Java Concurrency and Deadlock

Question

What concurrency problem is most likely with the MultiLock class?
 
```java
public class MultiLock {
    private int[] arrayA = new int[2];
    private int[] arrayB = new int[2];
    
    public void methodOne() {
        synchronized(arrayA) {
            try { Thread.sleep(50); } catch (InterruptedException e) {}
            synchronized(arrayB) {
                arrayA[0] = 10;
            }
        }
    }
    
    public void methodTwo() {
        synchronized(arrayB) {
            try { Thread.sleep(50); } catch (InterruptedException e) {}
            synchronized(arrayA) {
                arrayB[0] = 20;
            }
        }
    }
    
    public static void main(String[] args) {
        MultiLock ml = new MultiLock();
        Thread t1 = new Thread(() -> ml.methodOne());
        Thread t2 = new Thread(() -> ml.methodTwo());
        t1.start();
        t2.start();
    }
}
```

Accepted Answer

The lock ordering in methodOne and methodTwo is reversed, which can lead to a deadlock if both methods are executed concurrently.

Answer

Arrays are inherently thread-safe, so synchronizing on them is unnecessary and does not introduce any problems.

Answer

The sleep calls ensure that thread execution is serialized, thereby preventing any concurrency issues.

Answer

Deadlock is impossible because the locked objects are mutable arrays, which cannot cause deadlock conditions.

Question Leaderboard