1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/java/util/Queue.java Tue Feb 26 16:54:16 2013 +0100
1.3 @@ -0,0 +1,218 @@
1.4 +/*
1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.6 + *
1.7 + * This code is free software; you can redistribute it and/or modify it
1.8 + * under the terms of the GNU General Public License version 2 only, as
1.9 + * published by the Free Software Foundation. Oracle designates this
1.10 + * particular file as subject to the "Classpath" exception as provided
1.11 + * by Oracle in the LICENSE file that accompanied this code.
1.12 + *
1.13 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.14 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.15 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.16 + * version 2 for more details (a copy is included in the LICENSE file that
1.17 + * accompanied this code).
1.18 + *
1.19 + * You should have received a copy of the GNU General Public License version
1.20 + * 2 along with this work; if not, write to the Free Software Foundation,
1.21 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.22 + *
1.23 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.24 + * or visit www.oracle.com if you need additional information or have any
1.25 + * questions.
1.26 + */
1.27 +
1.28 +/*
1.29 + * This file is available under and governed by the GNU General Public
1.30 + * License version 2 only, as published by the Free Software Foundation.
1.31 + * However, the following notice accompanied the original version of this
1.32 + * file:
1.33 + *
1.34 + * Written by Doug Lea with assistance from members of JCP JSR-166
1.35 + * Expert Group and released to the public domain, as explained at
1.36 + * http://creativecommons.org/publicdomain/zero/1.0/
1.37 + */
1.38 +
1.39 +package java.util;
1.40 +
1.41 +/**
1.42 + * A collection designed for holding elements prior to processing.
1.43 + * Besides basic {@link java.util.Collection Collection} operations,
1.44 + * queues provide additional insertion, extraction, and inspection
1.45 + * operations. Each of these methods exists in two forms: one throws
1.46 + * an exception if the operation fails, the other returns a special
1.47 + * value (either <tt>null</tt> or <tt>false</tt>, depending on the
1.48 + * operation). The latter form of the insert operation is designed
1.49 + * specifically for use with capacity-restricted <tt>Queue</tt>
1.50 + * implementations; in most implementations, insert operations cannot
1.51 + * fail.
1.52 + *
1.53 + * <p>
1.54 + * <table BORDER CELLPADDING=3 CELLSPACING=1>
1.55 + * <tr>
1.56 + * <td></td>
1.57 + * <td ALIGN=CENTER><em>Throws exception</em></td>
1.58 + * <td ALIGN=CENTER><em>Returns special value</em></td>
1.59 + * </tr>
1.60 + * <tr>
1.61 + * <td><b>Insert</b></td>
1.62 + * <td>{@link #add add(e)}</td>
1.63 + * <td>{@link #offer offer(e)}</td>
1.64 + * </tr>
1.65 + * <tr>
1.66 + * <td><b>Remove</b></td>
1.67 + * <td>{@link #remove remove()}</td>
1.68 + * <td>{@link #poll poll()}</td>
1.69 + * </tr>
1.70 + * <tr>
1.71 + * <td><b>Examine</b></td>
1.72 + * <td>{@link #element element()}</td>
1.73 + * <td>{@link #peek peek()}</td>
1.74 + * </tr>
1.75 + * </table>
1.76 + *
1.77 + * <p>Queues typically, but do not necessarily, order elements in a
1.78 + * FIFO (first-in-first-out) manner. Among the exceptions are
1.79 + * priority queues, which order elements according to a supplied
1.80 + * comparator, or the elements' natural ordering, and LIFO queues (or
1.81 + * stacks) which order the elements LIFO (last-in-first-out).
1.82 + * Whatever the ordering used, the <em>head</em> of the queue is that
1.83 + * element which would be removed by a call to {@link #remove() } or
1.84 + * {@link #poll()}. In a FIFO queue, all new elements are inserted at
1.85 + * the <em> tail</em> of the queue. Other kinds of queues may use
1.86 + * different placement rules. Every <tt>Queue</tt> implementation
1.87 + * must specify its ordering properties.
1.88 + *
1.89 + * <p>The {@link #offer offer} method inserts an element if possible,
1.90 + * otherwise returning <tt>false</tt>. This differs from the {@link
1.91 + * java.util.Collection#add Collection.add} method, which can fail to
1.92 + * add an element only by throwing an unchecked exception. The
1.93 + * <tt>offer</tt> method is designed for use when failure is a normal,
1.94 + * rather than exceptional occurrence, for example, in fixed-capacity
1.95 + * (or "bounded") queues.
1.96 + *
1.97 + * <p>The {@link #remove()} and {@link #poll()} methods remove and
1.98 + * return the head of the queue.
1.99 + * Exactly which element is removed from the queue is a
1.100 + * function of the queue's ordering policy, which differs from
1.101 + * implementation to implementation. The <tt>remove()</tt> and
1.102 + * <tt>poll()</tt> methods differ only in their behavior when the
1.103 + * queue is empty: the <tt>remove()</tt> method throws an exception,
1.104 + * while the <tt>poll()</tt> method returns <tt>null</tt>.
1.105 + *
1.106 + * <p>The {@link #element()} and {@link #peek()} methods return, but do
1.107 + * not remove, the head of the queue.
1.108 + *
1.109 + * <p>The <tt>Queue</tt> interface does not define the <i>blocking queue
1.110 + * methods</i>, which are common in concurrent programming. These methods,
1.111 + * which wait for elements to appear or for space to become available, are
1.112 + * defined in the {@link java.util.concurrent.BlockingQueue} interface, which
1.113 + * extends this interface.
1.114 + *
1.115 + * <p><tt>Queue</tt> implementations generally do not allow insertion
1.116 + * of <tt>null</tt> elements, although some implementations, such as
1.117 + * {@link LinkedList}, do not prohibit insertion of <tt>null</tt>.
1.118 + * Even in the implementations that permit it, <tt>null</tt> should
1.119 + * not be inserted into a <tt>Queue</tt>, as <tt>null</tt> is also
1.120 + * used as a special return value by the <tt>poll</tt> method to
1.121 + * indicate that the queue contains no elements.
1.122 + *
1.123 + * <p><tt>Queue</tt> implementations generally do not define
1.124 + * element-based versions of methods <tt>equals</tt> and
1.125 + * <tt>hashCode</tt> but instead inherit the identity based versions
1.126 + * from class <tt>Object</tt>, because element-based equality is not
1.127 + * always well-defined for queues with the same elements but different
1.128 + * ordering properties.
1.129 + *
1.130 + *
1.131 + * <p>This interface is a member of the
1.132 + * <a href="{@docRoot}/../technotes/guides/collections/index.html">
1.133 + * Java Collections Framework</a>.
1.134 + *
1.135 + * @see java.util.Collection
1.136 + * @see LinkedList
1.137 + * @see PriorityQueue
1.138 + * @see java.util.concurrent.LinkedBlockingQueue
1.139 + * @see java.util.concurrent.BlockingQueue
1.140 + * @see java.util.concurrent.ArrayBlockingQueue
1.141 + * @see java.util.concurrent.LinkedBlockingQueue
1.142 + * @see java.util.concurrent.PriorityBlockingQueue
1.143 + * @since 1.5
1.144 + * @author Doug Lea
1.145 + * @param <E> the type of elements held in this collection
1.146 + */
1.147 +public interface Queue<E> extends Collection<E> {
1.148 + /**
1.149 + * Inserts the specified element into this queue if it is possible to do so
1.150 + * immediately without violating capacity restrictions, returning
1.151 + * <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt>
1.152 + * if no space is currently available.
1.153 + *
1.154 + * @param e the element to add
1.155 + * @return <tt>true</tt> (as specified by {@link Collection#add})
1.156 + * @throws IllegalStateException if the element cannot be added at this
1.157 + * time due to capacity restrictions
1.158 + * @throws ClassCastException if the class of the specified element
1.159 + * prevents it from being added to this queue
1.160 + * @throws NullPointerException if the specified element is null and
1.161 + * this queue does not permit null elements
1.162 + * @throws IllegalArgumentException if some property of this element
1.163 + * prevents it from being added to this queue
1.164 + */
1.165 + boolean add(E e);
1.166 +
1.167 + /**
1.168 + * Inserts the specified element into this queue if it is possible to do
1.169 + * so immediately without violating capacity restrictions.
1.170 + * When using a capacity-restricted queue, this method is generally
1.171 + * preferable to {@link #add}, which can fail to insert an element only
1.172 + * by throwing an exception.
1.173 + *
1.174 + * @param e the element to add
1.175 + * @return <tt>true</tt> if the element was added to this queue, else
1.176 + * <tt>false</tt>
1.177 + * @throws ClassCastException if the class of the specified element
1.178 + * prevents it from being added to this queue
1.179 + * @throws NullPointerException if the specified element is null and
1.180 + * this queue does not permit null elements
1.181 + * @throws IllegalArgumentException if some property of this element
1.182 + * prevents it from being added to this queue
1.183 + */
1.184 + boolean offer(E e);
1.185 +
1.186 + /**
1.187 + * Retrieves and removes the head of this queue. This method differs
1.188 + * from {@link #poll poll} only in that it throws an exception if this
1.189 + * queue is empty.
1.190 + *
1.191 + * @return the head of this queue
1.192 + * @throws NoSuchElementException if this queue is empty
1.193 + */
1.194 + E remove();
1.195 +
1.196 + /**
1.197 + * Retrieves and removes the head of this queue,
1.198 + * or returns <tt>null</tt> if this queue is empty.
1.199 + *
1.200 + * @return the head of this queue, or <tt>null</tt> if this queue is empty
1.201 + */
1.202 + E poll();
1.203 +
1.204 + /**
1.205 + * Retrieves, but does not remove, the head of this queue. This method
1.206 + * differs from {@link #peek peek} only in that it throws an exception
1.207 + * if this queue is empty.
1.208 + *
1.209 + * @return the head of this queue
1.210 + * @throws NoSuchElementException if this queue is empty
1.211 + */
1.212 + E element();
1.213 +
1.214 + /**
1.215 + * Retrieves, but does not remove, the head of this queue,
1.216 + * or returns <tt>null</tt> if this queue is empty.
1.217 + *
1.218 + * @return the head of this queue, or <tt>null</tt> if this queue is empty
1.219 + */
1.220 + E peek();
1.221 +}