- All Known Subinterfaces:
- ExecutorService,- ScheduledExecutorService
- All Known Implementing Classes:
- AbstractExecutorService,- ForkJoinPool,- ScheduledThreadPoolExecutor,- ThreadPoolExecutor
public interface Executor
An object that executes submitted 
Runnable tasks. This
 interface provides a way of decoupling task submission from the
 mechanics of how each task will be run, including details of thread
 use, scheduling, etc.  An Executor is normally used
 instead of explicitly creating threads. For example, rather than
 invoking new Thread(new RunnableTask()).start() for each
 of a set of tasks, you might use:
  
 Executor executor = anExecutor();
 executor.execute(new RunnableTask1());
 executor.execute(new RunnableTask2());
 ...
 However, the Executor interface does not strictly require
 that execution be asynchronous. In the simplest case, an executor
 can run the submitted task immediately in the caller's thread:
  
 class DirectExecutor implements Executor {
   public void execute(Runnable r) {
     r.run();
   }
 }
 More typically, tasks are executed in some thread other than the
 caller's thread.  The executor below spawns a new thread for each
 task.
  
 class ThreadPerTaskExecutor implements Executor {
   public void execute(Runnable r) {
     new Thread(r).start();
   }
 }
 Many Executor implementations impose some sort of
 limitation on how and when tasks are scheduled.  The executor below
 serializes the submission of tasks to a second executor,
 illustrating a composite executor.
  
 class SerialExecutor implements Executor {
   final Queue<Runnable> tasks = new ArrayDeque<>();
   final Executor executor;
   Runnable active;
   SerialExecutor(Executor executor) {
     this.executor = executor;
   }
   public synchronized void execute(Runnable r) {
     tasks.add(() -> {
       try {
         r.run();
       } finally {
         scheduleNext();
       }
     });
     if (active == null) {
       scheduleNext();
     }
   }
   protected synchronized void scheduleNext() {
     if ((active = tasks.poll()) != null) {
       executor.execute(active);
     }
   }
 }
 The Executor implementations provided in this package
 implement ExecutorService, which is a more extensive
 interface.  The ThreadPoolExecutor class provides an
 extensible thread pool implementation. The Executors class
 provides convenient factory methods for these Executors.
 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.
- Since:
- 1.5
- 
Method Summary
- 
Method Details- 
executeExecutes the given command at some time in the future. The command may execute in a new thread, in a pooled thread, or in the calling thread, at the discretion of theExecutorimplementation.- Parameters:
- command- the runnable task
- Throws:
- RejectedExecutionException- if this task cannot be accepted for execution
- NullPointerException- if command is null
 
 
-