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- All Known Subinterfaces:
ExecutorService,ScheduledExecutorService
- All Known Implementing Classes:
AbstractExecutorService,ForkJoinPool,ScheduledThreadPoolExecutor,ThreadPoolExecutor
public interface ExecutorAn object that executes submittedRunnabletasks. 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. AnExecutoris normally used instead of explicitly creating threads. For example, rather than invokingnew Thread(new RunnableTask()).start()for each of a set of tasks, you might use:
However, theExecutor executor = anExecutor(); executor.execute(new RunnableTask1()); executor.execute(new RunnableTask2()); ...Executorinterface 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:
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 DirectExecutor implements Executor { public void execute(Runnable r) { r.run(); } }
Manyclass ThreadPerTaskExecutor implements Executor { public void execute(Runnable r) { new Thread(r).start(); } }Executorimplementations 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.
Theclass 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); } } }Executorimplementations provided in this package implementExecutorService, which is a more extensive interface. TheThreadPoolExecutorclass provides an extensible thread pool implementation. TheExecutorsclass provides convenient factory methods for these Executors.Memory consistency effects: Actions in a thread prior to submitting a
Runnableobject to anExecutorhappen-before its execution begins, perhaps in another thread.- Since:
- 1.5
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description voidexecute(Runnable command)Executes the given command at some time in the future.
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Method Detail
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execute
void execute(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 theExecutorimplementation.- Parameters:
command- the runnable task- Throws:
RejectedExecutionException- if this task cannot be accepted for executionNullPointerException- if command is null
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