Programs & Examples On #Httplib2

104, 'Connection reset by peer' socket error, or When does closing a socket result in a RST rather than FIN?

Normally, you'd get an RST if you do a close which doesn't linger (i.e. in which data can be discarded by the stack if it hasn't been sent and ACK'd) and a normal FIN if you allow the close to linger (i.e. the close waits for the data in transit to be ACK'd).

Perhaps all you need to do is set your socket to linger so that you remove the race condition between a non lingering close done on the socket and the ACKs arriving?

How do I determine height and scrolling position of window in jQuery?

From jQuery Docs:

const height = $(window).height();
const scrollTop = $(window).scrollTop();

Get UTC time and local time from NSDate object

My Xcode Version 6.1.1 (6A2008a)

In playground, test like this:

// I'm in East Timezone 8
let x = NSDate() //Output:"Dec 29, 2014, 11:37 AM"
let y = NSDate.init() //Output:"Dec 29, 2014, 11:37 AM"
println(x) //Output:"2014-12-29 03:37:24 +0000"

// seconds since 2001
x.hash //Output:441,517,044
x.hashValue //Output:441,517,044
x.timeIntervalSinceReferenceDate //Output:441,517,044.875367

// seconds since 1970
x.timeIntervalSince1970 //Output:1,419,824,244.87537

Failed to connect to, reason: errno:111 Connection refused

First, Start MongoDB:

sudo service mongod start

Then, Run:


MySQL Error 1215: Cannot add foreign key constraint

Another reason: if you use ON DELETE SET NULL all columns that are used in the foreign key must allow null values. Someone else found this out in this question.

From my understanding it wouldn't be a problem regarding data integrity, but it seems that MySQL just doesn't support this feature (in 5.7).

Find the division remainder of a number

If you want the remainder of your division problem, just use the actual remainder rules, just like in mathematics. Granted this won't give you a decimal output.

valone = 8
valtwo = 3
x = valone / valtwo
r = valone - (valtwo * x)
print "Answer: %s with a remainder of %s" % (x, r)

If you want to make this in a calculator format, just substitute valone = 8 with valone = int(input("Value One")). Do the same with valtwo = 3, but different vairables obviously.

How to get WooCommerce order details



Here is a custom function I have made, to make the things clear for you, related to get the data of an order ID. You will see all the different RAW outputs you can get and how to get the data you need…

Using print_r() function (or var_dump() function too) allow to output the raw data of an object or an array.

So first I output this data to show the object or the array hierarchy. Then I use different syntax depending on the type of that variable (string, array or object) to output the specific data needed.

IMPORTANT: With $order object you can use most of WC_order or WC_Abstract_Order methods (using the object syntax)…

Here is the code:

function get_order_details($order_id){

    // 1) Get the Order object
    $order = wc_get_order( $order_id );

    // OUTPUT
    echo '<h3>RAW OUTPUT OF THE ORDER OBJECT: </h3>';
    echo '<br><br>';
    echo '<h3>THE ORDER OBJECT (Using the object syntax notation):</h3>';
    echo '$order->order_type: ' . $order->order_type . '<br>';
    echo '$order->id: ' . $order->id . '<br>';
    echo '<h4>THE POST OBJECT:</h4>';
    echo '$order->post->ID: ' . $order->post->ID . '<br>';
    echo '$order->post->post_author: ' . $order->post->post_author . '<br>';
    echo '$order->post->post_date: ' . $order->post->post_date . '<br>';
    echo '$order->post->post_date_gmt: ' . $order->post->post_date_gmt . '<br>';
    echo '$order->post->post_content: ' . $order->post->post_content . '<br>';
    echo '$order->post->post_title: ' . $order->post->post_title . '<br>';
    echo '$order->post->post_excerpt: ' . $order->post->post_excerpt . '<br>';
    echo '$order->post->post_status: ' . $order->post->post_status . '<br>';
    echo '$order->post->comment_status: ' . $order->post->comment_status . '<br>';
    echo '$order->post->ping_status: ' . $order->post->ping_status . '<br>';
    echo '$order->post->post_password: ' . $order->post->post_password . '<br>';
    echo '$order->post->post_name: ' . $order->post->post_name . '<br>';
    echo '$order->post->to_ping: ' . $order->post->to_ping . '<br>';
    echo '$order->post->pinged: ' . $order->post->pinged . '<br>';
    echo '$order->post->post_modified: ' . $order->post->post_modified . '<br>';
    echo '$order->post->post_modified_gtm: ' . $order->post->post_modified_gtm . '<br>';
    echo '$order->post->post_content_filtered: ' . $order->post->post_content_filtered . '<br>';
    echo '$order->post->post_parent: ' . $order->post->post_parent . '<br>';
    echo '$order->post->guid: ' . $order->post->guid . '<br>';
    echo '$order->post->menu_order: ' . $order->post->menu_order . '<br>';
    echo '$order->post->post_type: ' . $order->post->post_type . '<br>';
    echo '$order->post->post_mime_type: ' . $order->post->post_mime_type . '<br>';
    echo '$order->post->comment_count: ' . $order->post->comment_count . '<br>';
    echo '$order->post->filter: ' . $order->post->filter . '<br>';
    echo '<h4>THE ORDER OBJECT (again):</h4>';
    echo '$order->order_date: ' . $order->order_date . '<br>';
    echo '$order->modified_date: ' . $order->modified_date . '<br>';
    echo '$order->customer_message: ' . $order->customer_message . '<br>';
    echo '$order->customer_note: ' . $order->customer_note . '<br>';
    echo '$order->post_status: ' . $order->post_status . '<br>';
    echo '$order->prices_include_tax: ' . $order->prices_include_tax . '<br>';
    echo '$order->tax_display_cart: ' . $order->tax_display_cart . '<br>';
    echo '$order->display_totals_ex_tax: ' . $order->display_totals_ex_tax . '<br>';
    echo '$order->display_cart_ex_tax: ' . $order->display_cart_ex_tax . '<br>';
    echo '$order->formatted_billing_address->protected: ' . $order->formatted_billing_address->protected . '<br>';
    echo '$order->formatted_shipping_address->protected: ' . $order->formatted_shipping_address->protected . '<br><br>';
    echo '- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - <br><br>';

    // 2) Get the Order meta data
    $order_meta = get_post_meta($order_id);

    echo '<h3>RAW OUTPUT OF THE ORDER META DATA (ARRAY): </h3>';
    echo '<br><br>';
    echo '<h3>THE ORDER META DATA (Using the array syntax notation):</h3>';
    echo '$order_meta[_order_key][0]: ' . $order_meta[_order_key][0] . '<br>';
    echo '$order_meta[_order_currency][0]: ' . $order_meta[_order_currency][0] . '<br>';
    echo '$order_meta[_prices_include_tax][0]: ' . $order_meta[_prices_include_tax][0] . '<br>';
    echo '$order_meta[_customer_user][0]: ' . $order_meta[_customer_user][0] . '<br>';
    echo '$order_meta[_billing_first_name][0]: ' . $order_meta[_billing_first_name][0] . '<br><br>';
    echo 'And so on ……… <br><br>';
    echo '- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - <br><br>';

    // 3) Get the order items
    $items = $order->get_items();


    foreach ( $items as $item_id => $item_data ) {

        echo '<h4>RAW OUTPUT OF THE ORDER ITEM NUMBER: '. $item_id .'): </h4>';
        echo '<br><br>';
        echo 'Item ID: ' . $item_id. '<br>';
        echo '$item_data["product_id"] <i>(product ID)</i>: ' . $item_data['product_id'] . '<br>';
        echo '$item_data["name"] <i>(product Name)</i>: ' . $item_data['name'] . '<br>';

        // Using get_item_meta() method
        echo 'Item quantity <i>(product quantity)</i>: ' . $order->get_item_meta($item_id, '_qty', true) . '<br><br>';
        echo 'Item line total <i>(product quantity)</i>: ' . $order->get_item_meta($item_id, '_line_total', true) . '<br><br>';
        echo 'And so on ……… <br><br>';
        echo '- - - - - - - - - - - - - <br><br>';
    echo '- - - - - - E N D - - - - - <br><br>';

Code goes in function.php file of your active child theme (or theme) or also in any plugin file.

Usage (if your order ID is 159 for example):


This code is tested and works.

Updated code on November 21, 2016

jQuery UI Dialog - missing close icon

A wise man once helped me.

In the folder where jquery-ui.css is located, create a folder named "images" and copy the below files into it:







and the close icon appears.

C Programming: How to read the whole file contents into a buffer

Here is what I would recommend.

It should conform to C89, and be completely portable. In particular, it works also on pipes and sockets on POSIXy systems.

The idea is that we read the input in large-ish chunks (READALL_CHUNK), dynamically reallocating the buffer as we need it. We only use realloc(), fread(), ferror(), and free():

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

/* Size of each input chunk to be
   read and allocate for. */
#define  READALL_CHUNK  262144

#define  READALL_OK          0  /* Success */
#define  READALL_INVALID    -1  /* Invalid parameters */
#define  READALL_ERROR      -2  /* Stream error */
#define  READALL_TOOMUCH    -3  /* Too much input */
#define  READALL_NOMEM      -4  /* Out of memory */

/* This function returns one of the READALL_ constants above.
   If the return value is zero == READALL_OK, then:
     (*dataptr) points to a dynamically allocated buffer, with
     (*sizeptr) chars read from the file.
     The buffer is allocated for one extra char, which is NUL,
     and automatically appended after the data.
   Initial values of (*dataptr) and (*sizeptr) are ignored.
int readall(FILE *in, char **dataptr, size_t *sizeptr)
    char  *data = NULL, *temp;
    size_t size = 0;
    size_t used = 0;
    size_t n;

    /* None of the parameters can be NULL. */
    if (in == NULL || dataptr == NULL || sizeptr == NULL)
        return READALL_INVALID;

    /* A read error already occurred? */
    if (ferror(in))
        return READALL_ERROR;

    while (1) {

        if (used + READALL_CHUNK + 1 > size) {
            size = used + READALL_CHUNK + 1;

            /* Overflow check. Some ANSI C compilers
               may optimize this away, though. */
            if (size <= used) {
                return READALL_TOOMUCH;

            temp = realloc(data, size);
            if (temp == NULL) {
                return READALL_NOMEM;
            data = temp;

        n = fread(data + used, 1, READALL_CHUNK, in);
        if (n == 0)

        used += n;

    if (ferror(in)) {
        return READALL_ERROR;

    temp = realloc(data, used + 1);
    if (temp == NULL) {
        return READALL_NOMEM;
    data = temp;
    data[used] = '\0';

    *dataptr = data;
    *sizeptr = used;

    return READALL_OK;

Above, I've used a constant chunk size, READALL_CHUNK == 262144 (256*1024). This means that in the worst case, up to 262145 chars are wasted (allocated but not used), but only temporarily. At the end, the function reallocates the buffer to the optimal size. Also, this means that we do four reallocations per megabyte of data read.

The 262144-byte default in the code above is a conservative value; it works well for even old minilaptops and Raspberry Pis and most embedded devices with at least a few megabytes of RAM available for the process. Yet, it is not so small that it slows down the operation (due to many read calls, and many buffer reallocations) on most systems.

For desktop machines at this time (2017), I recommend a much larger READALL_CHUNK, perhaps #define READALL_CHUNK 2097152 (2 MiB).

Because the definition of READALL_CHUNK is guarded (i.e., it is defined only if it is at that point in the code still undefined), you can override the default value at compile time, by using (in most C compilers) -DREADALL_CHUNK=2097152 command-line option -- but do check your compiler options for defining a preprocessor macro using command-line options.

Java synchronized block vs. Collections.synchronizedMap

The way you have synchronized is correct. But there is a catch

  1. Synchronized wrapper provided by Collection framework ensures that the method calls I.e add/get/contains will run mutually exclusive.

However in real world you would generally query the map before putting in the value. Hence you would need to do two operations and hence a synchronized block is needed. So the way you have used it is correct. However.

  1. You could have used a concurrent implementation of Map available in Collection framework. 'ConcurrentHashMap' benefit is

a. It has a API 'putIfAbsent' which would do the same stuff but in a more efficient manner.

b. Its Efficient: dThe CocurrentMap just locks keys hence its not blocking the whole map's world. Where as you have blocked keys as well as values.

c. You could have passed the reference of your map object somewhere else in your codebase where you/other dev in your tean may end up using it incorrectly. I.e he may just all add() or get() without locking on the map's object. Hence his call won't run mutually exclusive to your sync block. But using a concurrent implementation gives you a peace of mind that it can never be used/implemented incorrectly.

Android TextView padding between lines

You can use TextView.setLineSpacing(n,m) function.

Calling a method inside another method in same class

Recursion is a method that call itself. In this case it is a recursion. However it will be overloading until you put a restriction inside the method to stop the loop (if-condition).

yum error "Cannot retrieve metalink for repository: epel. Please verify its path and try again" updating ContextBroker

Another possible cause is that your architecture is not supported. I ran into this because I was provided with a CentOS VM, wanted to install EPEL and couldn't for the life of me get it done.

Turns out the VM was CentOS 7 i386, which is an architecture that is apparently no longer supported by EPEL. I guess the only remedy in this case is to reinstall.

.autocomplete is not a function Error

Sounds like autocomplete is being called before the library that defines it is actually loaded - if that makes sense?

If your script is inline, rather than referenced, move it to the bottom of the page. Or (my preferred option) place the script in an external .js file and then reference it:

<script src=""></script>
<script src=""></script>
<script src="yourNewJSFile"></script>

Edit: if you externalise your script, ensure it is referenced AFTER any JQuery libraries it relies on :)

How to check if variable's type matches Type stored in a variable

In order to check if an object is compatible with a given type variable, instead of writing

u is t

you should write


Accessing a resource via codebehind in WPF

I got the resources on C# (Desktop WPF W/ .NET Framework 4.8) using the code below


SQLiteDatabase.query method


  • null for all columns as in SELECT * FROM ...
  • new String[] { "column1", "column2", ... } for specific columns as in SELECT column1, column2 FROM ... - you can also put complex expressions here:
    new String[] { "(SELECT max(column1) FROM table1) AS max" } would give you a column named max holding the max value of column1


  • the part you put after WHERE without that keyword, e.g. "column1 > 5"
  • should include ? for things that are dynamic, e.g. "column1=?" -> see whereArgs


  • specify the content that fills each ? in whereClause in the order they appear

the others

  • just like whereClause the statement after the keyword or null if you don't use it.


String[] tableColumns = new String[] {
    "(SELECT max(column1) FROM table2) AS max"
String whereClause = "column1 = ? OR column1 = ?";
String[] whereArgs = new String[] {
String orderBy = "column1";
Cursor c = sqLiteDatabase.query("table1", tableColumns, whereClause, whereArgs,
        null, null, orderBy);

// since we have a named column we can do
int idx = c.getColumnIndex("max");

is equivalent to the following raw query

String queryString =
    "SELECT column1, (SELECT max(column1) FROM table1) AS max FROM table1 " +
    "WHERE column1 = ? OR column1 = ? ORDER BY column1";
sqLiteDatabase.rawQuery(queryString, whereArgs);

By using the Where/Bind -Args version you get automatically escaped values and you don't have to worry if input-data contains '.

Unsafe: String whereClause = "column1='" + value + "'";
Safe: String whereClause = "column1=?";

because if value contains a ' your statement either breaks and you get exceptions or does unintended things, for example value = "XYZ'; DROP TABLE table1;--" might even drop your table since the statement would become two statements and a comment:

SELECT * FROM table1 where column1='XYZ'; DROP TABLE table1;--'

using the args version XYZ'; DROP TABLE table1;-- would be escaped to 'XYZ''; DROP TABLE table1;--' and would only be treated as a value. Even if the ' is not intended to do bad things it is still quite common that people have it in their names or use it in texts, filenames, passwords etc. So always use the args version. (It is okay to build int and other primitives directly into whereClause though)

Uri content://media/external/file doesn't exist for some devices

Most probably it has to do with caching on the device. Catching the exception and ignoring is not nice but my problem was fixed and it seems to work.

is vs typeof

Does it matter which is faster, if they don't do the same thing? Comparing the performance of statements with different meaning seems like a bad idea.

is tells you if the object implements ClassA anywhere in its type heirarchy. GetType() tells you about the most-derived type.

Not the same thing.

Hexadecimal string to byte array in C

Here's my version:

/* Convert a hex char digit to its integer value. */
int hexDigitToInt(char digit) {
    digit = tolower(digit);
    if ('0' <= digit && digit <= '9') //if it's decimal
        return (int)(digit - '0');
    else if ('a' <= digit && digit <= 'f') //if it's abcdef
        return (int)(digit - ('a' - 10));
        return -1; //value not in [0-9][a-f] range

/* Decode a hex string. */
char *decodeHexString(const char *hexStr) {
    char* decoded = malloc(strlen(hexStr)/2+1);
    char* hexStrPtr = (char *)hexStr;
    char* decodedPtr = decoded;

    while (*hexStrPtr != '\0') { /* Step through hexStr, two chars at a time. */
        *decodedPtr = 16 * hexDigitToInt(*hexStrPtr) + hexDigitToInt(*(hexStrPtr+1));
        hexStrPtr += 2;

    *decodedPtr = '\0'; /* final null char */
    return decoded;

How to Resize image in Swift?

UIImage Extension Swift 5

extension UIImage {
    func resize(_ width: CGFloat, _ height:CGFloat) -> UIImage? {
        let widthRatio  = width / size.width
        let heightRatio = height / size.height
        let ratio = widthRatio > heightRatio ? heightRatio : widthRatio
        let newSize = CGSize(width: size.width * ratio, height: size.height * ratio)
        let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)
        UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
        self.draw(in: rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        return newImage

Use : UIImage().resize(200, 300)

Passing enum or object through an intent (the best solution)

It may be possible to make your Enum implement Serializable then you can pass it via the Intent, as there is a method for passing it as a serializable. The advice to use int instead of enum is bogus. Enums are used to make your code easier to read and easier to maintain. It would a large step backwards into the dark ages to not be able to use Enums.

comparing elements of the same array in java

Try this or purpose will solve with lesser no of steps

for (int i = 0; i < a.length; i++) 
    for (int k = i+1; k < a.length; k++) 
        if (a[i] != a[k]) 
            System.out.println(a[i]+"not the same with"+a[k]+"\n");

How to use mongoose findOne

You might want to consider using console.log with the built-in "arguments" object:

console.log(arguments); // would have shown you [0] null, [1] yourResult

This will always output all of your arguments, no matter how many arguments you have.

Delaying a jquery script until everything else has loaded

Multiple $(document).ready() will fire in order top down on the page. The last $(document).ready() will fire last on the page. Inside the last $(document).ready(), you can trigger a new custom event to fire after all the others..

Wrap your code in an event handler for the new custom event.

    $(document).on("my-event-afterLastDocumentReady", function () {
        // Fires LAST
    $(document).ready(function() {
        // Fires FIRST
    $(document).ready(function() {
        // Fires SECOND
    $(document).ready(function() {
        // Fires THIRD
... other code, scripts, etc....

    $(document).ready(function() {
        // Fires FOURTH
        // This event will fire after all the other $(document).ready() functions have completed.
        // Usefull when your script is at the top of the page, but you need it run last

Get the time difference between two datetimes

Typescript: following should work,

export const getTimeBetweenDates = ({
}: {
  until: number;
  format: 'seconds' | 'minutes' | 'hours' | 'days';
}): number => {
  const date = new Date();
  const remainingTime = new Date(until * 1000);
  const getFrom = moment([date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate()]);
  const getUntil = moment([remainingTime.getUTCFullYear(), remainingTime.getUTCMonth(), remainingTime.getUTCDate()]);
  const diff = getUntil.diff(getFrom, format);
  return !isNaN(diff) ? diff : null;

How to prevent Google Colab from disconnecting?

Try this to avoid all the annoying dialog boxes appearing while you work when trying to simulate the click on the toolbar connect button every minute. you can just copy paste this to your console, call the method and you can work on your notebook.

function connectRefresher() {
       window.ConnectButtonIntervalId = setInterval(function ConnectButton(){
                document.querySelector("#top-toolbar > colab-connect-button").shadowRoot.querySelector("#connect").click();
                document.querySelector("colab-sessions-dialog").shadowRoot.querySelector("#footer > div > paper-button").click();
                console.log("closed the dialog!!"); 
function clearRefresher() { 
           console.log("clear Interval called !!");

 connectRefresher(); //to connect the refresher
 clearRefresher(); //to disconnect the refresher

Different color for each bar in a bar chart; ChartJS

You can call this function which generates random colors for each bars

var randomColorGenerator = function () { 
    return '#' + (Math.random().toString(16) + '0000000').slice(2, 8); 

var barChartData = {
        labels: ["001", "002", "003", "004", "005", "006", "007"],
        datasets: [
                label: "My First dataset",
                fillColor: randomColorGenerator(), 
                strokeColor: randomColorGenerator(), 
                highlightFill: randomColorGenerator(),
                highlightStroke: randomColorGenerator(),
                data: [20, 59, 80, 81, 56, 55, 40]

What's the difference between "Layers" and "Tiers"?

Yes my dear friends said correctly. Layer is a logical partition of application whereas tier is physical partition of system tier partition is depends on layer partition. Just like an application execute on single machine but it follows 3 layered architecture, so we can say that layer architecture could be exist in a tier architecture. In simple term 3 layer architecture can implement in single machine then we can say that its is 1 tier architecture. If we implement each layer on separate machine then its called 3 tier architecture. A layer may also able to run several tier. In layer architecture related component to communicate to each other easily.
Just like we follow given below architecture

  1. presentation layer
  2. business logic layer
  3. data access layer

A client could interact to "presentation layer", but they access public component of below layer's (like business logic layer's public component) to "business logic layer" due to security reason.
Q * why we use layer architecture ? because if we implement layer architecture then we increase our applications efficiency like




other need like after developing application we need to change dbms or modify business logic etc. then it is necessary to all.

Q * why we use tier architecture?

because physically implementation of each layer gives a better efficiency ,without layer architecture we can not implement tier architecture. separate machine to implement separate tier and separate tier is implement one or more layer that's why we use it.
it uses for the purposes of fault tolerance. ==>easy to maintain.

Simple example

Just like a bank open in a chamber, in which categories the employee:

  1. gate keeper
  2. a person for cash
  3. a person who is responsible to introduce banking scheme
  4. manager

they all are the related components of system.

If we going to bank for loan purpose then first a gate keeper open the door with smile after that we goes to near a person that introduce to all scheme of loan after that we goes to manager cabin and pass the loan. After that finally we goes to cashier's counter take loan. These are layer architecture of bank.

What about tier? A bank's branch open in a town, after that in another town, after that in another but what is the basic requirement of each branch

  1. gate keeper
  2. a person for cash
  3. a person who is responsible to introduce banking scheme
  4. manager

exactly the same concept of layer and tier.

How to decrypt hash stored by bcrypt


What's the difference?

The difference is that hashing is a one way function, where encryption is a two-way function.

So, how do you ascertain that the password is right?

Therefore, when a user submits a password, you don't decrypt your stored hash, instead you perform the same bcrypt operation on the user input and compare the hashes. If they're identical, you accept the authentication.

Should you hash or encrypt passwords?

What you're doing now -- hashing the passwords -- is correct. If you were to simply encrypt passwords, a breach of security of your application could allow a malicious user to trivially learn all user passwords. If you hash (or better, salt and hash) passwords, the user needs to crack passwords (which is computationally expensive on bcrypt) to gain that knowledge.

As your users probably use their passwords in more than one place, this will help to protect them.

How to convert a Drawable to a Bitmap?

So after looking (and using) of the other answers, seems they all handling ColorDrawable and PaintDrawable badly. (Especially on lollipop) seemed that Shaders were tweaked so solid blocks of colors were not handled correctly.

I am using the following code now:

public static Bitmap drawableToBitmap(Drawable drawable) {
    if (drawable instanceof BitmapDrawable) {
        return ((BitmapDrawable) drawable).getBitmap();

    // We ask for the bounds if they have been set as they would be most
    // correct, then we check we are  > 0
    final int width = !drawable.getBounds().isEmpty() ?
            drawable.getBounds().width() : drawable.getIntrinsicWidth();

    final int height = !drawable.getBounds().isEmpty() ?
            drawable.getBounds().height() : drawable.getIntrinsicHeight();

    // Now we check we are > 0
    final Bitmap bitmap = Bitmap.createBitmap(width <= 0 ? 1 : width, height <= 0 ? 1 : height,
    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());

    return bitmap;

Unlike the others, if you call setBounds on the Drawable before asking to turn it into a bitmap, it will draw the bitmap at the correct size!

Disable all table constraints in Oracle

This can be scripted in PL/SQL pretty simply based on the DBA/ALL/USER_CONSTRAINTS system view, but various details make not as trivial as it sounds. You have to be careful about the order in which it is done and you also have to take account of the presence of unique indexes.

The order is important because you cannot drop a unique or primary key that is referenced by a foreign key, and there could be foreign keys on tables in other schemas that reference primary keys in your own, so unless you have ALTER ANY TABLE privilege then you cannot drop those PKs and UKs. Also you cannot switch a unique index to being a non-unique index so you have to drop it in order to drop the constraint (for this reason it's almost always better to implement unique constraints as a "real" constraint that is supported by a non-unique index).

How can I submit a form using JavaScript?

document.forms["name of your form"].submit();


document.getElementById("form id").submit();

You can try any of this...this will definitely work...

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

Whilst this isn't strictly an answer to this question I think it's useful.

Arrays and Collections can bother be converted to Iterable which can avoid the need for performing a hard conversion.

For instance I wrote this to join lists/arrays of stuff into a string with a seperator

public static <T> String join(Iterable<T> collection, String delimiter) {
    Iterator<T> iterator = collection.iterator();
    if (!iterator.hasNext())
        return "";

    StringBuilder builder = new StringBuilder();

    T thisVal =;
    builder.append(thisVal == null? "": thisVal.toString());

    while (iterator.hasNext()) {
        thisVal =;
        builder.append(thisVal == null? "": thisVal.toString());

    return builder.toString();

Using iterable means you can either feed in an ArrayList or similar aswell as using it with a String... parameter without having to convert either.

How to SELECT based on value of another SELECT

You can calculate the total (and from that the desired percentage) by using a subquery in the FROM clause:

       SUM(Value) AS "SUM(VALUE)",
       SUM(Value) / AS "% of Total"
FROM   table1,
           SELECT Name,
                  SUM(Value) AS total
           FROM   table1
           GROUP BY Name
       ) AS totals
WHERE  table1.Name = totals.Name
AND    Year BETWEEN 2000 AND 2001

Note that the subquery does not have the WHERE clause filtering the years.

How to set the font style to bold, italic and underlined in an Android TextView?

I don't know about underline, but for bold and italic there is "bolditalic". There is no mention of underline here:

Mind you that to use the mentioned bolditalic you need to, and I quote from that page

Must be one or more (separated by '|') of the following constant values.

so you'd use bold|italic

You could check this question for underline: Can I underline text in an android layout?

SSL cert "err_cert_authority_invalid" on mobile chrome only

I solved my problem with this commands:

cat __mydomain_com.crt > __mydomain_com_combine.crt

and after:

cat __mydomain_com_combine.crt COMODORSADomainValidationSecureServerCA.crt 
COMODORSAAddTrustCA.crt AddTrustExternalCARoot.crt > mydomain.pem

And in my domain nginx .conf I put on the server 443:

ssl_certificate          ssl/mydomain.pem;
ssl_certificate_key      ssl/mydomain.private.key;

I don't forget restart your "Nginx"

service nginx restart

What datatype should be used for storing phone numbers in SQL Server 2005?

Use SSIS to extract and process the information. That way you will have the processing of the XML files separated from SQL Server. You can also do the SSIS transformations on a separate server if needed. Store the phone numbers in a standard format using VARCHAR. NVARCHAR would be unnecessary since we are talking about numbers and maybe a couple of other chars, like '+', ' ', '(', ')' and '-'.

Increment a database field by 1

If you can safely make (firstName, lastName) the PRIMARY KEY or at least put a UNIQUE key on them, then you could do this:

INSERT INTO logins (firstName, lastName, logins) VALUES ('Steve', 'Smith', 1)
ON DUPLICATE KEY UPDATE logins = logins + 1;

If you can't do that, then you'd have to fetch whatever that primary key is first, so I don't think you could achieve what you want in one query.

Disable Logback in SpringBoot

To add an exclusion for logback from Netbeans IDE

  1. Access the >Projects explorer section for your project
  2. Proceed to >Dependencies as displayed below
  3. Trace 'spring-boot-starter-logging-X.X.X.jar'
  4. Right click on the jar and select Exclude Dependency as shown below. This excludes the logback jar on the pom.xml like this;


enter image description here

Embed YouTube video - Refused to display in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'

Along with the embed, I also had to install the Google Cast extension in my browser.

<iframe width="1280" height="720" src="" frameborder="0" allowfullscreen></iframe>

How to add buttons dynamically to my form?

Two problems- List is empty. You need to add some buttons to the list first. Second problem: You can't add buttons to "this". "This" is not referencing what you think, I think. Change this to reference a Panel for instance.

//Assume you have on your .aspx page:
<asp:Panel ID="Panel_Controls" runat="server"></asp:Panel>

private void button1_Click(object sender, EventArgs e)
        List<Button> buttons = new List<Button>();

        for (int i = 0; i < buttons.Capacity; i++)

.htaccess deny from all

You can edit it. The content of the file is literally "Deny from all" which is an Apache directive:

Lightweight workflow engine for Java

The question is what you really want to achieve when you asking for a workflow engine.

The general goal which you would like to achieve by using a workflow engine, is to become more flexible in changing your business logic during runtime. The modelling part is surely one of the most important here. BPMN 2.0 is a de-facto standard in this area and all of the discussed engines support this standard.

The second goal is to control the business process in the way of describing the 'what should happen when...' questions. And this part has a lot to do with the business requirements you are confronted within your project.

Some of the workflow engines (Activity, JBPM) can help you to answer this requirement by 'coding' your processes. This means that you model the 'what should happen when..' paradigm in a way, where you decide which part of your code (e.g a task or an event) should be executed by the workflow engine in various situations. A lot of discussion is going about this concept. And developers naturally ask whether this may not even be implemented by themselves. (It is in fact not so easy as it seems at the first glance)

Some other workflow engines (Imixs-Workflow, Bonita) can help you to answer the 'what should happen when...' requirement in a more user-centric way. This is the area of Human-centric business process management, which supports human skills and activities by a task orientated workflow-engine. The focus is more on the distribution of tasks and processes inside an organisation. The workflow engine helps you to distribute a task to a certain user or user group and to secure, log and monitor a long running business process. Maybe these are the things you do not really want to implement by yourself.

So my advice is, not to mix things that need to be considered separately, because workflow covers a very wide area.

Html encode in PHP

By encode, do you mean: Convert all applicable characters to HTML entities?

htmlspecialchars or htmlentities

You can also use strip_tags if you want to remove all HTML tags :


Note: this will NOT stop all XSS attacks

ORA-01830: date format picture ends before converting entire input string / Select sum where date query

You can try this:

Select To_date ('15/2/2007 00:00:00', 'DD/MM/YYYY HH24:MI:SS'),
       To_date ('28/2/2007 10:12', 'DD/MM/YYYY HH24:MI:SS')
  From DUAL;


Angular ng-class if else

Just make a rule for each case:

<div id="homePage" ng-class="{ 'center': page.isSelected(1) , 'left': !page.isSelected(1)  }">

Or use the ternary operator:

<div id="homePage" ng-class="page.isSelected(1) ? 'center' : 'left'">

KeyListener, keyPressed versus keyTyped

keyPressed - when the key goes down
keyReleased - when the key comes up
keyTyped - when the unicode character represented by this key is sent by the keyboard to system input.

I personally would use keyReleased for this. It will fire only when they lift their finger up.

Note that keyTyped will only work for something that can be printed (I don't know if F5 can or not) and I believe will fire over and over again if the key is held down. This would be useful for something like... moving a character across the screen or something.

Split string into individual words Java

A regex can also be used to split words.

\w can be used to match word characters ([A-Za-z0-9_]), so that punctuation is removed from the results:

String s = "I want to walk my dog, and why not?";
Pattern pattern = Pattern.compile("\\w+");
Matcher matcher = pattern.matcher(s);
while (matcher.find()) {



See Java API documentation for Pattern

SSIS Convert Between Unicode and Non-Unicode Error

Add Data Conversion transformations to convert string columns from non-Unicode (DT_STR) to Unicode (DT_WSTR) strings.

You need to do this for all the string columns...

Java Error: illegal start of expression

public static int [] locations={1,2,3};

public static test dot=new test();

Declare the above variables above the main method and the code compiles fine.

public static void main(String[] args){

Hide Text with CSS, Best Practice?

you can simply make it transparent

   width: 20px;
   height: 20px;
   overflow: hidden; 

select2 changing items dynamically

In my project I use following code:

$('#attribute').bind('change', function(){
    var $options = $();
    for (var i in data) {
        $options = $options.add(
            $('<option>').attr('value', data[i].id).html(data[i].text)

Try to comment out the select2 part. The rest of the code will still work.

Remove local git tags that are no longer on the remote repository

All versions of Git since v1.7.8 understand git fetch with a refspec, whereas since v1.9.0 the --tags option overrides the --prune option. For a general purpose solution, try this:

$ git --version
git version 2.1.3

$ git fetch --prune origin "+refs/tags/*:refs/tags/*"
From ssh://xxx
 x [deleted]         (none)     -> rel_test

For further reading on how the "--tags" with "--prune" behavior changed in Git v1.9.0, see:

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

It's really easy to specify your own decimal separator. Just took me about 2 hours to figure it out :D. You see that you were using the current ou other culture that you specify right? Well, the only thing the parser needs is an IFormatProvider. If you give it the CultureInfo.CurrentCulture.NumberFormat as a formatter, it will format the double according to your current culture's NumberDecimalSeparator. What I did was just to create a new instance of the NumberFormatInfo class and set it's NumberDecimalSeparator property to whichever separator string I wanted. Complete code below:

double value = 2.3d;
NumberFormatInfo nfi = new NumberFormatInfo();
nfi.NumberDecimalSeparator = "-";
string x = value.ToString(nfi);

The result? "2-3"

How to specify the private SSH-key to use when executing shell command on Git?

When you need to connect to github with a normal request (git pull origin master), setting the Host as * in ~/.ssh/config worked for me, any other Host (say, "github" or "gb") wasn't working.

Host *
    User git
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/id_rsa_xxx

List of all users that can connect via SSH

Any user with a valid shell in /etc/passwd can potentially login. If you want to improve security, set up SSH with public-key authentication (there is lots of info on the web on doing this), install a public key in one user's ~/.ssh/authorized_keys file, and disable password-based authentication. This will prevent anybody except that one user from logging in, and will require that the user have in their possession the matching private key. Make sure the private key has a decent passphrase.

To prevent bots from trying to get in, run SSH on a port other than 22 (i.e. 3456). This doesn't improve security but prevents script-kiddies and bots from cluttering up your logs with failed attempts.

What is the best way to merge mp3 files?

As Thomas Owens pointed out, simply concatenating the files will leave multiple ID3 headers scattered throughout the resulting concatenated file - so the time/bitrate info will be wildly wrong.

You're going to need to use a tool which can combine the audio data for you.

mp3wrap would be ideal for this - it's designed to join together MP3 files, without needing to decode + re-encode the data (which would result in a loss of audio quality) and will also deal with the ID3 tags intelligently.

The resulting file can also be split back into its component parts using the mp3splt tool - mp3wrap adds information to the IDv3 comment to allow this.

Live search through table rows

Using yckart's answer, I made it to search for the whole table - all td's.

$("#search").keyup(function() {
    var value = this.value;

    $("table").find("tr").each(function(index) {
        if (index === 0) return;

        var if_td_has = false; //boolean value to track if td had the entered key
        $(this).find('td').each(function () {
            if_td_has = if_td_has || $(this).text().indexOf(value) !== -1; //Check if td's text matches key and then use OR to check it for all td's



How to load a UIView using a nib file created with Interface Builder

Thank you all. I did find a way to do what I wanted.

  1. Create your UIView with the IBOutlets you need.
  2. Create the xib in IB, design it to you liking and link it like this: The File's Owner is of class UIViewController (No custom subclass, but the "real" one). The File Owner's view is connected to the main view and its class is declared as the one from step 1).
  3. Connect your controls with the IBOutlets.
  4. The DynamicViewController can run its logic to decide what view/xib to load. Once its made the decission, in the loadView method put something like this:

    NSArray* nibViews = [[NSBundle mainBundle] loadNibNamed:@"QPickOneView"
    QPickOneView* myView = [ nibViews objectAtIndex: 1];
    myView.question = question;

That's it!

The main bundle's loadNibNamed method will take care of initializing the view and creating the connections.

Now the ViewController can display a view or another depending on the data in memory, and the "parent" screen doesn't need to bother with this logic.

Confirm deletion using Bootstrap 3 modal box

Create modal dialog in HTML with id="confirmation" and use function showConfirmation.

Also remember you should to unbind (modal.unbind()) cancel and success buttons after hide modal dialog. If you do not make this you will get double binding. For example: if you open dialog once and press 'Cancel' and then open dialog in second time and press 'Ok' you will get 2 executions of success callback.

showConfirmation = function(title, message, success, cancel) {
    title = title ? title : 'Are you sure?';
    var modal = $("#confirmation");
        .modal({ backdrop: 'static', keyboard: false })
        .on('', function () {
    if (success) {'click', '.modal-footer .btn-primary', success);
    if (cancel) {'click', '.modal-header .close, .modal-footer .btn-default', cancel);

// bind confirmation dialog on delete buttons
$(document).on("click", ".delete-event, .delete-all-event", function(event){
    var self = $(this);
    var url = $(this).data('url');
    var success = function(){
    var cancel = function(){
    if ('confirmation')) {
        var title ='confirmation-title') ?'confirmation-title') : undefined;
        var message ='confirmation');
        showConfirmation(title, message, success, cancel);
    } else {

display: inline-block extra margin

The divs are treated as inline-elements. Just as a space or line-break between two spans would create a gap, it does between inline-blocks. You could either give them a negative margin or set word-spacing: -1; on the surrounding container.

How to store date/time and timestamps in UTC time zone with JPA and Hibernate

To the best of my knowledge, you need to put your entire Java app in UTC timezone (so that Hibernate will store dates in UTC), and you'll need to convert to whatever timezone desired when you display stuff (at least we do it this way).

At startup, we do:


And set the desired timezone to the DateFormat:


List append() in for loop

The list.append function does not return any value(but None), it just adds the value to the list you are using to call that method.

In the first loop round you will assign None (because the no-return of append) to a, then in the second round it will try to call a.append, as a is None it will raise the Exception you are seeing

You just need to change it to:

for i in range(5):    
# [0, 1, 2, 3, 4]

list.append is what is called a mutating or destructive method, i.e. it will destroy or mutate the previous object into a new one(or a new state).

If you would like to create a new list based in one list without destroying or mutating it you can do something like this:

a=['a', 'b', 'c']
result = a + ['d']

print result
# ['a', 'b', 'c', 'd']

print a
# ['a', 'b', 'c']

As a corollary only, you can mimic the append method by doing the following:

a=['a', 'b', 'c']
a = a + ['d']

print a
# ['a', 'b', 'c', 'd']

Select from multiple tables without a join?

If your question was this -- Select ename, dname FROM emp, dept without using joins..

Then, I would do this...

SELECT ename, (SELECT dname 
FROM dept
WHERE dept.deptno=emp.deptno)dname


---------- --------------

---------- --------------

14 rows selected.

Jquery mouseenter() vs mouseover()

See the example code and demo at the bottom of the jquery documentation page:

... mouseover fires when the pointer moves into the child element as well, while mouseenter fires only when the pointer moves into the bound element.

summing two columns in a pandas dataframe

If "budget" has any NaN values but you don't want it to sum to NaN then try:

def fun (b, a):
    if math.isnan(b):
        return a
        return b + a

f = np.vectorize(fun, otypes=[float])

df['variance'] = f(df['budget'], df_Lp['actual'])

Dealing with multiple Python versions and PIP?

It worked for me in windows this way:

  1. I changed the name of python files and pythonw.exe to

  2. Then I just ran this command in the prompt:

    python3 -m pip install package

How do I get the logfile from an Android device?

Two steps:

  • Generate the log
  • Load Gmail to send the log


  1. Generate the log

    File generateLog() {
        File logFolder = new File(Environment.getExternalStorageDirectory(), "MyFolder");
        if (!logFolder.exists()) {
        String filename = "myapp_log_" + new Date().getTime() + ".log";
        File logFile = new File(logFolder, filename);
        try {
            String[] cmd = new String[] { "logcat", "-f", logFile.getAbsolutePath(), "-v", "time", "ActivityManager:W", "myapp:D" };
            Toaster.shortDebug("Log generated to: " + filename);
            return logFile;
        catch (IOException ioEx) {
        return null;
  2. Load Gmail to send the log

    File logFile = generateLog();
    Intent intent = new Intent(Intent.ACTION_SEND);
    intent.putExtra(Intent.EXTRA_STREAM, Uri.fromFile(logFile));

References for #1


For #2 - there are many different answers out there for how to load the log file to view and send. Finally, the solution here actually worked to both:

  • load Gmail as an option
  • attaches the file successfully

Big thanks to for the correctly working answer

Using AND/OR in if else PHP statement

Yes. The answer is yes.

Two things though:

  • Many programmers prefer && and || instead of and and or, but they work the same (safe for precedence).
  • $status = 'clear' should probably be $status == 'clear'. = is assignment, == is comparison.

how to return index of a sorted list?

You can use the python sorting functions' key parameter to sort the index array instead.

>>> s = [2, 3, 1, 4, 5, 3]
>>> sorted(range(len(s)), key=lambda k: s[k])
[2, 0, 1, 5, 3, 4]

How can I pass a list as a command-line argument with argparse?

I think the most elegant solution is to pass a lambda function to "type", as mentioned by Chepner. In addition to this, if you do not know beforehand what the delimiter of your list will be, you can also pass multiple delimiters to re.split:

# python3 -l "abc xyz, 123"

import re
import argparse

parser = argparse.ArgumentParser(description='Process a list.')
parser.add_argument('-l', '--list',
                    type=lambda s: re.split(' |, ', s),
                    help='comma or space delimited list of characters')

args = parser.parse_args()

# Output: ['abc', 'xyz', '123']

How does Go update third-party packages?

The above answeres have the following problems:

  1. They update everything including your app (in case you have uncommitted changes).
  2. They updated packages you may have already removed from your project but are already on your disk.

To avoid these, do the following:

  1. Delete the 3rd party folders that you want to update.
  2. go to your app folder and run go get -d

PHP CURL Enable Linux

If it's php 7 on ubuntu, try this

apt-get install php7.0-curl
/etc/init.d/apache2 restart

How to insert blank lines in PDF?

And to insert blank line between tables you can use these both methods



Refreshing page on click of a button

<button type="button" onClick="refreshPage()">Close</button>

function refreshPage(){


<button type="button" onClick="window.location.reload();">Close</button>

What does "select 1 from" do?

The statement SELECT 1 FROM SomeTable just returns a column containing the value 1 for each row in your table. If you add another column in, e.g. SELECT 1, cust_name FROM SomeTable then it makes it a little clearer:

----------- ---------------
1           Village Toys
1           Kids Place
1           Fun4All
1           Fun4All
1           The Toy Store

ValueError: max() arg is an empty sequence

When the length of v will be zero, it'll give you the value error.

You should check the length or you should check the list first whether it is none or not.

if list:


len(list)== 0

What is the difference between 'typedef' and 'using' in C++11?

Both keywords are equivalent, but there are a few caveats. One is that declaring a function pointer with using T = int (*)(int, int); is clearer than with typedef int (*T)(int, int);. Second is that template alias form is not possible with typedef. Third is that exposing C API would require typedef in public headers.

LINQ to read XML

Or, if you want a more general approach - i.e. for nesting up to "levelN":

void Main()
    XElement rootElement = XElement.Load(@"c:\events\test.xml");

    Console.WriteLine(GetOutline(0, rootElement));  

private string GetOutline(int indentLevel, XElement element)
    StringBuilder result = new StringBuilder();

    if (element.Attribute("name") != null)
        result = result.AppendLine(new string(' ', indentLevel * 2) + element.Attribute("name").Value);

    foreach (XElement childElement in element.Elements())
        result.Append(GetOutline(indentLevel + 1, childElement));

    return result.ToString();

C# 4.0: Convert pdf to byte[] and vice versa

using (FileStream fs = new FileStream("sample.pdf", FileMode.Open, FileAccess.Read))
                byte[] bytes = new byte[fs.Length];
                int numBytesToRead = (int)fs.Length;
                int numBytesRead = 0;
                while (numBytesToRead > 0)
                    // Read may return anything from 0 to numBytesToRead.
                    int n = fs.Read(bytes, numBytesRead, numBytesToRead);

                    // Break when the end of the file is reached.
                    if (n == 0)

                    numBytesRead += n;
                    numBytesToRead -= n;
                numBytesToRead = bytes.Length;

How to hide a div from code (c#)

Try this. Your markup:

<div id="MyId" runat="server">some content</div>

.. and in aspx.cs file:

protected void Page_Load(object sender, EventArgs e)
    if (Session["someSessionVal"].ToString() == "some value")
        MyId.Visible = true;
        MyId.Visible = false;

Create two threads, one display odd & other even numbers

Concurrent Package:

    import java.util.concurrent.ExecutorService;

    import java.util.concurrent.Executors;
    import java.util.concurrent.Future;
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    //=========== Task1 class prints odd =====
    class TaskClass1 implements Runnable

    private Condition condition;
    private Lock lock;
    boolean exit = false;
    int i;
    TaskClass1(Condition condition,Lock lock)
        this.condition = condition;
        this.lock = lock;
    public void run() {
            for(i = 1;i<11;i++)
                if(i%2 == 0)

                if(i%2 != 0)
                    System.out.println(Thread.currentThread().getName()+" == "+i);



        } catch (Exception e) {
            // TODO Auto-generated catch block


//==== Task2 : prints even =======
class TaskClass2 implements Runnable

    private Condition condition;
    private Lock lock;
    boolean exit = false;
    TaskClass2(Condition condition,Lock lock)
        this.condition = condition;
        this.lock = lock;
    public void run() {
        int i;
        // TODO Auto-generated method stub
            for(i = 2;i<11;i++)


                if(i%2 != 0)
                if(i%2 == 0)
                    System.out.println(Thread.currentThread().getName()+" == "+i);



        } catch (InterruptedException e) {
            // TODO Auto-generated catch block



public class OddEven {

    public static void main(String[] a)
        Lock lock = new ReentrantLock();
        Condition condition = lock.newCondition();
        Future future1;
        Future future2;
        ExecutorService executorService = Executors.newFixedThreadPool(2);

        future1 = executorService.submit(new TaskClass1(condition,lock));
        future2 = executorService.submit(new TaskClass2(condition,lock));



SQL Server : check if variable is Empty or NULL for WHERE clause

Old post but worth a look for someone who stumbles upon like me



It is more efficient to use if-return-return or if-else-return?

This is a question of style (or preference) since the interpreter does not care. Personally I would try not to make the final statement of a function which returns a value at an indent level other than the function base. The else in example 1 obscures, if only slightly, where the end of the function is.

By preference I use:

return A+1 if (A > B) else A-1

As it obeys both the good convention of having a single return statement as the last statement in the function (as already mentioned) and the good functional programming paradigm of avoiding imperative style intermediate results.

For more complex functions I prefer to break the function into multiple sub-functions to avoid premature returns if possible. Otherwise I revert to using an imperative style variable called rval. I try not to use multiple return statements unless the function is trivial or the return statement before the end is as a result of an error. Returning prematurely highlights the fact that you cannot go on. For complex functions that are designed to branch off into multiple subfunctions I try to code them as case statements (driven by a dict for instance).

Some posters have mentioned speed of operation. Speed of Run-time is secondary for me since if you need speed of execution Python is not the best language to use. I use Python as its the efficiency of coding (i.e. writing error free code) that matters to me.

How to put spacing between floating divs?

I found a solution, which at least helps in my situation, it probably is not suitable for other situations:

I give all my green child divs a complete margin:

margin: 10px;

And for the surrounding yellow parent div i set a negative margin:

margin: -10px;

I also had to remove any explicit width or height setting for the yellow parent div, otherwise it did not work.

This way, in absolute terms, the child divs are correctly aligned, although the parent yellow div obviously is set off, which in my case is OK, because it will not be visible.

Why fragments, and when to use fragments instead of activities?

1.Purposes of using a fragment?

  • Ans:
    1. Dealing with device form-factor differences.
    2. Passing information between app screens.
    3. User interface organization.
    4. Advanced UI metaphors.

no target device found android studio 2.1.1

  1. If suppose the android device is not getting connected by android studio then download "PDANet+"(for all android devices).

  2. Or also you can do these following steps:

    • Go to Run tab on toolbar of android studio.
    • Then click on edit configuration
    • In General tab there will "Deployment Target Option" click on "Target" and choose "Open select deployment target dialog" and uncheck the checkbox from below.
    • And at last click OK. Finish.

Git branching: master vs. origin/master vs. remotes/origin/master

I would try to make @ErichBSchulz's answer simpler for beginners:

  • origin/master is the state of master branch on remote repository
  • master is the state of master branch on local repository

Using form input to access camera and immediately upload photos using web app

It's really easy to do this, simply send the file via an XHR request inside of the file input's onchange handler.

<input id="myFileInput" type="file" accept="image/*;capture=camera">

var myInput = document.getElementById('myFileInput');

function sendPic() {
    var file = myInput.files[0];

    // Send file here either by adding it to a `FormData` object 
    // and sending that via XHR, or by simply passing the file into 
    // the `send` method of an XHR instance.

myInput.addEventListener('change', sendPic, false);

Why do we have to normalize the input for an artificial neural network?

Some inputs to NN might not have a 'naturally defined' range of values. For example, the average value might be slowly, but continuously increasing over time (for example a number of records in the database).

In such case feeding this raw value into your network will not work very well. You will teach your network on values from lower part of range, while the actual inputs will be from the higher part of this range (and quite possibly above range, that the network has learned to work with).

You should normalize this value. You could for example tell the network by how much the value has changed since the previous input. This increment usually can be defined with high probability in a specific range, which makes it a good input for network.

Python List vs. Array - when to use?

If you're going to be using arrays, consider the numpy or scipy packages, which give you arrays with a lot more flexibility.

Java integer list

Let's use some java 8 feature:

IntStream.iterate(10, x -> x + 10).limit(5)

If you need to store the numbers you can collect them into a collection eg:

List numbers = IntStream.iterate(10, x -> x + 10).limit(5)

And some delay added:

IntStream.iterate(10, x -> x + 10).limit(5)
  .forEach(x -> {
    try {
    } catch (InterruptedException e) {
      // Do something with the exception

How to instantiate a File object in JavaScript?

Now you can!

var parts = [_x000D_
  new Blob(['you construct a file...'], {type: 'text/plain'}),_x000D_
  ' Same way as you do with blob',_x000D_
  new Uint16Array([33])_x000D_
// Construct a file_x000D_
var file = new File(parts, 'sample.txt', {_x000D_
    lastModified: new Date(0), // optional - default = now_x000D_
    type: "overide/mimetype" // optional - default = ''_x000D_
var fr = new FileReader();_x000D_
fr.onload = function(evt){_x000D_
   document.body.innerHTML = + "<br><a href="+URL.createObjectURL(file)+" download=" + + ">Download " + + "</a><br>type: "+file.type+"<br>last modified: "+ file.lastModifiedDate_x000D_

What are the obj and bin folders (created by Visual Studio) used for?

The obj directory is for intermediate object files and other transient data files that are generated by the compiler or build system during a build. The bin directory is the directory that final output binaries (and any dependencies or other deployable files) will be written to.

You can change the actual directories used for both purposes within the project settings, if you like.

Ruby/Rails: converting a Date to a UNIX timestamp

Solution for Ruby 1.8 when you have an arbitrary DateTime object:

1.8.7-p374 :001 > require 'date'
 => true 
1.8.7-p374 :002 >, 1, 15).strftime('%s')
 => "1326585600"

iPad Safari scrolling causes HTML elements to disappear and reappear with a delay

You need to trick the browser to use hardware acceleration more effectively. You can do this with an empty 3d transform:

-webkit-transform: translate3d(0,0,0)

Particularly, you'll need this on child elements that have a position:relative; declaration (or, just go all out and do it to all child elements).

Not a guaranteed fix, but fairly successful most of the time.

Hat tip:

Get first and last date of current month with JavaScript or jQuery

Very simple, no library required:

var date = new Date();
var firstDay = new Date(date.getFullYear(), date.getMonth(), 1);
var lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);

or you might prefer:

var date = new Date(), y = date.getFullYear(), m = date.getMonth();
var firstDay = new Date(y, m, 1);
var lastDay = new Date(y, m + 1, 0);


Some browsers will treat two digit years as being in the 20th century, so that:

new Date(14, 0, 1);

gives 1 January, 1914. To avoid that, create a Date then set its values using setFullYear:

var date = new Date();
date.setFullYear(14, 0, 1); // 1 January, 14

java.rmi.ConnectException: Connection refused to host:;

you can use LocalRegistry such as:

Registry rgsty = LocateRegistry.createRegistry(1888);
rgsty.rebind("hello", hello);

How can I set NODE_ENV=production on Windows?

Current versions of Windows use Powershell as the default shell, so use:


Per @jsalonen's answer below. If you're in CMD (which is no longer maintained), use

set NODE_ENV=production

This should be executed in the command prompt where you intend to run your Node.js application.

The above line would set the environment variable NODE_ENV for the command prompt where you execute the command.

To set environment variables globally so they persist beyond just the single command prompt, you can find the tool from System in Control Panel (or by typing 'environment' into the search box in the start menu).

Open source face recognition for Android

macgyver offers face detection programs via a simple to use API.

The program below takes a reference to a public image and will return an array of the coordinates and dimensions of any faces detected in the image.

MySQL & Java - Get id of the last inserted value (JDBC)

Alternatively you can do:

Statement stmt = db.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
numero = stmt.executeUpdate();

ResultSet rs = stmt.getGeneratedKeys();
if ({

But use Sean Bright's answer instead for your scenario.

Using request.setAttribute in a JSP page

i think phil is right request option is available till the page load. so if we want to sent value to another page we want to set the in the hidden tag or in side the session if you just need the value only on another page and not more than that then hidden tags are best option if you need that value on more than one page at that time session is the better option than hidden tags.

How to display (print) vector in Matlab?

To print a vector which possibly has complex numbers-

fprintf('Answer: %s\n', sprintf('%d ', num2str(x)));

How to rename with prefix/suffix?

I've seen people mention a rename command, but it is not routinely available on Unix systems (as opposed to Linux systems, say, or Cygwin - on both of which, rename is an executable rather than a script). That version of rename has a fairly limited functionality:

rename from to file ...

It replaces the from part of the file names with the to, and the example given in the man page is:

rename foo foo0 foo? foo??

This renames foo1 to foo01, and foo10 to foo010, etc.

I use a Perl script called rename, which I originally dug out from the first edition Camel book, circa 1992, and then extended, to rename files.

#!/bin/perl -w
# @(#)$Id:,v 1.7 2008/02/16 07:53:08 jleffler Exp $
# Rename files using a Perl substitute or transliterate command

use strict;
use Getopt::Std;

my($usage) = "Usage: $0 [-fnxV] perlexpr [filenames]\n";
my($force) = 0;
my($noexc) = 0;
my($trace) = 0;

die $usage unless getopts('fnxV', \%opts);

if ($opts{V})
    printf "%s\n", q'RENAME Version $Revision: 1.7 $ ($Date: 2008/02/16 07:53:08 $)';
    exit 0;
$force = 1 if ($opts{f});
$noexc = 1 if ($opts{n});
$trace = 1 if ($opts{x});

my($op) = shift;
die $usage unless defined $op;

if (!@ARGV) {
    @ARGV = <STDIN>;

for (@ARGV)
    if (-e $_ || -l $_)
        my($was) = $_;
        eval $op;
        die $@ if $@;
        next if ($was eq $_);
        if ($force == 0 && -f $_)
            print STDERR "rename failed: $was - $_ exists\n";
            print "+ $was --> $_\n" if $trace;
            print STDERR "rename failed: $was - $!\n"
                unless ($noexc || rename($was, $_));
        print STDERR "$_ - $!\n";

This allows you to write any Perl substitute or transliterate command to map file names. In the specific example requested, you'd use:

rename 's/^/new./' original.filename

How to use onSavedInstanceState example please

If Data Is not Loaded From savedInstanceState use following code.
The problem is url call is not to complete fully so, check if data is loaded then to show the instanceState value.

//suppose data is not Loaded to savedInstanceState at 1st swipe
if (savedInstanceState == null && !mAlreadyLoaded){
    mAlreadyLoaded = true;
    GetStoryData();//Url Call
} else {
    if (listArray != null) {  //Data Array From JsonArray(ListArray)
        System.out.println("LocalData  " + listArray);
        GetStoryData();//Url Call

What is this CSS selector? [class*="span"]

.show-grid [class*="span"]

It's a CSS selector that selects all elements with the class show-grid that has a child element whose class contains the name span.

Operator overloading in Java

Just use Xtend along with your Java code. It supports Operator Overloading:

    package com.example;

public class Test {
  protected int wrapped;

  public Test(final int value) {
    this.wrapped = value;

  public int operator_plus(final Test e2) {
    return (this.wrapped + e2.wrapped);

package com.example

class Test2 {

    new() {
        val t1 = new Test(3)
        val t2 = new Test(5)
        val t3 = t1 + t2


On the official website, there is a list of the methods to implement for each operator !

How to open a web page automatically in full screen mode

You can go fullscreen automatically by putting this code in:

var elem = document.documentElement; if (elem.requestFullscreen) { elem.requestFullscreen() }


note: does not always work for security reasons. but it works for me at least. does not work when inspecting and pasting the code.

How can I get the Windows last reboot reason

Take a look at the Event Log API. Case a) (bluescreen, user cut the power cord or system hang) causes a note ('system did not shutdown correctly' or something like that) to be left in the 'System' event log the next time the system is rebooted properly. You should be able to access it programmatically using the above API (honestly, I've never used it but it should work).

Safe String to BigDecimal conversion

String value = "1,000,000,000.999999999999999";
BigDecimal money = new BigDecimal(value.replaceAll(",", ""));

Full code to prove that no NumberFormatException is thrown:

import java.math.BigDecimal;

public class Tester {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String value = "1,000,000,000.999999999999999";
        BigDecimal money = new BigDecimal(value.replaceAll(",", ""));



How to embed HTML into IPython output?

Expanding on @Harmon above, looks like you can combine the display and print statements together ... if you need. Or, maybe it's easier to just format your entire HTML as one string and then use display. Either way, nice feature.

display(HTML('<h1>Hello, world!</h1>'))
print("Here's a link:")
display(HTML("<a href='' target='_blank'></a>"))
print("some more printed text ...")
display(HTML('<p>Paragraph text here ...</p>'))

Outputs something like this:

Hello, world!

Here's a link:

some more printed text ...

Paragraph text here ...

Get all parameters from JSP page

HTML or Jsp Page         
<input type="text" name="1UserName">
<input type="text" name="2Password">
<Input type="text" name="3MobileNo">
<input type="text" name="4country">
and so on...
in java Code 

 SortedSet ss = new TreeSet();
 Enumeration<String> enm=request.getParameterNames();
    String pname = enm.nextElement();
Iterator i=ss.iterator();
    String param=(String);
    String value=request.getParameter(param);

SqlDataAdapter vs SqlDataReader

A SqlDataAdapter is typically used to fill a DataSet or DataTable and so you will have access to the data after your connection has been closed (disconnected access).

The SqlDataReader is a fast forward-only and connected cursor which tends to be generally quicker than filling a DataSet/DataTable.

Furthermore, with a SqlDataReader, you deal with your data one record at a time, and don't hold any data in memory. Obviously with a DataTable or DataSet, you do have a memory allocation overhead.

If you don't need to keep your data in memory, so for rendering stuff only, go for the SqlDataReader. If you want to deal with your data in a disconnected fashion choose the DataAdapter to fill either a DataSet or DataTable.

NoClassDefFoundError on Maven dependency

For some reason, the lib is present while compiling, but missing while running.

My situation is, two versions of one lib conflict.

For example, A depends on B and C, while B depends on D:1.0, C depends on D:1.1, maven may just import D:1.0. If A uses one class which is in D:1.1 but not in D:1.0, a NoClassDefFoundError will be throwed.

If you are in this situation too, you need to resolve the dependency conflict.

Run all SQL files in a directory

Use FOR. From the command prompt:

c:\>for %f in (*.sql) do sqlcmd /S <servername> /d <dbname> /E /i "%f"

Find mouse position relative to element

You can use getBoudingClientRect() of the relative parent.

document.addEventListener("mousemove", (e) => {
  let xCoord = e.clientX - + e.offsetX
  let yCoord = e.clientY - + e.offsetY
  console.log("xCoord", xCoord, "yCoord", yCoord)

"sed" command in bash

sed is the Stream EDitor. It can do a whole pile of really cool things, but the most common is text replacement.

The s,%,$,g part of the command line is the sed command to execute. The s stands for substitute, the , characters are delimiters (other characters can be used; /, : and @ are popular). The % is the pattern to match (here a literal percent sign) and the $ is the second pattern to match (here a literal dollar sign). The g at the end means to globally replace on each line (otherwise it would only update the first match).

Cannot catch toolbar home button click event

If you want to know when home is clicked is an AppCompatActivity then you should try it like this:

First tell Android you want to use your Toolbar as your ActionBar:


Then set Home to be displayed via setDisplayShowHomeEnabled like this:


Finally listen for click events on like usual:

public boolean onOptionsItemSelected(MenuItem menuItem) {
    if (menuItem.getItemId() == {
        Timber.d("Home pressed");
    return super.onOptionsItemSelected(menuItem);

If you want to know when the navigation button is clicked on a Toolbar in a class other than AppCompatActivity you can use these methods to set a navigation icon and listen for click events on it. The navigation icon will appear on the left side of your Toolbar where the the "home" button used to be.

toolbar.setNavigationOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        Log.d("cek", "home selected");

If you want to know when the hamburger is clicked and when the drawer opens, you're already listening for these events via onDrawerOpened and onDrawerClosed so you'll want to see if those callbacks fit your requirements.

How do I access the $scope variable in browser's console using AngularJS?

Pick an element in the HTML panel of the developer tools and type this in the console:


In WebKit and Firefox, $0 is a reference to the selected DOM node in the elements tab, so by doing this you get the selected DOM node scope printed out in the console.

You can also target the scope by element ID, like so:



There are some very useful Chrome extensions that you might want to check out:

  • Batarang. This has been around for a while.

  • ng-inspector. This is the newest one, and as the name suggests, it allows you to inspect your application's scopes.

Playing with jsFiddle

When working with jsfiddle you can open the fiddle in show mode by adding /show at the end of the URL. When running like this you have access to the angular global. You can try it here:

jQuery Lite

If you load jQuery before AngularJS, angular.element can be passed a jQuery selector. So you could inspect the scope of a controller with


Of a button


... and so on.

You might actually want to use a global function to make it easier:

window.SC = function(selector){
    return angular.element(selector).scope();

Now you could do this

SC('button:eq(10)').row   // -> value of scope.row

Check here:

How do I get the current date in JavaScript?

You can use this

function my_curr_date() {      
    var currentDate = new Date()
    var day = currentDate.getDate();
    var month = currentDate.getMonth() + 1;
    var year = currentDate.getFullYear();
    var my_date = month+"-"+day+"-"+year;

The HTML is

<body onload='return my_curr_date();'>
    <input type='text' name='dateField' id='dateField' value='' />

firefox proxy settings via command line

The easiest way to do this is to configure your Firefox to use a PAC with a file URL, and then change the file URL from the line command before you start Firefox.

This is the easiest way. You don't have to write a script that remembers what path to prefs.js is (which might change over time).

You configure your profile once, and then you edit the external file whenever you want.

Resize external website content to fit iFrame width

Tip for 1 website resizing the height. But you can change to 2 websites.

Here is my code to resize an iframe with an external website. You need insert a code into the parent (with iframe code) page and in the external website as well, so, this won't work with you don't have access to edit the external website.

  • local (iframe) page: just insert a code snippet
  • remote (external) page: you need a "body onload" and a "div" that holds all contents. And body needs to be styled to "margin:0"


<IFRAME STYLE="width:100%;height:1px" SRC="" FRAMEBORDER="no" BORDER="0" SCROLLING="no" ID="estframe"></IFRAME>

var eventMethod = window.addEventListener ? "addEventListener" : "attachEvent";
var eventer = window[eventMethod];
var messageEvent = eventMethod == "attachEvent" ? "onmessage" : "message";
eventer(messageEvent,function(e) {
  if (,3)=='frm') document.getElementById('estframe').style.height = + 'px';

You need this "frm" prefix to avoid problems with other embeded codes like Twitter or Facebook plugins. If you have a plain page, you can remove the "if" and the "frm" prefix on both pages (script and onload).


You need jQuery to accomplish about "real" page height. I cannot realize how to do with pure JavaScript since you'll have problem when resize the height down (higher to lower height) using body.scrollHeight or related. For some reason, it will return always the biggest height (pre-redimensioned).

<BODY onload="parent.postMessage('frm'+$('#master').height(),'*')" STYLE="margin:0">
<SCRIPT SRC="path-to-jquery/jquery.min.js"></SCRIPT>
<DIV ID="master">
your content

So, parent page (iframe) has a 1px default height. The script inserts a "wait for message/event" from the iframe. When a message (post message) is received and the first 3 chars are "frm" (to avoid the mentioned problem), will get the number from 4th position and set the iframe height (style), including 'px' unit.

The external site (loaded in the iframe) will "send a message" to the parent (opener) with the "frm" and the height of the main div (in this case id "master"). The "*" in postmessage means "any source".

Hope this helps. Sorry for my english.

git: patch does not apply

This command will apply the patch not resolving it leaving bad files as *.rej:

git apply --reject --whitespace=fix mypath.patch

You just have to resolve them. Once resolved run:

git -am resolved

How to change a dataframe column from String type to Double type in PySpark?

Given answers are enough to deal with the problem but I want to share another way which may be introduced the new version of Spark (I am not sure about it) so given answer didn't catch it.

We can reach the column in spark statement with col("colum_name") keyword:

from pyspark.sql.functions import col , column
changedTypedf = joindf.withColumn("show", col("show").cast("double"))

HttpWebRequest using Basic authentication

The following construction was not working correctly for me:

request.Credentials = new NetworkCredential("user", "pass");

I have used CredentialCache instead:

CredentialCache credentialCache = new CredentialCache
        new Uri($"http://{request.Host}/"), "Basic",
        new NetworkCredential("user", "pass")
request.Credentials = credentialCache;

However, if you would like to add multiple basic auth credentials (for example if there is redirection that you are aware of) you can use following function that I have made:

private void SetNetworkCredential(Uri uriPrefix, string authType, NetworkCredential credential)
    if (request.Credentials == null)
        request.Credentials = new CredentialCache();

    if (request.Credentials.GetCredential(uriPrefix, authType) == null)
        (request.Credentials as CredentialCache).Add(uriPrefix, authType, credential);

I hope it will help somebody in the future.

Copying sets Java

The copy constructor given by @Stephen C is the way to go when you have a Set you created (or when you know where it comes from). When it comes from a Map.entrySet(), it will depend on the Map implementation you're using:

findbugs says

The entrySet() method is allowed to return a view of the underlying Map in which a single Entry object is reused and returned during the iteration. As of Java 1.6, both IdentityHashMap and EnumMap did so. When iterating through such a Map, the Entry value is only valid until you advance to the next iteration. If, for example, you try to pass such an entrySet to an addAll method, things will go badly wrong.

As addAll() is called by the copy constructor, you might find yourself with a Set of only one Entry: the last one.

Not all Map implementations do that though, so if you know your implementation is safe in that regard, the copy constructor definitely is the way to go. Otherwise, you'd have to create new Entry objects yourself:

Set<K,V> copy = new HashSet<K,V>(map.size());
for (Entry<K,V> e : map.entrySet())
    copy.add(new java.util.AbstractMap.SimpleEntry<K,V>(e));

Edit: Unlike tests I performed on Java 7 and Java 6u45 (thanks to Stephen C), the findbugs comment does not seem appropriate anymore. It might have been the case on earlier versions of Java 6 (before u45) but I don't have any to test.

Rendering a template variable as HTML

The simplest way is to use the safe filter:

{{ message|safe }}

Check out the Django documentation for the safe filter for more information.

vba pass a group of cells as range to function

As I'm beginner for vba, I'm willing to get a deep knowledge of vba of how all excel in-built functions work form there back.

So as on the above question I have putted my basic efforts.

Function multi_add(a As Range, ParamArray b() As Variant) As Double

    Dim ele As Variant

    Dim i As Long

    For Each ele In a
        multi_add = a + ele.Value **- a**
    Next ele

    For i = LBound(b) To UBound(b)
        For Each ele In b(i)
            multi_add = multi_add + ele.Value
        Next ele
    Next i

End Function

- a: This is subtracted for above code cause a count doubles itself so what values you adds it will add first value twice.

Create stacked barplot where each stack is scaled to sum to 100%

prop.table is a nice friendly way of obtaining proportions of tables.

m <- matrix(1:4,2)

     [,1] [,2]
[1,]    1    3
[2,]    2    4

Leaving margin blank gives you proportions of the whole table

 prop.table(m, margin=NULL)
     [,1] [,2]
[1,]  0.1  0.3
[2,]  0.2  0.4

Giving it 1 gives you row proportions

 prop.table(m, 1)
      [,1]      [,2]
[1,] 0.2500000 0.7500000
[2,] 0.3333333 0.6666667

And 2 is column proportions

 prop.table(m, 2)
          [,1]      [,2]
[1,] 0.3333333 0.4285714
[2,] 0.6666667 0.5714286

How do I view the list of functions a Linux shared library is exporting?

On a MAC, you need to use nm *.o | c++filt, as there is no -C option in nm.

Why does instanceof return false for some literals?

The primitive wrapper types are reference types that are automatically created behind the scenes whenever strings, num­bers, or Booleans are read.For example :

var name = "foo";
var firstChar = name.charAt(0);

This is what happens behind the scenes:

// what the JavaScript engine does
var name = "foo";
var temp = new String(name);
var firstChar = temp.charAt(0);
temp = null;

Because the second line uses a string (a primitive) like an object, the JavaScript engine creates an instance of String so that charAt(0) will work.The String object exists only for one statement before it’s destroyed check this

The instanceof operator returns false because a temporary object is created only when a value is read. Because instanceof doesn’t actually read anything, no temporary objects are created, and it tells us the ­values aren’t instances of primitive wrapper types. You can create primitive wrapper types manually

How do I install a NuGet package .nupkg file locally?

On Linux, with NuGet CLI, the commands are similar. To install my.nupkg, run

nuget add -Source some/directory my.nupkg

Then run dotnet restore from that directory

dotnet restore --source some/directory Project.sln

or add that directory as a NuGet source

nuget sources Add -Name MySource -Source some/directory

and then tell msbuild to use that directory with /p:RestoreAdditionalSources=MySource or /p:RestoreSources=MySource. The second switch will disable all other sources, which is good for offline scenarios, for example.

How to select only 1 row from oracle sql?

There is no limit 1 condition (thats MySQL / PostgresSQL) in Oracle, you need to specify where rownum = 1.

Get list of data-* attributes using javascript / jQuery

A pure JavaScript solution ought to be offered as well, as the solution is not difficult:

var a = [], function(at) { return /^data-/.test(; });

This gives an array of attribute objects, which have name and value properties:

if (a.length) {
    var firstAttributeName = a[0].name;
    var firstAttributeValue = a[0].value;

Edit: To take it a step further, you can get a dictionary by iterating the attributes and populating a data object:

var data = {};
[], function(attr) {
    if (/^data-/.test( {
        var camelCaseName =, function ($0, $1) {
            return $1.toUpperCase();
        data[camelCaseName] = attr.value;

You could then access the value of, for example, data-my-value="2" as data.myValue;

Edit: If you wanted to set data attributes on your element programmatically from an object, you could:

Object.keys(data).forEach(function(key) {
    var attrName = "data-" + key.replace(/[A-Z]/g, function($0) {
        return "-" + $0.toLowerCase();
    el.setAttribute(attrName, data[key]);

EDIT: If you are using babel or TypeScript, or coding only for es6 browsers, this is a nice place to use es6 arrow functions, and shorten the code a bit:

var a = [], at => /^data-/.test(;

Can a JSON value contain a multiline string

Per the specification, the JSON grammar's char production can take the following values:

  • any-Unicode-character-except-"-or-\-or-control-character
  • \"
  • \\
  • \/
  • \b
  • \f
  • \n
  • \r
  • \t
  • \u four-hex-digits

Newlines are "control characters", so no, you may not have a literal newline within your string. However, you may encode it using whatever combination of \n and \r you require.

The JSONLint tool confirms that your JSON is invalid.

And, if you want to write newlines inside your JSON syntax without actually including newlines in the data, then you're doubly out of luck. While JSON is intended to be human-friendly to a degree, it is still data and you're trying to apply arbitrary formatting to that data. That is absolutely not what JSON is about.

Is there an upside down caret character?

An upside-down circumflex is called a caron, or a hácek.

It has an HTML entity in the TADS Latin-2 extension to HTML: &caron; and looks like this: ˇ which unfortunately doesn't display in the same size/proportion as the ^ caret.

Or you can use the unicode U+30C.

Laravel Blade html image

you can Using asset() you can directly access to the image folder.

<img src="{{asset('img/stuvi-logo.png')}}" alt="logo" class="img-size-50 mr-3 img-circle">

Best way to check function arguments?

def someFunc(a, b, c):
    params = locals()
    for _item in params:
        print type(params[_item]), _item, params[_item]


>> someFunc(1, 'asd', 1.0)
>> <type 'int'> a 1
>> <type 'float'> c 1.0
>> <type 'str'> b asd

more about locals()

When to use single quotes, double quotes, and backticks in MySQL

Backticks are to be used for table and column identifiers, but are only necessary when the identifier is a MySQL reserved keyword, or when the identifier contains whitespace characters or characters beyond a limited set (see below) It is often recommended to avoid using reserved keywords as column or table identifiers when possible, avoiding the quoting issue.

Single quotes should be used for string values like in the VALUES() list. Double quotes are supported by MySQL for string values as well, but single quotes are more widely accepted by other RDBMS, so it is a good habit to use single quotes instead of double.

MySQL also expects DATE and DATETIME literal values to be single-quoted as strings like '2001-01-01 00:00:00'. Consult the Date and Time Literals documentation for more details, in particular alternatives to using the hyphen - as a segment delimiter in date strings.

So using your example, I would double-quote the PHP string and use single quotes on the values 'val1', 'val2'. NULL is a MySQL keyword, and a special (non)-value, and is therefore unquoted.

None of these table or column identifiers are reserved words or make use of characters requiring quoting, but I've quoted them anyway with backticks (more on this later...).

Functions native to the RDBMS (for example, NOW() in MySQL) should not be quoted, although their arguments are subject to the same string or identifier quoting rules already mentioned.

Backtick (`)
table & column ------------------------------------------------------+
                      ?     ?  ?  ?  ?    ?  ?    ?  ?    ?  ?       ?
$query = "INSERT INTO `table` (`id`, `col1`, `col2`, `date`, `updated`) 
                       VALUES (NULL, 'val1', 'val2', '2001-01-01', NOW())";
                               ????  ?    ?  ?    ?  ?          ?  ????? 
Unquoted keyword          --------+  ¦    ¦  ¦    ¦  ¦          ¦  ¦¦¦¦¦
Single-quoted (') strings ------------------------+  ¦          ¦  ¦¦¦¦¦
Single-quoted (') DATE    --------------------------------------+  ¦¦¦¦¦
Unquoted function         ---------------------------------------------+    

Variable interpolation

The quoting patterns for variables do not change, although if you intend to interpolate the variables directly in a string, it must be double-quoted in PHP. Just make sure that you have properly escaped the variables for use in SQL. (It is recommended to use an API supporting prepared statements instead, as protection against SQL injection).

// Same thing with some variable replacements
// Here, a variable table name $table is backtick-quoted, and variables
// in the VALUES list are single-quoted 
$query = "INSERT INTO `$table` (`id`, `col1`, `col2`, `date`) VALUES (NULL, '$val1', '$val2', '$date')";

Prepared statements

When working with prepared statements, consult the documentation to determine whether or not the statement's placeholders must be quoted. The most popular APIs available in PHP, PDO and MySQLi, expect unquoted placeholders, as do most prepared statement APIs in other languages:

// PDO example with named parameters, unquoted
$query = "INSERT INTO `table` (`id`, `col1`, `col2`, `date`) VALUES (:id, :col1, :col2, :date)";

// MySQLi example with ? parameters, unquoted
$query = "INSERT INTO `table` (`id`, `col1`, `col2`, `date`) VALUES (?, ?, ?, ?)";

Characters requring backtick quoting in identifiers:

According to MySQL documentation, you do not need to quote (backtick) identifiers using the following character set:

ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9, dollar, underscore)

You can use characters beyond that set as table or column identifiers, including whitespace for example, but then you must quote (backtick) them.

Also, although numbers are valid characters for identifiers, identifiers cannot consist solely of numbers. If they do they must be wrapped in backticks.

How do I verify that a string only contains letters, numbers, underscores and dashes?

If it were not for the dashes and underscores, the easiest solution would be


(Section 3.6.1 of the Python Library Reference)

How do you implement a Stack and a Queue in JavaScript?

var stack = [];
stack.push(2);       // stack is now [2]
stack.push(5);       // stack is now [2, 5]
var i = stack.pop(); // stack is now [2]
alert(i);            // displays 5

var queue = [];
queue.push(2);         // queue is now [2]
queue.push(5);         // queue is now [2, 5]
var i = queue.shift(); // queue is now [5]
alert(i);              // displays 2

taken from "9 javascript tips you may not know"

Python: TypeError: cannot concatenate 'str' and 'int' objects

c = a + b 

Actually, in this last line you are not changing the type of the variable c. If you do

print "a + b as integers: " + c_str

it should work.

How can I use pickle to save a dict?

Try this:

import pickle

a = {'hello': 'world'}

with open('filename.pickle', 'wb') as handle:
    pickle.dump(a, handle, protocol=pickle.HIGHEST_PROTOCOL)

with open('filename.pickle', 'rb') as handle:
    b = pickle.load(handle)

print a == b

How to run 'sudo' command in windows

There is no sudo command in case of windows and also there is no need to put any $. For installing Angular CLI through node.js command prompt in windows, I just wrote npm install -g @angular/cli and then pressed Enter. It worked fine.

Android Emulator Error Message: "PANIC: Missing emulator engine program for 'x86' CPUS."

This worked for me on macOS:

echo 'export PATH=$PATH:'$HOME'/Library/Android/sdk/emulator:'$HOME'/Library/Android/sdk/tools:'$HOME'/Library/Android/sdk/platform-tools' >> ~/.bash_profile
source ~/.bash_profile

Get current date in milliseconds

Casting the NSTimeInterval directly to a long overflowed for me, so instead I had to cast to a long long.

long long milliseconds = (long long)([[NSDate date] timeIntervalSince1970] * 1000.0);

The result is a 13 digit timestamp as in Unix.

How to make a div with a circular shape?

You can do following


<div id="circle"></div>


#circle {
    width: 100px;
    height: 100px;
    background: red;
    -moz-border-radius: 50px;
    -webkit-border-radius: 50px;
    border-radius: 50px;

Other shape SOURCE

Difference between Role and GrantedAuthority in Spring Security

AFAIK GrantedAuthority and roles are same in spring security. GrantedAuthority's getAuthority() string is the role (as per default implementation SimpleGrantedAuthority).

For your case may be you can use Hierarchical Roles

<bean id="roleVoter" class="">
    <constructor-arg ref="roleHierarchy" />
<bean id="roleHierarchy"
    <property name="hierarchy">
            ROLE_ADMIN > ROLE_createSubUsers
            ROLE_ADMIN > ROLE_deleteAccounts 
            ROLE_USER > ROLE_viewAccounts

Not the exact sol you looking for, but hope it helps

Edit: Reply to your comment

Role is like a permission in spring-security. using intercept-url with hasRole provides a very fine grained control of what operation is allowed for which role/permission.

The way we handle in our application is, we define permission (i.e. role) for each operation (or rest url) for e.g. view_account, delete_account, add_account etc. Then we create logical profiles for each user like admin, guest_user, normal_user. The profiles are just logical grouping of permissions, independent of spring-security. When a new user is added, a profile is assigned to it (having all permissible permissions). Now when ever user try to perform some action, permission/role for that action is checked against user grantedAuthorities.

Also the defaultn RoleVoter uses prefix ROLE_, so any authority starting with ROLE_ is considered as role, you can change this default behavior by using a custom RolePrefix in role voter and using it in spring security.

How to Insert BOOL Value to MySQL Database

TRUE and FALSE are keywords, and should not be quoted as strings:


By quoting them as strings, MySQL will then cast them to their integer equivalent (since booleans are really just a one-byte INT in MySQL), which translates into zero for any non-numeric string. Thus, you get 0 for both values in your table.

Non-numeric strings cast to zero:

|                      0 |                       0 |                   12345 |

But the keywords return their corresponding INT representation:

|    1 |     0 |

Note also, that I have replaced your double-quotes with single quotes as are more standard SQL string enclosures. Finally, I have replaced your empty strings for id with NULL. The empty string may issue a warning.

Connecting to remote MySQL server using PHP

It is very easy to connect remote MySQL Server Using PHP, what you have to do is:

  1. Create a MySQL User in remote server.

  2. Give Full privilege to the User.

  3. Connect to the Server using PHP Code (Sample Given Below)

$link = mysql_connect('your_my_sql_servername or IP Address', 'new_user_which_u_created', 'password');
if (!$link) {
    die('Could not connect: ' . mysql_error());

echo 'Connected successfully';

mysql_select_db('sandsbtob',$link) or die ("could not open db".mysql_error());
// we connect to localhost at port 3306

How to access single elements in a table in R

?"[" pretty much covers the various ways of accessing elements of things.

Under usage it lists these:

x[i, j, ... , drop = TRUE]
x[[i, exact = TRUE]]
x[[i, j, ..., exact = TRUE]]
getElement(object, name)

x[i] <- value
x[i, j, ...] <- value
x[[i]] <- value
x$i <- value

The second item is sufficient for your purpose

Under Arguments it points out that with [ the arguments i and j can be numeric, character or logical

So these work:


As does this:


and keeping in mind a data frame is a list of vectors:


will also both work.

So that's a few things to be going on with. I suggest you type in the examples at the bottom of the help page one line at a time (yes, actually type the whole thing in one line at a time and see what they all do, you'll pick up stuff very quickly and the typing rather than copypasting is an important part of helping to commit it to memory.)

What are the lengths of Location Coordinates, latitude and longitude?

Latitude maximum in total is: 9 (12.3456789), longitude 10 (123.4567890), they both have maximum 7 decimals chars (At least is what i can find in Google Maps),

For example, both columns in Rails and Postgresql looks something like this:

t.decimal :latitude, precision: 9, scale: 7
t.decimal :longitude, precision: 10, scale: 7

What are all the possible values for HTTP "Content-Type" header?

As is defined in RFC 1341:

In the Extended BNF notation of RFC 822, a Content-Type header field value is defined as follows:

Content-Type := type "/" subtype *[";" parameter]

type := "application" / "audio" / "image" / "message" / "multipart" / "text" / "video" / x-token

x-token := < The two characters "X-" followed, with no intervening white space, by any token >

subtype := token

parameter := attribute "=" value

attribute := token

value := token / quoted-string

token := 1*

tspecials := "(" / ")" / "<" / ">" / "@" ; Must be in / "," / ";" / ":" / "\" / <"> ; quoted-string, / "/" / "[" / "]" / "?" / "." ; to use within / "=" ; parameter values

And a list of known MIME types that can follow it (or, as Joe remarks, the IANA source).

As you can see the list is way too big for you to validate against all of them. What you can do is validate against the general format and the type attribute to make sure that is correct (the set of options is small) and just assume that what follows it is correct (and of course catch any exceptions you might encounter when you put it to actual use).

Also note the comment above:

If another primary type is to be used for any reason, it must be given a name starting with "X-" to indicate its non-standard status and to avoid any potential conflict with a future official name.

You'll notice that a lot of HTTP requests/responses include an X- header of some sort which are self defined, keep this in mind when validating the types.

php: loop through json array

First you have to decode your json :

$array = json_decode($the_json_code);

Then after the json decoded you have to do the foreach

foreach ($array as $key => $jsons) { // This will search in the 2 jsons
     foreach($jsons as $key => $value) {
         echo $value; // This will show jsut the value f each key like "var1" will print 9
                       // And then goes print 16,16,8 ...

If you want something specific just ask for a key like this. Put this between the last foreach.

if($key == 'var1'){
 echo $value;

ES6 modules in the browser: Uncaught SyntaxError: Unexpected token import

Unfortunately, modules aren't supported by many browsers right now.

This feature is only just beginning to be implemented in browsers natively at this time. It is implemented in many transpilers, such as TypeScript and Babel, and bundlers such as Rollup and Webpack.

Found on MDN

SELECT * FROM multiple tables. MySQL

What you do here is called a JOIN (although you do it implicitly because you select from multiple tables). This means, if you didn't put any conditions in your WHERE clause, you had all combinations of those tables. Only with your condition you restrict your join to those rows where the drink id matches.

But there are still X multiple rows in the result for every drink, if there are X photos with this particular drinks_id. Your statement doesn't restrict which photo(s) you want to have!

If you only want one row per drink, you have to tell SQL what you want to do if there are multiple rows with a particular drinks_id. For this you need grouping and an aggregate function. You tell SQL which entries you want to group together (for example all equal drinks_ids) and in the SELECT, you have to tell which of the distinct entries for each grouped result row should be taken. For numbers, this can be average, minimum, maximum (to name some).

In your case, I can't see the sense to query the photos for drinks if you only want one row. You probably thought you could have an array of photos in your result for each drink, but SQL can't do this. If you only want any photo and you don't care which you'll get, just group by the drinks_id (in order to get only one row per drink):

SELECT name, price, photo
FROM drinks, drinks_photos
WHERE = drinks_id 
GROUP BY drinks_id

name     price   photo
fanta    5       ./images/fanta-1.jpg
dew      4       ./images/dew-1.jpg

In MySQL, we also have GROUP_CONCAT, if you want the file names to be concatenated to one single string:

SELECT name, price, GROUP_CONCAT(photo, ',')
FROM drinks, drinks_photos
WHERE = drinks_id 
GROUP BY drinks_id

name     price   photo
fanta    5       ./images/fanta-1.jpg,./images/fanta-2.jpg,./images/fanta-3.jpg
dew      4       ./images/dew-1.jpg,./images/dew-2.jpg

However, this can get dangerous if you have , within the field values, since most likely you want to split this again on the client side. It is also not a standard SQL aggregate function.

Using if-else in JSP

It's almost always advisable to not use scriptlets in your JSP. They're considered bad form. Instead, try using JSTL (JSP Standard Tag Library) combined with EL (Expression Language) to run the conditional logic you're trying to do. As an added benefit, JSTL also includes other important features like looping.

Instead of:

<%String user=request.getParameter("user"); %>
<%if(user == null || user.length() == 0){
    out.print("I see! You don't have a name.. well.. Hello no name");   
else {%>
    <%@ include file="response.jsp" %>
<% } %>


    <c:when test="${empty user}">
        I see!  You don't have a name.. well.. Hello no name
        <%@ include file="response.jsp" %>

Also, unless you plan on using response.jsp somewhere else in your code, it might be easier to just include the html in your otherwise statement:


Also of note. To use the core tag, you must import it as follows:

 <%@ taglib uri="" prefix="c" %>

You want to make it so the user will receive a message when the user submits a username. The easiest way to do this is to not print a message at all when the "user" param is null. You can do some validation to give an error message when the user submits null. This is a more standard approach to your problem. To accomplish this:

In scriptlet:

<% String user = request.getParameter("user");
   if( user != null && user.length() > 0 ) {
       <%@ include file="response.jsp" %>

In jstl:

<c:if test="${not empty user}">
    <%@ include file="response.jsp" %>

Mutex lock threads

A process consists of at least one thread (think of the main function). Multi threaded code will just spawn more threads. Mutexes are used to create locks around shared resources to avoid data corruption / unexpected / unwanted behaviour. Basically it provides for sequential execution in an asynchronous setup - the requirement for which stems from non-const non-atomic operations on shared data structures.

A vivid description of what mutexes would be the case of people (threads) queueing up to visit the restroom (shared resource). While one person (thread) is using the bathroom easing him/herself (non-const non-atomic operation), he/she should ensure the door is locked (mutex), otherwise it could lead to being caught in full monty (unwanted behaviour)

Psexec "run as (remote) admin"

Use psexec -s

The s switch will cause it to run under system account which is the same as running an elevated admin prompt. just used it to enable WinRM remotely.

Read Excel sheet in Powershell

There is the possibility of making something really more cool!

# Powershell 
$xl = new-object -ComObject excell.application
$doc.Sheets.item(1).rows |
% { ($_.value2 | Select-Object -first 3 | Select-Object -last 2) -join "," }

How to Check if value exists in a MySQL database

    IF city='C7'
    THEN city
    ELSE 'somethingelse'
    END as `city`
FROM `table` WHERE `city` = 'c7'

Javascript counting number of objects in object

Try Demo Here

var list ={}; var count= Object.keys(list).length;

How do you compare two version Strings in Java?

I liked the idea from @Peter Lawrey, And i extended it to further limits :

    * Normalize string array, 
    * Appends zeros if string from the array
    * has length smaller than the maxLen.
    private String normalize(String[] split, int maxLen){
        StringBuilder sb = new StringBuilder("");
        for(String s : split) {
            for(int i = 0; i<maxLen-s.length(); i++) sb.append('0');
        return sb.toString();

    * Removes trailing zeros of the form '.00.0...00'
    * (and does not remove zeros from, say, '4.1.100')
    public String removeTrailingZeros(String s){
        int i = s.length()-1;
        int k = s.length()-1;
        while(i >= 0 && (s.charAt(i) == '.' || s.charAt(i) == '0')){
          if(s.charAt(i) == '.') k = i-1;
        return s.substring(0,k+1);

    * Compares two versions(works for alphabets too),
    * Returns 1 if v1 > v2, returns 0 if v1 == v2,
    * and returns -1 if v1 < v2.
    public int compareVersion(String v1, String v2) {

        // Uncomment below two lines if for you, say, 4.1.0 is equal to 4.1
        // v1 = removeTrailingZeros(v1);
        // v2 = removeTrailingZeros(v2);

        String[] splitv1 = v1.split("\\.");
        String[] splitv2 = v2.split("\\.");
        int maxLen = 0;
        for(String str : splitv1) maxLen = Math.max(maxLen, str.length());
        for(String str : splitv2) maxLen = Math.max(maxLen, str.length());
        int cmp = normalize(splitv1, maxLen).compareTo(normalize(splitv2, maxLen));
        return cmp > 0 ? 1 : (cmp < 0 ? -1 : 0);

Hope it helps someone. It passed all test cases in interviewbit and leetcode (need to uncomment two lines in compareVersion function).

Easily tested !

Formatting floats without trailing zeros

Me, I'd do ('%f' % x).rstrip('0').rstrip('.') -- guarantees fixed-point formatting rather than scientific notation, etc etc. Yeah, not as slick and elegant as %g, but, it works (and I don't know how to force %g to never use scientific notation;-).

How to tell if tensorflow is using gpu acceleration from inside python shell?


The recommended way in which to check if TensorFlow is using GPU is the following:


As of TensorFlow 2.1, tf.test.gpu_device_name() has been deprecated in favour of the aforementioned.

Then, in the terminal you can use nvidia-smi to check how much GPU memory has been alloted; at the same time, using watch -n K nvidia-smi would tell you for example every K seconds how much memory you are using (you may want to use K = 1 for real-time)

If you have multiple GPUs and you want to use multiple networks, each one on a separated GPU, you can use:

 with tf.device('/GPU:0'):
      neural_network_1 = initialize_network_1()
 with tf.device('/GPU:1'):
      neural_network_2 = initialize_network_2()

How to get href value using jQuery?

You can get current href value by this code:


To get href value by ID


php_network_getaddresses: getaddrinfo failed: Name or service not known

If you only want to submit GET data to the URL, you should use something straightforward like file_get_contents();

$myGetData = "?var1=val1&var2=val2";

How can I convert a .jar to an .exe?

Launch4j works on both Windows and Linux/Mac. But if you're running Linux/Mac, there is a way to embed your jar into a shell script that performs the autolaunch for you, so you have only one runnable file:

MYSELF=`which "$0" 2>/dev/null`
[ $? -gt  0 -a -f "$0" ] && MYSELF="./$0"
# Parse options to determine which ones are for Java and which ones are for the Program
while [ $# -gt 0 ] ; do
    case $1 in
        -Xm*) JAVA_OPT="$JAVA_OPT $1" ;;
        -D*)  JAVA_OPT="$JAVA_OPT $1" ;;
        *)    PROG_OPT="$PROG_OPT $1" ;;
exec java $JAVA_OPT -jar $MYSELF $PROG_OPT

Then you create your runnable file from your jar:

$ cat myrunnablejar.jar > myrunnable
$ chmod +x myrunnable

It works the same way launch4j works: because a jar has a zip format, which header is located at the end of the file. You can have any header you want (either binary executable or, like here, shell script) and run java -jar <myexe>, as <myexe> is a valid zip/jar file.

How to read a text file directly from Internet using Java?

What really worked to me: (source: oracle documentation "reading url")


 public class UrlTextfile {
public static void main(String[] args) throws Exception {

    URL oracle = new URL("");
    BufferedReader in = new BufferedReader(
    new InputStreamReader(oracle.openStream()));

    String inputLine;
    while ((inputLine = in.readLine()) != null)

Warning: mysqli_query() expects parameter 1 to be mysqli, null given in

The getPosts() function seems to be expecting $con to be global, but you're not declaring it as such.

A lot of programmers regard bald global variables as a "code smell". The alternative at the other end of the scale is to always pass around the connection resource. Partway between the two is a singleton call that always returns the same resource handle.

Resize command prompt through commands

Simply type

MODE [width],[height]


MODE 14,1

That is the smallest size possible.

MODE 1000,1000

is the largest possible, although it probably won't even fit your screen. If you want to minimize it, type

start /min [yourbatchfile/cmd]

and of course, to maximaze,

start /max [yourbatchfile/cmd]

I am currently working on doing this from the same batch files so that you don't have to have two or start it with cmd. of course, there are shortcuts, but I'm gonna try to figure it out.

powershell - extract file name and extension

If is from a text file and and presuming name file are surrounded by white spaces this is a way:

$a = get-content c:\myfile.txt

$b = $a | select-string -pattern "\s.+\..{3,4}\s" | select -ExpandProperty matches | select -ExpandProperty value

$b | % {"File name:{0} - Extension:{1}" -f $_.substring(0, $_.lastindexof('.')) , $_.substring($_.lastindexof('.'), ($_.length - $_.lastindexof('.'))) }

If is a file you can use something like this based on your needs:

$a = dir .\my.file.xlsx # or $a = get-item c:\my.file.xlsx 

    Directory: Microsoft.PowerShell.Core\FileSystem::C:\ps

Mode           LastWriteTime       Length Name
----           -------------       ------ ----
-a---      25/01/10    11.51          624 my.file.xlsx


twitter bootstrap 3.0 typeahead ajax example

Here is my step by step experience, inspired by typeahead examples, from a Scala/PlayFramework app we are working on.

In a script (convertible of course to JS) I have:

$ ->
  learners = new Bloodhound(
    datumTokenizer: Bloodhound.tokenizers.obj.whitespace("value")
    queryTokenizer: Bloodhound.tokenizers.whitespace
    remote: "/learner/namelike?nameLikeStr=%QUERY"
    minLength: 3
    hint: true
    name: "learners"
    displayKey: "value"
    source: learners.ttAdapter()

I included the typeahead bundle and my script on the page, and there is a div around my input field as follows:

<script [email protected]("javascripts/typeahead.bundle.js")></script>
<script [email protected]("javascripts/LearnerNameTypeAhead.js") type="text/javascript" ></script>
  <input name="firstName" id="firstName" class="typeahead" placeholder="First Name" value="@firstName">

The result is that for each character typed in the input field after the first minLength (3) characters, the page issues a GET request with a URL looking like /learner/namelike?nameLikeStr= plus the currently typed characters. The server code returns a json array of objects containing fields "id" and "value", for example like this:

[ {
    "id": "109",
    "value": "Graham Jones"
    "id": "5833",
    "value": "Hezekiah Jones"
} ]

For play I need something in the routes file:

GET /learner/namelike controllers.Learners.namesLike(nameLikeStr:String)

And finally, I set some of the styling for the dropdown, etc. in a new typeahead.css file which I included in the page's <head> (or accessible .css)

.tt-dropdown-menu {
  width: 252px;
  margin-top: 12px;
  padding: 8px 0;
  background-color: #fff;
  border: 1px solid #ccc;
  border: 1px solid rgba(0, 0, 0, 0.2);
  -webkit-border-radius: 8px;
     -moz-border-radius: 8px;
          border-radius: 8px;
  -webkit-box-shadow: 0 5px 10px rgba(0,0,0,.2);
     -moz-box-shadow: 0 5px 10px rgba(0,0,0,.2);
          box-shadow: 0 5px 10px rgba(0,0,0,.2);
.typeahead {
  background-color: #fff;
.typeahead:focus {
  border: 2px solid #0097cf;
.tt-query {
  -webkit-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075);
     -moz-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075);
          box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075);
.tt-hint {
  color: #999
.tt-suggestion {
  padding: 3px 20px;
  font-size: 18px;
  line-height: 24px;
} {
  color: #fff;
  background-color: #0097cf;
.tt-suggestion p {
  margin: 0;

Cannot instantiate the type List<Product>

List can be instantiated by any class implementing the interface.By this way,Java provides us polymorphic behaviour.See the example below:

List<String> list = new ArrayList<String>();

Instead of instantiating an ArrayList directly,I am using a List to refer to ArrayList object so that we are using only the List interface methods and do not care about its actual implementation.

Examples of classes implementing List are ArrayList,LinkedList,Vector.You probably want to create a List depending upon your requirements.

Example:- a LinkedList is more useful when you hve to do a number of inertion or deletions .Arraylist is more performance intensive as it is backed by a fixed size array and array contents have to be changed by moving or regrowing the array.

Again,using a List we can simply change our object instantiation without changing any code further in your programs.

Suppose we are using ArrayList<String> value = new ArrayList<String>();

we may use a specific method of ArrrayList and out code will not be robust

By using List<String> value = new ArrayList<String>();

we are making sure we are using only List interface methods..and if we want to change it to a LinkedList we simply have to change the code :

List<String> value = new ArrayList<String>(); 

------ your code uses List interface methods.....

value = new LinkedList<String>(); 

-----your code still uses List interface methods and we do not have to change anything---- and we dont have to change anything in our code further

By the way a LinkedList also works a Deque which obviously also you cannot instantiate as it is also an interface

How to randomize (or permute) a dataframe rowwise and columnwise?

Of course you can sample each row:

sapply (1:4, function (row) df1[row,]<<-sample(df1[row,]))

will shuffle the rows itself, so the number of 1's in each row doesn't change. Small changes and it also works great with columns, but this is a exercise for the reader :-P

How to get GMT date in yyyy-mm-dd hh:mm:ss in PHP

Use below date function to get current time in MySQL format/(As requested on question also)

echo date("Y-m-d H:i:s", time());

ENOENT, no such file or directory

I had that issue : use path module

const path = require('path');

and also do not forget to create the uploads directory first period.

What is the convention in JSON for empty vs. null?

Empty array for empty collections and null for everything else.

How can I select item with class within a DIV?

try this instead $(".video-divs.focused"). This works if you are looking for video-divs that are focused.

How do I make a semi transparent background?

If you want to make transparent background is gray, pls try:


Check whether a cell contains a substring

Here is the formula I'm using

=IF( ISNUMBER(FIND(".",A1)), LEN(A1) - FIND(".",A1), 0 )

How to revert multiple git commits?

First be sure that your working copy is not modified. Then:

git diff --binary HEAD commit_sha_you_want_to_revert_to | git apply

and then just commit. Don't forget to document what's the reason for revert.

A generic list of anonymous class

In latest version 4.0, can use dynamic like below

var list = new List<dynamic>();
        list.Add(new {
            Name = "Damith"
        foreach(var item in list){

How to "inverse match" with regex?

In perl you can do

process($line) if ($line =~ !/Andrea/);

Getting rid of \n when using .readlines()

I used the strip function to get rid of newline character as split lines was throwing memory errors on 4 gb File.

Sample Code:

with open('C:\\aapl.csv','r') as apple:
    for apps in apple.readlines():

Bash Script : what does #!/bin/bash mean?

In bash script, what does #!/bin/bash at the 1st line mean ?

In Linux system, we have shell which interprets our UNIX commands. Now there are a number of shell in Unix system. Among them, there is a shell called bash which is very very common Linux and it has a long history. This is a by default shell in Linux.

When you write a script (collection of unix commands and so on) you have a option to specify which shell it can be used. Generally you can specify which shell it wold be by using Shebang(Yes that's what it's name).

So if you #!/bin/bash in the top of your scripts then you are telling your system to use bash as a default shell.

Now coming to your second question :Is there a difference between #!/bin/bash and #!/bin/sh ?

The answer is Yes. When you tell #!/bin/bash then you are telling your environment/ os to use bash as a command interpreter. This is hard coded thing.

Every system has its own shell which the system will use to execute its own system scripts. This system shell can be vary from OS to OS(most of the time it will be bash. Ubuntu recently using dash as default system shell). When you specify #!/bin/sh then system will use it's internal system shell to interpreting your shell scripts.

Visit this link for further information where I have explained this topic.

Hope this will eliminate your confusions...good luck.

Default value in Doctrine

If you use yaml definition for your entity, the following works for me on a postgresql database:

    type: entity
    table: table_name
            type: boolean
            nullable: false
                default: false

NSRange from Swift Range?

My solution is a string extension that first gets the swift range then get's the distance from the start of the string to the start and end of the substring.

These values are then used to calculate the start and length of the substring. We can then apply these values to the NSMakeRange constructor.

This solution works with substrings that consist of multiple words, which a lot of the solutions here using enumerateSubstrings let me down on.

extension String {

    func NSRange(of substring: String) -> NSRange? {
        // Get the swift range 
        guard let range = range(of: substring) else { return nil }

        // Get the distance to the start of the substring
        let start = distance(from: startIndex, to: range.lowerBound) as Int
        //Get the distance to the end of the substring
        let end = distance(from: startIndex, to: range.upperBound) as Int

        //length = endOfSubstring - startOfSubstring
        //start = startOfSubstring
        return NSMakeRange(start, end - start)


Convert char array to single int?

I'll just leave this here for people interested in an implementation with no dependencies.

inline int
stringLength (char *String)
    int Count = 0;
    while (*String ++) ++ Count;
    return Count;

inline int
stringToInt (char *String)
    int Integer = 0;
    int Length = stringLength(String);
    for (int Caret = Length - 1, Digit = 1; Caret >= 0; -- Caret, Digit *= 10)
        if (String[Caret] == '-') return Integer * -1;
        Integer += (String[Caret] - '0') * Digit;

    return Integer;

Works with negative values, but can't handle non-numeric characters mixed in between (should be easy to add though). Integers only.

How to make an AlertDialog in Flutter?

If you want beautiful and responsive alert dialog then you can use flutter packages like

rflutter alert ,fancy dialog,rich alert,sweet alert dialogs,easy dialog & easy alert

These alerts are good looking and responsive. Among them rflutter alert is the best. currently I am using rflutter alert for my apps.

Date / Timestamp to record when a record was added to the table?

you can use DateAdd on a trigger or a computed column if the timestamp you are adding is fixed or dependent of another column

Keep overflow div scrolled to bottom unless user scrolls up

I managed to get this working. The trick is to calculate: (a) current div user scroll position and (b) div scroll height, both BEFORE appending the new element.

If a === b, we know the user is at the bottom before appending the new element.

    let div = document.querySelector('div.scrollableBox');

    let span = document.createElement('span');
    span.textContent = 'Hello';

    let divCurrentUserScrollPosition = div.scrollTop + div.offsetHeight;
    let divScrollHeight = div.scrollHeight;

    // We have the current scroll positions saved in
    // variables, so now we can append the new element.

    if ((divScrollHeight === divCurrentUserScrollPosition)) {
        // Scroll to bottom of div
        div.scrollTo({ left: 0, top: div.scrollHeight });

Checking whether a variable is an integer or not

import numpy as np

if (np.floor(x)-x == 0):
  return "this is an int"

How to select multiple rows filled with constants?

The following bare VALUES command works for me in PostgreSQL:

VALUES (1,2,3), (4,5,6), (7,8,9)

Fatal error: Class 'ZipArchive' not found in

If you are running into this error while using a Docker image and that you are calling the class properly, or that the error comes from an up-to-date library, then the zip module is probably missing.

Assuming we use docker-compose, we can confirm it's missing by running docker-compose run php php -m for instance and see that zip is not listed.

To install it in your image, modify your Dockerfile so it does the same as this example.

FROM php:7.3-apache 

RUN set -eux \
    && apt-get update \
    && apt-get install -y libzip-dev zlib1g-dev \
    && docker-php-ext-install zip

Then rebuild the image with docker-compose build php and you are good to go.

Export P7b file with all the certificate chain into CER file

The selected answer didn't work for me, but it's close. I found a tutorial that worked for me and the certificate I obtained from StartCom.

  1. Open the .p7b in a text editor.
  2. Change the leader and trailer so the file looks similar to this:

    -----BEGIN PKCS7-----
    [... certificate content here ...]
    -----END PKCS7-----

For example, my StartCom certificate began with:

    -----BEGIN CERTIFICATE----- 

and ended with:

    -----END CERTIFICATE----- 
  1. Save and close the .p7b.
  2. Run the following OpenSSL command (works on Ubuntu 14.04.4, as of this writing):

    openssl pkcs7 -print_certs –in pkcs7.p7b -out pem.cer

The output is a .cer with the certificate chain.


How to read HDF5 files in Python

you can use Pandas.

import pandas as pd

Tuples( or arrays ) as Dictionary keys in C#

Between tuple and nested dictionaries based approaches, it's almost always better to go for tuple based.

From maintainability point of view,

  • its much easier to implement a functionality that looks like:

    var myDict = new Dictionary<Tuple<TypeA, TypeB, TypeC>, string>();


    var myDict = new Dictionary<TypeA, Dictionary<TypeB, Dictionary<TypeC, string>>>();

    from the callee side. In the second case each addition, lookup, removal etc require action on more than one dictionary.

  • Furthermore, if your composite key require one more (or less) field in future, you will need to change code a significant lot in the second case (nested dictionary) since you have to add further nested dictionaries and subsequent checks.

From performance perspective, the best conclusion you can reach is by measuring it yourself. But there are a few theoretical limitations which you can consider beforehand:

  • In the nested dictionary case, having an additional dictionary for every keys (outer and inner) will have some memory overhead (more than what creating a tuple would have).

  • In the nested dictionary case, every basic action like addition, updation, lookup, removal etc need to be carried out in two dictionaries. Now there is a case where nested dictionary approach can be faster, i.e., when the data being looked up is absent, since the intermediate dictionaries can bypass the full hash code computation & comparison, but then again it should be timed to be sure. In presence of data, it should be slower since lookups should be performed twice (or thrice depending on nesting).

  • Regarding tuple approach, .NET tuples are not the most performant when they're meant to be used as keys in sets since its Equals and GetHashCode implementation causes boxing for value types.

I would go with tuple based dictionary, but if I want more performance, I would use my own tuple with better implementation.

On a side note, few cosmetics can make the dictionary cool:

  1. Indexer style calls can be a lot cleaner and intuitive. For eg,

    string foo = dict[a, b, c]; //lookup
    dict[a, b, c] = ""; //update/insertion

    So expose necessary indexers in your dictionary class which internally handles the insertions and lookups.

  2. Also, implement a suitable IEnumerable interface and provide an Add(TypeA, TypeB, TypeC, string) method which would give you collection initializer syntax, like:

    new MultiKeyDictionary<TypeA, TypeB, TypeC, string> 
        { a, b, c, null },