java.util.concurrent
Interface Executor

All Known Subinterfaces:

ExecutorService

All Known Implementing Classes:

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. 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();
     }
 }

However, tasks are typically executed in a different thread 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();
     }
 }

Most Executor implementations will 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 {
     LinkedBlockingQueue tasks = new LinkedBlockingQueue<Runnable>();
     Executor executor;
     Runnable active;

     SerialExecutor(Executor executor) {
         this.executor = executor;
     }

     public synchronized void execute(final Runnable r) {
         tasks.offer(new Runnable() {
             public void run() {
                 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.

Since:

1.5

Author:

Doug Lea

Method Summary

void	execute(java.lang.Runnable command) Executes the given command at some time in the future.

Method Detail

execute

public void execute(java.lang.Runnable command)

Executes 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 the Executor implementation.

Parameters:

command - the runnable task

Throws:

RejectedExecutionException - if this task cannot be accepted for execution.

java.lang.NullPointerException - if command is null