我只是在探索java.util.concurrent包。

我学到类’Future’有一个方法boolean cancel(boolean mayInterruptIfRunning)

请附上我写的测试代码

package com.java.util.concurrent;

import java.util.concurrent.Callable;

import java.util.concurrent.FutureTask;

import java.util.concurrent.ScheduledFuture;

import java.util.concurrent.ScheduledThreadPoolExecutor;

public class FutureTester {

/**

* @param args

* @throws InterruptedException

*/

public static void main(String[] args) throws InterruptedException {

// TODO Auto-generated method stub

int poolCnt = 1;

Callable numberPrinter = null;

ScheduledThreadPoolExecutor schPool = new ScheduledThreadPoolExecutor(

poolCnt);

ScheduledFuture[] numPrinterFutures = new ScheduledFuture[poolCnt];

FutureTask[] futureTask = new FutureTask[poolCnt];

for (int i = 0; i < poolCnt; i++) {

numberPrinter = new NumberPrinter();

futureTask[i] = new FutureTask(numberPrinter);

/*

* numPrinterFutures[i] = (ScheduledFuture) schPool

* .schedule(futureTask[i], 0, TimeUnit.MILLISECONDS);

*/

numPrinterFutures[i] = (ScheduledFuture) schPool

.submit(futureTask[i]);

}

//Thread.sleep(30);

if (numPrinterFutures.length > 0) {

System.out.println("Task completed ? "

+ numPrinterFutures[0].isDone());

System.out.println("Task cancelled ? "

+ numPrinterFutures[0].cancel(true));

System.out.println("Is task cancelled ? "

+ numPrinterFutures[0].isCancelled());

}

}

}

class NumberPrinter implements Callable {

private int counter = 10;

@Override

public NumberPrinter call() throws Exception {

// TODO Auto-generated method stub

while (counter > 0) {

if (Thread.interrupted()) {/*OUCH !!!*/

return null;

}

System.out.println("counter = " + (counter--));

}

return this;

}

}

在本来，我假设取消一个任务也会停止运行的线程的执行(“OUCH”部分不包括在内)。但是我得到的输出如下：

counter = 10

Task completed ? false

counter = 9

Task cancelled ? true

counter = 8

Is task cancelled ? true

counter = 7

counter = 6

counter = 5

counter = 4

counter = 3

counter = 2

counter = 1

在进一步阅读stackoverflow本身，据说

>“取消”方法只能停止“未启动”作业(与方法的api描述相矛盾)

>取消方法只是中断正在运行的线程

必须从run()方法返回

因此，我包含了’OUCH’部分 – 一个循环检查中断;输出如下：

Task completed ? false

counter = 10

Task cancelled ? true

Is task cancelled ? true

题 ：

如果应该写一些类似于“OUCH”部分的东西来停止运行的线程，那么取消方法的实用程序/值是多少。如果线程无法通过取消停止，那么如何在FutureTask中包装Callable？我俯瞰的是什么设计/概念/逻辑部分？