java 多线程的单例模式,Java多线程中的单例模式两种实现方式

Java多线程中的单例模式

一、在多线程环境下创建单例

方式一：

package com.ietree.multithread.sync;

public class Singletion {

private static class InnerSingletion {

private static Singletion single = new Singletion();

}

public static Singletion getInstance() {

return InnerSingletion.single;

}

}

方式二：

package com.ietree.multithread.sync;

public class DubbleSingleton {

private static DubbleSingleton ds;

public static DubbleSingleton getDs() {

if (ds == null) {

try {

// 模拟初始化对象的准备时间...

Thread.sleep(3000);

} catch (InterruptedException e) {

e.printStackTrace();

}

synchronized (DubbleSingleton.class) {

if (ds == null) { // 这个判断很重要，如果没有那将不是单例，而是多例

ds = new DubbleSingleton();

}

}

}

return ds;

}

public static void main(String[] args) {

Thread t1 = new Thread(new Runnable() {

@Override

public void run() {

System.out.println(DubbleSingleton.getDs().hashCode());

}

}, "t1");

Thread t2 = new Thread(new Runnable() {

@Override

public void run() {

System.out.println(DubbleSingleton.getDs().hashCode());

}

}, "t2");

Thread t3 = new Thread(new Runnable() {

@Override

public void run() {

System.out.println(DubbleSingleton.getDs().hashCode());

}

}, "t3");

t1.start();

t2.start();

t3.start();

}

}

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