What's the benefit of having two ReentrantLock in a class?

Question

If I have this code:

public class PrLock {
    private Lock lock1= new ReentrantLock();
    private Lock lock2= new ReentrantLock();
    private int num=0;

    public void addLock1(){
        lock1.lock();
        try {
            num++;
            System.out.println(Thread.currentThread().getName()+" NUM "+num);
        } finally{
            lock1.unlock();
        }
    }
    public void addLock2() {
        lock2.lock();
        try {
            num++;
            System.out.println(Thread.currentThread().getName()+" NUM "+num);
        } finally{
            lock2.unlock();
        }
    }
}

What is the difference between lock1 and lock2, is it a simple alias or is there a different logic?

They're different locks so they won't block each other. – Bubletan May 13 '15 at 22:03 — Bubletan, May 13 '15 at 22:03
There is no aliasing here. They refer to different objects. – user207421 May 13 '15 at 22:45 — user207421, May 13 '15 at 22:45

score 0 · Answer 1 · answered May 13 '15 at 22:26

If you would use one lock for those two methods you won't be able to execute them concurrently.

So having two locks means, while executing addLock1() from Thread-A you can execute addLock2() from Thread-B. Thread-B will be blocked, if you had one lock.

What's the benefit of having two ReentrantLock in a class?

1 Answers1