How can the correct operation of competing objects of a class be ensured during parallel execution?

To ensure the correct operation of competing objects of a class during parallel execution in Java, synchronization mechanisms and access control to shared resources are used:

• Synchronized methods and blocks (synchronized): allow guaranteeing that only one thread executes the critical section at a time.

• Using classes from java.util.concurrent: such as ReentrantLock, Semaphore, CountDownLatch for more flexible lock management.

• Using atomic variables (AtomicInteger, AtomicReference, etc.): for operations on variables without explicit locking.

• Immutable objects: minimize the need for synchronization, as immutable objects are safe for access from multiple threads.

Example using synchronized to protect a shared resource:

public class Counter {
    private int count = 0;

    public synchronized void increment() {
        count++;
    }

    public synchronized int getCount() {
        return count;
    }
}

Thus, the correct choice of mechanism depends on the specific task and requirements for performance and safety.