章10——面向对象编程（高级部分）——两种单例模式

代码如下：

//单例模式
//instance--实例
//该篇中记录了饿汉模式和懒汉模式
public class HungryMan {public static void main(String[] args) {Single01.say();Single02.say();}
}class Single01{//只能有instance这一个实例。private Single01(){System.out.println("01created");};//private static Single01(){};private static Single01 instance = new Single01();public static Single01 getInstance(){return instance;}public static void say(){System.out.println("hello!");}}class Single02{private Single02(){System.out.println("02created");}private static Single02 instance = null;public static Single02 getInstance(){if(instance==null){instance = new Single02();}return instance;}public static void say(){System.out.println("HELLO!");}
}

两者区别如下：