Java Thread pool represents a group of worker threads that are waiting for the job and reuse many times.
In case of thread pool, a group of fixed size threads are created. A thread from the thread pool is pulled out and assigned a job by the service provider. After completion of the job, thread is contained in the thread pool again.
Better performance It saves time because there is no need to create new thread.
It is used in Servlet and JSP where container creates a thread pool to process the request.
Let's see a simple example of java thread pool using ExecutorService and Executors.