A sample program using "Future" of Java. The result of this program is (e.g.) as follows. Execute a task... Execute other task. Task started. Task Ended. Other task finished. Time(Task result) is Mon May 27 19:43:41 MDT 2013

FutureSample.java

import java.util.Date;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class FutureSample {

  public static void main(String[] args) {
    try{
      FutureSample futureSample = new FutureSample();
      futureSample.exec();
    }
    catch(Exception ex){
      System.out.println(ex.getMessage());
      System.out.println(ex.getStackTrace());
    }
  }

  private void exec() throws InterruptedException, ExecutionException {
    //--------------------------------
    // Definition of a task(Callable).
    //--------------------------------
    Callable<Date> task = new Callable<Date>() {
      public Date call() throws InterruptedException {
        System.out.println("Task started.");
        Thread.sleep(3000);
        Date time = new Date();
        System.out.println("Task Ended.");
        return time;
      }
    };
    
    ExecutorService executor = Executors.newSingleThreadExecutor();
    
    // Execute the task and get a future for the task.
    System.out.println("Execute a task...");
    Future<Date> future = executor.submit(task);
    
    // Other tasks can be done with the task here, and this fact is important for using Future.
    System.out.println("Execute other task.");
    Thread.sleep(5000);
    System.out.println("Other task finished.");
    
    // Get the result of the task if it has been done. Otherwise this thread waits here.
    Date time = future.get();
    System.out.println("Time(Task result) is " + time);
  }
}