线程八锁——synchronized加在方法上

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所谓的“线程八锁”
其实就是考察 synchronized 锁住的是哪个对象
情况1：12 或 21

@Slf4j(topic = "c.Number")
class Number{public synchronized void a() {log.debug("1");}public synchronized void b() {log.debug("2");}
}
public static void main(String[] args) {Number n1 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n1.b(); }).start();
}

情况2：1s后12，或 2 1s后1

@Slf4j(topic = "c.Number")
class Number{public synchronized void a() {sleep(1);log.debug("1");}public synchronized void b() {log.debug("2");}
}
public static void main(String[] args) {Number n1 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n1.b(); }).start();
}

情况3：3 1s 12 或 23 1s 1 或 32 1s 1

@Slf4j(topic = "c.Number")
class Number{public synchronized void a() {sleep(1);log.debug("1");}public synchronized void b() {log.debug("2");}public void c() {log.debug("3");}
}
public static void main(String[] args) {Number n1 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n1.b(); }).start();new Thread(()->{ n1.c(); }).start();
}

情况4：2 1s 后 1

@Slf4j(topic = "c.Number")
class Number{public synchronized void a() {sleep(1);log.debug("1");}public synchronized void b() {log.debug("2");}
}
public static void main(String[] args) {Number n1 = new Number();Number n2 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n2.b(); }).start();
}

情况5：2 1s 后 1

@Slf4j(topic = "c.Number")
class Number{public static synchronized void a() {// 在静态方法上加锁，锁住的是类对象sleep(1);log.debug("1");}public synchronized void b() {// 在成员方法上加锁，锁住的是this对象log.debug("2");}}
public static void main(String[] args) {Number n1 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n1.b(); }).start();
}

情况6：1s 后12，或 2 1s后 1

@Slf4j(topic = "c.Number")
class Number{public static synchronized void a() {sleep(1);log.debug("1");}public static synchronized void b() {log.debug("2");}
}
public static void main(String[] args) {Number n1 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n1.b(); }).start();
}

情况7：2 1s 后 1

@Slf4j(topic = "c.Number")
class Number{public static synchronized void a() {sleep(1);log.debug("1");}public synchronized void b() {log.debug("2");}
}
public static void main(String[] args) {Number n1 = new Number();Number n2 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n2.b(); }).start();
}

情况8：1s 后12，或 2 1s后 1

@Slf4j(topic = "c.Number")
class Number{public static synchronized void a() {sleep(1);log.debug("1");}public static synchronized void b() {log.debug("2");}
}
public static void main(String[] args) {Number n1 = new Number();Number n2 = new Number();new Thread(()->{ n1.a(); }).start();new Thread(()->{ n2.b(); }).start();
}