How did you implement multithreading in your projects and what problems did you encounter?

In my projects, I used several approaches to implement multithreading:

• Thread and Runnable — basic Java classes for creating threads.
• ExecutorService — a thread pool for managing and reusing threads.
• Future and Callable — for obtaining results from asynchronous tasks.
• Synchronization (synchronized, Lock) — for managing access to shared resources.

The main issues I encountered:

• Race conditions — when multiple threads modify shared data simultaneously without synchronization.
• Deadlocks — when threads wait for each other, blocking resources.
• Visibility issues — when changes in one thread are not visible to another due to caching.

Example of using ExecutorService:

ExecutorService executor = Executors.newFixedThreadPool(2);

Callable<Integer> task = () -> {
    // Some computational task
    return 123;
};

Future<Integer> future = executor.submit(task);

try {
    Integer result = future.get();
    System.out.println("Result: " + result);
} catch (InterruptedException | ExecutionException e) {
    e.printStackTrace();
}

executor.shutdown();

This approach allows efficient management of threads and obtaining results from asynchronous computations, minimizing synchronization issues.