/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* 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 static java.util.concurrent.TimeUnit.NANOSECONDS;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
/**
* Provides default implementations of {@link ExecutorService}
* execution methods. This class implements the {@code submit},
* {@code invokeAny} and {@code invokeAll} methods using a
* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
* to the {@link FutureTask} class provided in this package. For example,
* the implementation of {@code submit(Runnable)} creates an
* associated {@code RunnableFuture} that is executed and
* returned. Subclasses may override the {@code newTaskFor} methods
* to return {@code RunnableFuture} implementations other than
* {@code FutureTask}.
*
* <p><b>Extension example</b>. Here is a sketch of a class
* that customizes {@link ThreadPoolExecutor} to use
* a {@code CustomTask} class instead of the default {@code FutureTask}:
* <pre> {@code
* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
*
* static class CustomTask<V> implements RunnableFuture<V> {...}
*
* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
* return new CustomTask<V>(c);
* }
* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
* return new CustomTask<V>(r, v);
* }
* // ... add constructors, etc.
* }}</pre>
*
* @since 1.5
* @author Doug Lea
*/
public abstract class AbstractExecutorService implements ExecutorService {
/**
* Returns a {@code RunnableFuture} for the given runnable and default
* value.
*
* @param runnable the runnable task being wrapped
* @param value the default value for the returned future
* @param <T> the type of the given value
* @return a {@code RunnableFuture} which, when run, will run the
* underlying runnable and which, as a {@code Future}, will yield
* the given value as its result and provide for cancellation of
* the underlying task
* @since 1.6
*/
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
return new FutureTask<T>(runnable, value);
}
/**
* Returns a {@code RunnableFuture} for the given callable task.
*
* @param callable the callable task being wrapped
* @param <T> the type of the callable's result
* @return a {@code RunnableFuture} which, when run, will call the
* underlying callable and which, as a {@code Future}, will yield
* the callable's result as its result and provide for
* cancellation of the underlying task
* @since 1.6
*/
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
return new FutureTask<T>(callable);
}
/**
* @throws RejectedExecutionException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public Future<?> submit(Runnable task) {
if (task == null) throw new NullPointerException();
RunnableFuture<Void> ftask = newTaskFor(task, null);
execute(ftask);
return ftask;
}
/**
* @throws RejectedExecutionException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public <T> Future<T> submit(Runnable task, T result) {
if (task == null) throw new NullPointerException();
RunnableFuture<T> ftask = newTaskFor(task, result);
execute(ftask);
return ftask;
}
/**
* @throws RejectedExecutionException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
*/
public <T> Future<T> submit(Callable<T> task) {
if (task == null) throw new NullPointerException();
RunnableFuture<T> ftask = newTaskFor(task);
execute(ftask);
return ftask;
}
/**
* the main mechanics of invokeAny.
*/
private <T> T doInvokeAny(Collection<? extends Callable<T>> 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();
ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
ExecutorCompletionService<T> ecs =
new ExecutorCompletionService<T>(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;
final long deadline = timed ? System.nanoTime() + nanos : 0L;
Iterator<? extends Callable<T>> it = tasks.iterator();
// Start one task for sure; the rest incrementally
futures.add(ecs.submit(it.next()));
--ntasks;
int active = 1;
for (;;) {
Future<T> 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, NANOSECONDS);
if (f == null)
throw new TimeoutException();
nanos = deadline - System.nanoTime();
}
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 {
cancelAll(futures);
}
}
public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
throws InterruptedException, ExecutionException {
try {
return doInvokeAny(tasks, false, 0);
} catch (TimeoutException cannotHappen) {
assert false;
return null;
}
}
public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
return doInvokeAny(tasks, true, unit.toNanos(timeout));
}
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
throws InterruptedException {
if (tasks == null)
throw new NullPointerException();
ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
try {
for (Callable<T> t : tasks) {
RunnableFuture<T> f = newTaskFor(t);
futures.add(f);
execute(f);
}
for (int i = 0, size = futures.size(); i < size; i++) {
Future<T> f = futures.get(i);
if (!f.isDone()) {
try { f.get(); }
catch (CancellationException ignore) {}
catch (ExecutionException ignore) {}
}
}
return futures;
} catch (Throwable t) {
cancelAll(futures);
throw t;
}
}
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
long timeout, TimeUnit unit)
throws InterruptedException {
if (tasks == null)
throw new NullPointerException();
final long nanos = unit.toNanos(timeout);
final long deadline = System.nanoTime() + nanos;
ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
int j = 0;
timedOut: try {
for (Callable<T> t : tasks)
futures.add(newTaskFor(t));
final int size = futures.size();
// Interleave time checks and calls to execute in case
// executor doesn't have any/much parallelism.
for (int i = 0; i < size; i++) {
if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
break timedOut;
execute((Runnable)futures.get(i));
}
for (; j < size; j++) {
Future<T> f = futures.get(j);
if (!f.isDone()) {
try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
catch (CancellationException ignore) {}
catch (ExecutionException ignore) {}
catch (TimeoutException timedOut) {
break timedOut;
}
}
}
return futures;
} catch (Throwable t) {
cancelAll(futures);
throw t;
}
// Timed out before all the tasks could be completed; cancel remaining
cancelAll(futures, j);
return futures;
}
private static <T> void cancelAll(ArrayList<Future<T>> futures) {
cancelAll(futures, 0);
}
/** Cancels all futures with index at least j. */
private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
for (int size = futures.size(); j < size; j++)
futures.get(j).cancel(true);
}
}