Question

我有ThreadPoolExecutor corePoolSize=1和maxPoolSize=1，支持无限LinkedBlockingQueue。

让我们说在时间t，池中的单个线程正在处理任务T0。队列中有一个任务T1。

在处理任务T0期间设置corePoolSize=0会发生什么？

单个线程将处理任务T1，然后变为空闲并被销毁（因为新的corePoolSize）或
在处理任务T0之后单线程变为空闲，因此被破坏，并且任务T1保持在队列中，直到corePoolSize稍后增加> 0 ？

在线程池执行程序的上下文中，对于一个空闲＆＃34;空闲＆＃34;是什么意思？

Answer 1

单线程也将处理任务T1。之后，它可能会在闲置一段时间后被销毁。

线程有许多场景处于空闲状态。在下面的SO帖子中解释了这一点： When is a Java thread idle?

Answer 2

根据以下代码片段：java.util.concurrent.ThreadPoolExecutor。

当我们调用setMaximumPoolSize（..）

时，池将变为空

public void setMaximumPoolSize(int maximumPoolSize) {
        if (maximumPoolSize <= 0 || maximumPoolSize < corePoolSize)
            throw new IllegalArgumentException();
        this.maximumPoolSize = maximumPoolSize;
      -->>  if (workerCountOf(ctl.get()) > maximumPoolSize)
            interruptIdleWorkers();
    }

但是当我们再次尝试使用execute（..）方法执行T1时，所述注释可能会暗示接下来会发生什么。

/*
         * Proceed in 3 steps:
         *
         * 1. If fewer than corePoolSize threads are running, try to
         * start a new thread with the given command as its first
         * task.  The call to addWorker atomically checks runState and
         * workerCount, and so prevents false alarms that would add
         * threads when it shouldn't, by returning false.
         *
         * 2. If a task can be successfully queued, then we still need
         * to double-check whether we should have added a thread
         * (because existing ones died since last checking) or that
         * the pool shut down since entry into this method. So we
         * recheck state and if necessary roll back the enqueuing if
         * stopped, or start a new thread if there are none.
         *
         * 3. If we cannot queue task, then we try to add a new
         * thread.  If it fails, we know we are shut down or saturated
         * and so reject the task.
         */

我的回答仍有争议：）

ThreadPoolExecutor：在运行时更改corePoolSize

2 个答案: