对象及变量的并发访问-----synchronized同步----- 锁可重入

Posted 2020-10-10

一、一个类中的一个synchronized方法调用本类中其他的synchronized方法，可以得到锁的

　　类中synchronized方法一调用本类中synchronized方法二

package service;

/**
 * Created by zhc on 2017/10/10
 */
public class Service3 {
    synchronized public void service1(){
        System.out.println("service1");
        service2();
    }

    synchronized public void service2(){
        System.out.println("service2");
    }
}

　　thread的run方法中实例Service，调用service1方法

package extthread;

import service.Service3;

/**
 * Created by zhc on 2017/10/10
 */
public class ThreadD extends Thread{
    @Override
    public void run() {
        super.run();
        Service3 service = new Service3();
        service.service1();
    }
}

　　run

package test;

import extthread.ThreadD;

/**
 * Created by zhc on 2017/10/10
 */
public class Run3 {
    public static void main(String[] args) {
        ThreadD thread = new ThreadD();
        thread.start();
    }
}

　　测试结果：

　　service1
　　service2

　　synchronized修饰的方法可以调用本类中其他的synchronized方法

二、可重入锁还可以用父子类继承的环境中

　　父类

package service;

/**
 * Created by zhc on 2017/10/10
 */
public class Father {
    public int i = 10;
    synchronized public void operate(){
        try {
            i--;
            System.out.println("main print i =" + i);
            Thread.sleep(200);
        }catch (InterruptedException e){
            e.printStackTrace();
        }
    }
}

　　子类

package service;

/**
 * Created by zhc on 2017/10/10
 */
public class Son extends Father {
    synchronized public void operateSon() {
        try {
            while (i>0){
                i--;
                System.out.println("son print i "+i);
                Thread.sleep(100);
                this.operate();
            }
        }catch (InterruptedException e){
            e.printStackTrace();
        }
    }
}

　　线程调用子类方法

package extthread;

import service.Son;

/**
 * Created by zhc on 2017/10/10
 */
public class ThreadE extends Thread {
    @Override
    public void run() {
        super.run();
        Son son = new Son();
        son.operateSon();
    }
}

　　run

package test;

import extthread.ThreadE;

/**
 * Created by zhc on 2017/10/10
 */
public class Run4 {

    public static void main(String[] args) {
        ThreadE t = new ThreadE();
        t.start();
    }
}

　　测试结果：

　　son print i 9
　　main print i =8
　　son print i 7
　　main print i =6
　　son print i 5
　　main print i =4
　　son print i 3
　　main print i =2
　　son print i 1
　　main print i =0