2.2.11同步synchronized方法无限等待与解决

Posted 2020-10-17 成功的路上总是离不开贵人的帮助，名师的指点和小人的刺激。

同步方法容易造成死循环。

package com.cky.bean;

/**
 * Created by edison on 2017/12/8.
 */
public class Service {

  synchronized  public void methodA(){
      System.out.println("methodA begin");
      boolean isContinueRun = true;
      while (isContinueRun) {

      }
      System.out.println("methodA end");
  }

  synchronized  public void methodB(){
      System.out.println("methodB begin");
      System.out.println("methodB end");
  }


}

package com.cky.thread;

import com.cky.bean.Service;

/**
 * Created by edison on 2017/12/8.
 */
public class ThreadA extends  Thread{
    private Service service;

    public ThreadA(Service service) {
        this.service = service;
    }

    @Override
    public void run() {
        super.run();
        service.methodA();
    }
}

package com.cky.thread;

import com.cky.bean.Service;

/**
 * Created by edison on 2017/12/8.
 */
public class ThreadB extends  Thread{


    private Service service;

    public ThreadB(Service service) {
        this.service = service;
    }

    @Override
    public void run() {
        super.run();
        service.methodB();
    }
}

package com.cky.test;

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

/**
 * Created by edison on 2017/12/8.
 */
public class Test {
    public static void main(String[] args) {
        Service service = new Service();
        ThreadA threadA = new ThreadA(service);
        threadA.setName("a");
        threadA.start();
        ThreadB threadB = new ThreadB(service);
        threadB.setName("b");
        threadB.start();

    }
}

methodA begin

Process finished with exit code 1

结果运行：

线程B永远得不到运行的机会，锁死了。

这时可以使用同步代码块来解决这样的问题

更改Service.java文件代码

package com.cky.bean;

/**
 * Created by edison on 2017/12/8.
 */
public class Service {

    Object object1 = new Object();
    public void methodA(){
        synchronized (object1) {
            System.out.println("methodA begin");
            boolean isContinueRun = true;
            while (isContinueRun) {

            }
            System.out.println("methodA end");
        }

  }
    Object object2 = new Object();
    public void methodB(){
        synchronized (object2) {
            System.out.println("methodB begin");
            System.out.println("methodB end");
        }

  }


}

methodA begin
methodB begin
methodB end

运行结果不再出现同步等待的情况。