Programs & Examples On #Usb

USB is an acronym for Universal Serial Bus, a standard for a serial host-to-device protocol defined by the USB Implementors Forum.

Send raw ZPL to Zebra printer via USB

ZPL is the correct way to go. In most cases it is correct to use a driver that abstracts to GDI commands; however Zebra label printers are a special case. The best way to print to a Zebra printer is to generate ZPL directly. Note that the actual printer driver for a Zebra printer is a "plain text" printer - there is not a "driver" that could be updated or changed in the sense we think of most printers having drivers. It's just a driver in the absolute minimalist sense.

Get List of connected USB Devices

This is a much simpler example for people only looking for removable usb drives.

using System.IO;

foreach (DriveInfo drive in DriveInfo.GetDrives())
    if (drive.DriveType == DriveType.Removable)
        Console.WriteLine(string.Format("({0}) {1}", drive.Name.Replace("\\",""), drive.VolumeLabel));

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

Some people may have the issue where your phone might not immediately get recognized by the computer as an emulator, especially if you're given the option to choose why your phone is connected to the computer on your phone. These options are:

  • charge only
  • Media device (MTP)
  • Camera file transfer (PTP)
  • Share mobile network
  • Install driver

Of these options, choose MTP and follow the instructions found in the quotes of other answers.

  • Hope this helps!

goto run menu -> run configuration. right click on android application on the right side and click new. fill the corresponding details like project name under the android tab. then under the target tab. select 'launch on all compatible devices and then select active devices from the drop down list'. save the configuration and run it by either clicking run on the 'run' button on the bottom right side of the window or close the window and run again

How to change Android usb connect mode to charge only?

In your phone go to Settings->Connect to PC.

There you will see the option Default Connection Type. Select it and set it to your preference.

How do I connect to a terminal to a serial-to-USB device on Ubuntu 10.10 (Maverick Meerkat)?

Putty on ubuntu There is no need to install the driver for PL2303 So only type the command to enable the putty Sudo chmod 666 /dev/ttyUSB0 Done Open the putty.

Controlling a USB power supply (on/off) with Linux

PowerTOP from Intel allows you to toggle devices such as usb peripherals in real-time. These are called 'tunables'.

sudo apt install powertop
sudo powertop
  • Tab over to 'tunables'.
  • Scroll down to your device.
  • Hit enter to toggle power saving mode (Good/Bad)

enter image description here

Note that Bad means the device is always on. Toggling to Good will turn off the device after the preset inactive saving time (default is 2000ms).

See the PowerTOP docs for details on how to make these changes permanent.
It generates the config scripts for you (pretty much as described by other posters on this thread).

NOTE: These scripts do not affect USB pin power (which is always on).
These only send the driver protocol to activate and deactivate a device.

If you want to control pin power, you could use either a supported smart USB hub, or better yet a microcontroller.

Simple way to query connected USB devices info in Python?

For linux, I wrote a script called which you can find here:

It uses pyudev to enumerate all tty devices, and can match on various attributes.

Use the --list option to show all of the know USB serial ports and their attributes. You can filter by VID, PID, serial number, or vendor name. Use --help to see the filtering options. prints the /dev/ttyXXX name rather than the /dev/usb/... name.

USB Debugging option greyed out

Just ran into this on the LG Rebel LTE (LGL44VL). As other answers note, you need to change the USB connection mode to PTP. But my phone's control panels were different from stock Android and didn't have such an option.

The option was hiding in a notification that appeared when I plugged the phone in. I had to open the notification tray and tap a notification labeled

Media Device (MTP)
Tap here for more USB options

Is it possible to program Android to act as physical USB keyboard?

Seems someone have done it by patching the kernel. I just came across a paper titled "Exploiting Smart-Phone USB Connectivity For Fun And Profit" by Angelos Stavrou, Zhaohui Wang, Computer Science Department George Mason University, Fairfax, VA. (available freely by googling the above title). Here the two researchers are investigating the possibility of a compromised android device controlling the attached PC by having the android device presenting itself as an HID device (keyboard). As a proof of concept, it seems that they have successfully patched a kernel doing exactly what you want. They didn't provide detailed steps but anyway I just quote what they said they've done:

.....we developed a special USB gadget driver in addition to existing USB composite interface on the Android Linux kernel using the USB Gadget API for Linux[4]. The UGAL framework helped us implement a simple USB Human Interface Driver (HID) functionality (i.e. device driver) and the glue code between the various kernel APIs. Using the code provided in: “drivers/usb/gadget/composite.c”, we created our own gadget driver as an additional composite USB interface. This driver simulates a USB keyboard device. We can also simulate a USB mouse device sending pre-programmed input command to the desktop system. Therefore, it is straightforward to pose as a normal USB mouse or keyboard device and send predefined command stealthily to simulate malicious interactive user activities. To verify this functionality, in our controlled experiments, we send keycode sequences to perform non-fatal operations and show how such a manipulated device can cause damages In particular, we simulated a Dell USB keyboard (vendorID=413C, productID=2105) sending ”CTRL+ESC” key combination and ”U” and ”Enter” key sequence to reboot the machine. Notice that this only requires USB connection and can gain the ”current user” privilege on the desktop system. With the additional local or remote exploit sent as payload, the malware can escalate the privilege and gain full access of the desktop system.

Is there an equivalent of lsusb for OS X

On Mac OS X, the Xcode developer suite includes the USB application. This is found in /Developer/Applications/Utilities/. USB Prober will allow you to examine the device and interface descriptors.

"The semaphore timeout period has expired" error for USB connection

Too many big files all in one go. Windows barfs. Essentially the copying took too long because you asked too much of the computer and the file locking was locked too long and set a flag off, the flag is a semaphore error.

The computer stuffed itself and choked on it. I saw the RAM memory here get progressively filled with a Cache in RAM. Then when filled the subsystem ground to a halt with a semaphore error.

I have a workaround; copy or transfer fewer files not one humongous block. Break it down into sets of blocks and send across the files one at a time, maybe a few at a time, but not never the lot.


Why does adb return offline after the device string?

Reboot the device. This always fixes it on Mac OS, whereas adb kill-server does not.

How do I find the number of arguments passed to a Bash script?

echo "The number of arguments is: $#"
echo "The total length of all arguments is: ${#a}: "
for var in "$@"
    echo "The length of argument '$var' is: ${#var}"
    (( count++ ))
    (( accum += ${#var} ))
echo "The counted number of arguments is: $count"
echo "The accumulated length of all arguments is: $accum"

How to display multiple images in one figure correctly?

You could try the following:

import matplotlib.pyplot as plt
import numpy as np

def plot_figures(figures, nrows = 1, ncols=1):
    """Plot a dictionary of figures.

    figures : <title, figure> dictionary
    ncols : number of columns of subplots wanted in the display
    nrows : number of rows of subplots wanted in the figure

    fig, axeslist = plt.subplots(ncols=ncols, nrows=nrows)
    for ind,title in zip(range(len(figures)), figures):
        axeslist.ravel()[ind].imshow(figures[title], cmap=plt.jet())
    plt.tight_layout() # optional

# generation of a dictionary of (title, images)
number_of_im = 20
figures = {'im'+str(i): np.random.randint(10, size=(h,w)) for i in range(number_of_im)}

# plot of the images in a figure, with 5 rows and 4 columns
plot_figures(figures, 5, 4)

However, this is basically just copy and paste from here: Multiple figures in a single window for which reason this post should be considered to be a duplicate.

I hope this helps.

How do I create a URL shortener?

Here is one I have created and deployed in Google Cloud console. It is written in Java and Spring boot.

it is

If you want detail, just let me know in comments section, I will edit this post and explain it in detail

What do the python file extensions, .pyc .pyd .pyo stand for?

  1. .py: This is normally the input source code that you've written.
  2. .pyc: This is the compiled bytecode. If you import a module, python will build a *.pyc file that contains the bytecode to make importing it again later easier (and faster).
  3. .pyo: This was a file format used before Python 3.5 for *.pyc files that were created with optimizations (-O) flag. (see the note below)
  4. .pyd: This is basically a windows dll file.

Also for some further discussion on .pyc vs .pyo, take a look at: (I've copied the important part below)

  • When the Python interpreter is invoked with the -O flag, optimized code is generated and stored in ‘.pyo’ files. The optimizer currently doesn't help much; it only removes assert statements. When -O is used, all bytecode is optimized; .pyc files are ignored and .py files are compiled to optimized bytecode.
  • Passing two -O flags to the Python interpreter (-OO) will cause the bytecode compiler to perform optimizations that could in some rare cases result in malfunctioning programs. Currently only __doc__ strings are removed from the bytecode, resulting in more compact ‘.pyo’ files. Since some programs may rely on having these available, you should only use this option if you know what you're doing.
  • A program doesn't run any faster when it is read from a ‘.pyc’ or ‘.pyo’ file than when it is read from a ‘.py’ file; the only thing that's faster about ‘.pyc’ or ‘.pyo’ files is the speed with which they are loaded.
  • When a script is run by giving its name on the command line, the bytecode for the script is never written to a ‘.pyc’ or ‘.pyo’ file. Thus, the startup time of a script may be reduced by moving most of its code to a module and having a small bootstrap script that imports that module. It is also possible to name a ‘.pyc’ or ‘.pyo’ file directly on the command line.


On 2015-09-15 the Python 3.5 release implemented PEP-488 and eliminated .pyo files. This means that .pyc files represent both unoptimized and optimized bytecode.

Get position/offset of element relative to a parent container?

I did it like this in Internet Explorer.

function getWindowRelativeOffset(parentWindow, elem) {
    var offset = {
        left : 0,
        top : 0
    // relative to the target field's document
    offset.left = elem.getBoundingClientRect().left; = elem.getBoundingClientRect().top;
    // now we will calculate according to the current document, this current
    // document might be same as the document of target field or it may be
    // parent of the document of the target field
    var childWindow = elem.document.frames.window;
    while (childWindow != parentWindow) {
        offset.left = offset.left + childWindow.frameElement.getBoundingClientRect().left; = + childWindow.frameElement.getBoundingClientRect().top;
        childWindow = childWindow.parent;

    return offset;

=================== you can call it like this

getWindowRelativeOffset(top, inputElement);

I focus on IE only as per my focus but similar things can be done for other browsers.

What is an unsigned char?

If you want to use a character as a small integer, the safest way to do it is with the int8_tand uint8_t types.

no operator "<<" matches these operands

You're not including the standard <string> header.

You got [un]lucky that some of its pertinent definitions were accidentally made available by the other standard headers that you did include ... but operator<< was not.

WPF button click in C# code

The following should do the trick:

btn.Click += btn1_Click;

How to detect when keyboard is shown and hidden

Swift 4:

  NotificationCenter.default.addObserver( self, selector: #selector(ControllerClassName.keyboardWillShow(_:)),
  name: Notification.Name.UIKeyboardWillShow,
  object: nil)
  NotificationCenter.default.addObserver(self, selector: #selector(ControllerClassName.keyboardWillHide(_:)),
  name: Notification.Name.UIKeyboardWillHide,
  object: nil)

Next, adding method to stop listening for notifications when the object’s life ends:-

Then add the promised methods from above to the view controller:
deinit {
func adjustKeyboardShow(_ open: Bool, notification: Notification) {
  let userInfo = notification.userInfo ?? [:]
  let keyboardFrame = (userInfo[UIKeyboardFrameBeginUserInfoKey] as! NSValue).cgRectValue
  let height = (keyboardFrame.height + 20) * (open ? 1 : -1)
  scrollView.contentInset.bottom += height
  scrollView.scrollIndicatorInsets.bottom += height

@objc func keyboardWillShow(_ notification: Notification) {
  adjustKeyboardShow(true, notification: notification)
@objc func keyboardWillHide(_ notification: Notification) {
  adjustKeyboardShow(false, notification: notification)

How to add extra whitespace in PHP?

to make your code look better when viewing source

$variable = 'foo';
echo "this is my php variable $variable \n";
echo "this is another php echo here $variable\n";

your code when view source will look like, with nice line returns thanks to \n

this is my php variable foo
this is another php echo here foo

How do I dynamically change the content in an iframe using jquery?

var handle = setInterval(changeIframe, 30000);
var sites = ["", ""];
var index = 0;

function changeIframe() {
  $('#frame')[0].src = sites[index++];
  index = index >= sites.length ? 0 : index;

How do I set the default Java installation/runtime (Windows)?

After many attempts, I found the junction approach more convenient. This is very similar on how this problem is solved in linux.

Basically it consists of having a link between c:\tools\java\default and the actual version of java you want to use as default in your system.

How to set it:

  1. Download junction and make sure to put it in your PATH environment variable
  2. Set your environment this way: - PATH pointing to ONLY to this jre c:\tools\java\default\bin - JAVA_HOME pointing to `c:\tools\java\default
  3. Store all your jre-s in one folder like (if you do that in your Program FIles folder you may encounter some
    • C:\tools\Java\JRE_1.6
    • C:\tools\Java\JRE_1.7
    • C:\tools\Java\JRE_1.8
  4. Open a command prompt and cd to C:\tools\Java\
  5. Execute junction default JRE_1.6

This will create a junction (which is more or less like a symbolic link in linux) between C:\tools\java\default and C:\tools\java\JRE_1.6

In this way you will always have your default java in c:\tools\java\default.

If you then need to change your default java to the 1.8 version you just need to execute

junction -d default
junction default JRE_1.8 

Then you can have batch files to do that without command prompt like set_jdk8.bat set_jdk7.bat

As suggested from @????????????

EDIT: From windows vista, you can use mklink /J default JRE_1.8

What is difference between XML Schema and DTD?

DTD is pretty much deprecated because it is limited in its usefulness as a schema language, doesn't support namespace, and does not support data type. In addition, DTD's syntax is quite complicated, making it difficult to understand and maintain..

Eclipse: Java was started but returned error code=13

This error occurs because your Eclipse version is 64-bit. You should download and install 64-bit JRE and add the path to it in eclipse.ini. For example:

C:\Program Files\Java\jre1.8.0_45\bin\javaw.exe

Note: The -vm parameter should be just before -vmargs and the path should be on a separate line. It should be the full path to the javaw.exe file. Do not enclose the path in double quotes (").

If your Eclipse is 32-bit, install a 32-bit JRE and use the path to its javaw.exe file.

Start script missing error when running npm start

Try with these steps :

npm rm -g create-react-app

npm install -g create-react-app

npx create-react-app my-app

Definitely this works!!

Python slice first and last element in list

You can use something like

y[::max(1, len(y)-1)]

if you really want to use slicing. The advantage of this is that it cannot give index errors and works with length 1 or 0 lists as well.

How to call javascript function from button click event

You're already prepending the hash sign in your showDialog() function, and you're missing single quotes in your second code snippet. You should also return false from the handler to prevent a postback from occurring. Try:

<asp:Button ID="ButtonAdd" runat="server" Text="Add"
    OnClientClick="showDialog('<%=addPerson.ClientID %>'); return false;" />

Is floating point math broken?

Normal arithmetic is base-10, so decimals represent tenths, hundredths, etc. When you try to represent a floating-point number in binary base-2 arithmetic, you are dealing with halves, fourths, eighths, etc.

In the hardware, floating points are stored as integer mantissas and exponents. Mantissa represents the significant digits. Exponent is like scientific notation but it uses a base of 2 instead of 10. For example 64.0 would be represented with a mantissa of 1 and exponent of 6. 0.125 would be represented with a mantissa of 1 and an exponent of -3.

Floating point decimals have to add up negative powers of 2

0.1b = 0.5d
0.01b = 0.25d
0.001b = 0.125d
0.0001b = 0.0625d
0.00001b = 0.03125d

and so on.

It is common to use a error delta instead of using equality operators when dealing with floating point arithmetic. Instead of

if(a==b) ...

you would use

delta = 0.0001; // or some arbitrarily small amount
if(a - b > -delta && a - b < delta) ...

Convert int to a bit array in .NET

Use the BitArray class.

int value = 3;
BitArray b = new BitArray(new int[] { value });

If you want to get an array for the bits, you can use the BitArray.CopyTo method with a bool[] array.

bool[] bits = new bool[b.Count];
b.CopyTo(bits, 0);

Note that the bits will be stored from least significant to most significant, so you may wish to use Array.Reverse.

And finally, if you want get 0s and 1s for each bit instead of booleans (I'm using a byte to store each bit; less wasteful than an int):

byte[] bitValues = bits.Select(bit => (byte)(bit ? 1 : 0)).ToArray();

How do I upgrade PHP in Mac OS X?

You can use curl to update php version.

curl -s | bash -s 7.3

Last Step:

export PATH=/usr/local/php5/bin:$PATH

Check the upgraded version

php -v

PHP error: Notice: Undefined index:

Assure you have used method="post" in the form you are sending data from.

How to Completely Uninstall Xcode and Clear All Settings

For a complete removal of Xcode 10 delete the following:

  1. /Applications/
  2. ~/Library/Caches/
  3. ~/Library/Developer
  4. ~/Library/MobileDevice
  5. ~/Library/Preferences/
  6. /Library/Preferences/
  7. /System/Library/Receipts/
  8. /System/Library/Receipts/
  9. /System/Library/Receipts/
  10. /System/Library/Receipts/
  11. /private/var/db/receipts/

But instead of 11, open up /private/var/in the Finder and search for "Xcode" to see all the 'dna' left behind... and selectively clean that out too. I would post the pathnames but they will include randomized folder names which will not be the same from my Mac to yours.

but if you don't want to lose all of your customizations, consider saving these files or folders before deleting anything:

  1. ~/Library/Developer/Xcode/UserData/CodeSnippets
  2. ~/Library/Developer/Xcode/UserData/FontAndColorThemes
  3. ~/Library/Developer/Xcode/UserData/KeyBindings
  4. ~/Library/Developer/Xcode/Templates
  5. ~/Library/Preferences/
  6. ~/Library/MobileDevice/Provisioning Profiles

Update Rows in SSIS OLEDB Destination

You can't do a bulk-update in SSIS within a dataflow task with the OOB components.

The general pattern is to identify your inserts, updates and deletes and push the updates and deletes to a staging table(s) and after the Dataflow Task, use a set-based update or delete in an Execute SQL Task. Look at Andy Leonard's Stairway to Integration Services series. Scroll about 3/4 the way down the article to "Set-Based Updates" to see the pattern.

Stage data

Set based updates

enter image description here

You'll get much better performance with a pattern like this versus using the OLE DB Command transformation for anything but trivial amounts of data.

If you are into third party tools, I believe CozyRoc and I know PragmaticWorks have a merge destination component.

PHP page redirect

   echo '<META HTTP-EQUIV=REFRESH CONTENT="1; '.$url.'">';

this works for me fine.

How to set environment variables in Python?

Environment variables must be strings, so use

os.environ["DEBUSSY"] = "1"

to set the variable DEBUSSY to the string 1.

To access this variable later, simply use:


Child processes automatically inherit the environment variables of the parent process -- no special action on your part is required.

IndexError: too many indices for array

The message that you are getting is not for the default Exception of Python:

For a fresh python list, IndexError is thrown only on index not being in range (even docs say so).

>>> l = []
>>> l[1]
IndexError: list index out of range

If we try passing multiple items to list, or some other value, we get the TypeError:

>>> l[1, 2]
TypeError: list indices must be integers, not tuple

>>> l[float('NaN')]
TypeError: list indices must be integers, not float

However, here, you seem to be using matplotlib that internally uses numpy for handling arrays. On digging deeper through the codebase for numpy, we see:

static NPY_INLINE npy_intp
unpack_tuple(PyTupleObject *index, PyObject **result, npy_intp result_n)
    npy_intp n, i;
    n = PyTuple_GET_SIZE(index);
    if (n > result_n) {
                        "too many indices for array");
        return -1;
    for (i = 0; i < n; i++) {
        result[i] = PyTuple_GET_ITEM(index, i);
    return n;

where, the unpack method will throw an error if it the size of the index is greater than that of the results.

So, Unlike Python which raises a TypeError on incorrect Indexes, Numpy raises the IndexError because it supports multidimensional arrays.

How do you clear a stringstream variable?

You can clear the error state and empty the stringstream all in one line

std::stringstream().swap(m); // swap m with a default constructed stringstream

This effectively resets m to a default constructed state

How to printf "unsigned long" in C?

%lu is the correct format for unsigned long. Sounds like there are other issues at play here, such as memory corruption or an uninitialized variable. Perhaps show us a larger picture?

Convert a string to integer with decimal in Python


will give you an integer value, but a float type. With Python's duck typing, however, the actual type is usually not very relevant. This will also round the value, which you might not want. Replace 'round' with 'int' and you'll have it just truncated and an actual int. Like this:


But, again, actual 'type' is usually not that important.

How to use opencv in using Gradle?

The OpenCV Android SDK has an example file with helpful comments:

// Notes about integration OpenCV into existed Android Studio application project are below (application 'app' module should exist).
// This file is located in <OpenCV-android-sdk>/sdk directory (near 'etc', 'java', 'native' subdirectories)
// Add module into Android Studio application project:
// - Android Studio way:
//   (will copy almost all OpenCV Android SDK into your project, ~200Mb)
//   Import module: Menu -> "File" -> "New" -> "Module" -> "Import Gradle project":
//   Source directory: select this "sdk" directory
//   Module name: ":opencv"
// - or attach library module from OpenCV Android SDK
//   (without copying into application project directory, allow to share the same module between projects)
//   Edit "settings.gradle" and add these lines:
//   def opencvsdk='<path_to_opencv_android_sdk_rootdir>'
//   // You can put declaration above into file instead (including file in HOME directory),
//   // but without 'def' and apostrophe symbols ('): opencvsdk=<path_to_opencv_android_sdk_rootdir>
//   include ':opencv'
//   project(':opencv').projectDir = new File(opencvsdk + '/sdk')
// Add dependency into application module:
// - Android Studio way:
//   "Open Module Settings" (F4) -> "Dependencies" tab
// - or add "project(':opencv')" dependency into app/build.gradle:
//   dependencies {
//       implementation fileTree(dir: 'libs', include: ['*.jar'])
//       ...
//       implementation project(':opencv')
//   }
// Load OpenCV native library before using:
// - avoid using of "OpenCVLoader.initAsync()" approach - it is deprecated
//   It may load library with different version (from OpenCV Android Manager, which is installed separatelly on device)
// - use "System.loadLibrary("opencv_java3")" or "OpenCVLoader.initDebug()"
//   TODO: Add accurate API to load OpenCV native library
// Native C++ support (necessary to use OpenCV in native code of application only):
// - Use find_package() in app/CMakeLists.txt:
//   find_package(OpenCV 3.4 REQUIRED java)
//   ...
//   target_link_libraries(native-lib ${OpenCV_LIBRARIES})
// - Add "OpenCV_DIR" and enable C++ exceptions/RTTI support via app/build.gradle
//   Documentation about CMake options:
//   defaultConfig {
//       ...
//       externalNativeBuild {
//           cmake {
//               cppFlags "-std=c++11 -frtti -fexceptions"
//               arguments "-DOpenCV_DIR=" + opencvsdk + "/sdk/native/jni" // , "-DANDROID_ARM_NEON=TRUE"
//           }
//       }
//   }
// - (optional) Limit/filter ABIs to build ('android' scope of 'app/build.gradle'):
//   Useful information: (Configure separate APKs per ABI)
//   splits {
//       abi {
//           enable true
//           reset()
//           include 'armeabi-v7a' // , 'x86', 'x86_64', 'arm64-v8a'
//           universalApk false
//       }
//   }

apply plugin: ''

println "OpenCV: " + project.buildscript.sourceFile

android {
    compileSdkVersion 27
    //buildToolsVersion "27.0.3" // not needed since

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 21

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_6
        targetCompatibility JavaVersion.VERSION_1_6

    sourceSets {
        main {
            jniLibs.srcDirs = ['native/libs']
            java.srcDirs = ['java/src']
            aidl.srcDirs = ['java/src']
            res.srcDirs = ['java/res']
            manifest.srcFile 'java/AndroidManifest.xml'

dependencies {

Scp command syntax for copying a folder from local machine to a remote server

In stall PuTTY in our system and set the environment variable PATH Pointing to putty path. open the command prompt and move to putty folder. Using PSCP command

Please check this

What are the differences between C, C# and C++ in terms of real-world applications?

C is the bare-bones, simple, clean language that makes you do everything yourself. It doesn't hold your hand, it doesn't stop you from shooting yourself in the foot. But it has everything you need to do what you want.

C++ is C with classes added, and then a whole bunch of other things, and then some more stuff. It doesn't hold your hand, but it'll let you hold your own hand, with add-on GC, or RAII and smart-pointers. If there's something you want to accomplish, chances are there's a way to abuse the template system to give you a relatively easy syntax for it. (moreso with C++0x). This complexity also gives you the power to accidentally create a dozen instances of yourself and shoot them all in the foot.

C# is Microsoft's stab at improving on C++ and Java. Tons of syntactical features, but no where near the complexity of C++. It runs in a full managed environment, so memory management is done for you. It does let you "get dirty" and use unsafe code if you need to, but it's not the default, and you have to do some work to shoot yourself.

link_to image tag. how to add class to a tag

You can also try this

<li><%= link_to "", application_welcome_path, class: "navbar-brand metas-logo"    %></li>

Where "metas-logo" is a css class with a background image

Could not resolve placeholder in string value

In your configuration you have 2 PropertySourcesPlaceholderConfigurer instances.


<bean class="">
    <property name="environment">
        <bean class=""/>


<context:property-placeholder location=""/>

By default a PlaceholderConfigurer is going to fail-fast, so if a placeholder cannot be resolved it will throw an exception. The instance from the applicationContext.xml file has no properties and as such will fail on all placeholders.

Solution: Remove the one from applicationContext.xml as it doesn't add anything it only breaks things.

C pointer to array/array of pointers disambiguation

I think we can use the simple rule ..

example int * (*ptr)()[];
start from ptr 

" ptr is a pointer to " go towards right ..its ")" now go left its a "(" come out go right "()" so " to a function which takes no arguments " go left "and returns a pointer " go right "to an array" go left " of integers "

In Python, how do I loop through the dictionary and change the value if it equals something?

You could create a dict comprehension of just the elements whose values are None, and then update back into the original:

tmp = dict((k,"") for k,v in mydict.iteritems() if v is None)

Update - did some performance tests

Well, after trying dicts of from 100 to 10,000 items, with varying percentage of None values, the performance of Alex's solution is across-the-board about twice as fast as this solution.

Specify path to node_modules in package.json

I'm not sure if this is what you had in mind, but I ended up on this question because I was unable to install node_modules inside my project dir as it was mounted on a filesystem that did not support symlinks (a VM "shared" folder).

I found the following workaround:

  1. Copy the package.json file to a temp folder on a different filesystem
  2. Run npm install there
  3. Copy the resulting node_modules directory back into the project dir, using cp -r --dereference to expand symlinks into copies.

I hope this helps someone else who ends up on this question when looking for a way to move node_modules to a different filesystem.

Other options

There is another workaround, which I found on the github issue that @Charminbear linked to, but this doesn't work with grunt because it does not support NODE_PATH as per

lets say you have /media/sf_shared and you can't install symlinks in there, which means you can't actually npm install from /media/sf_shared/myproject because some modules use symlinks.

  • $ mkdir /home/dan/myproject && cd /home/dan/myproject
  • $ ln -s /media/sf_shared/myproject/package.json (you can symlink in this direction, just can't create one inside of /media/sf_shared)
  • $ npm install
  • $ cd /media/sf_shared/myproject
  • $ NODE_PATH=/home/dan/myproject/node_modules node index.js

Is it possible to style a mouseover on an image map using CSS?

I don't think this is possible just using CSS (not cross browser at least) but the jQuery plugin ImageMapster will do what you're after. You can outline, colour in or use an alternative image for hover/active states on an image map.

Disable Pinch Zoom on Mobile Web

To everyone who said that this is a bad idea I want to say it is not always a bad one. Sometimes it is very boring to have to zoom out to see all the content. For example when you type on an input on iOS it zooms to get it in the center of the screen. You have to zoom out after that cause closing the keyboard does not do the work. Also I agree that when you put many I hours in making a great layout and user experience you don't want it to be messed up by a zoom.

But the other argument is valuable as well for people with vision issues. However In my opinion if you have issues with your eyes you are already using the zooming features of the system so there is no need to disturb the content.

Django ManyToMany filter()

another way to do this is by going through the intermediate table. I'd express this within the Django ORM like this:

UserZone = User.zones.through

# for a single zone
users_in_zone = User.objects.filter(

# for multiple zones
users_in_zones = User.objects.filter(
  id__in=UserZone.objects.filter(zone__in=[zone1, zone2, zone3]).values('user'))

it would be nice if it didn't need the .values('user') specified, but Django (version 3.0.7) seems to need it.

the above code will end up generating SQL that looks something like:

SELECT * FROM users WHERE id IN (SELECT user_id FROM userzones WHERE zone_id IN (1,2,3))

which is nice because it doesn't have any intermediate joins that could cause duplicate users to be returned

Check if any type of files exist in a directory using BATCH script

You can use this

@echo off
for /F %%i in ('dir /b "c:\test directory\*.*"') do (
   echo Folder is NON empty
   goto :EOF
echo Folder is empty or does not exist

Taken from here.

That should do what you need.

How to Query an NTP Server using C#?

This is a optimized version of the function which removes dependency on BitConverter function and makes it compatible with NETMF (.NET Micro Framework)

public static DateTime GetNetworkTime()
    const string ntpServer = "";
    var ntpData = new byte[48];
    ntpData[0] = 0x1B; //LeapIndicator = 0 (no warning), VersionNum = 3 (IPv4 only), Mode = 3 (Client Mode)

    var addresses = Dns.GetHostEntry(ntpServer).AddressList;
    var ipEndPoint = new IPEndPoint(addresses[0], 123);
    var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);


    ulong intPart = (ulong)ntpData[40] << 24 | (ulong)ntpData[41] << 16 | (ulong)ntpData[42] << 8 | (ulong)ntpData[43];
    ulong fractPart = (ulong)ntpData[44] << 24 | (ulong)ntpData[45] << 16 | (ulong)ntpData[46] << 8 | (ulong)ntpData[47];

    var milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000L);
    var networkDateTime = (new DateTime(1900, 1, 1)).AddMilliseconds((long)milliseconds);

    return networkDateTime;

How to switch activity without animation in Android?

If your context is an activity you can call overridePendingTransition:

Call immediately after one of the flavors of startActivity(Intent) or finish to specify an explicit transition animation to perform next.

So, programmatically:

this.startActivity(new Intent(v.getContext(), newactivity.class));
this.overridePendingTransition(0, 0);

Python argparse: default value or specified value

import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--example', nargs='?', const=1, type=int)
args = parser.parse_args()

% --example
% --example 2

  • nargs='?' means 0-or-1 arguments
  • const=1 sets the default when there are 0 arguments
  • type=int converts the argument to int

If you want to set example to 1 even if no --example is specified, then include default=1. That is, with

parser.add_argument('--example', nargs='?', const=1, type=int, default=1)



PHP Regex to get youtube video ID?

if (preg_match('![?&]{1}v=([^&]+)!', $url . '&', $m))
    $video_id = $m[1];

Oracle query to fetch column names

The query to use with Oracle is:

String sqlStr="select COLUMN_NAME from ALL_TAB_COLUMNS where TABLE_NAME='"+_db+".users' and COLUMN_NAME not in ('password','version','id')"

Never heard of HQL for such queries. I assume it doesn't make sense for ORM implementations to deal with it. ORM is an Object Relational Mapping, and what you're looking for is metadata mapping... You wouldn't use HQL, rather use API methods for this purpose, or direct SQL. For instance, you can use JDBC DatabaseMetaData.

I think tablespace has nothing to do with schema. AFAIK tablespaces are mainly used for logical internal technical purposes which should bother DBAs. For more information regarding tablespaces, see Oracle doc.

How to convert a string to number in TypeScript?

As shown by other answers here, there are multiple ways to do the conversion:


I'd like to mention one more thing on parseInt though.

When using parseInt, it makes sense to always pass the radix parameter. For decimal conversion, that is 10. This is the default value for the parameter, which is why it can be omitted. For binary, it's a 2 and 16 for hexadecimal. Actually, any radix between and including 2 and 36 works.

parseInt('123')         // 123 (don't do this)
parseInt('123', 10)     // 123 (much better)

parseInt('1101', 2)     // 13
parseInt('0xfae3', 16)  // 64227

In some JS implementations, parseInt parses leading zeros as octal:

Although discouraged by ECMAScript 3 and forbidden by ECMAScript 5, many implementations interpret a numeric string beginning with a leading 0 as octal. The following may have an octal result, or it may have a decimal result. Always specify a radix to avoid this unreliable behavior.


The fact that code gets clearer is a nice side effect of specifying the radix parameter.

Since parseFloat only parses numeric expressions in radix 10, there's no need for a radix parameter here.

More on this:

Two values from one input in python?

The solution I found is the following:

Ask the user to enter two numbers separated by a comma or other character

value = input("Enter 2 numbers (separated by a comma): ")

Then, the string is split: n takes the first value and m the second one

n,m = value.split(',')

Finally, to use them as integers, it is necessary to convert them

n, m = int(n), int(m)

What does href expression <a href="javascript:;"></a> do?

An <a> element is invalid HTML unless it has either an href or name attribute.

If you want it to render correctly as a link (ie underlined, hand pointer, etc), then it will only do so if it has a href attribute.

Code like this is therefore sometimes used as a way of making a link, but without having to provide an actual URL in the href attribute. The developer obviously wanted the link itself not to do anything, and this was the easiest way he knew.

He probably has some javascript event code elsewhere which is triggered when the link is clicked, and that will be what he wants to actually happen, but he wants it to look like a normal <a> tag link.

Some developers use href='#' for the same purpose, but this causes the browser to jump to the top of the page, which may not be wanted. And he couldn't simply leave the href blank, because href='' is a link back to the current page (ie it causes a page refresh).

There are ways around these things. Using an empty bit of Javascript code in the href is one of them, and although it isn't the best solution, it does work.

Random numbers with Math.random() in Java

Math.random() generates a number between 0 (inclusive) and 1 (exclusive).

So (int)(Math.random() * max) ranges from 0 to max-1 inclusive.

Then (int)(Math.random() * max) + min ranges from min to max + min - 1, which is not what you want.

Google's formula is correct.

Find the files existing in one directory but not in the other

vim's DirDiff plugin is another very useful tool for comparing directories.

vim -c "DirDiff dir1 dir2"

It not only lists which files are different between the directories, but also allows you to inspect/modify with vimdiff the files that are different.

Reverting to a previous revision using TortoiseSVN

Here's another method that's unorthodox, but works*.

I recently found myself in a situation where I'd checked in breaking code, knowing that I couldn't update our production code to it until all the integration work had taken place (in retrospect this was a bad decision, but we didn't expect to get stalled out, but other projects took precedence). That was several months ago, and the integration has been stalled for that entire time. Along comes a requirement to change the base code and get it into production last week without the breaking change.

Here's what we did:

After verifying that the new requirement doesn't break anything when using the revision before my check in, I made a copy of the working directory containing the new code. Then I deleted everything in the working directory and checked out the revision I wanted to it. Then I deleted all the files I'd just checked out, and copied in the files from the working copy. Then I committed that change, effectively wiping out the breaking change from the repository and getting the production code in place as the head revision. We still have the breaking change available, but it's no longer in the head revision so we can move forward to production.

*I don't recommend this method, but if you find yourself in a similar situation, it's a way out that's not too painful.

Swipe ListView item From right to left show delete button

see there link was very nice and simple. its working fine... u don't want any library its working fine. click here

OnTouchListener gestureListener = new View.OnTouchListener() {
    private int padding = 0;
    private int initialx = 0;
    private int currentx = 0;
    private  ViewHolder viewHolder;

    public boolean onTouch(View v, MotionEvent event) {
        if ( event.getAction() == MotionEvent.ACTION_DOWN) {
            padding = 0;
            initialx = (int) event.getX();
            currentx = (int) event.getX();
            viewHolder = ((ViewHolder) v.getTag());
        if ( event.getAction() == MotionEvent.ACTION_MOVE) {
            currentx = (int) event.getX();
            padding = currentx - initialx;
        if ( event.getAction() == MotionEvent.ACTION_UP || 
                     event.getAction() == MotionEvent.ACTION_CANCEL) {
            padding = 0;
            initialx = 0;
            currentx = 0;
        if(viewHolder != null) {
            if(padding == 0) {
                v.setBackgroundColor(0xFF000000 );  
            if(padding > 75) {
                viewHolder.running = true;
                v.setBackgroundColor(0xFF00FF00 );  
            if(padding < -75) {
                viewHolder.running = false;
                v.setBackgroundColor(0xFFFF0000 );  

            v.setPadding(padding, 0,0, 0);

        return true;

How to set the default value of an attribute on a Laravel model

You can set Default attribute in Model also>

protected $attributes = [
        'status' => self::STATUS_UNCONFIRMED,
        'role_id' => self::ROLE_PUBLISHER,

You can find the details in these links

1.) How to set a default attribute value for a Laravel / Eloquent model?


You can also Use Accessors & Mutators for this You can find the details in the Laravel documentation 1.)


3.) Universal accessors and mutators in Laravel 4

Even though JRE 8 is installed on my MAC -" No Java Runtime present,requesting to install " gets displayed in terminal

Below is worked for me on macos mojave 10.14.6 version

I installed current jdk(

Then do respectively;

  • vim .bash_profile
  • add "export JAVA_HOME=$(/usr/libexec/java_home)" to bash_profile
  • source .bash_profile

it is done. And you can check the version with java -version command.

Double border with different color

Try below structure for applying two color border,

<div class="white">
    <div class="grey">

    border: 2px solid white;   

    border: 1px solid grey;   

Insert line after first match using sed

I had to do this recently as well for both Mac and Linux OS's and after browsing through many posts and trying many things out, in my particular opinion I never got to where I wanted to which is: a simple enough to understand solution using well known and standard commands with simple patterns, one liner, portable, expandable to add in more constraints. Then I tried to looked at it with a different perspective, that's when I realized i could do without the "one liner" option if a "2-liner" met the rest of my criteria. At the end I came up with this solution I like that works in both Ubuntu and Mac which i wanted to share with everyone:

insertLine=$(( $(grep -n "foo" sample.txt | cut -f1 -d: | head -1) + 1 ))
sed -i -e "$insertLine"' i\'$'\n''bar'$'\n' sample.txt

In first command, grep looks for line numbers containing "foo", cut/head selects 1st occurrence, and the arithmetic op increments that first occurrence line number by 1 since I want to insert after the occurrence. In second command, it's an in-place file edit, "i" for inserting: an ansi-c quoting new line, "bar", then another new line. The result is adding a new line containing "bar" after the "foo" line. Each of these 2 commands can be expanded to more complex operations and matching.

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

AndroidStudio Menu:

Build/Clean Project

Update old dependencies

Swift double to string

var b = String(stringInterpolationSegment: a)

This works for me. You may have a try

How can I remove the last character of a string in python?

Answering the question: to remove the last character, just use:string = string[:-1].

If you want to remove the last '\' if there is one (or if there is more than one):

while string[-1]=='\\':
    string = string[:-1]

If it's a path, then use the os.path functions:

dir = "dir1\\dir2\\file.jpg\\"   #I'm using windows by the way

although I would 'add' a slash in the end to prevent missing the filename in case there's no slash at the end of the original string:

dir = "dir1\\dir2\\file.jpg"
os.path.dirname(dir + "\\")

When using abspath, (if the path isn't absolute I guess,) will add the current working directory to the path.


Django: Model Form "object has no attribute 'cleaned_data'"

At times, if we forget the

return self.cleaned_data 

in the clean function of django forms, we will not have any data though the form.is_valid() will return True.

Centering the image in Bootstrap

.img-responsive {
     margin: 0 auto;

you can write like above code in your document so no need to add one another class in image tag.

How do we control web page caching, across all browsers?

If you're facing download problems with IE6-IE8 over SSL and cache:no-cache header (and similar values) with MS Office files you can use cache:private,no-store header and return file on POST request. It works.

setTimeout or setInterval?


setInterval() is a time interval based code execution method that has the native ability to repeatedly run a specified script when the interval is reached. It should not be nested into its callback function by the script author to make it loop, since it loops by default. It will keep firing at the interval unless you call clearInterval().

If you want to loop code for animations or on a clock tick, then use setInterval().

function doStuff() {
    alert("run your code here when time interval is reached");
var myTimer = setInterval(doStuff, 5000);


setTimeout() is a time based code execution method that will execute a script only one time when the interval is reached. It will not repeat again unless you gear it to loop the script by nesting the setTimeout() object inside of the function it calls to run. If geared to loop, it will keep firing at the interval unless you call clearTimeout().

function doStuff() {
    alert("run your code here when time interval is reached");
var myTimer = setTimeout(doStuff, 5000);

If you want something to happen one time after a specified period of time, then use setTimeout(). That is because it only executes one time when the specified interval is reached.

Angularjs $q.all

In javascript there are no block-level scopes only function-level scopes:

Read this article about javaScript Scoping and Hoisting.

See how I debugged your code:

var deferred = $q.defer();
deferred.count = i;

console.log(deferred.count); // 0,1,2,3,4,5 --< all deferred objects

// some code

   console.log(deferred.count); // 5,5,5,5,5,5 --< only the last deferred object
  • When you write var deferred= $q.defer(); inside a for loop it's hoisted to the top of the function, it means that javascript declares this variable on the function scope outside of the for loop.
  • With each loop, the last deferred is overriding the previous one, there is no block-level scope to save a reference to that object.
  • When asynchronous callbacks (success / error) are invoked, they reference only the last deferred object and only it gets resolved, so $q.all is never resolved because it still waits for other deferred objects.
  • What you need is to create an anonymous function for each item you iterate.
  • Since functions do have scopes, the reference to the deferred objects are preserved in a closure scope even after functions are executed.
  • As #dfsq commented: There is no need to manually construct a new deferred object since $http itself returns a promise.

Solution with angular.forEach:

Here is a demo plunker:

UploadService.uploadQuestion = function(questions){

    var promises = [];

    angular.forEach(questions , function(question) {

        var promise = $http({
            url   : 'upload/question',
            method: 'POST',
            data  : question



    return $q.all(promises);

My favorite way is to use Array#map:

Here is a demo plunker:

UploadService.uploadQuestion = function(questions){

    var promises = {

        return $http({
            url   : 'upload/question',
            method: 'POST',
            data  : question


    return $q.all(promises);

MySQL Cannot drop index needed in a foreign key constraint

Because you have to have an index on a foreign key field you can just create a simple index on the field 'AID'

CREATE INDEX aid_index ON mytable (AID);

and only then drop the unique index 'AID'


Excel VBA Open a Folder

I use this to open a workbook and then copy that workbook's data to the template.

Private Sub CommandButton24_Click()
Set Template = ActiveWorkbook
 With Application.FileDialog(msoFileDialogOpen)
    .InitialFileName = "I:\Group - Finance" ' Yu can select any folder you want
    .Title = "Your Title"
    If Not .Show Then
        MsgBox "No file selected.": Exit Sub
    End If
    Workbooks.OpenText .SelectedItems(1)

'The below is to copy the file into a new sheet in the workbook and paste those values in sheet 1

    Set myfile = ActiveWorkbook
    ActiveWorkbook.Sheets(1).Copy after:=ThisWorkbook.Sheets(1)

End With

Spring Security redirect to previous page after successful login

I have following solution and it worked for me.

Whenever login page is requested, write the referer value to the session:

@RequestMapping(value="/login", method = RequestMethod.GET)
public String login(ModelMap model,HttpServletRequest request) {

    String referrer = request.getHeader("Referer");
        request.getSession().setAttribute("url_prior_login", referrer);
    return "user/login";

Then, after successful login custom implementation of SavedRequestAwareAuthenticationSuccessHandler will redirect user to the previous page:

HttpSession session = request.getSession(false);
if (session != null) {
    url = (String) request.getSession().getAttribute("url_prior_login");

Redirect the user:

if (url != null) {

How to set width of a p:column in a p:dataTable in PrimeFaces 3.0?

I don't know what browser you're using, but according to, nth-child and nth-last-child do now work on MSIE 8. I don't know about 9. will give you more info.

Angularjs $http.get().then and binding to a list

Promise returned from $http can not be binded directly (I dont exactly know why). I'm using wrapping service that works perfectly for me:

.factory('DocumentsList', function($http, $q){
    var d = $q.defer();
    return d.promise;

and bind to it in controller:

function Ctrl($scope, DocumentsList) {
    $scope.Documents = DocumentsList;


In Angular 1.2 auto-unwrap promises was removed. See

parent & child with position fixed, parent overflow:hidden bug

2016 update:

You can create a new stacking context, as seen on Coderwall:

<div style="transform: translate3d(0,0,0);overflow:hidden">
   <img style="position:fixed; ..." />

Which refers to

For elements whose layout is governed by the CSS box model, any value other than none for the transform results in the creation of both a stacking context and a containing block. The object acts as a containing block for fixed positioned descendants.

How do you get total amount of RAM the computer has?

Compatible with .Net and Mono (tested with Win10/FreeBSD/CentOS)

Using ComputerInfo source code and PerformanceCounters for Mono and as backup for .Net:

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Security;

public class SystemMemoryInfo
    private readonly PerformanceCounter _monoAvailableMemoryCounter;
    private readonly PerformanceCounter _monoTotalMemoryCounter;
    private readonly PerformanceCounter _netAvailableMemoryCounter;

    private ulong _availablePhysicalMemory;
    private ulong _totalPhysicalMemory;

    public SystemMemoryInfo()
            if (PerformanceCounterCategory.Exists("Mono Memory"))
                _monoAvailableMemoryCounter = new PerformanceCounter("Mono Memory", "Available Physical Memory");
                _monoTotalMemoryCounter = new PerformanceCounter("Mono Memory", "Total Physical Memory");
            else if (PerformanceCounterCategory.Exists("Memory"))
                _netAvailableMemoryCounter = new PerformanceCounter("Memory", "Available Bytes");
            // ignored

    public ulong AvailablePhysicalMemory

            return _availablePhysicalMemory;

    public ulong TotalPhysicalMemory

            return _totalPhysicalMemory;

    [DllImport("Kernel32", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern void GlobalMemoryStatus(ref MEMORYSTATUS lpBuffer);

    [DllImport("Kernel32", CharSet = CharSet.Auto, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool GlobalMemoryStatusEx(ref MEMORYSTATUSEX lpBuffer);

    private void Refresh()
            if (_monoTotalMemoryCounter != null && _monoAvailableMemoryCounter != null)
                _totalPhysicalMemory = (ulong) _monoTotalMemoryCounter.NextValue();
                _availablePhysicalMemory = (ulong) _monoAvailableMemoryCounter.NextValue();
            else if (Environment.OSVersion.Version.Major < 5)
                var memoryStatus = MEMORYSTATUS.Init();
                GlobalMemoryStatus(ref memoryStatus);

                if (memoryStatus.dwTotalPhys > 0)
                    _availablePhysicalMemory = memoryStatus.dwAvailPhys;
                    _totalPhysicalMemory = memoryStatus.dwTotalPhys;
                else if (_netAvailableMemoryCounter != null)
                    _availablePhysicalMemory = (ulong) _netAvailableMemoryCounter.NextValue();
                var memoryStatusEx = MEMORYSTATUSEX.Init();

                if (GlobalMemoryStatusEx(ref memoryStatusEx))
                    _availablePhysicalMemory = memoryStatusEx.ullAvailPhys;
                    _totalPhysicalMemory = memoryStatusEx.ullTotalPhys;
                else if (_netAvailableMemoryCounter != null)
                    _availablePhysicalMemory = (ulong) _netAvailableMemoryCounter.NextValue();
            // ignored

    private struct MEMORYSTATUS
        private uint dwLength;
        internal uint dwMemoryLoad;
        internal uint dwTotalPhys;
        internal uint dwAvailPhys;
        internal uint dwTotalPageFile;
        internal uint dwAvailPageFile;
        internal uint dwTotalVirtual;
        internal uint dwAvailVirtual;

        public static MEMORYSTATUS Init()
            return new MEMORYSTATUS
                dwLength = checked((uint) Marshal.SizeOf(typeof(MEMORYSTATUS)))

    private struct MEMORYSTATUSEX
        private uint dwLength;
        internal uint dwMemoryLoad;
        internal ulong ullTotalPhys;
        internal ulong ullAvailPhys;
        internal ulong ullTotalPageFile;
        internal ulong ullAvailPageFile;
        internal ulong ullTotalVirtual;
        internal ulong ullAvailVirtual;
        internal ulong ullAvailExtendedVirtual;

        public static MEMORYSTATUSEX Init()
            return new MEMORYSTATUSEX
                dwLength = checked((uint) Marshal.SizeOf(typeof(MEMORYSTATUSEX)))

How to return part of string before a certain character?

In General a function to return string after substring is

function getStringAfterSubstring(parentString, substring) {_x000D_
    return parentString.substring(parentString.indexOf(substring) + substring.length)_x000D_
function getStringBeforeSubstring(parentString, substring) {_x000D_
    return parentString.substring(0, parentString.indexOf(substring))_x000D_
console.log(getStringAfterSubstring('abcxyz123uvw', '123'))_x000D_
console.log(getStringBeforeSubstring('abcxyz123uvw', '123'))

What is the "-->" operator in C/C++?

This code first compares x and 0 and then decrements x. (Also said in the first answer: You're post-decrementing x and then comparing x and 0 with the > operator.) See the output of this code:

9 8 7 6 5 4 3 2 1 0

We now first compare and then decrement by seeing 0 in the output.

If we want to first decrement and then compare, use this code:

#include <stdio.h>
int main(void)
    int x = 10;

    while( --x> 0 ) // x goes to 0
        printf("%d ", x);
    return 0;

That output is:

9 8 7 6 5 4 3 2 1

Add Text on Image using PIL

With Pillow, you can also draw on an image using the ImageDraw module. You can draw lines, points, ellipses, rectangles, arcs, bitmaps, chords, pieslices, polygons, shapes and text.

from PIL import Image, ImageDraw
blank_image ='RGBA', (400, 300), 'white')
img_draw = ImageDraw.Draw(blank_image)
img_draw.rectangle((70, 50, 270, 200), outline='red', fill='blue')
img_draw.text((70, 250), 'Hello World', fill='green')'drawn_image.jpg')

we create an Image object with the new() method. This returns an Image object with no loaded image. We then add a rectangle and some text to the image before saving it.

How to send a JSON object over Request with Android?

Sending a json object from Android is easy if you use Apache HTTP Client. Here's a code sample on how to do it. You should create a new thread for network activities so as not to lock up the UI thread.

    protected void sendJson(final String email, final String pwd) {
        Thread t = new Thread() {

            public void run() {
                Looper.prepare(); //For Preparing Message Pool for the child Thread
                HttpClient client = new DefaultHttpClient();
                HttpConnectionParams.setConnectionTimeout(client.getParams(), 10000); //Timeout Limit
                HttpResponse response;
                JSONObject json = new JSONObject();

                try {
                    HttpPost post = new HttpPost(URL);
                    json.put("email", email);
                    json.put("password", pwd);
                    StringEntity se = new StringEntity( json.toString());  
                    se.setContentType(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
                    response = client.execute(post);

                    /*Checking response */
                        InputStream in = response.getEntity().getContent(); //Get the data in the entity

                } catch(Exception e) {
                    createDialog("Error", "Cannot Estabilish Connection");

                Looper.loop(); //Loop in the message queue


You could also use Google Gson to send and retrieve JSON.

How to get the string size in bytes?

If you use sizeof()then a char *str and char str[] will return different answers. char str[] will return the length of the string(including the string terminator) while char *str will return the size of the pointer(differs as per compiler).

Configuring Git over SSH to login once

If you have cloned using HTTPS (recommended) then:-

git config --global credential.helper cache

and then

git config --global credential.helper 'cache --timeout=2592000'
  • timeout=2592000 (30 Days in seconds) to enable caching for 30 days (or whatever suites you).

  • Now run a simple git command that requires your username and password.

  • Enter your credentials once and now caching is enabled for 30 Days.

  • Try again with any git command and now you don't need any credentials.

  • For more info :- Caching your GitHub password in Git

Note : You need Git 1.7.10 or newer to use the credential helper. On system restart, we might have to enter the password again.

Update #1:

If you are receiving this error git: 'credential-cache' is not a git command. See 'get --help'

then replace git config --global credential.helper 'cache --timeout=2592000'

with git config --global credential.helper 'store --file ~/.my-credentials'

Update #2:

If you keep getting the prompt of username and password and getting this issue:

Logon failed, use ctrl+c to cancel basic credential prompt.

Reinstalling the latest version of git worked for me.

TensorFlow not found using pip

Nothing here worked for me on Windows 10. Perhaps an updated solution below that did work for me.

python -m pip install --upgrade tensorflow.

This is using Python 3.6 and tensorflow 1.5 on Windows 10

Spacing between elements

You do not need to create an element like the < br > tag, or any other spacer tag. What you should do is apply a style to the element that needs spacing around it.

Let's say the element you want to have space around is a DIV tag called "myelement".

<div class="myelement">
    I am content that needs spacing around it!

This is the style you would need to use.

 .myelement {
  margin: 20px;  // See below for explanation of this

This is the style you can use to better understand CSS for beginners

.myelement {

Also, avoid using the height: CSS property until you know what you are doing. You will run into some issues when using height that are harder to troubleshoot as a beginner.

How to make circular background using css?

You can use the :before and :after pseudo-classes to put a multi-layered background on a element.

#divID : before {
    background: url(someImage);

#div : after {
    background : url(someotherImage) -10% no-repeat;

Using Python's list index() method on a list of tuples or objects?

Inspired by this question, I found this quite elegant:

>>> tuple_list = [("pineapple", 5), ("cherry", 7), ("kumquat", 3), ("plum", 11)]
>>> next(i for i, t in enumerate(tuple_list) if t[1] == 7)
>>> next(i for i, t in enumerate(tuple_list) if t[0] == "kumquat")

Convert HTML5 into standalone Android App

You can use It is the same phonegap but in very convinient wrapper

How to trust a apt repository : Debian apt-get update error public key is not available: NO_PUBKEY <id>

I had the same problem of "gpg: keyserver timed out" with a couple of different servers. Finally, it turned out that I didn't need to do that manually at all. On a Debian system, the simple solution which fixed it was just (as root or precede with sudo):

aptitude install debian-archive-keyring

In case it is some other keyring you need, check out

apt-cache search keyring | grep debian

My squeeze system shows all these:

debian-archive-keyring       - GnuPG archive keys of the Debian archive
debian-edu-archive-keyring   - GnuPG archive keys of the Debian Edu archive
debian-keyring               - GnuPG keys of Debian Developers
debian-ports-archive-keyring - GnuPG archive keys of the debian-ports archive
emdebian-archive-keyring     - GnuPG archive keys for the emdebian repository

Instagram API: How to get all user media?

You can user pagination of Instagram PHP API:

Something like that:

    $Instagram = new MetzWeb\Instagram\Instagram(array(
        "apiKey"      => IG_APP_KEY,
        "apiSecret"   => IG_APP_SECRET,
        "apiCallback" => IG_APP_CALLBACK

    $pictures = $Instagram->getUserMedia(123);
    do {

        foreach ($pictures->data as $picture_data):

            echo '<img src="'.$picture_data->images->low_resolution->url.'">';


    } while ($pictures = $instagram->pagination($pictures));

"Field has incomplete type" error

You are using a forward declaration for the type MainWindowClass. That's fine, but it also means that you can only declare a pointer or reference to that type. Otherwise the compiler has no idea how to allocate the parent object as it doesn't know the size of the forward declared type (or if it actually has a parameterless constructor, etc.)

So, you either want:

// forward declaration, details unknown
class A;

class B {
  A *a;  // pointer to A, ok

Or, if you can't use a pointer or reference....

// declaration of A
#include "A.h"

class B {
  A a;  // ok, declaration of A is known

At some point, the compiler needs to know the details of A.

If you are only storing a pointer to A then it doesn't need those details when you declare B. It needs them at some point (whenever you actually dereference the pointer to A), which will likely be in the implementation file, where you will need to include the header which contains the declaration of the class A.

// B.h
// header file

// forward declaration, details unknown
class A;

class B {
    void foo();
  A *a;  // pointer to A, ok

// B.cpp
// implementation file

#include "B.h"
#include "A.h"  // declaration of A

B::foo() {
    // here we need to know the declaration of A

Convert wchar_t to char

In general, no. int(wchar_t(255)) == int(char(255)) of course, but that just means they have the same int value. They may not represent the same characters.

You would see such a discrepancy in the majority of Windows PCs, even. For instance, on Windows Code page 1250, char(0xFF) is the same character as wchar_t(0x02D9) (dot above), not wchar_t(0x00FF) (small y with diaeresis).

Note that it does not even hold for the ASCII range, as C++ doesn't even require ASCII. On IBM systems in particular you may see that 'A' != 65

What is a singleton in C#?

I use it for lookup data. Load once from DB.

public sealed class APILookup
        private static readonly APILookup _instance = new APILookup();
        private Dictionary<string, int> _lookup;

        private APILookup()
                _lookup = Utility.GetLookup();
            catch { }

        static APILookup()

        public static APILookup Instance
                return _instance;
        public Dictionary<string, int> GetLookup()
            return _lookup;


How do I run a docker instance from a DockerFile?

Download the file and from the same directory run docker build -t nodebb .

This will give you an image on your local machine that's named nodebb that you can launch an container from with docker run -d nodebb (you can change nodebb to your own name).

How to solve error "Missing `secret_key_base` for 'production' environment" (Rails 4.1)

Demi Magus answer worked for me until Rails 5.

On Apache2/Passenger/Ruby (2.4)/Rails (5.1.6), I had to put


from Demi Magus answer in /etc/apache2/envvars, cause /etc/profile seems to be ignored.


Is there an "exists" function for jQuery?

With jQuery you do not need >0, this is all you need:

if ($(selector).length)

With vanilla JS, you can do the same with:


If you want to turn it into a function that returns bool:

const exists = selector => !!document.querySelector(selector);

  // some code

Bash Templating: How to build configuration files from templates with Bash?

Perfect case for shtpl. (project of mine, so it is not widely in use and lacks in documentation. But here is the solution it offers anyhow. May you want to test it.)

Just execute:

$ i=1 word=dog sh -c "$( shtpl template.txt )"

Result is:

the number is 1
the word is dog

Have fun.

List of installed gems?

This lists all the gems I have installed.

gem query --local

See 2.7 Listing all installed gems

How to schedule a stored procedure in MySQL

If you're open to out-of-the-DB solution: You could set up a cron job that runs a script that will itself call the procedure.

When is a CDATA section necessary within a script tag?

A CDATA section is required if you need your document to parse as XML (e.g. when an XHTML page is interpreted as XML) and you want to be able to write literal i<10 and a && b instead of i&lt;10 and a &amp;&amp; b, as XHTML will parse the JavaScript code as parsed character data as opposed to character data by default. This is not an issue with scripts that are stored in external source files, but for any inline JavaScript in XHTML you will probably want to use a CDATA section.

Note that many XHTML pages were never intended to be parsed as XML in which case this will not be an issue.

For a good writeup on the subject, see

python requests get cookies

Alternatively, you can use requests.Session and observe cookies before and after a request:

>>> import requests
>>> session = requests.Session()
>>> print(session.cookies.get_dict())
>>> response = session.get('')
>>> print(session.cookies.get_dict())
{'PREF': 'ID=5514c728c9215a9a:FF=0:TM=1406958091:LM=1406958091:S=KfAG0U9jYhrB0XNf', 'NID': '67=TVMYiq2wLMNvJi5SiaONeIQVNqxSc2RAwVrCnuYgTQYAHIZAGESHHPL0xsyM9EMpluLDQgaj3db_V37NjvshV-eoQdA8u43M8UwHMqZdL-S2gjho8j0-Fe1XuH5wYr9v'}

What does it mean to "program to an interface"?

So, just to get this right, the advantage of a interface is that I can separate the calling of a method from any particular class. Instead creating a instance of the interface, where the implementation is given from whichever class I choose that implements that interface. Thus allowing me to have many classes, which have similar but slightly different functionality and in some cases (the cases related to the intention of the interface) not care which object it is.

For example, I could have a movement interface. A method which makes something 'move' and any object (Person, Car, Cat) that implements the movement interface could be passed in and told to move. Without the method every knowing the type of class it is.

Better way to Format Currency Input editText?

If your json currency field is of number type (and not String) it may come as 3.1 , 3.15 or just 3. Because json automatically round number fields.

In this case you may need to round it for proper display (and to be able to use a mask on a input field later):

    NumberFormat nf = NumberFormat.getCurrencyInstance();

    float value = 200 // it can be 200, 200.3 or 200.37, BigDecimal will take care
    BigDecimal valueAsBD = BigDecimal.valueOf(value);
    valueAsBD.setScale(2, BigDecimal.ROUND_HALF_UP);

    String formated = nf.format(valueAsBD);

Why this is needed?

All answers point to removing currency simbols when typing judcing you are receiving the cents and so formating dolar + cents / 100 = dolar,cents. But if your json currency field is an number type (and not an String) it will round your cents, it may be 3 , 3.1 or 3.15.

how to concatenate two dictionaries to create a new one in Python?

  1. Slowest and doesn't work in Python3: concatenate the items and call dict on the resulting list:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = dict(d1.items() + d2.items() + d3.items())'
    100000 loops, best of 3: 4.93 usec per loop
  2. Fastest: exploit the dict constructor to the hilt, then one update:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = dict(d1, **d2); d4.update(d3)'
    1000000 loops, best of 3: 1.88 usec per loop
  3. Middling: a loop of update calls on an initially-empty dict:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = {}' 'for d in (d1, d2, d3): d4.update(d)'
    100000 loops, best of 3: 2.67 usec per loop
  4. Or, equivalently, one copy-ctor and two updates:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = dict(d1)' 'for d in (d2, d3): d4.update(d)'
    100000 loops, best of 3: 2.65 usec per loop

I recommend approach (2), and I particularly recommend avoiding (1) (which also takes up O(N) extra auxiliary memory for the concatenated list of items temporary data structure).

HTML5 File API read as text and binary

Note in 2018: readAsBinaryString is outdated. For use cases where previously you'd have used it, these days you'd use readAsArrayBuffer (or in some cases, readAsDataURL) instead.

readAsBinaryString says that the data must be represented as a binary string, where:

...every byte is represented by an integer in the range [0..255].

JavaScript originally didn't have a "binary" type (until ECMAScript 5's WebGL support of Typed Array* (details below) -- it has been superseded by ECMAScript 2015's ArrayBuffer) and so they went with a String with the guarantee that no character stored in the String would be outside the range 0..255. (They could have gone with an array of Numbers instead, but they didn't; perhaps large Strings are more memory-efficient than large arrays of Numbers, since Numbers are floating-point.)

If you're reading a file that's mostly text in a western script (mostly English, for instance), then that string is going to look a lot like text. If you read a file with Unicode characters in it, you should notice a difference, since JavaScript strings are UTF-16** (details below) and so some characters will have values above 255, whereas a "binary string" according to the File API spec wouldn't have any values above 255 (you'd have two individual "characters" for the two bytes of the Unicode code point).

If you're reading a file that's not text at all (an image, perhaps), you'll probably still get a very similar result between readAsText and readAsBinaryString, but with readAsBinaryString you know that there won't be any attempt to interpret multi-byte sequences as characters. You don't know that if you use readAsText, because readAsText will use an encoding determination to try to figure out what the file's encoding is and then map it to JavaScript's UTF-16 strings.

You can see the effect if you create a file and store it in something other than ASCII or UTF-8. (In Windows you can do this via Notepad; the "Save As" as an encoding drop-down with "Unicode" on it, by which looking at the data they seem to mean UTF-16; I'm sure Mac OS and *nix editors have a similar feature.) Here's a page that dumps the result of reading a file both ways:

<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
<title>Show File Data</title>
<style type='text/css'>
body {
    font-family: sans-serif;
<script type='text/javascript'>

    function loadFile() {
        var input, file, fr;

        if (typeof window.FileReader !== 'function') {
            bodyAppend("p", "The file API isn't supported on this browser yet.");

        input = document.getElementById('fileinput');
        if (!input) {
            bodyAppend("p", "Um, couldn't find the fileinput element.");
        else if (!input.files) {
            bodyAppend("p", "This browser doesn't seem to support the `files` property of file inputs.");
        else if (!input.files[0]) {
            bodyAppend("p", "Please select a file before clicking 'Load'");
        else {
            file = input.files[0];
            fr = new FileReader();
            fr.onload = receivedText;

        function receivedText() {
            showResult(fr, "Text");

            fr = new FileReader();
            fr.onload = receivedBinary;

        function receivedBinary() {
            showResult(fr, "Binary");

    function showResult(fr, label) {
        var markup, result, n, aByte, byteStr;

        markup = [];
        result = fr.result;
        for (n = 0; n < result.length; ++n) {
            aByte = result.charCodeAt(n);
            byteStr = aByte.toString(16);
            if (byteStr.length < 2) {
                byteStr = "0" + byteStr;
        bodyAppend("p", label + " (" + result.length + "):");
        bodyAppend("pre", markup.join(" "));

    function bodyAppend(tagName, innerHTML) {
        var elm;

        elm = document.createElement(tagName);
        elm.innerHTML = innerHTML;

<form action='#' onsubmit="return false;">
<input type='file' id='fileinput'>
<input type='button' id='btnLoad' value='Load' onclick='loadFile();'>

If I use that with a "Testing 1 2 3" file stored in UTF-16, here are the results I get:

Text (13):

54 65 73 74 69 6e 67 20 31 20 32 20 33

Binary (28):

ff fe 54 00 65 00 73 00 74 00 69 00 6e 00 67 00 20 00 31 00 20 00 32 00 20 00 33 00

As you can see, readAsText interpreted the characters and so I got 13 (the length of "Testing 1 2 3"), and readAsBinaryString didn't, and so I got 28 (the two-byte BOM plus two bytes for each character).

* XMLHttpRequest.response with responseType = "arraybuffer" is supported in HTML 5.

** "JavaScript strings are UTF-16" may seem like an odd statement; aren't they just Unicode? No, a JavaScript string is a series of UTF-16 code units; you see surrogate pairs as two individual JavaScript "characters" even though, in fact, the surrogate pair as a whole is just one character. See the link for details.

Padding In bootstrap

There are padding built into various classes.

For example:

A web forms app:

<asp:CheckBox ID="chkShowDeletedServers" runat="server" AutoPostBack="True" Text="Show Deleted" />

this code above would place the Text of "Show Deleted" too close to the checkbox to what I see at nice to look at.

However with bootstrap

<div class="checkbox-inline">
    <asp:CheckBox ID="chkShowDeletedServers" runat="server" AutoPostBack="True" Text="Show Deleted" />

This created the space, if you don't want the text bold, that class=checkbox

Bootstrap is very flexible, so in this case I don't need a hack, but sometimes you need to.

Rename package in Android Studio

  1. Goto your AndroidManifest.xml file.
  2. Place your cursor in the package name like shown below. Don't select it, just place it.

    Enter image description here

  3. Then press Shift + F6 you will get a popup window as shown below select Rename package.

    Enter image description here

  4. Enter your new name and select Refactor. (Note since my cursor is on "something", only something is renamed.)

That's it done. AAPT2 error: check logs for details

Disabling the AAPT2 mght cause issue in further development, In my case the error was generated when I created the app icon.

<vector xmlns:android=""
<path android:fillColor="#26A69A"
<path android:fillColor="#00000000" android:pathData="M79,19L79,89"
      android:strokeColor="#33FFFFFF" android:strokeWidth="0.8"/>

I solve it by removing this line


Angular.js vs Knockout.js vs Backbone.js

It depends on the nature of your application. And, since you did not describe it in great detail, it is an impossible question to answer. I find Backbone to be the easiest, but I work in Angular all day. Performance is more up to the coder than the framework, in my opinion.

Are you doing heavy DOM manipulation? I would use jQuery and Backbone.

Very data driven app? Angular with its nice data binding.

Game programming? None - direct to canvas; maybe a game engine.

What is a "static" function in C?

There are two uses for the keyword static when it comes to functions in C++.

The first is to mark the function as having internal linkage so it cannot be referenced in other translation units. This usage is deprecated in C++. Unnamed namespaces are preferred for this usage.

// inside some .cpp file:

static void foo();    // old "C" way of having internal linkage

// C++ way:
   void this_function_has_internal_linkage()
      // ...

The second usage is in the context of a class. If a class has a static member function, that means the function is a member of the class (and has the usual access to other members), but it doesn't need to be invoked through a particular object. In other words, inside that function, there is no "this" pointer.

Creating a JSON dynamically with each input value using jquery

Like this:

function createJSON() {
    jsonObj = [];
    $("input[class=email]").each(function() {

        var id = $(this).attr("title");
        var email = $(this).val();

        item = {}
        item ["title"] = id;
        item ["email"] = email;




You are looking for an array of objects. So, you create a blank array. Create an object for each input by using 'title' and 'email' as keys. Then you add each of the objects to the array.

If you need a string, then do

jsonString = JSON.stringify(jsonObj);

Sample Output


How to sum a list of integers with java streams?

May this help those who have objects on the list.

If you have a list of objects and wanted to sum specific fields of this object use the below.

List<ResultSom> somList = MyUtil.getResultSom();
BigDecimal result=
                                             BigDecimal.ZERO, BigDecimal::add);

Relative instead of Absolute paths in Excel VBA

i think this may help. Below Macro checks if folder exists, if does not then create the folder and save in both xls and pdf formats in such folder. It happens that the folder is shared with the involved people so everybody is updated.

Sub PDF_laudo_e_Prod_SP_Sem_Ajuste_Preco()
' PDF_laudo_e_Prod_SP_Sem_Ajuste_Preco Macro


Dim MyFolder As String
Dim LaudoName As String
Dim NF1Name As String
Dim OrigFolder As String

MyFolder = ThisWorkbook.path & "\" & Sheets("Laudo").Range("C9")
LaudoName = Sheets("Laudo").Range("K27")
NF1Name = Sheets("PROD SP sem ajuste").Range("Q3")
OrigFolder = ThisWorkbook.path

Selection.EntireColumn.Hidden = True

If Dir(MyFolder, vbDirectory) <> "" Then
Sheets("Laudo").ExportAsFixedFormat Type:=xlTypePDF, filename:=MyFolder & "\" & LaudoName & ".pdf", Quality:=xlQualityMinimum, _
IncludeDocProperties:=True, IgnorePrintAreas:=False, OpenAfterPublish:= _

Sheets("PROD SP sem ajuste").ExportAsFixedFormat Type:=xlTypePDF, filename:=MyFolder & "\" & NF1Name & ".pdf", Quality:=xlQualityMinimum, _
IncludeDocProperties:=True, IgnorePrintAreas:=False, OpenAfterPublish:= _

ThisWorkbook.SaveAs filename:=MyFolder & "\" & LaudoName

Application.DisplayAlerts = False

ThisWorkbook.SaveAs filename:=OrigFolder & "\" & "Entregas e Instrucao Barter 2015 - beta"

Application.DisplayAlerts = True

MkDir MyFolder
Sheets("Laudo").ExportAsFixedFormat Type:=xlTypePDF, filename:=MyFolder & "\" & LaudoName & ".pdf", Quality:=xlQualityMinimum, _
IncludeDocProperties:=True, IgnorePrintAreas:=False, OpenAfterPublish:= _

Sheets("PROD SP sem ajuste").ExportAsFixedFormat Type:=xlTypePDF, filename:=MyFolder & "\" & NF1Name & ".pdf", Quality:=xlQualityMinimum, _
IncludeDocProperties:=True, IgnorePrintAreas:=False, OpenAfterPublish:= _

ThisWorkbook.SaveAs filename:=MyFolder & "\" & LaudoName

Application.DisplayAlerts = False

ThisWorkbook.SaveAs filename:=OrigFolder & "\" & "Entregas e Instrucao Barter 2015 - beta"

Application.DisplayAlerts = True

End If

Selection.EntireColumn.Hidden = False

End Sub

gpg failed to sign the data fatal: failed to write commit object [Git 2.10.0]

I've seen similar answers, but nothing exactly like what worked for me. On Linux, I had to kill and restart my gpg-agent with:

$ pkill gpg-agent
$ gpg-agent --daemon
$ git commit ...

This did the trick for me. It looks like you do need to have user.signingkey set to your private key as well from what some other comments are saying.

$ git config --global user.signingkey [your_key_hash]

How do I combine the first character of a cell with another cell in Excel?

Personally I like the & function for this

Assuming that you are using cells A1 and A2 for John Smith

=left(a1,1) & b1

If you want to add text between, for example a period

=left(a1,1) & "." & b1

How to make a Generic Type Cast function

While probably not as clean looking as the IConvertible approach, you could always use the straightforward checking typeof(T) to return a T:

public static T ReturnType<T>(string stringValue)
    if (typeof(T) == typeof(int))
        return (T)(object)1;
    else if (typeof(T) == typeof(FooBar))
        return (T)(object)new FooBar(stringValue);
        return default(T);

public class FooBar
    public FooBar(string something)

Finding the direction of scrolling in a UIScrollView?

Swift 5

More clean solution with enum for vertical scrolling.

enum ScrollDirection {
    case up, down

var scrollDirection: ScrollDirection? {
    if scrollView.panGestureRecognizer.translation(in: scrollView.superview).y > 0 {
        return .up
    } else if scrollView.panGestureRecognizer.translation(in: scrollView.superview).y < 0 {
        return .down
    } else {
        return nil


switch scrollDirection {
case .up:   print("up")
case .down: print("down")
default:    print("no scroll")

Why can't I inherit static classes?

Static classes and class members are used to create data and functions that can be accessed without creating an instance of the class. Static class members can be used to separate data and behavior that is independent of any object identity: the data and functions do not change regardless of what happens to the object. Static classes can be used when there is no data or behavior in the class that depends on object identity.

A class can be declared static, which indicates that it contains only static members. It is not possible to use the new keyword to create instances of a static class. Static classes are loaded automatically by the .NET Framework common language runtime (CLR) when the program or namespace that contains the class is loaded.

Use a static class to contain methods that are not associated with a particular object. For example, it is a common requirement to create a set of methods that do not act on instance data and are not associated to a specific object in your code. You could use a static class to hold those methods.

Following are the main features of a static class:

  1. They only contain static members.

  2. They cannot be instantiated.

  3. They are sealed.

  4. They cannot contain Instance Constructors (C# Programming Guide).

Creating a static class is therefore basically the same as creating a class that contains only static members and a private constructor. A private constructor prevents the class from being instantiated.

The advantage of using a static class is that the compiler can check to make sure that no instance members are accidentally added. The compiler will guarantee that instances of this class cannot be created.

Static classes are sealed and therefore cannot be inherited. They cannot inherit from any class except Object. Static classes cannot contain an instance constructor; however, they can have a static constructor. For more information, see Static Constructors (C# Programming Guide).

Java: How to convert String[] to List or Set

Collections.addAll provides the shortest (one-line) receipt


String[] array = {"foo", "bar", "baz"}; 
Set<String> set = new HashSet<>();

You can do as below

Collections.addAll(set, array); 

batch/bat to copy folder and content at once

if you have xcopy, you can use the /E param, which will copy directories and subdirectories and the files within them, including maintaining the directory structure for empty directories

xcopy [source] [destination] /E

How to go back to previous page if back button is pressed in WebView?

If someone wants to handle backPressed for a webView inside a fragment, then he can use below code.

  1. Copy below code into your Activity class (that contains a fragment YourFragmmentName)

    public void onBackPressed() {
    List<Fragment> fragmentList = getSupportFragmentManager().getFragments();
    boolean handled = false;
    for(Object f: fragmentList) {
        if(f instanceof YourFragmentName) {
            handled = ((YourFragmentName)f).onBackPressed();
            if(handled) {
    if(!handled) {


  2. Copy this code in the fragment YourFragmentName

    public boolean onBackPressed() {
       if (webView.canGoBack()) {
           return true;
       } else {
           return false;


  • Activity should be replaced with the actual Acitivity class you are using.
  • YourFragmentName should be replaced with the name of your Fragment.
  • Declare webView in YourFragmentName so that it can be accessed from within the function.

Can I concatenate multiple MySQL rows into one field?

Try this:

DECLARE @Hobbies NVARCHAR(200) = ' '

SELECT @Hobbies = @Hobbies + hobbies + ',' FROM peoples_hobbies WHERE person_id = 5;


set @sql='';
set @result='';
set @separator=' union \r\n';
@sql:=concat('select ''',INFORMATION_SCHEMA.COLUMNS.COLUMN_NAME  ,''' as col_name,',
' FROM ',
) as sql_piece, if(@result:=if(@result='',@sql,concat(@result,@separator,@sql)),'','') as dummy
select @result;

Checking on a thread / remove from list

mythreads = threading.enumerate()

Enumerate returns a list of all Thread objects still alive.

PHP: trying to create a new line with "\n"

If you want to write plain text, you must ensure the content type is set to Content-Type: text/plain. Example:

header('Content-Type: text/plain');

If you are dealing with HTML, you have two options. One is to inset a new line using <br> (Or <br /> for XHTML). The other is to put the plain text in a <pre> element (In this case "pre" stands for preformatted).

Arrays with different datatypes i.e. strings and integers. (Objectorientend)

Notice the repetition of Book in Booknumber (int), Booktitle (string), Booklanguage (string), Bookprice (int)- it screams for a class type.

class Book {
  int number;
  String title;
  String language;
  int price;

Now you can simply have:

Book[] books = new Books[3];

If you want arrays, you can declare it as object array an insert Integer and String into it:

Object books[3][4]

How to update an object in a List<> in C#

Just to add to CKoenig's response. His answer will work as long as the class you're dealing with is a reference type (like a class). If the custom object were a struct, this is a value type, and the results of .FirstOrDefault will give you a local copy of that, which will mean it won't persist back to the collection, as this example shows:

struct MyStruct
    public int TheValue { get; set; }

Test code:

List<MyStruct> coll = new List<MyStruct> {
                                            new MyStruct {TheValue = 10},
                                            new MyStruct {TheValue = 1},
                                            new MyStruct {TheValue = 145},
var found = coll.FirstOrDefault(c => c.TheValue == 1);
found.TheValue = 12;

foreach (var myStruct in coll)

The output is 10,1,145

Change the struct to a class and the output is 10,12,145


How to remove ASP.Net MVC Default HTTP Headers?

X-Powered-By is a custom header in IIS. Since IIS 7, you can remove it by adding the following to your web.config:

      <remove name="X-Powered-By" />

This header can also be modified to your needs, for more information refer to

Add this to web.config to get rid of the X-AspNet-Version header:

  <httpRuntime enableVersionHeader="false" />

Finally, to remove X-AspNetMvc-Version, edit Global.asax.cs and add the following in the Application_Start event:

protected void Application_Start()
    MvcHandler.DisableMvcResponseHeader = true;

You can also modify headers at runtime via the Application_PreSendRequestHeaders event in Global.asax.cs. This is useful if your header values are dynamic:

protected void Application_PreSendRequestHeaders(object source, EventArgs e)
      Response.Headers.Add("bar", "quux");

Difference between DOMContentLoaded and load events

  • domContentLoaded: marks the point when both the DOM is ready and there are no stylesheets that are blocking JavaScript execution - meaning we can now (potentially) construct the render tree. Many JavaScript frameworks wait for this event before they start executing their own logic. For this reason the browser captures the EventStart and EventEnd timestamps to allow us to track how long this execution took.

  • loadEvent: as a final step in every page load the browser fires an “onload” event which can trigger additional application logic.


What's the difference between 'r+' and 'a+' when open file in python?

One difference is for r+ if the files does not exist, it'll not be created and open fails. But in case of a+ the file will be created if it does not exist.

Java word count program

public class wordCount
public static void main(String ar[]) throws Exception
System.out.println("Simple Java Word Count Program");

    int wordCount = 1,count=1;
 BufferedReader br = new BufferedReader(new FileReader("C:/file.txt"));
            String str2 = "", str1 = "";

            while ((str1 = br.readLine()) != null) {

                    str2 += str1;


    for (int i = 0; i < str2.length(); i++) 
        if (str2.charAt(i) == ' ' && str2.charAt(i+1)!=' ') 


    System.out.println("Word count is = " +(wordCount));


How can I read a text file in Android?

Try this

try {
        reader = new BufferedReader(new InputStreamReader(in,"UTF-8"));
    } catch (UnsupportedEncodingException e1) {
        // TODO Auto-generated catch block
      String line="";
      String s ="";
       line = reader.readLine();
   catch (IOException e) 
      while (line != null) 
       s = s + line;
       s =s+"\n";
           line = reader.readLine();
       catch (IOException e) 

Array Length in Java

Arrays are allocated memory at compile time in java, so they are static, the elements not explicitly set or modified are set with the default values. You could use some code like this, though it is not recommended as it does not count default values, even if you explicitly initialize them that way, it is also likely to cause bugs down the line. As others said, when looking for the actual size, ".length" must be used instead of ".length()".

public int logicalArrayLength(type[] passedArray) {
    int count = 0;
    for (int i = 0; i < passedArray.length; i++) {
        if (passedArray[i] != defaultValue) {
    return count;

PHP combine two associative arrays into one array

I use a wrapper around array_merge to deal with SeanWM's comment about null arrays; I also sometimes want to get rid of duplicates. I'm also generally wanting to merge one array into another, as opposed to creating a new array. This ends up as:

 * Merge two arrays - but if one is blank or not an array, return the other.
 * @param $a array First array, into which the second array will be merged
 * @param $b array Second array, with the data to be merged
 * @param $unique boolean If true, remove duplicate values before returning
function arrayMerge(&$a, $b, $unique = false) {
    if (empty($b)) {
        return;  // No changes to be made to $a
    if (empty($a)) {
        $a = $b;
    $a = array_merge($a, $b);
    if ($unique) {
        $a = array_unique($a);

How to recover corrupted Eclipse workspace?

You should be able to start your workspace after deleting the following file: .metadata.plugins\org.eclipse.e4.workbench\workbench.xmi as shown here :

What's the difference between IFrame and Frame?

iframes are used a lot to include complete pages. When those pages are hosted on another domain you get problems with cross side scripting and stuff. There are ways to fix this.

Frames were used to divide your page into multiple parts (for example, a navigation menu on the left). Using them is no longer recommended.

Eclipse Indigo - Cannot install Android ADT Plugin

I tried installing and got the same error (using the new "marketplace"). I tried the typical Help->install new software... then where it says "Work with:" I entered:

followed all the prompts and everything seems to be working fine now.

What's the reason I can't create generic array types in Java?

Arrays Are Covariant

Arrays are said to be covariant which basically means that, given the subtyping rules of Java, an array of type T[] may contain elements of type T or any subtype of T. For instance

Number[] numbers = new Number[3];
numbers[0] = newInteger(10);
numbers[1] = newDouble(3.14);
numbers[2] = newByte(0);

But not only that, the subtyping rules of Java also state that an array S[] is a subtype of the array T[] if S is a subtype of T, therefore, something like this is also valid:

Integer[] myInts = {1,2,3,4};
Number[] myNumber = myInts;

Because according to the subtyping rules in Java, an array Integer[] is a subtype of an array Number[] because Integer is a subtype of Number.

But this subtyping rule can lead to an interesting question: what would happen if we try to do this?

myNumber[0] = 3.14; //attempt of heap pollution

This last line would compile just fine, but if we run this code, we would get an ArrayStoreException because we’re trying to put a double into an integer array. The fact that we are accessing the array through a Number reference is irrelevant here, what matters is that the array is an array of integers.

This means that we can fool the compiler, but we cannot fool the run-time type system. And this is so because arrays are what we call a reifiable type. This means that at run-time Java knows that this array was actually instantiated as an array of integers which simply happens to be accessed through a reference of type Number[].

So, as we can see, one thing is the actual type of the object, an another thing is the type of the reference that we use to access it, right?

The Problem with Java Generics

Now, the problem with generic types in Java is that the type information for type parameters is discarded by the compiler after the compilation of code is done; therefore this type information is not available at run time. This process is called type erasure. There are good reasons for implementing generics like this in Java, but that’s a long story, and it has to do with binary compatibility with pre-existing code.

The important point here is that since at run-time there is no type information, there is no way to ensure that we are not committing heap pollution.

Let’s consider now the following unsafe code:

List<Integer> myInts = newArrayList<Integer>();
List<Number> myNums = myInts; //compiler error
myNums.add(3.14); //heap polution

If the Java compiler does not stop us from doing this, the run-time type system cannot stop us either, because there is no way, at run time, to determine that this list was supposed to be a list of integers only. The Java run-time would let us put whatever we want into this list, when it should only contain integers, because when it was created, it was declared as a list of integers. That’s why the compiler rejects line number 4 because it is unsafe and if allowed could break the assumptions of the type system.

As such, the designers of Java made sure that we cannot fool the compiler. If we cannot fool the compiler (as we can do with arrays) then we cannot fool the run-time type system either.

As such, we say that generic types are non-reifiable, since at run time we cannot determine the true nature of the generic type.

I skipped some parts of this answers you can read full article here:

How to sort multidimensional array by column?

below solution worked for me in case of required number is float. Solution:

table=sorted(table,key=lambda x: float(x[5]))
for row in table[:]:


How to hide axes and gridlines in Matplotlib (python)

# Hide grid lines

# Hide axes ticks

Note, you need matplotlib>=1.2 for set_zticks() to work.

jQuery: Clearing Form Inputs

Took some searching and reading to find a method that suited my situation, on form submit, run ajax to a remote php script, on success/failure inform user, on complete clear the form.

I had some default values, all other methods involved .val('') thereby not resetting but clearing the form.

I got this too work by adding a reset button to the form, which had an id of myform:

$("#myform > input[type=reset]").trigger('click');

This for me had the correct outcome on resetting the form, oh and dont forget the


to stop the form submitting in browser, like I did :).



env: node: No such file or directory in mac

Let's see, I sorted that on a different way. in my case I had as path something like ~/.local/bin which seems that it is not the way it wants.

Try to use the full path, like /Users/tobias/.local/bin, I mean, change the PATH variable from ~/.local/bin to /Users/tobias/.local/bin or $HOME/.local/bin .

Now it works.

React.js: onChange event for contentEditable

Edit 2015

Someone has made a project on NPM with my solution:

Edit 06/2016: I've just encoutered a new problem that occurs when the browser tries to "reformat" the html you just gave him, leading to component always re-rendering. See

Edit 07/2016: here's my production contentEditable implementation. It has some additional options over react-contenteditable that you might want, including:

  • locking
  • imperative API allowing to embed html fragments
  • ability to reformat the content


FakeRainBrigand's solution has worked quite fine for me for some time until I got new problems. ContentEditables are a pain, and are not really easy to deal with React...

This JSFiddle demonstrates the problem.

As you can see, when you type some characters and click on Clear, the content is not cleared. This is because we try to reset the contenteditable to the last known virtual dom value.

So it seems that:

  • You need shouldComponentUpdate to prevent caret position jumps
  • You can't rely on React's VDOM diffing algorithm if you use shouldComponentUpdate this way.

So you need an extra line so that whenever shouldComponentUpdate returns yes, you are sure the DOM content is actually updated.

So the version here adds a componentDidUpdate and becomes:

var ContentEditable = React.createClass({
    render: function(){
        return <div id="contenteditable"
            dangerouslySetInnerHTML={{__html: this.props.html}}></div>;

    shouldComponentUpdate: function(nextProps){
        return nextProps.html !== this.getDOMNode().innerHTML;

    componentDidUpdate: function() {
        if ( this.props.html !== this.getDOMNode().innerHTML ) {
           this.getDOMNode().innerHTML = this.props.html;

    emitChange: function(){
        var html = this.getDOMNode().innerHTML;
        if (this.props.onChange && html !== this.lastHtml) {
                target: {
                    value: html
        this.lastHtml = html;

The Virtual dom stays outdated, and it may not be the most efficient code, but at least it does work :) My bug is resolved


1) If you put shouldComponentUpdate to avoid caret jumps, then the contenteditable never rerenders (at least on keystrokes)

2) If the component never rerenders on key stroke, then React keeps an outdated virtual dom for this contenteditable.

3) If React keeps an outdated version of the contenteditable in its virtual dom tree, then if you try to reset the contenteditable to the value outdated in the virtual dom, then during the virtual dom diff, React will compute that there are no changes to apply to the DOM!

This happens mostly when:

  • you have an empty contenteditable initially (shouldComponentUpdate=true,prop="",previous vdom=N/A),
  • the user types some text and you prevent renderings (shouldComponentUpdate=false,prop=text,previous vdom="")
  • after user clicks a validation button, you want to empty that field (shouldComponentUpdate=false,prop="",previous vdom="")
  • as both the newly produced and old vdom are "", React does not touch the dom.

Show/Hide Div on Scroll

Try this code


$('window').scrollUp(function(){ $(#div).show() });

Best way to find the months between two dates

Try this:

 dateRange = [datetime.strptime(dateRanges[0], "%Y-%m-%d"),
             datetime.strptime(dateRanges[1], "%Y-%m-%d")]
delta_time = max(dateRange) - min(dateRange)
#Need to use min(dateRange).month to account for different length month
#Note that timedelta returns a number of days
delta_datetime = (datetime(1, min(dateRange).month, 1) + delta_time -
                           timedelta(days=1)) #min y/m/d are 1
months = ((delta_datetime.year - 1) * 12 + delta_datetime.month -
print months

Shouldn't matter what order you input the dates, and it takes into account the difference in month lengths.

How can I install an older version of a package via NuGet?

Another more manual option to get it:

.nuget\nuget.exe install Newtonsoft.Json -Version 4.0.5

Moment.js - two dates difference in number of days

the diff method returns the difference in milliseconds. Instantiating moment(diff) isn't meaningful.

You can define a variable :

var dayInMilliseconds = 1000 * 60 * 60 * 24;

and then use it like so :

diff / dayInMilliseconds // --> 15


actually, this is built into the diff method, dubes' answer is better

Error Domain=NSURLErrorDomain Code=-1005 "The network connection was lost."

what solved the problem for me was to restart simulator ,and reset content and settings.

Create a sample login page using servlet and JSP?

You aren't really using the doGet() method. When you're opening the page, it issues a GET request, not POST.

Try changing doPost() to service() instead... then you're using the same method to handle GET and POST requests.


Javascript button to insert a big black dot (•) into a html textarea

Just access the element and append it to the value.

     onclick="document.getElementById('myTextArea').value += '•'" 
     value="Add •">

See a live demo.

For the sake of keeping things simple, I haven't written unobtrusive JS. For a production system you should.

Also it needs to be a UTF8 character.

Browsers generally submit forms using the encoding they received the page in. Serve your page as UTF-8 if you want UTF-8 data submitted back.

Numpy array dimensions

The shape method requires that a be a Numpy ndarray. But Numpy can also calculate the shape of iterables of pure python objects:


Storage permission error in Marshmallow

Seems user has declined the permission and app tries to write to external disk, causing error.

public void onRequestPermissionsResult(int requestCode,
        String permissions[], int[] grantResults) {
    switch (requestCode) {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! Do the
                // contacts-related task you need to do.

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.

        // other 'case' lines to check for other
        // permissions this app might request


This video will give you a better idea about UX, handling Runtime permissions

Getting distance between two points based on latitude/longitude

There are multiple ways to calculate the distance based on the coordinates i.e latitude and longitude

Install and import

from geopy import distance
from math import sin, cos, sqrt, atan2, radians
from sklearn.neighbors import DistanceMetric
import osrm
import numpy as np

Define coordinates

lat1, lon1, lat2, lon2, R = 20.9467,72.9520, 21.1702, 72.8311, 6373.0
coordinates_from = [lat1, lon1]
coordinates_to = [lat2, lon2]

Using haversine

dlon = radians(lon2) - radians(lon1)
dlat = radians(lat2) - radians(lat1)
a = sin(dlat / 2)**2 + cos(lat1) * cos(lat2) * sin(dlon / 2)**2
c = 2 * atan2(sqrt(a), sqrt(1 - a))
distance_haversine_formula = R * c
print('distance using haversine formula: ', distance_haversine_formula)

Using haversine with sklearn

dist = DistanceMetric.get_metric('haversine')
X = [[radians(lat1), radians(lon1)], [radians(lat2), radians(lon2)]]
distance_sklearn = R * dist.pairwise(X)
print('distance using sklearn: ', np.array(distance_sklearn).item(1))

Using OSRM

osrm_client = osrm.Client(host='')
coordinates_osrm = [[lon1, lat1], [lon2, lat2]] # note that order is lon, lat
osrm_response = osrm_client.route(coordinates=coordinates_osrm, overview=osrm.overview.full)
dist_osrm = osrm_response.get('routes')[0].get('distance')/1000 # in km
print('distance using OSRM: ', dist_osrm)

Using geopy

distance_geopy = distance.distance(coordinates_from, coordinates_to).km
print('distance using geopy: ', distance_geopy)
distance_geopy_great_circle = distance.great_circle(coordinates_from, coordinates_to).km 
print('distance using geopy great circle: ', distance_geopy_great_circle)


distance using haversine formula:  26.07547017310917
distance using sklearn:  27.847882224769783
distance using OSRM:  33.091699999999996
distance using geopy:  27.7528030550408
distance using geopy great circle:  27.839182219511834

Excel how to fill all selected blank cells with text

I don't believe search and replace will do it for you (doesn't work for me in Excel 2010 Home). Are you sure you want to put "null" in EVERY cell in the sheet? That is millions of cells, in which case there is no way a search and replace would be able to handle it memory-wise (correct me if I am wrong).

In the case I am right and you don't want millions of "null" cells, then here is a macro. It asks you to select the range then put "null" inside every cell that was blank.

Sub FillWithNull()

Dim cell As range
Dim myRange As range

Set myRange = Application.InputBox("Select the range", Type:=8)
Application.ScreenUpdating = False

For Each cell In myRange
    If Len(cell) = 0 Then
        cell.Value = "Null"
    End If

Application.ScreenUpdating = True

End Sub

ESRI : Failed to parse source map

Chrome recently added support for source maps in the developer tools. If you go under settings on the chrome developer toolbar you can see the following two options:

Chrome Developer Tools Source Maps

If you disable those two options, and refresh the browser, it should no longer ask for source maps.

These settings can be found here:

Chrome Developer Tools Source Maps

Chart.js - Formatting Y axis

Chart.js 2.X.X

I know this post is old. But if anyone is looking for more flexible solution, here it is

var options = {
        scales: {
            yAxes: [{
                ticks: {
                    beginAtZero: true,
                    callback: function(label, index, labels) {
                        return Intl.NumberFormat().format(label);
                        // 1,350

                        return Intl.NumberFormat('hi', { 
                            style: 'currency', currency: 'INR', minimumFractionDigits: 0, 
                        }).format(label).replace(/^(\D+)/, '$1 ');
                        // ? 1,350

                        // return Intl.NumberFormat('hi', {
                            style: 'currency', currency: 'INR', currencyDisplay: 'symbol', minimumFractionDigits: 2 
                        }).format(label).replace(/^(\D+)/, '$1 ');
                        // ? 1,350.00

'hi' is Hindi. Check here for other locales argument

for more currency symbol

Datatables Select All Checkbox

The solution given by @annoyingmouse works for me.

But to use the checkbox in the header cell, I also had to fix select.dataTables.css.
It seems that they used :

table.dataTable tbody

instead of :

table.dataTable thead

So I had to add this to my css :

table.dataTable thead {
  position: relative;
table.dataTable thead,
table.dataTable thead {
  display: block;
  position: absolute;
  top: 1.2em;
  left: 50%;
  width: 12px;
  height: 12px;
  box-sizing: border-box;
table.dataTable tbody,
table.dataTable thead {
  content: ' ';
  margin-top: -6px;
  margin-left: -6px;
  border: 1px solid black;
  border-radius: 3px;

Read/write to file using jQuery

Use javascript's execCommand('SaveAs', false, filename); functionality

Edit: No longer works. This Javascript function used to work across all browsers, but now only on IE, due to browser security considerations. It presented a "Save As" Dialog to the user who runs this function through their browser, the user presses OK and the file is saved by javascript on the server side.

Now this code is an rare antique zero day collectible.

// content is the data (a string) you'll write to file.
// filename is a string filename to write to on server side.
// This function uses iFrame as a buffer, it fills it up with your content
// and prompts the user to save it out.
function save_content_to_file(content, filename){
    var dlg = false;
           open("text/plain", "replace");
           charset = "utf-8";
           document.charset = "utf-8";
           dlg = execCommand('SaveAs', false, filename);
    return dlg;

Invoke the function like this:

msg =  "I am the president of tautology club.";
save_content_to_file(msg, "C:\\test");

Remove Rows From Data Frame where a Row matches a String

I had a column(A) in a data frame with 3 values in it (yes, no, unknown). I wanted to filter only those rows which had a value "yes" for which this is the code, hope this will help you guys as well --

df <- df [(!(df$A=="no") & !(df$A=="unknown")),]

Font-awesome, input type 'submit'

Also possible like this

<button type="submit" class="icon-search icon-large"></button>

How to change TIMEZONE for a java.util.Calendar/Date

  1. The class Date/Timestamp represents a specific instant in time, with millisecond precision, since January 1, 1970, 00:00:00 GMT. So this time difference (from epoch to current time) will be same in all computers across the world with irrespective of Timezone.

  2. Date/Timestamp doesn't know about the given time is on which timezone.

  3. If we want the time based on timezone we should go for the Calendar or SimpleDateFormat classes in java.

  4. If you try to print a Date/Timestamp object using toString(), it will convert and print the time with the default timezone of your machine.

  5. So we can say (Date/Timestamp).getTime() object will always have UTC (time in milliseconds)

  6. To conclude Date.getTime() will give UTC time, but toString() is on locale specific timezone, not UTC.

Now how will I create/change time on specified timezone?

The below code gives you a date (time in milliseconds) with specified timezones. The only problem here is you have to give date in string format.

   DateFormat dateFormat = new SimpleDateFormat("yyyyMMdd HH:mm:ss");
   java.util.Date parsedDate = dateFormatLocal.parse(date);

Use dateFormat.format for taking input Date (which is always UTC), timezone and return date as String.

How to store UTC/GMT time in DB:

If you print the parsedDate object, the time will be in default timezone. But you can store the UTC time in DB like below.

        Calendar calGMT = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
        Timestamp tsSchedStartTime = new Timestamp (parsedDate.getTime());
        if (tsSchedStartTime != null) {
            stmt.setTimestamp(11, tsSchedStartTime, calGMT );
        } else {
            stmt.setNull(11, java.sql.Types.DATE);

How to show progress bar while loading, using ajax

Here is an example that's working for me with MVC and Javascript in the Razor. The first function calls an action via ajax on my controller and passes two parameters.

        function redirectToAction(var1, var2)

                var url = '../actionnameinsamecontroller/' + routeId;

                    type: "GET",
                    url: url,
                    data: { param1: var1, param2: var2 },
                    dataType: 'html',
                    success: function(){
                    error: function(xhr, ajaxOptions, thrownError){


Use the ajaxStart to start your progress bar code.

                // showing a modal

                var i = 0;
                var timeout = 750;

                (function progressbar()
                    if(i < 1000)
                        // some code to make the progress bar move in a loop with a timeout to 
                        // control the speed of the bar
                        setTimeout(progressbar, timeout);

When the process completes close the progress bar

            // hide the progress bar

Stretch image to fit full container width bootstrap

First of all if the size of the image is smaller than the container, then only "img-fluid" class will not solve your problem. you have to set the width of image to 100%, for that you can use Bootstrap class "w-100". keep in mind that "container-fluid" and "col-12" class sets left and right padding to 15px and "row" class sets left and right margin to "-15px" by default. make sure to set them to 0.

Note: "px-0" is a bootstrap class which sets left and right padding to 0 and
"mx-0" is a bootstrap class which sets left and right margin to 0

P.S. i am using Bootstrap 4.0 version.

 <div class="container-fluid px-0">
        <div class="row mx-0">
            <div class="col-12 px-0">
            <img src="images/top.jpg" class="img-fluid w-100">

Grep for beginning and end of line?

It should be noted that not only will the caret (^) behave differently within the brackets, it will have the opposite result of placing it outside of the brackets. Placing the caret where you have it will search for all strings NOT beginning with the content you placed within the brackets. You also would want to place a period before the asterisk in between your brackets as with grep, it also acts as a "wildcard".

grep ^[.rwx].*[0-9]$

This should work for you, I noticed that some posters used a character class in their expressions which is an effective method as well, but you were not using any in your original expression so I am trying to get one as close to yours as possible explaining every minor change along the way so that it is better understood. How can we learn otherwise?

C++ error: "Array must be initialized with a brace enclosed initializer"

You cannot initialize an array to '0' like that

int cipher[Array_size][Array_size]=0;

You can either initialize all the values in the array as you declare it like this:

// When using different values
int a[3] = {10,20,30};

// When using the same value for all members
int a[3] = {0};

// When using same value for all members in a 2D array
int a[Array_size][Array_size] = { { 0 } };

Or you need to initialize the values after declaration. If you want to initialize all values to 0 for example, you could do something like:

for (int i = 0; i < Array_size; i++ ) {
    a[i] = 0;

How to use std::sort to sort an array in C++

Use the C++ std::sort function:

#include <algorithm>
using namespace std;

int main()
  vector<int> v(2000);
  sort(v.begin(), v.end());

git: Your branch is ahead by X commits

If you get this message after doing a git pull remote branch, try following it up with a git fetch. (Optionally, run git fetch -p to prune deleted branches from the repo)

Fetch seems to update the local representation of the remote branch, which doesn't necessarily happen when you do a git pull remote branch.

How do I measure the execution time of JavaScript code with callbacks?

var start = +new Date();
var counter = 0;
for(var i = 1; i < LIMIT; i++){
    ++counter;{id : i, name : "MongoUser [" + i + "]"}, function(err, saved) {
          if( err || !saved ) console.log("Error");
          else console.log("Saved");
          if (--counter === 0) 
              var end = +new Date();
              console.log("all users saved in " + (end-start) + " milliseconds");

How to convert decimal to hexadecimal in JavaScript

The code below will convert the decimal value d to hexadecimal. It also allows you to add padding to the hexadecimal result. So 0 will become 00 by default.

function decimalToHex(d, padding) {
    var hex = Number(d).toString(16);
    padding = typeof (padding) === "undefined" || padding === null ? padding = 2 : padding;

    while (hex.length < padding) {
        hex = "0" + hex;

    return hex;

jQuery 'if .change() or .keyup()'

You could subscribe for the change and keyup events:

$(function() {

where myFunction is the function you would like executed:

function myFunction() {
    alert( 'something happened!' );

How to correctly save instance state of Fragments in back stack?

This is the way I am using at this moment... it's very complicated but at least it handles all the possible situations. In case anyone is interested.

public final class MyFragment extends Fragment {
    private TextView vstup;
    private Bundle savedState = null;

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.whatever, null);
        vstup = (TextView)v.findViewById(;

        /* (...) */

        /* If the Fragment was destroyed inbetween (screen rotation), we need to recover the savedState first */
        /* However, if it was not, it stays in the instance from the last onDestroyView() and we don't want to overwrite it */
        if(savedInstanceState != null && savedState == null) {
            savedState = savedInstanceState.getBundle(App.STAV);
        if(savedState != null) {
        savedState = null;

        return v;

    public void onDestroyView() {
        savedState = saveState(); /* vstup defined here for sure */
        vstup = null;

    private Bundle saveState() { /* called either from onDestroyView() or onSaveInstanceState() */
        Bundle state = new Bundle();
        state.putCharSequence(App.VSTUP, vstup.getText());
        return state;

    public void onSaveInstanceState(Bundle outState) {
        /* If onDestroyView() is called first, we can use the previously savedState but we can't call saveState() anymore */
        /* If onSaveInstanceState() is called first, we don't have savedState, so we need to call saveState() */
        /* => (?:) operator inevitable! */
        outState.putBundle(App.STAV, (savedState != null) ? savedState : saveState());

    /* (...) */


Alternatively, it is always a possibility to keep the data displayed in passive Views in variables and using the Views only for displaying them, keeping the two things in sync. I don't consider the last part very clean, though.

How to handle floats and decimal separators with html5 input type number

I have not found a perfect solution but the best I could do was to use type="tel" and disable html5 validation (formnovalidate):

<input name="txtTest" type="tel" value="1,200.00" formnovalidate="formnovalidate" />

If the user puts in a comma it will output with the comma in every modern browser i tried (latest FF, IE, edge, opera, chrome, safari desktop, android chrome).

The main problem is:

  • Mobile users will see their phone keyboard which may be different than the number keyboard.
  • Even worse the phone keyboard may not even have a key for a comma.

For my use case I only had to:

  • Display the initial value with a comma (firefox strips it out for type=number)
  • Not fail html5 validation (if there is a comma)
  • Have the field read exactly as input (with a possible comma)

If you have a similar requirement this should work for you.

Note: I did not like the support of the pattern attribute. The formnovalidate seems to work much better.

How can I kill whatever process is using port 8080 so that I can vagrant up?

In case above-accepted answer did not work, try below solution. You can use it for port 8080 or for any other ports.

sudo lsof -i tcp:3000 

Replace 3000 with whichever port you want. Run below command to kill that process.

sudo kill -9 PID

PID is process ID you want to kill.

Below is the output of commands on mac Terminal.

Command output

Reset par to the default values at startup

Every time a new device is opened par() will reset, so another option is simply do and continue.

Get refresh token google api

For those using the Google API Client Library for PHP and seeking offline access and refresh tokens beware as of the time of this writing the docs are showing incorrect examples.

currently it's showing:

$client = new Google_Client();
$client->setRedirectUri('http://' . $_SERVER['HTTP_HOST'] . '/oauth2callback.php');
// offline access will give you both an access and refresh token so that
// your app can refresh the access token without user interaction.
// Using "consent" ensures that your application always receives a refresh token.
// If you are not using offline access, you can omit this.
$client->setIncludeGrantedScopes(true);   // incremental auth


All of this works great - except ONE piece


After a bit of reasoning I changed this line to the following and EVERYTHING WORKED


It makes sense since using the HTTP requests it was changed from approval_prompt=force to prompt=consent. So changing the setter method from setApprovalPrompt to setPrompt follows natural convention - BUT IT'S NOT IN THE DOCS!!! That I found at least.

How can I use Async with ForEach?

This is method I created to handle async scenarios with ForEach.

  • If one of tasks fails then other tasks will continue their execution.
  • You have ability to add function that will be executed on every exception.
  • Exceptions are being collected as aggregateException at the end and are available for you.
  • Can handle CancellationToken
 public static class ParallelExecutor
        /// <summary>
        /// Executes asynchronously given function on all elements of given enumerable with task count restriction.
        /// Executor will continue starting new tasks even if one of the tasks throws. If at least one of the tasks throwed exception then <see cref="AggregateException"/> is throwed at the end of the method run.
        /// </summary>
        /// <typeparam name="T">Type of elements in enumerable</typeparam>
        /// <param name="maxTaskCount">The maximum task count.</param>
        /// <param name="enumerable">The enumerable.</param>
        /// <param name="asyncFunc">asynchronous function that will be executed on every element of the enumerable. MUST be thread safe.</param>
        /// <param name="onException">Acton that will be executed on every exception that would be thrown by asyncFunc. CAN be thread unsafe.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        public static async Task ForEachAsync<T>(int maxTaskCount, IEnumerable<T> enumerable, Func<T, Task> asyncFunc, Action<Exception> onException = null, CancellationToken cancellationToken = default)
            using var semaphore = new SemaphoreSlim(initialCount: maxTaskCount, maxCount: maxTaskCount);

            // This `lockObject` is used only in `catch { }` block.
            object lockObject = new object();
            var exceptions = new List<Exception>();
            var tasks = new Task[enumerable.Count()];
            int i = 0;

                foreach (var t in enumerable)
                    await semaphore.WaitAsync(cancellationToken);
                    tasks[i++] = Task.Run(
                        async () =>
                                await asyncFunc(t);
                            catch (Exception e)
                                if (onException != null)
                                    lock (lockObject)

                                // This exception will be swallowed here but it will be collected at the end of ForEachAsync method in order to generate AggregateException.
                        }, cancellationToken);

                    if (cancellationToken.IsCancellationRequested)
            catch (OperationCanceledException e)

            foreach (var t in tasks)
                if (cancellationToken.IsCancellationRequested)

                // Exception handling in this case is actually pretty fast.
                    await t;
#pragma warning disable CA1031 // Do not catch general exception types - we want to throw that exception later as aggregate exception. Nothing wrong here.
                catch (Exception e)
#pragma warning restore CA1031 // Do not catch general exception types

            if (exceptions.Any())
                throw new AggregateException(exceptions);

What are the retransmission rules for TCP?

What exactly are the rules for requesting retransmission of lost data?

The receiver does not request the retransmission. The sender waits for an ACK for the byte-range sent to the client and when not received, resends the packets, after a particular interval. This is ARQ (Automatic Repeat reQuest). There are several ways in which this is implemented.

Stop-and-wait ARQ
Go-Back-N ARQ
Selective Repeat ARQ

are detailed in the RFC 3366.

At what time frequency are the retransmission requests performed?

The retransmissions-times and the number of attempts isn't enforced by the standard. It is implemented differently by different operating systems, but the methodology is fixed. (One of the ways to fingerprint OSs perhaps?)

The timeouts are measured in terms of the RTT (Round Trip Time) times. But this isn't needed very often due to Fast-retransmit which kicks in when 3 Duplicate ACKs are received.

Is there an upper bound on the number?

Yes there is. After a certain number of retries, the host is considered to be "down" and the sender gives up and tears down the TCP connection.

Is there functionality for the client to indicate to the server to forget about the whole TCP segment for which part went missing when the IP packet went missing?

The whole point is reliable communication. If you wanted the client to forget about some part, you wouldn't be using TCP in the first place. (UDP perhaps?)

Multiple Updates in MySQL

I took the answer from @newtover and extended it using the new json_table function in MySql 8. This allows you to create a stored procedure to handle the workload rather than building your own SQL text in code:

drop table if exists `test`;
create table `test` (
  `Id` int,
  `Number` int,
insert into test (Id, Number) values (1, 1), (2, 2);

DROP procedure IF EXISTS `Test`;
    p_json json
    update test s
        join json_table(p_json, '$[*]' columns(`id` int path '$.id', `number` int path '$.number')) v 
        on set s.Number=v.number;

call `Test`('[{"id": 1, "number": 10}, {"id": 2, "number": 20}]');
select * from test;

drop table if exists `test`;

It's a few ms slower than pure SQL but I'm happy to take the hit rather than generate the sql text in code. Not sure how performant it is with huge recordsets (the JSON object has a max size of 1Gb) but I use it all the time when updating 10k rows at a time.

How to get query string parameter from MVC Razor markup?

If you are using .net core 2.0 this would be:


Sample usage:

<a href="@Url.Action("Query",new {parm1=Context.Request.Query["queryparm1"]})">GO</a>

PHP Notice: Undefined offset: 1 with array when reading data

The output of the error, is because you call an index of the Array that does not exist, for example

$arr = Array(1,2,3);
echo $arr[3]; 
// Error PHP Notice:  Undefined offset: 1 pointer 3 does not exist, the array only has 3 elements but starts at 0 to 2, not 3!

How To Define a JPA Repository Query with a Join

You are experiencing this issue for two reasons.

  • The JPQL Query is not valid.
  • You have not created an association between your entities that the underlying JPQL query can utilize.

When performing a join in JPQL you must ensure that an underlying association between the entities attempting to be joined exists. In your example, you are missing an association between the User and Area entities. In order to create this association we must add an Area field within the User class and establish the appropriate JPA Mapping. I have attached the source for User below. (Please note I moved the mappings to the fields)

public class User {

    private Long idUser;

    private String userName;

    private Area area;

    public Long getIdUser() {
        return idUser;

    public void setIdUser(Long idUser) {
        this.idUser = idUser;

    public String getUserName() {
        return userName;

    public void setUserName(String userName) {
        this.userName = userName;

    public Area getArea() {
        return area;

    public void setArea(Area area) {
        this.area = area;

Once this relationship is established you can reference the area object in your @Query declaration. The query specified in your @Query annotation must follow proper syntax, which means you should omit the on clause. See the following:

@Query("select u.userName from User u inner join u.area ar where ar.idArea = :idArea")

While looking over your question I also made the relationship between the User and Area entities bidirectional. Here is the source for the Area entity to establish the bidirectional relationship.

@Table(name = "area")
public class Area {

    private Long idArea;

    private String areaName;

    @OneToOne(fetch=FetchType.LAZY, mappedBy="area")
    private User user;

    public Long getIdArea() {
        return idArea;

    public void setIdArea(Long idArea) {
        this.idArea = idArea;

    public String getAreaName() {
        return areaName;

    public void setAreaName(String areaName) {
        this.areaName = areaName;

    public User getUser() {
        return user;

    public void setUser(User user) {
        this.user = user;

Uncaught SoapFault exception: [HTTP] Error Fetching http headers

In my apache error log, I saw:

[Tue Feb 16 14:55:02 2010] [notice] child pid 9985 exit signal File size limit exceeded (25)

So I, removed all the contents of my largest log file 2.1GB /var/log/system.log. Now everything works.

Auto-scaling input[type=text] to width of value?

Unfortunately the size attribute will not work very well. There will be extra space and too little space sometimes, depending on how the font is set up. (check out the example)

If you want this to work well, try watching for changes on the input, and resize it then. You probably want to set it to the input's scrollWidth. We would need to account for box sizing, too.

In the following example, I'm setting the size of the input to 1 to prevent it from having a scrollWidth that is greater than our initial width (set manually with CSS).

// (no-jquery document.ready)_x000D_
function onReady(f) {_x000D_
    "complete" === document.readyState_x000D_
        ? f() : setTimeout(onReady, 10, f);_x000D_
onReady(function() {_x000D_
function registerInput(el) {_x000D_
    el.size = 1;_x000D_
    var style = el.currentStyle || window.getComputedStyle(el),_x000D_
        borderBox = style.boxSizing === "border-box",_x000D_
        boxSizing = borderBox_x000D_
            ? parseInt(style.borderRightWidth, 10) +_x000D_
                parseInt(style.borderLeftWidth, 10)_x000D_
            : 0;_x000D_
    if ("onpropertychange" in el) {_x000D_
         // IE_x000D_
         el.onpropertychange = adjust;_x000D_
    } else if ("oninput" in el) {_x000D_
         el.oninput = adjust;_x000D_
    function adjust() {_x000D_
        // reset to smaller size (for if text deleted) _x000D_ = "";_x000D_
        // getting the scrollWidth should trigger a reflow_x000D_
        // and give you what the width would be in px if _x000D_
        // original style, less any box-sizing_x000D_
        var newWidth = el.scrollWidth + boxSizing;_x000D_
        // so let's set this to the new width!_x000D_ = newWidth + "px";_x000D_
* {_x000D_
  font-family: sans-serif;_x000D_
input.autoresize {_x000D_
  width: 125px;_x000D_
  min-width: 125px;_x000D_
  max-width: 400px;_x000D_
input[type='text'] {_x000D_
  box-sizing: border-box;_x000D_
  padding: 4px 8px;_x000D_
  border-radius: 4px;_x000D_
  border: 1px solid #ccc;_x000D_
  margin-bottom: 10px;_x000D_
<label> _x000D_
  <input class="autoresize" placeholder="this will resize" type='text'>_x000D_
  Doesn't resize:_x000D_
<input placeholder="this will not" type='text'>_x000D_
  Has extra space to right:_x000D_
  <input value="123456789" size="9" type="text"/>_x000D_

I think this should work in even IE6, but don't take my word for it.

Depending on your use case, you may need to bind the adjust function to other events. E.g. changing an input's value programmatically, or changing the element's style's display property from none (where scrollWidth === 0) to block or inline-block, etc.

Ignore parent padding

margin: 0 -10px; 

is better than

margin: -10px;

The later sucks content vertically into it.

How to combine paths in Java?

This also works in Java 8 :

Path file = Paths.get("Some path");
file = Paths.get(file + "Some other path");

Error: Generic Array Creation

The following will give you an array of the type you want while preserving type safety.

PCB[] getAll(Class<PCB[]> arrayType) {  
    PCB[] res = arrayType.cast(java.lang.reflect.Array.newInstance(arrayType.getComponentType(), list.size()));  
    for (int i = 0; i < res.length; i++)  {  
        res[i] = list.get(i);  
    return res;  

How this works is explained in depth in my answer to the question that Kirk Woll linked as a duplicate.

Appending an element to the end of a list in Scala

That's because you shouldn't do it (at least with an immutable list). If you really really need to append an element to the end of a data structure and this data structure really really needs to be a list and this list really really has to be immutable then do eiher this:

(4 :: List(1,2,3).reverse).reverse

or that:

List(1,2,3) ::: List(4)

How to pass value from <option><select> to form action

Like @Shoaib answered, you dont need any jQuery or Javascript. You can to this simply with pure html!

<form method="POST" action="index.php?action=contact_agent">
  <select name="agent_id" required>
    <option value="1">Agent Homer</option>
    <option value="2">Agent Lenny</option>
    <option value="3">Agent Carl</option>
  <input type="submit" value="Submit">
  1. Remove &agent_id= from form action since you don't need it there.
  2. Add name="agent_id" to the select
  3. Optionally add word required do indicate that this selection is required.

Since you are using PHP, then by posting the form to index.php you can catch agent_id with $_POST

/** Since you reference action on `form action` then value of $_GET['action'] will be contact_agent */
$action = $_GET['action'];

/** Value of $_POST['agent_id'] will be selected option value */
$agent_id = $_POST['agent_id']; 

As conclusion for such a simple task you should not use any javascript or jQuery. To @FelipeAlvarez that answers your comment

Vertical Text Direction

<!DOCTYPE html>
        h2 {
           margin: 0 0 0 0;
           transform: rotate(270deg);
           transform-origin: top left;
           color: #852c98;
           position: absolute;
           top: 200px;
        <h2>It’s all in the curd</h2>

What is the max size of VARCHAR2 in PL/SQL and SQL?

As per official documentation link shared by Andre Kirpitch, Oracle 10g gives a maximum size of 4000 bytes or characters for varchar2. If you are using a higher version of oracle (for example Oracle 12c), you can get a maximum size upto 32767 bytes or characters for varchar2. To utilize the extended datatype feature of oracle 12, you need to start oracle in upgrade mode. Follow the below steps in command prompt:

1) Login as sysdba (sqlplus / as sysdba)



4) ALTER SYSTEM SET max_string_size=extended;

5) Oracle\product\\rdbms\admin\utl32k.sql



How to make a <div> always full screen?

What I found the best elegant way is like the following, the most trick here is make the div's position: fixed.

.mask {_x000D_
    background-color: rgba(0, 0, 0, 0.5);_x000D_
    position: fixed;_x000D_
    top: 0;_x000D_
    left: 0;_x000D_
    right: 0;_x000D_
    bottom: 0;_x000D_
    margin: 0;_x000D_
    box-sizing: border-box;_x000D_
    width: 100%;_x000D_
    height: 100%;_x000D_
    object-fit: contain;_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <h1>Whatever it takes</h1>_x000D_
    <div class="mask"></div>_x000D_

The mask demo

How to download dependencies in gradle

I have found this answer also very helpful:

gradle dependencies will list the dependencies and download them as a side-effect.

Unix command to find lines common in two files

rm file3.txt

cat file1.out | while read line1
        cat file2.out | while read line2
                if [[ $line1 == $line2 ]]; then
                        echo $line1 >>file3.out

This should do it.

How to serialize an Object into a list of URL query parameters?

If you use jQuery, this is what it uses for parameterizing the options of a GET XHR request:

$.param( obj )

Is there any way to change input type="date" format?

Since the post is active 2 Months ago. so I thought to give my input as well.

In my case i recieve date from a card reader which comes in dd/mm/yyyy format.

what i do. E.g.

var d="16/09/2019" // date received from card_x000D_
function filldate(){_x000D_
<input type="date" id="cardexpirydate">_x000D_
<br /><br />_x000D_
<input type="button" value="fill the date" onclick="filldate();">

what the code do:

  1. it splits the date which i get as dd/mm/yyyy (using split()) on basis of "/" and makes an array,
  2. it then reverse the array (using reverse()) since the date input supports the reverse of what i get.
  3. then it joins (using join())the array to a string according the format required by the input field

All this is done in a single line.

i thought this will help some one so i wrote this.

SQL Server "cannot perform an aggregate function on an expression containing an aggregate or a subquery", but Sybase can

One option is to put the subquery in a LEFT JOIN:

select sum ( t.graduates ) - t1.summedGraduates 
from table as t
    left join 
        select sum ( graduates ) summedGraduates, id
        from table  
        where group_code not in ('total', 'others' )
        group by id 
    ) t1 on =
where t.group_code = 'total'
group by t1.summedGraduates 

Perhaps a better option would be to use SUM with CASE:

select sum(case when group_code = 'total' then graduates end) -
    sum(case when group_code not in ('total','others') then graduates end)
from yourtable

SQL Fiddle Demo with both

CSS: How to have position:absolute div inside a position:relative div not be cropped by an overflow:hidden on a container

There's no magical solution of displaying something outside an overflow hidden container.

A similar effect can be achieved by having an absolute positioned div that matches the size of its parent by positioning it inside your current relative container (the div you don't wish to clip should be outside this div):

#1 .mask {
  width: 100%;
  height: 100%;
  position: absolute;
  z-index: 1;
  overflow: hidden;

Take in mind that if you only have to clip content on the x axis (which appears to be your case, as you only have set the div's width), you can use overflow-x: hidden.

How to remove all white space from the beginning or end of a string?

String.Trim() removes all whitespace from the beginning and end of a string. To remove whitespace inside a string, or normalize whitespace, use a Regular Expression.

How to flush route table in windows?

route -f causes damage. So we need to either disconnect the correct parts of the routing table or find out how to rebuild it.

Can .NET load and parse a properties file equivalent to Java Properties class?

I realize that this isn't exactly what you're asking, but just in case:

When you want to load an actual Java properties file, you'll need to accomodate its encoding. The Java docs indicate that the encoding is ISO 8859-1, which contains some escape sequences that you might not correctly interpret. For instance look at this SO answer to see what's necessary to turn UTF-8 into ISO 8859-1 (and vice versa)

When we needed to do this, we found an open-source PropertyFile.cs and made a few changes to support the escape sequences. This class is a good one for read/write scenarios. You'll need the supporting PropertyFileIterator.cs class as well.

Even if you're not loading true Java properties, make sure that your prop file can express all the characters you need to save (UTF-8 at least)

Twitter Bootstrap: div in container with 100% height

Update 2019

In Bootstrap 4, flexbox can be used to get a full height layout that fills the remaining space.

First of all, the container (parent) needs to be full height:

Option 1_ Add a class for min-height: 100%;. Remember that min-height will only work if the parent has a defined height:

html, body {
  height: 100%;

.min-100 {
    min-height: 100%;

Option 2_ Use vh units:

.vh-100 {
    min-height: 100vh;

Also of Bootstrap 4.1, the vh-100 and min-vh-100 classes are included in Bootstrap so there is no need to for the extra CSS

Then, use flexbox direction column d-flex flex-column on the container, and flex-grow-1 on any child divs (ie: row) that you want to fill the remaining height.

Also see:
Bootstrap 4 Navbar and content fill height flexbox
Bootstrap - Fill fluid container between header and footer
How to make the row stretch remaining height

Creating threads - Task.Factory.StartNew vs new Thread()

The task gives you all the goodness of the task API:

  • Adding continuations (Task.ContinueWith)
  • Waiting for multiple tasks to complete (either all or any)
  • Capturing errors in the task and interrogating them later
  • Capturing cancellation (and allowing you to specify cancellation to start with)
  • Potentially having a return value
  • Using await in C# 5
  • Better control over scheduling (if it's going to be long-running, say so when you create the task so the task scheduler can take that into account)

Note that in both cases you can make your code slightly simpler with method group conversions:

DataInThread = new Thread(ThreadProcedure);
// Or...
Task t = Task.Factory.StartNew(ThreadProcedure);

How do I unlock a SQLite database?

From your previous comments you said a -journal file was present.

This could mean that you have opened and (EXCLUSIVE?) transaction and have not yet committed the data. Did your program or some other process leave the -journal behind??

Restarting the sqlite process will look at the journal file and clean up any uncommitted actions and remove the -journal file.

java build path problems

Here's a good discussion on this:

Basically you should

  1. Download and install the 1.5 JDK. (download link)
  2. In Eclipse, Go to Window ? Preferences ? Java ? Installed JREs.
  3. Add the 1.5 JDK to the list.
  4. Select 1.5 as Compiler Compliance Level.