Programs & Examples On #Recoverymodel

"Char cannot be dereferenced" error

A char doesn't have any methods - it's a Java primitive. You're looking for the Character wrapper class.

The usage would be:

if(Character.isLetter(ch)) { //... }

Iterate through every file in one directory

This is my favorite method for being easy to read:

Dir.glob("*/*.txt") do |my_text_file|
  puts "working on: #{my_text_file}..."

And you can even extend this to work on all files in subdirs:

Dir.glob("**/*.txt") do |my_text_file| # note one extra "*"
  puts "working on: #{my_text_file}..."

Set database from SINGLE USER mode to MULTI USER

I have solved the problem easily

  1. Right click on database name rename it

  2. After changing, right click on database name --> properties --> options --> go to bottom of scrolling RestrictAccess (SINGLE_USER to MULTI_USER)

  3. Now again you can rename database as your old name.

kill a process in bash

try kill -9 {processID}

To find the process ID you can use ps -ef | grep gedit

Repair all tables in one go

You may need user name and password:

mysqlcheck -A --auto-repair -uroot -p

You will be prompted for password.

mysqlcheck -A --auto-repair -uroot -p{{password here}}

If you want to put in cron, BUT your password will be visible in plain text!

Is there an XSLT name-of element?

<xsl:for-each select="person">
  <xsl:for-each select="*">
    <xsl:value-of select="local-name()"/> : <xsl:value-of select="."/>

Is Unit Testing worth the effort?

Unit-testing is well worth the initial investment. Since starting to use unit-testing a couple of years ago, I've found some real benefits:

  • regression testing removes the fear of making changes to code (there's nothing like the warm glow of seeing code work or explode every time a change is made)
  • executable code examples for other team members (and yourself in six months time..)
  • merciless refactoring - this is incredibly rewarding, try it!

Code snippets can be a great help in reducing the overhead of creating tests. It isn't difficult to create snippets that enable the creation of a class outline and an associated unit-test fixture in seconds.

How can I export Excel files using JavaScript?

To answer your question with a working example:

<script type="text/javascript">
function DownloadJSON2CSV(objArray)
    var array = typeof objArray != 'object' ? JSON.parse(objArray) : objArray;

    var str = '';

    for (var i = 0; i < array.length; i++) {
        var line = new Array();

        for (var index in array[i]) {
           line.push('"' + array[i][index] + '"');

        str += line.join(';');
        str += '\r\n';
    } "data:text/csv;charset=utf-8," + encodeURIComponent(str));

How can I send an xml body using requests library?

Just send xml bytes directly:

#!/usr/bin/env python2
# -*- coding: utf-8 -*-
import requests

xml = """<?xml version='1.0' encoding='utf-8'?>
headers = {'Content-Type': 'application/xml'} # set what your server accepts
print'', data=xml, headers=headers).text


  "origin": "x.x.x.x",
  "files": {},
  "form": {},
  "url": "",
  "args": {},
  "headers": {
    "Content-Length": "48",
    "Accept-Encoding": "identity, deflate, compress, gzip",
    "Connection": "keep-alive",
    "Accept": "*/*",
    "User-Agent": "python-requests/0.13.9 CPython/2.7.3 Linux/3.2.0-30-generic",
    "Host": "",
    "Content-Type": "application/xml"
  "json": null,
  "data": "<?xml version='1.0' encoding='utf-8'?>\n<a>\u0431</a>"

Can I change the checkbox size using CSS?

The problem is Firefox doesn't listen to width and height. Disable that and your good to go.

input[type=checkbox] {_x000D_
    width: 25px;_x000D_
    height: 25px;_x000D_
    -moz-appearance: none;_x000D_
<label><input type="checkbox"> Test</label>

When I catch an exception, how do I get the type, file, and line number?

Here is an example of showing the line number of where exception takes place.

import sys
except Exception as e:
    print('Error on line {}'.format(sys.exc_info()[-1].tb_lineno), type(e).__name__, e)

print('And the rest of program continues')

"Integer number too large" error message for 600851475143

Append suffix L: 23423429L.

By default, java interpret all numeral literals as 32-bit integer values. If you want to explicitely specify that this is something bigger then 32-bit integer you should use suffix L for long values.

Laravel 4: how to run a raw SQL?

In the Laravel 4 manual - it talks about doing raw commands like this:

DB::select(DB::raw('RENAME TABLE photos TO images'));

edit: I just found this in the Laravel 4 documentation which is probably better:

DB::statement('drop table users');

Update: In Laravel 4.1 (maybe 4.0 - I'm not sure) - you can also do this for a raw Where query:

$users = User::whereRaw('age > ? and votes = 100', array(25))->get();

Further Update If you are specifically looking to do a table rename - there is a schema command for that - see Mike's answer below for that.

Git diff -w ignore whitespace only at start & end of lines

This is an old question, but is still regularly viewed/needed. I want to post to caution readers like me that whitespace as mentioned in the OP's question is not the same as Regex's definition, to include newlines, tabs, and space characters -- Git asks you to be explicit. See some options here:

As stated, git diff -b or git diff --ignore-space-change will ignore spaces at line ends. If you desire that setting to be your default behavior, the following line adds that intent to your .gitconfig file, so it will always ignore the space at line ends:

git config --global core.whitespace trailing-space

In my case, I found this question because I was interested in ignoring "carriage return whitespace differences", so I needed this:

git diff --ignore-cr-at-eol or git config --global core.whitespace cr-at-eol from here.

You can also make it the default only for that repo by omitting the --global parameter, and checking in the settings file for that repo. For the CR problem I faced, it goes away after check-in if warncrlf or autocrlf = true in the [core] section of the .gitconfig file.

Singleton in Android

It is simple, as a java, Android also supporting singleton. -

Singleton is a part of Gang of Four design pattern and it is categorized under creational design patterns.

-> Static member : This contains the instance of the singleton class.

-> Private constructor : This will prevent anybody else to instantiate the Singleton class.

-> Static public method : This provides the global point of access to the Singleton object and returns the instance to the client calling class.

  1. create private instance
  2. create private constructor
  3. use getInstance() of Singleton class

    public class Logger{
    private static Logger   objLogger;
    private Logger(){
            //ToDo here
    public static Logger getInstance()
        if (objLogger == null)
          objLogger = new Logger();
       return objLogger;

while use singleton -


How to modify values of JsonObject / JsonArray directly?

It's actually all in the documentation.
JSONObject and JSONArray can both be used to replace the standard data structure.
To implement a setter simply call a remove(String name) before a put(String name, Object value).

Here's an simple example:

public class BasicDB {

private JSONObject jData = new JSONObject;

public BasicDB(String username, String tagline) {
    try {
        jData.put("username", username);
        jData.put("tagline" , tagline);
    } catch (JSONException e) {
        // TODO Auto-generated catch block

public String getUsername () { 
    String ret = null;
    try {
        ret = jData.getString("username");
    } catch (JSONException e) {
    // TODO Auto-generated catch block
    return ret;

public void setUsername (String username) { 
    try {
        jData.put("username" , username);
    } catch (JSONException e) {
        // TODO Auto-generated catch block

public String getTagline () {
    String ret = null;
    try {
        ret = jData.getString("tagline");
    } catch (JSONException e) {
    // TODO Auto-generated catch block
    return ret;

How do I make a list of data frames?

If you have a large number of sequentially named data frames you can create a list of the desired subset of data frames like this:

d1 <- data.frame(y1=c(1,2,3), y2=c(4,5,6))
d2 <- data.frame(y1=c(3,2,1), y2=c(6,5,4))
d3 <- data.frame(y1=c(6,5,4), y2=c(3,2,1))
d4 <- data.frame(y1=c(9,9,9), y2=c(8,8,8))

my.list <- list(d1, d2, d3, d4)

my.list2 <- lapply(paste('d', seq(2,4,1), sep=''), get)

where my.list2 returns a list containing the 2nd, 3rd and 4th data frames.

  y1 y2
1  3  6
2  2  5
3  1  4

  y1 y2
1  6  3
2  5  2
3  4  1

  y1 y2
1  9  8
2  9  8
3  9  8

Note, however, that the data frames in the above list are no longer named. If you want to create a list containing a subset of data frames and want to preserve their names you can try this:

list.function <-  function() { 

     d1 <- data.frame(y1=c(1,2,3), y2=c(4,5,6))
     d2 <- data.frame(y1=c(3,2,1), y2=c(6,5,4))
     d3 <- data.frame(y1=c(6,5,4), y2=c(3,2,1))
     d4 <- data.frame(y1=c(9,9,9), y2=c(8,8,8))

     sapply(paste('d', seq(2,4,1), sep=''), get, environment(), simplify = FALSE) 

my.list3 <- list.function()

which returns:

> my.list3
  y1 y2
1  3  6
2  2  5
3  1  4

  y1 y2
1  6  3
2  5  2
3  4  1

  y1 y2
1  9  8
2  9  8
3  9  8

> str(my.list3)
List of 3
 $ d2:'data.frame':     3 obs. of  2 variables:
  ..$ y1: num [1:3] 3 2 1
  ..$ y2: num [1:3] 6 5 4
 $ d3:'data.frame':     3 obs. of  2 variables:
  ..$ y1: num [1:3] 6 5 4
  ..$ y2: num [1:3] 3 2 1
 $ d4:'data.frame':     3 obs. of  2 variables:
  ..$ y1: num [1:3] 9 9 9
  ..$ y2: num [1:3] 8 8 8

> my.list3[[1]]
  y1 y2
1  3  6
2  2  5
3  1  4

> my.list3$d4
  y1 y2
1  9  8
2  9  8
3  9  8

python variable NameError

In addition to the missing quotes around 100Mb in the last else, you also want to quote the constants in your if-statements if tSizeAns == "1":, because raw_input returns a string, which in comparison with an integer will always return false.

However the missing quotes are not the reason for the particular error message, because it would result in an syntax error before execution. Please check your posted code. I cannot reproduce the error message.

Also if ... elif ... else in the way you use it is basically equivalent to a case or switch in other languages and is neither less readable nor much longer. It is fine to use here. One other way that might be a good idea to use if you just want to assign a value based on another value is a dictionary lookup:

tSize = {"1": "100Mb", "2": "200Mb"}[tSizeAns] 

This however does only work as long as tSizeAns is guaranteed to be in the range of tSize. Otherwise you would have to either catch the KeyError exception or use a defaultdict:

lookup = {"1": "100Mb", "2": "200Mb"} try:     tSize = lookup[tSizeAns] except KeyError:     tSize = "100Mb" 


from collections import defaultdict  [...]  lookup = defaultdict(lambda: "100Mb", {"1": "100Mb", "2": "200Mb"}) tSize = lookup[tSizeAns] 

In your case I think these methods are not justified for two values. However you could use the dictionary to construct the initial output at the same time.

How to find my php-fpm.sock?

When you look up your php-fpm.conf

example location:
cat /usr/src/php/sapi/fpm/php-fpm.conf

you will see, that you need to configure the PHP FastCGI Process Manager to actually use Unix sockets. Per default, the listen directive` is set up to listen on a TCP socket on one port. If there's no Unix socket defined, you won't find a Unix socket file.

; The address on which to accept FastCGI requests.
; Valid syntaxes are:
;   ''    - to listen on a TCP socket to a specific IPv4 address on
;                            a specific port;
;   '[ip:6:addr:ess]:port' - to listen on a TCP socket to a specific IPv6 address on
;                            a specific port;
;   'port'                 - to listen on a TCP socket to all IPv4 addresses on a
;                            specific port;
;   '[::]:port'            - to listen on a TCP socket to all addresses
;                            (IPv6 and IPv4-mapped) on a specific port;
;   '/path/to/unix/socket' - to listen on a unix socket.
; Note: This value is mandatory.
listen =

Returning the product of a list

Without using lambda:

from operator import mul
reduce(mul, list, 1)

it is better and faster. With python 2.7.5

from operator import mul
import numpy as np
import numexpr as ne
# from functools import reduce # python3 compatibility

a = range(1, 101)
%timeit reduce(lambda x, y: x * y, a)   # (1)
%timeit reduce(mul, a)                  # (2)
%timeit                      # (3)
%timeit ne.evaluate("prod(a)")          # (4)

In the following configuration:

a = range(1, 101)  # A
a = np.array(a)    # B
a = np.arange(1, 1e4, dtype=int) #C
a = np.arange(1, 1e5, dtype=float) #D

Results with python 2.7.5

       |     1     |     2     |     3     |     4     |
 A       20.8 µs     13.3 µs     22.6 µs     39.6 µs     
 B        106 µs     95.3 µs     5.92 µs     26.1 µs
 C       4.34 ms     3.51 ms     16.7 µs     38.9 µs
 D       46.6 ms     38.5 ms      180 µs      216 µs

Result: is the fastest one, if you use np.array as data structure (18x for small array, 250x for large array)

with python 3.3.2:

       |     1     |     2     |     3     |     4     |
 A       23.6 µs     12.3 µs     68.6 µs     84.9 µs     
 B        133 µs      107 µs     7.42 µs     27.5 µs
 C       4.79 ms     3.74 ms     18.6 µs     40.9 µs
 D       48.4 ms     36.8 ms      187 µs      214 µs

Is python 3 slower?

C: scanf to array

if (array[0]=1) should be if (array[0]==1).

The same with else if (array[0]=2).

Note that the expression of the assignment returns the assigned value, in this case if (array[0]=1) will be always true, that's why the code below the if-statement will be always executed if you don't change the = to ==.

= is the assignment operator, you want to compare, not to assign. So you need ==.

Another thing, if you want only one integer, why are you using array? You might want also to scanf("%d", &array[0]);

Escape quotes in JavaScript

This is how I do it, basically str.replace(/[\""]/g, '\\"').

var display = document.getElementById('output');_x000D_
var str = 'class="whatever-foo__input" id="node-key"';_x000D_
display.innerHTML = str.replace(/[\""]/g, '\\"');_x000D_
//will return class=\"whatever-foo__input\" id=\"node-key\"
<span id="output"></span>

Mysql 1050 Error "Table already exists" when in fact, it does not

Was trying to import a backup sql file but was getting the error; 1050 "Table already exists"

My setup was:

  • Windows 7
  • Mysql 5.5.16


  1. Changed the server engine from InnoDB to MyISAM
  2. Using phpMyAdmin Deleted the database I was trying to import to
  3. Restarted the mysql service
  4. Tried the re-importation and it worked

Jenkins - passing variables between jobs?

I think the answer above needs some update:

I was trying to create a dynamic directory to store my upstream build artifacts so I wanted to pass my upstream job build number to downstream job I tried the above steps but couldn't make it work. Here is how it worked:

  1. I copied the artifacts from my current job using copy artifacts plugin.
  2. In post build action of upstream job I added the variable like "SOURCE_BUILD_NUMBER=${BUILD_NUMBER}" and configured it to trigger the downstream job.
  3. Everything worked except that my downstream job was not able to get $SOURCE_BUILD_NUMBER to create the directory.
  4. So I found out that to use this variable I have to define the same variable in down stream job as a parameter variable like in this picture below:

enter image description here

This is because the new version of jenkins require's you to define the variable in the downstream job as well. I hope it's helpful.

How to get package name from anywhere?

Use: BuildConfig.APPLICATION_ID to get PACKAGE NAME anywhere( ie; services, receiver, activity, fragment, etc )

Example: String PackageName = BuildConfig.APPLICATION_ID; invalid stream header: 7371007E

when I send only one object from the client to server all works well.

when I attempt to send several objects one after another on the same stream I get StreamCorruptedException.

Actually, your client code is writing one object to the server and reading multiple objects from the server. And there is nothing on the server side that is writing the objects that the client is trying to read.

Is there a way to programmatically scroll a scroll view to a specific edit text?

Another varition would be:

scrollView.postDelayed(new Runnable()
    public void run()
        scrollView.smoothScrollTo(0, img_transparent.getTop());
}, 2000);

or you can use the post() method.

SQL Server stored procedure parameters

You are parsing wrong parameter you passing @TaskName = and @ID instead of @TaskName = .SP need only one parameter.

Including non-Python files with

create in the project root with recursive-include to the required directory or include with the file name.

include LICENSE
include README.rst
recursive-include package/static *
recursive-include package/templates *

documentation can be found here

JSON forEach get Key and Value

Assuming that obj is a pre-constructed object (and not a JSON string), you can achieve this with the following:

   console.log(key + '=' + obj[key]);

How do you post data with a link

We should make everything easier for everyone because you can simply combine JS to PHP Combining PHP and JS is pretty easy.

$house_number = HOUSE_NUMBER;
echo "<script type='text/javascript'>document.forms[0].house_number.value = $house_number; document.forms[0].submit();</script>";

Or a somewhat safer way

$house_number = HOUSE_NUMBER;
echo "<script type='text/javascript'>document.forms[0].house_number.value = " . $house_number . "; document.forms[0].submit();</script>";

How to delete multiple pandas (python) dataframes from memory to save RAM?

This will delete the dataframe and will release the RAM/memory

del [[df_1,df_2]]

the data-frame will be explicitly set to null

in the above statements

Firstly, the self reference of the dataframe is deleted meaning the dataframe is no longer available to python there after all the references of the dataframe is collected by garbage collector (gc.collect()) and then explicitly set all the references to empty dataframe.

more on the working of garbage collector is well explained in

Remove array element based on object property

One possibility:

myArray = myArray.filter(function( obj ) {
    return obj.field !== 'money';

Please note that filter creates a new array. Any other variables referring to the original array would not get the filtered data although you update your original variable myArray with the new reference. Use with caution.

How to replace a whole line with sed?

Try this:

sed "s/aaa=.*/aaa=xxx/g"

Read binary file as string in Ruby

Ruby have binary reading

data = IO.binread(path/filaname)

or if less than Ruby 1.9.2

data =

Android getting value from selected radiobutton

Radiogroup rgteam;
String team;
rgteam.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
        public void onCheckedChanged(RadioGroup group, @IdRes int checkedId) {
            RadioButton rb= (RadioButton) findViewById(checkedId);
            team = rb.getText().toString();

How to "wait" a Thread in Android

You can try this one it is short :)


It will sleep for 7 sec look at documentation

How to detect internet speed in JavaScript?

It's possible to some extent but won't be really accurate, the idea is load image with a known file size then in its onload event measure how much time passed until that event was triggered, and divide this time in the image file size.

Example can be found here: Calculate speed using javascript

Test case applying the fix suggested there:

var imageAddr = ""; _x000D_
var downloadSize = 4995374; //bytes_x000D_
function ShowProgressMessage(msg) {_x000D_
    if (console) {_x000D_
        if (typeof msg == "string") {_x000D_
        } else {_x000D_
            for (var i = 0; i < msg.length; i++) {_x000D_
    var oProgress = document.getElementById("progress");_x000D_
    if (oProgress) {_x000D_
        var actualHTML = (typeof msg == "string") ? msg : msg.join("<br />");_x000D_
        oProgress.innerHTML = actualHTML;_x000D_
function InitiateSpeedDetection() {_x000D_
    ShowProgressMessage("Loading the image, please wait...");_x000D_
    window.setTimeout(MeasureConnectionSpeed, 1);_x000D_
};    _x000D_
if (window.addEventListener) {_x000D_
    window.addEventListener('load', InitiateSpeedDetection, false);_x000D_
} else if (window.attachEvent) {_x000D_
    window.attachEvent('onload', InitiateSpeedDetection);_x000D_
function MeasureConnectionSpeed() {_x000D_
    var startTime, endTime;_x000D_
    var download = new Image();_x000D_
    download.onload = function () {_x000D_
        endTime = (new Date()).getTime();_x000D_
    download.onerror = function (err, msg) {_x000D_
        ShowProgressMessage("Invalid image, or error downloading");_x000D_
    startTime = (new Date()).getTime();_x000D_
    var cacheBuster = "?nnn=" + startTime;_x000D_
    download.src = imageAddr + cacheBuster;_x000D_
    function showResults() {_x000D_
        var duration = (endTime - startTime) / 1000;_x000D_
        var bitsLoaded = downloadSize * 8;_x000D_
        var speedBps = (bitsLoaded / duration).toFixed(2);_x000D_
        var speedKbps = (speedBps / 1024).toFixed(2);_x000D_
        var speedMbps = (speedKbps / 1024).toFixed(2);_x000D_
            "Your connection speed is:", _x000D_
            speedBps + " bps", _x000D_
            speedKbps + " kbps", _x000D_
            speedMbps + " Mbps"_x000D_
<h1 id="progress">JavaScript is turned off, or your browser is realllllly slow</h1>

Quick comparison with "real" speed test service showed small difference of 0.12 Mbps when using big picture.

To ensure the integrity of the test, you can run the code with Chrome dev tool throttling enabled and then see if the result matches the limitation. (credit goes to user284130 :))

Important things to keep in mind:

  1. The image being used should be properly optimized and compressed. If it isn't, then default compression on connections by the web server might show speed bigger than it actually is. Another option is using uncompressible file format, e.g. jpg. (thanks Rauli Rajande for pointing this out and Fluxine for reminding me)

  2. The cache buster mechanism described above might not work with some CDN servers, which can be configured to ignore query string parameters, hence better setting cache control headers on the image itself. (thanks orcaman for pointing this out))

Label python data points on plot

How about print (x, y) at once.

from matplotlib import pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111)

A = -0.75, -0.25, 0, 0.25, 0.5, 0.75, 1.0
B = 0.73, 0.97, 1.0, 0.97, 0.88, 0.73, 0.54

for xy in zip(A, B):                                       # <--
    ax.annotate('(%s, %s)' % xy, xy=xy, textcoords='data') # <--


enter image description here

@HostBinding and @HostListener: what do they do and what are they for?

DECORATORS: to dynamically change the behaviour of DOM elements

@HostBinding: Dynamic binding custom logic to Host element

 activeClass = false;

@HostListen: To Listen to events on Host element

    this.activeClass = !this.activeClass;

Host Element:

  <button type='button' class="btn btn-primary btn-sm" appHost>Host</button>

How to filter an array of objects based on values in an inner array with jq?

Here is another solution which uses any/2

map(select(any(.Names[]; contains("data"))|not)|.Id)[]

with the sample data and the -r option it produces


Can we install Android OS on any Windows Phone and vice versa, and same with iPhone and vice versa?

Android needs to be compiled for every hardware plattform / every device model seperatly with the specific drivers etc. If you manage to do that you need also break the security arrangements every manufacturer implements to prevent the installation of other software - these are also different between each model / manufacturer. So it is possible at in theory, but only there :-)

VBA general way for pulling data out of SAP

This all depends on what sort of access you have to your SAP system. An ABAP program that exports the data and/or an RFC that your macro can call to directly get the data or have SAP create the file is probably best.

However as a general rule people looking for this sort of answer are looking for an immediate solution that does not require their IT department to spend months customizing their SAP system.

In that case you probably want to use SAP GUI Scripting. SAP GUI scripting allows you to automate the Windows SAP GUI in much the same way as you automate Excel. In fact you can call the SAP GUI directly from an Excel macro. Read up more on it here. The SAP GUI has a macro recording tool much like Excel does. It records macros in VBScript which is nearly identical to Excel VBA and can usually be copied and pasted into an Excel macro directly.

Example Code

Here is a simple example based on a SAP system I have access to.

Public Sub SimpleSAPExport()
  Set SapGuiAuto  = GetObject("SAPGUI") 'Get the SAP GUI Scripting object
  Set SAPApp = SapGuiAuto.GetScriptingEngine 'Get the currently running SAP GUI 
  Set SAPCon = SAPApp.Children(0) 'Get the first system that is currently connected
  Set session = SAPCon.Children(0) 'Get the first session (window) on that connection

  'Start the transaction to view a table
  session.StartTransaction "SE16"

  'Select table T001
  session.findById("wnd[0]/usr/ctxtDATABROWSE-TABLENAME").Text = "T001"

  'Set our selection criteria
  session.findById("wnd[0]/usr/txtMAX_SEL").text = "2"

  'Click the export to file button

  'Choose the export format

  'Choose the export filename
  session.findById("wnd[1]/usr/ctxtDY_FILENAME").text = "test.txt"
  session.findById("wnd[1]/usr/ctxtDY_PATH").text = "C:\Temp\"

  'Export the file
End Sub

Script Recording

To help find the names of elements such aswnd[1]/tbar[0]/btn[0] you can use script recording. Click the customize local layout button, it probably looks a bit like this: Customize Local Layout
Then find the Script Recording and Playback menu item.
Script Recording and Playback
Within that the More button allows you to see/change the file that the VB Script is recorded to. The output format is a bit messy, it records things like selecting text, clicking inside a text field, etc.

Edit: Early and Late binding

The provided script should work if copied directly into a VBA macro. It uses late binding, the line Set SapGuiAuto = GetObject("SAPGUI") defines the SapGuiAuto object.

If however you want to use early binding so that your VBA editor might show the properties and methods of the objects you are using, you need to add a reference to sapfewse.ocx in the SAP GUI installation folder.

AngularJS: Uncaught Error: [$injector:modulerr] Failed to instantiate module?

For people who find this old posting on the web by searching for the error message, there is another possible cause of the problem.

You could just have a typo in your call to the script, even if you have already done the things described in the other excellent answer. So check to make sure you can used the right spelling in your script tags.

Run CRON job everyday at specific time

you can write multiple lines in case of different minutes, for example you want to run at 10:01 AM and 2:30 PM

1 10 * * * php -f /var/www/package/index.php controller function

30 14 * * * php -f /var/www/package/index.php controller function

but the following is the best solution for running cron multiple times in a day as minutes are same, you can mention hours like 10,30 .

30 10,14 * * * php -f /var/www/package/index.php controller function

How to set the custom border color of UIView programmatically?

swift 3.0

self.uiTextView.layer.borderWidth = 0.5
    self.txtItemShortDes.layer.borderColor = UIColor(red:205.0/255.0, green:205.0/255.0, blue:205.0/255.0, alpha: 1.0).cgColor

How to delete a certain row from mysql table with same column values?

You need to specify the number of rows which should be deleted. In your case (and I assume that you only want to keep one) this can be done like this:

DELETE FROM your_table WHERE id_users=1 AND id_product=2
LIMIT (SELECT COUNT(*)-1 FROM your_table WHERE id_users=1 AND id_product=2)


It means that the delegate you pass is executed on the thread that created the Control object (which is the UI thread).

You need to call this method when your application is multi-threaded and you want do some UI operation from a thread other than the UI thread, because if you just try to call a method on a Control from a different thread you'll get a System.InvalidOperationException.

Radio/checkbox alignment in HTML/CSS

I wouldn't use tables for this at all. CSS can easily do this.

I would do something like this:

   <p class="clearfix">
      <input id="option1" type="radio" name="opt" />
      <label for="option1">Option 1</label>

p { margin: 0px 0px 10px 0px; }
input { float: left; width: 50px; }
label { margin: 0px 0px 0px 10px; float: left; }

Note: I have used the clearfix class from :

.clearfix:after {
    content: ".";
    display: block;
    height: 0;
    clear: both;
    visibility: hidden;

.clearfix {display: inline-block;}

/* Hides from IE-mac \*/
* html .clearfix {height: 1%;}
.clearfix {display: block;}
/* End hide from IE-mac */

How to hide axes and gridlines in Matplotlib (python)

Turn the axes off with:


And gridlines with:


With Spring can I make an optional path variable?

You can't have optional path variables, but you can have two controller methods which call the same service code:

@RequestMapping(value = "/json/{type}", method = RequestMethod.GET)
public @ResponseBody TestBean typedTestBean(
        HttpServletRequest req,
        @PathVariable String type,
        @RequestParam("track") String track) {
    return getTestBean(type);

@RequestMapping(value = "/json", method = RequestMethod.GET)
public @ResponseBody TestBean testBean(
        HttpServletRequest req,
        @RequestParam("track") String track) {
    return getTestBean();

Why does Vim save files with a ~ extension?

To turn off those files, just add these lines to .vimrc (vim configuration file on unix based OS):

set nobackup       #no backup files
set nowritebackup  #only in case you don't want a backup file while editing
set noswapfile     #no swap files

EditText onClickListener in Android

Here is what worked for me

Set editable to false

<EditText android:id="@+id/dob"
android:hint="Date of Birth"


Then add an event listener for OnFocusChange

private  View.OnFocusChangeListener onFocusChangeDOB= new View.OnFocusChangeListener() {

 public void onFocusChange(View v, boolean hasFocus) {
   if (hasFocus){

Hide element by class in pure Javascript

<script type="text/javascript">




<script type="text/javascript">



Posting form to different MVC post action depending on the clicked submit button


ActionNameSelectorAttribute mentioned in

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

  2. ASP.Net MVC 4 Form with 2 submit buttons/actions


Reference: dotnet-tricks - Handling multiple submit buttons on the same form - MVC Razor

Second Approach

Adding a new Form for handling Cancel button click. Now, on Cancel button click we will post the second form and will redirect to the home page.

Third Approach: Client Script

<button name="ClientCancel" type="button" 
    onclick=" document.location.href = $('#cancelUrl').attr('href');">Cancel (Client Side)
<a id="cancelUrl" href="@Html.AttributeEncode(Url.Action("Index", "Home"))" 

How to convert an NSTimeInterval (seconds) into minutes

Since it's essentially a double...

Divide by 60.0 and extract the integral part and the fractional part.

The integral part will be the whole number of minutes.

Multiply the fractional part by 60.0 again.

The result will be the remaining seconds.

String length in bytes in JavaScript

For simple UTF-8 encoding, with slightly better compatibility than TextEncoder, Blob does the trick. Won't work in very old browsers though.

new Blob([""]).size; // -> 4  

CSS selector for disabled input type="submit"

As said by jensgram, IE6 does not support attribute selector. You could add a class="disabled" to select the disabled inputs so that this can work in IE6.

Extend contigency table with proportions (percentages)

I made this for when doing aggregate functions and similar <- function(x) {
        denom <- length(x);
        num <- sum(x);
        percentage <- num/denom;
        else NA

Reportviewer tool missing in visual studio 2017 RC

Update: this answer works with both ,Visual Sudio 2017 and 2019

For me it worked by the following three steps:

  1. Updating Visual Studio to the latest build.
  2. Adding Report / Report Wizard to the Add/New Item menu by:
    • Going to Visual Studio menu Tools/Extensions and Updates
    • Choose Online from the left panel.
    • Search for Microsoft Rdlc Report Designer for Visual Studio
    • Download and install it.
  3. Adding Report viewer control by:

    • Going to NuGet Package Manager.

    • Installing Microsoft.ReportingServices.ReportViewerControl.Winforms

    • Go to the folder that contains Microsoft.ReportViewer.WinForms.dll: %USERPROFILE%\.nuget\packages\microsoft.reportingservices.reportviewercontrol.winforms\140.1000.523\lib\net40
    • Drag the Microsoft.ReportViewer.WinForms.dll file and drop it at Visual Studio Toolbox Window.

For WebForms applications:

  1. The same.
  2. The same.
  3. Adding Report viewer control by:

    • Going to NuGet Package Manager.

    • Installing Microsoft.ReportingServices.ReportViewerControl.WebForms

    • Go to the folder that contains Microsoft.ReportViewer.WebForms.dll file: %USERPROFILE%\.nuget\packages\microsoft.reportingservices.reportviewercontrol.webforms\140.1000.523\lib\net40
    • Drag the Microsoft.ReportViewer.WebForms.dll file and drop it at Visual Studio Toolbox Window.

That's all!

Using Server.MapPath() inside a static field in ASP.NET MVC

Try HostingEnvironment.MapPath, which is static.

See this SO question for confirmation that HostingEnvironment.MapPath returns the same value as Server.MapPath: What is the difference between Server.MapPath and HostingEnvironment.MapPath?

NodeJS: How to decode base64 encoded string back to binary?

As of Node.js v6.0.0 using the constructor method has been deprecated and the following method should instead be used to construct a new buffer from a base64 encoded string:

var b64string = /* whatever */;
var buf = Buffer.from(b64string, 'base64'); // Ta-da

For Node.js v5.11.1 and below

Construct a new Buffer and pass 'base64' as the second argument:

var b64string = /* whatever */;
var buf = new Buffer(b64string, 'base64'); // Ta-da

If you want to be clean, you can check whether from exists :

if (typeof Buffer.from === "function") {
    // Node 5.10+
    buf = Buffer.from(b64string, 'base64'); // Ta-da
} else {
    // older Node versions, now deprecated
    buf = new Buffer(b64string, 'base64'); // Ta-da

shell script. how to extract string using regular expressions

Using bash regular expressions:

if [[ $name =~ $re ]]; then echo ${BASH_REMATCH[1]}; fi

Edit - OP asked for explanation of syntax. Regular expression syntax is a large topic which I can't explain in full here, but I will attempt to explain enough to understand the example.


This is the regular expression stored in a bash variable, re - i.e. what you want your input string to match, and hopefully extract a substring. Breaking it down:

  • http:// is just a string - the input string must contain this substring for the regular expression to match
  • [] Normally square brackets are used say "match any character within the brackets". So c[ao]t would match both "cat" and "cot". The ^ character within the [] modifies this to say "match any character except those within the square brackets. So in this case [^/] will match any character apart from "/".
  • The square bracket expression will only match one character. Adding a + to the end of it says "match 1 or more of the preceding sub-expression". So [^/]+ matches 1 or more of the set of all characters, excluding "/".
  • Putting () parentheses around a subexpression says that you want to save whatever matched that subexpression for later processing. If the language you are using supports this, it will provide some mechanism to retrieve these submatches. For bash, it is the BASH_REMATCH array.
  • Finally we do an exact match on "/" to make sure we match all the way to end of the fully qualified domain name and the following "/"

Next, we have to test the input string against the regular expression to see if it matches. We can use a bash conditional to do that:

if [[ $name =~ $re ]]; then
    echo ${BASH_REMATCH[1]}

In bash, the [[ ]] specify an extended conditional test, and may contain the =~ bash regular expression operator. In this case we test whether the input string $name matches the regular expression $re. If it does match, then due to the construction of the regular expression, we are guaranteed that we will have a submatch (from the parentheses ()), and we can access it using the BASH_REMATCH array:

  • Element 0 of this array ${BASH_REMATCH[0]} will be the entire string matched by the regular expression, i.e. "".
  • Subsequent elements of this array will be subsequent results of submatches. Note you can have multiple submatch () within a regular expression - The BASH_REMATCH elements will correspond to these in order. So in this case ${BASH_REMATCH[1]} will contain "", which I think is the string you want.

Note that the contents of the BASH_REMATCH array only apply to the last time the regular expression =~ operator was used. So if you go on to do more regular expression matches, you must save the contents you need from this array each time.

This may seem like a lengthy description, but I have really glossed over several of the intricacies of regular expressions. They can be quite powerful, and I believe with decent performance, but the regular expression syntax is complex. Also regular expression implementations vary, so different languages will support different features and may have subtle differences in syntax. In particular escaping of characters within a regular expression can be a thorny issue, especially when those characters would have an otherwise different meaning in the given language.

Note that instead of setting the $re variable on a separate line and referring to this variable in the condition, you can put the regular expression directly into the condition. However in bash 3.2, the rules were changed regarding whether quotes around such literal regular expressions are required or not. Putting the regular expression in a separate variable is a straightforward way around this, so that the condition works as expected in all bash versions that support the =~ match operator.

Can I call curl_setopt with CURLOPT_HTTPHEADER multiple times to set multiple headers?

 * If $header is an array of headers
 * It will format and return the correct $header
 * $header = [
 *  'Accept' => 'application/json',
 *  'Content-Type' => 'application/x-www-form-urlencoded'
 * ];
$i_header = $header;
if(is_array($i_header) === true){
    $header = [];
    foreach ($i_header as $param => $value) {
        $header[] = "$param: $value";

Builder Pattern in Effective Java

As many already stated here you need to make the class static. Just small addition - if you want, there is a bit different way without static one.

Consider this. Implementing a builder by declaring something like withProperty(value) type setters inside the class and make them return a reference to itself. In this approach, you have a single and an elegant class which is a thread safe and concise.

Consider this:

public class DataObject {

    private String first;
    private String second;
    private String third;

    public String getFirst(){
       return first; 

    public void setFirst(String first){
       this.first = first; 


    public DataObject withFirst(String first){
       this.first = first;
       return this; 

    public DataObject withSecond(String second){
       this.second = second;
       return this; 

    public DataObject withThird(String third){
       this.third = third;
       return this; 

DataObject dataObject = new DataObject()
     .withFirst("first data")
     .withSecond("second data")
     .withThird("third data");

Check it out for more Java Builder examples.

Disable a link in Bootstrap

I just removed 'href' attribute from that anchor tag which I want to disable


$('#idOfAnchorTag').attr('class', $('#idOfAnchorTag').attr('class')+ ' disabled');

Programmatically Lighten or Darken a hex color (or rgb, and blend colors)

I made a port of the excellent xcolor library to remove its jQuery dependency. There are a ton of functions in there including lightening and darkening colors.

Really, converting hex to RGB is a completely separate function from lightening or darkening colors. Keep things DRY please. In any case, once you have an RGB color, you can just add the difference between the light level you want and the light level you have to each of the RGB values:

var lightness = function(level) {
    if(level === undefined) {
        return Math.max(this.g,this.r,this.b)
    } else {
        var roundedLevel = Math.round(level) // fractions won't work here
        var levelChange = roundedLevel - this.lightness()

        var r = Math.max(0,this.r+levelChange)
        var g = Math.max(0,this.g+levelChange)
        var b = Math.max(0,this.b+levelChange)

        if(r > 0xff) r = 0xff
        if(g > 0xff) g = 0xff
        if(b > 0xff) b = 0xff

        return xolor({r: r, g: g, b: b})

var lighter = function(amount) {
    return this.lightness(this.lightness()+amount)

See for more of the source.

In C#, what is the difference between public, private, protected, and having no access modifier?


See here: Access Modifiers.

In a nutshell:

Public gives the method or type complete visibility from other types/classes.

Private allows only the type containing the private method/variable access to the private method/variable (note that nested classes also have access to the containing classes private methods/variables).

Protected is similar to private except derived classes can also access protected methods.

"Nothing" is VB.NET's equivalent to null. Although if you're referring to "nothing" meaning "no access modifier", then it depends, although a very rough rule of thumb (certainly in C#) is that if you don't explicitly specify an access modifier, the method/variable declaration is usually as restricted as it can be. i.e.

public class MyClass
    string s = "";

is effectively the same as:

public class MyClass
    private string s = "";

The linked MSDN article will offer a fully description when there's no access modifier explicitly specified.

Call Python function from JavaScript code

Communicating through processes


Python: This python code block should return random temperatures.


import random, time
while True:
    time.sleep(random.random() * 5)  # wait 0 to 5 seconds
    temperature = (random.random() * 20) - 5  # -5 to 15
    print(temperature, flush=True, end='')

Javascript (Nodejs): Here we will need to spawn a new child process to run our python code and then get the printed output.

// temperature-listener.js

const { spawn } = require('child_process');
const temperatures = []; // Store readings

const sensor = spawn('python', ['']);
sensor.stdout.on('data', function(data) {

    // convert Buffer object to Float

Can't specify the 'async' modifier on the 'Main' method of a console app

As you discovered, in VS11 the compiler will disallow an async Main method. This was allowed (but never recommended) in VS2010 with the Async CTP.

I have recent blog posts about async/await and asynchronous console programs in particular. Here's some background info from the intro post:

If "await" sees that the awaitable has not completed, then it acts asynchronously. It tells the awaitable to run the remainder of the method when it completes, and then returns from the async method. Await will also capture the current context when it passes the remainder of the method to the awaitable.

Later on, when the awaitable completes, it will execute the remainder of the async method (within the captured context).

Here's why this is a problem in Console programs with an async Main:

Remember from our intro post that an async method will return to its caller before it is complete. This works perfectly in UI applications (the method just returns to the UI event loop) and ASP.NET applications (the method returns off the thread but keeps the request alive). It doesn't work out so well for Console programs: Main returns to the OS - so your program exits.

One solution is to provide your own context - a "main loop" for your console program that is async-compatible.

If you have a machine with the Async CTP, you can use GeneralThreadAffineContext from My Documents\Microsoft Visual Studio Async CTP\Samples(C# Testing) Unit Testing\AsyncTestUtilities. Alternatively, you can use AsyncContext from my Nito.AsyncEx NuGet package.

Here's an example using AsyncContext; GeneralThreadAffineContext has almost identical usage:

using Nito.AsyncEx;
class Program
    static void Main(string[] args)
        AsyncContext.Run(() => MainAsync(args));

    static async void MainAsync(string[] args)
        Bootstrapper bs = new Bootstrapper();
        var list = await bs.GetList();

Alternatively, you can just block the main Console thread until your asynchronous work has completed:

class Program
    static void Main(string[] args)

    static async Task MainAsync(string[] args)
        Bootstrapper bs = new Bootstrapper();
        var list = await bs.GetList();

Note the use of GetAwaiter().GetResult(); this avoids the AggregateException wrapping that happens if you use Wait() or Result.

Update, 2017-11-30: As of Visual Studio 2017 Update 3 (15.3), the language now supports an async Main - as long as it returns Task or Task<T>. So you can now do this:

class Program
    static async Task Main(string[] args)
        Bootstrapper bs = new Bootstrapper();
        var list = await bs.GetList();

The semantics appear to be the same as the GetAwaiter().GetResult() style of blocking the main thread. However, there's no language spec for C# 7.1 yet, so this is only an assumption.

login failed for user 'sa'. The user is not associated with a trusted SQL Server connection. (Microsoft SQL Server, Error: 18452) in sql 2008

  1. First make sure sa is enabled
  2. Change the authontication mode to mixed mode (Window and SQL authentication)
  3. Stop your SQL Server
  4. Restart your SQL Server

System.BadImageFormatException: Could not load file or assembly

My cause was different I referenced a web service then I got this message.

Then I changed my target .Net Framework 4.0 to .Net Framework 2.0 and re-refer my webservice. After a few changes problem solved. There is no error worked fine.

hope this helps!

How do I modify a MySQL column to allow NULL?

You want the following:

ALTER TABLE mytable MODIFY mycolumn VARCHAR(255);

Columns are nullable by default. As long as the column is not declared UNIQUE or NOT NULL, there shouldn't be any problems.

How to suppress binary file matching results in grep

This is an old question and its been answered but I thought I'd put the --binary-files=text option here for anyone who wants to use it. The -I option ignores the binary file but if you want the grep to treat the binary file as a text file use --binary-files=text like so:

bash$ grep -i reset mediaLog*
Binary file mediaLog_dc1.txt matches
bash$ grep --binary-files=text -i reset mediaLog*
mediaLog_dc1.txt:2016-06-29 15:46:02,470 - Media [uploadChunk  ,315] - ERROR - ('Connection aborted.', error(104, 'Connection reset by peer'))
mediaLog_dc1.txt:ConnectionError: ('Connection aborted.', error(104, 'Connection reset by peer'))

What is the difference between jQuery: text() and html() ?

The first example will actually embed HTML within the div whereas the second example will escape the text by means of replacing element-related characters with their corresponding character entities so that it displays literally (i.e. the HTML will be displayed not rendered).

git pull aborted with error filename too long

Solution1 - set global config, by running this command:

git config --system core.longpaths true

Solution2 - or you can edit directly your specific git config file like below:

YourRepoFolder -> .git -> config:

    repositoryformatversion = 0
    filemode = false
    longpaths = true        <-- (add this line under core section)

Solution3 - when cloning a new repository: here.

Login to website, via C#

You can continue using WebClient to POST (instead of GET, which is the HTTP verb you're currently using with DownloadString), but I think you'll find it easier to work with the (slightly) lower-level classes WebRequest and WebResponse.

There are two parts to this - the first is to post the login form, the second is recovering the "Set-cookie" header and sending that back to the server as "Cookie" along with your GET request. The server will use this cookie to identify you from now on (assuming it's using cookie-based authentication which I'm fairly confident it is as that page returns a Set-cookie header which includes "PHPSESSID").

POSTing to the login form

Form posts are easy to simulate, it's just a case of formatting your post data as follows:


Using WebRequest and code I adapted from Scott Hanselman, here's how you'd POST form data to your login form:

string formUrl = ""; // NOTE: This is the URL the form POSTs to, not the URL of the form (you can find this in the "action" attribute of the HTML's form tag
string formParams = string.Format("email_address={0}&password={1}", "your email", "your password");
string cookieHeader;
WebRequest req = WebRequest.Create(formUrl);
req.ContentType = "application/x-www-form-urlencoded";
req.Method = "POST";
byte[] bytes = Encoding.ASCII.GetBytes(formParams);
req.ContentLength = bytes.Length;
using (Stream os = req.GetRequestStream())
    os.Write(bytes, 0, bytes.Length);
WebResponse resp = req.GetResponse();
cookieHeader = resp.Headers["Set-cookie"];

Here's an example of what you should see in the Set-cookie header for your login form:

PHPSESSID=c4812cffcf2c45e0357a5a93c137642e; path=/;,wowmine_referer=directenter; path=/;,lang=en; path=/;,adt_usertype=other,adt_host=-

GETting the page behind the login form

Now you can perform your GET request to a page that you need to be logged in for.

string pageSource;
string getUrl = "the url of the page behind the login";
WebRequest getRequest = WebRequest.Create(getUrl);
getRequest.Headers.Add("Cookie", cookieHeader);
WebResponse getResponse = getRequest.GetResponse();
using (StreamReader sr = new StreamReader(getResponse.GetResponseStream()))
    pageSource = sr.ReadToEnd();


If you need to view the results of the first POST, you can recover the HTML it returned with:

using (StreamReader sr = new StreamReader(resp.GetResponseStream()))
    pageSource = sr.ReadToEnd();

Place this directly below cookieHeader = resp.Headers["Set-cookie"]; and then inspect the string held in pageSource.

How can I add a variable to console.log?

You can pass multiple args to log:

console.log("story", name, "story");

How to extract elements from a list using indices in Python?

I think you're looking for this:

elements = [10, 11, 12, 13, 14, 15]
indices = (1,1,2,1,5)

result_list = [elements[i] for i in indices]    

How do you write to a folder on an SD card in Android?

File sdCard = Environment.getExternalStorageDirectory();
File dir = new File (sdCard.getAbsolutePath() + "/dir1/dir2");
File file = new File(dir, "filename");

FileOutputStream f = new FileOutputStream(file);

Dump a list in a pickle file and retrieve it back later

Pickling will serialize your list (convert it, and it's entries to a unique byte string), so you can save it to disk. You can also use pickle to retrieve your original list, loading from the saved file.

So, first build a list, then use pickle.dump to send it to a file...

Python 3.4.1 (default, May 21 2014, 12:39:51) 
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> mylist = ['I wish to complain about this parrot what I purchased not half an hour ago from this very boutique.', "Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?", "I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!", "No, no, 'e's uh,...he's resting."]
>>> import pickle
>>> with open('parrot.pkl', 'wb') as f:
...   pickle.dump(mylist, f)

Then quit and come back later… and open with pickle.load...

Python 3.4.1 (default, May 21 2014, 12:39:51) 
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle
>>> with open('parrot.pkl', 'rb') as f:
...   mynewlist = pickle.load(f)
>>> mynewlist
['I wish to complain about this parrot what I purchased not half an hour ago from this very boutique.', "Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?", "I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!", "No, no, 'e's uh,...he's resting."]

Sort an Array by keys based on another Array?

I adopted the answer from @Darkwaltz4 for its brevity and would like to share how I adapted the solution to situations where the array may contain different keys for each iteration like so:

Array[0] ...
['dob'] = '12/08/1986';
['some_key'] = 'some value';

Array[1] ...
['dob'] = '12/08/1986';

Array[2] ...
['dob'] = '12/08/1986';
['some_key'] = 'some other value';

and maintained a "master key" like so:

$master_key = array( 'dob' => ' ' ,  'some_key' => ' ' );

array_merge would have executed the merge in the Array[1] iteration based on $master_key and produced ['some_key'] = '', an empty value, for that iteration. Hence, array_intersect_key was used to modify $master_key in each iterations like so:

foreach ($customer as $customer) {
  $modified_key = array_intersect_key($master_key, $unordered_array);
  $properOrderedArray = array_merge($modified_key, $customer);

Reactjs convert html string to jsx

npm i html-react-parser;

import Parser from 'html-react-parser';


How to set up fixed width for <td>?

Hard to judge without the context of the page html or the rest of your CSS. There might be a zillion reasons why your CSS rule is not affecting the td element.

Have you tried more specific CSS selectors such as

tr.somethingontrlevel td.something {
  width: 90px;

This to avoid your CSS being overridden by a more specific rule from the bootstrap css.

(by the way, in your inline css sample with the style attribute, you misspelled width - that could explain why that try failed!)

Java 8 - Difference between Optional.flatMap and

Note:- below is the illustration of map and flatmap function, otherwise Optional is primarily designed to be used as a return type only.

As you already may know Optional is a kind of container which may or may not contain a single object, so it can be used wherever you anticipate a null value(You may never see NPE if use Optional properly). For example if you have a method which expects a person object which may be nullable you may want to write the method something like this:

void doSome(Optional<Person> person){
  /*and here you want to retrieve some property phone out of person
    you may write something like this:
  Optional<String> phone =>p.getPhone());
class Person{
  private String phone;
  //setter, getters

Here you have returned a String type which is automatically wrapped in an Optional type.

If person class looked like this, i.e. phone is also Optional

class Person{
  private Optional<String> phone;

In this case invoking map function will wrap the returned value in Optional and yield something like:

//And you may want Optional<String> instead, here comes flatMap

void doSome(Optional<Person> person){
  Optional<String> phone = person.flatMap((p)->p.getPhone());

PS; Never call get method (if you need to) on an Optional without checking it with isPresent() unless you can't live without NullPointerExceptions.

How can I get a favicon to show up in my django app?

The best solution is to override the Django base.html template. Make another base.html template under admin directory. Make an admin directory first if it does not exist. app/admin/base.html.

Add {% block extrahead %} to the overriding template.

{% extends 'admin/base.html' %}
{% load staticfiles %}
{% block javascripts %}
    {{ block.super }}
<script type="text/javascript" src="{% static 'app/js/action.js' %}"></script>

{% endblock %}

{% block extrahead %}
    <link rel="shortcut icon" href="{% static 'app/img/favicon.ico'  %}" />
{% endblock %}
{% block stylesheets %}

    {{ block.super }}
{% endblock %}

How to split CSV files as per number of rows specified?

This should work !!!

file_name = Name of the file you want to split.
10000 = Number of rows each split file would contain
file_part_ = Prefix of split file name (file_part_0,file_part_1,file_part_2..etc goes on)

split -d -l 10000 file_name.csv file_part_

What does the "yield" keyword do?

Yield is an object

A return in a function will return a single value.

If you want a function to return a huge set of values, use yield.

More importantly, yield is a barrier.

like barrier in the CUDA language, it will not transfer control until it gets completed.

That is, it will run the code in your function from the beginning until it hits yield. Then, it’ll return the first value of the loop.

Then, every other call will run the loop you have written in the function one more time, returning the next value until there isn't any value to return.

Styling HTML email for Gmail

As others have said, some email programs will not read the css styles. If you already have a web email written up you can use the following tool from zurb to inline all of your styles:

This comes in extremely handy when using templates like those mentioned above from mailchimp, campaign monitor, etc. as they, as you have found, will not work in some email programs. This tool leaves your style section for the mail programs that will read it and puts all the styles inline to get more universal readability in the format that you wanted.

Python: count repeated elements in the list

Use Counter

>>> from collections import Counter
>>> MyList = ["a", "b", "a", "c", "c", "a", "c"]
>>> c = Counter(MyList)
>>> c
Counter({'a': 3, 'c': 3, 'b': 1})

AngularJs: Reload page

This can be done by calling the reload() method in JavaScript.


How to parse dates in multiple formats using SimpleDateFormat

This solution checks all the possible formats before throwing an exception. This solution is more convenient if you are trying to test for multiple date formats.

Date extractTimestampInput(String strDate){
    final List<String> dateFormats = Arrays.asList("yyyy-MM-dd HH:mm:ss.SSS", "yyyy-MM-dd");    

    for(String format: dateFormats){
        SimpleDateFormat sdf = new SimpleDateFormat(format);
            return sdf.parse(strDate);
        } catch (ParseException e) {
             //intentionally empty
        throw new IllegalArgumentException("Invalid input for date. Given '"+strDate+"', expecting format yyyy-MM-dd HH:mm:ss.SSS or yyyy-MM-dd.");


How to pipe list of files returned by find command to cat to view all the files

  1. Piping to another process (Although this WON'T accomplish what you said you are trying to do):

    command1 | command2

    This will send the output of command1 as the input of command2

  2. -exec on a find (this will do what you are wanting to do -- but is specific to find)

    find . -name '*.foo' -exec cat {} \;

    (Everything between find and -exec are the find predicates you were already using. {} will substitute the particular file you found into the command (cat {} in this case); the \; is to end the -exec command.)

  3. send output of one process as command line arguments to another process

    command2 `command1`

    for example:

    cat `find . -name '*.foo' -print`

    (Note these are BACK-QUOTES not regular quotes (under the tilde ~ on my keyboard).) This will send the output of command1 into command2 as command line arguments. Note that file names containing spaces (newlines, etc) will be broken into separate arguments, though.

How do I send an HTML Form in an Email .. not just MAILTO

<FORM Action="mailto:xyz?Subject=Test_Post" METHOD="POST">
    mailto: protocol test:
    <INPUT name="Subject" value="Test Subject">
    <TEXTAREA name="Body">
    <INPUT type="submit" value="Submit"> 

What is this Javascript "require"?

Alright, so let's first start with making the distinction between Javascript in a web browser, and Javascript on a server (CommonJS and Node).

Javascript is a language traditionally confined to a web browser with a limited global context defined mostly by what came to be known as the Document Object Model (DOM) level 0 (the Netscape Navigator Javascript API).

Server-side Javascript eliminates that restriction and allows Javascript to call into various pieces of native code (like the Postgres library) and open sockets.

Now require() is a special function call defined as part of the CommonJS spec. In node, it resolves libraries and modules in the Node search path, now usually defined as node_modules in the same directory (or the directory of the invoked javascript file) or the system-wide search path.

To try to answer the rest of your question, we need to use a proxy between the code running in the the browser and the database server.

Since we are discussing Node and you are already familiar with how to run a query from there, it would make sense to use Node as that proxy.

As a simple example, we're going to make a URL that returns a few facts about a Beatle, given a name, as JSON.

/* your connection code */

var express = require('express');
var app = express.createServer();
app.get('/beatles/:name', function(req, res) {
    var name = || '';
    name = name.replace(/[^a-zA_Z]/, '');
    if (!name.length) {
    } else {
        var query = client.query('SELECT * FROM BEATLES WHERE name =\''+name+'\' LIMIT 1');
        var data = {};
        query.on('row', function(row) {
            data = row;
app.listen(80, '');

Accessing certain pixel RGB value in openCV

const double pi = boost::math::constants::pi<double>();

cv::Mat distance2ellipse(cv::Mat image, cv::RotatedRect ellipse){
    float distance = 2.0f;
    float angle = ellipse.angle;
    cv::Point ellipse_center =;
    float major_axis = ellipse.size.width/2;
    float minor_axis = ellipse.size.height/2;
    cv::Point pixel;
    float a,b,c,d;

    for(int x = 0; x < image.cols; x++)
        for(int y = 0; y < image.rows; y++) 
        auto u =  cos(angle*pi/180)*(x-ellipse_center.x) + sin(angle*pi/180)*(y-ellipse_center.y);
        auto v = -sin(angle*pi/180)*(x-ellipse_center.x) + cos(angle*pi/180)*(y-ellipse_center.y);

        distance = (u/major_axis)*(u/major_axis) + (v/minor_axis)*(v/minor_axis);  

  <cv::Vec3b>(y,x)[1] = 255;
  return image;  

Can't ignore UserInterfaceState.xcuserstate

For me nothing worked, but this

add this line to your gitignore


Git removing upstream from local repository

Using git version there is no "remove" command for remote. Use "rm" instead.

$ git remote rm upstream
$ git remote add upstream

or, as noted in the previous answer, set-url works.

I don't know when the command changed, but Ubuntu 12.04 shipped with

How to convert a Java 8 Stream to an Array?

If you want to get an array of ints, with values from 1 to 10, from a Stream<Integer>, there is IntStream at your disposal.

Here we create a Stream with a Stream.of method and convert a Stream<Integer> to an IntStream using a mapToInt. Then we can call IntStream's toArray method.

Stream<Integer> stream = Stream.of(1,2,3,4,5,6,7,8,9,10);
//or use this to create our stream 
//Stream<Integer> stream = IntStream.rangeClosed(1, 10).boxed();
int[] array =  stream.mapToInt(x -> x).toArray();

Here is the same thing, without the Stream<Integer>, using only the IntStream:

int[]array2 =  IntStream.rangeClosed(1, 10).toArray();

How to change already compiled .class file without decompile?

As far as I've been able to find out, there is no simple way to do it. The easiest way is to not actually convert the class file into an executable, but to wrap an executable launcher around the class file. That is, create an executable file (perhaps an OS-based, executable scripting file) which simply invokes the Java class through the command line.

If you want to actually have a program that does it, you should look into some of the automated installers out there.

Here is a way I've found:

import java.util.jar.*;

class OnlyExt implements FilenameFilter{
String ext;
public OnlyExt(String ext){
this.ext="." + ext;

public boolean accept(File dir,String name){
return name.endsWith(ext);

public class ExeCreator {
public static int buffer = 10240;
protected void create(File exefile, File[] listFiles) {
try {
byte b[] = new byte[buffer];
FileOutputStream fout = new FileOutputStream(exefile);
JarOutputStream out = new JarOutputStream(fout, new Manifest());
for (int i = 0; i < listFiles.length; i++) {
if (listFiles[i] == null || !listFiles[i].exists()|| listFiles[i].isDirectory())
System.out.println("Adding " + listFiles[i].getName());
JarEntry addFiles = new JarEntry(listFiles[i].getName());

FileInputStream fin = new FileInputStream(listFiles[i]);
while (true) {
int len =, 0, b.length);
if (len <= 0)
out.write(b, 0, len);
System.out.println("Jar File is created successfully.");
} catch (Exception ex) {}

public static void main(String[]args){
ExeCreator exe=new ExeCreator();
FilenameFilter ff = new OnlyExt("class");
File folder = new File("./examples");
File[] files = folder.listFiles(ff);
File file=new File("examples.exe");
exe.create(file, files);



Working copy locked error in tortoise svn while committing

No problem... try this:

  • Go to top level SVN folder.
  • Right click on folder (that has your svn files) > TortoiseSVN > CleanUp

This will surely solve your problem. I did this lots of time... :)

Note. Make sure "Break locks" option is selected in the Cleanup dialog.

Change the name of a key in dictionary

Easily done in 2 steps:

dictionary[new_key] = dictionary[old_key]
del dictionary[old_key]

Or in 1 step:

dictionary[new_key] = dictionary.pop(old_key)

which will raise KeyError if dictionary[old_key] is undefined. Note that this will delete dictionary[old_key].

>>> dictionary = { 1: 'one', 2:'two', 3:'three' }
>>> dictionary['ONE'] = dictionary.pop(1)
>>> dictionary
{2: 'two', 3: 'three', 'ONE': 'one'}
>>> dictionary['ONE'] = dictionary.pop(1)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
KeyError: 1

c++ integer->std::string conversion. Simple function?

Now in c++11 we have

#include <string>
string s = std::to_string(123);

Link to reference:

Using the value in a cell as a cell reference in a formula?


=SUM(INDIRECT(<start cell here> & ":" & <end cell here>))

jQuery select2 get value of select tag?

Try this :

$('#input_id :selected').val(); //for getting value from selected option
$('#input_id :selected').text(); //for getting text from selected option

How to subtract days from a plain Date?

I converted into millisecond and deducted days else month and year won't change and logical

var numberOfDays = 10;//number of days need to deducted or added
var date = "01-01-2018"// date need to change
var dt = new Date(parseInt(date.substring(6), 10),        // Year
              parseInt(date.substring(3,5), 10) - 1, // Month (0-11)
              parseInt(date.substring(0,2), 10));
var new_dt = dt.setMilliseconds(dt.getMilliseconds() - numberOfDays*24*60*60*1000);
new_dt = new Date(new_dt);
var changed_date = new_dt.getDate()+"-"+(new_dt.getMonth()+1)+"-"+new_dt.getFullYear();

Hope helps

Assertion failure in dequeueReusableCellWithIdentifier:forIndexPath:

You're using the dequeueReusableCellWithIdentifier:forIndexPath: method. The documentation for that method says this:

Important: You must register a class or nib file using the registerNib:forCellReuseIdentifier: or registerClass:forCellReuseIdentifier: method before calling this method.

You didn't register a nib or a class for the reuse identifier "Cell".

Looking at your code, you seem to expect the dequeue method to return nil if it doesn't have a cell to give you. You need to use the dequeueReusableCellWithIdentifier: for that behavior:

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

Notice that dequeueReusableCellWithIdentifier: and dequeueReusableCellWithIdentifier:forIndexPath: are different methods. See doc for the former and the latter.

If you want to understand why you'd want to ever use dequeueReusableCellWithIdentifier:forIndexPath:, check out this Q&A.

How can I list all of the files in a directory with Perl?

If you are a slacker like me you might like to use the File::Slurp module. The read_dir function will reads directory contents into an array, removes the dots, and if needed prefix the files returned with the dir for absolute paths

my @paths = read_dir( '/path/to/dir', prefix => 1 ) ;

Connecting to Microsoft SQL server using Python

Minor addition to what has been said before. You likely want to return a dataframe. This would be done as

import pypyodbc 
import pandas as pd

cnxn = pypyodbc.connect("Driver={SQL Server Native Client 11.0};"
df = pd.read_sql_query('select * from table', cnxn)

sqlplus: error while loading shared libraries: cannot open shared object file: No such file or directory

PERMISSIONS: I want to stress the importance of permissions for "sqlplus".

  1. For any "Other" UNIX user other than the Owner/Group to be able to run sqlplus and access an ORACLE database , read/execute permissions are required (rx) for these 4 directories :

    $ORACLE_HOME/bin , $ORACLE_HOME/lib, $ORACLE_HOME/oracore, $ORACLE_HOME/sqlplus

  2. Environment. Set those properly:

    A. ORACLE_HOME (example: ORACLE_HOME=/u01/app/oranpgm/product/12.1.0/PRMNRDEV/)

    B. LD_LIBRARY_PATH (example: ORACLE_HOME=/u01/app/oranpgm/product/12.1.0/PRMNRDEV/lib)


    D. PATH

     export PATH="$ORACLE_HOME/bin:$PATH"

How to delete a record in Django models?

if you want to delete one instance then write the code

entry= Account.objects.get(id= 5)

if you want to delete all instance then write the code

entries= Account.objects.all()

datatable jquery - table header width not aligned with body width

I fixed, Work for me.

var table = $('#example').DataTable();
$('#container').css( 'display', 'block' );


var table = $('#example').DataTable();


Adjust width and height of iframe to fit with content in it

Javascript to be placed in header:

function resizeIframe(obj) { = obj.contentWindow.document.body.scrollHeight + 'px';

Here goes iframe html code:

<iframe class="spec_iframe" seamless="seamless" frameborder="0" scrolling="no" id="iframe" onload="javascript:resizeIframe(this);" src="somepage.php" style="height: 1726px;"></iframe>

Css stylesheet


.spec_iframe {
        width: 100%;
        overflow: hidden;

How do I include image files in Django templates?

I do understand, that your question was about files stored in MEDIA_ROOT, but sometimes it can be possible to store content in static, when you are not planning to create content of that type anymore.
May be this is a rare case, but anyway - if you have a huge amount of "pictures of the day" for your site - and all these files are on your hard drive?

In that case I see no contra to store such a content in STATIC.
And all becomes really simple:


To link to static files that are saved in STATIC_ROOT Django ships with a static template tag. You can use this regardless if you're using RequestContext or not.

{% load static %} <img src="{% static "images/hi.jpg" %}" alt="Hi!" />

copied from Official django 1.4 documentation / Built-in template tags and filters

How to POST URL in data of a curl request

I don't think it's necessary to use semi-quotes around the variables, try:

curl -XPOST 'http://localhost/Service' -d "path=%2fxyz%2fpqr%2ftest%2f&fileName=1.doc"

%2f is the escape code for a /.

Also, do you need to specify a port? ( just checking :) )

How to specify the JDK version in android studio?

This is old question but still my answer may help someone

For checking Java version in android studio version , simply open Terminal of Android Studio and type

java -version 

This will display java version installed in android studio

Fastest way to zero out a 2d array in C?

Well, the fastest way to do it is to not do it at all.

Sounds odd I know, here's some pseudocode:

int array [][];
bool array_is_empty;

void ClearArray ()
   array_is_empty = true;

int ReadValue (int x, int y)
   return array_is_empty ? 0 : array [x][y];

void SetValue (int x, int y, int value)
   if (array_is_empty)
      memset (array, 0, number of byte the array uses);
      array_is_empty = false;
   array [x][y] = value;

Actually, it's still clearing the array, but only when something is being written to the array. This isn't a big advantage here. However, if the 2D array was implemented using, say, a quad tree (not a dynamic one mind), or a collection of rows of data, then you can localise the effect of the boolean flag, but you'd need more flags. In the quad tree just set the empty flag for the root node, in the array of rows just set the flag for each row.

Which leads to the question "why do you want to repeatedly zero a large 2d array"? What is the array used for? Is there a way to change the code so that the array doesn't need zeroing?

For example, if you had:

clear array
for each set of data
  for each element in data set
    array += element 

that is, use it for an accumulation buffer, then changing it like this would improve the performance no end:

 for set 0 and set 1
   for each element in each set
     array = element1 + element2

 for remaining data sets
   for each element in data set
     array += element 

This doesn't require the array to be cleared but still works. And that will be far faster than clearing the array. Like I said, the fastest way is to not do it in the first place.

Spring Bean Scopes

Detailed explanation for each scope can be found here in Spring bean scopes. Below is the summary

Singleton - (Default) Scopes a single bean definition to a single object instance per Spring IoC container.

prototype - Scopes a single bean definition to any number of object instances.

request - Scopes a single bean definition to the lifecycle of a single HTTP request; that is, each HTTP request has its own instance of a bean created off the back of a single bean definition. Only valid in the context of a web-aware Spring ApplicationContext.

session - Scopes a single bean definition to the lifecycle of an HTTP Session. Only valid in the context of a web-aware Spring ApplicationContext.

global session - Scopes a single bean definition to the lifecycle of a global HTTP Session. Typically only valid when used in a portlet context. Only valid in the context of a web-aware Spring ApplicationContext.

Redirect to external URI from ASP.NET MVC controller

Try this (I've used Home controller and Index View):

return RedirectToAction("Index", "Home");

Compiling LaTex bib source

Just in case it helps someone, since these questions (and answers) helped me really much; I decided to create an alias that runs these 4 commands in a row:

Just add the following line to your ~/.bashrc file (modify the main keyword accordingly to the name of your .tex and .bib files)

alias texbib = 'pdflatex main.tex && bibtex main && pdflatex main.tex && pdflatex main.tex'

And now, by just executing the texbib command (alias), all these commands will be executed sequentially.

Node.js Web Application examples/tutorials


Dav Glass from Yahoo has given a talk at YuiConf2010 in November which is now available in Video from.

He shows to great extend how one can use YUI3 to render out widgets on the server side an make them work with GET requests when JS is disabled, or just make them work normally when it's active.

He also shows examples of how to use server side DOM to apply style sheets before rendering and other cool stuff.

The demos can be found on his GitHub Account.

The part that's missing IMO to make this really awesome, is some kind of underlying storage of the widget state. So that one can visit the page without JavaScript and everything works as expected, then they turn JS on and now the widget have the same state as before but work without page reloading, then throw in some saving to the server + WebSockets to sync between multiple open browser.... and the next generation of unobtrusive and gracefully degrading ARIA's is born.

Original Answer

Well go ahead and built it yourself then.

Seriously, 90% of all WebApps out there work fine with a REST approach, of course you could do magical things like superior user tracking, tracking of downloads in real time, checking which parts of videos are being watched etc.

One problem is scalability, as soon as you have more then 1 Node process, many (but not all) of the benefits of having the data stored between requests go away, so you have to make sure that clients always hit the same process. And even then, bigger things will yet again need a database layer.

Node.js isn't the solution to everything, I'm sure people will build really great stuff in the future, but that needs some time, right now many are just porting stuff over to Node to get things going.

What (IMHO) makes Node.js so great, is the fact that it streamlines the Development process, you have to write less code, it works perfectly with JSON, you loose all that context switching.

I mainly did gaming experiments so far, but I can for sure say that there will be many cool multi player (or even MMO) things in the future, that use both HTML5 and Node.js.

Node.js is still gaining traction, it's not even near to the RoR Hype some years ago (just take a look at the Node.js tag here on SO, hardly 4-5 questions a day).

Rome (or RoR) wasn't built over night, and neither will Node.js be.

Node.js has all the potential it needs, but people are still trying things out, so I'd suggest you to join them :)

Android: Align button to bottom-right of screen using FrameLayout?

Actually it's possible, despite what's being said in other answers. If you have a FrameLayout, and want to position a child item to the bottom, you can use android:layout_gravity="bottom" and that is going to align that child to the bottom of the FrameLayout.

I know it works because I'm using it. I know is late, but it might come handy to others since this ranks in the top positions on google

Calling remove in foreach loop in Java

Make sure this is not code smell. Is it possible to reverse the logic and be 'inclusive' rather than 'exclusive'?

List<String> names = ....
List<String> reducedNames = ....
for (String name : names) {
   // Do something
   if (conditionToIncludeMet)
return reducedNames;

The situation that led me to this page involved old code that looped through a List using indecies to remove elements from the List. I wanted to refactor it to use the foreach style.

It looped through an entire list of elements to verify which ones the user had permission to access, and removed the ones that didn't have permission from the list.

List<Service> services = ...
for (int i=0; i<services.size(); i++) {
    if (!isServicePermitted(user, services.get(i)))

To reverse this and not use the remove:

List<Service> services = ...
List<Service> permittedServices = ...
for (Service service:services) {
    if (isServicePermitted(user, service))
return permittedServices;

When would "remove" be preferred? One consideration is if gien a large list or expensive "add", combined with only a few removed compared to the list size. It might be more efficient to only do a few removes rather than a great many adds. But in my case the situation did not merit such an optimization.

Find Process Name by its Process ID

SET /a pid=1600
FOR /f "skip=3delims=" %%a IN ('tasklist') DO (
 SET "found=%%a"
 SET /a foundpid=!found:~26,8!
 IF %pid%==!foundpid! echo found %pid%=!found:~0,24%!


...set PID to suit your circumstance.

Run reg command in cmd (bat file)?

You could also just create a Group Policy Preference and have it create the reg key for you. (no scripting involved)

Python style - line continuation with strings?

Another possibility is to use the textwrap module. This also avoids the problem of "string just sitting in the middle of nowhere" as mentioned in the question.

import textwrap
mystr = """\
        Why, hello there
        wonderful stackoverfow people"""
print (textwrap.fill(textwrap.dedent(mystr)))

How do I drop a foreign key constraint only if it exists in sql server?

The more simple solution is provided in Eric Isaacs's answer. However, it will find constraints on any table. If you want to target a foreign key constraint on a specific table, use this:

  FROM sys.foreign_keys 
   WHERE object_id = OBJECT_ID(N'dbo.FK_TableName_TableName2')
   AND parent_object_id = OBJECT_ID(N'dbo.TableName')
  ALTER TABLE [dbo.TableName] DROP CONSTRAINT [FK_TableName_TableName2]

document.getElementByID is not a function

I've modified your script to work with jQuery, if you wish to do so.

    //To add a task when the user hits the return key
          if(evt.keyCode == 13)
             add_task($(this), evt);
    //To add a task when the user clicks on the submit button

function add_task(textBox, evt){
  var taskText = textBox.val();
  $("<li />").text(taskText).appendTo("#tasks");

java.lang.UnsupportedClassVersionError: Bad version number in .class file?

I also got the same error. Reason for that I was compiling the project using Maven. I had JAVA_HOME pointing to JDK7 and hence java 1.7 was being used for compilation and when running the project I was using JDK1.5. Changing the below entry in .classpath file or change in the eclipse as in the screenshot resolved the issue.

classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/J2SE-1.5

or change in the run configuarions of eclipse as enter image description here

Php - Your PHP installation appears to be missing the MySQL extension which is required by WordPress

For me (ubuntu 16.04) the winner was:

sudo apt install php7.0-mysql

Vuex - Computed property "name" was assigned to but it has no setter

If you're going to v-model a computed, it needs a setter. Whatever you want it to do with the updated value (probably write it to the $store, considering that's what your getter pulls it from) you do in the setter.

If writing it back to the store happens via form submission, you don't want to v-model, you just want to set :value.

If you want to have an intermediate state, where it's saved somewhere but doesn't overwrite the source in the $store until form submission, you'll need to create such a data item.

NotificationCenter issue on Swift 3

Notifications appear to have changed again (October 2016).

// Register to receive notification

NotificationCenter.default.addObserver(self, selector: #selector(yourClass.yourMethod), name: NSNotification.Name(rawValue: "yourNotificatioName"), object: nil)

// Post notification NSNotification.Name(rawValue: "yourNotificationName"), object: nil)

Select top 1 result using JPA

Use a native SQL query by specifying a @NamedNativeQuery annotation on the entity class, or by using the EntityManager.createNativeQuery method. You will need to specify the type of the ResultSet using an appropriate class, or use a ResultSet mapping.

How can I output a UTF-8 CSV in PHP that Excel will read properly?

Excel doesn't support UTF-8. You have to encode your UTF-8 text into UCS-2LE.

mb_convert_encoding($output, 'UCS-2LE', 'UTF-8');

How to schedule a function to run every hour on Flask?

You could try using APScheduler's BackgroundScheduler to integrate interval job into your Flask app. Below is the example that uses blueprint and app factory ( :

from datetime import datetime

# import BackgroundScheduler
from apscheduler.schedulers.background import BackgroundScheduler
from flask import Flask

from webapp.models.main import db 
from webapp.controllers.main import main_blueprint    

# define the job
def hello_job():
    print('Hello Job! The time is: %s' %

def create_app(object_name):
    app = Flask(__name__)
    # init BackgroundScheduler job
    scheduler = BackgroundScheduler()
    # in your case you could change seconds to hours
    scheduler.add_job(hello_job, trigger='interval', seconds=3)

        # To keep the main thread alive
        return app
        # shutdown if app occurs except 

Hope it helps :)

Ref :


How to convert hex string to Java string?

Using Hex in Apache Commons:

String hexString = "fd00000aa8660b5b010006acdc0100000101000100010000";    
byte[] bytes = Hex.decodeHex(hexString.toCharArray());
System.out.println(new String(bytes, "UTF-8"));

Warning: mysqli_real_escape_string() expects exactly 2 parameters, 1 given... what I do wrong?

There is slight change in mysql_real_escape_string mysqli_real_escape_string. below syntax

mysql_real_escape_string syntax will be mysql_real_escape_string($_POST['sample_var'])

mysqli_real_escape_string syntax will be mysqli_real_escape_string($conn,$_POST['sample_var'])

How to use GROUP BY to concatenate strings in SQL Server?

SQL Server 2005 and later allow you to create your own custom aggregate functions, including for things like concatenation- see the sample at the bottom of the linked article.

Get Wordpress Category from Single Post

<div class="post_category">
        <?php $category = get_the_category();
             $allcategory = get_the_category(); 
        foreach ($allcategory as $category) {
           <a class="btn"><?php echo $category->cat_name;; ?></a>

Securely storing passwords for use in python script

Know the master key yourself. Don't hard code it.

Use py-bcrypt (bcrypt), powerful hashing technique to generate a password yourself.

Basically you can do this (an idea...)

import bcrypt
from getpass import getpass
master_secret_key = getpass('tell me the master secret key you are going to use')
salt = bcrypt.gensalt()
combo_password = raw_password + salt + master_secret_key
hashed_password = bcrypt.hashpw(combo_password, salt)

save salt and hashed password somewhere so whenever you need to use the password, you are reading the encrypted password, and test against the raw password you are entering again.

This is basically how login should work these days.

Equivalent of Super Keyword in C#

C# equivalent of your code is

  class Imagedata : PDFStreamEngine
     // C# uses "base" keyword whenever Java uses "super" 
     // so instead of super(...) in Java we should call its C# equivalent (base):
     public Imagedata()
       : base(ResourceLoader.loadProperties("org/apache/pdfbox/resources/", true)) 
     { }

     // Java methods are virtual by default, when C# methods aren't.
     // So we should be sure that processOperator method in base class 
     // (that is PDFStreamEngine)
     // declared as "virtual"
     protected override void processOperator(PDFOperator operations, List arguments)
        base.processOperator(operations, arguments);

Using strtok with a std::string

EDIT: usage of const cast is only used to demonstrate the effect of strtok() when applied to a pointer returned by string::c_str().

You should not use strtok() since it modifies the tokenized string which may lead to undesired, if not undefined, behaviour as the C string "belongs" to the string instance.

#include <string>
#include <iostream>

int main(int ac, char **av)
    std::string theString("hello world");
    std::cout << theString << " - " << theString.size() << std::endl;

    //--- this cast *only* to illustrate the effect of strtok() on std::string 
    char *token = strtok(const_cast<char  *>(theString.c_str()), " ");

    std::cout << theString << " - " << theString.size() << std::endl;

    return 0;

After the call to strtok(), the space was "removed" from the string, or turned down to a non-printable character, but the length remains unchanged.

hello world - 11
helloworld - 11

Therefore you have to resort to native mechanism, duplication of the string or an third party library as previously mentioned.

Math.random() versus Random.nextInt(int)

According to this example Random.nextInt(n) has less predictable output then Math.random() * n. According to [sorted array faster than an unsorted array][1] I think we can say Random.nextInt(n) is hard to predict.

usingRandomClass : time:328 milesecond.

usingMathsRandom : time:187 milesecond.

package javaFuction;
import java.util.Random;
public class RandomFuction 
    static int array[] = new int[9999];
    static long sum = 0;
    public static void usingMathsRandom() {
        for (int i = 0; i < 9999; i++) {
         array[i] = (int) (Math.random() * 256);

        for (int i = 0; i < 9999; i++) {
            for (int j = 0; j < 9999; j++) {
                if (array[j] >= 128) {
                    sum += array[j];

    public static void usingRandomClass() {
        Random random = new Random();
        for (int i = 0; i < 9999; i++) {
            array[i] = random.nextInt(256);

        for (int i = 0; i < 9999; i++) {
            for (int j = 0; j < 9999; j++) {
                if (array[j] >= 128) {
                    sum += array[j];



    public static void main(String[] args) {
        long start = System.currentTimeMillis();
        long end = System.currentTimeMillis();
        System.out.println("usingRandomClass " + (end - start));
        start = System.currentTimeMillis();
        end = System.currentTimeMillis();
        System.out.println("usingMathsRandom " + (end - start));



Provide static IP to docker containers via docker-compose

Note that I don't recommend a fixed IP for containers in Docker unless you're doing something that allows routing from outside to the inside of your container network (e.g. macvlan). DNS is already there for service discovery inside of the container network and supports container scaling. And outside the container network, you should use exposed ports on the host. With that disclaimer, here's the compose file you want:

version: '2'

    container_name: mysql
    image: mysql:latest
    restart: always
     - "3306:3306"

    container_name: apigw-tomcat
    build: tomcat/.
     - "8080:8080"
     - "8009:8009"
     - mysql

    driver: bridge
       - subnet:

Sublime Text 2 - View whitespace characters

If you really only want to see trailing spaces, this ST2 plugin will do the trick:

Where can I download IntelliJ IDEA Color Schemes?

If you're just looking for a dark color scheme for IntelliJ IDEA, this is the first link I get in a Google search:

Dark Pastels theme for IntelliJ IDEA Dark Pastels theme for IntelliJ IDEA

Of course, you can tweak either of these two schemes to your satisfaction. Don't feel like you have to stick to the fonts and the colors that the original authors have chosen. We programmers don't get nearly enough change to try our hand at interior decorating to pass up this opportunity.

Is there any reason these won't work in the version you have? As best I can tell, you can simply import any theme that you want.

Loop over html table and get checked checkboxes (JQuery)

The following code snippet enables/disables a button depending on whether at least one checkbox on the page has been checked.
$('input[type=checkbox]').change(function () {
    $('#test > tbody  tr').each(function () {
        if ($('input[type=checkbox]').is(':checked')) {
        } else {
            $('#btnexcellSelect').attr('disabled', 'disabled');
        if ($(this).is(':checked')){
            console.log( $(this).attr('id'));

Here is demo in JSFiddle.

Authenticating in PHP using LDAP through Active Directory

You would think that simply authenticating a user in Active Directory would be a pretty simple process using LDAP in PHP without the need for a library. But there are a lot of things that can complicate it pretty fast:

  • You must validate input. An empty username/password would pass otherwise.
  • You should ensure the username/password is properly encoded when binding.
  • You should be encrypting the connection using TLS.
  • Using separate LDAP servers for redundancy in case one is down.
  • Getting an informative error message if authentication fails.

It's actually easier in most cases to use a LDAP library supporting the above. I ultimately ended up rolling my own library which handles all the above points: LdapTools (Well, not just for authentication, it can do much more). It can be used like the following:

use LdapTools\Configuration;
use LdapTools\DomainConfiguration;
use LdapTools\LdapManager;

$domain = (new DomainConfiguration(''))
    ->setUsername('username') # A separate AD service account used by your app
    ->setServers(['dc1', 'dc2', 'dc3'])
$config = new Configuration($domain);
$ldap = new LdapManager($config);

if (!$ldap->authenticate($username, $password, $message)) {
    echo "Error: $message";
} else {
    // Do something...

The authenticate call above will:

  • Validate that neither the username or password is empty.
  • Ensure the username/password is properly encoded (UTF-8 by default)
  • Try an alternate LDAP server in case one is down.
  • Encrypt the authentication request using TLS.
  • Provide additional information if it failed (ie. locked/disabled account, etc)

There are other libraries to do this too (Such as Adldap2). However, I felt compelled enough to provide some additional information as the most up-voted answer is actually a security risk to rely on with no input validation done and not using TLS.

How to store a large (10 digits) integer?

In addition to all the other answers I'd like to note that if you want to write that number as a literal in your Java code, you'll need to append a L or l to tell the compiler that it's a long constant:

long l1 = 9999999999;  // this won't compile
long l2 = 9999999999L; // this will work

How to store file name in database, with other info while uploading image to server using PHP?

Adding the following avoids problems with quotes in file names, e.g.

"freddy's pic.jpg"

which are acceptable on some operating systems.





What reference do I need to use Microsoft.Office.Interop.Excel in .NET?

Here is super solid solution, you just need have excell.dll in your Debug/Release folder Mine is 77,824 bytes, I downloaded it as a file, this also explain why some people have Debug compiled but Release not or vice versa.


What is the Difference Between read() and recv() , and Between send() and write()?

I just noticed recently that when I used write() on a socket in Windows, it almost works (the FD passed to write() isn't the same as the one passed to send(); I used _open_osfhandle() to get the FD to pass to write()). However, it didn't work when I tried to send binary data that included character 10. write() somewhere inserted character 13 before this. Changing it to send() with a flags parameter of 0 fixed that problem. read() could have the reverse problem if 13-10 are consecutive in the binary data, but I haven't tested it. But that appears to be another possible difference between send() and write().

ORA-01843 not a valid month- Comparing Dates

If you don't need to check exact timestamp, use


otherwise, you can use


Here, you use hard code date,if you directly compare then you must use DD-MM-YY HH24:MI:SS else you might get ORA-01849: hour must be between 1 and 12.

How to change Oracle default data pump directory to import dumpfile?

I want change default directory dumpfile.

You could create a new directory and give it required privileges, for example:

SQL> CREATE DIRECTORY dmpdir AS '/opt/oracle';
Directory created.

SQL> GRANT read, write ON DIRECTORY dmpdir TO scott;
Grant succeeded.

To use the newly created directory, you could just add it as a parameter:


Oracle introduced a default directory from 10g R2, called DATA_PUMP_DIR, that can be used. To check the location, you could look into dba_directories:


-------------------- --------------------------------------------------
DATA_PUMP_DIR        C:\app\Lalit/admin/orcl/dpdump/


How to pick just one item from a generator?

I believe the only way is to get a list from the iterator then get the element you want from that list.

l = list(myfunct())

SQLSTATE[HY093]: Invalid parameter number: number of bound variables does not match number of tokens on line 102

You didn't bind all your bindings here

$sql = "SELECT SQL_CALC_FOUND_ROWS *, UNIX_TIMESTAMP(publicationDate) AS publicationDate     FROM comments WHERE articleid = :art 
ORDER BY " . mysqli_escape_string($order) . " LIMIT :numRows";

$st = $conn->prepare( $sql );
$st->bindValue( ":art", $art, PDO::PARAM_INT );

You've declared a binding called :numRows but you never actually bind anything to it.

UPDATE 2019: I keep getting upvotes on this and that reminded me of another suggestion

Double quotes are string interpolation in PHP, so if you're going to use variables in a double quotes string, it's pointless to use the concat operator. On the flip side, single quotes are not string interpolation, so if you've only got like one variable at the end of a string it can make sense, or just use it for the whole string.

In fact, there's a micro op available here since the interpreter doesn't care about parsing the string for variables. The boost is nearly unnoticable and totally ignorable on a small scale. However, in a very large application, especially good old legacy monoliths, there can be a noticeable performance increase if strings are used like this. (and IMO, it's easier to read anyway)

os.walk without digging into directories below

The same idea with listdir, but shorter:

[f for f in os.listdir(root_dir) if os.path.isfile(os.path.join(root_dir, f))]

In SQL Server, how to create while loop in select

  1. Create function that parses incoming string (say "AABBCC") as a table of strings (in particular "AA", "BB", "CC").
  2. Select IDs from your table and use CROSS APPLY the function with data as argument so you'll have as many rows as values contained in the current row's data. No need of cursors or stored procs.

In Tensorflow, get the names of all the Tensors in a graph

tf.all_variables() can get you the information you want.

Also, this commit made today in TensorFlow Learn that provides a function get_variable_names in estimator that you can use to retrieve all variable names easily.

What is Type-safe?

Many answers here conflate type-safety with static-typing and dynamic-typing. A dynamically typed language (like smalltalk) can be type-safe as well.

A short answer: a language is considered type-safe if no operation leads to undefined behavior. Many consider the requirement of explicit type conversions necessary for a language to be strictly typed, as automatic conversions can sometimes leads to well defined but unexpected/unintuitive behaviors.

Fastest way to list all primes below N

My guess is that the fastest of all ways is to hard code the primes in your code.

So why not just write a slow script that generates another source file that has all numbers hardwired in it, and then import that source file when you run your actual program.

Of course, this works only if you know the upper bound of N at compile time, but thus is the case for (almost) all project Euler problems.


PS: I might be wrong though iff parsing the source with hard-wired primes is slower than computing them in the first place, but as far I know Python runs from compiled .pyc files so reading a binary array with all primes up to N should be bloody fast in that case.

How to Convert Boolean to String

function ToStr($Val=null,$T=0){

    return is_string($Val)?"$Val"

function StrArr($Arr,$T=0)
    foreach($Arr AS $K => $V)
    $Str.=((++$i)?", ":null).(is_string($K)?"\"$K\"":$K)." => ".(is_string($V)?"\"$V\"":@ToStr($V,$T+1));
    return "array( ".($i?@ToStr($Arr):$Str)." )".($T?null:";");

$A = array(1,2,array('a'=>'b'),array('a','b','c'),true,false,ToStr(100));
echo StrArr($A); // OR ToStr($A) // OR ToStr(true) // OR StrArr(true)

How to format html table with inline styles to look like a rendered Excel table?

This is quick-and-dirty (and not formally valid HTML5), but it seems to work -- and it is inline as per the question:

<table border='1' style='border-collapse:collapse'>

No further styling of <tr>/<td> tags is required (for a basic table grid).

How get the base URL via context path in JSF?

JSTL 1.2 variation leveraged from BalusC answer

<c:set var="baseURL" value="${pageContext.request.requestURL.substring(0, pageContext.request.requestURL.length() - pageContext.request.requestURI.length())}${pageContext.request.contextPath}/" />

  <base href="${baseURL}" />

Delete specific line from a text file?

The best way to do this is to open the file in text mode, read each line with ReadLine(), and then write it to a new file with WriteLine(), skipping the one line you want to delete.

There is no generic delete-a-line-from-file function, as far as I know.

how to make a jquery "$.post" request synchronous

From the Jquery docs: you specify the async option to be false to get a synchronous Ajax request. Then your callback can set some data before your mother function proceeds.

Here's what your code would look like if changed as suggested:

beforecreate: function(node,targetNode,type,to) {
         url:    url,
         success: function(result) {
                      if(result.isOk == false)
         async:   false

this is because $.ajax is the only request type that you can set the asynchronousity for

Suppress/ print without b' prefix for bytes in Python 3

If the bytes use an appropriate character encoding already; you could print them directly:



nwritten = os.write(sys.stdout.fileno(), data)  # NOTE: it may write less than len(data) bytes

The simplest way to comma-delimit a list?

for(int i=0, length=list.size(); i<length; i++)
  result+=(i==0?"":", ") + list.get(i);

Select first 4 rows of a data.frame in R

Using the index:


Where the values in the parentheses can be interpreted as either logical, numeric, or character (matching the respective names):

df[row.index, column.index]

Read help(`[`) for more detail on this subject, and also read about index matrices in the Introduction to R.

Convert Month Number to Month Name Function in SQL

A little hacky but should work:

SELECT DATENAME(month, DATEADD(month, @mydate-1, CAST('2008-01-01' AS datetime)))

Android Studio and cannot resolve symbol

enter image description hereI found a shortcut: File - Project Structure - Tab:Dependencies Click on the green + sign, select support-v4 (or any other you need), click OK.

now go to your gradle file and see that is been added

How to reset a form using jQuery with .reset() method

you may try using trigger() Reference Link


onChange and onSelect in DropDownList

To make a robust form, have it load in a useful state and use script to enhance its behaviour. In the following, the select has been replaced by radio buttons (makes life much easier for the user).

The "yes" option is checked by default and the select is enabled. If the user checks either radio button, the select is enabled or disabled accordingly.

<form onclick="this.mySelect1.disabled = this.becomeMember[1].checked;" ... >
  <input type="radio" name="becomeMember" checked>Yes<br>
  <input type="radio" name="becomeMember">No<br>

  <select id="mySelect1">

How to strip comma in Python string

This will strip all commas from the text and left justify it.

for row in inputfile:
    place = row['your_row_number_here'].strip(', ')

? ????? ??????

Convert tuple to list and back

You can have a list of lists. Convert your tuple of tuples to a list of lists using:

level1 = [list(row) for row in level1]


level1 = map(list, level1)

and modify them accordingly.

But a numpy array is cooler.

Why doesn't C++ have a garbage collector?

Implicit garbage collection could have been added in, but it just didn't make the cut. Probably due to not just implementation complications, but also due to people not being able to come to a general consensus fast enough.

A quote from Bjarne Stroustrup himself:

I had hoped that a garbage collector which could be optionally enabled would be part of C++0x, but there were enough technical problems that I have to make do with just a detailed specification of how such a collector integrates with the rest of the language, if provided. As is the case with essentially all C++0x features, an experimental implementation exists.

There is a good discussion of the topic here.

General overview:

C++ is very powerful and allows you to do almost anything. For this reason it doesn't automatically push many things onto you that might impact performance. Garbage collection can be easily implemented with smart pointers (objects that wrap pointers with a reference count, which auto delete themselves when the reference count reaches 0).

C++ was built with competitors in mind that did not have garbage collection. Efficiency was the main concern that C++ had to fend off criticism from in comparison to C and others.

There are 2 types of garbage collection...

Explicit garbage collection:

C++0x will have garbage collection via pointers created with shared_ptr

If you want it you can use it, if you don't want it you aren't forced into using it.

You can currently use boost:shared_ptr as well if you don't want to wait for C++0x.

Implicit garbage collection:

It does not have transparent garbage collection though. It will be a focus point for future C++ specs though.

Why Tr1 doesn't have implicit garbage collection?

There are a lot of things that tr1 of C++0x should have had, Bjarne Stroustrup in previous interviews stated that tr1 didn't have as much as he would have liked.

C# Remove object from list of objects

You can use a while loop to delete item/items matching ChunkID. Here is my suggestion:

public void DeleteChunk(int ChunkID)
   int i = 0;
   while (i < ChunkList.Count) 
      Chunk currentChunk = ChunkList[i];
      if (currentChunk.UniqueID == ChunkID) {
      else {

Reading From A Text File - Batch

Your code "for /f "tokens=* delims=" %%x in (a.txt) do echo %%x" will work on most Windows Operating Systems unless you have modified commands.

So you could instead "cd" into the directory to read from before executing the "for /f" command to follow out the string. For instance if the file "a.txt" is located at C:\documents and settings\%USERNAME%\desktop\a.txt then you'd use the following.

cd "C:\documents and settings\%USERNAME%\desktop"
for /f "tokens=* delims=" %%x in (a.txt) do echo %%x
pause >nul

But since this doesn't work on your computer for x reason there is an easier and more efficient way of doing this. Using the "type" command.

@echo off
color a
cd "C:\documents and settings\%USERNAME%\desktop"
type a.txt
pause >nul

Or if you'd like them to select the file from which to write in the batch you could do the following.

@echo off
color a
echo Choose the file that you want to read.
set file=
set /p file=File:
echo Reading from %file%
type %file%
set re=
set /p re=Y/N?:
if %re%==Y goto :A
if %re%==y goto :A

How do I set a ViewModel on a window in XAML using DataContext property?

Try this instead.

<Window x:Class="BuildAssistantUI.BuildAssistantWindow"
        <VM:MainViewModel />

Convert a byte array to integer in Java and vice versa

You can also use BigInteger for variable length bytes. You can convert it to long, int or short, whichever suits your needs.

new BigInteger(bytes).intValue();

or to denote polarity:

new BigInteger(1, bytes).intValue();

To get bytes back just:

new BigInteger(bytes).toByteArray()

In MySQL, how to copy the content of one table to another table within the same database?

If the table doesn't exist, you can create one with the same schema like so:

CREATE TABLE table2 LIKE table1;

Then, to copy the data over:


How do I indent multiple lines at once in Notepad++?

I have Notepad++ 5.3.1 (UNICODE). I haven't done any magic and it works fine for me as described by you.

Maybe it depends on the (programming/markup/...) "Language"?

Apache - MySQL Service detected with wrong path. / Ports already in use

  • Ok it's very easy actually to solve this...most of you who are presented with this problem probably don't even realize you don't have the full software yet installed :) I tried looking online with little success except some1 mentioned you need to look for those services running already. Forexample problem with filezilla you look in task manager for filezilla and you stop the process then you click the X in the xampp control pannel to install filezilla and then click run and it should start the service normally showing you a green lite with a check mark.

  • Same goes for mysql issues.

  • As for the apache problem, it usualy is a problem with the port being overtaken by skype or some other program, but you can find info how to solve that on the net easily :)

Put icon inside input element in a form

background: url(1.jpg) no-repeat;

add above tags into your CSS file and use the specified class.

Java - Change int to ascii

Do you want to convert ints to chars?:

int yourInt = 33;
char ch = (char) yourInt;
// Output:
// 33
// !

Or do you want to convert ints to Strings?

int yourInt = 33;
String str = String.valueOf(yourInt);

Or what is it that you mean?

How to use Checkbox inside Select Option

Use this code for checkbox list on option menu.

.dropdown-menu input {_x000D_
   margin-right: 10px;_x000D_
<div class="btn-group">_x000D_
    <a href="#" class="btn btn-primary"><i class="fa fa-cogs"></i></a>_x000D_
    <a href="#" class="btn btn-primary dropdown-toggle" data-toggle="dropdown">_x000D_
      <span class="caret"></span>_x000D_
    <ul class="dropdown-menu" style="padding: 10px" id="myDiv">_x000D_
        <li><p><input type="checkbox" value="id1" > OA Number</p></li>_x000D_
        <li><p><input type="checkbox" value="id2" >Customer</p></li>_x000D_
        <li><p><input type="checkbox" value="id3" > OA Date</p></li>_x000D_
        <li><p><input type="checkbox" value="id4" >Product Code</p></li>_x000D_
        <li><p><input type="checkbox" value="id5" >Name</p></li>_x000D_
        <li><p><input type="checkbox" value="id6" >WI Number</p></li>_x000D_
        <li><p><input type="checkbox" value="id7" >WI QTY</p></li>_x000D_
        <li><p><input type="checkbox" value="id8" >Production QTY</p></li>_x000D_
        <li><p><input type="checkbox" value="id9" >PD Sr.No (from-to)</p></li>_x000D_
        <li><p><input type="checkbox" value="id10" > Production Date</p></li>_x000D_
        <button class="btn btn-info" onClick="showTable();">Go</button>_x000D_

Shell equality operators (=, ==, -eq)

== is a bash-specific alias for = and it performs a string (lexical) comparison instead of a numeric comparison. eq being a numeric comparison of course.

Finally, I usually prefer to use the form if [ "$a" == "$b" ]

Multi value Dictionary

I think this is quite overkill for a dictionary semantics, since dictionary is by definition is a collection of keys and its respective values, just like the way we see a book of language dictionary that contains a word as the key and its descriptive meaning as the value.

But you can represent a dictionary that can contain collection of values, for example:


Or a dictionary of a key and the value as a dictionary:


Then you'll have a dictionary that can have multiple values.

"Error: Main method not found in class MyClass, please define the main method as..."

If you are running the correct class and the main is properly defined, also check if you have a class called String defined in the same package. This definition of String class will be considered and since it doesn't confirm to main(java.lang.String[] args), you will get the same exception.

  • It's not a compile time error since compiler just assumes you are defining a custom main method.

Suggestion is to never hide library java classes in your package.

200 PORT command successful. Consider using PASV. 425 Failed to establish connection

Try using the passive command before using ls.

From FTP client, to check if the FTP server supports passive mode, after login, type quote PASV.

Following are connection examples to a vsftpd server with passive mode on and off

vsftpd with pasv_enable=NO:

# ftp localhost
Connected to localhost.localdomain.
220 (vsFTPd 2.3.5)
Name (localhost:john): anonymous
331 Please specify the password.
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> quote PASV
550 Permission denied.

vsftpd with pasv_enable=YES:

# ftp localhost
Connected to localhost.localdomain.
220 (vsFTPd 2.3.5)
Name (localhost:john): anonymous
331 Please specify the password.
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> quote PASV
227 Entering Passive Mode (127,0,0,1,173,104).

Side-by-side plots with ggplot2

One downside of the solutions based on grid.arrange is that they make it difficult to label the plots with letters (A, B, etc.), as most journals require.

I wrote the cowplot package to solve this (and a few other) issues, specifically the function plot_grid():


iris1 <- ggplot(iris, aes(x = Species, y = Sepal.Length)) +
  geom_boxplot() + theme_bw()

iris2 <- ggplot(iris, aes(x = Sepal.Length, fill = Species)) +
  geom_density(alpha = 0.7) + theme_bw() +
  theme(legend.position = c(0.8, 0.8))

plot_grid(iris1, iris2, labels = "AUTO")

enter image description here

The object that plot_grid() returns is another ggplot2 object, and you can save it with ggsave() as usual:

p <- plot_grid(iris1, iris2, labels = "AUTO")
ggsave("plot.pdf", p)

Alternatively, you can use the cowplot function save_plot(), which is a thin wrapper around ggsave() that makes it easy to get the correct dimensions for combined plots, e.g.:

p <- plot_grid(iris1, iris2, labels = "AUTO")
save_plot("plot.pdf", p, ncol = 2)

(The ncol = 2 argument tells save_plot() that there are two plots side-by-side, and save_plot() makes the saved image twice as wide.)

For a more in-depth description of how to arrange plots in a grid see this vignette. There is also a vignette explaining how to make plots with a shared legend.

One frequent point of confusion is that the cowplot package changes the default ggplot2 theme. The package behaves that way because it was originally written for internal lab uses, and we never use the default theme. If this causes problems, you can use one of the following three approaches to work around them:

1. Set the theme manually for every plot. I think it's good practice to always specify a particular theme for each plot, just like I did with + theme_bw() in the example above. If you specify a particular theme, the default theme doesn't matter.

2. Revert the default theme back to the ggplot2 default. You can do this with one line of code:


3. Call cowplot functions without attaching the package. You can also not call library(cowplot) or require(cowplot) and instead call cowplot functions by prepending cowplot::. E.g., the above example using the ggplot2 default theme would become:

## Commented out, we don't call this
# library(cowplot)

iris1 <- ggplot(iris, aes(x = Species, y = Sepal.Length)) +

iris2 <- ggplot(iris, aes(x = Sepal.Length, fill = Species)) +
  geom_density(alpha = 0.7) +
  theme(legend.position = c(0.8, 0.8))

cowplot::plot_grid(iris1, iris2, labels = "AUTO")

enter image description here


  • As of cowplot 1.0, the default ggplot2 theme is not changed anymore.
  • As of ggplot2 3.0.0, plots can be labeled directly, see e.g. here.

JavaScript get element by name

You want this:

function validate() {
    var acc = document.getElementsByName('acc')[0].value;
    var pass = document.getElementsByName('pass')[0].value;

    alert (acc);

How do I split a string so I can access item x?

In my opinion you guys are making it way too complicated. Just create a CLR UDF and be done with it.

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Collections.Generic;

public partial class UserDefinedFunctions {
  public static SqlString SearchString(string Search) {
    List<string> SearchWords = new List<string>();
    foreach (string s in Search.Split(new char[] { ' ' })) {
      if (!s.ToLower().Equals("or") && !s.ToLower().Equals("and")) {

    return new SqlString(string.Join(" OR ", SearchWords.ToArray()));

How do DATETIME values work in SQLite?

Store it in a field of type long. See Date.getTime() and new Date(long)

Setting the selected attribute on a select list using jQuery

If you don't mind modifying your HTML a little to include the value attribute of the options, you can significantly reduce the code necessary to do this:



<option value="B">B</option>

This will be helpful when you want to do something like:

<option value="IL">Illinois</option>

With that, the follow jQuery will make the change:

$("select option[value='B']").attr("selected","selected");

If you decide not to include the use of the value attribute, you will be required to cycle through each option, and manually check its value:

$("select option").each(function(){
  if ($(this).text() == "B")

How do I perform a GROUP BY on an aliased column in MS-SQL Server?

This is what I do.

  SELECT LastName + ', ' + FirstName AS FullName
  FROM customers
) as sub

This technique applies in a straightforward way to your "edit" scenario:

       WHEN LastName IS NULL THEN FirstName
       WHEN LastName IS NOT NULL THEN LastName + ', ' + FirstName
     END AS FullName
  FROM customers
) as sub

Conda version pip install -r requirements.txt --target ./lib

You can run conda install --file requirements.txt instead of the loop, but there is no target directory in conda install. conda install installs a list of packages into a specified conda environment.