What are the differences between locks and semaphores in Java?

What are the differences between locks and semaphores in Java?

Locks and semaphores are both synchronization mechanisms in Java, but they serve different purposes. A lock allows only one thread to access a resource at a time, while a semaphore can allow multiple threads to access a resource, up to a specified limit.

Can you give me an example of how to use a lock in Java?

Sure! You can use the ReentrantLock class. Here's a simple example:

ReentrantLock lock = new ReentrantLock();

lock.lock();
try {
    // critical section code
} finally {
    lock.unlock();
}

What about semaphores? How do they work?

Semaphores maintain a set number of permits. When a thread acquires a permit, it decreases the count. If no permits are available, the thread will block until one is released. Here's a basic example:

Semaphore semaphore = new Semaphore(3);

semaphore.acquire();
try {
    // critical section code
} finally {
    semaphore.release();
}

When should I use locks instead of semaphores?

Use locks when you need exclusive access to a resource. Use semaphores when you want to limit access to a resource to a certain number of threads.