1 /* 2  * 设计模式之单例模式的简单demo 3  */ 4 class Single 5 { 6     /* 7      * 创建一个本类对象。 8      * 和get/set方法思想一样，类不能直接调用对象 9      * 所以用private限制权限10      */11     private static Single s = new Single();12     /*13      * 构造函数私有化目的是为了只能产生一个对象14      */15     private Single(){}16     // 定义一个方法返回该对象，让外部可以调用。17     public static Single getInstance()18     {19         return s;20     }21 }22 23 class  SingleDemo24 {25     public static void main(String[] args) 26     {27 //        Single s = Single.s;28         Single s1 = Single.getInstance();29         Single s2 = Single.getInstance();30         System.out.println(s1 == s2);31     }32 }

/* * 单例模式之饿汉式与懒汉式 */ //饿汉式class Single{    private static Single s = new Single();    private Single(){}    public static Single getInstance()    {        return s;    }}//懒汉式class Single {    private static Single s = null;    private Single(){}    public static Single getInstance()    {        if (s == null)        {            s = new Single();        }        return s;    }}

1 /* 2  * 单例模式的小例子 3  */ 4 class SuperMan 5 { 6     private String name; 7  8     private static SuperMan man = new SuperMan("Clarke"); 9 10     private SuperMan (String name)11     {12         this.name = name;13     }14 15     public static SuperMan getInstance () 16     {17         return man;18     }19 20     public void setName(String name)21     {22         this.name = name;23     }24     public String getName()25     {26         return this.name;27     }28 }29 30 class SuperManDemo 31 {32     public static void main(String[] args) 33     {34         SuperMan s1 = SuperMan.getInstance();35         String name1 = s1.getName();36         System.out.println("name1 = " + name1);37 38         SuperMan s2 = SuperMan.getInstance();39         s2.setName("hero");40         String name2 = s2.getName();41         System.out.println("name2 = " + name2);42     }43 }