Confusion in usage of synchronized keyword

Asked Dec 18 '17 at 12:10

Active Dec 18 '17 at 12:19

Viewed 60 times

This is confusion while preparing for an exam, I have weird piece of code that does nothing except bugging my head. Refer the below code

public class p2 implements Runnable {

    static Object lock = new Object();

    public void run() {
        String name = Thread.currentThread().getName();
        synchronized(lock) {
            System.out.println(name + " entering lock.");
            try { lock.wait(); } catch(Exception e) {System.out.println(e);}
            System.out.println(name + " came out");
        }
    }

    public static void main(String[] args) {
        new Thread(new p2()).start();
        new Thread(new p2()).start();
    }
}

The output of the code is :

Thread-0 entering lock.
Thread-1 entering lock.

My question is when the thread enters the synchronized block it has exclusive access for that block, since it has ownership on that object's monitor. Then why Thread-1 is allowed to enter the monitor?

edited Dec 18 '17 at 12:11

Mark Rotteveel

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asked Dec 18 '17 at 12:10

Madhusoodan P

1

The quote block (prefixed by `>`) is not for emphasis, it is for **quotes** from other sources. – Mark Rotteveel Dec 18 '17 at 12:12
3

Did you read the [documentation for Object.wait()](https://docs.oracle.com/javase/7/docs/api/java/lang/Object.html)? – Andrew Henle Dec 18 '17 at 12:13
@MarkRotteveel thanks – Madhusoodan P Dec 18 '17 at 12:14
@AndrewHenle Ok it says that the current thread leaves the monitor and waits for another to notify it. Thanks for pointing – Madhusoodan P Dec 18 '17 at 12:15

Confusion in usage of synchronized keyword

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