java单例设计模式

 1 public class SingleDemo {
 2 
 3     public static void main(String[] args) {
 4         // TODO Auto-generated method stub
 5 
 6         Single2 s1 = Single2.getInstance();
 7         Single2 s2 = Single2.getInstance();
 8         System.out.println(s1 == s2);
 9         //输出true，说明对象为同一个，验证单例设计模式
10     }
11 
12 }
13 //饿汉式
14 class Single1
15 {
16     private Single1(){}
17     private static Single1 s = new Single1();
18     public static Single1 getInstance()
19     {
20         return s;
21     }
22 }
23 //懒汉式
24 class Single2
25 {
26     private Single2(){}
27     private static Single2 s = null;
28     public static Single2 getInstance()
29     {
30         if(s == null)
31             s = new Single2();
32         return s;
33     }
34 }