Deadlock!!

[mulligan252]

Hi, I am trying to fix the deadlock situation here. Each Thread is waiting for the other to exit the bow synchronized method and therefore bowback method can not be invoked. How can i fix this code so the deadlock does not occur.. I've been trying to fix this for ages. i really appreciate anyone's help. Thanks.

//
public class Deadlock {
    static class Friend {
        private final String name;
        public Friend(String name) {
            this.name = name;
        }
        public String getName() {
            return this.name;
        }
        public synchronized void bow(Friend bower) {
            System.out.format("%s: %s has bowed to me!%n", 
                    this.name, bower.getName());
            bower.bowBack(this);
        }
        public synchronized void bowBack(Friend bower) {
            System.out.format("%s: %s has bowed back to me!%n",
                    this.name, bower.getName());
        }
    }
 
    public static void main(String[] args) {
        final Friend alphonse = new Friend("Alphonse");
        final Friend gaston = new Friend("Gaston");
        new Thread(new Runnable() {
            public void run() { alphonse.bow(gaston); }
        }).start();
        new Thread(new Runnable() {
            public void run() { gaston.bow(alphonse); }
        }).start();
    }
}
//

[copeg]

First, please wrap your code in the code tags....

How can i fix this code so the deadlock does not occur

Why are the methods synchronized? In the code posted, you are not changing any values, so there shouldn't be concurrency issues.

[ofesak]

here is really no deadlock
what is a real your problem please clarify more exactly



__________________________________________________ ____________________________
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[copeg]

here is really no deadlock
what is a real your problem please clarify more exactly

Really? No deadlock? Are you going to explain, or are you just here to post nonsense with links to drive traffic to your blog

[qurtan]

I have a little hard to see why you want to sync this. The only reason I see is if you always want a "bowBack" before a new "bow" is performed. If this is the case I should synchronize "bow" with an class variable like this:

static class Friend {
        private static final Object syncObject = new Object();
        private final String name;
        public Friend(String name) {
            this.name = name;
        }
        public String getName() {
            return this.name;
        }
        public void bow(Friend bower) {
            synchronized(syncObject) {
                System.out.format("%s: %s has bowed to me!%n",
                        this.name, bower.getName());
                bower.bowBack(this);
            }
        }
        public void bowBack(Friend bower) {
            System.out.format("%s: %s has bowed back to me!%n",
                    this.name, bower.getName());
        }
    }

[mulligan252]

Really? No deadlock? Are you going to explain, or are you just here to post nonsense with links to drive traffic to your blog

This is nonsense? explain please why? I am just asking a question about deadlock as i am new to threads and synchronization. This was a problem i was given as part of an assignment. I know the methods do not need to be synchronized.. it's the first thing i noticed.. but in the case that they really did, how i would fix this. Thanks alot qurtan for a solution for this..

[helloworld922]

This is nonsense? explain please why?

Copeg wasn't referring to your topic, he was referring to ofesak's post about there not being any deadlock.

There is absolutely the potential for a deadlock problem here. The most obvious solution is to remove synchronization as there's no data dependency issues, but without knowing if you wanted some sort of execution order to be enforced there's no way to tell if this is the correct solution.

[copeg]

This is nonsense? explain please why?

The comment was in reference to the quoted text in my post - a quote from the post by ofesak - not to your post mulligan252 (thank you helloworld for the clarification)