The Singleton design pattern in Java

In Java, sometimes it can be useful to have exactly one instance of a class. This is known as a Singleton pattern. A logger, print spooler, or window manager would be potential uses for this.

In essence, a Singleton ensures that a class has a single instance, and a global point of access to it. The class declaration typically looks like this:

public class mySingleton { private static mySingleton instance = null; protected mySingleton() { // Protected constructor to prevent instantiation. } public static mySingleton getInstance() { if(instance == null) { instance = new mySingleton(); } return instance; } }

For a much more in-depth guide to this design pattern, check out http://www.javaworld.com/article/2073352/core-java/simply-singleton.html