多线程 - 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

1、Executors.newFixedThreadPool(nThreads ):IllegalArgumentException - if nThreads <= 0
2、final指的是你的线程池地址不会变化，但是线程池里的线程没有限制。

Answer 2

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;
}