Tutorial by Examples: all

Sometimes, programmers who are new Java will use primitive types and wrappers interchangeably. This can lead to problems. Consider this example: public class MyRecord { public int a, b; public Integer c, d; } ... MyRecord record = new MyRecord(); record.a = 1; // OK ...

SELECT s.name + '.' + t.NAME AS TableName, SUM(a.used_pages)*8 AS 'TableSizeKB' --a page in SQL Server is 8kb FROM sys.tables t JOIN sys.schemas s on t.schema_id = s.schema_id LEFT JOIN sys.indexes i ON t.OBJECT_ID = i.object_id LEFT JOIN sys.partitions p ON i.object_id = ...

Since JUnit is a Java library, all you have to do to install it is to add a few JAR files into the classpath of your Java project and you're ready to go. You can download these two JAR files manually: junit.jar & hamcrest-core.jar. If you're using Maven, you can simply add in a dependency into...

Caller info attributes can be used to pass down information about the invoker to the invoked method. The declaration looks like this: using System.Runtime.CompilerServices; public void LogException(Exception ex, [CallerMemberName]string callerMemberName = "", ...

In themes.xml: <style name="AppTheme" parent="Theme.AppCompat"> <!-- Theme attributes here --> </style> In AndroidManifest.xml: <application android:icon="@mipmap/ic_launcher" android:label="@string/app_name" andr...

Have required JavaScript and CSS files included in your index.html. You can do this by either using the CDN files availiable at the following paths: <link rel="stylesheet" type="text/css" href="//cdn.datatables.net/1.10.12/css/jquery.dataTables.css"> <scr...

XML elements often nest, have data in attributes and/or as character data. The way to capture this data is by using ,attr and ,chardata respectively for those cases. var doc = ` <parent> <child1 attr1="attribute one"/> <child2>and some cdata</child2> </p...

Directives comes with the AngularJS library itself. A sample directive can be created as: angular.module('simpleDirective', []) .directive('helloData', function() { return { template: 'Hello, {{data}}' }; }); And can be used as: JS: angular.module('app', ['simpleDirective']) .con...

You can install Json.Net into your Visual Studio Project in 1 of 2 ways. Install Json.Net using the Package Manager Console. Open the Package Manager Console window in Visual Studio either by typing package manager console in the Quick Launch box and selecting it or by clicking View -> O...

Requirements Python (2.7, 3.2, 3.3, 3.4, 3.5, 3.6) Django (1.7+, 1.8, 1.9, 1.10, 1.11) Install You can either use pip to install or clone the project from github. Using pip: pip install djangorestframework Using git clone: git clone [email protected]:tomchristie/django-rest-framew...

A dotfile is a file whose names begin with a .. These are normally hidden by ls and not listed unless requested. For example the following output of ls: $ ls bin pki The -a or --all option will list all files, including dotfiles. $ ls -a . .ansible .bash_logout .bashrc .lesshst ...

It is possible to await multiple calls concurrently by first invoking the awaitable tasks and then awaiting them. public async Task RunConcurrentTasks() { var firstTask = DoSomethingAsync(); var secondTask = DoSomethingElseAsync(); await firstTask; await secondTask; } Alt...

If you want two or more arguments to be mutually exclusive. You can use the function argparse.ArgumentParser.add_mutually_exclusive_group(). In the example below, either foo or bar can exist but not both at the same time. import argparse parser = argparse.ArgumentParser() group = parser.add_mut...

If an iterator method has a yield inside a try...finally, then the returned IEnumerator will execute the finally statement when Dispose is called on it, as long as the current point of evaluation is inside the try block. Given the function: private IEnumerable<int> Numbers() { yield re...

Detailed instructions on getting android-activity set up or installed.

Detailed instructions on getting openerp set up or installed in Debian/Ubuntu. To install from source code, we need Python 2.7, Git and a PostgreSQL database: $ sudo apt-get install git python-pip python2.7-dev -y $ sudo apt-get install postgresql -y $ sudo su -c "createuser -s $(whoami)&qu...

Imagine the following XML: <root> <element>hello</element> <another> hello </another> <example>Hello, <nested> I am an example </nested>.</example> </root> The following XPath expression: //*[text() = 'hel...

Using the Control.Invoke() method you may move the execution of a method or function from a background thread to the thread that the control was created on, which is usually the UI (User Interface) thread. By doing so your code will be queued to run on the control's thread instead, which removes the...

# no error, even the subscript is out of range. julia> sub2ind((3,3), 3, 4) 12 One cannot determine whether a subscript is in the range of an array by comparing its index: julia> sub2ind((3,3), -1, 2) 2 julia> 0 < sub2ind((3,3), -1, 2) <= 9 true

You should use caution when using setState in an asynchronous context. For example, you might try to call setState in the callback of a get request: class MyClass extends React.Component { constructor() { super(); this.state = { user: {} }; } ...