Java Multithreading and Parallel Programming Masterclass - What Is a Deadlock and How Can We Avoid It?

The lecture discusses thread synchronization issues, focusing on deadlocks and livelocks. It explains deadlocks as situations where threads wait indefinitely for resources held by each other, using a Java example to illustrate. Strategies to avoid deadlocks, such as consistent lock ordering and using try-lock with timeouts, are covered. Livelocks, where threads remain active but make no progress, are also introduced.

What is a deadlock in the context of multithreading?

• A situation where threads run indefinitely without synchronization.

• A scenario where threads wait indefinitely for resources held by each other.

• A condition where threads execute in parallel without any issues.

• A state where threads are terminated unexpectedly.

What does the Java instruction 'thread.currentThread().join()' do?

• It allows a thread to join another thread's execution.

• It terminates the current thread immediately.

• It pauses the current thread for a specified duration.

• It causes the current thread to wait for itself to finish, leading to a block.

What is a recommended practice when using the 'join' method in Java?

• Use 'join' with a specific timeout to limit blocking.

• Use 'join' only in the main thread.

• Always use 'join' without a timeout.

• Avoid using 'join' in multithreaded applications.

In the deadlock example, what causes the deadlock between thread one and thread two?

• Thread one releases its lock before acquiring another.

• Both threads try to acquire the same lock at the same time.

• Thread two never releases its lock.

• Thread one and thread two acquire locks in a different order, causing a circular wait.

How can deadlocks be prevented in multithreading applications?

• By ensuring threads acquire locks in a consistent order.

• By using more threads to handle the locks.

• By avoiding the use of locks altogether.

• By increasing the priority of the threads.

What is a livelock in the context of multithreading?

• A state where threads are paused indefinitely.

• A situation where threads are terminated unexpectedly.

• A condition where threads are runnable but do not make progress.

• A scenario where threads execute without any synchronization.

What is the purpose of using 'tryLock' with a timeout?

• To ensure a lock is always acquired.

• To prioritize one thread over another.

• To attempt acquiring a lock within a specified time frame and handle failure gracefully.

• To release a lock after a certain period.