单例模式(饱汉式 饿汉式)

/*2011-9-18author:BearFly1990*/package designpattern;public class SingletonPattern {    private static SingletonPattern sp = null;    private SingletonPattern() {            }    public static synchronized SingletonPattern getInstance(){        if(sp == null){            sp = new SingletonPattern();        }        return sp;    }}class SingletonPattern2 {    private static SingletonPattern2 sp = new SingletonPattern2();    private SingletonPattern2() {            }    public static synchronized SingletonPattern2 getInstance(){        return sp;    }}