Singleton Decorator

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.