java中的线程八锁

public class Main {
    public synchronized void test(){
    }
}
等价于
public class Main {
    public  void test(){
        synchronized(this){
        }
    }
}

public class Main {
    public static synchronized void test(){
    }
}
等价于
public class Main {
    public static  void test(){
        synchronized (Main.class){
        }
    }
}

• 非静态同步方法锁住的是实例对象本身
• 静态同步方法锁住的是类对象本身

线程八锁------>考察的就是锁住哪个对象

@Slf4j(topic = "c.Number")
public class Number {
    public synchronized void a() {
        log.debug("a");
    }
    public synchronized void b(){
        log.debug("b");
    }
    public static void main(String[] args) {
        Number n1=new Number();
        new Thread(()->n1.a(),"t1").start();
        new Thread(()->n1.b(),"t2").start();
    }
}


线程t1和线程t2锁住的是同一个实例对象n1,有竞争
情况：ab或者ba

@Slf4j(topic = "c.Number")
public class Number {
    public synchronized void a() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
        log.debug("a");
    }
    public synchronized void b(){
        log.debug("b");
    }
    public static void main(String[] args) {
        Number n1=new Number();
        new Thread(()-> {
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->n1.b(),"t2").start();
    }
}
线程t1和线程t2锁住的是同一个实例对象n1,有竞争
情况：1s后ab或者 b 1s后 a

@Slf4j(topic = "c.Number")
public class Number {
    public synchronized void a() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
        log.debug("a");
    }
    public synchronized void b(){
        log.debug("b");
    }
    public void c(){
        log.debug("c");
    }
    public static void main(String[] args) {
        Number n1=new Number();
        new Thread(()-> {
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->n1.b(),"t2").start();
        new Thread(()->n1.c(),"t3").start();
    }
}
线程t3没有去争抢锁
情况：c 1s 后ab 或者 bc 1s 后 a 或者 cb 1s后a

@Slf4j(topic = "c.Number")
public class Number {
    public synchronized void a() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
        log.debug("a");
    }
    public synchronized void b(){
        log.debug("b");
    }

    public static void main(String[] args) {
        Number n1=new Number();
        Number n2=new Number();
        new Thread(()-> {
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->n2.b(),"t2").start();

    }
}
线程t1和线程t2锁住的是不同的实例对象，没有竞争
情况 b 1s后 a

@Slf4j(topic = "c.Number")
public class Number {
    public static synchronized void a() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
        log.debug("a");
    }
    public synchronized void b(){
        log.debug("b");
    }

    public static void main(String[] args) {
        Number n1=new Number();
        new Thread(()-> {
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->n1.b(),"t2").start();

    }
}
线程t1锁住的是类对象本身,线程t2锁住的是n1实例对象本身,没有竞争
情况: b 1s后 a

@Slf4j(topic = "c.Number")
public class Number {
    public static synchronized void a() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
        log.debug("a");
    }
    public static synchronized void b(){
        log.debug("b");
    }

    public static void main(String[] args) {
        Number n1=new Number();
        new Thread(()-> {
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->n1.b(),"t2").start();

    }
}
线程t1和线程t2锁住的都是类对象本身,有竞争
情况： 1s 后 ab  或者 b 1s后 a

@Slf4j(topic = "c.Number")
public class Number {
    public static synchronized void a() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
        log.debug("a");
    }
    public  synchronized void b(){
        log.debug("b");
    }

    public static void main(String[] args) {
        Number n1=new Number();
        Number n2=new Number();
        new Thread(()-> {
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->n2.b(),"t2").start();

    }
}
线程t1锁住的是类对象本身,线程t2锁住的是n2实例对象本身，没有竞争
情况 b 1s 后 a

@Slf4j(topic = "c.Number")
public class Number {
    public static synchronized void a() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
        log.debug("a");
    }
    public static synchronized void b(){
        log.debug("b");
    }

    public static void main(String[] args) {
        Number n1=new Number();
        Number n2=new Number();
        new Thread(()-> {
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->n2.b(),"t2").start();

    }
}
线程t1和t2锁住的都是类对象本身，有竞争
情况： 1s后ab 或者 b 1s后 a

有误请指正
参考：黑马程序员全面深入学习Java并发编程，JUC并发编程全套教程.