What are an Executors in Java?

[Beter 2 Burn Out]

Hi friends,
I have recently completed with the basic functions of the threads. Now I have gone through the term executors of which I am having no idea. So thought to post here, as your help is very useful. So please tell me what are an Executors in Java? Hope that someone had got the point. Explain me as soon as possible.!!

[Viensterrr]

Normally close connection between the task being done by a new thread, as defined by its Runnable object, and the thread itself, as defined by a Thread object. In large-scale applications, it makes sense to separate thread management and creation from the rest of the application. Objects that encapsulate these functions are known as executors. An object that executes submitted Runnable tasks. An Executor interface does not strictly require that execution be asynchronous.

[Warner]

The following subsections describe executors in detail :

• Executor Interfaces define the three executor object types.
• Thread Pools are the most common kind of executor implementation.

The java.util.concurrent package defines three executor interfaces :

1. Executor, a simple interface that supports launching new tasks.
2. ExecutorService, a subinterface of Executor, which adds features that help manage the lifecycle, both of the individual tasks and of the executor itself.
3. ScheduledExecutorService, a subinterface of ExecutorService, supports future and/or periodic execution of tasks.

[Allan.d]

The Executor interface provides a single method, execute, designed to be a drop-in replacement for a common thread-creation idiom. If r is a Runnable object, and e is an Executor object you can replace

(new Thread(r)).start();

with the

e.execute(r);

[void]

The following is an example of Executors in coding :

import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class ClassDemo {
  ExecutorService executor = Executors.newFixedThreadPool(3);

  public void start() throws IOException {
    int i=0;
    while (!executor.isShutdown())
      executor.submit(new MyThread(i++));
  }

  public void shutdown() throws InterruptedException {
    executor.shutdown();
    executor.awaitTermination(30, TimeUnit.SECONDS);
    executor.shutdownNow();
  }

  public static void main(String argv[]) throws Exception {
    new ClassDemo().start();
  }
}

class MyThread implements Runnable {
private int i;
  MyThread(int i) {
  this.i = i;
  }

  public void run() {
    System.out.println("I am in thread:"+i);
    
  }
}