Examples of Atomic in Java

Problematic Code :

package com.demo.atomicDemo;

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

public class NonAtomicDemo {
	public static void main(String[] args) throws InterruptedException {
		ExecutorService executerService = null; 
		 Counter count = new Counter();
		 
		 executerService = Executors.newFixedThreadPool(2);
		 
		 Runnable task1 = () -> {
			for(int i=0;i<2000000;i++) {
				count.incremenetCounter();
//				System.out.println(Thread.currentThread().getName()+" ---- "+count.getCounter());
			}
		 };
		 Runnable task2 = () -> {
			for(int i=0;i<8000000;i++) {
				count.incremenetCounter();
//				System.out.println(Thread.currentThread().getName()+" ---- "+count.getCounter());
			}
		 };		 
		 executerService.submit(task1);
		 executerService.submit(task2);
		 executerService.awaitTermination(1, TimeUnit.SECONDS);
		 executerService.shutdown();
		 System.out.println(count.getCounter());
	    }	
	}
class Counter{
	private int counter;
	public int getCounter() {
		return counter;
	}

	public void incremenetCounter() { counter = counter+1; }
}

Ouptut

Fixing the code by using volatile and synchronized but it is slow

class Counter{
	private volatile int counter;
	public int getCounter() {
		return counter;
	}

	public synchronized void incremenetCounter() { counter = counter+1; }
}

Why synchronized is slow you ask ?

• Because to enter into the synchronized block between threads there has to be a lot of context switching