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2.1.3多个对象多个锁

时间:2017-12-04 20:29:44      阅读:159      评论:0      收藏:0      [点我收藏+]

标签:data   jar   access   ash   launcher   enum   PFS   col   分析   

测试如下

package com.cky.bean;

/**
 * Created by chenkaiyang on 2017/12/4.
 */
public class SelfPrivateNum {
    int num =0;
   synchronized public void addI(String usrName) {
        try {
            if (usrName.equals("a")) {
                num  =100;
                System.out.println("a over");
                Thread.sleep(2000);
            } else {
                num= 200;
                System.out.println("b over");

            }
            System.out.println(usrName + " num="+ num);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
package com.cky.thread;

import com.cky.bean.SelfPrivateNum;

/**
 * Created by chenkaiyang on 2017/12/4.
 */
public class ThreadA  extends Thread{
    private SelfPrivateNum sn;
    public ThreadA (SelfPrivateNum sn) {
        this.sn = sn;
    }
    @Override
    public void run() {
        super.run();
        sn.addI("a");
    }
}
package com.cky.thread;

import com.cky.bean.SelfPrivateNum;

/**
 * Created by chenkaiyang on 2017/12/4.
 */
public class ThreadB extends Thread{
    private SelfPrivateNum sn;
    public ThreadB (SelfPrivateNum sn) {
        this.sn = sn;
    }
    @Override
    public void run() {
        super.run();
        sn.addI("b");
    }
}
package com.cky.test;

import com.cky.bean.SelfPrivateNum;
import com.cky.thread.ThreadA;
import com.cky.thread.ThreadB;

/**
 * Created by chenkaiyang on 2017/12/2.
 */
public class Test {
    public static void main(String[] args){
        SelfPrivateNum sn1 = new SelfPrivateNum();
        SelfPrivateNum sn2 = new SelfPrivateNum();
        ThreadA threadA = new ThreadA(sn1);
        ThreadB threadB = new ThreadB(sn2);
        threadA.start();
        threadB.start();
    }
}
D:\it\jdk1.8\bin\java -Didea.launcher.port=7535 "-Didea.launcher.bin.path=D:\it\idea\IntelliJ IDEA 2016.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\it\jdk1.8\jre\lib\charsets.jar;D:\it\jdk1.8\jre\lib\deploy.jar;D:\it\jdk1.8\jre\lib\ext\access-bridge-64.jar;D:\it\jdk1.8\jre\lib\ext\cldrdata.jar;D:\it\jdk1.8\jre\lib\ext\dnsns.jar;D:\it\jdk1.8\jre\lib\ext\jaccess.jar;D:\it\jdk1.8\jre\lib\ext\jfxrt.jar;D:\it\jdk1.8\jre\lib\ext\localedata.jar;D:\it\jdk1.8\jre\lib\ext\nashorn.jar;D:\it\jdk1.8\jre\lib\ext\sunec.jar;D:\it\jdk1.8\jre\lib\ext\sunjce_provider.jar;D:\it\jdk1.8\jre\lib\ext\sunmscapi.jar;D:\it\jdk1.8\jre\lib\ext\sunpkcs11.jar;D:\it\jdk1.8\jre\lib\ext\zipfs.jar;D:\it\jdk1.8\jre\lib\javaws.jar;D:\it\jdk1.8\jre\lib\jce.jar;D:\it\jdk1.8\jre\lib\jfr.jar;D:\it\jdk1.8\jre\lib\jfxswt.jar;D:\it\jdk1.8\jre\lib\jsse.jar;D:\it\jdk1.8\jre\lib\management-agent.jar;D:\it\jdk1.8\jre\lib\plugin.jar;D:\it\jdk1.8\jre\lib\resources.jar;D:\it\jdk1.8\jre\lib\rt.jar;F:\springboot\threaddemo\out\production\threaddemo;D:\it\idea\IntelliJ IDEA 2016.3.3\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test
a over
b over
b num=200
a num=100

Process finished with exit code 0

结果分析:本测试实例化了2个对象,分别开启两个线程进行访问,效果却不是同步执行的,而是异步执行,因为本实例创建了2个锁,虽然使用了synchronized关键字,但是打印顺序不是同步的,而是交叉的。

关键字synchronized取得的锁是对象锁,而非一段代码或方法的锁,哪个线程先执行该关键字的方法,哪个线程就持有该方法所属的对象的锁lock,此时其他线程等待,前提也是多个线程访问同一个对象。

如果多个线程访问的是多个对象,那么JVM会创建多个锁。

2.1.3多个对象多个锁

标签:data   jar   access   ash   launcher   enum   PFS   col   分析   

原文地址:http://www.cnblogs.com/edison20161121/p/7967427.html

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