counter.java

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

/** 
* @author evivehealth on 08/02/19. 
*/
// Java program depicting 
// concurrent programming in action. 

// Runnable Class that defines the logic 
// of run method of runnable interface 
public class Counter implements Runnable 
{ 
	private final MainApp mainApp; 
	private final int loopLimit; 
	private final String task; 

	// Constructor to get a reference to the main class 
	public Counter 
		(MainApp mainApp, int loopLimit, String task) 
	{ 
		this.mainApp = mainApp; 
		this.loopLimit = loopLimit; 
		this.task = task; 
	} 

	// Prints the thread name, task number and 
	// the value of counter 
	// Calls pause method to allow multithreading to occur 
	@Override
	public void run() 
	{ 
		for (int i = 0; i < loopLimit; i++) 
		{ 
			System.out.println("Thread: " + 
			Thread.currentThread().getName() + " Counter: "
							+ (i + 1) + " Task: " + task); 
			mainApp.pause(Math.random()); 
		} 
	} 
} 
class MainApp 
{ 

	// Starts the threads. Pool size 2 means at any time 
	// there can only be two simultaneous threads 
	public void startThread() 
	{ 
		ExecutorService taskList = 
						Executors.newFixedThreadPool(2); 
		for (int i = 0; i < 5; i++) 
		{ 
			// Makes tasks available for execution. 
			// At the appropriate time, calls run 
			// method of runnable interface 
			taskList.execute(new Counter(this, i + 1, 
									"task " + (i + 1))); 
		} 

		// Shuts the thread that's watching to see if 
		// you have added new tasks. 
		taskList.shutdown(); 
	} 

	// Pauses execution for a moment 
	// so that system switches back and forth 
	public void pause(double seconds) 
	{ 
		try
		{ 
			Thread.sleep(Math.round(1000.0 * seconds)); 
		} 
		catch (InterruptedException e) 
		{ 
			e.printStackTrace(); 
		} 
	} 

	// Driver method 
	public static void main(String[] args) 
	{ 
		new MainApp().startThread(); 
	} 
}