Java.Multithreading.What is a thread pool?

A thread pool is a programming construct used to manage a group of worker threads for executing tasks concurrently. Instead of creating and destroying a thread for each task (which is expensive), a thread pool reuses a fixed number of threads to execute many tasks efficiently

🧠 Concept in Simple Terms

Imagine a restaurant kitchen with a team of chefs (threads). Customers (tasks) place orders. Instead of hiring a new chef for each order, the kitchen has a set number of chefs ready to cook incoming orders. When a chef finishes one order, they take the next.

⚙️ How It Works

• A thread pool has:
  • A queue of tasks (waiting to be executed)
  • A fixed or dynamic number of worker threads
• When you submit a task:
  • If a thread is available, it executes the task.
  • If all threads are busy, the task waits in the queue.

✅ Benefits

• Performance: Reuses threads, avoiding overhead of thread creation/destruction.
• Scalability: Prevents your system from being overwhelmed by too many threads.
• Resource management: You control how many threads run at once.

🧰 In Java: Example with Executors

ExecutorService executor = Executors.newFixedThreadPool(4);

executor.submit(() -> {
    System.out.println("Running task in thread: " + Thread.currentThread().getName());
});

executor.shutdown(); // Optional: shuts down the executor when done

🛠️ Types of Thread Pools (Java)

• newFixedThreadPool(n): Fixed number of threads
• newCachedThreadPool(): Creates new threads as needed, reuses old ones
• newSingleThreadExecutor(): One thread for all tasks
• newScheduledThreadPool(n): For delayed or periodic tasks