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/* * @(#)AbstractExecutorService.java 1.5 06/01/30 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.util.concurrent; import java.util.*; /** * Provides default implementations of {@link ExecutorService} * execution methods. This class implements the <tt>submit</tt>, * <tt>invokeAny</tt> and <tt>invokeAll</tt> methods using a * {@link RunnableFuture} returned by <tt>newTaskFor</tt>, which defaults * to the {@link FutureTask} class provided in this package. For example, * the implementation of <tt>submit(Runnable)</tt> creates an * associated <tt>RunnableFuture</tt> that is executed and * returned. Subclasses may override the <tt>newTaskFor</tt> methods * to return <tt>RunnableFuture</tt> implementations other than * <tt>FutureTask</tt>. * * <p> <b>Extension example</b>. Here is a sketch of a class * that customizes {@link ThreadPoolExecutor} to use * a <tt>CustomTask</tt> class instead of the default <tt>FutureTask</tt>: * <pre> * 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 <tt>RunnableFuture</tt> 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 <tt>RunnableFuture</tt> which when run will run the * underlying runnable and which, as a <tt>Future</tt>, 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 <tt>RunnableFuture</tt> for the given callable task. * * @param callable the callable task being wrapped * @return a <tt>RunnableFuture</tt> which when run will call the * underlying callable and which, as a <tt>Future</tt>, 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); } public Future<?> submit(Runnable task) { if (task == null) throw new NullPointerException(); RunnableFuture<Object> ftask = newTaskFor(task, null); execute(ftask); return ftask; } 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; } 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(); List<Future<T>> futures= new ArrayList<Future<T>>(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; long lastTime = (timed)? System.nanoTime() : 0; 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, 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 (InterruptedException ie) { throw ie; } catch (ExecutionException eex) { ee = eex; } catch (RuntimeException rex) { ee = new ExecutionException(rex); } } } if (ee == null) ee = new ExecutionException(); throw ee; } finally { for (Future<T> f : futures) f.cancel(true); } } 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(); List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size()); boolean done = false; try { for (Callable<T> t : tasks) { RunnableFuture<T> f = newTaskFor(t); futures.add(f); execute(f); } for (Future<T> f : futures) { if (!f.isDone()) { try { f.get(); } catch (CancellationException ignore) { } catch (ExecutionException ignore) { } } } done = true; return futures; } finally { if (!done) for (Future<T> f : futures) f.cancel(true); } } public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException { if (tasks == null || unit == null) throw new NullPointerException(); long nanos = unit.toNanos(timeout); List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size()); boolean done = false; try { for (Callable<T> 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<Future<T>> 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<T> 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<T> f : futures) f.cancel(true); } } }