设计模式——“signleton”

那天别人问了我一个问题，关于单例模式的，由于之前了解的都是蜻蜓点水，所以重新复习了一次重新总结。

单例模式的写法总的来说有5种：懒汉，恶汉，枚举，双重校验锁，静态内部类

懒汉

 1 public class Signleton{

 2         private static Signleton instance;

 3         private Signleton(){}

 4         public static synchronized Sginleton getInstance(){

 5              if( instance == null ){

 6                 instance = new Signleton();

 7              }

 8              return instance;

 9         }

10 }

恶汉:

 1 public class Singleton {

 2         private Singleton instance = null;

 3            static {

 4                instance = new Singleton();

 5            }

 6            private Singleton (){}

 7            public static Singleton getInstance() {

 8                return this.instance;

 9         }

10     }  

双重校验锁：

 1 public class Singleton {

 2             private volatile static Singleton singleton;

 3             private Singleton (){}

 4             public static Singleton getSingleton() {

 5                 if (singleton == null) {

 6                       synchronized (Singleton.class) {

 7                           if (singleton == null) {

 8                               singleton = new Singleton();

 9                           }

10                       }

11                 }

12                 return singleton;

13             }

14     }  

枚举：

1 public enum Singleton {

2         INSTANCE;

3         public void whateverMethod() {}

4     }

静态内部类：

1 public class Singleton {

2         private static class SingletonHolder {

3            private static final Singleton INSTANCE = new Singleton();

4         }

5         private Singleton (){}

6         public static final Singleton getInstance() {

7             return SingletonHolder.INSTANCE;

8         }

9 }  

有兴趣的可以看这篇文章: http://stackoverflow.com/questions/70689/what-is-an-efficient-way-to-implement-a-singleton-pattern-in-java
the
best way to do it is to use：
Since java5 ：
enum: 
Pre    java5 ：other

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