Java 单例模式

Java 单例模式

1、饿汉模式：

package com.abin.info.service;

public class Singleton {
 private static Singleton singleton=new Singleton();
 
 private Singleton(){
  
 }
 
 public static Singleton getInstance(){
  return singleton;
 }

}

private static LazyMode lazyMode=null;

public static synchronized LazyMode getInstance(){

if(null==lazyMode){

lazyMode=new LazyMode();

}

return lazyMode;

} 

2、懒汉模式：

package com.abin.inter.she;

public class Singleton {
 private static Singleton singleton=null;
 private Singleton(){
  
 }
 public static Singleton getInstance(){
  if(null==singleton){
   return new Singleton();
  }
  return singleton;
 }

}

懒汉模式的线程安全版本：

package com.abin.lee.template.pattern;

public class LazyMode {

private static LazyMode lazyMode=null;

public static synchronized LazyMode getInstance(){

if(null==lazyMode){

lazyMode=new LazyMode();

}

return lazyMode;

} 

}

3、双重检测：

 

package com.east.abin.impl;

public class Singleton {
 private static Singleton instance=null;
 private Singleton(){
  
 }
 
 public static Singleton getInstance(){
  if(null==instance){
   synchronized(Singleton.class){
    if(null==instance){
     instance=new Singleton();
     return instance;
    }
   }
  }
  return instance;
 }

}

 

4.静态内部类：

单例模式创新！google的ioc作者写的。只有在调用的时候才会初始化！而且线程安全   

超级牛！

package com.east.abin.bin;

public class Singleton {
 private Singleton(){
  
 }
 
 private static class SingletonHelp{
  private static Singleton instance=new Singleton();
 }
 
 public static Singleton getInstance(){
  return SingletonHelp.instance;
 }
 

}

5、enum类型的(这个是针对jdk 1.5以及1.5版本以上的)

package com.abin.peng.service;

public enum Singleton {
 Singleton;
 private Singleton(){}
 public static Singleton getInstance(){
  return Singleton;
 }
}