Java Executors newFixedThreadPool() Method

The newFixedThreadPool() method of Executors class creates a thread pool that reuses a fixed number of threads operating off a shared unbounded queue. At any point, at most n Threads will be active processing tasks. If additional tasks are submitted when all threads are active, they will wait in the queue until a thread is available.

Syntax

public static ExecutorService newFixedThreadPool(int nThreads)
public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory)

Parameter

nThreads - the number of threads in the pool

threadFactory - the factory to use when creating new threads

Returns

Throws

IllegalArgumentException

NullPointerException

Example 1

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class ExecutornewFixedThreadPoolExample1   {
    
   public static void main(final String[] arguments) throws InterruptedException {
      ThreadFactory ThreadFactory = Executors.defaultThreadFactory();
      ExecutorService excr = Executors.newFixedThreadPool(5 , ThreadFactory);
      ThreadPoolExecutor mypool = (ThreadPoolExecutor) excr;
      System.out.println("size of mypool: " + mypool.getPoolSize());
      excr.submit(new Threadimpl());
      excr.shutdown();
   }  

static class Threadimpl implements Runnable {
      public void run() {
         try {
            Long num = (long) (Math.random() * 30);
            System.out.println("Thread Name: " +Thread.currentThread().getName());
               TimeUnit.SECONDS.sleep(num);
            System.out.println("after sleep Thread Name: " +Thread.currentThread().getName());
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }
   }

}

Test it Now

Output:

size of mypool: 0
Thread Name: pool-1-thread-1
after sleep Thread Name: pool-1-thread-1

Example 2

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class ExecutornewFixedThreadPoolExample2   {
    
   public static void main(final String[] arguments) throws InterruptedException {
      ExecutorService excr = Executors.newFixedThreadPool(5);
      ThreadPoolExecutor mypool = (ThreadPoolExecutor) excr;
      System.out.println("size of mypool: " + mypool.getPoolSize());
      excr.submit(new Threadimpl());
      excr.shutdown();
   }  

static class Threadimpl implements Runnable {
      public void run() {
         try {
            Long num = (long) (Math.random() * 30);
            System.out.println("Thread Name: " +Thread.currentThread().getName());
               TimeUnit.SECONDS.sleep(num);
            System.out.println("after sleep Thread Name: " +Thread.currentThread().getName());
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }
   }

}

Test it Now

Output:

size of mypool: 0
Thread Name: pool-1-thread-1
after sleep Thread Name: pool-1-thread-1

Next TopicJava Executors

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