Java – Thread Pools (Executor Framework) | Code Factory

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• Creating a new thread for every job may create performance on memory problems, to overcome this we should go for Thread Pool.
• Thread pool is a pool of already created threads, ready to do out job.
• Java 1.5v introduces thread pool framework to implement thread pools. Thread Pool also know as executor framework.
• We can create a thread pool as foolows.

ExecutorService service = Executors.newFixedThreadPool(3);

• We can submit a Runnable job by using a submit method service.submit(job).
• We can shutdown executor service by using shutdown method service.shutdown().

package com.example.thread;

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

/**
 * @author code.factory
 *
 */
public class ExecutorTest {
	public static void main(String... args) {
		PrintJob jobs[] = {
			new PrintJob("Narendra"),
			new PrintJob("Amit"),
			new PrintJob("Yogi"),
			new PrintJob("Rupani"),
			new PrintJob("Mukesh"),
			new PrintJob("Anil"),
		};
		ExecutorService service = Executors.newFixedThreadPool(3);
		for(PrintJob job : jobs) {
			service.submit(job);
		}
		service.shutdown();
	}
}

class PrintJob implements Runnable {
	String name;
	public PrintJob(String name) {
		this.name = name;
	}
	
	public void run() {
		System.out.println(name + " job started by thread " + Thread.currentThread().getName());
		try {
			Thread.sleep(2000);
		} catch(InterruptedException e) {
			e.printStackTrace();
		}
	}
}

Output :

Narendra job started by thread pool-1-thread-1
Yogi job started by thread pool-1-thread-3
Amit job started by thread pool-1-thread-2
Rupani job started by thread pool-1-thread-1
Anil job started by thread pool-1-thread-3
Mukesh job started by thread pool-1-thread-2

• In the above exmple 3 threads are responsible to execute 6 jobs. So that a single thread can be reuse for multiple jobs.
• While designing web servers and application servers we can use thread pool concept.