package headfirst.singleton.dcl;//// Danger!  This implementation of Singleton not// guaranteed to work prior to Java 5//public class Singleton {	private volatile static Singleton uniqueInstance; 	private Singleton() {} 	public static Singleton getInstance() {		if (uniqueInstance == null) {			synchronized (Singleton.class) {				if (uniqueInstance == null) {					uniqueInstance = new Singleton();				}			}		}		return uniqueInstance;	}}