What are some examples of deadlocks in Java?

What are some examples of deadlocks in Java?

Deadlocks in Java occur when two or more threads are blocked forever, each waiting for the other to release a resource. A classic example is when Thread A holds Resource 1 and waits for Resource 2, while Thread B holds Resource 2 and waits for Resource 1.

Can you give me a code example of a deadlock?

Sure! Here's a simple example:

class Resource {
    public synchronized void lock(Resource other) {
        System.out.println(Thread.currentThread().getName() + " locked " + this);
        other.lock(this);
    }
}

public class DeadlockExample {
    public static void main(String[] args) {
        final Resource resource1 = new Resource();
        final Resource resource2 = new Resource();

        Thread thread1 = new Thread(() -> resource1.lock(resource2));
        Thread thread2 = new Thread(() -> resource2.lock(resource1));

        thread1.start();
        thread2.start();
    }
}

This code can lead to a deadlock situation.

How can I prevent deadlocks in my Java application?

To prevent deadlocks, you can follow these strategies:

1. Lock ordering: Always acquire locks in a consistent order.
2. Timeout: Use timeouts when trying to acquire locks.
3. Avoid nested locks: Minimize the use of multiple locks.

What tools can help detect deadlocks?

Tools like VisualVM, JConsole, and Java Mission Control can help detect deadlocks by monitoring thread states and resource usage.