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This type of Singleton is thread safe, and prevents unnecessary locking after the Singleton instance has been created. Java SE 5 public class MySingleton { // instance of class private static volatile MySingleton instance = null; // Private constructor private MySingleton()...

As shown in Declaring Namespaces, we can define a class in a namespace as follows: namespace MyProject\Shapes; class Rectangle { ... } To reference this class the full path (including the namespace) needs to be used: $rectangle = new MyProject\Shapes\Rectangle(); This can be shortened by ...

Install .NET Core on macOS 10.11+, after install homebrew: brew update brew install openssl mkdir -p /usr/local/lib ln -s /usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib /usr/local/lib/ ln -s /usr/local/opt/openssl/lib/libssl.1.0.0.dylib /usr/local/lib/ Install .NET Core SDK from https://go...

When defining discriminated unions you can name elements of tuple types and use these names during pattern matching. type Shape = | Circle of diameter:int | Rectangle of width:int * height:int let shapeIsTenWide = function | Circle(diameter=10) | Rectangle(width=10) -> t...

To use Vagrant on Windows platform you need to install virtualization software and an ssh command-line tool first. This example will use freeware VirtualBox and Cygwin. Install VirtualBox Download the latest VirtualBox version from the official download page and run the downloaded file. Note that ...

5 <input type="month" /> Dependent on browser support, a control will show to pick the month.

Setup for Yii 1.1 Step 1 - downloading Yii Download the Yii framework bundle from the Yii website Inside the downloaded bundle there are 3 folders, namely: demos framework requirements demos, as the name suggests contains a number of demo Yii applications. framework contains the Yii framew...

To create a pure JSON table you need to provide a single field with the type JSONB: CREATE TABLE mytable (data JSONB NOT NULL); You should also create a basic index: CREATE INDEX mytable_idx ON mytable USING gin (data jsonb_path_ops); At this point you can insert data in to the table and que...

Taking a complex JSON document in a table: CREATE TABLE mytable (data JSONB NOT NULL); CREATE INDEX mytable_idx ON mytable USING gin (data jsonb_path_ops); INSERT INTO mytable VALUES($$ { "name": "Alice", "emails": [ "[email protected]", ...

Creation of a Button is simple: Button sampleButton = new Button(); This will create a new Button without any text or graphic inside. If you want to create a Button with a text, simply use the constructor that takes a String as parameter (which sets the textProperty of the Button): Button samp...

The current stable version of scikit-learn requires: Python (>= 2.6 or >= 3.3), NumPy (>= 1.6.1), SciPy (>= 0.9). For most installation pip python package manager can install python and all of its dependencies: pip install scikit-learn However for linux systems it is recomm...

The D programming language's standard compiler DMD can run on all major platforms. To install DMD see here. To install by command line you may run the command (found on the D website): curl -fsS https://dlang.org/install.sh | bash -s dmd Package Managers Arch Linux pacman -S dlang Chocolate...

SWI-Prolog Windows and Mac: Download SWI-Prolog at the official website Simply install by following the installer instructions. Linux (PPA): Add the PPA ppa:swi-prolog/stable to your system’s software sources (developers may choose for ppa:swi-prolog/devel) : Open a terminal (Ctrl+...

If you don't have any RubyGems installed, there is still the pre-gem approach to getting software, doing it manually: Download from RubyGems Unpack into a directory and cd there Install with: ruby setup.rb (you may need admin/root privilege) sudo ruby setup.rb For more details...

Strings in JavaScript can be enclosed in Single quotes 'hello', Double quotes "Hello" and (from ES2015, ES6) in Template Literals (backticks) `hello`. var hello = "Hello"; var world = 'world'; var helloW = `Hello World`; // ES2015 / ES6 Strings can be created...

Swift //System Font textView.font = UIFont.systemFont(ofSize: 12) //Font of your choosing textView.font = UIFont(name: "Font Name", size: 12) Objective-C //System Font textView.font = [UIFont systemFontOfSize:12]; //Font of your choosing textView.font = [UIFont fontWithName:...

To keep a container running in the background, supply the -d command line option during container startup: docker run -d busybox top The option -d runs the container in detached mode. It is also equivalent to -d=true. A container in detached mode cannot be removed automatically when it stops, t...

A Docker volume is a file or directory which persists beyond the lifetime of the container. It is possible to mount a host file or directory into a container as a volume (bypassing the UnionFS). Add a volume with the -v command line option: docker run -d -v "/data" awesome/app bootstrap....

fn to_test(output: bool) -> bool { output } #[cfg(test)] // The module is only compiled when testing. mod test { use super::to_test; // This function is a test function. It will be executed and // the test will succeed if the function exits cleanly. #[test] fn...

Lets assume we have some Film model: public class Film { public string Title { get; set; } public string Category { get; set; } public int Year { get; set; } } Group by Category property: foreach (var grp in films.GroupBy(f => f.Category)) { var groupCategory = grp.Key; ...