8锁问题

8锁问题

1.synchronized 锁的对象是方法调用者,两个方法用的是同一个锁，谁先拿到谁执行！结果：先发短信后打电话

package com.czp.lock;

import java.util.concurrent.TimeUnit;

/**
 * 8锁就是关于锁的八个问题
 * 1\. 标准情况下,两个线程先打印 发短信 还是打电话
 * AsendMessage
 * Bcall
 *  synchronized 放在方法上  锁的对象是方法调用者
 *
 */
public class Test1 {

    public static void main(String[] args) {
        Phone phone = new Phone();

        new Thread(()->{
            phone.sendMessage();
        },"A").start();

        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(()->{
            phone.call();
        },"B").start();
    }
}

class Phone{

    public synchronized void sendMessage(){
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName() + "sendMessage");
    }

    public synchronized void call(){
        System.out.println(Thread.currentThread().getName() + "call");
    }
}

package com.czp.lock;

import java.util.concurrent.TimeUnit;

/**
 * 增加了一个普通方法
 * 3\. hello后发短信
 *
 * 4.打电话/后发短信
 */
public class Test2 {
    public static void main(String[] args) {
        Phone1 phone = new Phone1();
        Phone1 phone2 = new Phone1();

        new Thread(() -> {
            phone.sendMessage();
        }, "A").start();

        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(() -> {
//            phone.hello();
            phone2.call();
        }, "B").start();
    }
}

class Phone1 {

    public synchronized void sendMessage() {
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName() + "sendMessage");
    }

    public synchronized void call() {
        System.out.println(Thread.currentThread().getName() + "call");
    }
    //这里没有锁,不受锁的影响
    public void hello(){
        System.out.println("hello");
    }
}

package com.czp.lock;

import java.util.concurrent.TimeUnit;

/**
 * 5.增加两个静态的同步方法
 * synchronized 锁的是方法调用者
 * static 静态方法类一加载就有了 锁的是CLass
 *先发短信后打电话
 * 6\. 两个对象,两个静态同步方法,先发短信还是先打电话
 *发短信后打电话
 */
public class Test3 {

    public static void main(String[] args) {
        Phone2 phone2 = new Phone2();
        Phone2 phone3 = new Phone2();

        new Thread(() -> {
            phone2.sendMessage();
        }, "A").start();

        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(() -> {
            phone3.call();
        }, "B").start();
    }
}
class Phone2 {

    public static synchronized void sendMessage() {
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName() + "sendMessage");
    }

    public static synchronized void call() {
        System.out.println(Thread.currentThread().getName() + "call");
    }
}

package com.czp.lock;

import java.util.concurrent.TimeUnit;

/**
 * 7.一个静态同步方法,一个普通同步方法 ,一个对象,先输出哪一个
 *先call后发短信
 * 8\. 一个静态同步方法,一个普通同步方法, 两个对象,先打印哪一个
 */先call后发信息
public class Test4 {
    public static void main(String[] args) {
        Phone3 phone3 = new Phone3();
        Phone3 phone4 = new Phone3();

        new Thread(() -> {
            phone3.sendMessage();
        }, "A").start();

        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(() -> {
            phone4.call();
        }, "B").start();
    }
}

class Phone3 {

    public static synchronized void sendMessage() {
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName() + "sendMessage");
    }

    //普通同步方法
    public synchronized void call() {
        System.out.println(Thread.currentThread().getName() + "call");
    }

}

小结

new this 具体的一个手机对象

static Class 唯一的模板