Java中Synchronized的用法

package DeadLock;

public class DeadLock {
    public static String obj1 = "obj1";
    public static String obj2 = "obj2";
    public static  String obj3 ="obj3";
    public static void main(String[] args){
        Thread a = new Thread(new Lock1());
        Thread b = new Thread(new Lock2());
        a.start();
        b.start();
    }
}
class Lock1 implements Runnable{
    public void run(){
        try{
            System.out.println("Lock1 running");
            while(true){
                synchronized(DeadLock.obj1){
                    System.out.println("Lock1 lock obj1");
                    Thread.sleep(3000);//获取obj1后先等一会儿，让Lock2有足够的时间锁住obj2
                    synchronized(DeadLock.obj2){
                        System.out.println("Lock1 lock obj2");
                    }
                }
            }
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

假如a线程先运行，线程lock1抢占资源（synchronized） obj1锁住然后暂停30秒给lock2抢占资源的时间，lock2抢占obj2并抢占（

synchronized）obj2.然后暂停30秒，此时线程a运行想要抢占资源obj2但是抢占不到因为已经被线程b抢占会陷入等待

class Lock2 implements Runnable{ public void run(){ try{ System.out.println("Lock2 running"); while(true){ synchronized(DeadLock.obj2){ System.out.println("Lock2 lock obj2"); Thread.sleep(3000); synchronized(DeadLock.obj1){ System.out.println("Lock2 lock obj1"); } } } }catch(Exception e){ e.printStackTrace(); } }}

假如b线程先运行，情况如上

输出情况：

Lock1 running
Lock1 lock obj1
Lock2 running
Lock2 lock obj2

线程停止只会跑出四行。如果换其他字符串。控制台会不断输出。