关于锁的对象

锁的对象共有两种：类对象和Class模板对象

1.标准情况下，两个线程、一个对象，先打印发短信还是打电话？发短信
2.发短信方法设置延迟4秒后，两个线程、一个对象，先打印发短信还是打电话？发短信
Synchronized锁的对象是方法的调用者，故两个方法用的是同一把锁，谁先拿到谁执行

package com.itheima.lock8;

import java.util.concurrent.TimeUnit;

public class Test01 {
    public static void main(String[] args) {
        Phone phone = new Phone();
        new Thread(()->{
            phone.sendMsg();
        },"A").start();
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

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

//资源类
class Phone{
    public synchronized void sendMsg(){
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName()+"发短信");
    }
    public synchronized void call(){
        System.out.println(Thread.currentThread().getName()+"打电话");
    }
}

3.两个线程、一个对象、一个同步方法、一个普通方法，先打印发短信还是hello？hello
因为发短信方法会延迟4秒，hello是普通方法，无锁，不是同步方法，不受锁的影响，不存在抢占资源情况。

package com.itheima.lock8;

import java.util.concurrent.TimeUnit;

public class Test02 {
    public static void main(String[] args) {
        Phone2 phone = new Phone2();
        new Thread(()->{
            phone.sendMsg();
        },"A").start();
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

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

//资源类
class Phone2{
    public synchronized void sendMsg(){
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName()+"发短信");
    }
    public synchronized void call(){
        
        System.out.println(Thread.currentThread().getName()+"打电话");
    }

    //普通方法
    public void hello(){
        System.out.println(Thread.currentThread().getName()+"=>hello");
    }
}

4.两个线程、两个对象、两个同步方法，先打印发短信还是打电话？打电话
两个对象会存在两把锁，锁不一样，故按照时间顺序来执行

package com.itheima.lock8;

import java.util.concurrent.TimeUnit;

public class Test03 {
    public static void main(String[] args) {
        Phone3 phone1 = new Phone3();
        Phone3 phone2 = new Phone3();
        new Thread(()->{
            phone1.sendMsg();
        },"A").start();
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

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

//资源类
class Phone3{
    public synchronized void sendMsg(){
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName()+"发短信");
    }
    public synchronized void call(){

        System.out.println(Thread.currentThread().getName()+"打电话");
    }

    //普通方法
    public void hello(){
        System.out.println(Thread.currentThread().getName()+"=>hello");
    }
}

5.两个线程、一个对象、两个静态同步方法，先打印发短信还是打电话？发短信
当同步方法为静态时，锁的是其Class模板，一个类只有一个Class对象

package com.itheima.lock8;

import java.util.concurrent.TimeUnit;

public class Test04 {
    public static void main(String[] args) {
        Phone4 phone4 = new Phone4();
        new Thread(()->{
            phone4.msg();
        },"A").start();
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        new Thread(()->{
            phone4.call();
        },"B").start();
    }
}
class Phone4{
    public static synchronized void msg(){
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("发短信");
    }
    public static synchronized void call(){
        System.out.println("打电话");
    }
}

6.两个线程、两个对象、两个静态同步方法，先打印发短信还是打电话？发短信
当同步方法为静态时，锁的是其Class模板，一个类只有唯一的一个Class对象

package com.itheima.lock8;

import java.util.concurrent.TimeUnit;

public class Test04 {
    public static void main(String[] args) {
        Phone4 phone1 = new Phone4();
        Phone4 phone2 = new Phone4();

        new Thread(()->{
            phone1.msg();
        },"A").start();
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        new Thread(()->{
            phone2.call();
        },"B").start();
    }
}
class Phone4{
    public static synchronized void msg(){
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("发短信");
    }
    public static synchronized void call(){
        System.out.println("打电话");
    }
}

7.两个线程、一个对象、一个静态同步方法、一个普通同步方法，先打印发短信还是打电话？打电话
静态同步方法锁的是Class类对象，普通同步方法锁的是类对象，因此拥有两把锁，互不冲突

package com.itheima.lock8;

import java.util.concurrent.TimeUnit;

public class Test05 {
    public static void main(String[] args) {
        Phone5 phone = new Phone5();

        new Thread(()->{
            phone.msg();
        },"A").start();
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        new Thread(()->{
            phone.call();
        },"B").start();
    }
}
class Phone5{
    public static synchronized void msg(){
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("发短信");
    }
    public synchronized void call(){
        System.out.println("打电话");
    }
}

8.两个线程、两个对象、一个静态同步方法、一个普通同步方法，先打印发短信还是打电话？打电话
拥有两个锁，故先输出没有延时的

package com.itheima.lock8;

import java.util.concurrent.TimeUnit;

public class Test05 {
    public static void main(String[] args) {
        Phone5 phone1 = new Phone5();
        Phone5 phone2 = new Phone5();

        new Thread(()->{
            phone1.msg();
        },"A").start();
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        new Thread(()->{
            phone2.call();
        },"B").start();
    }
}
class Phone5{
    public static synchronized void msg(){
        try {
            TimeUnit.SECONDS.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("发短信");
    }
    public synchronized void call(){
        System.out.println("打电话");
    }
}

标签：Thread,对象,void,关于,TimeUnit,发短信,new,public
来源： https://blog.csdn.net/Puyefeng/article/details/122800522