Design pattern--Singleton

What is a singleton pattern? How do you code it in Java?

 

A singleton is a class that can be instantiated only one time in a JVM per class loader. Repeated calls always return the same instance. Ensures that a class has only one instance, and provide a global point of access. It can be an issue if singleton class gets loaded by multiple class loaders or JVMs.

 

Code:

public class Singleton { private static Singleton one = new Singleton(); // private constructor. This class cannot be instantiated from outside and // prevents subclassing. private Singleton(){} public static Singleton getInstance() { return one; } }