单件模式 

 1 /**
 2  * 经典的单例模式实现
 3  */
 4 public class Singleton{
 5     private static Singleton uniqueInstance;
 6 
 7     private Singleton(){}
 8 
 9     public static Singleton getInstance(){
10         if(uniqueInstance == null){
11             uniqueInstance = new Singleton();
12         }
13         return uniqueInstance;
14     }
15 }
16 /**
17  * 单件模式确保一个类只有一个实例，并提供一个全局访问点
18  */
19     /*
20      * 处理多线程:
21      * 用synchronized修饰getInstance
22      * public static synchronized Singleton getInstance(){}
23      * 每次调用这个方法，同步是一种累赘
24      */
25 
26     /*
27      * 急切创建实例:JVM在加载这个类时马上创建唯一的单件实例
28      */
29 public class Singleton{
30     private static Singleton uniqueInstance = new Singleton();
31 
32     private Singleton(){}
33 
34     public static Singleton getInstance(){
35         return uniqueInstance;
36     }
37 }
38 /**
39  * 双重检查加锁
40  */
41 public class Singleton{
42     private volatile static Singleton uniqueInstance;
43 
44     private Singleton(){}
45 
46     public static Singleton getInstance(){
47         if(uniqueInstance == null){
48             synchronized(Singleton.class){
49             if(uniqueInstance == null)
50                 uniqueInstance = new Singleton();
51             }
52         }
53         return uniqueInstance;
54     }
55 }

 

posted @ 2014-04-09 09:59  soul390  阅读(117)  评论(0)    收藏  举报