单例模式

 1 package designPattern;
 2 /**
 3  * 单例模式
 4  */
 5 public class A1_SingletonTest {
 6 
 7     public static void main(String[] args) {
 8         Singleton s1 = Singleton.getInstance();
 9         Singleton s2 = Singleton.getInstance();
10         if (s1 == s2) {
11             System.out.println("单例模式!");
12         }else {
13             System.out.println("不是单例模式...");
14         }
15     }
16 }
17 
18 class Singleton
19 {
20     private static Singleton s;;
21     
22     private Singleton() {}
23 
24     public static Singleton getInstance()
25     {
26         if (s==null) {
27             s = new Singleton();
28         }
29         return s;
30     }
31 }