Java中在子线程中获取固定大小的连接池出现错误，如果解释？

Question

问题1. 不太好描述，直接看代码吧public class QueueConsumer extends EndPoint implements Runnable {    // 线程池    private ExecutorService executor = null;    public QueueConsumer(String endPointName, String hosts, String ports,            String username, String password) throws Exception {        super(endPointName, hosts, ports, username, password);        // 初始化线程池        executor = Executors.newCachedThreadPool();    }    @Override    public void run() {        try {            QueueingConsumer consumer = new QueueingConsumer(channel);            channel.basicConsume(endPointName, false, consumer);            while (true) {                // 信息到达时                Delivery delivery = consumer.nextDelivery();                                // 初始化业务线程对象                BusinessClient businessClient = new BusinessClient(channel, delivery);                // 执行任务                executor.execute(businessClient);            }        } catch (Exception e) {            LogUtil.printException("消息队列异常", e, LogUtil.LOG_LEVEL_ERROR);        } finally {            try {                close();            } catch (Exception e) {                LogUtil.printException("关闭消息队列异常", e, LogUtil.LOG_LEVEL_ERROR);public class BusinessClient implements Runnable {    ... 省略        // 主要代码    List<Callable<Object>> taskList = new ArrayList<Callable<Object>>();    for (BaseRequestData<BaseResponseData> queryData : queryDataLst) {        QueryThread queryThread = new QueryThread(queryData);        taskList.add(queryThread);    }    // 问题点：此处使用Executors.newFixedThreadPool(i)会抛出IllegalArgumentException              但是使用Executors.newCachedThreadPool()则不会有问题.不是很理解，为什么此处不可以用newFixedThreadPool(i)?                  ExecutorService executor = Executors.newCachedThreadPool();    List<Future<Object>> results = executor.invokeAll(taskList);    executor.shutdown();        ... 省略}问题2. 我如果定义一个线程池工厂，将线程池定义为static final，每个需要并发的地方都使用工厂来获得线程池，   那么问题来了，我这个线程池会自动扩展或者释放线程吗？      纯粹自学的Java, 对于一些基础知识不是很理解，望不吝赐教！谢谢

Answer 1

Executors.newFixedThreadPool(i) 此处的i取值范围不对吧，如果你出现IllegalArgumentException，说明这个值是小于0的，这是不允许的。

Executors.newFixedThreadPool(i) 最终会走下如下逻辑。

public ThreadPoolExecutor(int corePoolSize,

                          int maximumPoolSize,

                          long keepAliveTime,

                          TimeUnit unit,

                          BlockingQueue<Runnable> workQueue,

                          ThreadFactory threadFactory,

                          RejectedExecutionHandler handler) {

    if (corePoolSize < 0 ||

        maximumPoolSize <= 0 ||

        maximumPoolSize < corePoolSize ||

        keepAliveTime < 0)

        throw new IllegalArgumentException();

    if (workQueue == null || threadFactory == null || handler == null)

        throw new NullPointerException();

    this.corePoolSize = corePoolSize;

    this.maximumPoolSize = maximumPoolSize;

    this.workQueue = workQueue;

    this.keepAliveTime = unit.toNanos(keepAliveTime);

    this.threadFactory = threadFactory;

    this.handler = handler;

}