Future Interface

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;
class Demonstration {
    
    // Create and initialize a threadpool
    static ExecutorService threadPool = Executors.newFixedThreadPool(2);
  
    public static void main( String args[] ) throws Exception {
        System.out.println( "sum :" + findSum(10));
        threadPool.shutdown();
    }
  
    static int findSum(final int n) throws ExecutionException, InterruptedException {
        Callable<Integer> sumTask = new Callable<Integer>() {
            public Integer call() throws Exception {
                int sum = 0;
                for (int i = 1; i <= n; i++)
                    sum += i;
                return sum;
            }
        };
        Future<Integer> f = threadPool.submit(sumTask);
        return f.get();
    }  
  
  
}