Tell about a complex bug or a difficult enhancement in your last project.

In my last project, I encountered a bug related to multithreading in a Java application, which manifested under high load and led to race conditions and incorrect data.

The problem was that several threads were modifying a shared resource simultaneously without proper synchronization. To resolve this, I:

• Analyzed call stacks and logs to localize the race condition.
• Made changes using synchronized blocks and ReentrantLock to control access to shared data.
• Conducted load testing to ensure the bug was fixed and performance was not affected.

Example of using ReentrantLock:

import java.util.concurrent.locks.ReentrantLock;

public class Counter {
    private int count = 0;
    private final ReentrantLock lock = new ReentrantLock();

    public void increment() {
        lock.lock();
        try {
            count++;
        } finally {
            lock.unlock();
        }
    }

    public int getCount() {
        return count;
    }
}

This approach helped eliminate the race condition and improved the stability of the application.