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.
Method Summary | |
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void |
execute(Runnable command)
Executes the given command at some time in the future. |
Method Detail |
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void execute(Runnable command)
command
- the runnable task
RejectedExecutionException
- if this task cannot be
accepted for execution.
NullPointerException
- if command is null