Java 执行器服务 : should I put a lock before to use execute?

Question

我有一个组织如下的类:

public class MyClass {

   ExecutorService pool;

   public MyClass(){
     pool = ... //inited by a class that implements ExecutorService
   }

   public final void submit(Runnable run){
        pool.execute(run);
   }
}

submit 方法是线程安全的还是我应该使用基于Lock 的系统？例如

   ReentrantLock look  = new ReentrantLock();

   public final void submit(Runnable run){
        lock.lock();
        try{ pool.execute(run); } finally{lock.unlock();}
   }

Answer 1

不，调用 ExecutorService#submit 时不需要锁.

Memory consistency effects: Actions in a thread prior to the submission of a Runnable or Callable task to an ExecutorService happen-before any actions taken by that task, which in turn happen-before the result is retrieved via Future.get().

或调用 Executor#execute 时:

Memory consistency effects: Actions in a thread prior to submitting a Runnable object to an Executor happen-before its execution begins, perhaps in another thread.