java - 使用 newSingleThreadScheduledExecutor 调度多个任务

Question

如果我为 ScheduledExecutorService 安排了多个任务，但我已经确定只能有一个线程来执行所有任务，每个任务会按顺序执行吗？

例如:在下面的场景中会发生什么

ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
scheduler.scheduleWithFixedDelay(new Runnable{void run(){....}}, 6000,6000,TimeUnit.MILLISECONDS);
scheduler.scheduleWithFixedDelay(new Runnable{void run(){....}}, 6000,6000,TimeUnit.MILLISECONDS);

Answer 1

来自javadoc:

Creates an Executor that uses a single worker thread operating off an unbounded queue. (Note however that if this single thread terminates due to a failure during execution prior to shutdown, a new one will take its place if needed to execute subsequent tasks.) Tasks are guaranteed to execute sequentially, and no more than one task will be active at any given time. Unlike the otherwise equivalent newFixedThreadPool(1) the returned executor is guaranteed not to be reconfigurable to use additional threads.

http://download.java.net/jdk7/archive/b123/docs/api/java/util/concurrent/Executors.html#newSingleThreadExecutor(java.util.concurrent.ThreadFactory)