[Java] Thread pool

Thread pool

- Thread pool represents a group of worker threads that are waiting for the job and reuse many times

- a group of fixed size threads are created

- A thread from thread pool is pulled out and assigned a job by service provider

- After completion of the job, thread is contained in the thread pool again

1. Advantage

- Better performance

- It saves time because there is no need to create new thread

2. Real time usage

- It is used in Servlet and JSP  where container creates a thread pool to process the request

3. Example

import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; class WorkerThread implements Runnable{ private String message; public WorkerThread(String s){ this.message = s; } public void run(){ System.out.println(Thread.currentThread().getName()+"Start message:"+message); //call processmessage method processmessage(); System.out.println(Thread.currentThread().getName()+"End"); } private void processmessage(){ try{ Thread.sleep(2000); }catch(InterruptedException e){ e.printStackTrace(); } } } public class ThreadPool { public static void main(String[]args){ //creating a pool of 5 thread ExecutorService executor = Executors.newFixedThreadPool(5); for(int i = 0; i<10; i++){ Runnable worker = new WorkerThread(""+i); executor.execute(worker); } executor.shutdown(); while(!executor.isTerminated()){ } System.out.println("Finish all Threads"); } }