SingletonDecorator

A DecoratorPattern on SingletonDecorator.

public class SingletonDecorator implements Singleton {

	private Singleton singleton;
	private static String DEFAULT = "ConcreteSingleton1";

	private static String getDefault() {
	return DEFAULT;
	}

	public SingletonDecorator() {
	this(getDefault());
	}

	public SingletonDecorator(final String which) {
	this(SingletonRegistry.getSingleton(which));
	}

	public SingletonDecorator(final Singleton singleton) {
	this.singleton = singleton;
	}

	public Singleton getInstance() {
	return singleton;
	}

	// decorator interfaced methods.

}

SingletonRegistry is just a facade for Singleton creation.