Types of Thread Pool

 In Java, the java.util.concurrent.Executors class provides several methods to create different types of thread pools:

1. Fixed Thread Pool (Executors.newFixedThreadPool(int nThreads)): This method creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue. If any thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks.

        ExecutorService executorService = Executors.newFixedThreadPool(5);

• Pros: This type of thread pool can be used when you know the maximum number of concurrent tasks your application will need to execute. It provides a fixed number of threads that can work off an unbounded queue.
• Cons: Since the queue is unbounded, if tasks are submitted faster than the threads can process them, the queue can grow indefinitely, eventually running out of memory.

2. Single Thread Executor (Executors.newSingleThreadExecutor()): This method creates an Executor that uses a single worker thread operating off an unbounded queue.

        ExecutorService executorService = Executors.newSingleThreadExecutor();

• Pros: This type of thread pool can be used when you need to execute tasks sequentially in the order they are added.
• Cons: Since there's only one thread, tasks are processed sequentially, so this type of executor is not suitable for tasks that can be run in parallel.

3. Cached Thread Pool (Executors.newCachedThreadPool()): This method creates a thread pool that creates new threads as needed, but will reuse previously constructed threads when they are available.

        ExecutorService executorService = Executors.newCachedThreadPool();

• Pros: This type of thread pool is suitable for programs that execute many short-lived asynchronous tasks. It will create as many threads as it needs to execute the tasks concurrently, reusing threads when possible.
• Cons: Since new threads are created as needed, it can create a high number of threads, which can lead to system resource exhaustion.

4. Scheduled Thread Pool (Executors.newScheduledThreadPool(int corePoolSize)): This method creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.

        ScheduledExecutorService executorService = Executors.newScheduledThreadPool(5);

• Pros: This type of thread pool can be used when you need to schedule tasks to be executed periodically or after a certain delay.
• Cons: It's more complex than other types of executors due to the scheduling capabilities.

5. Work Stealing Thread Pool (Executors.newWorkStealingPool(int parallelism)): This method creates a work-stealing thread pool using all available processors as its target parallelism level.

        ExecutorService executorService = Executors.newWorkStealingPool();

• Pros: This type of thread pool is suitable for tasks that spawn other tasks (fork/join tasks).
• Cons: It's more complex than other types of executors due to the work-stealing algorithm.

Remember to always shut down your executor service when you're done using it:

        executorService.shutdown();