Re: Thread-safe Singleton Design Implementation

I was reading Wikipedia about Singleton Design pattern and it had some
sample codes for the implementation.

Under Java example implementation, there was "A thread-safe Java
programming language lazy-loaded solution." But I don't understand why
it is thread-safe & lazy-loaded solution. Could anyone explain it?

This is the source code from the Wikipedia (http://en.wikipedia.org/
wiki/Singleton_pattern) :
public class Singleton
{
  // Private constructor suppresses generation of a (public) default
constructor
  private Singleton() {}

  private static class SingletonHolder
  {
    private final static Singleton INSTANCE = new Singleton();
  }

  public static Singleton getInstance()
  {
    return SingletonHolder.INSTANCE;
  }
}