-aware).

I love regex and I answer lots of regex questions, but when dealing with valid HTML there is seldom a good reason to regex over a parser.

In the demonstration below, see how easy and clean DOMDocument handles img tag attributes in any order with a mixture of quoting (and no quoting at all). Also notice that tags without a targeted attribute are not disruptive at all -- an empty string is provided as a value.

Code: (Demo)

$test = <<<HTML
<img src="/image/fluffybunny.jpg" title="Harvey the bunny" alt="a cute little fluffy bunny" />
<img src='/image/pricklycactus.jpg' title='Roger the cactus' alt='a big green prickly cactus' />
<p>This is irrelevant text.</p>
<img alt="an annoying white cockatoo" title="Polly the cockatoo" src="/image/noisycockatoo.jpg">
<img title=something src=somethingelse>

libxml_use_internal_errors(true);  // silences/forgives complaints from the parser (remove to see what is generated)
$dom = new DOMDocument();
foreach ($dom->getElementsByTagName('img') as $i => $img) {
    echo "IMG#{$i}:\n";
    echo "\tsrc = " , $img->getAttribute('src') , "\n";
    echo "\ttitle = " , $img->getAttribute('title') , "\n";
    echo "\talt = " , $img->getAttribute('alt') , "\n";
    echo "---\n";


    src = /image/fluffybunny.jpg
    title = Harvey the bunny
    alt = a cute little fluffy bunny
    src = /image/pricklycactus.jpg
    title = Roger the cactus
    alt = a big green prickly cactus
    src = /image/noisycockatoo.jpg
    title = Polly the cockatoo
    alt = an annoying white cockatoo
    src = somethingelse
    title = something
    alt = 

Using this technique in professional code will leave you with a clean script, fewer hiccups to contend with, and fewer colleagues that wish you worked somewhere else.

HTML table sort

The way I have sorted HTML tables in the browser uses plain, unadorned Javascript.

The basic process is:

  1. add a click handler to each table header
  2. the click handler notes the index of the column to be sorted
  3. the table is converted to an array of arrays (rows and cells)
  4. that array is sorted using javascript sort function
  5. the data from the sorted array is inserted back into the HTML table

The table should, of course, be nice HTML. Something like this...


So, first adding the click handlers...

const table = document.querySelector('table'); //get the table to be sorted

table.querySelectorAll('th') // get all the table header elements
  .forEach((element, columnNo)=>{ // add a click handler for each 
    element.addEventListener('click', event => {
        sortTable(table, columnNo); //call a function which sorts the table by a given column number

This won't work right now because the sortTable function which is called in the event handler doesn't exist.

Lets write it...

function sortTable(table, sortColumn){
  // get the data from the table cells
  const tableBody = table.querySelector('tbody')
  const tableData = table2data(tableBody);
  // sort the extracted data
  tableData.sort((a, b)=>{
    if(a[sortColumn] > b[sortColumn]){
      return 1;
    return -1;
  // put the sorted data back into the table
  data2table(tableBody, tableData);

So now we get to the meat of the problem, we need to make the functions table2data to get data out of the table, and data2table to put it back in once sorted.

Here they are ...

// this function gets data from the rows and cells 
// within an html tbody element
function table2data(tableBody){
  const tableData = []; // create the array that'll hold the data rows
    .forEach(row=>{  // for each table row...
      const rowData = [];  // make an array for that row
      row.querySelectorAll('td')  // for each cell in that row
          rowData.push(cell.innerText);  // add it to the row data
      tableData.push(rowData);  // add the full row to the table data 
  return tableData;

// this function puts data into an html tbody element
function data2table(tableBody, tableData){
  tableBody.querySelectorAll('tr') // for each table row...
    .forEach((row, i)=>{  
      const rowData = tableData[i]; // get the array for the row data
      row.querySelectorAll('td')  // for each table cell ...
        .forEach((cell, j)=>{
          cell.innerText = rowData[j]; // put the appropriate array element into the cell

And that should do it.

A couple of things that you may wish to add (or reasons why you may wish to use an off the shelf solution): An option to change the direction and type of sort i.e. you may wish to sort some columns numerically ("10" > "2" is false because they're strings, probably not what you want). The ability to mark a column as sorted. Some kind of data validation.

Bash command line and input limit

Ok, Denizens. So I have accepted the command line length limits as gospel for quite some time. So, what to do with one's assumptions? Naturally- check them.

I have a Fedora 22 machine at my disposal (meaning: Linux with bash4). I have created a directory with 500,000 inodes (files) in it each of 18 characters long. The command line length is 9,500,000 characters. Created thus:

seq 1 500000 | while read digit; do
    touch $(printf "abigfilename%06d\n" $digit);

And we note:

$ getconf ARG_MAX

Note however I can do this:

$ echo * > /dev/null

But this fails:

$ /bin/echo * > /dev/null
bash: /bin/echo: Argument list too long

I can run a for loop:

$ for f in *; do :; done

which is another shell builtin.

Careful reading of the documentation for ARG_MAX states, Maximum length of argument to the exec functions. This means: Without calling exec, there is no ARG_MAX limitation. So it would explain why shell builtins are not restricted by ARG_MAX.

And indeed, I can ls my directory if my argument list is 109948 files long, or about 2,089,000 characters (give or take). Once I add one more 18-character filename file, though, then I get an Argument list too long error. So ARG_MAX is working as advertised: the exec is failing with more than ARG_MAX characters on the argument list- including, it should be noted, the environment data.

Updating version numbers of modules in a multi-module Maven project

versions:update-child-modules sounds like what you're looking for. You could do versions:set as mentioned, but this is a light-weight way to update the parent version numbers. For the child modules, it's my opinion that you should remove the <version> definitions, since they will inherit the parent module's version number.

Warning: date_format() expects parameter 1 to be DateTime

Why don't you try it like this:

$Weddingdate = new DateTime($row2['weddingdate']);
$formattedweddingdate = date_format($Weddingdate, 'd-m-Y');

Or you can also just do it like :

$Weddingdate = new DateTime($row2['weddingdate']);
echo $Weddingdate->format('d-m-Y');

How to manually trigger validation with jQuery validate?

Eva M from above, almost had the answer as posted above (Thanks Eva M!):

var validator = $( "#myform" ).validate();

This is almost the answer, but it causes problems, in even the most up to date jquery validation plugin as of 13 DEC 2018. The problem is that if one directly copies that sample, and EVER calls ".validate()" more than once, the focus/key processing of the validation can get broken, and the validation may not show errors properly.

Here is how to use Eva M's answer, and ensure those focus/key/error-hiding issues do not occur:

1) Save your validator to a variable/global.

var oValidator = $("#myform").validate();

2) DO NOT call $("#myform").validate() EVER again.

If you call $("#myform").validate() more than once, it may cause focus/key/error-hiding issues.

3) Use the variable/global and call form.

var bIsValid = oValidator.form();

Cookies vs. sessions

when you save the #ID as the cookie to recognize logged in users, you actually are showing data to users that is not related to them. In addition, if a third party tries to set random IDs as cookie data in their browser, they will be able to convince the server that they are a user while they actually are not. That's a lack of security.

You have used cookies, and as you said you have already completed most of the project. besides cookie has the privilege of remaining for a long time, while sessions end more quickly. So sessions are not suitable in this case. In reality many famous and popular websites and services use cookie and you can stay logged-in for a long time. But how can you use their method to create a safer log-in process?

here's the idea: you can help the way you use cookies: If you use random keys instead of IDs to recognize logged-in users, first, you don't leak your primary data to random users, and second, If you consider the Random key large enough, It will be harder for anyone to guess a key or create a random one. for example you can save a 40 length key like this in User's browser: "KUYTYRFU7987gJHFJ543JHBJHCF5645UYTUYJH54657jguthfn" and it will be less likely for anyone to create the exact key and pretend to be someone else.

How to make a PHP SOAP call using the SoapClient class

This is what you need to do.

I tried to recreate the situation...

  • For this example, I created a .NET sample WebService (WS) with a WebMethod called Function1 expecting the following params:

Function1(Contact Contact, string description, int amount)

  • Where Contact is just a model that has getters and setters for id and name like in your case.

  • You can download the .NET sample WS at:

The code.

This is what you need to do at PHP side:

(Tested and working)

// Create Contact class
class Contact {
    public function __construct($id, $name) 
        $this->id = $id;
        $this->name = $name;

// Initialize WS with the WSDL
$client = new SoapClient("http://localhost:10139/Service1.asmx?wsdl");

// Create Contact obj
$contact = new Contact(100, "John");

// Set request params
$params = array(
  "Contact" => $contact,
  "description" => "Barrel of Oil",
  "amount" => 500,

// Invoke WS method (Function1) with the request params 
$response = $client->__soapCall("Function1", array($params));

// Print WS response


Testing the whole thing.

  • If you do print_r($params) you will see the following output, as your WS would expect:

Array ( [Contact] => Contact Object ( [id] => 100 [name] => John ) [description] => Barrel of Oil [amount] => 500 )

  • When I debugged the .NET sample WS I got the following:

enter image description here

(As you can see, Contact object is not null nor the other params. That means your request was successfully done from PHP side)

  • The response from the .NET sample WS was the expected one and this is what I got at PHP side:

object(stdClass)[3] public 'Function1Result' => string 'Detailed information of your request! id: 100, name: John, description: Barrel of Oil, amount: 500' (length=98)

Happy Coding!

Compile to stand alone exe for C# app in Visual Studio 2010

Press the start button in visual studio. Then go to the location where your solution is stored and open the folder of your main project then the bin folder. If your application was running in debug mode then go to the debug folder. If running in release mode then go to the release folder. You should find your exe there.

What's the difference of $host and $http_host in Nginx

$host is a variable of the Core module.


This variable is equal to line Host in the header of request or name of the server processing the request if the Host header is not available.

This variable may have a different value from $http_host in such cases: 1) when the Host input header is absent or has an empty value, $host equals to the value of server_name directive; 2)when the value of Host contains port number, $host doesn't include that port number. $host's value is always lowercase since 0.8.17.

$http_host is also a variable of the same module but you won't find it with that name because it is defined generically as $http_HEADER (ref).


The value of the HTTP request header HEADER when converted to lowercase and with 'dashes' converted to 'underscores', e.g. $http_user_agent, $http_referer...;


  • $http_host equals always the HTTP_HOST request header.
  • $host equals $http_host, lowercase and without the port number (if present), except when HTTP_HOST is absent or is an empty value. In that case, $host equals the value of the server_name directive of the server which processed the request.

SQL Server - calculate elapsed time between two datetime stamps in HH:MM:SS format


SELECT @StartTime = '2013-03-08 08:00:00', @EndTime = '2013-03-08 08:30:00'

SELECT CAST(@EndTime - @StartTime AS TIME)

Result: 00:30:00.0000000

Format result as you see fit.

When to catch java.lang.Error?

Very, very rarely.

I did it only for one very very specific known cases. For example, java.lang.UnsatisfiedLinkError could be throw if two independence ClassLoader load same DLL. (I agree that I should move the JAR to a shared classloader)

But most common case is that you needed logging in order to know what happened when user come to complain. You want a message or a popup to user, rather then silently dead.

Even programmer in C/C++, they pop an error and tell something people don't understand before it exit (e.g. memory failure).

What’s the best way to check if a file exists in C++? (cross platform)

Use boost::filesystem:

#include <boost/filesystem.hpp>

if ( !boost::filesystem::exists( "myfile.txt" ) )
  std::cout << "Can't find my file!" << std::endl;

Re-render React component when prop changes

You have to add a condition in your componentDidUpdate method.

The example is using fast-deep-equal to compare the objects.

import equal from 'fast-deep-equal'


  this.updateUser = this.updateUser.bind(this);

componentDidMount() {

componentDidUpdate(prevProps) {
  if(!equal(this.props.user, prevProps.user)) // Check if it's a new user, you can also use some unique property, like the ID  ( !==

updateUser() {
  if (this.props.isManager) {
  } else {
    const currentUserId = this.props.user.get('id')

Using Hooks (React 16.8.0+)

import React, { useEffect } from 'react';

const SitesTableContainer = ({
}) => {
  useEffect(() => {
    if(isManager) {
    } else {
      const currentUserId = user.get('id')
  }, [user]); 

  return (
    return <SitesTable sites={sites}/>


If the prop you are comparing is an object or an array, you should use useDeepCompareEffect instead of useEffect.

How to resolve "gpg: command not found" error during RVM installation?

As the instruction said "might need gpg2"

In mac, you can try install it with homebrew

$ brew install gpg2 

Git merge error "commit is not possible because you have unmerged files"

You need to do two things. First add the changes with

git add .
git stash  

git checkout <some branch>

It should solve your issue as it solved to me.

How to set max_connections in MySQL Programmatically

How to change max_connections

You can change max_connections while MySQL is running via SET:

mysql> SET GLOBAL max_connections = 5000;
Query OK, 0 rows affected (0.00 sec)

mysql> SHOW VARIABLES LIKE "max_connections";
| Variable_name   | Value |
| max_connections | 5000  |
1 row in set (0.00 sec)


timeout related

I had never seen your error message before, so I googled. probably, you are using Connector/Net. Connector/Net Manual says there is max connection pool size. (default is 100) see table 22.21.

I suggest that you increase this value to 100k or disable connection pooling Pooling=false


he has two questions.

Q1 - what happens if I disable pooling Slow down making DB connection. connection pooling is a mechanism that use already made DB connection. cost of Making new connection is high.

Q2 - Can the value of pooling be increased or the maximum is 100?

you can increase but I'm sure what is MAX value, maybe max_connections in my.cnf

My suggestion is that do not turn off Pooling, increase value by 100 until there is no connection error.

If you have Stress Test tool like JMeter you can test youself.

Should MySQL have its timezone set to UTC?

It seems that it does not matter what timezone is on the server as long as you have the time set right for the current timezone, know the timezone of the datetime columns that you store, and are aware of the issues with daylight savings time.

On the other hand if you have control of the timezones of the servers you work with then you can have everything set to UTC internally and never worry about timezones and DST.

Here are some notes I collected of how to work with timezones as a form of cheatsheet for myself and others which might influence what timezone the person will choose for his/her server and how he/she will store date and time.

MySQL Timezone Cheatsheet


  1. Changing the timezone will not change the stored datetime or timestamp, but it will select a different datetime from timestamp columns
  2. Warning! UTC has leap seconds, these look like '2012-06-30 23:59:60' and can be added randomly, with 6 months prior notice, due to the slowing of the earths rotation
  3. GMT confuses seconds, which is why UTC was invented.

  4. Warning! different regional timezones might produce the same datetime value due to daylight savings time

  5. The timestamp column only supports dates 1970-01-01 00:00:01 to 2038-01-19 03:14:07 UTC, due to a limitation.
  6. Internally a MySQL timestamp column is stored as UTC but when selecting a date MySQL will automatically convert it to the current session timezone.

    When storing a date in a timestamp, MySQL will assume that the date is in the current session timezone and convert it to UTC for storage.

  7. MySQL can store partial dates in datetime columns, these look like "2013-00-00 04:00:00"
  8. MySQL stores "0000-00-00 00:00:00" if you set a datetime column as NULL, unless you specifically set the column to allow null when you create it.
  9. Read this

To select a timestamp column in UTC format

no matter what timezone the current MySQL session is in:

CONVERT_TZ(`timestamp_field`, @@session.time_zone, '+00:00') AS `utc_datetime` 
FROM `table_name`

You can also set the sever or global or current session timezone to UTC and then select the timestamp like so:

SELECT `timestamp_field` FROM `table_name`

To select the current datetime in UTC:

SELECT CONVERT_TZ(NOW(), @@session.time_zone, '+00:00');

Example result: 2015-03-24 17:02:41

To select the current datetime in the session timezone


To select the timezone that was set when the server launched

SELECT @@system_time_zone;

Returns "MSK" or "+04:00" for Moscow time for example, there is (or was) a MySQL bug where if set to a numerical offset it would not adjust the Daylight savings time

To get the current timezone


It will return 02:00:00 if your timezone is +2:00.

To get the current UNIX timestamp (in seconds):


To get the timestamp column as a UNIX timestamp

SELECT UNIX_TIMESTAMP(`timestamp`) FROM `table_name`

To get a UTC datetime column as a UNIX timestamp

SELECT UNIX_TIMESTAMP(CONVERT_TZ(`utc_datetime`, '+00:00', @@session.time_zone)) FROM `table_name`

Get a current timezone datetime from a positive UNIX timestamp integer

SELECT FROM_UNIXTIME(`unix_timestamp_int`) FROM `table_name`

Get a UTC datetime from a UNIX timestamp

SELECT CONVERT_TZ(FROM_UNIXTIME(`unix_timestamp_int`), @@session.time_zone, '+00:00') 
FROM `table_name`

Get a current timezone datetime from a negative UNIX timestamp integer

SELECT DATE_ADD('1970-01-01 00:00:00',INTERVAL -957632400 SECOND) 

There are 3 places where the timezone might be set in MySQL:

Note: A timezone can be set in 2 formats:

  1. an offset from UTC: '+00:00', '+10:00' or '-6:00'
  2. as a named time zone: 'Europe/Helsinki', 'US/Eastern', or 'MET'

Named time zones can be used only if the time zone information tables in the mysql database have been created and populated.

in the file "my.cnf"




@@global.time_zone variable

To see what value they are set to

SELECT @@global.time_zone;

To set a value for it use either one:

SET GLOBAL time_zone = '+8:00';
SET GLOBAL time_zone = 'Europe/Helsinki';
SET @@global.time_zone='+00:00';

@@session.time_zone variable

SELECT @@session.time_zone;

To set it use either one:

SET time_zone = 'Europe/Helsinki';
SET time_zone = "+00:00";
SET @@session.time_zone = "+00:00";

both "@@global.time_zone variable" and "@@session.time_zone variable" might return "SYSTEM" which means that they use the timezone set in "my.cnf".

For timezone names to work (even for default-time-zone) you must setup your timezone information tables need to be populated:

Note: you can not do this as it will return NULL:

CONVERT_TZ(`timestamp_field`, TIMEDIFF(NOW(), UTC_TIMESTAMP), '+00:00') AS `utc_datetime` 
FROM `table_name`

Setup mysql timezone tables

For CONVERT_TZ to work, you need the timezone tables to be populated

SELECT * FROM mysql.`time_zone` ;
SELECT * FROM mysql.`time_zone_leap_second` ;
SELECT * FROM mysql.`time_zone_name` ;
SELECT * FROM mysql.`time_zone_transition` ;
SELECT * FROM mysql.`time_zone_transition_type` ;

If they are empty, then fill them up by running this command

mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql

if this command gives you the error "data too long for column 'abbreviation' at row 1", then it might be caused by a NULL character being appended at the end of the timezone abbreviation

the fix being to run this

mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql
(if the above gives error "data too long for column 'abbreviation' at row 1")
mysql_tzinfo_to_sql /usr/share/zoneinfo > /tmp/zut.sql

echo "SET SESSION SQL_MODE = '';" > /tmp/mysql_tzinfo_to.sql
cat /tmp/zut.sql >> /tmp/mysql_tzinfo_to.sql

mysql --defaults-file=/etc/mysql/my.cnf --user=verifiedscratch -p mysql < /tmp/mysql_tzinfo_to.sql

(make sure your servers dst rules are up to date zdump -v Europe/Moscow | grep 2011

See the full DST (Daylight Saving Time) transition history for every timezone

tzn.Name AS tz_name,
tztt.Abbreviation AS tz_abbr,
tztt.Is_DST AS is_dst,
tztt.`Offset` AS `offset`,
DATE_ADD('1970-01-01 00:00:00',INTERVAL tzt.Transition_time SECOND)  AS transition_date
FROM mysql.`time_zone_transition` tzt
INNER JOIN mysql.`time_zone_transition_type` tztt USING(Time_zone_id, Transition_type_id)
INNER JOIN mysql.`time_zone_name` tzn USING(Time_zone_id)
-- WHERE tzn.Name LIKE 'Europe/Moscow' -- Moscow has weird DST changes
ORDER BY tzt.Transition_time ASC

CONVERT_TZ also applies any necessary DST changes based on the rules in the above tables and the date that you use.

According to the docs, the value you set for time_zone does not change, if you set it as "+01:00" for example, then the time_zone will be set as an offset from UTC, which does not follow DST, so it will stay the same all year round.

Only the named timezones will change time during daylight savings time.

Abbreviations like CET will always be a winter time and CEST will be summer time while +01:00 will always be UTC time + 1 hour and both won't change with DST.

The system timezone will be the timezone of the host machine where mysql is installed (unless mysql fails to determine it)

You can read more about working with DST here

related questions:


How to list the certificates stored in a PKCS12 keystore with keytool?

You can also use openssl to accomplish the same thing:

$ openssl pkcs12 -nokeys -info \
    -in </path/to/file.pfx> \
    -passin pass:<pfx's password>

MAC Iteration 2048
MAC verified OK
PKCS7 Encrypted data: pbeWithSHA1And40BitRC2-CBC, Iteration 2048
Certificate bag
Bag Attributes
    localKeyID: XX XX XX XX XX XX XX XX XX XX XX XX XX 48 54 A0 47 88 1D 90
    friendlyName: jedis-server
subject=/C=US/ST=NC/L=Raleigh/O=XXX Security/OU=XXX/CN=something1
issuer=/C=US/ST=NC/L=Raleigh/O=XXX Security/OU=XXXX/CN=something1
PKCS7 Data
Shrouded Keybag: pbeWithSHA1And3-KeyTripleDES-CBC, Iteration 2048

How to check if an integer is within a range of numbers in PHP?

$ranges = [
    1 => [
        'min_range' => 0.01,
        'max_range' => 199.99
    2 => [
        'min_range' => 200.00,

   foreach( $ranges as $value => $range ){
        if( filter_var( $cartTotal, FILTER_VALIDATE_FLOAT, [ 'options' => $range ] ) ){
            return $value;

Git says local branch is behind remote branch, but it's not

To diagnose it, follow this answer.

But to fix it, knowing you are the only one changing it, do:
1 - backup your project (I did only the files on git, ./src folder)
2 - git pull
3 - restore you backup over the many "messed" files (with merge indicators)

I tried git pull -s recursive -X ours but didnt work the way I wanted, it could be an option tho, but backup first!!!

Make sure the differences/changes (at git gui) are none. This is my case, there is nothing to merge at all, but github keeps saying I should merge...

How to load my app from Eclipse to my Android phone instead of AVD

For those who are trying to find how to enable debugging on devices running Jelly Bean 4.2 (e.g Google Nexus), you have to go to Settings > Apps > About tablet and tap the text "Build number" 7 times slowly. Go back to the now available Settings > Developer options and check USB debugging as stated in previous posts.

Is there any use for unique_ptr with array?

A common pattern can be found in some Windows Win32 API calls, in which the use of std::unique_ptr<T[]> can come in handy, e.g. when you don't exactly know how big an output buffer should be when calling some Win32 API (that will write some data inside that buffer):

// Buffer dynamically allocated by the caller, and filled by some Win32 API function.
// (Allocation will be made inside the 'while' loop below.)
std::unique_ptr<BYTE[]> buffer;

// Buffer length, in bytes.
// Initialize with some initial length that you expect to succeed at the first API call.
UINT32 bufferLength = /* ... */;

    // Allocate buffer of specified length
    buffer.reset( BYTE[bufferLength] );
    // Or, in C++14, could use make_unique() instead, e.g.
    // buffer = std::make_unique<BYTE[]>(bufferLength);

    // Call some Win32 API.
    // If the size of the buffer (stored in 'bufferLength') is not big enough,
    // the API will return ERROR_INSUFFICIENT_BUFFER, and the required size
    // in the [in, out] parameter 'bufferLength'.
    // In that case, there will be another try in the next loop iteration
    // (with the allocation of a bigger buffer).
    // Else, we'll exit the while loop body, and there will be either a failure
    // different from ERROR_INSUFFICIENT_BUFFER, or the call will be successful
    // and the required information will be available in the buffer.
    returnCode = ::SomeApiCall(inParam1, inParam2, inParam3, 
                               &bufferLength, // size of output buffer
                               buffer.get(),  // output buffer pointer
                               &outParam1, &outParam2);

if (Failed(returnCode))
    // Handle failure, or throw exception, etc.

// All right!
// Do some processing with the returned information...

GIT fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree

Jacob Helwig mentions in his answer that:

It looks like rev-parse is being used without sufficient error checking before-hand

Commit 62f162f from Jeff King (peff) should improve the robustness of git rev-parse in Git 1.9/2.0 (Q1 2014) (in addition of commit 1418567):

For cases where we do not match (e.g., "doesnotexist..HEAD"), we would then want to try to treat the argument as a filename.
try_difference() gets this right, and always unmunges in this case.
However, try_parent_shorthand() never unmunges, leading to incorrect error messages, or even incorrect results:

$ git rev-parse foobar^@
fatal: ambiguous argument 'foobar': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

Professional jQuery based Combobox control?

A new fork of the sexy-combo project is now out which looks promising:

How to uncompress a tar.gz in another directory

You can use for loop to untar multiple .tar.gz files to another folder. The following code will take /destination/folder/path as an argument to the script and untar all .tar.gz files present at the current location in /destination/folder/path.

if [ $# -ne 1 ];
 echo "invalid argument/s"
 echo "Usage: ./ /target/directory"
 exit 0
for file in *.tar.gz
    tar -zxvf "$file" --directory $1

What is the difference between static func and class func in Swift?

Is it simply that static is for static functions of structs and enums, and class for classes and protocols?

That's the main difference. Some other differences are that class functions are dynamically dispatched and can be overridden by subclasses.

Protocols use the class keyword, but it doesn't exclude structs from implementing the protocol, they just use static instead. Class was chosen for protocols so there wouldn't have to be a third keyword to represent static or class.

From Chris Lattner on this topic:

We considered unifying the syntax (e.g. using "type" as the keyword), but that doesn't actually simply things. The keywords "class" and "static" are good for familiarity and are quite descriptive (once you understand how + methods work), and open the door for potentially adding truly static methods to classes. The primary weirdness of this model is that protocols have to pick a keyword (and we chose "class"), but on balance it is the right tradeoff.

And here's a snippet that shows some of the override behavior of class functions:

class MyClass {
    class func myFunc() {

class MyOtherClass: MyClass {
    override class func myFunc() {

var x: MyClass = MyOtherClass()
x.dynamicType.myFunc() //myOtherClass
x = MyClass()
x.dynamicType.myFunc() //myClass

Map.Entry: How to use it?

public HashMap<Integer,Obj> ListeObj= new HashMap<>();

public void addObj(String param1, String param2, String param3){
  Obj newObj = new Obj(param1, param2, param3);
  this.ListObj.put(newObj.getId(), newObj);

public ArrayList<Integer> searchdObj (int idObj){
  ArrayList<Integer> returnList = new ArrayList<>();
  for (java.util.Map.Entry<Integer, Obj> e : this.ListObj.entrySet()){
    if(e.getValue().getName().equals(idObj)) {
return returnList;

How to change background color of cell in table using java script

Try this:

function btnClick() {
    var x = document.getElementById("mytable").getElementsByTagName("td");
    x[0].innerHTML = "i want to change my cell color";
    x[0].style.backgroundColor = "yellow";            

Set from JS, backgroundColor is the equivalent of background-color in your style-sheet.

Note also that the .cells collection belongs to a table row, not to the table itself. To get all the cells from all rows you can instead use getElementsByTagName().


React JS onClick event handler

Handling events with React elements is very similar to handling events on DOM elements. There are some syntactic differences:

  • React events are named using camelCase, rather than lowercase.
  • With JSX you pass a function as the event handler, rather than a string.

So as mentioned in React documentation, they quite similar to normal HTML when it comes to Event Handling, but event names in React using camelcase, because they are not really HTML, they are JavaScript, also, you pass the function while we passing function call in a string format for HTML, they are different, but the concepts are pretty similar...

Look at the example below, pay attention to the way event get passed to the function:

function ActionLink() {
  function handleClick(e) {
    console.log('The link was clicked.');

  return (
    <a href="#" onClick={handleClick}>
      Click me

How to make a div fill a remaining horizontal space?

The solution comes from the display property.

Basically you need to make the two divs act like table cells. So instead of using float:left, you'll have to use display:table-cell on both divs, and for the dynamic width div you need to set width:auto; also. The both divs should be placed into a 100% width container with the display:table property.

Here is the css:

.container {display:table;width:100%}
#search {
  width: 160px;
  height: 25px;
  background-color: #FFF;
#navigation {
  width: auto;
  /*background-color: url('../images/transparent.png') ;*/
  background-color: #A53030;

*html #navigation {float:left;}

And the HTML:

<div class="container">
   <div id="search"></div>
   <div id="navigation"></div>

IMPORTANT:For Internet Explorer you need to specify the float property on the dynamic width div, otherwise the space will not be filled.

I hope that this will solve your problem. If you want, you can read the full article I wrote about this on my blog.

java.lang.RuntimeException: Unable to instantiate org.apache.hadoop.hive.ql.metadata.SessionHiveMetaStoreClient

starting the hive metastore service worked for me. First, set up the database for hive metastore:

 $ hive --service metastore 


Second, run the following commands:

 $ schematool -dbType mysql -initSchema  
 $ schematool -dbType mysql -info

Save image from url with curl PHP

try this:

function grab_image($url,$saveto){
    $ch = curl_init ($url);
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_BINARYTRANSFER,1);
    curl_close ($ch);
    $fp = fopen($saveto,'x');
    fwrite($fp, $raw);

and ensure that in php.ini allow_url_fopen is enable

Passing html values into javascript functions

Simply put id attribute in your input text field -

<input type="text" maxlength="3" name="value" id="value" />

Android studio 3.0: Unable to resolve dependency for :app@dexOptions/compileClasspath': Could not resolve project :animators

Step 1:
1.Open the Preferences, by clicking File > Settings (on Mac, Android Studio > Preferences).
2.In the left pane, click Build, Execution, Deployment >> Gradle.
3.Uncheck/disable the Offline work checkbox.
4.Click Apply or OK.

Step 2:
downgrade the content which you can access this 
file directory by clicking on CTRL + SHFT +R KEY 
e.g from


or to any lower version like / or /

Redirect form to different URL based on select option element

you can use this simple way

<select onchange="location = this.value;">
                <option value="/finished">Finished</option>
                <option value="/break">Break</option>
                <option value="/issue">Issues</option>
                <option value="/downtime">Downtime</option>

will redirect to route url you can direct to .html page or direct to some link just change value in option.

How to logout and redirect to login page using Laravel 5.4?

Best way for Laravel 5.8

100% worked

Add this function inside your Auth\LoginController.php

use Illuminate\Http\Request;

And also add this

public function logout(Request $request)


    return $this->loggedOut($request) ?: redirect('/login');

Reading local text file into a JavaScript array

Using Node.js

sync mode:

var fs = require("fs");
var text = fs.readFileSync("./mytext.txt");
var textByLine = text.split("\n")

async mode:

var fs = require("fs");
fs.readFile("./mytext.txt", function(text){
    var textByLine = text.split("\n")


As of at least Node 6, readFileSync returns a Buffer, so it must first be converted to a string in order for split to work:

var text = fs.readFileSync("./mytext.txt").toString('utf-8');


var text = fs.readFileSync("./mytext.txt", "utf-8");

Hide HTML element by id

<style type="text/css">
  #nav-ask{ display:none; }

Use async await with

A solution using modern-async's map():

import { map } from 'modern-async'

const result = await map(myArray, async (v) => {

The advantage of using that library is that you can control the concurrency using mapLimit() or mapSeries().

How to redirect to another page using PHP

firstly create index.php page and just copy paste below code :-

<form name="frmUser" class="well login-form" id="form" method="post" action="login_check.php" onSubmit="return FormValidation()">
        <icon class="icon-circles"></icon>Restricted Area<icon class="icon-circles-reverse"></icon>
    <div class="control-group">
        <label class="control-label" for="inputPassword">Username</label>
        <div class="controls">
            <div class="input-prepend">
                <span class="add-on"><icon class="icon-user icon-cream"></icon> </span>
                <input class="input" type="text" name="username" id="username" placeholder="Username" />
    <div class="control-group">
        <label class="control-label" for="inputPassword">Password</label>
        <div class="controls">
            <div class="input-prepend">
                <span class="add-on"><icon class="icon-password icon-cream"></icon>
                </span> <input class="input" type="password" name="password" id="password" value="" placeholder="Password" />
    <div class="control-group signin">
        <div class="controls ">
            <input type="submit" class="btn btn-block" value="Submit" />
            <div class="clearfix">
                <span class="icon-forgot"></span><a href="#">forgot password</a>

/*------------------after that ----------------------*/

create a login_check.php and just copy paste this below code :-


/* Redirect browser */

/* Make sure that code below does not get executed when we redirect. */



    $result = mysql_query("SELECT * FROM admin WHERE username='".$_POST["username"]."' and password = '".$_POST["password"]."'");
    $row  = mysql_fetch_array($result);

    $_SESSION["user_id"] = $row[user_id];
    $_SESSION["username"] = $row[username];

    $session_register["user_id"] = $row[user_id];
    $session_register["username"] = $row[username];
   $_SESSION['msg']="Invalid Username or Password";



/*-----------------------after that ----------------------*/

create a dashboard.php and copy paste this code in starting of dashboard.php


/*-----------------------after that-----------------*/ 

create a check_session.php which check your session and copy paste this code :- 

    Welcome <?php echo $_SESSION["user_name"]; ?>. Click here to <a href="logout.php" tite="Logout">Logout.</a>

if you have any query so let me know on my mail id [email protected]

How to add additional libraries to Visual Studio project?

For Visual Studio you'll want to right click on your project in the solution explorer and then click on Properties.

Next open Configuration Properties and then Linker.

Now you want to add the folder you have the Allegro libraries in to Additional Library Directories,

Linker -> Input you'll add the actual library files under Additional Dependencies.

For the Header Files you'll also want to include their directories under C/C++ -> Additional Include Directories.

If there is a dll have a copy of it in your main project folder, and done.

I would recommend putting the Allegro files in the your project folder and then using local references in for the library and header directories.

Doing this will allow you to run the application on other computers without having to install Allergo on the other computer.

This was written for Visual Studio 2008. For 2010 it should be roughly the same.

How to create a stopwatch using JavaScript?

Please see stopwatch.js for a very clean and simple Vanilla Javascript ES6 solution.

.NET / C# - Convert char[] to string

Use the constructor of string which accepts a char[]

char[] c = ...;
string s = new string(c);

What are the differences between type() and isinstance()?

Differences between isinstance() and type() in Python?

Type-checking with

isinstance(obj, Base)

allows for instances of subclasses and multiple possible bases:

isinstance(obj, (Base1, Base2))

whereas type-checking with

type(obj) is Base

only supports the type referenced.

As a sidenote, is is likely more appropriate than

type(obj) == Base

because classes are singletons.

Avoid type-checking - use Polymorphism (duck-typing)

In Python, usually you want to allow any type for your arguments, treat it as expected, and if the object doesn't behave as expected, it will raise an appropriate error. This is known as polymorphism, also known as duck-typing.

def function_of_duck(duck):

If the code above works, we can presume our argument is a duck. Thus we can pass in other things are actual sub-types of duck:


or that work like a duck:


and our code still works.

However, there are some cases where it is desirable to explicitly type-check. Perhaps you have sensible things to do with different object types. For example, the Pandas Dataframe object can be constructed from dicts or records. In such a case, your code needs to know what type of argument it is getting so that it can properly handle it.

So, to answer the question:

Differences between isinstance() and type() in Python?

Allow me to demonstrate the difference:


Say you need to ensure a certain behavior if your function gets a certain kind of argument (a common use-case for constructors). If you check for type like this:

def foo(data):
    '''accepts a dict to construct something, string support in future'''
    if type(data) is not dict:
        # we're only going to test for dicts for now
        raise ValueError('only dicts are supported for now')

If we try to pass in a dict that is a subclass of dict (as we should be able to, if we're expecting our code to follow the principle of Liskov Substitution, that subtypes can be substituted for types) our code breaks!:

from collections import OrderedDict

foo(OrderedDict([('foo', 'bar'), ('fizz', 'buzz')]))

raises an error!

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in foo
ValueError: argument must be a dict


But if we use isinstance, we can support Liskov Substitution!:

def foo(a_dict):
    if not isinstance(a_dict, dict):
        raise ValueError('argument must be a dict')
    return a_dict

foo(OrderedDict([('foo', 'bar'), ('fizz', 'buzz')]))

returns OrderedDict([('foo', 'bar'), ('fizz', 'buzz')])

Abstract Base Classes

In fact, we can do even better. collections provides Abstract Base Classes that enforce minimal protocols for various types. In our case, if we only expect the Mapping protocol, we can do the following, and our code becomes even more flexible:

from collections import Mapping

def foo(a_dict):
    if not isinstance(a_dict, Mapping):
        raise ValueError('argument must be a dict')
    return a_dict

Response to comment:

It should be noted that type can be used to check against multiple classes using type(obj) in (A, B, C)

Yes, you can test for equality of types, but instead of the above, use the multiple bases for control flow, unless you are specifically only allowing those types:

isinstance(obj, (A, B, C))

The difference, again, is that isinstance supports subclasses that can be substituted for the parent without otherwise breaking the program, a property known as Liskov substitution.

Even better, though, invert your dependencies and don't check for specific types at all.


So since we want to support substituting subclasses, in most cases, we want to avoid type-checking with type and prefer type-checking with isinstance - unless you really need to know the precise class of an instance.

How to install a gem or update RubyGems if it fails with a permissions error

sudo gem update --system
sudo gem install (gemfile)

How to secure database passwords in PHP?

Previously we stored DB user/pass in a configuration file, but have since hit paranoid mode -- adopting a policy of Defence in Depth.

If your application is compromised, the user will have read access to your configuration file and so there is potential for a cracker to read this information. Configuration files can also get caught up in version control, or copied around servers.

We have switched to storing user/pass in environment variables set in the Apache VirtualHost. This configuration is only readable by root -- hopefully your Apache user is not running as root.

The con with this is that now the password is in a Global PHP variable.

To mitigate this risk we have the following precautions:

  • The password is encrypted. We extend the PDO class to include logic for decrypting the password. If someone reads the code where we establish a connection, it won't be obvious that the connection is being established with an encrypted password and not the password itself.
  • The encrypted password is moved from the global variables into a private variable The application does this immediately to reduce the window that the value is available in the global space.
  • phpinfo() is disabled. PHPInfo is an easy target to get an overview of everything, including environment variables.

Default value in an mvc view model

What will you have? You'll probably end up with a default search and a search that you load from somewhere. Default search requires a default constructor, so make one like Dismissile has already suggested.

If you load the search criteria from elsewhere, then you should probably have some mapping logic.

Keras input explanation: input_shape, units, batch_size, dim, etc

Input Dimension Clarified:

Not a direct answer, but I just realized the word Input Dimension could be confusing enough, so be wary:

It (the word dimension alone) can refer to:

a) The dimension of Input Data (or stream) such as # N of sensor axes to beam the time series signal, or RGB color channel (3): suggested word=> "InputStream Dimension"

b) The total number /length of Input Features (or Input layer) (28 x 28 = 784 for the MINST color image) or 3000 in the FFT transformed Spectrum Values, or

"Input Layer / Input Feature Dimension"

c) The dimensionality (# of dimension) of the input (typically 3D as expected in Keras LSTM) or (#RowofSamples, #of Senors, #of Values..) 3 is the answer.

"N Dimensionality of Input"

d) The SPECIFIC Input Shape (eg. (30,50,50,3) in this unwrapped input image data, or (30, 250, 3) if unwrapped Keras:

Keras has its input_dim refers to the Dimension of Input Layer / Number of Input Feature

model = Sequential()
model.add(Dense(32, input_dim=784))  #or 3 in the current posted example above

In Keras LSTM, it refers to the total Time Steps

The term has been very confusing, is correct and we live in a very confusing world!!

I find one of the challenge in Machine Learning is to deal with different languages or dialects and terminologies (like if you have 5-8 highly different versions of English, then you need to very high proficiency to converse with different speakers). Probably this is the same in programming languages too.


import java.util.ArrayList;
import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

public class Employee implements Serializable{
private static final long serialVersionUID = 1L;
private int id;
private String empName;

List<Address> addList=new ArrayList<Address>();

public int getId() {
    return id;
public void setId(int id) { = id;
public String getEmpName() {
    return empName;
public void setEmpName(String empName) {
    this.empName = empName;

public List<Address> getAddList() {
    return addList;

public void setAddList(List<Address> addList) {
    this.addList = addList;

We have two entities Employee and Address with One to Many relationship.

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

public class Address implements Serializable{

private static final long serialVersionUID = 1L;

private int address_id;
private String address;
Employee employee;

public int getAddress_id() {
    return address_id;
public void setAddress_id(int address_id) {
    this.address_id = address_id;
public String getAddress() {
    return address;
public void setAddress(String address) {
    this.address = address;

public Employee getEmployee() {
    return employee;
public void setEmployee(Employee employee) {
    this.employee = employee;

By this way we can implement inner join between two tables

import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;

public class Main {

public static void main(String[] args) {



private static void saveEmployee() {
    Employee employee=new Employee();
    Employee employee1=new Employee();
    Employee employee2=new Employee();
    Employee employee3=new Employee();

    Address address=new Address();
    Address address1=new Address();
    Address address2=new Address();
    Address address3=new Address();

    address.setAddress("1485,Sector 42 b");
    address1.setAddress("1485,Sector 42 c");
    address2.setAddress("1485,Sector 42 d");
    address3.setAddress("1485,Sector 42 a");




    Session session=HibernateUtil.getSessionFactory().openSession();


private static void retrieveEmployee() {

    String sqlQuery="select e from Employee e inner join e.addList";

    Session session=HibernateUtil.getSessionFactory().openSession();

    Query query=session.createQuery(sqlQuery);

    List<Employee> list=query.list();>{System.out.println(p.getEmpName());});     
    }catch(Exception e){

I have used Java 8 for loop for priting the names. Make sure you have jdk 1.8 with tomcat 8. Also add some more records for better understanding.

 public class HibernateUtil {
 private static SessionFactory sessionFactory ;
 static {
    Configuration configuration = new Configuration();

    configuration.setProperty("hibernate.connection.url", "jdbc:mysql://localhost:3306/hibernate");                                
    configuration.setProperty("hibernate.connection.username", "root");     
    configuration.setProperty("hibernate.connection.password", "root");
    configuration.setProperty("dialect", "org.hibernate.dialect.MySQLDialect");
    configuration.setProperty("", "update");
    configuration.setProperty("hibernate.show_sql", "true");
    configuration.setProperty(" hibernate.connection.pool_size", "10");

   // configuration
    StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties());
    sessionFactory = configuration.buildSessionFactory(;
public static SessionFactory getSessionFactory() {
    return sessionFactory;

How to get file path from OpenFileDialog and FolderBrowserDialog?

Use the Path class from System.IO. It contains useful calls for manipulating file paths, including GetDirectoryName which does what you want, returning the directory portion of the file path.

Usage is simple.

string directoryPath = System.IO.Path.GetDirectoryName(choofdlog.FileName);

Python 2,3 Convert Integer to "bytes" Cleanly

You can use the struct's pack:

In [11]: struct.pack(">I", 1)
Out[11]: '\x00\x00\x00\x01'

The ">" is the byte-order (big-endian) and the "I" is the format character. So you can be specific if you want to do something else:

In [12]: struct.pack("<H", 1)
Out[12]: '\x01\x00'

In [13]: struct.pack("B", 1)
Out[13]: '\x01'

This works the same on both python 2 and python 3.

Note: the inverse operation (bytes to int) can be done with unpack.

Error TF30063: You are not authorized to access ... \DefaultCollection

None of the current answers worked for me. I found a solution here.

The issue was that my previous credentials were cached by the Windows OS for the TFS server. While some people might have had success wiping out the AppData temp folders, that is not required.

You need to update the credentials through Control Panel on the Windows OS.

For me on Windows 10: Close VS. Go to Control Panel (with small icon view)-->User Accounts-->Manage your credentials (on the left column)-->Select "Windows Credentials"-->Scroll down to the "Generic Credentials" section and look for your TFS server connection. Expand the pull down and click "Edit". Enter in new network password. Reopen VS and everything should work again.

What is the format specifier for unsigned short int?

Try using the "%h" modifier:

scanf("%hu", &length);

ISO/IEC 9899:201x -

Specifies that a following d , i , o , u , x , X , or n conversion specifier applies to an argument with type pointer to short or unsigned short.

Change type of varchar field to integer: "cannot be cast automatically to type integer"

There is no implicit (automatic) cast from text or varchar to integer (i.e. you cannot pass a varchar to a function expecting integer or assign a varchar field to an integer one), so you must specify an explicit cast using ALTER TABLE ... ALTER COLUMN ... TYPE ... USING:

ALTER TABLE the_table ALTER COLUMN col_name TYPE integer USING (col_name::integer);

Note that you may have whitespace in your text fields; in that case, use:

ALTER TABLE the_table ALTER COLUMN col_name TYPE integer USING (trim(col_name)::integer);

to strip white space before converting.

This shoud've been obvious from an error message if the command was run in psql, but it's possible PgAdmin-III isn't showing you the full error. Here's what happens if I test it in psql on PostgreSQL 9.2:

=> CREATE TABLE test( x varchar );
=> insert into test(x) values ('14'), (' 42  ');
ERROR:  column "x" cannot be cast automatically to type integer
HINT:  Specify a USING expression to perform the conversion. 
=> ALTER TABLE test ALTER COLUMN x TYPE integer USING (trim(x)::integer);

Thanks @muistooshort for adding the USING link.

See also this related question; it's about Rails migrations, but the underlying cause is the same and the answer applies.

If the error still occurs, then it may be related not to column values, but indexes over this column or column default values might fail typecast. Indexes need to be dropped before ALTER COLUMN and recreated after. Default values should be changed appropriately.

How to remove square brackets in string using regex?

Use this regular expression to match square brackets or single quotes:


Replace with the empty string.


Convert an image (selected by path) to base64 string

Based on top voted answer, updated for C# 8. Following can be used out of the box. Added explicit System.Drawing before Image as one might be using that class from other namespace defaultly.

public static string ImagePathToBase64(string path)
    using System.Drawing.Image image = System.Drawing.Image.FromFile(path);
    using MemoryStream m = new MemoryStream();
    image.Save(m, image.RawFormat);
    byte[] imageBytes = m.ToArray();
    tring base64String = Convert.ToBase64String(imageBytes);
    return base64String;

How does strcmp() work?

I found this on web.

int strcmp(const char *s1, const char *s2)
    for ( ; *s1 == *s2; s1++, s2++)
        if (*s1 == '\0')
            return 0;
    return ((*(unsigned char *)s1 < *(unsigned char *)s2) ? -1 : +1);

dictionary update sequence element #0 has length 3; 2 is required

One of the fast ways to create a dict from equal-length tuples:

>>> t1 = (a,b,c,d)
>>> t2 = (1,2,3,4)
>>> dict(zip(t1, t2))
{'a':1, 'b':2, 'c':3, 'd':4, }

Switch statement for greater-than/less-than

In my case (color-coding a percentage, nothing performance-critical), I quickly wrote this:

function findColor(progress) {
    const thresholds = [30, 60];
    const colors = ["#90B451", "#F9A92F", "#90B451"];

    return colors.find((col, index) => {
        return index >= thresholds.length || progress < thresholds[index];

Replacing &nbsp; from javascript dom text node

I think when you define a function with "var foo = function() {...};", the function is only defined after that line. In other words, try this:

var replaceHtmlEntites = (function() {
  var translate_re = /&(nbsp|amp|quot|lt|gt);/g;
  var translate = {
    "nbsp": " ",
    "amp" : "&",
    "quot": "\"",
    "lt"  : "<",
    "gt"  : ">"
  return function(s) {
    return ( s.replace(translate_re, function(match, entity) {
      return translate[entity];
    }) );

var cleanText = text.replace(/^\xa0*([^\xa0]*)\xa0*$/g,"");
cleanText = replaceHtmlEntities(text);

Edit: Also, only use "var" the first time you declare a variable (you're using it twice on the cleanText variable).

Edit 2: The problem is the spelling of the function name. You have "var replaceHtmlEntites =". It should be "var replaceHtmlEntities ="

Why should a Java class implement comparable?

Here is a real life sample. Note that String also implements Comparable.

class Author implements Comparable<Author>{
    String firstName;
    String lastName;

    public int compareTo(Author other){
        // compareTo should return < 0 if this is supposed to be
        // less than other, > 0 if this is supposed to be greater than 
        // other and 0 if they are supposed to be equal
        int last = this.lastName.compareTo(other.lastName);
        return last == 0 ? this.firstName.compareTo(other.firstName) : last;


 * List the authors. Sort them by name so it will look good.
public List<Author> listAuthors(){
    List<Author> authors = readAuthorsFromFileOrSomething();
    return authors;

 * List unique authors. Sort them by name so it will look good.
public SortedSet<Author> listUniqueAuthors(){
    List<Author> authors = readAuthorsFromFileOrSomething();
    return new TreeSet<Author>(authors);

How to enable PHP short tags?

This can be done by enabling short_open_tag in php.ini:

1.To locate php.ini file,on comment line execute

 php --ini

you will get some thing like this,

Configuration File (php.ini) Path: /etc
Loaded Configuration File:         /etc/php.ini
Scan for additional .ini files in: /etc/php.d
Additional .ini files parsed:      /etc/php.d/curl.ini,

See 2nd line from the comment output.The file will be in the mentioned path.

2.Open php.ini file and find short_open_tag. By default it is in off change it to on.

3.Restart the server,execute this comment

service httpd restart


Close pre-existing figures in matplotlib when running from eclipse

See Bi Rico's answer for the general Eclipse case.

For anybody - like me - who lands here because you have lots of windows and you're struggling to close them all, just killing python can be effective, depending on your circumstances. It probably works under almost any circumstances - including with Eclipse.

I just spawned 60 plots from emacs (I prefer that to eclipse) and then I thought my script had exited. Running close('all') in my ipython window did not work for me because the plots did not come from ipython, so I resorted to looking for running python processes.

When I killed the interpreter running the script, then all 60 plots were closed - e.g.,

$ ps aux | grep python
rsage    11665  0.1  0.6 649904 109692 ?       SNl  10:54   0:03 /usr/bin/python3 /usr/bin/update-manager --no-update --no-focus-on-map
rsage    12111  0.9  0.5 390956 88212 pts/30   Sl+  11:08   0:17 /usr/bin/python /usr/bin/ipython -pylab
rsage    12410 31.8  2.4 576640 406304 pts/33  Sl+  11:38   0:06 python3 ../
rsage    12431  0.0  0.0   8860   648 pts/32   S+   11:38   0:00 grep python

$ kill 12410

Note that I did not kill my ipython/pylab, nor did I kill the update manager (killing the update manager is probably a bad idea)...

Inserting a blank table row with a smaller height

Just add the CSS rule (and the slightly improved mark-up) posted below and you should get the result that you're after.


    height: 10px !important; /* overwrites any other rules */
    background-color: #FFFFFF;


<tr class="blank_row">
    <td colspan="3"></td>

Since I have no idea what your current stylesheet looks like I added the !important property just in case. If possible, though, you should remove it as one rarely wants to rely on !important declarations in a stylesheet considering the big possibility that they will mess it up later on.

How to deep watch an array in angularjs?

Here is a comparison of the 3 ways you can watch a scope variable with examples:

$watch() is triggered by:

$scope.myArray = [];
$scope.myArray = null;
$scope.myArray = someOtherArray;

$watchCollection() is triggered by everything above AND:

$scope.myArray.push({}); // add element
$scope.myArray.splice(0, 1); // remove element
$scope.myArray[0] = {}; // assign index to different value

$watch(..., true) is triggered by EVERYTHING above AND:

$scope.myArray[0].someProperty = "someValue";


$watch() is the only one that triggers when an array is replaced with another array even if that other array has the same exact content.

For example where $watch() would fire and $watchCollection() would not:

$scope.myArray = ["Apples", "Bananas", "Orange" ];

var newArray = [];

$scope.myArray = newArray;

Below is a link to an example JSFiddle that uses all the different watch combinations and outputs log messages to indicate which "watches" were triggered:

Simple way to query connected USB devices info in Python?

For a system with legacy usb coming back and libusb-1.0, this approach will work to retrieve the various actual strings. I show the vendor and product as examples. It can cause some I/O, because it actually reads the info from the device (at least the first time, anyway.) Some devices don't provide this information, so the presumption that they do will throw an exception in that case; that's ok, so we pass.

import usb.core
import usb.backend.libusb1

busses = usb.busses()
for bus in busses:
    devices = bus.devices
    for dev in devices:
        if dev != None:
                xdev = usb.core.find(idVendor=dev.idVendor, idProduct=dev.idProduct)
                if xdev._manufacturer is None:
                    xdev._manufacturer = usb.util.get_string(xdev, xdev.iManufacturer)
                if xdev._product is None:
                    xdev._product = usb.util.get_string(xdev, xdev.iProduct)
                stx = '%6d %6d: '+str(xdev._manufacturer).strip()+' = '+str(xdev._product).strip()
                print stx % (dev.idVendor,dev.idProduct)

replacing text in a file with Python

The essential way is

  • read(),
  • data = data.replace() as often as you need and then
  • write().

If you read and write the whole data at once or in smaller parts is up to you. You should make it depend on the expected file size.

read() can be replaced with the iteration over the file object.

Append values to query string

You could use the HttpUtility.ParseQueryString method and an UriBuilder which provides a nice way to work with query string parameters without worrying about things like parsing, url encoding, ...:

string longurl = "";
var uriBuilder = new UriBuilder(longurl);
var query = HttpUtility.ParseQueryString(uriBuilder.Query);
query["action"] = "login1";
query["attempts"] = "11";
uriBuilder.Query = query.ToString();
longurl = uriBuilder.ToString();
// ""

Multiple commands on a single line in a Windows batch file

Can be achieved also with scriptrunner

ScriptRunner.exe -appvscript demoA.cmd arg1 arg2 -appvscriptrunnerparameters -wait -timeout=30 -rollbackonerror -appvscript demoB.ps1 arg3 arg4 -appvscriptrunnerparameters -wait -timeout=30 

Which also have some features as rollback , timeout and waiting.

How to get all the AD groups for a particular user?

This is how I list all the groups (direct and indirect) for a specific Distinguished Name:

The string 1.2.840.113556.1.4.1941 specifies LDAP_MATCHING_RULE_IN_CHAIN.

This rule is limited to filters that apply to the DN. This is a special "extended" match operator that walks the chain of ancestry in objects all the way to the root until it finds a match.

This method is 25 times faster than the UserPrincipal.GetGroups() method in my testing.

Note: The primary group (typically Domain Users) is not returned by this or GetGroups() method. To get the primary group name too, I've confirmed this method works.

Additionally, I found this list of LDAP filters extremely useful.

private IEnumerable<string> GetGroupsForDistinguishedName(DirectoryEntry domainDirectoryEntry, string distinguishedName)
    var groups = new List<string>();
    if (!string.IsNullOrEmpty(distinguishedName))
        var getGroupsFilterForDn = $"(&(objectCategory=group)(member:1.2.840.113556.1.4.1941:={distinguishedName}))";
        using (DirectorySearcher dirSearch = new DirectorySearcher(domainDirectoryEntry))
            dirSearch.Filter = getGroupsFilterForDn;

            using (var results = dirSearch.FindAll())
                foreach (SearchResult result in results)
                    if (result.Properties.Contains("name"))

    return groups;

Get all object attributes in Python?

Use the built-in function dir().

Check for internet connection with Swift

This is my version. Essentially it doesn't bring anything new. I bound it to UIDevice.

import UIKit
import SystemConfiguration

extension UIDevice {

    open class var isConnectedToNetwork: Bool {
        get {
            var zeroAddress = sockaddr_in()
            zeroAddress.sin_len = UInt8(MemoryLayout.size(ofValue: zeroAddress))
            zeroAddress.sin_family = sa_family_t(AF_INET)

                let defaultRouteReachability: SCNetworkReachability = withUnsafePointer(to: &zeroAddress, {
                    $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                        SCNetworkReachabilityCreateWithAddress(nil, $0)
                var flags: SCNetworkReachabilityFlags = SCNetworkReachabilityFlags() as SCNetworkReachabilityFlags?,
                SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags)
                else { return false }

            return flags.contains(.reachable) && !flags.contains(.connectionRequired)


print("Network status availability: " + ( UIDevice.isConnectedToNetwork ? "true" : "false" ))

converting numbers in to words C#

public static string NumberToWords(int number)
    if (number == 0)
        return "zero";

    if (number < 0)
        return "minus " + NumberToWords(Math.Abs(number));

    string words = "";

    if ((number / 1000000) > 0)
        words += NumberToWords(number / 1000000) + " million ";
        number %= 1000000;

    if ((number / 1000) > 0)
        words += NumberToWords(number / 1000) + " thousand ";
        number %= 1000;

    if ((number / 100) > 0)
        words += NumberToWords(number / 100) + " hundred ";
        number %= 100;

    if (number > 0)
        if (words != "")
            words += "and ";

        var unitsMap = new[] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" };
        var tensMap = new[] { "zero", "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety" };

        if (number < 20)
            words += unitsMap[number];
            words += tensMap[number / 10];
            if ((number % 10) > 0)
                words += "-" + unitsMap[number % 10];

    return words;

Do you get charged for a 'stopped' instance on EC2?

Short answer - no.

You will only be charged for the time that your instance is up and running, in hour increments. If you are using other services in conjunction you may be charged for those but it would be separate from your server instance.

How do you handle multiple submit buttons in ASP.NET MVC Framework?

I've tried to make a synthesis of all solutions and created a [ButtenHandler] attribute that makes it easy to handle multiple buttons on a form.

I've described it on CodeProject Multiple parameterized (localizable) form buttons in ASP.NET MVC.

To handle the simple case of this button:

<button type="submit" name="AddDepartment">Add Department</button>

You'll have something like the following action method:

public ActionResult AddDepartment(Company model)
    model.Departments.Add(new Department());
    return View(model);

Notice how the name of the button matches the name of the action method. The article also describes how to have buttons with values and buttons with indexes.

Postgres: How to do Composite keys?

Your compound PRIMARY KEY specification already does what you want. Omit the line that's giving you a syntax error, and omit the redundant CONSTRAINT (already implied), too:

               question_id INTEGER NOT NULL,
               tag_id SERIAL NOT NULL,
               tag1 VARCHAR(20),
               tag2 VARCHAR(20),
               tag3 VARCHAR(20),
               PRIMARY KEY(question_id, tag_id)

NOTICE:  CREATE TABLE will create implicit sequence "tags_tag_id_seq" for serial column "tags.tag_id"
    NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "tags_pkey" for table "tags"
    pg=> \d tags
                                         Table "public.tags"
       Column    |         Type          |                       Modifiers       
     question_id | integer               | not null
     tag_id      | integer               | not null default nextval('tags_tag_id_seq'::regclass)
     tag1        | character varying(20) |
     tag2        | character varying(20) |
     tag3        | character varying(20) |
        "tags_pkey" PRIMARY KEY, btree (question_id, tag_id)

How do I combine 2 select statements into one?

select Status, * from WorkItems t1
where  exists (select 1 from workitems t2 where t1.TextField01=t2.TextField01 AND (BoolField05=1) )
AND TimeStamp=(select max(t2.TimeStamp) from workitems t2 where t2.TextField01=t1.TextField01) 
AND TimeStamp>'2009-02-12 18:00:00'


select 'DELETED', * from WorkItems t1
where  exists (select 1 from workitems t2 where t1.TextField01=t2.TextField01 AND (BoolField05=1) )
AND TimeStamp=(select max(t2.TimeStamp) from workitems t2 where t2.TextField01=t1.TextField01) 
AND TimeStamp>'2009-02-12 18:00:00'
AND NOT (BoolField05=1)

Perhaps that'd do the trick. I can't test it from here though, and I'm not sure what version of SQL you're working against.

Getting visitors country from their IP

Would that be acceptable ? pure PHP

$country = geoip_country_code_by_name($_SERVER['REMOTE_ADDR']);
print $country;