OOP - f2019 Buffer (revised)

public class Buffer{

    private Mutex m1, m2;
    private int n;
    private in k;

    private ReentrantLock lock;
    object obj;

    public Buffer(int n, int k){
        lock = new ReentrantLock();
        m = new Mutex();
        this.n = n;
        this.k = k;
        obj = new Object();
    }

    public void await() {
        lock.lock();
        m2.lock();


        // atomic Substraction
        m1.lock();
        n--;
        m1.unlock();
        while(n > 0 && k > 0){
            m2.unlock();
            lock.unlock();

            obj.wait();

            lock.lock();
            m2.lock();
        }
        m2.unlock();

        // atomic substraction
        m2.lock();
        k--;
        if(k>0) obj.notify();
        m2.unlock();
        lock.unlock();
    }
}