21.10 活动对象

import java.util.concurrent.*;
import java.util.*;
public class ActiveObjectDemo1 {
    private ExecutorService ex = Executors.newFixedThreadPool(1);
    private Random rand = new Random(47);
    private void pause(int factor) {
        try {
            TimeUnit.MILLISECONDS.sleep(100 + rand.nextInt(factor));
        } catch (InterruptedException e) {
            System.out.println("sleep() interrupted");
        }
    }
    public Future<Integer> calculateInt(final int x, final int y) {
        return ex.submit(new Callable<Integer>() {
            public Integer call() {
                System.out.println(Thread.currentThread().getName() + "->" + "starting " + x + " + " + y);
                pause(500);//模拟计算的过程
                return x + y;
            }
        });
    }
    public Future<Float> calculateFloat(final float x, final float y) {
        return ex.submit(new Callable<Float>() {
            public Float call() {
                System.out.println(Thread.currentThread().getName() + "->" + "starting " + x + " + " + y);
                pause(2000);
                return x + y;
            }
        });
    }
    public void shutdown() {
        ex.shutdown();
    }
    public static void main(String[] args) {
        ActiveObjectDemo d1 = new ActiveObjectDemo();
        // Prevents ConcurrentModificationException:
        List<Future<?>> results = new CopyOnWriteArrayList<Future<?>>();
        for (float f = 0.0f; f < 1.0f; f += 0.2f)
            results.add(d1.calculateFloat(f, f));
        for (int i = 0; i < 5; i++)
            results.add(d1.calculateInt(i, i));
        System.out.println("All asynch calls made");
        //1,results可能添加一个null 但其size为1
        while (results.size() > 0) {
            for (Future<?> f : results)
                //2，不阻塞 没关系，但其是一直遍历的
                if (f.isDone()) {
                    try {
                        System.out.println("res="+f.get());//4，获取结果的时候去阻塞的，获取完结果再去remove
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                    results.remove(f);//3，当把所有结果都移除后 while的size才为0
                }
        }
        d1.shutdown();
    }
}