Java进阶之多线程：死锁

学习狂神视频的第七天

Java进阶之多线程：死锁

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前言：

死锁：多个线程互相抱着对方需要的资源，然后形成僵持。

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一、死锁样例

public class DeadLock {
    public static void main(String[] args) {
        Makeup g1 = new Makeup(0,"灰姑娘");
        Makeup g2 = new Makeup(1,"白雪公主");

        g1.start();
        g2.start();
    }
}

// 口红
class Lipstick{

}
//镜子
class Mirror{

}
class Makeup extends Thread{
    //需要的资源只有一份,用static来保证只有一份
    static Lipstick lipstick = new Lipstick();
    static Mirror mirror = new Mirror();

    int choice;//选择
    String girlName;// 使用化妆品的人

    Makeup(int choice,String girlName){
        this.choice = choice;
        this.girlName = girlName;
    }
    @Override
    public void run(){
        // 化妆
        makeup();
    }

    private void makeup(){
        if(choice == 0){
            synchronized (lipstick){// 获得口红的锁
                System.out.println(this.girlName+"获得口红的锁");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                synchronized (mirror) {// 一秒钟后想获得镜子
                    System.out.println(this.girlName + "获得镜子的锁");
                }
            }
        } else {
            synchronized (mirror){// 获得镜子的锁
                System.out.println(this.girlName+"获得镜子的锁");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                synchronized (lipstick) {// 一秒钟后想获得镜子
                    System.out.println(this.girlName + "获得镜子的锁");
                }
            }
        }
    }
}

结果

二、解决死锁

public class DeadLock {
    public static void main(String[] args) {
        Makeup g1 = new Makeup(0,"灰姑娘");
        Makeup g2 = new Makeup(1,"白雪公主");

        g1.start();
        g2.start();
    }
}

// 口红
class Lipstick{

}
//镜子
class Mirror{

}
class Makeup extends Thread{
    //需要的资源只有一份,用static来保证只有一份
    static Lipstick lipstick = new Lipstick();
    static Mirror mirror = new Mirror();

    int choice;//选择
    String girlName;// 使用化妆品的人

    Makeup(int choice,String girlName){
        this.choice = choice;
        this.girlName = girlName;
    }
    @Override
    public void run(){
        // 化妆
        makeup();
    }

    private void makeup(){
        if(choice == 0){
            synchronized (lipstick){// 获得口红的锁
                System.out.println(this.girlName+"获得口红的锁");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
/*
                synchronized (mirror) {// 一秒钟后想获得镜子
                    System.out.println(this.girlName + "获得镜子的锁");
                }*/
            }
            synchronized (mirror) {// 一秒钟后想获得镜子
                System.out.println(this.girlName + "获得镜子的锁");
            }
        } else {
            synchronized (mirror){// 获得镜子的锁
                System.out.println(this.girlName+"获得镜子的锁");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

/*                synchronized (lipstick) {// 一秒钟后想获得镜子
                    System.out.println(this.girlName + "获得镜子的锁");
                }*/
            }
            synchronized (lipstick) {// 一秒钟后想获得镜子
                System.out.println(this.girlName + "获得口红的锁");
            }
        }
    }
}

结果