java线程同步-同步方法

线程的同步是保证多线程安全访问竞争资源的一种手段。

对于同步，在具体的Java代码中需要完成一下两个操作：

把竞争访问的资源标识为private；

同步哪些修改变量的代码，使用synchronized关键字同步方法或代码。

实例：

package com.du20150310Synchr;

public class Synchr {
    public static void main(String[] args) {
        User u = new User("张三",100);
        MyThread myThread1 = new MyThread("线程A",u,20);
        MyThread myThread2 = new MyThread("线程B",u,-20);
        MyThread myThread3 = new MyThread("线程C",u,60);
        MyThread myThread4 = new MyThread("线程D",u,-80);
        MyThread myThread5 = new MyThread("线程E",u,100);
        
        myThread1.start();
        myThread2.start();
        myThread3.start();
        myThread4.start();
        myThread5.start();
    }
    
}
class MyThread extends Thread{
    public MyThread() {
    }
    public MyThread(String name,User u, Integer y) {
        super(name);
        this.u = u;
        this.y = y;
    }

    private User u;
    private Integer y;
    @Override
    public void run() {
        u.oper(y);
    }
    
}
class User{
    public User() {
    }
    public User(String name, Integer result) {
        this.name = name;
        this.result = result;
    }
    private String name;
    private Integer result;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getResult() {
        return result;
    }
    public void setResult(Integer result) {
        this.result = result;
    }
    @Override
    public String toString() {
        return super.toString();
    }
    public synchronized void oper(int y){
        try {
            Thread.sleep(10);
            this.result = this.result + y;
            System.out.println(Thread.currentThread().getName()+"\t运行结束，增加"+"'"+y+"'"+"\t余额为："+this.result);
            Thread.sleep(10);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    
}

结果：