Example for ExecutorService in Java

gistfile1.java

package aa;

import java.text.MessageFormat;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;

public class Pooling {
  
  private static final int NUMBER_OF_THREADS = 3;

	public static void main(String[] args) {
		final ExecutorService executor = Executors.newFixedThreadPool(NUMBER_OF_THREADS);
		
		for (int i = 0; i < 10; i++) {
			// Work items will be executed in an indeterministic order in the available threads.
			// At most NUMBER_OF_THREADS work items will be executed at the same time.
			executor.execute(createWorkItemWithOrderNumber(i));			
		}
		
	}

	static final AtomicInteger concurrentExecutions = new AtomicInteger(0); 
	
	private static Runnable createWorkItemWithOrderNumber(final int orderNumber) {
		return new Runnable() {
			@Override
			public void run() {
				int numberOfConcurrentExecutions = concurrentExecutions.incrementAndGet();
				
				System.out.println(MessageFormat.format("This is the {0}th work item running in thread {1}, # of concurrent executions {2}",
						orderNumber, Thread.currentThread().getName(), numberOfConcurrentExecutions));
				
				concurrentExecutions.decrementAndGet();
			}
		};
	}

//		Output will be similar to this:
//			This is the 0th work item running in thread pool-1-thread-1
//			This is the 2th work item running in thread pool-1-thread-3
//			This is the 4th work item running in thread pool-1-thread-3
//			This is the 3th work item running in thread pool-1-thread-1
//			This is the 5th work item running in thread pool-1-thread-3
//			This is the 6th work item running in thread pool-1-thread-1
//			This is the 7th work item running in thread pool-1-thread-3
//			This is the 8th work item running in thread pool-1-thread-1
//			This is the 9th work item running in thread pool-1-thread-3
//			This is the 1th work item running in thread pool-1-thread-2
	
}