Programs & Examples On #Principles

what is an illegal reflective access

Just look at setAccessible() method used to access private fields and methods:

Now there is a lot more conditions required for this method to work. The only reason it doesn't break almost all of older software is that modules autogenerated from plain JARs are very permissive (open and export everything for everyone).

AngularJS: No "Access-Control-Allow-Origin" header is present on the requested resource

This is a server side issue. You don't need to add any headers in angular for cors. You need to add header on the server side:

Access-Control-Allow-Headers: Content-Type
Access-Control-Allow-Methods: GET, POST, OPTIONS
Access-Control-Allow-Origin: *

First two answers here: How to enable CORS in AngularJs

How many bits is a "word"?

I'm not familiar with either of these books, but the second is closer to current reality. The first may be discussing a specific processor.

Processors have been made with quite a variety of word sizes, not always a multiple of 8.

The 8086 and 8087 processors used 16 bit words, and it's likely this is the machine the first author was writing about.

More recent processors commonly use 32 or 64 bit words.

In the 50's and 60's there were machines with words sizes that seem quite strange to us now, such as 4, 9 and 36. Since about the 70's word size has commonly been a power of 2 and a multiple of 8.

Running multiple async tasks and waiting for them all to complete

Both answers didn't mention the awaitable Task.WhenAll:

var task1 = DoWorkAsync();
var task2 = DoMoreWorkAsync();

await Task.WhenAll(task1, task2);

The main difference between Task.WaitAll and Task.WhenAll is that the former will block (similar to using Wait on a single task) while the latter will not and can be awaited, yielding control back to the caller until all tasks finish.

More so, exception handling differs:


At least one of the Task instances was canceled -or- an exception was thrown during the execution of at least one of the Task instances. If a task was canceled, the AggregateException contains an OperationCanceledException in its InnerExceptions collection.


If any of the supplied tasks completes in a faulted state, the returned task will also complete in a Faulted state, where its exceptions will contain the aggregation of the set of unwrapped exceptions from each of the supplied tasks.

If none of the supplied tasks faulted but at least one of them was canceled, the returned task will end in the Canceled state.

If none of the tasks faulted and none of the tasks were canceled, the resulting task will end in the RanToCompletion state. If the supplied array/enumerable contains no tasks, the returned task will immediately transition to a RanToCompletion state before it's returned to the caller.

Best approach to real time http streaming to HTML5 video client

How about use jpeg solution, just let server distribute jpeg one by one to browser, then use canvas element to draw these jpegs?

How do I integrate Ajax with Django applications?

Easy ajax calls with Django

This is in my opinion much cleaner and simpler than the correct answer. This one also includes how to add the csrftoken and using login_required methods with ajax.

The view

def some_view(request):
    """Returns a json response to an ajax call. (request.user is available in view)"""
    # Fetch the attributes from the request body
    data_attribute = request.GET.get('some_attribute')  # Make sure to use POST/GET correctly
    return JsonResponse(data={}, status=200)

urlpatterns = [
    path('some-view-does-something/', views.some_view, name='doing-something'),

The ajax call

The ajax call is quite simple, but is sufficient for most cases. You can fetch some values and put them in the data object, then in the view depicted above you can fetch their values again via their names.

You can find the csrftoken function in django's documentation. Basically just copy it and make sure it is rendered before your ajax call so that the csrftoken variable is defined.

    url: "{% url 'doing-something' %}",
    headers: {'X-CSRFToken': csrftoken},
    data: {'some_attribute': some_value},
    type: "GET",
    dataType: 'json',
    success: function (data) {
        if (data) {
            // call function to do something with data

Add HTML to current page with ajax

This might be a bit off topic but I have rarely seen this used and it is a great way to minimize window relocations as well as manual html string creation in javascript.

This is very similar to the one above but this time we are rendering html from the response without reloading the current window.

If you intended to render some kind of html from the data you would receive as a response to the ajax call, it might be easier to send a HttpResponse back from the view instead of a JsonResponse. That allows you to create html easily which can then be inserted into an element.

The view

# The login required part is of course optional
def create_some_html(request):
    """In this particular example we are filtering some model by a constraint sent in by 
    ajax and creating html to send back for those models who match the search"""
    # Fetch the attributes from the request body (sent in ajax data)
    search_input = request.GET.get('search_input')

    # Get some data that we want to render to the template
    if search_input:
        data = MyModel.objects.filter(name__contains=search_input) # Example
        data = []

    # Creating an html string using template and some data
    html_response = render_to_string('path/to/creation_template.html', context = {'models': data})

    return HttpResponse(html_response, status=200)

The html creation template for view


{% for model in models %}
   <li class="xyz">{{ }}</li>
{% endfor %}

urlpatterns = [
    path('get-html/', views.create_some_html, name='get-html'),

The main template and ajax call

This is the template where we want to add the data to. In this example in particular we have a search input and a button that sends the search input's value to the view. The view then sends a HttpResponse back displaying data matching the search that we can render inside an element.

{% extends 'base.html' %}
{% load static %}
{% block content %}
    <input id="search-input" placeholder="Type something..." value="">
    <button id="add-html-button" class="btn btn-primary">Add Html</button>
    <ul id="add-html-here">
        <!-- This is where we want to render new html -->
{% end block %}

{% block extra_js %}
        // When button is pressed fetch inner html of ul
        $("#add-html-button").on('click', function (e){
            let search_input = $('#search-input').val();
            let target_element = $('#add-html-here');
                url: "{% url 'get-html' %}",
                headers: {'X-CSRFToken': csrftoken},
                data: {'search_input': search_input},
                type: "GET",
                dataType: 'html',
                success: function (data) {
                    if (data) {
                        // Add the http response to element
{% endblock %}

Simple JavaScript Checkbox Validation

You could use:

    alert('You must agree to the terms first.');
    return false;

(demo page).

<input type="checkbox" name="checkbox" value="check"  />
<input type="submit" name="email_submit" value="submit" onclick="if(!this.form.checkbox.checked){alert('You must agree to the terms first.');return false}"  />
  • Returning false from an inline event handler will prevent the default action from taking place (in this case, submitting the form).
  • ! is the Boolean NOT operator.
  • this is the submit button because it is the element the event handler is attached to.
  • .form is the form the submit button is in.
  • .checkbox is the control named "checkbox" in that form.
  • .checked is true if the checkbox is checked and false if the checkbox is unchecked.

RESTful web service - how to authenticate requests from other services?

After reading your question, I would say, generate special token to do request required. This token will live in specific time (lets say in one day).

Here is an example from to generate authentication token:

(day * 10) + (month * 100) + (year (last 2 digits) * 1000)

for example: 3 June 2011

(3 * 10) + (6 * 100) + (11 * 1000) = 
30 + 600 + 11000 = 11630

then concatenate with user password, example "my4wesomeP4ssword!"


Then do MD5 of that string:


When do you call a request, always use this token,

This token is always unique everyday, so I guess this kind of protection is more than sufficient to always protect ur service.

Hope helps


Runnable with a parameter?

Since Java 8, the best answer is to use Consumer<T>:

It's one of the functional interfaces, which means you can call it as a lambda expression:

void doSomething(Consumer<String> something) {


doSomething( (something) -> System.out.println(something) )


Why would one use nested classes in C++?

Nested classes are just like regular classes, but:

  • they have additional access restriction (as all definitions inside a class definition do),
  • they don't pollute the given namespace, e.g. global namespace. If you feel that class B is so deeply connected to class A, but the objects of A and B are not necessarily related, then you might want the class B to be only accessible via scoping the A class (it would be referred to as A::Class).

Some examples:

Publicly nesting class to put it in a scope of relevant class

Assume you want to have a class SomeSpecificCollection which would aggregate objects of class Element. You can then either:

  1. declare two classes: SomeSpecificCollection and Element - bad, because the name "Element" is general enough in order to cause a possible name clash

  2. introduce a namespace someSpecificCollection and declare classes someSpecificCollection::Collection and someSpecificCollection::Element. No risk of name clash, but can it get any more verbose?

  3. declare two global classes SomeSpecificCollection and SomeSpecificCollectionElement - which has minor drawbacks, but is probably OK.

  4. declare global class SomeSpecificCollection and class Element as its nested class. Then:

    • you don't risk any name clashes as Element is not in the global namespace,
    • in implementation of SomeSpecificCollection you refer to just Element, and everywhere else as SomeSpecificCollection::Element - which looks +- the same as 3., but more clear
    • it gets plain simple that it's "an element of a specific collection", not "a specific element of a collection"
    • it is visible that SomeSpecificCollection is also a class.

In my opinion, the last variant is definitely the most intuitive and hence best design.

Let me stress - It's not a big difference from making two global classes with more verbose names. It just a tiny little detail, but imho it makes the code more clear.

Introducing another scope inside a class scope

This is especially useful for introducing typedefs or enums. I'll just post a code example here:

class Product {
    enum ProductType {
    enum ProductBoxType {
        BOX, BAG, CRATE
    Product(ProductType t, ProductBoxType b, String name);

    // the rest of the class: fields, methods

One then will call:

Product p(Product::FANCY, Product::BOX);

But when looking at code completion proposals for Product::, one will often get all the possible enum values (BOX, FANCY, CRATE) listed and it's easy to make a mistake here (C++0x's strongly typed enums kind of solve that, but never mind).

But if you introduce additional scope for those enums using nested classes, things could look like:

class Product {
    struct ProductType {
        enum Enum { FANCY, AWESOME, USEFUL };
    struct ProductBoxType {
        enum Enum { BOX, BAG, CRATE };
    Product(ProductType::Enum t, ProductBoxType::Enum b, String name);

    // the rest of the class: fields, methods

Then the call looks like:

Product p(Product::ProductType::FANCY, Product::ProductBoxType::BOX);

Then by typing Product::ProductType:: in an IDE, one will get only the enums from the desired scope suggested. This also reduces the risk of making a mistake.

Of course this may not be needed for small classes, but if one has a lot of enums, then it makes things easier for the client programmers.

In the same way, you could "organise" a big bunch of typedefs in a template, if you ever had the need to. It's a useful pattern sometimes.

The PIMPL idiom

The PIMPL (short for Pointer to IMPLementation) is an idiom useful to remove the implementation details of a class from the header. This reduces the need of recompiling classes depending on the class' header whenever the "implementation" part of the header changes.

It's usually implemented using a nested class:


class X {
    virtual ~X();
    void publicInterface();
    void publicInterface2();
    struct Impl;
    std::unique_ptr<Impl> impl;


#include "X.h"
#include <windows.h>

struct X::Impl {
    HWND hWnd; // this field is a part of the class, but no need to include windows.h in header
    // all private fields, methods go here

    void privateMethod(HWND wnd);
    void privateMethod();

X::X() : impl(new Impl()) {
    // ...

// and the rest of definitions go here

This is particularly useful if the full class definition needs the definition of types from some external library which has a heavy or just ugly header file (take WinAPI). If you use PIMPL, then you can enclose any WinAPI-specific functionality only in .cpp and never include it in .h.

REST, HTTP DELETE and parameters

In addition to Alex's answer:

Note that http://server/resource/id?force_delete=true identifies a different resource than http://server/resource/id. For example, it is a huge difference whether you delete /customers/?status=old or /customers/.

How to calculate modulus of large numbers?

5^55 mod221

= (   5^10         * 5^10         * 5^10         * 5^10          * 5^10          * 5^5) mod221    

= ( ( 5^10) mod221 * 5^10         * 5^10         * 5^10          * 5^10          * 5^5) mod221 

= (   77           * 5^10         * 5^10         * 5^10          * 5^10          * 5^5) mod221   

= ( ( 77           * 5^10) mod221 * 5^10         * 5^10          * 5^10          * 5^5) mod221 

= (   183                         * 5^10         * 5^10          * 5^10          * 5^5) mod221 

= ( ( 183                         * 5^10) mod221 * 5^10          * 5^10          * 5^5) mod221 

= (   168                                        * 5^10          * 5^10          * 5^5) mod221 

= ( ( 168                                        * 5^10) mod 221 * 5^10          * 5^5) mod221 

= (   118                                                        * 5^10          * 5^5) mod221 

= ( ( 118                                                        * 5^10) mod 221 * 5^5) mod221 

= (   25                                                                         * 5^5) mod221 

=     112

Understanding REST: Verbs, error codes, and authentication

I would suggest (as a first pass) that PUT should only be used for updating existing entities. POST should be used for creating new ones. i.e.

/api/users     when called with PUT, creates user record

doesn't feel right to me. The rest of your first section (re. verb usage) looks logical, however.

What does Ruby have that Python doesn't, and vice versa?

Syntax is not a minor thing, it has a direct impact on how we think. It also has a direct effect on the rules we create for the systems we use. As an example we have the order of operations because of the way we write mathematical equations or sentences. The standard notation for mathematics allows people to read it more than one way and arrive at different answers given the same equation. If we had used prefix or postfix notation we would have created rules to distinguish what the numbers to be manipulated were rather than only having rules for the order in which to compute values.

The standard notation makes it plain what numbers we are talking about while making the order in which to compute them ambiguous. Prefix and postfix notation make the order in which to compute plain while making the numbers ambiguous. Python would already have multiline lambdas if it were not for the difficulties caused by the syntactic whitespace. (Proposals do exist for pulling this kind of thing off without necessarily adding explicit block delimiters.)

I find it easier to write conditions where I want something to occur if a condition is false much easier to write with the unless statement in Ruby than the semantically equivalent "if-not" construction in Ruby or other languages for example. If most of the languages that people are using today are equal in power, how can the syntax of each language be considered a trivial thing? After specific features like blocks and inheritance mechanisms etc. syntax is the most important part of a language,hardly a superficial thing.

What is superficial are the aesthetic qualities of beauty that we ascribe to syntax. Aesthetics have nothing to do with how our cognition works, syntax does.

Why can't decimal numbers be represented exactly in binary?

To repeat what I said in my comment to Mr. Skeet: we can represent 1/3, 1/9, 1/27, or any rational in decimal notation. We do it by adding an extra symbol. For example, a line over the digits that repeat in the decimal expansion of the number. What we need to represent decimal numbers as a sequence of binary numbers are 1) a sequence of binary numbers, 2) a radix point, and 3) some other symbol to indicate the repeating part of the sequence.

Hehner's quote notation is a way of doing this. He uses a quote symbol to represent the repeating part of the sequence. The article: and the Wikipedia entry:

There's nothing that says we can't add a symbol to our representation system, so we can represent decimal rationals exactly using binary quote notation, and vice versa.

When to use IMG vs. CSS background-image?

You can use IMG tags if you want the images to be fluid and scale to different screen sizes. For me these images are mostly part of the content. For most elements that are not part of the content, I use CSS sprites to keep the download size minimal unless I really want to animate icons etc.

Default string initialization: NULL or Empty?

This is actually a gaping hole in the C# language. There is no way to define a string that cannot be null. This causes problems as simple as the one you are describing, which forces programmers to make a decision they shouldn't have to make, since in many cases NULL and String.Empty mean the same thing. That, in turn, can later force other programmers to have to handle both NULL and String.Empty, which is annoying.

A bigger problem is that databases allow you to define fields that map to a C# string, but database fields can be defined as NOT NULL. So, there is no way to accurately represent, say, a varchar( 100 ) NOT NULL field in SQL Server using a C# type.

Other languages, such as Spec #, do allow this.

In my opinion, C#'s inability to define a string that doesn't allow null is just as bad as its previous inability to define an int that does allow null.

To completely answer your question: I always use empty string for default initialization because it is more similar to how database data types work. (Edit: This statement was very unclear. It should read "I use empty string for default initialization when NULL is a superfluous state, much in the same way I set up a database column as NOT NULL if NULL would be a superfluous state. Similarly, many of my DB columns are set up as NOT NULL, so when I bring those into a C# string, the string will be empty or have a value, but will never be NULL. In other words, I only initialize a string to NULL if null has a meaning that is distinct from the meaning of String.Empty, and I find that case to be less than common (but people here have given legitimate examples of this case).")

What's wrong with foreign keys?

From my experience its always better to avoid using FKs in Database Critical Applications. I would not disagree with guys here who say FKs is a good practice but its not practical where the database is huge and has huge CRUD operations/sec. I can share without naming ... one of the biggest investment bank of doesn't have a single FK in databases. These constrains are handled by programmers while creating applications involving DB. The basic reason is when ever a new CRUD is done it has to effect multiple tables and verify for each inserts/updates, though this won't be a big issue for queries affecting single rows but it does create a huge latency when you deal with batch processing which any big bank has to do as daily tasks.

Its better to avoid FKs but its risk has to be handled by programmers.

What is reflection and why is it useful?

Reflection has many uses. The one I am more familiar with, is to be able to create code on the fly.

IE: dynamic classes, functions, constructors - based on any data (xml/array/sql results/hardcoded/etc..)

Language Books/Tutorials for popular languages

The reference you have listed for Ruby is for Ruby on Rails. While still ruby deep down, it is definitely not a place to start for people wanting to learn Ruby.

For Ruby tutorials, I would suggest Why's (Poignant) Guide to Ruby as a great starting point for anyone interested in the language.

If you would want to get into more detail, I would recommend the book Programming Ruby, which has become the standard for all things Ruby. The third edition is currently being written, highlighting Ruby 1.9 features, so I would hold off for a while if anyone is considering buying this book.

How to fix curl: (60) SSL certificate: Invalid certificate chain

The problem is an expired intermediate certificate that is no longer used and must be deleted. Here is a blog post from Digicert explaining the issue and how to resolve it.

I was seeing the issue with Github not loading via SSL in both Safari and the command line with git pull. Once I deleted the old expired cert everything was fine.

How to prevent multiple definitions in C?

Including the implementation file (test.c) causes it to be prepended to your main.c and complied there and then again separately. So, the function test has two definitions -- one in the object code of main.c and once in that of test.c, which gives you a ODR violation. You need to create a header file containing the declaration of test and include it in main.c:

/* test.h */
#ifndef TEST_H
#define TEST_H
void test(); /* declaration */
#endif /* TEST_H */

sorting a vector of structs

Use a comparison function:

bool compareByLength(const data &a, const data &b)
    return a.word.size() < b.word.size();

and then use std::sort in the header #include <algorithm>:

std::sort(info.begin(), info.end(), compareByLength);

How to get IP address of the device from code?

I don't do Android, but I'd tackle this in a totally different way.

Send a query to Google, something like:

And refer to the HTML field where the response is posted. You may also query directly to the source.

Google will most like be there for longer than your Application.

Just remember, it could be that your user does not have internet at this time, what would you like to happen !

Good Luck

Docker-Compose can't connect to Docker Daemon

For me the fix was to install a newer version (1.24) of docker-compose using this article.

The previous version (1.17) was installed from ubuntu's default repository, but after installing a newer version I managed to launch the container. Hope it helps somebody.

Learning to write a compiler

The quickest approach is through two books:

1990 version of An Introduction to Compiling Techniques, a First Course using ANSI C, LeX, and YaCC by JP Bennett - a perfect balance of example code, parsing theory and design- it contains a complete compiler written in C, lex and yacc for a simple grammar

Dragon Book (older version) - mostly a detailed reference for the features not covered in the former book

Spring MVC - HttpMediaTypeNotAcceptableException

Make sure you add both Jackson jars to classpath:

  • jackson-core-asl-x.jar
  • jackson-mapper-asl-x.jar

Also, you must have the following in your Spring xml file:

<mvc:annotation-driven />

Is there a way to 'uniq' by column?

To consider multiple column.

Sort and give unique list based on column 1 and column 3:

sort -u -t : -k 1,1 -k 3,3 test.txt
  • -t : colon is separator
  • -k 1,1 -k 3,3 based on column 1 and column 3

How to use makefiles in Visual Studio?

If you are asking about actual command line makefiles then you can export a makefile, or you can call MSBuild on a solution file from the command line. What exactly do you want to do with the makefile?

You can do a search on SO for MSBuild for more details.

Updating GUI (WPF) using a different thread

You may use a delegate to solve this issue. Here is an example that is showing how to update a textBox using diffrent thread

public delegate void UpdateTextCallback(string message);

private void TestThread()
    for (int i = 0; i <= 1000000000; i++)
            new UpdateTextCallback(this.UpdateText),
            new object[] { i.ToString() }
private void UpdateText(string message)
    richTextBox1.AppendText(message + "\n");

private void button1_Click(object sender, RoutedEventArgs e)
   Thread test = new Thread(new ThreadStart(TestThread));

TestThread method is used by thread named test to update textBox

Git Pull While Ignoring Local Changes?


"Adding unwanted files to .gitignore works as long as you have not initially committed them to any branch. "

Also you can run:

git update-index --assume-unchanged filename

Revert to Eclipse default settings

To me the first answer by Rikus Khan was almost what I needed. It wasn't enough to go to ,e.g. General > Editors > Text editors and click Restore Defaults. I had to choose every single subcategory, namely: Accessibility, Annotations, Hyperlinking, etc., and manually restore their defaults as well. Apparently restoring defaults doesn't propagate down the tree.

The problem I had was the underscoring of warnings and errors in Java editor changed to highliting (after importing RainbowDrops.epf, recommended by the MoonRise UI Theme) and didn't want to revert when changing syntax coloring and other related options. This option itself is located in the aforementioned Annotations > Errors and Warnings.

How to programmatically log out from Facebook SDK 3.0 without using Facebook login/logout button?

This method will help you to logout from facebook programmatically in android

 * Logout From Facebook 
public static void callFacebookLogout(Context context) {
    Session session = Session.getActiveSession();
    if (session != null) {

        if (!session.isClosed()) {
            //clear your preferences if saved
    } else {

        session = new Session(context);

            //clear your preferences if saved



Removing credits link

Both of the following code will work fine for removing from the chart:-

credits: false



How to host material icons offline?

By the way there is video available on youtube with step by step instructions.

  1. These are the steps. Download materialize icon package from

  2. Copy the icon-font folder and rename it to icons.

  3. Open the materialize.css file and update the following paths:

a. from url(MaterialIcons-Regular.eot) to url(../fonts/MaterialIcons-Regular.eot) b. from url(MaterialIcons-Regular.woff2) format('woff2') to url(../fonts/MaterialIcons-Regular.woff2) format('woff2') c. from url(MaterialIcons-Regular.woff) format('woff') to url(../fonts/MaterialIcons-Regular.woff) format('woff') d. from url(MaterialIcons-Regular.ttf) format('truetype') to url(../fonts/MaterialIcons-Regular.ttf) format('truetype')

  1. Copy the materialize-icon.css to your css folder and reference it in your html file.

Everything will work like magic !

ClassNotFoundException com.mysql.jdbc.Driver

I keep the mysql-connector jar with my project rather than in Javahome. As a result, you can be sure it can be found by being sure its in the local classpath. A big upside is that you you can more the project to another machine and not have to worry about (or forget) to set this up again. I personally like including it in version control.

ComboBox SelectedItem vs SelectedValue

The ComboBox control inherits from the ListControl control.

The SelectedItem property is a proper member of the ComboBox control. The event that is fired on change is ComboBox.SelectionChangeCommitted


Occurs when the selected item has changed and that change is displayed in the ComboBox.

The SelectedValue property is inherited from the ListControl control. As such, this property will fire the ListControl.SelectedValueChanged event.


Occurs when the SelectedValue property changes.

That said, they won't fire the INotifyPropertyChanged.PropertyChanged event the same, but they will anyway. The only difference is in the firing event. SelectedValueChanged is fired as soon as a new selection is made from the list part of the ComboBox, and SelectedItemChanged is fired when the item is displayed in the TextBox portion of the ComboBox.

In short, they both represent something in the list part of the ComboBox. So, when binding either property, the result is the same, since the PropertyChanged event is fired in either case. And since they both represent an element from the list, the they are probably treated the same.

Does this help?


Assuming that the list part of the ComboBox represents a property (as I can't confirm since I didn't write the control), binding either of SelectedItem or SelectedValue affects the same collection inside the control. Then, when this property is changed, the same occurs in the end. The INotifyPropertryPropertyChanged.PropertyChanged event is fired on the same property.

In jQuery, how do I get the value of a radio button when they all have the same name?

There is another way also. Try below code


      $("input[name='gender']").on("click", function() {

LINQ syntax where string value is not null or empty

This won't fail on Linq2Objects, but it will fail for Linq2SQL, so I am assuming that you are talking about the SQL provider or something similar.

The reason has to do with the way that the SQL provider handles your lambda expression. It doesn't take it as a function Func<P,T>, but an expression Expression<Func<P,T>>. It takes that expression tree and translates it so an actual SQL statement, which it sends off to the server.

The translator knows how to handle basic operators, but it doesn't know how to handle methods on objects. It doesn't know that IsNullOrEmpty(x) translates to return x == null || x == string.empty. That has to be done explicitly for the translation to SQL to take place.

Play multiple CSS animations at the same time

You can indeed run multiple animations simultaneously, but your example has two problems. First, the syntax you use only specifies one animation. The second style rule hides the first. You can specify two animations using syntax like this:

-webkit-animation-name: spin, scale
-webkit-animation-duration: 2s, 4s

as in this fiddle (where I replaced "scale" with "fade" due to the other problem explained below... Bear with me.):

Second, both of your animations alter the same CSS property (transform) of the same DOM element. I don't believe you can do that. You can specify two animations on different elements, the image and a container element perhaps. Just apply one of the animations to the container, as in this fiddle:

How do you make a LinearLayout scrollable?

you need to use the following attribute and enclose it within the linear layout

<LinearLayout ...>
<scrollView ...> 


How to convert string to float?

Use atof() or strtof()* instead:

printf("float value : %4.8f\n" ,atof(s)); 
printf("float value : %4.8f\n" ,strtof(s, NULL));

  • atoll() is meant for integers.
  • atof()/strtof() is for floats.

The reason why you only get 4.00 with atoll() is because it stops parsing when it finds the first non-digit.

*Note that strtof() requires C99 or C++11.

VBA for clear value in specific range of cell and protected cell from being wash away formula

Try this

Sheets("your sheetname").range("A5:X50").Value = ""

You can also use


How do I increase the cell width of the Jupyter/ipython notebook in my browser?

To get this to work with jupyter (version 4.0.6) I created ~/.jupyter/custom/custom.css containing:

/* Make the notebook cells take almost all available width */
.container {
    width: 99% !important;

/* Prevent the edit cell highlight box from getting clipped;
 * important so that it also works when cell is in edit mode*/
div.cell.selected {
    border-left-width: 1px !important;

TypeError: unsupported operand type(s) for /: 'str' and 'str'

I would have written:

percent = 100
while True:
        pyc = int(input('enter pyc :'))
        tpy = int(input('enter tpy:'))
        percent = (pyc / tpy) * percent
     except ZeroDivisionError as detail:
        print 'Handling run-time error:', detail

SQL SELECT multi-columns INTO multi-variable

SELECT @var = col1,
       @var2 = col2
FROM   Table

Here is some interesting information about SET / SELECT

  • SET is the ANSI standard for variable assignment, SELECT is not.
  • SET can only assign one variable at a time, SELECT can make multiple assignments at once.
  • If assigning from a query, SET can only assign a scalar value. If the query returns multiple values/rows then SET will raise an error. SELECT will assign one of the values to the variable and hide the fact that multiple values were returned (so you'd likely never know why something was going wrong elsewhere - have fun troubleshooting that one)
  • When assigning from a query if there is no value returned then SET will assign NULL, where SELECT will not make the assignment at all (so the variable will not be changed from it's previous value)
  • As far as speed differences - there are no direct differences between SET and SELECT. However SELECT's ability to make multiple assignments in one shot does give it a slight speed advantage over SET.

Wrapping text inside input type="text" element HTML/CSS

That is the textarea's job - for multiline text input. The input won't do it; it wasn't designed to do it.

So use a textarea. Besides their visual differences, they are accessed via JavaScript the same way (use value property).

You can prevent newlines being entered via the input event and simply using a replace(/\n/g, '').

SVN remains in conflict?

I guess the proper solution is:

(1) backup your-file/your-directory
(2) svn revert your-file/your-directory
(3) svn update your-file/your-directory
(4) Merge the backup your-file/your-directory to the updated one.
(5) svn ci -m "My work here is done"

Disable building workspace process in Eclipse

Building workspace is about incremental build of any evolution detected in one of the opened projects in the currently used workspace.

You can also disable it through the menu "Project / Build automatically".

But I would recommend first to check:

  • if a Project Clean all / Build result in the same kind of long wait (after disabling this option)
  • if you have (this time with building automatically activated) some validation options you could disable to see if they have an influence on the global compilation time (Preferences / Validations, or Preferences / XML / ... if you have WTP installed)
  • if a fresh eclipse installation referencing the same workspace (see this eclipse.ini for more) results in the same issue (with building automatically activated)

Note that bug 329657 (open in 2011, in progress in 2014) is about interrupting a (too lengthy) build, instead of cancelling it:

There is an important difference between build interrupt and cancel.

  • When a build is cancelled, it typically handles this by discarding incremental build state and letting the next build be a full rebuild. This can be quite expensive in some projects.
    As a user I think I would rather wait for the 5 second incremental build to finish rather than cancel and result in a 30 second rebuild afterwards.

  • The idea with interrupt is that a builder could more efficiently handle interrupt by saving its intermediate state and resuming on the next invocation.
    In practice this is hard to implement so the most common boundary is when we check for interrupt before/after calling each builder in the chain.


awk - concatenate two string variable and assign to a third

Concatenating strings in awk can be accomplished by the print command AWK manual page, and you can do complicated combination. Here I was trying to change the 16 char to A and used string concatenation:

echo    CTCTCTGAAATCACTGAGCAGGAGAAAGATT | awk -v w=15 -v BA=A '{OFS=""; print substr($0, 1, w), BA, substr($0,w+2)}'

I used the substr function to extract a portion of the input (STDIN). I passed some external parameters (here I am using hard-coded values) that are usually shell variable. In the context of shell programming, you can write -v w=$width -v BA=$my_charval. The key is the OFS which stands for Output Field Separate in awk. Print function take a list of values and write them to the STDOUT and glue them with the OFS. This is analogous to the perl join function.

It looks that in awk, string can be concatenated by printing variable next to each other:

echo xxx | awk -v a="aaa" -v b="bbb" '{ print a b $1 "string literal"}'
# will produce: aaabbbxxxstring literal

Python Image Library fails with message "decoder JPEG not available" - PIL

For those on Mac OS Mountain Lion, I followed the anwser of zeantsoi, but it doesn't work.

I finally ended up with the solution of this post:

Now, I'm happily running my script for jpeg !

How to select specific form element in jQuery?

It isn't valid to have the same ID twice, that's why #name only finds the first one.

You can try:

$("#form2 input").val('Hello World!');


$("#form2 input[name=name]").val('Hello World!');

If you're stuck with an invalid page and want to select all #names, you can use the attribute selector on the id:

$("input[id=name]").val('Hello World!');

Difference between Hive internal tables and external tables?

Hive has a relational database on the master node it uses to keep track of state. For instance, when you CREATE TABLE FOO(foo string) LOCATION 'hdfs://tmp/';, this table schema is stored in the database.

If you have a partitioned table, the partitions are stored in the database(this allows hive to use lists of partitions without going to the file-system and finding them, etc). These sorts of things are the 'metadata'.

When you drop an internal table, it drops the data, and it also drops the metadata.

When you drop an external table, it only drops the meta data. That means hive is ignorant of that data now. It does not touch the data itself.

How to handle a single quote in Oracle SQL

Use two single-quotes



Alternatively, use the new (10g+) quoting method:



How to find the serial port number on Mac OS X?

You can find your Arduino via Terminal with

 ls /dev/tty.*

then you can read that serial port using the screen command, like this

screen /dev/tty.[yourSerialPortName] [yourBaudRate]

for example:

screen /dev/tty.usbserial-A6004byf 9600

How to check "hasRole" in Java Code with Spring Security?

Spring Security 3.0 has this API

SecurityContextHolderAwareRequestWrapper.isUserInRole(String role)

You'll have to inject the wrapper, before you use it.


Get device token for push notification

Using description as many of these answers suggest is the wrong approach - even if you get it to work, it will break in iOS 13+.

Instead you should ensure you use the actual binary data, not simply a description of it. Andrey Gagan addressed the Objective C solution quite well, but fortunately it's much simpler in swift:

Swift 4.2 works in iOS 13+

// credit to NSHipster (see link above)
// format specifier produces a zero-padded, 2-digit hexadecimal representation
let deviceTokenString = { String(format: "%02x", $0) }.joined()

maven error: package org.junit does not exist

if you are using Eclipse watch your POM dependencies and your Eclipse buildpath dependency on junit

if you select use Junit4 eclipse create TestCase using org.junit package but your POM use by default Junit3 (junit.framework package) that is the cause, like this picture:

see JUNIT conflict

Just update your Junit dependency in your POM file to Junit4 or your Eclipse BuildPath to Junit3

How to verify static void method has been called with power mockito

If you are mocking the behavior (with something like doNothing()) there should really be no need to call to verify*(). That said, here's my stab at re-writing your test method:

public class InternalServiceTest { //Note the renaming of the test class.
   public void testProcessOrder() {
        InternalService is = new InternalService();
        Order order = mock(Order.class);

        //Mock Behavior
        doNothing().when(InternalUtils.class); //This is the preferred way
                                               //to mock static void methods.
        InternalUtils.sendEmail(anyString(), anyString(), anyString(), anyString());


        verifyStatic(InternalUtils.class); //Similar to how you mock static methods
                                           //this is how you verify them.
        InternalUtils.sendEmail(anyString(), anyString(), anyString(), anyString());

I grouped into four sections to better highlight what is going on:

1. Variables

I choose to declare any instance variables / method arguments / mock collaborators here. If it is something used in multiple tests, consider making it an instance variable of the test class.

2. Mock Behavior

This is where you define the behavior of all of your mocks. You're setting up return values and expectations here, prior to executing the code under test. Generally speaking, if you set the mock behavior here you wouldn't need to verify the behavior later.

3. Execute

Nothing fancy here; this just kicks off the code being tested. I like to give it its own section to call attention to it.

4. Verify

This is when you call any method starting with verify or assert. After the test is over, you check that the things you wanted to have happen actually did happen. That is the biggest mistake I see with your test method; you attempted to verify the method call before it was ever given a chance to run. Second to that is you never specified which static method you wanted to verify.

Additional Notes

This is mostly personal preference on my part. There is a certain order you need to do things in but within each grouping there is a little wiggle room. This helps me quickly separate out what is happening where.

I also highly recommend going through the examples at the following sites as they are very robust and can help with the majority of the cases you'll need:

How to remove specific element from an array using python

You don't need to iterate the array. Just:

>>> x = ['[email protected]', '[email protected]']
>>> x
['[email protected]', '[email protected]']
>>> x.remove('[email protected]')
>>> x
['[email protected]']

This will remove the first occurence that matches the string.

EDIT: After your edit, you still don't need to iterate over. Just do:

index = initial_list.index(item1)
del initial_list[index]
del other_list[index]

How to decode a Base64 string?

Base64 encoding converts three 8-bit bytes (0-255) into four 6-bit bytes (0-63 aka base64). Each of the four bytes indexes an ASCII string which represents the final output as four 8-bit ASCII characters. The indexed string is typically 'A-Za-z0-9+/' with '=' used as padding. This is why encoded data is 4/3 longer.

Base64 decoding is the inverse process. And as one would expect, the decoded data is 3/4 as long.

While base64 encoding can encode plain text, its real benefit is encoding non-printable characters which may be interpreted by transmitting systems as control characters.

I suggest the original poster render $z as bytes with each bit having meaning to the application. Rendering non-printable characters as text typically invokes Unicode which produces glyphs based on your system's localization.

Base64decode("the answer to life the universe and everything") = 00101010

What is the best way to add options to a select from a JavaScript object with jQuery?

If you don't have to support old IE versions, using the Option constructor is clearly the way to go, a readable and efficient solution:

$(new Option('myText', 'val')).appendTo('#mySelect');

It's equivalent in functionality to, but cleaner than:

$("<option></option>").attr("value", "val").text("myText")).appendTo('#mySelect');

Close pre-existing figures in matplotlib when running from eclipse

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

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

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

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

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

$ kill 12410

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

Exposing the current state name with ui router

I wrapped around $state around $timeout and it worked for me.

For example,

(function() {
  'use strict';

    .controller('BodyController', BodyController);

  BodyController.$inject = ['$state', '$timeout'];

  /* @ngInject */
  function BodyController($state, $timeout) {


How can I get the domain name of my site within a Django template?

If you use the "request" context processor, and are using the Django sites framework, and have the Site middleware installed (i.e. your settings include these):



... then you will have the request object available in templates, and it will contain a reference to the current Site for the request as You can then retrieve the domain in a template with:


and the site name with:


MySQL, create a simple function


and change the following line too.


It should work.

Controller not a function, got undefined, while defining controllers globally

These errors occurred, in my case, preceeded by syntax errors at list.find() fuction; 'find' method of a list not recognized by IE11, so has to replace by Filter method, which works for both IE11 and chrome. refer

What is an MvcHtmlString and when should I use it?

You would use an MvcHtmlString if you want to pass raw HTML to an MVC helper method and you don't want the helper method to encode the HTML.

Force div element to stay in same place, when page is scrolled

Change position:absolute to position:fixed;.

Example can be found in this jsFiddle.

OpenCV & Python - Image too big to display

The other answers perform a fixed (width, height) resize. If you wanted to resize to a specific size while maintaining aspect ratio, use this

def ResizeWithAspectRatio(image, width=None, height=None, inter=cv2.INTER_AREA):
    dim = None
    (h, w) = image.shape[:2]

    if width is None and height is None:
        return image
    if width is None:
        r = height / float(h)
        dim = (int(w * r), height)
        r = width / float(w)
        dim = (width, int(h * r))

    return cv2.resize(image, dim, interpolation=inter)


image = cv2.imread('img.png')
resize = ResizeWithAspectRatio(image, width=1280) # Resize by width OR
# resize = ResizeWithAspectRatio(image, height=1280) # Resize by height 

cv2.imshow('resize', resize)

Git: Permission denied (publickey) fatal - Could not read from remote repository. while cloning Git repository

If you generate new public ssh key and inserted it to bitbucket or github and

it not helped - please try to restart your PC. It helped me!!

How to execute a bash command stored as a string with quotes and asterisk

try this

$ cmd='mysql AMORE -u root --password="password" -h localhost -e "select host from amoreconfig"'
$ eval $cmd

How to get public directory?

The best way to retrieve your public folder path from your Laravel config is the function:

$myPublicFolder = public_path();
$savePath = $mypublicPath."enter_path_to_save";
$path = $savePath."filename.ext";
return File::put($path , $data);

There is no need to have all the variables, but this is just for a demonstrative purpose.

Hope this helps, GRnGC

git replacing LF with CRLF

echo "* -crlf" > .gitattributes 

Do this on a separate commit or git might still see whole files as modified when you make a single change (depending on if you have changed autocrlf option)

This one really works. Git will respect the line endings in mixed line ending projects and not warning you about them.

How to get the current date and time of your timezone in Java?

Here are some steps for finding Time for your zone:

Date now = new Date();

 DateFormat df = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");  


How can I make my website's background transparent without making the content (images & text) transparent too?

You probably want an extra wrapper. use a div for the background and position it below your content..


<div id="background-image"></div>
<div id="content">
    Here is the content at opacity 1
    <img src="">



#background-image {
    background-image: url(;
#content {

MySQL SELECT AS combine two columns into one

In case of NULL columns it is better to use IF clause like this which combine the two functions of : CONCAT and COALESCE and uses special chars between the columns in result like space or '_'

SELECT FirstName , LastName , 
IF(FirstName IS NULL AND LastName IS NULL, NULL,' _ ',CONCAT(COALESCE(FirstName ,''), COALESCE(LastName ,''))) 
AS Contact_Phone FROM   TABLE1

How to connect a Windows Mobile PDA to Windows 10

  1. Install

    • Windows Mobile 6 Professional SDK Refresh
    • Windows Mobile 6 Standard SDK Refresh
    • Windows Mobile 6.5 Professional Developer Tool Kit (USA)
    • Windows Mobile 6.5 Standard Developer Tool Kit (USA)
  2. Control Panel > Programs and Features > Add or remove a Windows component

    • NET Framework 3.5
    • Check HTTP and non HTTP
  3. Reinstall WMDC observing your platform x64/x86

  4. Services.msc > Windows Mobile 2003-based device connectivity

    • Logon > Local System
    • Allow service to interact with desktop
  5. Restart your PC

Laravel Carbon subtract days from current date

Use subDays() method:

$users = Users::where('status_id', 'active')
           ->where( 'created_at', '>', Carbon::now()->subDays(30))

Can't choose class as main class in IntelliJ

The documentation you linked actually has the answer in the link associated with the "Java class located out of the source root." Configure your source and test roots and it should work.

Since you stated that these are tests you should probably go with them marked as Test Source Root instead of Source Root.

How to output git log with the first line only?

If you don't want hashes and just the first lines (subject lines):

git log --pretty=format:%s

Why GDB jumps unpredictably between lines and prints variables as "<value optimized out>"?

Im using QtCreator with gdb.



Works well for me

Execute combine multiple Linux commands in one line

You can use as the following code;

cd /my_folder && \
rm *.jar && \
svn co path to repo && \
mvn compile package install

It works...

Remove CSS class from element with JavaScript (no jQuery)

document.getElementById("whatever").className += "classToKeep";

With the plus sign ('+') appending the class as opposed to overwriting any existing classes

Static methods in Python?

Static methods in Python?

Is it possible to have static methods in Python so I can call them without initializing a class, like:


Yes, static methods can be created like this (although it's a bit more Pythonic to use underscores instead of CamelCase for methods):

class ClassName(object):

    def static_method(kwarg1=None):
        '''return a value that is a function of kwarg1'''

The above uses the decorator syntax. This syntax is equivalent to

class ClassName(object):

    def static_method(kwarg1=None):
        '''return a value that is a function of kwarg1'''

    static_method = staticmethod(static_method)

This can be used just as you described:


A builtin example of a static method is str.maketrans() in Python 3, which was a function in the string module in Python 2.

Another option that can be used as you describe is the classmethod, the difference is that the classmethod gets the class as an implicit first argument, and if subclassed, then it gets the subclass as the implicit first argument.

class ClassName(object):

    def class_method(cls, kwarg1=None):
        '''return a value that is a function of the class and kwarg1'''

Note that cls is not a required name for the first argument, but most experienced Python coders will consider it badly done if you use anything else.

These are typically used as alternative constructors.

new_instance = ClassName.class_method()

A builtin example is dict.fromkeys():

new_dict = dict.fromkeys(['key1', 'key2'])

Does Java read integers in little endian or big endian?

If it fits the protocol you use, consider using a DataInputStream, where the behavior is very well defined.

Bash Shell Script - Check for a flag and grab its value

Here is a generalized simple command argument interface you can paste to the top of all your scripts.


declare -A flags
declare -A booleans

while [ "$1" ];
    if [ "${1:0:1}" == "-" ]
      rev=$(echo "$arg" | rev)
      if [ -z "$1" ] || [ "${1:0:1}" == "-" ] || [ "${rev:0:1}" == ":" ]
        bool=$(echo ${arg:1} | sed s/://g)
        echo \"$bool\" is boolean
        echo \"$arg\" is flag with value \"$value\"
      echo \"$arg\" is an arg

echo -e "\n"
echo booleans: ${booleans[@]}
echo flags: ${flags[@]}
echo args: ${args[@]}

echo -e "\nBoolean types:\n\tPrecedes Flag(pf): ${booleans[pf]}\n\tFinal Arg(f): ${booleans[f]}\n\tColon Terminated(Ct): ${booleans[Ct]}\n\tNot Mentioned(nm): ${boolean[nm]}"
echo -e "\nFlag: myFlag => ${flags["myFlag"]}"
echo -e "\nArgs: one: ${args[0]}, two: ${args[1]}, three: ${args[2]}"

By running the command: firstArg -pf -myFlag "my flag value" secondArg -Ct: thirdArg -f

The output will be this:

"firstArg" is an arg
"pf" is boolean
"-myFlag" is flag with value "my flag value"
"secondArg" is an arg
"Ct" is boolean
"thirdArg" is an arg
"f" is boolean

booleans: true true true
flags: my flag value
args: firstArg secondArg thirdArg

Boolean types:
    Precedes Flag(pf): true
    Final Arg(f): true
    Colon Terminated(Ct): true
    Not Mentioned(nm): 

Flag: myFlag => my flag value

Args: one => firstArg, two => secondArg, three => thirdArg

Basically, the arguments are divided up into flags booleans and generic arguments. By doing it this way a user can put the flags and booleans anywhere as long as he/she keeps the generic arguments (if there are any) in the specified order.

Allowing me and now you to never deal with bash argument parsing again!

You can view an updated script here

This has been enormously useful over the last year. It can now simulate scope by prefixing the variables with a scope parameter.

Just call the script like

replace() (
  source $FUTIL_REL_DIR/ -scope ${FUNCNAME[0]} "$@"
  echo ${replaceFlags[f]}
  echo ${replaceBooleans[b]}

Doesn't look like I implemented argument scope, not sure why I guess I haven't needed it yet.

Selenium C# WebDriver: Wait until element is present

Alternatively you can use an implicit wait:

driver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(10);

An implicit wait is to tell WebDriver to poll the DOM for a certain amount of time when trying to find an element or elements if they are not immediately available. The default setting is 0. Once set, the implicit wait is set for the life of the WebDriver object instance.

What is difference between png8 and png24

There is only one PNG format, but it supports 5 color types.

PNG-8 refers to palette variant, which supports only 256 colors, but is usually smaller in size. PNG-8 can be a GIF substitute.

PNG-24 refers to true color variant, which supports more colors, but might be bigger. PNG-24 can be used instead of JPEG, if lossless image format is needed.

Any modern web browser will support both variants.

background-image: url("images/plaid.jpg") no-repeat; wont show up

Most important

Keep in mind that relative URLs are resolved from the URL of your stylesheet.

So it will work if folder images is inside the stylesheets folder.

From you description you would need to change it to either




Additional 1

Also you cannot have no selector..

CSS is applied through selectors..

Additional 2

You should use either the shorthand background to pass multiple values like this

background: url("../images/plaid.jpg") no-repeat;

or the verbose syntax of specifying each property on its own

background-image: url("../images/plaid.jpg");

How to call a function from another controller in angularjs?

I wouldn't use function from one controller into another. A better approach would be to move the common function to a service and then inject the service in both controllers.

Changing the row height of a datagridview

Make sure AutoSizeRowsMode is set to None else the row height won't matter because well... it'll auto-size the rows.

Should be an easy thing but I fought this for a few hours before I figured it out.

Better late than never to respond =)

Jquery UI tooltip does not support html content

You can also achieve this completely without jQueryUI by using CSS styles. See the snippet below:

div#Tooltip_Text_container {_x000D_
  max-width: 25em;_x000D_
  height: auto;_x000D_
  display: inline;_x000D_
  position: relative;_x000D_
div#Tooltip_Text_container a {_x000D_
  text-decoration: none;_x000D_
  color: black;_x000D_
  cursor: default;_x000D_
  font-weight: normal;_x000D_
div#Tooltip_Text_container a span.tooltips {_x000D_
  visibility: hidden;_x000D_
  opacity: 0;_x000D_
  transition: visibility 0s linear 0.2s, opacity 0.2s linear;_x000D_
  position: absolute;_x000D_
  left: 10px;_x000D_
  top: 18px;_x000D_
  width: 30em;_x000D_
  border: 1px solid #404040;_x000D_
  padding: 0.2em 0.5em;_x000D_
  cursor: default;_x000D_
  line-height: 140%;_x000D_
  font-size: 12px;_x000D_
  font-family: 'Segoe UI';_x000D_
  -moz-border-radius: 3px;_x000D_
  -webkit-border-radius: 3px;_x000D_
  border-radius: 3px;_x000D_
  -moz-box-shadow: 7px 7px 5px -5px #666;_x000D_
  -webkit-box-shadow: 7px 7px 5px -5px #666;_x000D_
  box-shadow: 7px 7px 5px -5px #666;_x000D_
  background: #E4E5F0  repeat-x;_x000D_
div#Tooltip_Text_container:hover a span.tooltips {_x000D_
  visibility: visible;_x000D_
  opacity: 1;_x000D_
  transition-delay: 0.2s;_x000D_
div#Tooltip_Text_container img {_x000D_
  left: -10px;_x000D_
div#Tooltip_Text_container:hover a span.tooltips {_x000D_
  visibility: visible;_x000D_
  opacity: 1;_x000D_
  transition-delay: 0.2s;_x000D_
<div id="Tooltip_Text_container">_x000D_
  <span><b>Tooltip headline</b></span>_x000D_
  <a href="#">_x000D_
    <span class="tooltips">_x000D_
        <b>This is&nbsp;</b> a tooltip<br/>_x000D_
        <b>This is&nbsp;</b> another tooltip<br/>_x000D_
  <br/>Move the mousepointer to the tooltip headline above. _x000D_

The first span is for the displayed text, the second span for the hidden text, which is shown when you hover over it.

How to get first item from a java.util.Set?

From the Oracle docs:

As implied by its name, this interface models the mathematical set abstraction.

In Set Theory, "a "set" is a collection of distinct objects, considered as an object in its own right." - [Wikipedia - Set].

Mathematically, elements in sets are not individualised. Their only identity is derived from their presence in the set. Therefore, there is no point in getting the "first" element in a set, as conceptually such a task is illogical.

There may be no point to getting the "first" element from a set, but if all you need is to get one single object from a set (with no guarantees as to which object that is) you can do the following:

for(String aSiteId: siteIdSet) {
    siteId = aSiteId;

This is a slightly shorter way (than the method you posted) to get the "first" object of a Set, however since an Iterator is still being created (under the hood) it does not grant any performance benefit.

Easy way to print Perl array? (with a little formatting)

You can simply print it.

@a = qw(abc def hij);

print "@a";

You will got:

abc def hij

Convert `List<string>` to comma-separated string

The following will result in a comma separated list. Be sure to include a using statement for System.Linq

List<string> ls = new List<string>();
string type = ls.Aggregate((x,y) => x + "," + y);

will yield one,two

if you need a space after the comma, simply change the last line to string type = ls.Aggregate((x,y) => x + ", " + y);

What is @RenderSection in MVC

Suppose if I have GetAllEmployees.cshtml


    <a asp-action="Create">Create New</a>
<table class="table">
         // do something ...
       // do something ...

   //Added my custom scripts in the scripts sections

@section Scripts
    <script src="~/js/customScripts.js"></script>

And another view "GetEmployeeDetails.cshtml" with no scripts


    <a asp-action="Create">Create New</a>
<table class="table">
       // do something ... 
       // do something ...

And my layout page "_layout.cshtml"

@RenderSection("Scripts", required: true)

So, when I navigate to GetEmployeeDetails.cshtml. I get the error that there is no section scripts to be rendered in GetEmployeeDetails.cshtml. If I change the flag in @RenderSection() from required : true to ``required : false`. It means render the scripts defined in the @section scripts of the views if present.Else, do nothing. And the refined approach would be in _layout.cshtml

@if (IsSectionDefined("Scripts"))
        @RenderSection("Scripts", required: true)

Equivalent of waitForVisible/waitForElementPresent in Selenium WebDriver tests using Java?

WebElement myDynamicElement = (new WebDriverWait(driver, 10))

This waits up to 10 seconds before throwing a TimeoutException or if it finds the element will return it in 0 - 10 seconds. WebDriverWait by default calls the ExpectedCondition every 500 milliseconds until it returns successfully. A successful return is for ExpectedCondition type is Boolean return true or not null return value for all other ExpectedCondition types.

WebDriverWait wait = new WebDriverWait(driver, 10);
WebElement element = wait.until(ExpectedConditions.elementToBeClickable("someid")));

Element is Clickable - it is Displayed and Enabled.

From WebDriver docs: Explicit and Implicit Waits

Example of Named Pipes

Linux dotnet core doesn't support namedpipes!

Try TcpListener if you deploy to Linux

This NamedPipe Client/Server code round trips a byte to a server.

  • Client writes byte
  • Server reads byte
  • Server writes byte
  • Client reads byte

DotNet Core 2.0 Server ConsoleApp

using System;
using System.IO.Pipes;
using System.Threading.Tasks;

namespace Server
    class Program
        static void Main(string[] args)
            var server = new NamedPipeServerStream("A", PipeDirection.InOut);

            for (int i =0; i < 10000; i++)
                var b = new byte[1];
                server.Read(b, 0, 1); 
                Console.WriteLine("Read Byte:" + b[0]);
                server.Write(b, 0, 1);

DotNet Core 2.0 Client ConsoleApp

using System;
using System.IO.Pipes;
using System.Threading.Tasks;

namespace Client
    class Program
        public static int threadcounter = 1;
        public static NamedPipeClientStream client;

        static void Main(string[] args)
            client = new NamedPipeClientStream(".", "A", PipeDirection.InOut, PipeOptions.Asynchronous);

            var t1 = new System.Threading.Thread(StartSend);
            var t2 = new System.Threading.Thread(StartSend);


        public static void StartSend()
            int thisThread = threadcounter;


            for (int i = 0; i < 10000; i++)
                var buf = new byte[1];
                buf[0] = (byte)i;
                client.WriteAsync(buf, 0, 1);

                Console.WriteLine($@"Thread{thisThread} Wrote: {buf[0]}");

        public static async Task StartReadingAsync(NamedPipeClientStream pipe)
            var bufferLength = 1; 
            byte[] pBuffer = new byte[bufferLength];

            await pipe.ReadAsync(pBuffer, 0, bufferLength).ContinueWith(async c =>
                Console.WriteLine($@"read data {pBuffer[0]}");
                await StartReadingAsync(pipe); // read the next data <-- 

Python; urllib error: AttributeError: 'bytes' object has no attribute 'read'

I'm not familiar with python 3 yet, but it seems like urllib.request.urlopen().read() returns a byte object rather than string.

You might try to feed it into a StringIO object, or even do a str(response).

Convert List<Object> to String[] in Java

You could use toArray() to convert into an array of Objects followed by this method to convert the array of Objects into an array of Strings:

Object[] objectArray = lst.toArray();
String[] stringArray = Arrays.copyOf(objectArray, objectArray.length, String[].class);

Classpath including JAR within a JAR

You need to build a custom class-loader to do this or a third-party library that supports this. Your best bet is to extract the jar from the runtime and add them to the classpath (or have them already added to the classpath).

How to get div height to auto-adjust to background size?

This Worked For Me:

background-image: url("/assets/image_complete_path");
background-position: center; /* Center the image */
background-repeat: no-repeat; /* Do not repeat the image */
background-size: cover;
height: 100%;

How to "log in" to a website using Python's Requests module?

I know you've found another solution, but for those like me who find this question, looking for the same thing, it can be achieved with requests as follows:

Firstly, as Marcus did, check the source of the login form to get three pieces of information - the url that the form posts to, and the name attributes of the username and password fields. In his example, they are inUserName and inUserPass.

Once you've got that, you can use a requests.Session() instance to make a post request to the login url with your login details as a payload. Making requests from a session instance is essentially the same as using requests normally, it simply adds persistence, allowing you to store and use cookies etc.

Assuming your login attempt was successful, you can simply use the session instance to make further requests to the site. The cookie that identifies you will be used to authorise the requests.


import requests

# Fill in your details here to be posted to the login form.
payload = {
    'inUserName': 'username',
    'inUserPass': 'password'

# Use 'with' to ensure the session context is closed after use.
with requests.Session() as s:
    p ='LOGIN_URL', data=payload)
    # print the html returned or something more intelligent to see if it's a successful login page.
    print p.text

    # An authorised request.
    r = s.get('A protected web page url')
    print r.text
        # etc...

Excel VBA code to copy a specific string to clipboard

If you want to put a variable's value in the clipboard using the Immediate window, you can use this single line to easily put a breakpoint in your code:

Set MSForms_DataObject = CreateObject("new:{1C3B4210-F441-11CE-B9EA-00AA006B1A69}"): MSForms_DataObject.SetText VARIABLENAME: MSForms_DataObject.PutInClipboard: Set MSForms_DataObject = Nothing

Retrieve a single file from a repository

For single file, just use wget command.

First, follow the pic below to click "raw" to get the url, otherwise you will download code embedded in html. enter image description here

Then, the browser will open a new page with url start with

just enter the command in the terminal:


A while the file will put in your folder.

Shell script to get the process ID on Linux

option -v is very important. It can exclude a grep expression itself


ps -w | grep sshd | grep -v grep | awk '{print $1}' to get sshd id

How do I install command line MySQL client on mac?

If you installed from the DMG on a mac, it created a mysql client but did not put it in your user path.

Add this to your .bash_profile:

export PATH="/usr/local/mysql/bin:$PATH

This will let you run mysql from anywhere as you.

What is the Oracle equivalent of SQL Server's IsNull() function?

Instead of ISNULL(), use NVL().


SELECT ISNULL(SomeNullableField, 'If null, this value') FROM SomeTable


SELECT NVL(SomeNullableField, 'If null, this value') FROM SomeTable

get jquery `$(this)` id

Do you mean that for a select element with an id of "next" you need to perform some specific script?

    //enter code here

Google Maps API v3: Can I setZoom after fitBounds?

All I did is:

map.setCenter(bounds.getCenter(), map.getBoundsZoomLevel(bounds));

And it works on V3 API.

How to uninstall downloaded Xcode simulator?

Slightly off topic but could be very useful as it could be the basis for other tasks you might want to do with simulators.

I like to keep my simulator list to a minimum, and since there is no multi-select in the "Devices and Simulators" it is a pain to delete them all.

So I boot all the sims that I want to use then, remove all the simulators that I don't have booted.

Delete all the shutdown simulators:

xcrun simctl list | grep -w "Shutdown"  | grep -o "([-A-Z0-9]*)" | sed 's/[\(\)]//g' | xargs -I uuid xcrun simctl delete  uuid

If you need individual simulators back, just add them back to the list in "Devices and Simulators" with the plus button.

enter image description here

git stash apply version

git Stash list 

List will show all stashed items eg:stash@{0}:,stash@{1}:,..,stash@{n}:

Then select the number n which denotes stash@{n}:

git stash apply n 

for example:

git stash apply 1 

will apply that particular stashed changes to the current branch

How do I turn a String into a InputStreamReader in java?

Are you trying to get a) Reader functionality out of InputStreamReader, or b) InputStream functionality out of InputStreamReader? You won't get b). InputStreamReader is not an InputStream.

The purpose of InputStreamReader is to take an InputStream - a source of bytes - and decode the bytes to chars in the form of a Reader. You already have your data as chars (your original String). Encoding your String into bytes and decoding the bytes back to chars would be a redundant operation.

If you are trying to get a Reader out of your source, use StringReader.

If you are trying to get an InputStream (which only gives you bytes), use apache commons IOUtils.toInputStream(..) as suggested by other answers here.

Django upgrading to 1.9 error "AppRegistryNotReady: Apps aren't loaded yet."

Late to the party, but grappelli was the reason for my error as well. I looked up the compatible version on pypi and that fixed it for me.

Center align "span" text inside a div

If you know the width of the span you could just stuff in a left margin.

Try this:

.center { text-align: center} span { display: table; }

Add the "center: class to your .

If you want some spans centered, but not others, replace the " span" in your style sheet to a class (e.g "center-span") and add that class to the span.

Why is the Java main method static?

From (there's more information on the site) :

The main method is static to give the Java VM interpreter a way to start the class without creating an instance of the control class first. Instances of the control class are created in the main method after the program starts.

My understanding has always been simply that the main method, like any static method, can be called without creating an instance of the associated class, allowing it to run before anything else in the program. If it weren't static, you would have to instantiate an object before calling it-- which creates a 'chicken and egg' problem, since the main method is generally what you use to instantiate objects at the beginning of the program.

How to get the file path from HTML input form in Firefox 3

We can't get complete file path in FF3. The below might be useful for File component customization.


function setFileName()
    var file1=document.forms[0].firstAttachmentFileName.value; 

function initFileUploads(fileName,fileinputs,fileValue) {
    var fakeFileUpload = document.createElement('div');
    fakeFileUpload.className = 'fakefile';
    var filename = document.createElement('input');
    var image = document.createElement('input');
    image.value='Browse File';
    var x = document.getElementsByTagName('input');
    for (var i=0; i&lt;x.length;i++) {
        if (x[i].type != 'file') continue;
        if (x[i].parentNode.className != fileinputs) continue;
        x[i].className = 'file hidden';
        var clone = fakeFileUpload.cloneNode(true);
        x[i].relatedElement = clone.getElementsByTagName('input')[0];
        x[i].onchange= function () {
            this.relatedElement.value = this.value;
    if(document.forms[0].firstFile != null && document.getElementById('firstFile1') != null)
    document.getElementById('firstFile1').value= document.forms[0].firstFile.value;

function submitFile()
alert( document.forms[0].firstAttachmentFileName.value);
<style>div.fileinputs1 {position: relative;}div.fileinputs2 {position: relative;}
div.fakefile {position: absolute;top: 0px;left: 0px;z-index: 1;}
input.file {position: relative;text-align: right;-moz-opacity:0 ;filter:alpha(opacity: 0);
    opacity: 0;z-index: 2;}</style>

<body onLoad ="setFileName();">
<div class="fileinputs1">
<INPUT TYPE=file NAME="firstAttachmentFileName" styleClass="file" />
<INPUT type="button" value="submit" onclick="submitFile();" />

ValidateRequest="false" doesn't work in Asp.Net 4

Note that another approach is to keep with the 4.0 validation behaviour, but to define your own class that derives from RequestValidator and set:

<httpRuntime requestValidationType="YourNamespace.YourValidator" />

(where YourNamespace.YourValidator is well, you should be able to guess...)

This way you keep the advantages of 4.0s behaviour (specifically, that the validation happens earlier in the processing), while also allowing the requests you need to let through, through.

Handler "ExtensionlessUrlHandler-Integrated-4.0" has a bad module "ManagedPipelineHandler" in its module list

I'm working on Windows Server 2012. .NET Extensibility 4.5 feature is on. WebDAVModule removed. I was still getting 500.21 error on ASP.NET route '/docs'.

Changing 'skipManagedModules' to false fixed the problem.

<applicationInitialization doAppInitAfterRestart="true" skipManagedModules="false">
        <add initializationPage="/docs" />    

Thanks to!topic/bonobo-git-server/GbdMXdDO4tI

Add padding on view programmatically

Using TypedValue is a much cleaner way of converting to pixels compared to manually calculating:

float paddingDp = 10f;
// Convert to pixels
int paddingPx = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, paddingDp, context.getResources().getDisplayMetrics());
view.setPadding(paddingPx, paddingPx, paddingPx, paddingPx);

Essentially, TypedValue.applyDimension converts the desired padding into pixels appropriately depending on the current device's display properties.

For more info see: TypedValue.applyDimension Docs.

Ant is using wrong java version

Just had this issue, it happened because I'd first added the build file to the ant-view when the default JRE was 1.6.

There was no project-specific JRE and I changed the default to 1.5, even eclipse was running in 1.5, and JAVA_HOME was 1.5 too. Running the ant target from the command line used JRE 1.5, but within eclipse it still used 1.6.

I had to right-click the ant target, select Run As... and change the JRE under the JRE tab. This setting is remembered for subsequent runs.

Excel add one hour


Although, maybe this should be posted on Super User.

How can I change the text color with jQuery?

Nowadays, animating text color is included in the jQuery UI Effects Core. It's pretty small. You can make a custom download here: - but you don't actually need anything but the effects core itself (not even the UI core), and it brings with it different easing functions as well.

Filter multiple values on a string column in dplyr

You need %in% instead of ==:

target <- c("Tom", "Lynn")
filter(dat, name %in% target)  # equivalently, dat %>% filter(name %in% target)


  days name
1   88 Lynn
2   11  Tom
3    1  Tom
4  222 Lynn
5    2 Lynn

To understand why, consider what happens here:

dat$name == target

Basically, we're recycling the two length target vector four times to match the length of dat$name. In other words, we are doing:

 Lynn == Tom
  Tom == Lynn
Chris == Tom
 Lisa == Lynn
 ... continue repeating Tom and Lynn until end of data frame

In this case we don't get an error because I suspect your data frame actually has a different number of rows that don't allow recycling, but the sample you provide does (8 rows). If the sample had had an odd number of rows I would have gotten the same error as you. But even when recycling works, this is clearly not what you want. Basically, the statement dat$name == target is equivalent to saying:

return TRUE for every odd value that is equal to "Tom" or every even value that is equal to "Lynn".

It so happens that the last value in your sample data frame is even and equal to "Lynn", hence the one TRUE above.

To contrast, dat$name %in% target says:

for each value in dat$name, check that it exists in target.

Very different. Here is the result:


Note your problem has nothing to do with dplyr, just the mis-use of ==.

Compare 2 arrays which returns difference

function subtractarrays(array1, array2){
    var difference = [];
    for( var i = 0; i < array1.length; i++ ) {
        if( $.inArray( array1[i], array2 ) == -1 ) {

    return difference;

You can then call the function anywhere in your code.

var I_like    = ["love", "sex", "food"];
var she_likes = ["love", "food"];

alert( "what I like and she does't like is: " + subtractarrays( I_like, she_likes ) ); //returns "Naughty"!

This works in all cases and avoids the problems in the methods above. Hope that helps!

How do I make a https post in Node Js without any third party module?

For example, like this:

const querystring = require('querystring');
const https = require('https');

var postData = querystring.stringify({
    'msg' : 'Hello World!'

var options = {
  hostname: '',
  port: 443,
  path: '/post.php',
  method: 'POST',
  headers: {
       'Content-Type': 'application/x-www-form-urlencoded',
       'Content-Length': postData.length

var req = https.request(options, (res) => {
  console.log('statusCode:', res.statusCode);
  console.log('headers:', res.headers);

  res.on('data', (d) => {

req.on('error', (e) => {


.htaccess redirect http to https

Searching for the best way to redirect, i've found this (coming from html5boilerplate) :

# ----------------------------------------------------------------------
# | HTTP Strict Transport Security (HSTS)                              |
# ----------------------------------------------------------------------

# Force client-side SSL redirection.
# If a user types `` in their browser, even if the server
# redirects them to the secure version of the website, that still leaves
# a window of opportunity (the initial HTTP connection) for an attacker
# to downgrade or redirect the request.
# The following header ensures that browser will ONLY connect to your
# server via HTTPS, regardless of what the users type in the browser's
# address bar.
# (!) Remove the `includeSubDomains` optional directive if the website's
# subdomains are not using HTTPS.

Header set Strict-Transport-Security "max-age=16070400; includeSubDomains"

Maybe it will help someone in 2017 ! :)

Detect Click into Iframe using JavaScript

Assumptions -

  1. Your script runs outside the iframe BUT NOT in the outermost window. (For outermost window, other blur solutions are good enough)
  2. A new page is opened replacing the current page / a new page in a new tab and control is switched to new tab.

This works for both sourceful and sourceless iframes

var ifr = document.getElementById("my-iframe");
var isMouseIn;
ifr.addEventListener('mouseenter', () => {
    isMouseIn = true;
ifr.addEventListener('mouseleave', () => {
    isMouseIn = false;
window.document.addEventListener("visibilitychange", () => {
    if (isMouseIn && document.hidden) {
        console.log("Click Recorded By Visibility Change");
window.addEventListener("beforeunload", (event) => {
    if (isMouseIn) {
        console.log("Click Recorded By Before Unload");

If a new tab is opened / same page unloads and the mouse pointer is within the Iframe, a click is considered

How to convert int to Integer

int iInt = 10;
Integer iInteger = new Integer(iInt);

How to open a PDF file in an <iframe>?

Do it like this: Remember to close iframe tag.

<iframe src="" width="800" height="600"></iframe>

How do I do a case-insensitive string comparison?

def insenStringCompare(s1, s2):
    """ Method that takes two strings and returns True or False, based
        on if they are equal, regardless of case."""
        return s1.lower() == s2.lower()
    except AttributeError:
        print "Please only pass strings into this method."
        print "You passed a %s and %s" % (s1.__class__, s2.__class__)

How can I display a pdf document into a Webview?

Use this code:

private void pdfOpen(String fileUrl){


        //---you need this to prevent the webview from
        // launching another browser when a url
        // redirection occurs---
        webView.setWebViewClient(new Callback());

                "" + fileUrl);


    private class Callback extends WebViewClient {
        public boolean shouldOverrideUrlLoading(
                WebView view, String url) {
            return (false);

What is the correct way to write HTML using Javascript?

There are many ways to write html with JavaScript.

document.write is only useful when you want to write to page before it has actually loaded. If you use document.write() after the page has loaded (at onload event) it will create new page and overwrite the old content. Also it doesn't work with XML, that includes XHTML.

From other hand other methods can't be used before DOM has been created (page loaded), because they work directly with DOM.

These methods are:

  • node.innerHTML = "Whatever";
  • document.createElement('div'); and node.appendChild(), etc..

In most cases node.innerHTML is better since it's faster then DOM functions. Most of the time it also make code more readable and smaller.

How can I use the HTML5 canvas element in IE?

Currently, ExplorerCanvas is the only option to emulate HTML5 canvas for IE6, 7, and 8. You're also right about its performance, which is pretty poor.

I found a particle simulatior that benchmarks the difference between true HTML5 canvas handling in Google Chrome, Safari, and Firefox, vs ExplorerCanvas in IE. The results show that the major browsers that do support the canvas tag run about 20 to 30 times faster than the emulated HTML5 in IE with ExplorerCanvas.

I doubt that anyone will go through the effort of creating an alternative because 1) excanvas.js is about as cleanly coded as it gets and 2) when IE9 is released all of the major browsers will finally support the canvas object. Hopefully, We'll get IE9 within a year

Eric @

Find out who is locking a file on a network share

sounds like you have the same problem i tried to solve here. in my case, it's a Linux fileserver (running samba, of course), so i can log in and see what process is locking the file; unfortunately, i haven't found how to close it without killing the responsible session. AFAICT, the windows client 'thinks' it's closed; but didn't bother telling the fileserver.

PDOException SQLSTATE[HY000] [2002] No such file or directory

Check your port carefully . In my case it was 8889 and i am using 8888. change "DB_HOST" from "localhost" to "" and vice versa

How do I use a pipe to redirect the output of one command to the input of another?

Not sure if you are coding these programs, but this is a simple example of how you'd do it.


#include <stdio.h>
int main (int argc, char * argv[] ) {
    printf("%s", argv[1]); 
    return 0;


#include <cstdio>
#include <regex>
#include <iostream>
using namespace std;
int main (int argc, char * argv[] ) {
    char input[200];
    string s(input)
    smatch m;
    string reg_exp(argv[1]);
    regex e(reg_exp);
    while (regex_search (s,m,e)) {
      for (auto x:m) cout << x << " ";
      cout << endl;
      s = m.suffix().str();
    return 0;

Compile both then run program1.exe "this subject has a submarine as a subsequence" | rgx.exe "\b(sub)([^ ]*)"

The | operator simply redirects the output of program1's printf operation from the stdout stream to the stdin stream whereby it's sitting there waiting for rgx.exe to pick up.

show distinct column values in pyspark dataframe: python

collect_set can help to get unique values from a given column of pyspark.sql.DataFrame"column").alias("column")).first()["column"]

#1071 - Specified key was too long; max key length is 767 bytes

For me, the issue of "#1071 - Specified key was too long; max key length is 767 bytes" got resolved after changing the primarykey / uniquekey combination by limiting the column size by 200.

`column1` (200) ,
`column2` (200)

Broadcast Receiver within a Service

as your service is already setup, simply add a broadcast receiver in your service:

private final BroadcastReceiver receiver = new BroadcastReceiver() {
   public void onReceive(Context context, Intent intent) {
      String action = intent.getAction();
        //action for sms received
      else if(action.equals(android.telephony.TelephonyManager.ACTION_PHONE_STATE_CHANGED)){
           //action for phone state changed

in your service's onCreate do this:

IntentFilter filter = new IntentFilter();
filter.addAction("your_action_strings"); //further more
filter.addAction("your_action_strings"); //further more

registerReceiver(receiver, filter);

and in your service's onDestroy:


and you are good to go to receive broadcast for what ever filters you mention in onCreate. Make sure to add any permission if required. for e.g.

<uses-permission android:name="android.permission.RECEIVE_SMS" />

How to copy a selection to the OS X clipboard

I used:

map <C-x> :!pbcopy<CR>
vmap <C-c> :w !pbcopy<CR><CR>

It worked really well.

Run batch file from Java code

Rather than Runtime.exec(String command), you need to use the exec(String command, String[] envp, File dir) method signature:

Process p =  Runtime.getRuntime().exec("cmd /c upsert.bat", null, new File("C:\\Program Files\\\\Data Loader\\cliq_process\\upsert"));

But personally, I'd use ProcessBuilder instead, which is a little more verbose but much easier to use and debug than Runtime.exec().

ProcessBuilder pb = new ProcessBuilder("cmd", "/c", "upsert.bat");
File dir = new File("C:/Program Files/ Loader/cliq_process/upsert");;
Process p = pb.start();

How to refresh a Page using react-route Link

Try like this.

You must give a function as value to onClick()

You button:

<button type="button" onClick={ refreshPage }> <span>Reload</span> </button> 

refreshPage function:

function refreshPage(){ 

Refresh certain row of UITableView based on Int in Swift

I realize this question is for Swift, but here is the Xamarin equivalent code of the accepted answer if someone is interested.

var indexPath = NSIndexPath.FromRowSection(rowIndex, 0);
tableView.ReloadRows(new NSIndexPath[] { indexPath }, UITableViewRowAnimation.Top);

How to generate JAXB classes from XSD?

In intellij click .xsd file -> WebServices ->Generate Java code from Xml Schema JAXB then give package path and package name ->ok

Cannot convert lambda expression to type 'string' because it is not a delegate type

My case it solved i was using

@Html.DropDownList(model => model.TypeId ...)  


@Html.DropDownListFor(model => model.TypeId ...) 

will solve it

Advantages of using display:inline-block vs float:left in CSS

While I agree that in general inline-block is better, there's one extra thing to take into account if you're using percentage widths to create a responsive grid (or if you want pixel-perfect widths):

If you're using inline-block for grids that total 100% or near to 100% width, you need to make sure your HTML markup contains no white space between columns.

With floats, this is not something you need to worry about - the columns float over any whitespace or other content between columns. This question's answers have some good tips on ways to remove HTML whitespace without making your code ugly.

If for any reason you can't control the HTML markup (e.g. a restrictive CMS), you can try the tricks described here, or you might need to compromise and use floats instead of inline-block. There are also ugly CSS tricks that should only be used in extreme circumstances, like font-size:0; on the column container then reapply font size within each column.

For example:

VBA: How to display an error message just like the standard error message which has a "Debug" button?

This answer does not address the Debug button (you'd have to design a form and use the buttons on that to do something like the method in your next question). But it does address this part:

now I don't want to lose the comfortableness of the default handler which also point me to the exact line where the error has occured.

First, I'll assume you don't want this in production code - you want it either for debugging or for code you personally will be using. I use a compiler flag to indicate debugging; then if I'm troubleshooting a program, I can easily find the line that's causing the problem.

# Const IsDebug = True

Sub ProcA()
On Error Goto ErrorHandler
' Main code of proc

    On Error Resume Next
    ' Close objects and stuff here
    Exit Sub

    MsgBox Err.Number & ": " & Err.Description, , ThisWorkbook.Name & ": ProcA"
    #If IsDebug Then
        Stop            ' Used for troubleshooting - Then press F8 to step thru code 
        Resume          ' Resume will take you to the line that errored out
        Resume ExitHere ' Exit procedure during normal running
    #End If
End Sub

Note: the exception to Resume is if the error occurs in a sub-procedure without an error handling routine, then Resume will take you to the line in this proc that called the sub-procedure with the error. But you can still step into and through the sub-procedure, using F8 until it errors out again. If the sub-procedure's too long to make even that tedious, then your sub-procedure should probably have its own error handling routine.

There are multiple ways to do this. Sometimes for smaller programs where I know I'm gonna be stepping through it anyway when troubleshooting, I just put these lines right after the MsgBox statement:

    Resume ExitHere         ' Normally exits during production
    Resume                  ' Never will get here
Exit Sub

It will never get to the Resume statement, unless you're stepping through and set it as the next line to be executed, either by dragging the next statement pointer to that line, or by pressing CtrlF9 with the cursor on that line.

Here's an article that expands on these concepts: Five tips for handling errors in VBA. Finally, if you're using VBA and haven't discovered Chip Pearson's awesome site yet, he has a page explaining Error Handling In VBA.

'0000-00-00 00:00:00' can not be represented as java.sql.Timestamp error

I believe this is help full for who are getting this below Exception on to pumping data through logstash Error: logstash.inputs.jdbc - Exception when executing JDBC query {:exception=>#}


or if you are working with mysql

Ruby: How to iterate over a range, but in set increments?

rng.step(n=1) {| obj | block } => rng

Iterates over rng, passing each nth element to the block. If the range contains numbers or strings, natural ordering is used. Otherwise step invokes succ to iterate through range elements. The following code uses class Xs, which is defined in the class-level documentation.

range =
range.step(2) {|x| puts x}
range.step(3) {|x| puts x}


1 x
3 xxx
5 xxxxx
7 xxxxxxx
9 xxxxxxxxx
1 x
4 xxxx
7 xxxxxxx
10 xxxxxxxxxx



Add line break to 'git commit -m' from the command line

If you just want, say, a head line and a content line, you can use:

git commit -m "My head line" -m "My content line."

Note that this creates separate paragraphs - not lines. So there will be a blank line between each two -m lines, e.g.:

My head line

My content line.

How do I deal with special characters like \^$.?*|+()[{ in my regex?

I think the easiest way to match the characters like


are using character classes from within R. Consider the following to clean column headers from a data file, which could contain spaces, and punctuation characters:

> library(stringr)
> colnames(order_table) <- str_replace_all(colnames(order_table),"[:punct:]|[:space:]","")

This approach allows us to string character classes to match punctation characters, in addition to whitespace characters, something you would normally have to escape with \\ to detect. You can learn more about the character classes at this cheatsheet below, and you can also type in ?regexp to see more info about this.

How do I show the number keyboard on an EditText in android?

More input types and details found here on google website

How to analyze information from a Java core dump?

Actually, VisualVM can process application core dump.

Just invoke "File/Add VM Coredump" and will add a new application in the application explorer. You can then take thread dump or heap dump of that JVM.

What are 'get' and 'set' in Swift?

variable declares and call like this in a class

class X {
    var x: Int = 3

var y = X()
print("value of x is: ", y.x)

//value of x is:  3

now you want to program to make the default value of x more than or equal to 3. Now take the hypothetical case if x is less than 3, your program will fail. so, you want people to either put 3 or more than 3. Swift got it easy for you and it is important to understand this bit-advance way of dating the variable value because they will extensively use in iOS development. Now let's see how get and set will be used here.

class X {
    var _x: Int = 3
    var x: Int {
        get {
            return _x
        set(newVal) {  //set always take 1 argument
            if newVal >= 3 {
             _x = newVal //updating _x with the input value by the user
            print("new value is: ", _x)
            else {
                print("error must be greater than 3")
let y = X()
y.x = 1
print(y.x) //error must be greater than 3
y.x = 8 // //new value is: 8

if you still have doubts, just remember, the use of get and set is to update any variable the way we want it to be updated. get and set will give you better control to rule your logic. Powerful tool hence not easily understandable.

DateTime to javascript date


return DateTime.Now.Subtract(new DateTime(1970, 1,1)).TotalMilliseconds

Edit: true UTC is better, but then we need to be consistent

return DateTime.UtcNow
               .Subtract(new DateTime(1970,1,1,0,0,0,DateTimeKind.Utc))

Although, on second thoughts it does not matter, as long as both dates are in the same time zone.

PHP Foreach Arrays and objects

Looping over arrays and objects is a pretty common task, and it's good that you're wanting to learn how to do it. Generally speaking you can do a foreach loop which cycles over each member, assigning it a new temporary name, and then lets you handle that particular member via that name:

foreach ($arr as $item) {
    echo $item->sm_id;

In this example each of our values in the $arr will be accessed in order as $item. So we can print our values directly off of that. We could also include the index if we wanted:

foreach ($arr as $index => $item) {
    echo "Item at index {$index} has sm_id value {$item->sm_id}";

Generate PDF from HTML using pdfMake in Angularjs

this is what it worked for me I'm using html2pdf from an Angular2 app, so I made a reference to this function in the controller

var html2pdf = (function(html2canvas, jsPDF) {

declared in html2pdf.js.

So I added just after the import declarations in my angular-controller this declaration:

declare function html2pdf(html2canvas, jsPDF): any;

then, from a method of my angular controller I'm calling this function:

      pdfContent => {
        html2pdf(pdfContent, {
          margin:       1,
          filename:     'myfile.pdf',
          image:        { type: 'jpeg', quality: 0.98 },
          html2canvas:  { dpi: 192, letterRendering: true },
          jsPDF:        { unit: 'in', format: 'A4', orientation: 'portrait' }

Hope it helps

How to check if an option is selected?

If you want to check selected option through javascript

Simplest method is add onchange attribute in that tag and define a function in js file see example if your html file has options something like this

 <select onchange="subjects(this.value)">
               <option>Select subject</option>
               <option value="Computer science">Computer science</option>
               <option value="Information Technolgy">Information Technolgy</option>
               <option value="Electronic Engineering">Electronic Engineering</option>
               <option value="Electrical Engineering">Electrical Engineering</option>

And now add function in js file

function subjects(str){
    console.log(`selected option is ${str}`);

If you want to check selected option in php file

Simply give name attribute in your tag and access it php file global variables /array ($_GET or $_POST) see example if your html file is something like this

<form action="validation.php" method="POST">
            <select name="subject">
               <option>Select subject</option>
               <option value="Computer science">Computer science</option>
               <option value="Information Technolgy">Information Technolgy</option>
               <option value="Electronic Engineering">Electronic Engineering</option>
               <option value="Electrical Engineering">Electrical Engineering</option>


And in your php file validation.php you can access like this

$subject = $_POST['subject'];
echo "selected option is $subject";

Xcode warning: "Multiple build commands for output file"

As previously mentioned, this issue can be seen if you have multiple files with the same name, but in different groups (yellow folders) in the project navigator. In my case, this was intentional as I had multiple subdirectories each with a "preview.jpg" that I wanted copying to the app bundle:

group references

In this situation, you need to ensure that Xcode recognises the directory reference (blue folder icon), not just the groups.

Remove the offending files and choose "Remove Reference" (so we don't delete them entirely):

remove group references

Re-add them to the project by dragging them back into the project navigator. In the dialog that appears, choose "Create folder references for any added folders":

add as folder references

Notice that the files now have a blue folder icon in the project navigator:

folder references

If you now look under the "Copy Bundle Resources" section of the target's build phases, you will notice that there is a single entry for the entire folder, rather than entries for each item contained within the directory. The compiler will not complain about multiple build commands for those files.

How to copy and paste code without rich text formatting?

I wrote an unpublished java app to monitor the clipboard, replacing items that offered text along with other richer formats, with items only offering the plain text format.

Optimal way to concatenate/aggregate strings

Although @serge answer is correct but i compared time consumption of his way against xmlpath and i found the xmlpath is so faster. I'll write the compare code and you can check it by yourself. This is @serge way:

DECLARE @startTime datetime2;
DECLARE @endTime datetime2;
DECLARE @counter INT;
SET @counter = 1;

set nocount on;

declare @YourTable table (ID int, Name nvarchar(50))

WHILE @counter < 1000
    insert into @YourTable VALUES (ROUND(@counter/10,0), CONVERT(NVARCHAR(50), @counter) + 'CC')
    SET @counter = @counter + 1;

SET @startTime = GETDATE()

;WITH Partitioned AS
        COUNT(*) OVER (PARTITION BY ID) AS NameCount
    FROM @YourTable
Concatenated AS
    SELECT ID, CAST(Name AS nvarchar) AS FullName, Name, NameNumber, NameCount FROM Partitioned WHERE NameNumber = 1


        P.ID, CAST(C.FullName + ', ' + P.Name AS nvarchar), P.Name, P.NameNumber, P.NameCount
    FROM Partitioned AS P
        INNER JOIN Concatenated AS C ON P.ID = C.ID AND P.NameNumber = C.NameNumber + 1
FROM Concatenated
WHERE NameNumber = NameCount

SET @endTime = GETDATE();

SELECT DATEDIFF(millisecond,@startTime, @endTime)
--Take about 54 milliseconds

And this is xmlpath way:

DECLARE @startTime datetime2;
DECLARE @endTime datetime2;
DECLARE @counter INT;
SET @counter = 1;

set nocount on;

declare @YourTable table (RowID int, HeaderValue int, ChildValue varchar(5))

WHILE @counter < 1000
    insert into @YourTable VALUES (@counter, ROUND(@counter/10,0), CONVERT(NVARCHAR(50), @counter) + 'CC')
    SET @counter = @counter + 1;

SET @startTime = GETDATE();

set nocount off
                        ', ' + t2.ChildValue
                        FROM @YourTable t2
                        WHERE t1.HeaderValue=t2.HeaderValue
                        ORDER BY t2.ChildValue
                        FOR XML PATH(''), TYPE
                   ,1,2, ''
              ) AS ChildValues
    FROM @YourTable t1
    GROUP BY t1.HeaderValue

SET @endTime = GETDATE();

SELECT DATEDIFF(millisecond,@startTime, @endTime)
--Take about 4 milliseconds

How to download source in ZIP format from GitHub?

As of December 2016, the Clone or download button is still under the <> Code tab, however it is now to the far right of the header:

Github Clone or download screenshot

Showing line numbers in IPython/Jupyter Notebooks

Was looking for this: Shift-L in JupyterLab 1.0.0

Function pointer as a member of a C struct

The pointer str is never allocated. It should be malloc'd before use.

How to have multiple CSS transitions on an element?

.nav a {
    transition: color .2s, text-shadow .2s;

How can I get useful error messages in PHP?

This answer is brought to you by the department of redundancy department.

  1. ini_set() / php.ini / .htaccess / .user.ini

    The settings display_errors and error_reporting have been covered sufficiently now. But just to recap when to use which option:

    • ini_set() and error_reporting() apply for runtime errors only.
    • php.ini should primarily be edited for development setups. (Webserver and CLI version often have different php.ini's)
    • .htaccess flags only work for dated setups (Find a new hoster! Well managed servers are cheaper.)
    • .user.ini are partial php.ini's for modern setups (FCGI/FPM)

    And as crude alternative for runtime errors you can often use:

    set_error_handler("var_dump");   // ignores error_reporting and `@` suppression
  2. error_get_last()

    Can be used to retrieve the last runtime notice/warning/error, when error_display is disabled.

  3. $php_errormsg

    Is a superlocal variable, which also contains the last PHP runtime message.

  4. isset() begone!

    I know this will displease a lot of folks, but isset and empty should not be used by newcomers. You can add the notice suppression after you verified your code is working. But never before.

    A lot of the "something doesn't work" questions we get lately are the result of typos like:

    #                  ??

    You won't get any useful notices if your code is littered with isset/empty/array_keys_exists. It's sometimes more sensible to use @, so notices and warnings go to the logs at least.

  5. assert_options(ASSERT_ACTIVE|ASSERT_WARNING);

    To get warnings for assert() sections. (Pretty uncommon, but more proficient code might contain some.)

    PHP7 requires zend.assertions=1 in the php.ini as well.

  6. declare(strict_types=1);

    Bending PHP into a strictly typed language is not going to fix a whole lot of logic errors, but it's definitely an option for debugging purposes.

  7. PDO / MySQLi

    And @Phil already mentioned PDO/MySQLi error reporting options. Similar options exist for other database APIs of course.

  8. json_last_error() + json_last_error_msg

    For JSON parsing.

  9. preg_last_error()

    For regexen.


    To debug curl requests, you need CURLOPT_VERBOSE at the very least.

  11. shell/exec()

    Likewise will shell command execution not yield errors on its own. You always need 2>&1 and peek at the $errno.

Compare given date with today

$toBeComparedDate = '2014-08-12';
$today = (new DateTime())->format('Y-m-d'); //use format whatever you are using
$expiry = (new DateTime($toBeComparedDate))->format('Y-m-d');

var_dump(strtotime($today) > strtotime($expiry)); //false or true

Finish all activities at a time

close the app

Intent intent = new Intent(getApplicationContext(), Splash_Screen.class);
                intent.putExtra("EXIT", true);

put this in the oncreate and onResume of the very first activity that is opened. ex. is on splash screen activity

if (getIntent().getBooleanExtra("EXIT", false)) {

What is an application binary interface (ABI)?


There are various interpretation and strong opinions of the exact layer that define an ABI (application binary interface).

In my view an ABI is a subjective convention of what is considered a given/platform for a specific API. The ABI is the "rest" of conventions that "will not change" for a specific API or that will be addressed by the runtime environment: executors, tools, linkers, compilers, jvm, and OS.

Defining an Interface: ABI, API

If you want to use a library like joda-time you must declare a dependency on joda-time-<major>.<minor>.<patch>.jar. The library follows best practices and use Semantic Versioning. This defines the API compatibility at three levels:

  1. Patch - You don't need to change at all your code. The library just fixes some bugs.
  2. Minor - You don't need to change your code since the additions
  3. Major - The interface (API) is changed and you might need to change your code.

In order for you to use a new major release of the same library a lot of other conventions are still to be respected:

  • The binary language used for the libraries (in Java cases the JVM target version that defines the Java bytecode)
  • Calling conventions
  • JVM conventions
  • Linking conventions
  • Runtime conventions All these are defined and managed by the tools we use.


Java case study

For example, Java standardized all these conventions, not in a tool, but in a formal JVM specification. The specification allowed other vendors to provide a different set of tools that can output compatible libraries.

Java provides two other interesting case studies for ABI: Scala versions and Dalvik virtual machine.

Dalvik virtual machine broke the ABI

The Dalvik VM needs a different type of bytecode than the Java bytecode. The Dalvik libraries are obtained by converting the Java bytecode (with same API) for Dalvik. In this way you can get two versions of the same API: defined by the original joda-time-1.7.2.jar. We could call it joda-time-1.7.2.jar and joda-time-1.7.2-dalvik.jar. They use a different ABI one is for the stack-oriented standard Java vms: Oracle's one, IBM's one, open Java or any other; and the second ABI is the one around Dalvik.

Scala successive releases are incompatible

Scala doesn't have binary compatibility between minor Scala versions: 2.X . For this reason the same API "io.reactivex" %% "rxscala" % "0.26.5" has three versions (in the future more): for Scala 2.10, 2.11 and 2.12. What is changed? I don't know for now, but the binaries are not compatible. Probably the latest versions adds things that make the libraries unusable on the old virtual machines, probably things related to linking/naming/parameter conventions.

Java successive releases are incompatible

Java has problems with the major releases of the JVM too: 4,5,6,7,8,9. They offer only backward compatibility. Jvm9 knows how to run code compiled/targeted (javac's -target option) for all other versions, while JVM 4 doesn't know how to run code targeted for JVM 5. All these while you have one joda-library. This incompatibility flies bellow the radar thanks to different solutions:

  1. Semantic versioning: when libraries target higher JVM they usually change the major version.
  2. Use JVM 4 as the ABI, and you're safe.
  3. Java 9 adds a specification on how you can include bytecode for specific targeted JVM in the same library.

Why did I start with the API definition?

API and ABI are just conventions on how you define compatibility. The lower layers are generic in respect of a plethora of high level semantics. That's why it's easy to make some conventions. The first kind of conventions are about memory alignment, byte encoding, calling conventions, big and little endian encodings, etc. On top of them you get the executable conventions like others described, linking conventions, intermediate byte code like the one used by Java or LLVM IR used by GCC. Third you get conventions on how to find libraries, how to load them (see Java classloaders). As you go higher and higher in concepts you have new conventions that you consider as a given. That's why they didn't made it to the semantic versioning. They are implicit or collapsed in the major version. We could amend semantic versioning with <major>-<minor>-<patch>-<platform/ABI>. This is what is actually happening already: platform is already a rpm, dll, jar (JVM bytecode), war(jvm+web server), apk, 2.11 (specific Scala version) and so on. When you say APK you already talk about a specific ABI part of your API.

API can be ported to different ABI

The top level of an abstraction (the sources written against the highest API can be recompiled/ported to any other lower level abstraction.

Let's say I have some sources for rxscala. If the Scala tools are changed I can recompile them to that. If the JVM changes I could have automatic conversions from the old machine to the new one without bothering with the high level concepts. While porting might be difficult will help any other client. If a new operating system is created using a totally different assembler code a translator can be created.

APIs ported across languages

There are APIs that are ported in multiple languages like reactive streams. In general they define mappings to specific languages/platforms. I would argue that the API is the master specification formally defined in human language or even a specific programming language. All the other "mappings" are ABI in a sense, else more API than the usual ABI. The same is happening with the REST interfaces.

Google Play on Android 4.0 emulator

Have you ever tried Genymotion? I've read about it last week and it is great. They have several Android Images that you run (with their own software). The images are INCREDIBLY fast and they have Google Play installed on them. Check it out if it is the kind of thing that you need.

POST request via RestTemplate in JSON

This technique worked for me:

HttpHeaders headers = new HttpHeaders();

HttpEntity<String> entity = new HttpEntity<String>(requestJson, headers);
ResponseEntity<String> response = restTemplate.put(url, entity);

I hope this helps

How to search for a string in cell array in MATLAB?

Since 2011a, the recommended way is:

booleanIndex = strcmp('KU', strs)

If you want to get the integer index (which you often don't need), you can use:

integerIndex = find(booleanIndex);

strfind is deprecated, so try not to use it.

How do I tell whether my IE is 64-bit? (For that matter, Java too?)

Normally, you run IE 32 bit.
However, on 64-bit versions of Windows, there is a separate link in the Start Menu to Internet Explorer (64 bit). There's no real reason to use it, though.

In Help, About, the 64-bit version of IE will say 64-bit Edition (just after the full version string).

The 32-bit and 64-bit versions of IE have separate addons lists (because 32-bit addons cannot be loaded in 64-bit IE, and vice-versa), so you should make sure that Java appears on both lists.

In general, you can tell whether a process is 32-bit or 64-bit by right-clicking the application in Task Manager and clicking Go To Process. 32-bit processes will end with *32.

How to remove all of the data in a table using Django

Django 1.11 delete all objects from a database table -

Entry.objects.all().delete()  ## Entry being Model Name. 

Refer the Official Django documentation here as quoted below -

Note that delete() is the only QuerySet method that is not exposed on a Manager itself. This is a safety mechanism to prevent you from accidentally requesting Entry.objects.delete(), and deleting all the entries. If you do want to delete all the objects, then you have to explicitly request a complete query set:

I myself tried the code snippet seen below within my

    # for deleting model objects
    from django.db import connection
    def del_model_4(self):
        with connection.schema_editor() as schema_editor:

and within my i have a view that simply renders a html page ...

  def data_del_4(request):
      obj = calc_2() ## 
      return render(request, 'dc_dash/data_del_4.html') ## 

it ended deleting all entries from - model == model_4 , but now i get to see a Error screen within Admin console when i try to asceratin that all objects of model_4 have been deleted ...

ProgrammingError at /admin/dc_dash/model_4/
relation "dc_dash_model_4" does not exist
LINE 1: SELECT COUNT(*) AS "__count" FROM "dc_dash_model_4" 

Do consider that - if we do not go to the ADMIN Console and try and see objects of the model - which have been already deleted - the Django app works just as intended.

django admin screencapture

How to use stringstream to separate comma separated strings

#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int main()
    std::string input = "abc,def,   ghi";
    std::istringstream ss(input);
    std::string token;
    size_t pos=-1;
    while(ss>>token) {
      while ((pos=token.rfind(',')) != std::string::npos) {
        token.erase(pos, 1);
      std::cout << token << '\n';

How do I get TimeSpan in minutes given two Dates?

Why not just doing it this way?

DateTime dt1 = new DateTime(2009, 6, 1);
DateTime dt2 = DateTime.Now;
double totalminutes = (dt2 - dt1).TotalMinutes;

Hope this helps.

Modulo operator in Python

In addition to the other answers, the fmod documentation has some interesting things to say on the subject:

math.fmod(x, y)

Return fmod(x, y), as defined by the platform C library. Note that the Python expression x % y may not return the same result. The intent of the C standard is that fmod(x, y) be exactly (mathematically; to infinite precision) equal to x - n*y for some integer n such that the result has the same sign as x and magnitude less than abs(y). Python’s x % y returns a result with the sign of y instead, and may not be exactly computable for float arguments. For example, fmod(-1e-100, 1e100) is -1e-100, but the result of Python’s -1e-100 % 1e100 is 1e100-1e-100, which cannot be represented exactly as a float, and rounds to the surprising 1e100. For this reason, function fmod() is generally preferred when working with floats, while Python’s x % y is preferred when working with integers.

SQL Server after update trigger

Try this (update, not after update)

CREATE TRIGGER [dbo].[xxx_update] ON [dbo].[MYTABLE]

        SET mytable.CHANGED_ON = GETDATE()
            ,CHANGED_BY = USER_NAME(USER_ID())
        FROM inserted
        WHERE MYTABLE.ID = inserted.ID


How to make a HTML Page in A4 paper size page(s)?

I know that this subject is quite old but I want to share my experience about that topic. Actually, I was searching a module that can help me with my daily reports. I'm writting some documentations and some reports in HTML + CSS (instead of Word, Latex, OO, ...). The objectif would be to print them on A4 paper to share it with friends, ... Instead of searching, I decided to have a small funny coding session to implement a simple lib that can handle "pages", page number, summary, header, footer, .... Finally, I did it in ~~2h and I know that's not the best tool ever but it's almost ok for my purpose. You can take a look at this project on my repo and don't hesitate to share your ideas. It's maybe not what you are searching for at 100% but I think that this module can help you.

Basically I create a page of body "width: 200mm;" and container of height: 290mm (smaller than A4). Then I used page-break-after: always; so the "print" option of the browser know when to split pages.


What's the "Content-Length" field in HTTP header?

It's the number of bytes of data in the body of the request or response. The body is the part that comes after the blank line below the headers.

How to open port in Linux

First, you should disable selinux, edit file /etc/sysconfig/selinux so it looks like this:


Save file and restart system.

Then you can add the new rule to iptables:

iptables -A INPUT -m state --state NEW -p tcp --dport 8080 -j ACCEPT

and restart iptables with /etc/init.d/iptables restart

If it doesn't work you should check other network settings.

How to override the path of PHP to use the MAMP path?

The fact that the previously accepted answer refers to php 5.3.6, while the current version of MAMP ships with 7.2.1 as the default (as of early 2018), points out that this is not a very sustainable solution. You can make your path update automatically by adding an extra line to your .bash_profile or .zshrc to get the latest version of PHP from /Applications/MAMP/bin/php/ and export that to your path. Here’s how I do it:

# Use MAMP version of PHP
PHP_VERSION=`command ls /Applications/MAMP/bin/php/ | sort -n | tail -1`
export PATH=/Applications/MAMP/bin/php/${PHP_VERSION}/bin:$PATH

(Use source ~/.bash_profile after making your changes to make sure they take effect.)

As others have mentioned, you will likely also want to modify your shell to use MAMP’s mysql executable, which is located in /Applications/MAMP/Library/bin. However, I do not recommend exporting that folder, because there are a bunch of other executables there, like libtool, that you probably don’t want to be giving priority to over your system installed versions. This issue prevented me from installing a node package recently (libxmljs), as documented here.

My solution was to define and export mysql and mysqladmin as functions:

# Export MAMP MySQL executables as functions
# Makes them usable from within shell scripts (unlike an alias)
mysql() {
    /Applications/MAMP/Library/bin/mysql "$@"
mysqladmin() {
    /Applications/MAMP/Library/bin/mysqladmin "$@"
export -f mysql
export -f mysqladmin

I used functions instead of aliases, because aliases don’t get passed to child processes, or at least not in the context of a shell script. The only downside I’ve found is that running which mysql and which mysqladmin will no longer return anything, which is a bummer. If you want to check which mysql is being used and make sure everything is copacetic, use mysql --version instead.

Note: @julianromera points out that zsh doesn’t support exporting functions, so in that case, you’re best off using an alias, like alias mysql='/Applications/MAMP/Library/bin/mysql'. Just be aware that your aliases might not be available from subshells (like when executing a shell script).

C++ callback using class member

Instead of having static methods and passing around a pointer to the class instance, you could use functionality in the new C++11 standard: std::function and std::bind:

#include <functional>
class EventHandler
        void addHandler(std::function<void(int)> callback)
            cout << "Handler added..." << endl;
            // Let's pretend an event just occured

The addHandler method now accepts a std::function argument, and this "function object" have no return value and takes an integer as argument.

To bind it to a specific function, you use std::bind:

class MyClass

        // Note: No longer marked `static`, and only takes the actual argument
        void Callback(int x);
        int private_x;

    using namespace std::placeholders; // for `_1`

    private_x = 5;
    handler->addHandler(std::bind(&MyClass::Callback, this, _1));

void MyClass::Callback(int x)
    // No longer needs an explicit `instance` argument,
    // as `this` is set up properly
    cout << x + private_x << endl;

You need to use std::bind when adding the handler, as you explicitly needs to specify the otherwise implicit this pointer as an argument. If you have a free-standing function, you don't have to use std::bind:

void freeStandingCallback(int x)
    // ...

int main()
    // ...

Having the event handler use std::function objects, also makes it possible to use the new C++11 lambda functions:

handler->addHandler([](int x) { std::cout << "x is " << x << '\n'; });

Calendar date to yyyy-MM-dd format in java

public static void main(String[] args) {
    Calendar cal = Calendar.getInstance();
    cal.set(year, month, date);
    SimpleDateFormat format1 = new SimpleDateFormat("yyyy MM dd");
    String formatted = format1.format(cal.getTime());

Recover from git reset --hard?

Yes, YOU CAN RECOVER from a hard reset in git.


git reflog

to get the identifier of your commit. Then use:

git reset --hard <commit-id-retrieved-using-reflog>

This trick saved my life a couple of times.

You can find the documentation of reflog HERE.

How to change UIPickerView height

Even thought it is not resizing, another trick may help in the situation when the UIPicker is located at the bottom of the screen.

One can try moving it slightly downwards, but the central row should remain visible. This will help reveal some space above the picker since bottom rows will be offscreen.

I repeat that this is not the way of changing UIPicker view's height but some idea on what you can do if all other attempts fail.

Bootstrap modal opening on page load

Use a document.ready() event around your call.

$(document).ready(function () {



jsFiddle updated -

How do I unset an element in an array in javascript?

there is an important difference between delete and splice:


[<1 empty item>, 'one',<3 empty items>, 'five', <3 empty items>,'nine']

AFTER SPLICE (array.splice(1,1)):

[ <4 empty items>, 'five', <3 empty items>, 'nine' ]

AFTER DELETE (delete array[1]):

[ <5 empty items>, 'five', <3 empty items>, 'nine' ]

Creating a copy of a database in PostgreSQL

For those still interested, I have come up with a bash script that does (more or less) what the author wanted. I had to make a daily business database copy on a production system, this script seems to do the trick. Remember to change the database name/user/pw values.


if [ 1 -ne $# ]
  echo "Usage `basename $0` {tar.gz database file}"
  exit 65;

if [ -f "$1" ]
  EXTRACTED=`tar -xzvf $1`
  echo "using database archive: $EXTRACTED";
  echo "file $1 does not exist"
  exit 1


datestr=`date +%Y%m%d`

createdbcmd="CREATE DATABASE $dbname WITH OWNER = postgres ENCODING = 'UTF8' TABLESPACE = pg_default LC_COLLATE = 'en_US.UTF-8' LC_CTYPE = 'en_US.UTF-8' CONNECTION LIMIT = -1;"
dropdbcmp="DROP DATABASE $dbname"

echo "creating database $dbname"
psql -c "$createdbcmd"

if [[ $rc != 0 ]] ; then
  rm -rf "$EXTRACTED"
  echo "error occured while creating database $dbname ($rc)"
  exit $rc

echo "loading data into database"
psql $dbname < $EXTRACTED > /dev/null


rm -rf "$EXTRACTED"

if [[ $rc != 0 ]] ; then
  psql -c "$dropdbcmd"
  echo "error occured while loading data to database $dbname ($rc)"
  exit $rc

echo "finished OK"

The request failed or the service did not respond in a timely fashion?

After chasing this issue for some hours, we found an log in the SQL Server Agent logs stating the following:

This installation of SQL Server Agent is disabled. The edition of SQL server that installed this service does not support SQL server agent.

We were using SQL Server Express. After some Googling it appears SQL Server Express does not support SQL Server Agent.

I didn't find a direct piece of Microsoft communications stating that SQL Express doesn't support SQL Server Agent, however this sentiment seems to be echoed across many forums.

What programming language does facebook use?

Facebook uses the LAMP stack, so if you want to get a career with them you're going to want to focus on that. In addition they often have C++ and/or Java listed in their requirements as well.

One of the postings includes the following requirements:

  • Expertise with C++ and/or Java
  • Knowledge of Perl or PHP or Python
  • Knowledge of relational databases and SQL, preferably MySQL and Oracle


  • Expertise in PHP, JavaScript, and CSS.


  • Knowledge of Perl or PHP or Python
  • Knowledge of relational databases and
  • SQL, preferably MySQL Knowledge of
  • web technologies: XHTML, JavaScript Experience with C, C++ a plus


Also, do any other social networking sites use the same language?

Some other companys that use PHP/LAMP Stack:

How to recursively list all the files in a directory in C#?

In .NET 4.5, at least, there's this version that is much shorter and has the added bonus of evaluating any file criteria for inclusion in the list:

public static IEnumerable<string> GetAllFiles(string path, 
                                              Func<FileInfo, bool> checkFile = null)
    string mask = Path.GetFileName(path);
    if (string.IsNullOrEmpty(mask)) mask = "*.*";
    path = Path.GetDirectoryName(path);
    string[] files = Directory.GetFiles(path, mask, SearchOption.AllDirectories);

    foreach (string file in files)
        if (checkFile == null || checkFile(new FileInfo(file)))
            yield return file;

Use like this:

var list = GetAllFiles(mask, (info) => Path.GetExtension(info.Name) == ".html").ToList();

How can I parse a local JSON file from assets folder into a ListView?

Method to read JSON file from Assets folder and return as a string object.

public static String getAssetJsonData(Context context) {
            String json = null;
            try {
                InputStream is = context.getAssets().open("myJson.json");
                int size = is.available();
                byte[] buffer = new byte[size];
                json = new String(buffer, "UTF-8");
            } catch (IOException ex) {
                return null;

            Log.e("data", json);
            return json;


Now for parsing data in your activity:-

String data = getAssetJsonData(getApplicationContext());
        Type type = new TypeToken<Your Data model>() {
  <Your Data model> modelObject = new Gson().fromJson(data, type);

Build error, This project references NuGet

I also had this error I took this part of code from .csproj file:

 <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
        <ErrorText>This project references NuGet package(s) that are missing on this computer. Enable NuGet Package Restore to download them.  For more information, see The missing file is {0}.</ErrorText>
      <Error Condition="!Exists('$(SolutionDir)\.nuget\NuGet.targets')" Text="$([System.String]::Format('$(ErrorText)', '$(SolutionDir)\.nuget\NuGet.targets'))" />

Python Requests requests.exceptions.SSLError: [Errno 8] _ssl.c:504: EOF occurred in violation of protocol

Installing the "security" package extras for requests solved for me:

sudo apt-get install libffi-dev
sudo pip install -U requests[security]

Android ListView Selector Color

The list selector drawable is a StateListDrawable — it contains reference to multiple drawables for each state the list can be, like selected, focused, pressed, disabled...

While you can retrieve the drawable using getSelector(), I don't believe you can retrieve a specific Drawable from a StateListDrawable, nor does it seem possible to programmatically retrieve the colour directly from a ColorDrawable anyway.

As for setting the colour, you need a StateListDrawable as described above. You can set this on your list using the android:listSelector attribute, defining the drawable in XML like this:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="">
  <item android:state_enabled="false" android:state_focused="true"
        android:drawable="@drawable/item_disabled" />
  <item android:state_pressed="true"
        android:drawable="@drawable/item_pressed" />
  <item android:state_focused="true"
        android:drawable="@drawable/item_focused" />

Disabling Warnings generated via _CRT_SECURE_NO_DEPRECATE

i work on a multi platform project, so i can't use _s function and i don't want pollute my code with visual studio specific code.
my solution is disable the warning 4996 on the visual studio project. go to Project -> Properties -> Configuration properties -> C/C++ -> Advanced -> Disable specific warning add the value 4996.
if you use also the mfc and/or atl library (not my case) define before include mfc _AFX_SECURE_NO_DEPRECATE and before include atl _ATL_SECURE_NO_DEPRECATE.
i use this solution across visual studio 2003 and 2005.

p.s. if you use only visual studio the secure template overloads could be a good solution.

Android - Set text to TextView

Please correct the following line:

err = (TextView)findViewById(;


err = (TextView)findViewById(;

How can I view the shared preferences file using Android Studio?

You could simply create a special Activity for debugging purpose:

public void loadPreferences() {
// create a textview with id (tv_pref) in Layout.
TextView prefTextView;
prefTextView = (TextView) findViewById(;
    Map<String, ?> prefs = PreferenceManager.getDefaultSharedPreferences(
    for (String key : prefs.keySet()) {
        Object pref = prefs.get(key);
        String printVal = "";
        if (pref instanceof Boolean) {
            printVal =  key + " : " + (Boolean) pref;
        if (pref instanceof Float) {
            printVal =  key + " : " + (Float) pref;
        if (pref instanceof Integer) {
            printVal =  key + " : " + (Integer) pref;
        if (pref instanceof Long) {
            printVal =  key + " : " + (Long) pref;
        if (pref instanceof String) {
            printVal =  key + " : " + (String) pref;
        if (pref instanceof Set<?>) {
            printVal =  key + " : " + (Set<String>) pref;
        // Every new preference goes to a new line
        prefTextView.append(printVal + "\n\n");     
// call loadPreferences() in the onCreate of your Activity.

Structure of a PDF file?

Extracting text from PDF is a hard problem because PDF has such a layout-oriented structure. You can see the docs and source code of my barely-successful attempt on CPAN (my implementation is in Perl). The PDF data structure is very cool and well designed, but it's easier to write than read.

Using openssl to get the certificate from a server

While I agree with Ari's answer (and upvoted it :), I needed to do an extra step to get it to work with Java on Windows (where it needed to be deployed):

openssl s_client -showcerts -connect < /dev/null | openssl x509 -outform DER > derp.der

Before adding the openssl x509 -outform DER conversion, I was getting an error from keytool on Windows complaining about the certificate's format. Importing the .der file worked fine.

How to prevent form from submitting multiple times from client side?

<form onsubmit="if(submitted) return false; submitted = true; return true">

Easiest way to ignore blank lines when reading a file in Python

If you want you can just put what you had in a list comprehension:

names_list = [line for line in open("names.txt", "r").read().splitlines() if line]


all_lines = open("names.txt", "r").read().splitlines()
names_list = [name for name in all_lines if name]

splitlines() has already removed the line endings.

I don't think those are as clear as just looping explicitly though:

names_list = []
with open('names.txt', 'r') as _:
    for line in _:
        line = line.strip()
        if line:


Although, filter looks quite readable and concise:

names_list = filter(None, open("names.txt", "r").read().splitlines())

How to get current available GPUs in tensorflow?

Apart from the excellent explanation by Mrry, where he suggested to use device_lib.list_local_devices() I can show you how you can check for GPU related information from the command line.

Because currently only Nvidia's gpus work for NN frameworks, the answer covers only them. Nvidia has a page where they document how you can use the /proc filesystem interface to obtain run-time information about the driver, any installed NVIDIA graphics cards, and the AGP status.


Provide information about each of the installed NVIDIA graphics adapters (model name, IRQ, BIOS version, Bus Type). Note that the BIOS version is only available while X is running.

So you can run this from command line cat /proc/driver/nvidia/gpus/0/information and see information about your first GPU. It is easy to run this from python and also you can check second, third, fourth GPU till it will fail.

Definitely Mrry's answer is more robust and I am not sure whether my answer will work on non-linux machine, but that Nvidia's page provide other interesting information, which not many people know about.

jQuery $("#radioButton").change(...) not firing during de-selection

The change event not firing on deselection is the desired behaviour. You should run a selector over the entire radio group rather than just the single radio button. And your radio group should have the same name (with different values)

Consider the following code:

$('input[name="job[video_need]"]').on('change', function () {
    var value;
    if ($(this).val() == 'none') {
        value = 'hide';
    } else {
        value = 'show';

I have same use case as yours i.e. to show an input box when a particular radio button is selected. If the event was fired on de-selection as well, I would get 2 events each time.

Why isn't my Pandas 'apply' function referencing multiple columns working?

Seems you forgot the '' of your string.

In [43]: df['Value'] = df.apply(lambda row: my_test(row['a'], row['c']), axis=1)

In [44]: df
                    a    b         c     Value
          0 -1.674308  foo  0.343801  0.044698
          1 -2.163236  bar -2.046438 -0.116798
          2 -0.199115  foo -0.458050 -0.199115
          3  0.918646  bar -0.007185 -0.001006
          4  1.336830  foo  0.534292  0.268245
          5  0.976844  bar -0.773630 -0.570417

BTW, in my opinion, following way is more elegant:

In [53]: def my_test2(row):
....:     return row['a'] % row['c']

In [54]: df['Value'] = df.apply(my_test2, axis=1)

Laravel Eloquent ORM Transactions

If you want to use Eloquent, you also can use this

This is just sample code from my project

         * Saving Question
        $question = new Question;
        $questionCategory = new QuestionCategory;

         * Insert new record for question
        $question->title = $title;
        $question->user_id = Auth::user()->user_id;
        $question->description = $description;
        $question->time_post = date('Y-m-d H:i:s');

            $question->expired_time = Input::get('expiredtime');

        $questionCategory->category_id = $category;
        $questionCategory->time_added = date('Y-m-d H:i:s');

        DB::transaction(function() use ($question, $questionCategory) {


             * insert new record for question category
            $questionCategory->question_id = $question->id;

How to listen for changes to a MongoDB collection?

There is an working java example which can be found here.

 MongoClient mongoClient = new MongoClient();
    DBCollection coll = mongoClient.getDatabase("local").getCollection("");

    DBCursor cur = coll.find().sort(BasicDBObjectBuilder.start("$natural", 1).get())

    System.out.println("== open cursor ==");

    Runnable task = () -> {
        System.out.println("\tWaiting for events");
        while (cur.hasNext()) {
            DBObject obj =;
            System.out.println( obj );

    new Thread(task).start();

The key is QUERY OPTIONS given here.

Also you can change find query, if you don't need to load all the data every time.

BasicDBObject query= new BasicDBObject();
query.put("ts", new BasicDBObject("$gt", new BsonTimestamp(1471952088, 1))); //timestamp is within some range
query.put("op", "i"); //Only insert operation

DBCursor cur = coll.find(query).sort(BasicDBObjectBuilder.start("$natural", 1).get())

How to Set/Update State of StatefulWidget from other StatefulWidget in Flutter?

enter image description here

This examples shows calling a method

  1. Defined in Child widget from Parent widget.
  2. Defined in Parent widget from Child widget.

class ParentPage extends StatefulWidget {
  _ParentPageState createState() => _ParentPageState();

class _ParentPageState extends State<ParentPage> {
  final GlobalKey<ChildPageState> _key = GlobalKey();

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Parent")),
      body: Center(
        child: Column(
          children: <Widget>[
              child: Container(
                color: Colors.grey,
                width: double.infinity,
                child: RaisedButton(
                  child: Text("Call method in child"),
                  onPressed: () => _key.currentState.methodInChild(), // calls method in child
            Text("Above = Parent\nBelow = Child"),
              child: ChildPage(
                key: _key,
                function: methodInParent,

  methodInParent() => Fluttertoast.showToast(msg: "Method called in parent", gravity: ToastGravity.CENTER);

class ChildPage extends StatefulWidget {
  final Function function;

  ChildPage({Key key, this.function}) : super(key: key);

  ChildPageState createState() => ChildPageState();

class ChildPageState extends State<ChildPage> {
  Widget build(BuildContext context) {
    return Container(
      color: Colors.teal,
      width: double.infinity,
      child: RaisedButton(
        child: Text("Call method in parent"),
        onPressed: () => widget.function(), // calls method in parent

  methodInChild() => Fluttertoast.showToast(msg: "Method called in child");

Problem with SMTP authentication in PHP using PHPMailer, with Pear Mail works

This isn't on the code parter it's on the server side Contact your Server Manager or fix it from server if you own it If you use CPANEL/WHM GO TO WHM/SMTP RESTRICTIONS AND DISABLE IT

Auto margins don't center image in page

I remember someday that I spent a lot of time trying to center a div, using margin: 0 auto.

I had display: inline-block on it, when I removed it, the div centered correctly.

As Ross pointed out, it doesn't work on inline elements.

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

My Oracle is a bit rusty, but I think this would work:


Team Build Error: The Path ... is already mapped to workspace

Simplest way to do this is to go to your AppData and delete the TFS cache (depending on the version 3.0 or 4.0)

C:\Users{UserName}\AppData\Local\Microsoft\Team Foundation\3.0\Cache or C:\Users{UserName}\AppData\Local\Microsoft\Team Foundation\4.0\Cache

Find out the history of SQL queries

You can use this sql statement to get the history for any date:

SELECT * FROM V$SQL V where  to_date(v.FIRST_LOAD_TIME,'YYYY-MM-DD hh24:mi:ss') > sysdate - 60

Node.js throws "btoa is not defined" error

Here's a concise universal solution for base64 encoding:

const nodeBtoa = (b) => Buffer.from(b).toString('base64');
export const base64encode = typeof btoa !== 'undefined' ? btoa : nodeBtoa;