23种设计模式学习之单例模式

public class Singleton {
　　//私有构造方法，防止被实例化
    private Singleton(){}
　　//用一个内部类来维护单例 
    private static class SingletonFactory{
        private static Singleton singleton=new Singleton();
    }
　　//获取实例
    public static Singleton getInstance(){
        return SingletonFactory.singleton;
    }
}

public class Singleton {
    private static Singleton singleton=null;
    private Singleton(){}
    private static synchronized void syncInit() {
        if (singleton == null) {
            singleton = new Singleton();
        }
    }
    public static Singleton getInstance(){
        if (singleton == null){
            syncInit();
        }
        return singleton;
    }
}