常用设计模式之单例

• Code

 1 // 饿汉式
 2 public class Singleton{
 3 private Singleton(){}
 4 private static final Singleton instance = new Singleton();
 5 public static Singleton getInstance(){
 6     return instance ;
 7 }
 8 }
 9 // 静态代码块
10  public class Singleton {
11       private Singleton instance = null;
12       static {
13            instance = new Singleton();
14      }
15       private Singleton (){}
16       public static Singleton getInstance() {
17          return this.instance;
18        }
19 }
20
21 // 懒汉式 在getInstance方法上加同步
22 public class Singleton {
23     private Singleton() {}
24     private static Singleton single=null;
25     public static synchronized Singleton getInstance() {
26          if (single == null) {
27              single = new Singleton();
28          }
29         return single;
30     }
31 }
32 // 懒汉式 双重检查锁定
33 public class Singleton {
34     private Singleton() {}
35     private static Singleton single=null;
36     public static Singleton getInstance() {
37         if (singleton == null) {
38             synchronized (Singleton.class) {
39                if (singleton == null) {
40                   singleton = new Singleton();
41                }
42             }
43         }
44         return singleton;
45     }
46 }
47 // 静态内部类
48 public class Singleton {
49     private static class LazyHolder {
50        private static final Singleton INSTANCE = new Singleton();
51     }
52     private Singleton (){}
53     public static final Singleton getInstance() {
54        return LazyHolder.INSTANCE;
55     }
56 } 

参考：

http://www.blogjava.net/kenzhh/archive/2013/03/15/357824.html