java.util.concurrent.AbstractExecutorService Maven / Gradle / Ivy
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* published by the Free Software Foundation. Oracle designates this
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* accompanied this code).
*
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/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
*/
package java.util.concurrent;
import java.util.*;
/**
* Provides default implementations of {@link ExecutorService}
* execution methods. This class implements the submit,
* invokeAny and invokeAll methods using a
* {@link RunnableFuture} returned by newTaskFor, which defaults
* to the {@link FutureTask} class provided in this package. For example,
* the implementation of submit(Runnable) creates an
* associated RunnableFuture that is executed and
* returned. Subclasses may override the newTaskFor methods
* to return RunnableFuture implementations other than
* FutureTask.
*
* Extension example. Here is a sketch of a class
* that customizes {@link ThreadPoolExecutor} to use
* a CustomTask class instead of the default FutureTask:
*
{@code
* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
*
* static class CustomTask implements RunnableFuture {...}
*
* protected RunnableFuture newTaskFor(Callable c) {
* return new CustomTask(c);
* }
* protected RunnableFuture newTaskFor(Runnable r, V v) {
* return new CustomTask(r, v);
* }
* // ... add constructors, etc.
* }}
*
* @since 1.5
* @author Doug Lea
*/
public abstract class AbstractExecutorService implements ExecutorService {
/**
* Returns a RunnableFuture for the given runnable and default
* value.
*
* @param runnable the runnable task being wrapped
* @param value the default value for the returned future
* @return a RunnableFuture which when run will run the
* underlying runnable and which, as a Future, will yield
* the given value as its result and provide for cancellation of
* the underlying task.
* @since 1.6
*/
protected RunnableFuture newTaskFor(Runnable runnable, T value) {
return new FutureTask(runnable, value);
}
/**
* Returns a RunnableFuture for the given callable task.
*
* @param callable the callable task being wrapped
* @return a RunnableFuture which when run will call the
* underlying callable and which, as a Future, will yield
* the callable's result as its result and provide for
* cancellation of the underlying task.
* @since 1.6
*/
protected RunnableFuture newTaskFor(Callable callable) {
return new FutureTask(callable);
}
/**
* @throws RejectedExecutionException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public Future submit(Runnable task) {
if (task == null) throw new NullPointerException();
RunnableFuture ftask = newTaskFor(task, null);
execute(ftask);
return ftask;
}
/**
* @throws RejectedExecutionException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public Future submit(Runnable task, T result) {
if (task == null) throw new NullPointerException();
RunnableFuture ftask = newTaskFor(task, result);
execute(ftask);
return ftask;
}
/**
* @throws RejectedExecutionException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public Future submit(Callable task) {
if (task == null) throw new NullPointerException();
RunnableFuture ftask = newTaskFor(task);
execute(ftask);
return ftask;
}
/**
* the main mechanics of invokeAny.
*/
private T doInvokeAny(Collection> tasks,
boolean timed, long nanos)
throws InterruptedException, ExecutionException, TimeoutException {
if (tasks == null)
throw new NullPointerException();
int ntasks = tasks.size();
if (ntasks == 0)
throw new IllegalArgumentException();
List> futures= new ArrayList>(ntasks);
ExecutorCompletionService ecs =
new ExecutorCompletionService(this);
// For efficiency, especially in executors with limited
// parallelism, check to see if previously submitted tasks are
// done before submitting more of them. This interleaving
// plus the exception mechanics account for messiness of main
// loop.
try {
// Record exceptions so that if we fail to obtain any
// result, we can throw the last exception we got.
ExecutionException ee = null;
long lastTime = timed ? System.nanoTime() : 0;
Iterator> it = tasks.iterator();
// Start one task for sure; the rest incrementally
futures.add(ecs.submit(it.next()));
--ntasks;
int active = 1;
for (;;) {
Future f = ecs.poll();
if (f == null) {
if (ntasks > 0) {
--ntasks;
futures.add(ecs.submit(it.next()));
++active;
}
else if (active == 0)
break;
else if (timed) {
f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
if (f == null)
throw new TimeoutException();
long now = System.nanoTime();
nanos -= now - lastTime;
lastTime = now;
}
else
f = ecs.take();
}
if (f != null) {
--active;
try {
return f.get();
} catch (ExecutionException eex) {
ee = eex;
} catch (RuntimeException rex) {
ee = new ExecutionException(rex);
}
}
}
if (ee == null)
ee = new ExecutionException();
throw ee;
} finally {
for (Future f : futures)
f.cancel(true);
}
}
public T invokeAny(Collection> tasks)
throws InterruptedException, ExecutionException {
try {
return doInvokeAny(tasks, false, 0);
} catch (TimeoutException cannotHappen) {
assert false;
return null;
}
}
public T invokeAny(Collection> tasks,
long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
return doInvokeAny(tasks, true, unit.toNanos(timeout));
}
public List> invokeAll(Collection> tasks)
throws InterruptedException {
if (tasks == null)
throw new NullPointerException();
List> futures = new ArrayList>(tasks.size());
boolean done = false;
try {
for (Callable t : tasks) {
RunnableFuture f = newTaskFor(t);
futures.add(f);
execute(f);
}
for (Future f : futures) {
if (!f.isDone()) {
try {
f.get();
} catch (CancellationException ignore) {
} catch (ExecutionException ignore) {
}
}
}
done = true;
return futures;
} finally {
if (!done)
for (Future f : futures)
f.cancel(true);
}
}
public List> invokeAll(Collection> tasks,
long timeout, TimeUnit unit)
throws InterruptedException {
if (tasks == null || unit == null)
throw new NullPointerException();
long nanos = unit.toNanos(timeout);
List> futures = new ArrayList>(tasks.size());
boolean done = false;
try {
for (Callable t : tasks)
futures.add(newTaskFor(t));
long lastTime = System.nanoTime();
// Interleave time checks and calls to execute in case
// executor doesn't have any/much parallelism.
Iterator> it = futures.iterator();
while (it.hasNext()) {
execute((Runnable)(it.next()));
long now = System.nanoTime();
nanos -= now - lastTime;
lastTime = now;
if (nanos <= 0)
return futures;
}
for (Future f : futures) {
if (!f.isDone()) {
if (nanos <= 0)
return futures;
try {
f.get(nanos, TimeUnit.NANOSECONDS);
} catch (CancellationException ignore) {
} catch (ExecutionException ignore) {
} catch (TimeoutException toe) {
return futures;
}
long now = System.nanoTime();
nanos -= now - lastTime;
lastTime = now;
}
}
done = true;
return futures;
} finally {
if (!done)
for (Future f : futures)
f.cancel(true);
}
}
}