java设计模式---单例模式

public class SingletonSun{
    private static SingletonSun sun=null;//staic 把sun作为一个类变量
    public SingletonSun(){

    }
    public static synchronized  Singleton getInstance(){//加synchronized 可以保证获取单例的时候线程安全
    if(sun==null){
            sun=new SingletonSun();
        }
        return sun;
    }
}

/**
*恶汉单例一定是线程安全的
*/
public class SingletonSun{
    private static final SinglentonSun sun=new SinglentonSun();
    public SinglentonSun(){};
    public SinglentonSun getInstance(){
        return sun;
    }
}