线程基础知识05 synchronized类锁和对象锁演示

1 简介

　　synchronized在方法内，同步代码块，传入对象，使用的是对象锁，传入class对象，使用的是类锁

　　作用于普通方法，也是对象锁，当前对象

　　作用于静态方法，是类锁

2 同步方法示例

2.1

两个synchronized 修饰的普通方法

public class SychTest1 {

    static class Phone{
        synchronized void  sendEmail(){
            System.out.println("EMAIL");
        }
        synchronized void sendMsg(){
            System.out.println("MSG");
        }
    }

    public static void main(String[] args) {

        Phone p = new Phone();

        new Thread(()->{
            p.sendEmail();
        }).start();

        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(()->{
            p.sendMsg();
        }).start();
    }
}

执行结果，持有同一个锁对象p

EMAIL
MSG

2.2

两个synchronized 修饰的普通方法，sendEmail睡了2秒

public class SychTest2 {

    static class Phone{
        synchronized void sendEmail(){
            try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println("EMAIL");
        }
        synchronized void sendMsg(){
            System.out.println("MSG");
        }
    }

    public static void main(String[] args) {

        Phone p = new Phone();

        new Thread(()->{
            p.sendEmail();
        }).start();
        
        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }
        new Thread(()->{
            p.sendMsg();
        }).start();
    }
}

执行结果，持有同一个锁对象p，所以还是sendEmail先执行

EMAIL
MSG

2.3

一个同步方法，一个普通方法

public class SychTest3 {

    static class Phone{
        synchronized void sendEmail(){
            try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println("EMAIL");
        }
        void sendMsg(){
            System.out.println("MSG");
        }

    }

    public static void main(String[] args) {

        Phone p = new Phone();

        new Thread(()->{
            p.sendEmail();
        }).start();


        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(()->{
            p.sendMsg();
        }).start();
    }
    
}

执行结果

MSG
EMAIL

2.4

两个同步方法，但是是两个不同的对象p和p2去调用同步方法

public class SychTest4 {

    static class Phone{
        synchronized void sendEmail(){
            try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println("EMAIL");
        }
        synchronized void sendMsg(){
            System.out.println("MSG");
        }
        
    }

    public static void main(String[] args) {

        Phone p = new Phone();

        Phone p2 = new Phone();

        new Thread(()->{
            p.sendEmail();
        }).start();


        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(()->{
            p2.sendMsg();
        }).start();
    }
}

执行结果，持有的是不同的锁对象p和p2

MSG
EMAIL

2.5

两个静态同步方法

public class SychTest5 {

    static class Phone{
        synchronized static void sendEmail(){
            try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println("EMAIL");
        }
        synchronized static void sendMsg(){
            System.out.println("MSG");
        }
    }

    public static void main(String[] args) {

        Phone p = new Phone();

        new Thread(()->{
            p.sendEmail();
        }).start();


        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(()->{
            p.sendMsg();
        }).start();
    }
}

执行结果，持有的是同一个类锁

EMAIL
MSG

2.6

两个静态同步方法，两个对象p和p2去调用

public class SychTest6 {//?

    static class Phone{
        synchronized static void sendEmail(){
            try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println("EMAIL");
        }
        synchronized static void sendMsg(){
            System.out.println("MSG");
        }
    }

    public static void main(String[] args) {

        Phone p = new Phone();
        Phone p2 = new Phone();

        new Thread(()->{
            p.sendEmail();
        }).start();


        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(()->{
            p2.sendMsg();
        }).start();
    }
}

执行结果，持有的是同一个类锁，和哪个对象去调用无关

EMAIL
MSG

2.7

一个静态同步，一个非静态同步

public class SychTest7 {

    static class Phone{
        synchronized static void sendEmail(){
            try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println("EMAIL");
        }
        synchronized  void sendMsg(){
            System.out.println("MSG");
        }
    }

    public static void main(String[] args) {

        Phone p = new Phone();

        new Thread(()->{
            p.sendEmail();
        }).start();


        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(()->{
            p.sendMsg();
        }).start();
    }

}

执行结果，一个持有类锁，一个持有对象锁

MSG
EMAIL

2.8

一个静态同步方法，一个非静态同步方法，两个对象去调用

public class SychTest8 {

    static class Phone{
        synchronized static void sendEmail(){
            try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println("EMAIL");
        }
        synchronized  void sendMsg(){
            System.out.println("MSG");
        }
    }

    public static void main(String[] args) {

        Phone p = new Phone();

        Phone p2 = new Phone();


        new Thread(()->{
            p.sendEmail();
        }).start();


        try { Thread.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(()->{
            p2.sendMsg();
        }).start();
    }
}

执行结果，一个持有类锁，一个持有对象锁

MSG
EMAIL

3 同步代码示例

3.1

传入class对象

public class SychTest13 {

    public static synchronized  void aa()  {
        System.out.println("aaa");
    }

    public static void main(String[] args) throws InterruptedException {

        new Thread(()->{
            synchronized (SychTest13.class){
                try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); }
                System.out.println("aaaaaaaaaaaa");
            }
        }).start();

        new Thread(()->{
            synchronized (SychTest13.class){
                System.out.println("bbbbbbbbbb");
            }
        }).start();
    }
}

执行结果

aaaaaaaaaaaa
bbbbbbbbbbb

3.2

传入同一个对象t1

public class SychTest14 {

    public static synchronized  void aa()  {
        System.out.println("aaa");
    }

    public static void main(String[] args) throws InterruptedException {
        SychTest13 t1 = new SychTest13();
        new Thread(()->{
            synchronized (t1){
                try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); }
                System.out.println("aaaaaaaaaaaa");
            }
        }).start();

        new Thread(()->{
            synchronized (t1){
                System.out.println("bbbbbbbbbb");
            }
        }).start();
    }
}

执行结果

aaaaaaaaaaaa
bbbbbbbbbbb

3.3

传入对象t1和t2

public class SychTest15 {

    public static synchronized  void aa()  {
        System.out.println("aaa");
    }

    public static void main(String[] args) throws InterruptedException {
        SychTest13 t1 = new SychTest13();
        SychTest13 t2 = new SychTest13();
        new Thread(()->{
            synchronized (t1){
                try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); }
                System.out.println("aaaaaaaaaaaa");
            }
        }).start();

        new Thread(()->{
            synchronized (t2){
                System.out.println("bbbbbbbbbb");
            }
        }).start();
    }
}

执行结果

bbbbbbbbbb
aaaaaaaaaaaa