线程同步测试 线程安全问题

package com.day02;

/**
 * @author anyan
 * @date 2021/5/8-16:33
 */
/*
蛋糕类
 */
public class Cake {
    //蛋糕可以切成num块
    private int num;

    public Cake() {
    }

    public Cake(int num) {
        this.num = num;
    }


    public int getNum() {
        return num;
    }

    public void setNum(int num) {
        this.num = num;
    }
}

package com.day02;

/**
 * @author anyan
 * @date 2021/5/8-16:35
 */
/*
学生类
 */
public class Student extends Thread {
    //假设蛋糕可以切成12块
    Cake cake=new Cake(12);
    public Student(Cake cake) {
        this.cake = cake;
    }
    //学生吃蛋糕的方法,某学生对象吃n块
    public void eat(int n) throws Exception {
        //线程安全。为了使每个学生对象吃蛋糕同步，不并发执行学生线程对象
        synchronized(cake) {
            //起初蛋糕有t0块
            int t0 = cake.getNum();
            //学生对象吃完n块后有t1块
            int t1 = t0 - n;
            Thread.sleep(1000);
            //刷新蛋糕块数
            cake.setNum(t1);
        }
    }
    //学生开始吃蛋糕
    public void run(){
        int x=2;
        try {
            this.eat(x);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(currentThread().getName()+"吃蛋糕成功   剩余块数："+cake.getNum());
    }

}

package com.day02;

/**
 * @author anyan
 * @date 2021/5/8-16:57
 */
/*
测试学生吃蛋糕
 */
public class Test {
    public static void main(String[] args) {
        //创建一个蛋糕对象，假设分成12块
        Cake cake=new Cake(12);
        Cake cake2=new Cake(5);
        //创建两个线程对象，即学生对象，并且让其共享同一块蛋糕
        Student stu1=new Student(cake);
        Student stu2=new Student(cake);
        //stu3不参与同一块蛋糕
        Student stu3=new Student(cake2);
        stu1.setName("anyan");
        stu2.setName("ouyang");
        stu3.setName("tahuazi");
        stu1.start();
        stu2.start();
        stu3.start();

    }
}