java - SingleThreadExecutor VS 普通线程

Question

除了 Executor 接口(interface)比普通线程有一些优势(例如管理)之外，在做:

ExecutorService executor = Executors.newSingleThreadExecutor();
executor.submit(runnable);

和:

Thread thread = new Thread(runnable);
thread.start();

我在这里只询问一个线程。

Answer 1

Executors#newSingleThreadExecutor() 在后台创建 ThreadPoolExecutor 对象，
在这里查看代码:http://www.docjar.com/html/api/java/util/concurrent/Executors.java.html

  133       public static ExecutorService newSingleThreadExecutor() {
  134           return new FinalizableDelegatedExecutorService
  135               (new ThreadPoolExecutor(1, 1,
  136                                       0L, TimeUnit.MILLISECONDS,
  137                                       new LinkedBlockingQueue<Runnable>()));
  138       }

documentation of ThreadPoolExecutor解释它在什么情况下会带来优势:

Thread pools address two different problems: they usually provide improved performance when executing large numbers of asynchronous tasks, due to reduced per-task invocation overhead, and they provide a means of bounding and managing the resources, including threads, consumed when executing a collection of tasks. Each ThreadPoolExecutor also maintains some basic statistics, such as the number of completed tasks.

如果你只需要偶尔运行一次单线程(比如每小时一次)，那么就性能而言，使用 ThreadPoolExecutor 可能会更慢，因为你需要实例化整个机器(池 + 线程)，然后将其从内存中丢弃。

但是如果您想经常使用这个单线程(比如每 15 秒一次)，那么优点是您创建池和线程仅一次，将其保存在内存中，然后全部使用时不时地创建一个新线程可以节省时间(如果您想每 15 秒左右使用一次，这可能会非常昂贵)。