java 스레드의FutureTask

package com.concurrent;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;

import junit.framework.TestCase;

public class TestFutureTask extends TestCase {
	private static final Random random = new Random();

	private static final int COUNT = 5;

	public void testFutureTask() {
		ExecutorService executorService = Executors.newFixedThreadPool(COUNT);
		List<FutureTask<Integer>> list = new ArrayList<FutureTask<Integer>>();

		for (int i = 0; i < COUNT; i++) {
			final int index = i;
			FutureTask<Integer> ft = new FutureTask<Integer>(new Callable<Integer>() {

				@Override
				public Integer call() throws Exception {
					int result = random.nextInt(10);
					System.out.println("call " + index + ", result = " + result);
					return result;
				}
			}) {

				@Override
				protected void done() {
					System.out.println("done " + index);
				}

			};
			list.add(ft);
			executorService.submit(ft);
		}

		int sum = 0;
		for (FutureTask<Integer> ft : list) {
			try {
				sum += ft.get();
			} catch (InterruptedException e) {
				e.printStackTrace();
			} catch (ExecutionException e) {
				e.printStackTrace();
			}
		}

		System.out.println("sum = " + sum);
		executorService.shutdown();
	}

}

call 0, result = 6
call 1, result = 5
call 2, result = 4
done 1
done 2
done 0
call 3, result = 2
done 3
call 4, result = 9
done 4
sum = 26