2007-12-01 00:00:00 +00:00
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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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2010-05-25 15:58:33 -07:00
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* published by the Free Software Foundation. Oracle designates this
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2007-12-01 00:00:00 +00:00
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* particular file as subject to the "Classpath" exception as provided
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2010-05-25 15:58:33 -07:00
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* by Oracle in the LICENSE file that accompanied this code.
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2007-12-01 00:00:00 +00:00
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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2010-05-25 15:58:33 -07:00
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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2007-12-01 00:00:00 +00:00
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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2011-04-07 15:06:32 +01:00
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* http://creativecommons.org/publicdomain/zero/1.0/
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2007-12-01 00:00:00 +00:00
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*/
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package java.util.concurrent;
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import java.util.concurrent.locks.*;
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import java.util.*;
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/**
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* A bounded {@linkplain BlockingQueue blocking queue} backed by an
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* array. This queue orders elements FIFO (first-in-first-out). The
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* <em>head</em> of the queue is that element that has been on the
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* queue the longest time. The <em>tail</em> of the queue is that
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* element that has been on the queue the shortest time. New elements
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* are inserted at the tail of the queue, and the queue retrieval
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* operations obtain elements at the head of the queue.
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*
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* <p>This is a classic "bounded buffer", in which a
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* fixed-sized array holds elements inserted by producers and
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* extracted by consumers. Once created, the capacity cannot be
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2011-01-12 14:40:36 +00:00
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* changed. Attempts to {@code put} an element into a full queue
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* will result in the operation blocking; attempts to {@code take} an
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2007-12-01 00:00:00 +00:00
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* element from an empty queue will similarly block.
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*
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2011-01-12 14:40:36 +00:00
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* <p>This class supports an optional fairness policy for ordering
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2007-12-01 00:00:00 +00:00
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* waiting producer and consumer threads. By default, this ordering
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* is not guaranteed. However, a queue constructed with fairness set
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2011-01-12 14:40:36 +00:00
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* to {@code true} grants threads access in FIFO order. Fairness
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2007-12-01 00:00:00 +00:00
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* generally decreases throughput but reduces variability and avoids
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* starvation.
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*
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* <p>This class and its iterator implement all of the
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* <em>optional</em> methods of the {@link Collection} and {@link
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* Iterator} interfaces.
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*
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* <p>This class is a member of the
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* <a href="{@docRoot}/../technotes/guides/collections/index.html">
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* Java Collections Framework</a>.
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*
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* @since 1.5
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* @author Doug Lea
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* @param <E> the type of elements held in this collection
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*/
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public class ArrayBlockingQueue<E> extends AbstractQueue<E>
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implements BlockingQueue<E>, java.io.Serializable {
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/**
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* Serialization ID. This class relies on default serialization
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* even for the items array, which is default-serialized, even if
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* it is empty. Otherwise it could not be declared final, which is
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* necessary here.
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*/
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private static final long serialVersionUID = -817911632652898426L;
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2011-01-12 14:40:36 +00:00
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/** The queued items */
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final Object[] items;
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/** items index for next take, poll, peek or remove */
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int takeIndex;
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/** items index for next put, offer, or add */
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int putIndex;
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/** Number of elements in the queue */
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int count;
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2007-12-01 00:00:00 +00:00
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/*
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* Concurrency control uses the classic two-condition algorithm
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* found in any textbook.
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*/
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/** Main lock guarding all access */
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2011-01-12 14:40:36 +00:00
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final ReentrantLock lock;
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2007-12-01 00:00:00 +00:00
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/** Condition for waiting takes */
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private final Condition notEmpty;
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/** Condition for waiting puts */
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private final Condition notFull;
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// Internal helper methods
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/**
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* Circularly increment i.
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*/
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final int inc(int i) {
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2011-01-12 14:40:36 +00:00
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return (++i == items.length) ? 0 : i;
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}
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/**
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* Circularly decrement i.
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*/
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final int dec(int i) {
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return ((i == 0) ? items.length : i) - 1;
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}
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@SuppressWarnings("unchecked")
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static <E> E cast(Object item) {
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return (E) item;
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}
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/**
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* Returns item at index i.
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*/
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final E itemAt(int i) {
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return this.<E>cast(items[i]);
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}
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/**
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* Throws NullPointerException if argument is null.
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*
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* @param v the element
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*/
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private static void checkNotNull(Object v) {
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if (v == null)
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throw new NullPointerException();
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2007-12-01 00:00:00 +00:00
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}
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/**
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* Inserts element at current put position, advances, and signals.
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* Call only when holding lock.
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*/
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private void insert(E x) {
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items[putIndex] = x;
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putIndex = inc(putIndex);
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++count;
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notEmpty.signal();
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}
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/**
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* Extracts element at current take position, advances, and signals.
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* Call only when holding lock.
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*/
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private E extract() {
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2011-01-12 14:40:36 +00:00
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final Object[] items = this.items;
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E x = this.<E>cast(items[takeIndex]);
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2007-12-01 00:00:00 +00:00
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items[takeIndex] = null;
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takeIndex = inc(takeIndex);
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--count;
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notFull.signal();
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return x;
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}
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/**
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2011-01-12 14:40:36 +00:00
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* Deletes item at position i.
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* Utility for remove and iterator.remove.
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2007-12-01 00:00:00 +00:00
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* Call only when holding lock.
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*/
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void removeAt(int i) {
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2011-01-12 14:40:36 +00:00
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final Object[] items = this.items;
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2007-12-01 00:00:00 +00:00
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// if removing front item, just advance
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if (i == takeIndex) {
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items[takeIndex] = null;
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takeIndex = inc(takeIndex);
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} else {
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// slide over all others up through putIndex.
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for (;;) {
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int nexti = inc(i);
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if (nexti != putIndex) {
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items[i] = items[nexti];
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i = nexti;
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} else {
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items[i] = null;
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putIndex = i;
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break;
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}
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}
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}
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--count;
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notFull.signal();
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}
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/**
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2011-01-12 14:40:36 +00:00
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* Creates an {@code ArrayBlockingQueue} with the given (fixed)
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2007-12-01 00:00:00 +00:00
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* capacity and default access policy.
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*
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* @param capacity the capacity of this queue
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2011-01-12 14:40:36 +00:00
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* @throws IllegalArgumentException if {@code capacity < 1}
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2007-12-01 00:00:00 +00:00
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*/
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public ArrayBlockingQueue(int capacity) {
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this(capacity, false);
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}
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/**
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2011-01-12 14:40:36 +00:00
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* Creates an {@code ArrayBlockingQueue} with the given (fixed)
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2007-12-01 00:00:00 +00:00
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* capacity and the specified access policy.
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*
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* @param capacity the capacity of this queue
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2011-01-12 14:40:36 +00:00
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* @param fair if {@code true} then queue accesses for threads blocked
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2007-12-01 00:00:00 +00:00
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* on insertion or removal, are processed in FIFO order;
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2011-01-12 14:40:36 +00:00
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* if {@code false} the access order is unspecified.
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* @throws IllegalArgumentException if {@code capacity < 1}
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2007-12-01 00:00:00 +00:00
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*/
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public ArrayBlockingQueue(int capacity, boolean fair) {
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if (capacity <= 0)
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throw new IllegalArgumentException();
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2011-01-12 14:40:36 +00:00
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this.items = new Object[capacity];
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2007-12-01 00:00:00 +00:00
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lock = new ReentrantLock(fair);
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notEmpty = lock.newCondition();
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notFull = lock.newCondition();
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}
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/**
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2011-01-12 14:40:36 +00:00
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* Creates an {@code ArrayBlockingQueue} with the given (fixed)
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2007-12-01 00:00:00 +00:00
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* capacity, the specified access policy and initially containing the
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* elements of the given collection,
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* added in traversal order of the collection's iterator.
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*
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* @param capacity the capacity of this queue
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2011-01-12 14:40:36 +00:00
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* @param fair if {@code true} then queue accesses for threads blocked
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2007-12-01 00:00:00 +00:00
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* on insertion or removal, are processed in FIFO order;
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2011-01-12 14:40:36 +00:00
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* if {@code false} the access order is unspecified.
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2007-12-01 00:00:00 +00:00
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* @param c the collection of elements to initially contain
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2011-01-12 14:40:36 +00:00
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* @throws IllegalArgumentException if {@code capacity} is less than
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* {@code c.size()}, or less than 1.
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2007-12-01 00:00:00 +00:00
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* @throws NullPointerException if the specified collection or any
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* of its elements are null
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*/
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public ArrayBlockingQueue(int capacity, boolean fair,
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Collection<? extends E> c) {
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this(capacity, fair);
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2011-01-12 14:40:36 +00:00
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final ReentrantLock lock = this.lock;
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lock.lock(); // Lock only for visibility, not mutual exclusion
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try {
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int i = 0;
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try {
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for (E e : c) {
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checkNotNull(e);
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items[i++] = e;
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}
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} catch (ArrayIndexOutOfBoundsException ex) {
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throw new IllegalArgumentException();
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}
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count = i;
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putIndex = (i == capacity) ? 0 : i;
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} finally {
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lock.unlock();
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}
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2007-12-01 00:00:00 +00:00
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}
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/**
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* Inserts the specified element at the tail of this queue if it is
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* possible to do so immediately without exceeding the queue's capacity,
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2011-01-12 14:40:36 +00:00
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* returning {@code true} upon success and throwing an
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* {@code IllegalStateException} if this queue is full.
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2007-12-01 00:00:00 +00:00
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*
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* @param e the element to add
|
2011-01-12 14:40:36 +00:00
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* @return {@code true} (as specified by {@link Collection#add})
|
2007-12-01 00:00:00 +00:00
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* @throws IllegalStateException if this queue is full
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* @throws NullPointerException if the specified element is null
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*/
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public boolean add(E e) {
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return super.add(e);
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}
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/**
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* Inserts the specified element at the tail of this queue if it is
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* possible to do so immediately without exceeding the queue's capacity,
|
2011-01-12 14:40:36 +00:00
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* returning {@code true} upon success and {@code false} if this queue
|
2007-12-01 00:00:00 +00:00
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* is full. This method is generally preferable to method {@link #add},
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* which can fail to insert an element only by throwing an exception.
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*
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* @throws NullPointerException if the specified element is null
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*/
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public boolean offer(E e) {
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2011-01-12 14:40:36 +00:00
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checkNotNull(e);
|
2007-12-01 00:00:00 +00:00
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final ReentrantLock lock = this.lock;
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lock.lock();
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try {
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if (count == items.length)
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return false;
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else {
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insert(e);
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return true;
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}
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|
} finally {
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lock.unlock();
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}
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}
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|
|
/**
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|
* Inserts the specified element at the tail of this queue, waiting
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* for space to become available if the queue is full.
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|
*
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|
* @throws InterruptedException {@inheritDoc}
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|
* @throws NullPointerException {@inheritDoc}
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|
*/
|
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|
public void put(E e) throws InterruptedException {
|
2011-01-12 14:40:36 +00:00
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checkNotNull(e);
|
2007-12-01 00:00:00 +00:00
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final ReentrantLock lock = this.lock;
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lock.lockInterruptibly();
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|
try {
|
2011-01-12 14:40:36 +00:00
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while (count == items.length)
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|
notFull.await();
|
2007-12-01 00:00:00 +00:00
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|
insert(e);
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|
} finally {
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|
lock.unlock();
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|
}
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|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* Inserts the specified element at the tail of this queue, waiting
|
|
|
|
* up to the specified wait time for space to become available if
|
|
|
|
* the queue is full.
|
|
|
|
*
|
|
|
|
* @throws InterruptedException {@inheritDoc}
|
|
|
|
* @throws NullPointerException {@inheritDoc}
|
|
|
|
*/
|
|
|
|
public boolean offer(E e, long timeout, TimeUnit unit)
|
|
|
|
throws InterruptedException {
|
|
|
|
|
2011-01-12 14:40:36 +00:00
|
|
|
checkNotNull(e);
|
2007-12-01 00:00:00 +00:00
|
|
|
long nanos = unit.toNanos(timeout);
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lockInterruptibly();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
while (count == items.length) {
|
2007-12-01 00:00:00 +00:00
|
|
|
if (nanos <= 0)
|
|
|
|
return false;
|
2011-01-12 14:40:36 +00:00
|
|
|
nanos = notFull.awaitNanos(nanos);
|
2007-12-01 00:00:00 +00:00
|
|
|
}
|
2011-01-12 14:40:36 +00:00
|
|
|
insert(e);
|
|
|
|
return true;
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
public E poll() {
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
return (count == 0) ? null : extract();
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
public E take() throws InterruptedException {
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lockInterruptibly();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
while (count == 0)
|
|
|
|
notEmpty.await();
|
|
|
|
return extract();
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
|
|
|
|
long nanos = unit.toNanos(timeout);
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lockInterruptibly();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
while (count == 0) {
|
2007-12-01 00:00:00 +00:00
|
|
|
if (nanos <= 0)
|
|
|
|
return null;
|
2011-01-12 14:40:36 +00:00
|
|
|
nanos = notEmpty.awaitNanos(nanos);
|
2007-12-01 00:00:00 +00:00
|
|
|
}
|
2011-01-12 14:40:36 +00:00
|
|
|
return extract();
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
public E peek() {
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
return (count == 0) ? null : itemAt(takeIndex);
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// this doc comment is overridden to remove the reference to collections
|
|
|
|
// greater in size than Integer.MAX_VALUE
|
|
|
|
/**
|
|
|
|
* Returns the number of elements in this queue.
|
|
|
|
*
|
|
|
|
* @return the number of elements in this queue
|
|
|
|
*/
|
|
|
|
public int size() {
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
|
|
|
return count;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// this doc comment is a modified copy of the inherited doc comment,
|
|
|
|
// without the reference to unlimited queues.
|
|
|
|
/**
|
|
|
|
* Returns the number of additional elements that this queue can ideally
|
|
|
|
* (in the absence of memory or resource constraints) accept without
|
|
|
|
* blocking. This is always equal to the initial capacity of this queue
|
2011-01-12 14:40:36 +00:00
|
|
|
* less the current {@code size} of this queue.
|
2007-12-01 00:00:00 +00:00
|
|
|
*
|
|
|
|
* <p>Note that you <em>cannot</em> always tell if an attempt to insert
|
2011-01-12 14:40:36 +00:00
|
|
|
* an element will succeed by inspecting {@code remainingCapacity}
|
2007-12-01 00:00:00 +00:00
|
|
|
* because it may be the case that another thread is about to
|
|
|
|
* insert or remove an element.
|
|
|
|
*/
|
|
|
|
public int remainingCapacity() {
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
|
|
|
return items.length - count;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* Removes a single instance of the specified element from this queue,
|
2011-01-12 14:40:36 +00:00
|
|
|
* if it is present. More formally, removes an element {@code e} such
|
|
|
|
* that {@code o.equals(e)}, if this queue contains one or more such
|
2007-12-01 00:00:00 +00:00
|
|
|
* elements.
|
2011-01-12 14:40:36 +00:00
|
|
|
* Returns {@code true} if this queue contained the specified element
|
2007-12-01 00:00:00 +00:00
|
|
|
* (or equivalently, if this queue changed as a result of the call).
|
|
|
|
*
|
2011-01-12 14:40:36 +00:00
|
|
|
* <p>Removal of interior elements in circular array based queues
|
|
|
|
* is an intrinsically slow and disruptive operation, so should
|
|
|
|
* be undertaken only in exceptional circumstances, ideally
|
|
|
|
* only when the queue is known not to be accessible by other
|
|
|
|
* threads.
|
|
|
|
*
|
2007-12-01 00:00:00 +00:00
|
|
|
* @param o element to be removed from this queue, if present
|
2011-01-12 14:40:36 +00:00
|
|
|
* @return {@code true} if this queue changed as a result of the call
|
2007-12-01 00:00:00 +00:00
|
|
|
*/
|
|
|
|
public boolean remove(Object o) {
|
|
|
|
if (o == null) return false;
|
2011-01-12 14:40:36 +00:00
|
|
|
final Object[] items = this.items;
|
2007-12-01 00:00:00 +00:00
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
for (int i = takeIndex, k = count; k > 0; i = inc(i), k--) {
|
2007-12-01 00:00:00 +00:00
|
|
|
if (o.equals(items[i])) {
|
|
|
|
removeAt(i);
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
}
|
2011-01-12 14:40:36 +00:00
|
|
|
return false;
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
2011-01-12 14:40:36 +00:00
|
|
|
* Returns {@code true} if this queue contains the specified element.
|
|
|
|
* More formally, returns {@code true} if and only if this queue contains
|
|
|
|
* at least one element {@code e} such that {@code o.equals(e)}.
|
2007-12-01 00:00:00 +00:00
|
|
|
*
|
|
|
|
* @param o object to be checked for containment in this queue
|
2011-01-12 14:40:36 +00:00
|
|
|
* @return {@code true} if this queue contains the specified element
|
2007-12-01 00:00:00 +00:00
|
|
|
*/
|
|
|
|
public boolean contains(Object o) {
|
|
|
|
if (o == null) return false;
|
2011-01-12 14:40:36 +00:00
|
|
|
final Object[] items = this.items;
|
2007-12-01 00:00:00 +00:00
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
for (int i = takeIndex, k = count; k > 0; i = inc(i), k--)
|
2007-12-01 00:00:00 +00:00
|
|
|
if (o.equals(items[i]))
|
|
|
|
return true;
|
|
|
|
return false;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* Returns an array containing all of the elements in this queue, in
|
|
|
|
* proper sequence.
|
|
|
|
*
|
|
|
|
* <p>The returned array will be "safe" in that no references to it are
|
|
|
|
* maintained by this queue. (In other words, this method must allocate
|
|
|
|
* a new array). The caller is thus free to modify the returned array.
|
|
|
|
*
|
|
|
|
* <p>This method acts as bridge between array-based and collection-based
|
|
|
|
* APIs.
|
|
|
|
*
|
|
|
|
* @return an array containing all of the elements in this queue
|
|
|
|
*/
|
|
|
|
public Object[] toArray() {
|
2011-01-12 14:40:36 +00:00
|
|
|
final Object[] items = this.items;
|
2007-12-01 00:00:00 +00:00
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
final int count = this.count;
|
2007-12-01 00:00:00 +00:00
|
|
|
Object[] a = new Object[count];
|
2011-01-12 14:40:36 +00:00
|
|
|
for (int i = takeIndex, k = 0; k < count; i = inc(i), k++)
|
|
|
|
a[k] = items[i];
|
2007-12-01 00:00:00 +00:00
|
|
|
return a;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* Returns an array containing all of the elements in this queue, in
|
|
|
|
* proper sequence; the runtime type of the returned array is that of
|
|
|
|
* the specified array. If the queue fits in the specified array, it
|
|
|
|
* is returned therein. Otherwise, a new array is allocated with the
|
|
|
|
* runtime type of the specified array and the size of this queue.
|
|
|
|
*
|
|
|
|
* <p>If this queue fits in the specified array with room to spare
|
|
|
|
* (i.e., the array has more elements than this queue), the element in
|
|
|
|
* the array immediately following the end of the queue is set to
|
2011-01-12 14:40:36 +00:00
|
|
|
* {@code null}.
|
2007-12-01 00:00:00 +00:00
|
|
|
*
|
|
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between
|
|
|
|
* array-based and collection-based APIs. Further, this method allows
|
|
|
|
* precise control over the runtime type of the output array, and may,
|
|
|
|
* under certain circumstances, be used to save allocation costs.
|
|
|
|
*
|
2011-01-12 14:40:36 +00:00
|
|
|
* <p>Suppose {@code x} is a queue known to contain only strings.
|
2007-12-01 00:00:00 +00:00
|
|
|
* The following code can be used to dump the queue into a newly
|
2011-01-12 14:40:36 +00:00
|
|
|
* allocated array of {@code String}:
|
2007-12-01 00:00:00 +00:00
|
|
|
*
|
|
|
|
* <pre>
|
|
|
|
* String[] y = x.toArray(new String[0]);</pre>
|
|
|
|
*
|
2011-01-12 14:40:36 +00:00
|
|
|
* Note that {@code toArray(new Object[0])} is identical in function to
|
|
|
|
* {@code toArray()}.
|
2007-12-01 00:00:00 +00:00
|
|
|
*
|
|
|
|
* @param a the array into which the elements of the queue are to
|
|
|
|
* be stored, if it is big enough; otherwise, a new array of the
|
|
|
|
* same runtime type is allocated for this purpose
|
|
|
|
* @return an array containing all of the elements in this queue
|
|
|
|
* @throws ArrayStoreException if the runtime type of the specified array
|
|
|
|
* is not a supertype of the runtime type of every element in
|
|
|
|
* this queue
|
|
|
|
* @throws NullPointerException if the specified array is null
|
|
|
|
*/
|
2011-01-12 14:40:36 +00:00
|
|
|
@SuppressWarnings("unchecked")
|
2007-12-01 00:00:00 +00:00
|
|
|
public <T> T[] toArray(T[] a) {
|
2011-01-12 14:40:36 +00:00
|
|
|
final Object[] items = this.items;
|
2007-12-01 00:00:00 +00:00
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
final int count = this.count;
|
|
|
|
final int len = a.length;
|
|
|
|
if (len < count)
|
2007-12-01 00:00:00 +00:00
|
|
|
a = (T[])java.lang.reflect.Array.newInstance(
|
2011-01-12 14:40:36 +00:00
|
|
|
a.getClass().getComponentType(), count);
|
|
|
|
for (int i = takeIndex, k = 0; k < count; i = inc(i), k++)
|
|
|
|
a[k] = (T) items[i];
|
|
|
|
if (len > count)
|
2007-12-01 00:00:00 +00:00
|
|
|
a[count] = null;
|
|
|
|
return a;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
public String toString() {
|
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
int k = count;
|
|
|
|
if (k == 0)
|
|
|
|
return "[]";
|
|
|
|
|
|
|
|
StringBuilder sb = new StringBuilder();
|
|
|
|
sb.append('[');
|
|
|
|
for (int i = takeIndex; ; i = inc(i)) {
|
|
|
|
Object e = items[i];
|
|
|
|
sb.append(e == this ? "(this Collection)" : e);
|
|
|
|
if (--k == 0)
|
|
|
|
return sb.append(']').toString();
|
|
|
|
sb.append(',').append(' ');
|
|
|
|
}
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* Atomically removes all of the elements from this queue.
|
|
|
|
* The queue will be empty after this call returns.
|
|
|
|
*/
|
|
|
|
public void clear() {
|
2011-01-12 14:40:36 +00:00
|
|
|
final Object[] items = this.items;
|
2007-12-01 00:00:00 +00:00
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
for (int i = takeIndex, k = count; k > 0; i = inc(i), k--)
|
2007-12-01 00:00:00 +00:00
|
|
|
items[i] = null;
|
|
|
|
count = 0;
|
|
|
|
putIndex = 0;
|
|
|
|
takeIndex = 0;
|
|
|
|
notFull.signalAll();
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* @throws UnsupportedOperationException {@inheritDoc}
|
|
|
|
* @throws ClassCastException {@inheritDoc}
|
|
|
|
* @throws NullPointerException {@inheritDoc}
|
|
|
|
* @throws IllegalArgumentException {@inheritDoc}
|
|
|
|
*/
|
|
|
|
public int drainTo(Collection<? super E> c) {
|
2011-01-12 14:40:36 +00:00
|
|
|
checkNotNull(c);
|
2007-12-01 00:00:00 +00:00
|
|
|
if (c == this)
|
|
|
|
throw new IllegalArgumentException();
|
2011-01-12 14:40:36 +00:00
|
|
|
final Object[] items = this.items;
|
2007-12-01 00:00:00 +00:00
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
|
|
|
int i = takeIndex;
|
|
|
|
int n = 0;
|
|
|
|
int max = count;
|
|
|
|
while (n < max) {
|
2011-01-12 14:40:36 +00:00
|
|
|
c.add(this.<E>cast(items[i]));
|
2007-12-01 00:00:00 +00:00
|
|
|
items[i] = null;
|
|
|
|
i = inc(i);
|
|
|
|
++n;
|
|
|
|
}
|
|
|
|
if (n > 0) {
|
|
|
|
count = 0;
|
|
|
|
putIndex = 0;
|
|
|
|
takeIndex = 0;
|
|
|
|
notFull.signalAll();
|
|
|
|
}
|
|
|
|
return n;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* @throws UnsupportedOperationException {@inheritDoc}
|
|
|
|
* @throws ClassCastException {@inheritDoc}
|
|
|
|
* @throws NullPointerException {@inheritDoc}
|
|
|
|
* @throws IllegalArgumentException {@inheritDoc}
|
|
|
|
*/
|
|
|
|
public int drainTo(Collection<? super E> c, int maxElements) {
|
2011-01-12 14:40:36 +00:00
|
|
|
checkNotNull(c);
|
2007-12-01 00:00:00 +00:00
|
|
|
if (c == this)
|
|
|
|
throw new IllegalArgumentException();
|
|
|
|
if (maxElements <= 0)
|
|
|
|
return 0;
|
2011-01-12 14:40:36 +00:00
|
|
|
final Object[] items = this.items;
|
2007-12-01 00:00:00 +00:00
|
|
|
final ReentrantLock lock = this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
|
|
|
int i = takeIndex;
|
|
|
|
int n = 0;
|
2011-01-12 14:40:36 +00:00
|
|
|
int max = (maxElements < count) ? maxElements : count;
|
2007-12-01 00:00:00 +00:00
|
|
|
while (n < max) {
|
2011-01-12 14:40:36 +00:00
|
|
|
c.add(this.<E>cast(items[i]));
|
2007-12-01 00:00:00 +00:00
|
|
|
items[i] = null;
|
|
|
|
i = inc(i);
|
|
|
|
++n;
|
|
|
|
}
|
|
|
|
if (n > 0) {
|
|
|
|
count -= n;
|
|
|
|
takeIndex = i;
|
|
|
|
notFull.signalAll();
|
|
|
|
}
|
|
|
|
return n;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* Returns an iterator over the elements in this queue in proper sequence.
|
2011-01-12 14:40:36 +00:00
|
|
|
* The elements will be returned in order from first (head) to last (tail).
|
|
|
|
*
|
|
|
|
* <p>The returned {@code Iterator} is a "weakly consistent" iterator that
|
|
|
|
* will never throw {@link java.util.ConcurrentModificationException
|
|
|
|
* ConcurrentModificationException},
|
2007-12-01 00:00:00 +00:00
|
|
|
* and guarantees to traverse elements as they existed upon
|
|
|
|
* construction of the iterator, and may (but is not guaranteed to)
|
|
|
|
* reflect any modifications subsequent to construction.
|
|
|
|
*
|
|
|
|
* @return an iterator over the elements in this queue in proper sequence
|
|
|
|
*/
|
|
|
|
public Iterator<E> iterator() {
|
2011-01-12 14:40:36 +00:00
|
|
|
return new Itr();
|
2007-12-01 00:00:00 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
2011-01-12 14:40:36 +00:00
|
|
|
* Iterator for ArrayBlockingQueue. To maintain weak consistency
|
|
|
|
* with respect to puts and takes, we (1) read ahead one slot, so
|
|
|
|
* as to not report hasNext true but then not have an element to
|
|
|
|
* return -- however we later recheck this slot to use the most
|
|
|
|
* current value; (2) ensure that each array slot is traversed at
|
|
|
|
* most once (by tracking "remaining" elements); (3) skip over
|
|
|
|
* null slots, which can occur if takes race ahead of iterators.
|
|
|
|
* However, for circular array-based queues, we cannot rely on any
|
|
|
|
* well established definition of what it means to be weakly
|
|
|
|
* consistent with respect to interior removes since these may
|
|
|
|
* require slot overwrites in the process of sliding elements to
|
|
|
|
* cover gaps. So we settle for resiliency, operating on
|
|
|
|
* established apparent nexts, which may miss some elements that
|
|
|
|
* have moved between calls to next.
|
2007-12-01 00:00:00 +00:00
|
|
|
*/
|
|
|
|
private class Itr implements Iterator<E> {
|
2011-01-12 14:40:36 +00:00
|
|
|
private int remaining; // Number of elements yet to be returned
|
|
|
|
private int nextIndex; // Index of element to be returned by next
|
|
|
|
private E nextItem; // Element to be returned by next call to next
|
|
|
|
private E lastItem; // Element returned by last call to next
|
|
|
|
private int lastRet; // Index of last element returned, or -1 if none
|
2007-12-01 00:00:00 +00:00
|
|
|
|
|
|
|
Itr() {
|
2011-01-12 14:40:36 +00:00
|
|
|
final ReentrantLock lock = ArrayBlockingQueue.this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
|
|
|
lastRet = -1;
|
|
|
|
if ((remaining = count) > 0)
|
|
|
|
nextItem = itemAt(nextIndex = takeIndex);
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
2007-12-01 00:00:00 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
public boolean hasNext() {
|
2011-01-12 14:40:36 +00:00
|
|
|
return remaining > 0;
|
2007-12-01 00:00:00 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
public E next() {
|
|
|
|
final ReentrantLock lock = ArrayBlockingQueue.this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
2011-01-12 14:40:36 +00:00
|
|
|
if (remaining <= 0)
|
2007-12-01 00:00:00 +00:00
|
|
|
throw new NoSuchElementException();
|
|
|
|
lastRet = nextIndex;
|
2011-01-12 14:40:36 +00:00
|
|
|
E x = itemAt(nextIndex); // check for fresher value
|
|
|
|
if (x == null) {
|
|
|
|
x = nextItem; // we are forced to report old value
|
|
|
|
lastItem = null; // but ensure remove fails
|
|
|
|
}
|
|
|
|
else
|
|
|
|
lastItem = x;
|
|
|
|
while (--remaining > 0 && // skip over nulls
|
|
|
|
(nextItem = itemAt(nextIndex = inc(nextIndex))) == null)
|
|
|
|
;
|
2007-12-01 00:00:00 +00:00
|
|
|
return x;
|
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
public void remove() {
|
|
|
|
final ReentrantLock lock = ArrayBlockingQueue.this.lock;
|
|
|
|
lock.lock();
|
|
|
|
try {
|
|
|
|
int i = lastRet;
|
|
|
|
if (i == -1)
|
|
|
|
throw new IllegalStateException();
|
|
|
|
lastRet = -1;
|
2011-01-12 14:40:36 +00:00
|
|
|
E x = lastItem;
|
|
|
|
lastItem = null;
|
|
|
|
// only remove if item still at index
|
|
|
|
if (x != null && x == items[i]) {
|
|
|
|
boolean removingHead = (i == takeIndex);
|
|
|
|
removeAt(i);
|
|
|
|
if (!removingHead)
|
|
|
|
nextIndex = dec(nextIndex);
|
|
|
|
}
|
2007-12-01 00:00:00 +00:00
|
|
|
} finally {
|
|
|
|
lock.unlock();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
2011-01-12 14:40:36 +00:00
|
|
|
|
2007-12-01 00:00:00 +00:00
|
|
|
}
|