635 lines
26 KiB
Java
635 lines
26 KiB
Java
/*
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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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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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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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* 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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*/
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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 and Josh Bloch with assistance from members of
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* JCP JSR-166 Expert Group and released to the public domain, as explained
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* at http://creativecommons.org/publicdomain/zero/1.0/
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*/
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package java.util;
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// Android-changed: removed link to collections framework docs
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/**
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* A linear collection that supports element insertion and removal at
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* both ends. The name <i>deque</i> is short for "double ended queue"
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* and is usually pronounced "deck". Most {@code Deque}
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* implementations place no fixed limits on the number of elements
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* they may contain, but this interface supports capacity-restricted
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* deques as well as those with no fixed size limit.
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*
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* <p>This interface defines methods to access the elements at both
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* ends of the deque. Methods are provided to insert, remove, and
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* examine the element. Each of these methods exists in two forms:
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* one throws an exception if the operation fails, the other returns a
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* special value (either {@code null} or {@code false}, depending on
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* the operation). The latter form of the insert operation is
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* designed specifically for use with capacity-restricted
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* {@code Deque} implementations; in most implementations, insert
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* operations cannot fail.
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*
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* <p>The twelve methods described above are summarized in the
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* following table:
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*
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* <table class="striped">
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* <caption>Summary of Deque methods</caption>
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* <thead>
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* <tr>
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* <td rowspan="2"></td>
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* <th scope="col" colspan="2"> First Element (Head)</th>
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* <th scope="col" colspan="2"> Last Element (Tail)</th>
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* </tr>
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* <tr>
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* <th scope="col" style="font-weight:normal; font-style:italic">Throws exception</th>
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* <th scope="col" style="font-weight:normal; font-style:italic">Special value</th>
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* <th scope="col" style="font-weight:normal; font-style:italic">Throws exception</th>
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* <th scope="col" style="font-weight:normal; font-style:italic">Special value</th>
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* </tr>
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* </thead>
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* <tbody>
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* <tr>
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* <th scope="row">Insert</th>
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* <td>{@link #addFirst(Object) addFirst(e)}</td>
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* <td>{@link #offerFirst(Object) offerFirst(e)}</td>
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* <td>{@link #addLast(Object) addLast(e)}</td>
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* <td>{@link #offerLast(Object) offerLast(e)}</td>
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* </tr>
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* <tr>
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* <th scope="row">Remove</th>
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* <td>{@link #removeFirst() removeFirst()}</td>
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* <td>{@link #pollFirst() pollFirst()}</td>
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* <td>{@link #removeLast() removeLast()}</td>
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* <td>{@link #pollLast() pollLast()}</td>
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* </tr>
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* <tr>
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* <th scope="row">Examine</th>
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* <td>{@link #getFirst() getFirst()}</td>
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* <td>{@link #peekFirst() peekFirst()}</td>
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* <td>{@link #getLast() getLast()}</td>
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* <td>{@link #peekLast() peekLast()}</td>
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* </tr>
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* </tbody>
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* </table>
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*
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* <p>This interface extends the {@link Queue} interface. When a deque is
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* used as a queue, FIFO (First-In-First-Out) behavior results. Elements are
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* added at the end of the deque and removed from the beginning. The methods
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* inherited from the {@code Queue} interface are precisely equivalent to
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* {@code Deque} methods as indicated in the following table:
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*
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* <table class="striped">
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* <caption>Comparison of Queue and Deque methods</caption>
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* <thead>
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* <tr>
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* <th scope="col"> {@code Queue} Method</th>
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* <th scope="col"> Equivalent {@code Deque} Method</th>
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* </tr>
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* </thead>
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* <tbody>
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* <tr>
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* <th scope="row">{@link #add(Object) add(e)}</th>
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* <td>{@link #addLast(Object) addLast(e)}</td>
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* </tr>
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* <tr>
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* <th scope="row">{@link #offer(Object) offer(e)}</th>
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* <td>{@link #offerLast(Object) offerLast(e)}</td>
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* </tr>
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* <tr>
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* <th scope="row">{@link #remove() remove()}</th>
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* <td>{@link #removeFirst() removeFirst()}</td>
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* </tr>
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* <tr>
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* <th scope="row">{@link #poll() poll()}</th>
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* <td>{@link #pollFirst() pollFirst()}</td>
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* </tr>
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* <tr>
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* <th scope="row">{@link #element() element()}</th>
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* <td>{@link #getFirst() getFirst()}</td>
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* </tr>
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* <tr>
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* <th scope="row">{@link #peek() peek()}</th>
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* <td>{@link #peekFirst() peekFirst()}</td>
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* </tr>
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* </tbody>
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* </table>
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*
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* <p>Deques can also be used as LIFO (Last-In-First-Out) stacks. This
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* interface should be used in preference to the legacy {@link Stack} class.
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* When a deque is used as a stack, elements are pushed and popped from the
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* beginning of the deque. Stack methods are equivalent to {@code Deque}
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* methods as indicated in the table below:
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*
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* <table class="striped">
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* <caption>Comparison of Stack and Deque methods</caption>
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* <thead>
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* <tr>
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* <th scope="col"> Stack Method</th>
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* <th scope="col"> Equivalent {@code Deque} Method</th>
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* </tr>
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* </thead>
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* <tbody>
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* <tr>
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* <th scope="row">{@link #push(Object) push(e)}</th>
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* <td>{@link #addFirst(Object) addFirst(e)}</td>
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* </tr>
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* <tr>
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* <th scope="row">{@link #pop() pop()}</th>
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* <td>{@link #removeFirst() removeFirst()}</td>
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* </tr>
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* <tr>
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* <th scope="row">{@link #peek() peek()}</th>
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* <td>{@link #getFirst() getFirst()}</td>
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* </tr>
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* </tbody>
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* </table>
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*
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* <p>Note that the {@link #peek peek} method works equally well when
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* a deque is used as a queue or a stack; in either case, elements are
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* drawn from the beginning of the deque.
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*
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* <p>This interface provides two methods to remove interior
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* elements, {@link #removeFirstOccurrence removeFirstOccurrence} and
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* {@link #removeLastOccurrence removeLastOccurrence}.
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*
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* <p>Unlike the {@link List} interface, this interface does not
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* provide support for indexed access to elements.
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*
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* <p>While {@code Deque} implementations are not strictly required
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* to prohibit the insertion of null elements, they are strongly
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* encouraged to do so. Users of any {@code Deque} implementations
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* that do allow null elements are strongly encouraged <i>not</i> to
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* take advantage of the ability to insert nulls. This is so because
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* {@code null} is used as a special return value by various methods
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* to indicate that the deque is empty.
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*
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* <p>{@code Deque} implementations generally do not define
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* element-based versions of the {@code equals} and {@code hashCode}
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* methods, but instead inherit the identity-based versions from class
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* {@code Object}.
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*
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* @author Doug Lea
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* @author Josh Bloch
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* @since 1.6
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* @param <E> the type of elements held in this deque
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*/
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public interface Deque<E> extends Queue<E>, SequencedCollection<E> {
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// Android-changed: fix framework docs link to "Collection#optional-restrictions"
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// Several occurrences of the link have been fixed throughout.
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/**
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* Inserts the specified element at the front of this deque if it is
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* possible to do so immediately without violating capacity restrictions,
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* throwing an {@code IllegalStateException} if no space is currently
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* available. When using a capacity-restricted deque, it is generally
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* preferable to use method {@link #offerFirst}.
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*
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* @param e the element to add
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* @throws IllegalStateException if the element cannot be added at this
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* time due to capacity restrictions
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this deque
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* @throws IllegalArgumentException if some property of the specified
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* element prevents it from being added to this deque
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*/
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void addFirst(E e);
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/**
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* Inserts the specified element at the end of this deque if it is
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* possible to do so immediately without violating capacity restrictions,
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* throwing an {@code IllegalStateException} if no space is currently
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* available. When using a capacity-restricted deque, it is generally
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* preferable to use method {@link #offerLast}.
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*
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* <p>This method is equivalent to {@link #add}.
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*
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* @param e the element to add
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* @throws IllegalStateException if the element cannot be added at this
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* time due to capacity restrictions
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this deque
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* @throws IllegalArgumentException if some property of the specified
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* element prevents it from being added to this deque
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*/
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void addLast(E e);
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/**
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* Inserts the specified element at the front of this deque unless it would
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* violate capacity restrictions. When using a capacity-restricted deque,
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* this method is generally preferable to the {@link #addFirst} method,
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* which can fail to insert an element only by throwing an exception.
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*
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* @param e the element to add
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* @return {@code true} if the element was added to this deque, else
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* {@code false}
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this deque
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* @throws IllegalArgumentException if some property of the specified
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* element prevents it from being added to this deque
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*/
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boolean offerFirst(E e);
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/**
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* Inserts the specified element at the end of this deque unless it would
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* violate capacity restrictions. When using a capacity-restricted deque,
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* this method is generally preferable to the {@link #addLast} method,
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* which can fail to insert an element only by throwing an exception.
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*
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* @param e the element to add
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* @return {@code true} if the element was added to this deque, else
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* {@code false}
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this deque
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* @throws IllegalArgumentException if some property of the specified
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* element prevents it from being added to this deque
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*/
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boolean offerLast(E e);
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/**
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* Retrieves and removes the first element of this deque. This method
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* differs from {@link #pollFirst pollFirst} only in that it throws an
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* exception if this deque is empty.
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*
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* @return the head of this deque
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* @throws NoSuchElementException if this deque is empty
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*/
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E removeFirst();
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/**
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* Retrieves and removes the last element of this deque. This method
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* differs from {@link #pollLast pollLast} only in that it throws an
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* exception if this deque is empty.
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*
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* @return the tail of this deque
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* @throws NoSuchElementException if this deque is empty
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*/
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E removeLast();
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/**
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* Retrieves and removes the first element of this deque,
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* or returns {@code null} if this deque is empty.
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*
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* @return the head of this deque, or {@code null} if this deque is empty
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*/
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E pollFirst();
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/**
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* Retrieves and removes the last element of this deque,
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* or returns {@code null} if this deque is empty.
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*
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* @return the tail of this deque, or {@code null} if this deque is empty
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*/
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E pollLast();
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/**
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* Retrieves, but does not remove, the first element of this deque.
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*
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* This method differs from {@link #peekFirst peekFirst} only in that it
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* throws an exception if this deque is empty.
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*
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* @return the head of this deque
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* @throws NoSuchElementException if this deque is empty
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*/
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E getFirst();
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/**
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* Retrieves, but does not remove, the last element of this deque.
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* This method differs from {@link #peekLast peekLast} only in that it
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* throws an exception if this deque is empty.
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*
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* @return the tail of this deque
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* @throws NoSuchElementException if this deque is empty
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*/
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E getLast();
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/**
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* Retrieves, but does not remove, the first element of this deque,
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* or returns {@code null} if this deque is empty.
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*
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* @return the head of this deque, or {@code null} if this deque is empty
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*/
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E peekFirst();
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/**
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* Retrieves, but does not remove, the last element of this deque,
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* or returns {@code null} if this deque is empty.
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*
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* @return the tail of this deque, or {@code null} if this deque is empty
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*/
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E peekLast();
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/**
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* Removes the first occurrence of the specified element from this deque.
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* If the deque does not contain the element, it is unchanged.
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* More formally, removes the first element {@code e} such that
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* {@code Objects.equals(o, e)} (if such an element exists).
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* Returns {@code true} if this deque contained the specified element
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* (or equivalently, if this deque changed as a result of the call).
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*
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* @param o element to be removed from this deque, if present
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* @return {@code true} if an element was removed as a result of this call
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* @throws ClassCastException if the class of the specified element
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* is incompatible with this deque
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* ({@linkplain Collection##optional-restrictions optional})
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* ({@linkplain Collection##optional-restrictions optional})
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*/
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boolean removeFirstOccurrence(Object o);
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/**
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* Removes the last occurrence of the specified element from this deque.
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* If the deque does not contain the element, it is unchanged.
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* More formally, removes the last element {@code e} such that
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* {@code Objects.equals(o, e)} (if such an element exists).
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* Returns {@code true} if this deque contained the specified element
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* (or equivalently, if this deque changed as a result of the call).
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*
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* @param o element to be removed from this deque, if present
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* @return {@code true} if an element was removed as a result of this call
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* @throws ClassCastException if the class of the specified element
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* is incompatible with this deque
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* ({@linkplain Collection##optional-restrictions optional})
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* ({@linkplain Collection##optional-restrictions optional})
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*/
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boolean removeLastOccurrence(Object o);
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// *** Queue methods ***
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/**
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* Inserts the specified element into the queue represented by this deque
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* (in other words, at the tail of this deque) if it is possible to do so
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* immediately without violating capacity restrictions, returning
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* {@code true} upon success and throwing an
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* {@code IllegalStateException} if no space is currently available.
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* When using a capacity-restricted deque, it is generally preferable to
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* use {@link #offer(Object) offer}.
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*
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* <p>This method is equivalent to {@link #addLast}.
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*
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* @param e the element to add
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* @return {@code true} (as specified by {@link Collection#add})
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* @throws IllegalStateException if the element cannot be added at this
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* time due to capacity restrictions
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this deque
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* @throws IllegalArgumentException if some property of the specified
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* element prevents it from being added to this deque
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*/
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boolean add(E e);
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/**
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* Inserts the specified element into the queue represented by this deque
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* (in other words, at the tail of this deque) if it is possible to do so
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* immediately without violating capacity restrictions, returning
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* {@code true} upon success and {@code false} if no space is currently
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* available. When using a capacity-restricted deque, this method is
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* generally preferable to the {@link #add} method, which can fail to
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* insert an element only by throwing an exception.
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*
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* <p>This method is equivalent to {@link #offerLast}.
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*
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* @param e the element to add
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* @return {@code true} if the element was added to this deque, else
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* {@code false}
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* @throws ClassCastException if the class of the specified element
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* prevents it from being added to this deque
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* @throws NullPointerException if the specified element is null and this
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* deque does not permit null elements
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* @throws IllegalArgumentException if some property of the specified
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* element prevents it from being added to this deque
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*/
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boolean offer(E e);
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/**
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* Retrieves and removes the head of the queue represented by this deque
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* (in other words, the first element of this deque).
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* This method differs from {@link #poll() poll()} only in that it
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* throws an exception if this deque is empty.
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*
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* <p>This method is equivalent to {@link #removeFirst()}.
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*
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* @return the head of the queue represented by this deque
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* @throws NoSuchElementException if this deque is empty
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*/
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E remove();
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/**
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* Retrieves and removes the head of the queue represented by this deque
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* (in other words, the first element of this deque), or returns
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* {@code null} if this deque is empty.
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*
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* <p>This method is equivalent to {@link #pollFirst()}.
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*
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* @return the first element of this deque, or {@code null} if
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* this deque is empty
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*/
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E poll();
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/**
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* Retrieves, but does not remove, the head of the queue represented by
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* this deque (in other words, the first element of this deque).
|
|
* This method differs from {@link #peek peek} only in that it throws an
|
|
* exception if this deque is empty.
|
|
*
|
|
* <p>This method is equivalent to {@link #getFirst()}.
|
|
*
|
|
* @return the head of the queue represented by this deque
|
|
* @throws NoSuchElementException if this deque is empty
|
|
*/
|
|
E element();
|
|
|
|
/**
|
|
* Retrieves, but does not remove, the head of the queue represented by
|
|
* this deque (in other words, the first element of this deque), or
|
|
* returns {@code null} if this deque is empty.
|
|
*
|
|
* <p>This method is equivalent to {@link #peekFirst()}.
|
|
*
|
|
* @return the head of the queue represented by this deque, or
|
|
* {@code null} if this deque is empty
|
|
*/
|
|
E peek();
|
|
|
|
/**
|
|
* Adds all of the elements in the specified collection at the end
|
|
* of this deque, as if by calling {@link #addLast} on each one,
|
|
* in the order that they are returned by the collection's iterator.
|
|
*
|
|
* <p>When using a capacity-restricted deque, it is generally preferable
|
|
* to call {@link #offer(Object) offer} separately on each element.
|
|
*
|
|
* <p>An exception encountered while trying to add an element may result
|
|
* in only some of the elements having been successfully added when
|
|
* the associated exception is thrown.
|
|
*
|
|
* @param c the elements to be inserted into this deque
|
|
* @return {@code true} if this deque changed as a result of the call
|
|
* @throws IllegalStateException if not all the elements can be added at
|
|
* this time due to insertion restrictions
|
|
* @throws ClassCastException if the class of an element of the specified
|
|
* collection prevents it from being added to this deque
|
|
* @throws NullPointerException if the specified collection contains a
|
|
* null element and this deque does not permit null elements,
|
|
* or if the specified collection is null
|
|
* @throws IllegalArgumentException if some property of an element of the
|
|
* specified collection prevents it from being added to this deque
|
|
*/
|
|
boolean addAll(Collection<? extends E> c);
|
|
|
|
// *** Stack methods ***
|
|
|
|
/**
|
|
* Pushes an element onto the stack represented by this deque (in other
|
|
* words, at the head of this deque) if it is possible to do so
|
|
* immediately without violating capacity restrictions, throwing an
|
|
* {@code IllegalStateException} if no space is currently available.
|
|
*
|
|
* <p>This method is equivalent to {@link #addFirst}.
|
|
*
|
|
* @param e the element to push
|
|
* @throws IllegalStateException if the element cannot be added at this
|
|
* time due to capacity restrictions
|
|
* @throws ClassCastException if the class of the specified element
|
|
* prevents it from being added to this deque
|
|
* @throws NullPointerException if the specified element is null and this
|
|
* deque does not permit null elements
|
|
* @throws IllegalArgumentException if some property of the specified
|
|
* element prevents it from being added to this deque
|
|
*/
|
|
void push(E e);
|
|
|
|
/**
|
|
* Pops an element from the stack represented by this deque. In other
|
|
* words, removes and returns the first element of this deque.
|
|
*
|
|
* <p>This method is equivalent to {@link #removeFirst()}.
|
|
*
|
|
* @return the element at the front of this deque (which is the top
|
|
* of the stack represented by this deque)
|
|
* @throws NoSuchElementException if this deque is empty
|
|
*/
|
|
E pop();
|
|
|
|
|
|
// *** Collection methods ***
|
|
|
|
/**
|
|
* Removes the first occurrence of the specified element from this deque.
|
|
* If the deque does not contain the element, it is unchanged.
|
|
* More formally, removes the first element {@code e} such that
|
|
* {@code Objects.equals(o, e)} (if such an element exists).
|
|
* Returns {@code true} if this deque contained the specified element
|
|
* (or equivalently, if this deque changed as a result of the call).
|
|
*
|
|
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
|
|
*
|
|
* @param o element to be removed from this deque, if present
|
|
* @return {@code true} if an element was removed as a result of this call
|
|
* @throws ClassCastException if the class of the specified element
|
|
* is incompatible with this deque
|
|
* ({@linkplain Collection##optional-restrictions optional})
|
|
* @throws NullPointerException if the specified element is null and this
|
|
* deque does not permit null elements
|
|
* ({@linkplain Collection##optional-restrictions optional})
|
|
*/
|
|
boolean remove(Object o);
|
|
|
|
/**
|
|
* Returns {@code true} if this deque contains the specified element.
|
|
* More formally, returns {@code true} if and only if this deque contains
|
|
* at least one element {@code e} such that {@code Objects.equals(o, e)}.
|
|
*
|
|
* @param o element whose presence in this deque is to be tested
|
|
* @return {@code true} if this deque contains the specified element
|
|
* @throws ClassCastException if the class of the specified element
|
|
* is incompatible with this deque
|
|
* ({@linkplain Collection##optional-restrictions optional})
|
|
* @throws NullPointerException if the specified element is null and this
|
|
* deque does not permit null elements
|
|
* ({@linkplain Collection##optional-restrictions optional})
|
|
*/
|
|
boolean contains(Object o);
|
|
|
|
/**
|
|
* Returns the number of elements in this deque.
|
|
*
|
|
* @return the number of elements in this deque
|
|
*/
|
|
int size();
|
|
|
|
/**
|
|
* Returns an iterator over the elements in this deque in proper sequence.
|
|
* The elements will be returned in order from first (head) to last (tail).
|
|
*
|
|
* @return an iterator over the elements in this deque in proper sequence
|
|
*/
|
|
Iterator<E> iterator();
|
|
|
|
/**
|
|
* Returns an iterator over the elements in this deque in reverse
|
|
* sequential order. The elements will be returned in order from
|
|
* last (tail) to first (head).
|
|
*
|
|
* @return an iterator over the elements in this deque in reverse
|
|
* sequence
|
|
*/
|
|
Iterator<E> descendingIterator();
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
*
|
|
* @implSpec
|
|
* The implementation in this interface returns a reverse-ordered Deque
|
|
* view. The {@code reversed()} method of the view returns a reference
|
|
* to this Deque. Other operations on the view are implemented via calls to
|
|
* public methods on this Deque. The exact relationship between calls on the
|
|
* view and calls on this Deque is unspecified. However, order-sensitive
|
|
* operations generally delegate to the appropriate method with the opposite
|
|
* orientation. For example, calling {@code getFirst} on the view results in
|
|
* a call to {@code getLast} on this Deque.
|
|
*
|
|
* @return a reverse-ordered view of this collection, as a {@code Deque}
|
|
* @since 21
|
|
*/
|
|
default Deque<E> reversed() {
|
|
return ReverseOrderDequeView.of(this);
|
|
}
|
|
}
|