java - 如何关闭 CompletionService

Question

我需要做这样的事情:

ExecutorService executor = Executors.newFixedThreadPool(2);
CompletionService<Boolean> completionService = new ExecutorCompletionService<>(executor);
int i = 0;
while (i < 40) {
  completionService.submit(getTask());
  i++;
}
executor.shutdown();
System.out.println("SHUTDOWN");

但是在 executor 对象上调用 shutdown 之后 completionService 仍然执行任务。

我怎样才能让它停止？

有没有办法停止ExecutorService，等待当前正在执行的任务完成？

Answer 1

ExecutorService 将继续执行已经提交的任务，但不允许提交更多任务，来自 documentation

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. Invocation has no additional effect if already shut down.
_{emphasis mine}

所以您已经提交了 40 个任务，这些任务将在关机前执行。

如果你想强制关机。您可以使用 shutdownNow :

Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.
_{emphasis mine}

这将根据需要放弃计划任务。

注意:停止进行中的任务完全是另一个问题。