Difference between Fixed thread pool and cached thread pool.

Executor framework are designed using thread pool concept. Thread pool is the way to reuse the already created thread instead of creating a new thread every time to execute the current task.

Executors class provides a factory method to create thread pools. The ThreadPoolExecutor class is the base implementation for the executors that are returned from many of the Executors  factory methods.

Example of Fixed thread pool

public class Main {
   public static void main(String args[]) throws InterruptedException {
      ExecutorService executors = Executors.newFixedThreadPool(4);
      CountDownLatch latch= new CountDownLatch(2);
      executors.submit(new Service1(latch));
      executors.submit(new Service2(latch));
      latch.await();
      System.out.println("Done");
   }

import java.util.concurrent.CountDownLatch;
public class Service1 implements Runnable {
   CountDownLatch latch;
   public Service1(CountDownLatch latch) {
      super();
      this.latch = latch;
   }
   @Override
   public void run() {
      try {
         Thread.sleep(20000);
      } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
         }
         latch.countDown();
         System.out.println("Services2"+latch.getCount());
      }
   }
   import java.util.concurrent.CountDownLatch;
   public class Service2 implements Runnable {
      CountDownLatch latch;
      public Service2(CountDownLatch latch) {
         super();
         this.latch = latch;
      }
      @Override
      public void run() {
         try {
            Thread.sleep(20000);
         } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }
   latch.countDown();
   System.out.println("Services2"+latch.getCount());
   }
}