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多线程之死锁、生产者与消费者模型以及线程池

死锁产生的四个必要条件
  • 互斥条件:一个资源每次只能被一个进程使用

  • 请求与保持条件:一个进程因请求资源而阻塞时,对已获得的资源保持不放

  • 不剥夺条件:进程已获得的资源,在未使用完之前,不能强制剥夺

  • 循环等待条件:若干进程之间形成一种头尾相接的循环等待资源关系

实例
package com.yeyue.thread;
?
public class DeadLock {
    public static void main(String[] args) {
        new Makeup(0,"灰姑凉").start();
        new Makeup(1,"白雪公主").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;
    String girlName;
?
    Makeup(int choice, String girlName) {
        this.choice = choice;
        this.girlName = girlName;
    }
?
    @Override
    public void run() {
        try {
            makeup();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
?
    private void makeup() throws InterruptedException {
        if (choice == 0) {
            synchronized (lipstick) {
                System.out.println(this.girlName + "获得了口红的锁");
                Thread.sleep(1000);
                synchronized (mirror) {
                    System.out.println(this.girlName + "获得了镜子的锁");
                }
            }
        } else {
            synchronized (mirror) {
                System.out.println(this.girlName + "获得了镜子的锁");
                Thread.sleep(1000);
                synchronized (lipstick) {
                    System.out.println(this.girlName + "获得了口红的锁");
                }
            }
        }
    }
}
避免死锁
package com.yeyue.thread;
?
public class DeadLock {
    public static void main(String[] args) {
        new Makeup(0,"灰姑凉").start();
        new Makeup(1,"白雪公主").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;
    String girlName;
?
    Makeup(int choice, String girlName) {
        this.choice = choice;
        this.girlName = girlName;
    }
?
    @Override
    public void run() {
        try {
            makeup();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
?
    private void makeup() throws InterruptedException {
        if (choice == 0) {
            synchronized (lipstick) {
                System.out.println(this.girlName + "获得了口红的锁");
                Thread.sleep(1000);
                }
            synchronized (mirror) {
                System.out.println(this.girlName + "获得了镜子的锁");
            }
        } else {
            synchronized (mirror) {
                System.out.println(this.girlName + "获得了镜子的锁");
                Thread.sleep(1000);
                }
            synchronized (lipstick) {
                System.out.println(this.girlName + "获得了口红的锁");
            }
        }
    }
}
synchronized与lock的对比
  • lock是显示锁(手动开启和关闭锁,别忘记关锁)synchronized是隐式锁,除了作用域自动释放

  • lock只有代码块锁,synchronized有代码块锁和方法锁

  • 使用lock锁,jvm将花费较少的时间来调度线程,性能更好。而且具有更好的扩展性(提供更多的子类)

  • 优先使用顺序:

    lock>同步代码块(已经进入方法体,分配了相应资源)>同步方法(在方法体之外)

    实例
  • package com.yeyue.thread;
    ?
    import java.util.concurrent.locks.ReentrantLock;
    ?
    public class TestLock {
        public static void main(String[] args) {
            TestLock2 testLock2 = new TestLock2();
    ?
            new Thread(testLock2).start();
            new Thread(testLock2).start();
            new Thread(testLock2).start();
        }
    }
    ?
    class TestLock2 implements Runnable{
    ?
        int ticketNums = 10;
        //定义lock锁
        private final ReentrantLock lock = new ReentrantLock();
    ?
        @Override
        public void run() {
            while (true){
                try{
                    lock.lock();
                    if(ticketNums>0){
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(ticketNums--);
                    }else {
                        break;
                    }
                }finally {
                    lock.unlock();
                }
            }
        }
    }
    生产者消费者模型-->利用缓冲区解决:管程法
  • package com.yeyue.thread;
    ?
    //测试:生产者消费者模型-->利用缓冲区解决:管程法
    ?
    //生产者,消费者,产品,缓冲区
    public class TestPC {
        public static void main(String[] args) {
            SynContainer container = new SynContainer();
    ?
            new Productor(container).start();
            new Consumer(container).start();
    ?
        }
    }
    ?
    //生产者
    class Productor extends Thread{
        SynContainer container;
    ?
        public Productor(SynContainer container){
            this.container = container;
        }
    ?
        //生产
        @Override
        public void run() {
            for (int i = 0; i < 100; i++) {
                container.push(new Chicken(i));
                System.out.println("生产了"+i+"只鸡");
                try {
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    ?
    //消费者
    class Consumer extends Thread{
        SynContainer container;
    ?
        public Consumer(SynContainer container){
            this.container = container;
        }
    ?
        //消费
        @Override
        public void run() {
            for (int i = 0; i < 100; i++) {
                System.out.println("消费了-->"+container.pop().id+"只鸡");
                try {
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    ?
    //产品
    class Chicken{
        int id ; //产品ID
    ?
        public Chicken(int id) {
            this.id = id;
        }
    }
    ?
    //缓冲区
    class SynContainer {
    ?
        //容器大小
        Chicken[] chickens = new Chicken[10];
        //容器计数器
        int count = 0;
    ?
    ?
        //生产者放入产品
        public synchronized void push(Chicken chicken){
            //如果产品满了,就需要生产者等待消费者消费
            if(count==chickens.length) {
                //通知消费者消费,生产等待
                try {
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            //如果没有满,我们就需要丢入产品
            chickens[count]=chicken;
            count++;
    ?
            //可以通知消费者消费了
            this.notifyAll();
        }
    ?
        //消费者消费产品
        public synchronized Chicken pop(){
            //判断能否消费
            if(count==0){
                //等待生产者生产,消费者等待
                try {
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
    ?
            //如果可以消费
            count--;
            Chicken chicken = chickens[count];
    ?
            //吃完了
            this.notifyAll();
            return chicken;
        }
    ?
    ?
    ?
    ?
    ?
    ?
    ?
    ?
    ?
    ?
    ?
    ?
    }
    测试:生产者消费者模型2-->信号灯法
  • package com.yeyue.thread;
    ?
    //测试:生产者消费者模型2-->信号灯法
    public class TestPC2 {
        public static void main(String[] args) {
            TV tv = new TV();
            new Player(tv).start();
            new Watcher(tv).start();
        }
    }
    ?
    //生产者:演员
    class Player extends Thread{
        TV tv;
        public Player(TV tv){
            this.tv = tv;
        }
    ?
        //表演节目
        @Override
        public void run() {
            for (int i = 0; i < 20; i++) {
                if(i%2==0){
                    this.tv.play("快乐大本营");
                }else{
                    this.tv.play("抖音:记录美好生活");
                }
            }
        }
    }
    ?
    //消费者:观众
    class Watcher extends Thread{
        TV tv;
        public Watcher(TV tv){
            this.tv = tv;
        }
    ?
        //观看
        @Override
        public void run() {
            for (int i = 0; i < 20; i++) {
                tv.watch();
            }
        }
    }
    ?
    //产品:节目
    class TV {
        //演员表演,观众等待 T
        //观众观看,演员等待 F
        String voice; //表演的节目
        boolean flag = true;
    ?
        //表演
        public synchronized void play(String voice){
    ?
            //等待观众观看
            if (!flag){
                try {
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
    ?
            System.out.println("演员表演了:" + voice);
    ?
            this.notifyAll(); //通知观众观看
            this.voice = voice;
            this.flag = !this.flag;
        }
    ?
        //观看
        public synchronized  void watch(){
            if(flag){
                try {
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("观看了"+voice);
    ?
            this.notifyAll(); //通知演员表演
            this.flag = !this.flag;
        }
    ?
    }
    线程池
  • package com.yeyue.thread;
    ?
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    ?
    public class TestPool {
        public static void main(String[] args) {
            //1、创建服务,创建线程池
            //newFixedThreadPool 参数:线程池大小
            ExecutorService service = Executors.newFixedThreadPool(10);
    ?
            //执行
            service.execute(new MyThread());
            service.execute(new MyThread());
            service.execute(new MyThread());
            service.execute(new MyThread());
    ?
            //2、关闭链接
            service.shutdown();
    ?
        }
    }
    ?
    class MyThread implements Runnable{
    ?
        @Override
        public void run() {
            System.out.println(Thread.currentThread().getName());
        }
    }

posted on 2022-04-18 00:02  jf009  阅读(116)  评论(0编辑  收藏  举报