关于线程死锁和重进入的小例子
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package thread;public class Test implements Runnable {public Object 吃西餐先拿;static Object 刀 = new Object();static Object 叉 = new Object();public static void main(String[] args) {ChildClass c = new ChildClass();c.f();System.out.println("不会死锁，这种机制叫重进入！");//--------重进入例子---------------//---------死锁例子---------------Test 丈夫 = new Test();Test 妻子 = new Test();丈夫.吃西餐先拿 = 刀;妻子.吃西餐先拿 = 叉;Thread t1 = new Thread(丈夫);Thread t2 = new Thread(妻子);t1.start();t2.start();}public void run() {if (吃西餐先拿 == 刀) {synchronized (刀) {try {Thread.sleep(500);} catch (InterruptedException e) {}synchronized (叉) {System.out.println("1");}}}if (吃西餐先拿 == 叉) {synchronized (叉) {try {Thread.sleep(500);} catch (InterruptedException e) {}synchronized (刀) {System.out.println("0");}}}}}class ParentClass extends Thread {public synchronized void f() {}}class ChildClass extends ParentClass {public synchronized void f() {super.f();}}子类的重写同步方法f中又调用了父类的同步f方法 这时不会对调用的该对象死锁，可以理解为不会上第二个锁 也可以理解为第二把锁没有加上去。总而言之 sychronized关键字的本质是不让其他线程在同一对象上再上一把锁。