Java多線程中的單例模式

標籤：多線程   pack   blog   java   類比   exception   nts   方式   turn   

一、在多線程環境下建立單例

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 {                // 類比初始化對象的準備時間...                Thread.sleep(3000);            } catch (InterruptedException e) {                e.printStackTrace();            }            synchronized (DubbleSingleton.class) {                if (ds == null) { // 這個判斷很重要，如果沒有那將不是單例，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();    }}

 

Java多線程中的單例模式