设计模式之单例模式（懒汉式、饿汉式、双重检查）

转自：http://blog.csdn.net/hehe9737/article/details/7616224

 package Singleton;

 public class Persion1 {
     public static Persion1 persion=new Persion1();
     /**
      * 饿汉式单例
      */
     public static Persion1 getInstance()
     {
         return persion;
     }
     private int age;

     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }

 }

 package Singleton;

 public class Persion2 {
     public static Persion2 persion;
     /**
      * 懒汉式单例
      */
     public synchronized static Persion2 getInstance()
     {
         if(persion==null)
         {
             persion=new Persion2();
         }
         return persion;
     }
     private int age;

     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }

 }

 package Singleton;

 public class Persion3 {
     public static Persion3 persion;
     /**
      * 双重检查单例
      */
     public static Persion3 getInstance()
     {
         if(persion==null)
         {
             synchronized (Persion3.class) {
                 if(persion==null)
                 {
                     persion=new Persion3();
                 }
             }
         }
         return persion;
     }
     private int age;

     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }

 }

 package Singleton;



 public class SingletonT {

     /**测试方法
      * @param args
      */
     public static void main(String[] args) {
 //      饿汉式单例
         Persion1 p1=Persion1.getInstance();
         Persion1 p2=Persion1.getInstance();
         p1.setAge(12);
         p2.setAge(14);
         System.out.println("p1 :"+p1.getAge()+",p2 :"+p2.getAge());
 //      懒汉式单例类
         Persion2 p3=Persion2.getInstance();
         Persion2 p4=Persion2.getInstance();
         p3.setAge(15);
         p4.setAge(17);
         System.out.println("p3 :"+p3.getAge()+",p4 :"+p4.getAge());
 //      双重检查单例
         Persion3 p5=Persion3.getInstance();
         Persion3 p6=Persion3.getInstance();
         p5.setAge(18);
         p6.setAge(20);
         System.out.println("p5 :"+p5.getAge()+",p6 :"+p6.getAge());

     }

 }

运行结果：

p1 :14,p2 :14
p3 :17,p4 :17
p5 :20,p6 :20