Executor
Stay organized with collections
Save and categorize content based on your preferences.
Known Indirect Subclasses
|
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(final Runnable r) {
tasks.add(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.
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.
Public Method Summary
abstract
void
|
execute( Runnable command)
Executes the given command at some time in the future.
|
Public Methods
public
abstract
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 the Executor
implementation.
Parameters
command |
the runnable task |
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2024-07-10 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2024-07-10 UTC."],[[["The `Executor` interface provides a way to decouple task submission from the mechanics of how each task will be run, often using thread pools instead of explicitly creating threads."],["`Executor` implementations have flexibility in how they execute tasks, including running them immediately, in a new thread, or in a pooled thread."],["`ExecutorService` extends `Executor` with more advanced features, such as managing termination and tracking task progress with `Future` objects."],["Several implementations like `ThreadPoolExecutor` and `ScheduledThreadPoolExecutor` are available in the `java.util.concurrent` package, along with factory methods in `Executors` for easier creation."],["Memory consistency is guaranteed: actions in a thread before submitting a task happen-before its execution begins."]]],[]]