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Threads in Java - Deadlock (Part 16)

Sometimes in a Multithreading environment, there arises a condition where two threads are waiting for each other to release a resource they require.

For instance, it Thread-1 locks the resource A and tries to lock resource B, and Thread-2 has already locked resource B and tries to lock resource A, deadlock arises. Thread-1 can never lock resource B and Thread-2 can never lock resource A. In addition, neither of them will ever know. They will remain locked on their objects, forever. This situation is a deadlock.

Thread-1 locks resource A, waits for resource B.
Thread-2 locks resource B, waits for resource A.

Deadlock (source: dzone)

Deadlock example


The above code shows the example of a deadlock for the reasons discussed above.
Here, Thread-1 has acquired a lock on resource A and Thread-B has acquired a lock on resource B. Now, Thread-1 tries to acquire a lock on B (already held by Thread-2) and Thread-2 tries to acquire a lock on A (already held by A). This situation caused deadlock.

To resolve the deadlock, we reorder the locking on resources as follows - 
Now, since both the threads are acquiring the locks in the same order, the deadlock condition is resolved.

Conclusion

Congratulations!! 🙋 today we discussed Deadlock and its resolution with their implementations. I hope you enjoyed this post.

You can find the complete code of this project on my GitHub in this commit. Feel free to fork or open issues, if any.

I would love to hear your thoughts on this and would like have suggestions from you to make it better. 

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Happy Coding 😊

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