Tell us about your experience with multithreading. What level of API do you use?

In working with multithreading in Java, I use different API levels depending on the task:

• Low-level tools: synchronized, wait/notify for simple synchronization cases.
• High-level constructs from java.util.concurrent:
  • ExecutorService and ThreadPoolExecutor for thread management.
  • Future and Callable for asynchronous tasks with results.
  • CountDownLatch, CyclicBarrier, Semaphore for thread coordination.
  • ConcurrentHashMap, BlockingQueue for thread-safe collections.
• Functional style with CompletableFuture: for building chains of asynchronous operations.

Example of using ExecutorService:

ExecutorService executor = Executors.newFixedThreadPool(4);
Future<Integer> future = executor.submit(() -> {
    // Long operation
    return 42;
});

Integer result = future.get();
executor.shutdown();

It is also important to consider proper thread lifecycle management and avoid races and deadlocks. For complex systems, I apply patterns such as Producer-Consumer and use profiling tools to identify concurrency issues.