java.util.concurrent
Interface Executor

All Known Subinterfaces:
ExecutorService sample code for java.util.concurrent.ExecutorService definition code for java.util.concurrent.ExecutorService , ScheduledExecutorService sample code for java.util.concurrent.ScheduledExecutorService definition code for java.util.concurrent.ScheduledExecutorService
All Known Implementing Classes:
AbstractExecutorService sample code for java.util.concurrent.AbstractExecutorService definition code for java.util.concurrent.AbstractExecutorService , ScheduledThreadPoolExecutor sample code for java.util.concurrent.ScheduledThreadPoolExecutor definition code for java.util.concurrent.ScheduledThreadPoolExecutor , ThreadPoolExecutor sample code for java.util.concurrent.ThreadPoolExecutor definition code for java.util.concurrent.ThreadPoolExecutor

public interface Executor

An object that executes submitted Runnable sample code for java.lang.Runnable definition code for java.lang.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 LinkedBlockingQueue<Runnable>();
     final 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 sample code for java.util.concurrent.ExecutorService definition code for java.util.concurrent.ExecutorService , which is a more extensive interface. The ThreadPoolExecutor sample code for java.util.concurrent.ThreadPoolExecutor definition code for java.util.concurrent.ThreadPoolExecutor class provides an extensible thread pool implementation. The Executors sample code for java.util.concurrent.Executors definition code for java.util.concurrent.Executors class provides convenient factory methods for these Executors.

Since:
1.5

Method Summary
 void execute sample code for java.util.concurrent.Executor.execute(java.lang.Runnable) definition code for java.util.concurrent.Executor.execute(java.lang.Runnable) (Runnable sample code for java.lang.Runnable definition code for java.lang.Runnable  command)
          Executes the given command at some time in the future.
 

Method Detail

execute sample code for java.util.concurrent.Executor.execute(java.lang.Runnable) definition code for java.util.concurrent.Executor.execute(java.lang.Runnable)

void execute(Runnable sample code for java.lang.Runnable definition code for 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 sample code for java.util.concurrent.RejectedExecutionException definition code for java.util.concurrent.RejectedExecutionException - if this task cannot be accepted for execution.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if command is null