java如何更改ScheduledExecutorService中的线程池大小？

Question

我需要带有动态线程池的ScheduledExecutorService。我想动态更改线程池大小。我该怎么做

class ExecutorTask {
    private ScheduledExecutorService service;

    public void add(Task task) {
        // I need thread pool size == count added tasks.
        service.scheduleAtFixedRate(this::start, 0, 10, TimeUnit.SECONDS);
    }
}

也许你能给我建议另一个线程池

Answer 1

你可以用ScheduledThreadPoolExecutor轻松做到这一点

    //Init executor
    int initialPoolSize = 5;
    ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(initialPoolSize);

    //[...] do something

    //Change max size
    int newPoolSize = 10;
    executor.setCorePoolSize(newPoolSize);

注意，继承的方法setMaximumPoolSize(int)有no effect on ScheduledThreadPoolExecutor。要更改池大小，需要更改corePoolSize：

While this class inherits from ThreadPoolExecutor, a few of the inherited tuning methods are not useful for it. In particular, because it acts as a fixed-sized pool using corePoolSize threads and an unbounded queue, adjustments to maximumPoolSize have no useful effect. Additionally, it is almost never a good idea to set corePoolSize to zero or use allowCoreThreadTimeOut because this may leave the pool without threads to handle tasks once they become eligible to run.

Answer 2

也许这就是您在Executors Util类中寻找的：

ExecutorService executorService = Executors.newScheduledThreadPool(5)

Answer 3

您可以使用setCorePoolSize(int)方法来实现这一点

还可以使用Executors.newCachedThreadPool将线程池大小创建为ThreadPoolExecutor

如果需要执行新任务，ThreadPoolExecutor会创建新线程，并使用Executors.newCachedThreadPool()重用现有线程