author | naoto |
Thu, 14 Mar 2013 11:29:16 -0700 | |
changeset 16481 | 8e30386cc014 |
parent 13795 | 73850c397272 |
child 17168 | b7d3500f2516 |
permissions | -rw-r--r-- |
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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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* 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 Josh Bloch of Google Inc. and released to the public domain, |
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* as explained at http://creativecommons.org/publicdomain/zero/1.0/. |
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*/ |
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package java.util; |
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import java.io.*; |
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/** |
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* Resizable-array implementation of the {@link Deque} interface. Array |
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* deques have no capacity restrictions; they grow as necessary to support |
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* usage. They are not thread-safe; in the absence of external |
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* synchronization, they do not support concurrent access by multiple threads. |
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* Null elements are prohibited. This class is likely to be faster than |
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* {@link Stack} when used as a stack, and faster than {@link LinkedList} |
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* when used as a queue. |
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* |
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* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time. |
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* Exceptions include {@link #remove(Object) remove}, {@link |
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* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence |
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* removeLastOccurrence}, {@link #contains contains}, {@link #iterator |
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* iterator.remove()}, and the bulk operations, all of which run in linear |
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* time. |
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* |
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* <p>The iterators returned by this class's <tt>iterator</tt> method are |
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* <i>fail-fast</i>: If the deque is modified at any time after the iterator |
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* is created, in any way except through the iterator's own <tt>remove</tt> |
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* method, the iterator will generally throw a {@link |
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* ConcurrentModificationException}. Thus, in the face of concurrent |
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* modification, the iterator fails quickly and cleanly, rather than risking |
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* arbitrary, non-deterministic behavior at an undetermined time in the |
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* future. |
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* |
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
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* as it is, generally speaking, impossible to make any hard guarantees in the |
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* presence of unsynchronized concurrent modification. Fail-fast iterators |
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* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
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* Therefore, it would be wrong to write a program that depended on this |
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* exception for its correctness: <i>the fail-fast behavior of iterators |
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* should be used only to detect bugs.</i> |
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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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* @author Josh Bloch and Doug Lea |
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* @since 1.6 |
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* @param <E> the type of elements held in this collection |
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*/ |
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public class ArrayDeque<E> extends AbstractCollection<E> |
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implements Deque<E>, Cloneable, Serializable |
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{ |
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/** |
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* The array in which the elements of the deque are stored. |
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* The capacity of the deque is the length of this array, which is |
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* always a power of two. The array is never allowed to become |
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* full, except transiently within an addX method where it is |
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* resized (see doubleCapacity) immediately upon becoming full, |
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* thus avoiding head and tail wrapping around to equal each |
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* other. We also guarantee that all array cells not holding |
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* deque elements are always null. |
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*/ |
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private transient E[] elements; |
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/** |
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* The index of the element at the head of the deque (which is the |
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* element that would be removed by remove() or pop()); or an |
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* arbitrary number equal to tail if the deque is empty. |
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*/ |
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private transient int head; |
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/** |
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* The index at which the next element would be added to the tail |
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* of the deque (via addLast(E), add(E), or push(E)). |
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*/ |
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private transient int tail; |
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/** |
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* The minimum capacity that we'll use for a newly created deque. |
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* Must be a power of 2. |
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*/ |
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private static final int MIN_INITIAL_CAPACITY = 8; |
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// ****** Array allocation and resizing utilities ****** |
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/** |
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* Allocate empty array to hold the given number of elements. |
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* |
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* @param numElements the number of elements to hold |
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*/ |
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@SuppressWarnings("unchecked") |
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private void allocateElements(int numElements) { |
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int initialCapacity = MIN_INITIAL_CAPACITY; |
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// Find the best power of two to hold elements. |
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// Tests "<=" because arrays aren't kept full. |
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if (numElements >= initialCapacity) { |
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initialCapacity = numElements; |
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initialCapacity |= (initialCapacity >>> 1); |
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initialCapacity |= (initialCapacity >>> 2); |
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initialCapacity |= (initialCapacity >>> 4); |
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initialCapacity |= (initialCapacity >>> 8); |
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initialCapacity |= (initialCapacity >>> 16); |
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initialCapacity++; |
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if (initialCapacity < 0) // Too many elements, must back off |
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initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements |
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} |
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elements = (E[]) new Object[initialCapacity]; |
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} |
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/** |
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* Double the capacity of this deque. Call only when full, i.e., |
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* when head and tail have wrapped around to become equal. |
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*/ |
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private void doubleCapacity() { |
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assert head == tail; |
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int p = head; |
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int n = elements.length; |
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int r = n - p; // number of elements to the right of p |
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int newCapacity = n << 1; |
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if (newCapacity < 0) |
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throw new IllegalStateException("Sorry, deque too big"); |
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@SuppressWarnings("unchecked") |
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E[] a = (E[]) new Object[newCapacity]; |
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System.arraycopy(elements, p, a, 0, r); |
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System.arraycopy(elements, 0, a, r, p); |
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elements = a; |
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head = 0; |
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tail = n; |
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} |
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/** |
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* Copies the elements from our element array into the specified array, |
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* in order (from first to last element in the deque). It is assumed |
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* that the array is large enough to hold all elements in the deque. |
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* |
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* @return its argument |
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*/ |
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private <T> T[] copyElements(T[] a) { |
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if (head < tail) { |
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System.arraycopy(elements, head, a, 0, size()); |
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} else if (head > tail) { |
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int headPortionLen = elements.length - head; |
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System.arraycopy(elements, head, a, 0, headPortionLen); |
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System.arraycopy(elements, 0, a, headPortionLen, tail); |
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} |
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return a; |
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} |
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/** |
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* Constructs an empty array deque with an initial capacity |
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* sufficient to hold 16 elements. |
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*/ |
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@SuppressWarnings("unchecked") |
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public ArrayDeque() { |
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elements = (E[]) new Object[16]; |
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} |
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/** |
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* Constructs an empty array deque with an initial capacity |
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* sufficient to hold the specified number of elements. |
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* |
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* @param numElements lower bound on initial capacity of the deque |
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*/ |
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public ArrayDeque(int numElements) { |
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allocateElements(numElements); |
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} |
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/** |
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* Constructs a deque containing the elements of the specified |
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* collection, in the order they are returned by the collection's |
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* iterator. (The first element returned by the collection's |
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* iterator becomes the first element, or <i>front</i> of the |
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* deque.) |
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* |
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* @param c the collection whose elements are to be placed into the deque |
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* @throws NullPointerException if the specified collection is null |
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*/ |
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public ArrayDeque(Collection<? extends E> c) { |
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allocateElements(c.size()); |
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addAll(c); |
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} |
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// The main insertion and extraction methods are addFirst, |
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// addLast, pollFirst, pollLast. The other methods are defined in |
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// terms of these. |
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/** |
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* Inserts the specified element at the front of this deque. |
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* |
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* @param e the element to add |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public void addFirst(E e) { |
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if (e == null) |
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throw new NullPointerException(); |
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elements[head = (head - 1) & (elements.length - 1)] = e; |
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if (head == tail) |
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doubleCapacity(); |
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} |
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/** |
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* Inserts the specified element at the end of this deque. |
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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 NullPointerException if the specified element is null |
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*/ |
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public void addLast(E e) { |
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if (e == null) |
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throw new NullPointerException(); |
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elements[tail] = e; |
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if ( (tail = (tail + 1) & (elements.length - 1)) == head) |
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doubleCapacity(); |
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} |
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/** |
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* Inserts the specified element at the front of this deque. |
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* |
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* @param e the element to add |
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* @return <tt>true</tt> (as specified by {@link Deque#offerFirst}) |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean offerFirst(E e) { |
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addFirst(e); |
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return true; |
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} |
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/** |
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* Inserts the specified element at the end of this deque. |
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* |
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* @param e the element to add |
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* @return <tt>true</tt> (as specified by {@link Deque#offerLast}) |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public boolean offerLast(E e) { |
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addLast(e); |
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return true; |
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} |
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
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*/ |
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public E removeFirst() { |
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E x = pollFirst(); |
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if (x == null) |
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throw new NoSuchElementException(); |
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return x; |
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} |
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
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*/ |
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public E removeLast() { |
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E x = pollLast(); |
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if (x == null) |
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throw new NoSuchElementException(); |
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return x; |
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} |
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295 |
public E pollFirst() { |
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int h = head; |
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E result = elements[h]; // Element is null if deque empty |
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298 |
if (result == null) |
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return null; |
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elements[h] = null; // Must null out slot |
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head = (h + 1) & (elements.length - 1); |
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return result; |
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} |
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||
305 |
public E pollLast() { |
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int t = (tail - 1) & (elements.length - 1); |
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E result = elements[t]; |
|
308 |
if (result == null) |
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return null; |
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elements[t] = null; |
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tail = t; |
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return result; |
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} |
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314 |
||
315 |
/** |
|
316 |
* @throws NoSuchElementException {@inheritDoc} |
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317 |
*/ |
|
318 |
public E getFirst() { |
|
319 |
E x = elements[head]; |
|
320 |
if (x == null) |
|
321 |
throw new NoSuchElementException(); |
|
322 |
return x; |
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323 |
} |
|
324 |
||
325 |
/** |
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326 |
* @throws NoSuchElementException {@inheritDoc} |
|
327 |
*/ |
|
328 |
public E getLast() { |
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329 |
E x = elements[(tail - 1) & (elements.length - 1)]; |
|
330 |
if (x == null) |
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throw new NoSuchElementException(); |
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return x; |
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333 |
} |
|
334 |
||
335 |
public E peekFirst() { |
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336 |
return elements[head]; // elements[head] is null if deque empty |
|
337 |
} |
|
338 |
||
339 |
public E peekLast() { |
|
340 |
return elements[(tail - 1) & (elements.length - 1)]; |
|
341 |
} |
|
342 |
||
343 |
/** |
|
344 |
* Removes the first occurrence of the specified element in this |
|
345 |
* deque (when traversing the deque from head to tail). |
|
346 |
* If the deque does not contain the element, it is unchanged. |
|
347 |
* More formally, removes the first element <tt>e</tt> such that |
|
348 |
* <tt>o.equals(e)</tt> (if such an element exists). |
|
349 |
* Returns <tt>true</tt> if this deque contained the specified element |
|
350 |
* (or equivalently, if this deque changed as a result of the call). |
|
351 |
* |
|
352 |
* @param o element to be removed from this deque, if present |
|
353 |
* @return <tt>true</tt> if the deque contained the specified element |
|
354 |
*/ |
|
355 |
public boolean removeFirstOccurrence(Object o) { |
|
356 |
if (o == null) |
|
357 |
return false; |
|
358 |
int mask = elements.length - 1; |
|
359 |
int i = head; |
|
360 |
E x; |
|
361 |
while ( (x = elements[i]) != null) { |
|
362 |
if (o.equals(x)) { |
|
363 |
delete(i); |
|
364 |
return true; |
|
365 |
} |
|
366 |
i = (i + 1) & mask; |
|
367 |
} |
|
368 |
return false; |
|
369 |
} |
|
370 |
||
371 |
/** |
|
372 |
* Removes the last occurrence of the specified element in this |
|
373 |
* deque (when traversing the deque from head to tail). |
|
374 |
* If the deque does not contain the element, it is unchanged. |
|
375 |
* More formally, removes the last element <tt>e</tt> such that |
|
376 |
* <tt>o.equals(e)</tt> (if such an element exists). |
|
377 |
* Returns <tt>true</tt> if this deque contained the specified element |
|
378 |
* (or equivalently, if this deque changed as a result of the call). |
|
379 |
* |
|
380 |
* @param o element to be removed from this deque, if present |
|
381 |
* @return <tt>true</tt> if the deque contained the specified element |
|
382 |
*/ |
|
383 |
public boolean removeLastOccurrence(Object o) { |
|
384 |
if (o == null) |
|
385 |
return false; |
|
386 |
int mask = elements.length - 1; |
|
387 |
int i = (tail - 1) & mask; |
|
388 |
E x; |
|
389 |
while ( (x = elements[i]) != null) { |
|
390 |
if (o.equals(x)) { |
|
391 |
delete(i); |
|
392 |
return true; |
|
393 |
} |
|
394 |
i = (i - 1) & mask; |
|
395 |
} |
|
396 |
return false; |
|
397 |
} |
|
398 |
||
399 |
// *** Queue methods *** |
|
400 |
||
401 |
/** |
|
402 |
* Inserts the specified element at the end of this deque. |
|
403 |
* |
|
404 |
* <p>This method is equivalent to {@link #addLast}. |
|
405 |
* |
|
406 |
* @param e the element to add |
|
407 |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
|
408 |
* @throws NullPointerException if the specified element is null |
|
409 |
*/ |
|
410 |
public boolean add(E e) { |
|
411 |
addLast(e); |
|
412 |
return true; |
|
413 |
} |
|
414 |
||
415 |
/** |
|
416 |
* Inserts the specified element at the end of this deque. |
|
417 |
* |
|
418 |
* <p>This method is equivalent to {@link #offerLast}. |
|
419 |
* |
|
420 |
* @param e the element to add |
|
421 |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
|
422 |
* @throws NullPointerException if the specified element is null |
|
423 |
*/ |
|
424 |
public boolean offer(E e) { |
|
425 |
return offerLast(e); |
|
426 |
} |
|
427 |
||
428 |
/** |
|
429 |
* Retrieves and removes the head of the queue represented by this deque. |
|
430 |
* |
|
431 |
* This method differs from {@link #poll poll} only in that it throws an |
|
432 |
* exception if this deque is empty. |
|
433 |
* |
|
434 |
* <p>This method is equivalent to {@link #removeFirst}. |
|
435 |
* |
|
436 |
* @return the head of the queue represented by this deque |
|
437 |
* @throws NoSuchElementException {@inheritDoc} |
|
438 |
*/ |
|
439 |
public E remove() { |
|
440 |
return removeFirst(); |
|
441 |
} |
|
442 |
||
443 |
/** |
|
444 |
* Retrieves and removes the head of the queue represented by this deque |
|
445 |
* (in other words, the first element of this deque), or returns |
|
446 |
* <tt>null</tt> if this deque is empty. |
|
447 |
* |
|
448 |
* <p>This method is equivalent to {@link #pollFirst}. |
|
449 |
* |
|
450 |
* @return the head of the queue represented by this deque, or |
|
451 |
* <tt>null</tt> if this deque is empty |
|
452 |
*/ |
|
453 |
public E poll() { |
|
454 |
return pollFirst(); |
|
455 |
} |
|
456 |
||
457 |
/** |
|
458 |
* Retrieves, but does not remove, the head of the queue represented by |
|
459 |
* this deque. This method differs from {@link #peek peek} only in |
|
460 |
* that it throws an exception if this deque is empty. |
|
461 |
* |
|
462 |
* <p>This method is equivalent to {@link #getFirst}. |
|
463 |
* |
|
464 |
* @return the head of the queue represented by this deque |
|
465 |
* @throws NoSuchElementException {@inheritDoc} |
|
466 |
*/ |
|
467 |
public E element() { |
|
468 |
return getFirst(); |
|
469 |
} |
|
470 |
||
471 |
/** |
|
472 |
* Retrieves, but does not remove, the head of the queue represented by |
|
473 |
* this deque, or returns <tt>null</tt> if this deque is empty. |
|
474 |
* |
|
475 |
* <p>This method is equivalent to {@link #peekFirst}. |
|
476 |
* |
|
477 |
* @return the head of the queue represented by this deque, or |
|
478 |
* <tt>null</tt> if this deque is empty |
|
479 |
*/ |
|
480 |
public E peek() { |
|
481 |
return peekFirst(); |
|
482 |
} |
|
483 |
||
484 |
// *** Stack methods *** |
|
485 |
||
486 |
/** |
|
487 |
* Pushes an element onto the stack represented by this deque. In other |
|
488 |
* words, inserts the element at the front of this deque. |
|
489 |
* |
|
490 |
* <p>This method is equivalent to {@link #addFirst}. |
|
491 |
* |
|
492 |
* @param e the element to push |
|
493 |
* @throws NullPointerException if the specified element is null |
|
494 |
*/ |
|
495 |
public void push(E e) { |
|
496 |
addFirst(e); |
|
497 |
} |
|
498 |
||
499 |
/** |
|
500 |
* Pops an element from the stack represented by this deque. In other |
|
501 |
* words, removes and returns the first element of this deque. |
|
502 |
* |
|
503 |
* <p>This method is equivalent to {@link #removeFirst()}. |
|
504 |
* |
|
505 |
* @return the element at the front of this deque (which is the top |
|
506 |
* of the stack represented by this deque) |
|
507 |
* @throws NoSuchElementException {@inheritDoc} |
|
508 |
*/ |
|
509 |
public E pop() { |
|
510 |
return removeFirst(); |
|
511 |
} |
|
512 |
||
513 |
private void checkInvariants() { |
|
514 |
assert elements[tail] == null; |
|
515 |
assert head == tail ? elements[head] == null : |
|
516 |
(elements[head] != null && |
|
517 |
elements[(tail - 1) & (elements.length - 1)] != null); |
|
518 |
assert elements[(head - 1) & (elements.length - 1)] == null; |
|
519 |
} |
|
520 |
||
521 |
/** |
|
522 |
* Removes the element at the specified position in the elements array, |
|
523 |
* adjusting head and tail as necessary. This can result in motion of |
|
524 |
* elements backwards or forwards in the array. |
|
525 |
* |
|
526 |
* <p>This method is called delete rather than remove to emphasize |
|
527 |
* that its semantics differ from those of {@link List#remove(int)}. |
|
528 |
* |
|
529 |
* @return true if elements moved backwards |
|
530 |
*/ |
|
531 |
private boolean delete(int i) { |
|
532 |
checkInvariants(); |
|
533 |
final E[] elements = this.elements; |
|
534 |
final int mask = elements.length - 1; |
|
535 |
final int h = head; |
|
536 |
final int t = tail; |
|
537 |
final int front = (i - h) & mask; |
|
538 |
final int back = (t - i) & mask; |
|
539 |
||
540 |
// Invariant: head <= i < tail mod circularity |
|
541 |
if (front >= ((t - h) & mask)) |
|
542 |
throw new ConcurrentModificationException(); |
|
543 |
||
544 |
// Optimize for least element motion |
|
545 |
if (front < back) { |
|
546 |
if (h <= i) { |
|
547 |
System.arraycopy(elements, h, elements, h + 1, front); |
|
548 |
} else { // Wrap around |
|
549 |
System.arraycopy(elements, 0, elements, 1, i); |
|
550 |
elements[0] = elements[mask]; |
|
551 |
System.arraycopy(elements, h, elements, h + 1, mask - h); |
|
552 |
} |
|
553 |
elements[h] = null; |
|
554 |
head = (h + 1) & mask; |
|
555 |
return false; |
|
556 |
} else { |
|
557 |
if (i < t) { // Copy the null tail as well |
|
558 |
System.arraycopy(elements, i + 1, elements, i, back); |
|
559 |
tail = t - 1; |
|
560 |
} else { // Wrap around |
|
561 |
System.arraycopy(elements, i + 1, elements, i, mask - i); |
|
562 |
elements[mask] = elements[0]; |
|
563 |
System.arraycopy(elements, 1, elements, 0, t); |
|
564 |
tail = (t - 1) & mask; |
|
565 |
} |
|
566 |
return true; |
|
567 |
} |
|
568 |
} |
|
569 |
||
570 |
// *** Collection Methods *** |
|
571 |
||
572 |
/** |
|
573 |
* Returns the number of elements in this deque. |
|
574 |
* |
|
575 |
* @return the number of elements in this deque |
|
576 |
*/ |
|
577 |
public int size() { |
|
578 |
return (tail - head) & (elements.length - 1); |
|
579 |
} |
|
580 |
||
581 |
/** |
|
582 |
* Returns <tt>true</tt> if this deque contains no elements. |
|
583 |
* |
|
584 |
* @return <tt>true</tt> if this deque contains no elements |
|
585 |
*/ |
|
586 |
public boolean isEmpty() { |
|
587 |
return head == tail; |
|
588 |
} |
|
589 |
||
590 |
/** |
|
591 |
* Returns an iterator over the elements in this deque. The elements |
|
592 |
* will be ordered from first (head) to last (tail). This is the same |
|
593 |
* order that elements would be dequeued (via successive calls to |
|
594 |
* {@link #remove} or popped (via successive calls to {@link #pop}). |
|
595 |
* |
|
596 |
* @return an iterator over the elements in this deque |
|
597 |
*/ |
|
598 |
public Iterator<E> iterator() { |
|
599 |
return new DeqIterator(); |
|
600 |
} |
|
601 |
||
602 |
public Iterator<E> descendingIterator() { |
|
603 |
return new DescendingIterator(); |
|
604 |
} |
|
605 |
||
606 |
private class DeqIterator implements Iterator<E> { |
|
607 |
/** |
|
608 |
* Index of element to be returned by subsequent call to next. |
|
609 |
*/ |
|
610 |
private int cursor = head; |
|
611 |
||
612 |
/** |
|
613 |
* Tail recorded at construction (also in remove), to stop |
|
614 |
* iterator and also to check for comodification. |
|
615 |
*/ |
|
616 |
private int fence = tail; |
|
617 |
||
618 |
/** |
|
619 |
* Index of element returned by most recent call to next. |
|
620 |
* Reset to -1 if element is deleted by a call to remove. |
|
621 |
*/ |
|
622 |
private int lastRet = -1; |
|
623 |
||
624 |
public boolean hasNext() { |
|
625 |
return cursor != fence; |
|
626 |
} |
|
627 |
||
628 |
public E next() { |
|
629 |
if (cursor == fence) |
|
630 |
throw new NoSuchElementException(); |
|
631 |
E result = elements[cursor]; |
|
632 |
// This check doesn't catch all possible comodifications, |
|
633 |
// but does catch the ones that corrupt traversal |
|
634 |
if (tail != fence || result == null) |
|
635 |
throw new ConcurrentModificationException(); |
|
636 |
lastRet = cursor; |
|
637 |
cursor = (cursor + 1) & (elements.length - 1); |
|
638 |
return result; |
|
639 |
} |
|
640 |
||
641 |
public void remove() { |
|
642 |
if (lastRet < 0) |
|
643 |
throw new IllegalStateException(); |
|
644 |
if (delete(lastRet)) { // if left-shifted, undo increment in next() |
|
645 |
cursor = (cursor - 1) & (elements.length - 1); |
|
646 |
fence = tail; |
|
647 |
} |
|
648 |
lastRet = -1; |
|
649 |
} |
|
650 |
} |
|
651 |
||
652 |
private class DescendingIterator implements Iterator<E> { |
|
653 |
/* |
|
654 |
* This class is nearly a mirror-image of DeqIterator, using |
|
655 |
* tail instead of head for initial cursor, and head instead of |
|
656 |
* tail for fence. |
|
657 |
*/ |
|
658 |
private int cursor = tail; |
|
659 |
private int fence = head; |
|
660 |
private int lastRet = -1; |
|
661 |
||
662 |
public boolean hasNext() { |
|
663 |
return cursor != fence; |
|
664 |
} |
|
665 |
||
666 |
public E next() { |
|
667 |
if (cursor == fence) |
|
668 |
throw new NoSuchElementException(); |
|
669 |
cursor = (cursor - 1) & (elements.length - 1); |
|
670 |
E result = elements[cursor]; |
|
671 |
if (head != fence || result == null) |
|
672 |
throw new ConcurrentModificationException(); |
|
673 |
lastRet = cursor; |
|
674 |
return result; |
|
675 |
} |
|
676 |
||
677 |
public void remove() { |
|
678 |
if (lastRet < 0) |
|
679 |
throw new IllegalStateException(); |
|
680 |
if (!delete(lastRet)) { |
|
681 |
cursor = (cursor + 1) & (elements.length - 1); |
|
682 |
fence = head; |
|
683 |
} |
|
684 |
lastRet = -1; |
|
685 |
} |
|
686 |
} |
|
687 |
||
688 |
/** |
|
689 |
* Returns <tt>true</tt> if this deque contains the specified element. |
|
690 |
* More formally, returns <tt>true</tt> if and only if this deque contains |
|
691 |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
|
692 |
* |
|
693 |
* @param o object to be checked for containment in this deque |
|
694 |
* @return <tt>true</tt> if this deque contains the specified element |
|
695 |
*/ |
|
696 |
public boolean contains(Object o) { |
|
697 |
if (o == null) |
|
698 |
return false; |
|
699 |
int mask = elements.length - 1; |
|
700 |
int i = head; |
|
701 |
E x; |
|
702 |
while ( (x = elements[i]) != null) { |
|
703 |
if (o.equals(x)) |
|
704 |
return true; |
|
705 |
i = (i + 1) & mask; |
|
706 |
} |
|
707 |
return false; |
|
708 |
} |
|
709 |
||
710 |
/** |
|
711 |
* Removes a single instance of the specified element from this deque. |
|
712 |
* If the deque does not contain the element, it is unchanged. |
|
713 |
* More formally, removes the first element <tt>e</tt> such that |
|
714 |
* <tt>o.equals(e)</tt> (if such an element exists). |
|
715 |
* Returns <tt>true</tt> if this deque contained the specified element |
|
716 |
* (or equivalently, if this deque changed as a result of the call). |
|
717 |
* |
|
718 |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
|
719 |
* |
|
720 |
* @param o element to be removed from this deque, if present |
|
721 |
* @return <tt>true</tt> if this deque contained the specified element |
|
722 |
*/ |
|
723 |
public boolean remove(Object o) { |
|
724 |
return removeFirstOccurrence(o); |
|
725 |
} |
|
726 |
||
727 |
/** |
|
728 |
* Removes all of the elements from this deque. |
|
729 |
* The deque will be empty after this call returns. |
|
730 |
*/ |
|
731 |
public void clear() { |
|
732 |
int h = head; |
|
733 |
int t = tail; |
|
734 |
if (h != t) { // clear all cells |
|
735 |
head = tail = 0; |
|
736 |
int i = h; |
|
737 |
int mask = elements.length - 1; |
|
738 |
do { |
|
739 |
elements[i] = null; |
|
740 |
i = (i + 1) & mask; |
|
741 |
} while (i != t); |
|
742 |
} |
|
743 |
} |
|
744 |
||
745 |
/** |
|
746 |
* Returns an array containing all of the elements in this deque |
|
747 |
* in proper sequence (from first to last element). |
|
748 |
* |
|
749 |
* <p>The returned array will be "safe" in that no references to it are |
|
750 |
* maintained by this deque. (In other words, this method must allocate |
|
751 |
* a new array). The caller is thus free to modify the returned array. |
|
752 |
* |
|
753 |
* <p>This method acts as bridge between array-based and collection-based |
|
754 |
* APIs. |
|
755 |
* |
|
756 |
* @return an array containing all of the elements in this deque |
|
757 |
*/ |
|
758 |
public Object[] toArray() { |
|
759 |
return copyElements(new Object[size()]); |
|
760 |
} |
|
761 |
||
762 |
/** |
|
763 |
* Returns an array containing all of the elements in this deque in |
|
764 |
* proper sequence (from first to last element); the runtime type of the |
|
765 |
* returned array is that of the specified array. If the deque fits in |
|
766 |
* the specified array, it is returned therein. Otherwise, a new array |
|
767 |
* is allocated with the runtime type of the specified array and the |
|
768 |
* size of this deque. |
|
769 |
* |
|
770 |
* <p>If this deque fits in the specified array with room to spare |
|
771 |
* (i.e., the array has more elements than this deque), the element in |
|
772 |
* the array immediately following the end of the deque is set to |
|
773 |
* <tt>null</tt>. |
|
774 |
* |
|
775 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
|
776 |
* array-based and collection-based APIs. Further, this method allows |
|
777 |
* precise control over the runtime type of the output array, and may, |
|
778 |
* under certain circumstances, be used to save allocation costs. |
|
779 |
* |
|
780 |
* <p>Suppose <tt>x</tt> is a deque known to contain only strings. |
|
781 |
* The following code can be used to dump the deque into a newly |
|
782 |
* allocated array of <tt>String</tt>: |
|
783 |
* |
|
784 |
* <pre> |
|
785 |
* String[] y = x.toArray(new String[0]);</pre> |
|
786 |
* |
|
787 |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
|
788 |
* <tt>toArray()</tt>. |
|
789 |
* |
|
790 |
* @param a the array into which the elements of the deque are to |
|
791 |
* be stored, if it is big enough; otherwise, a new array of the |
|
792 |
* same runtime type is allocated for this purpose |
|
793 |
* @return an array containing all of the elements in this deque |
|
794 |
* @throws ArrayStoreException if the runtime type of the specified array |
|
795 |
* is not a supertype of the runtime type of every element in |
|
796 |
* this deque |
|
797 |
* @throws NullPointerException if the specified array is null |
|
798 |
*/ |
|
13795
73850c397272
7193406: Clean-up JDK Build Warnings in java.util, java.io
dxu
parents:
12448
diff
changeset
|
799 |
@SuppressWarnings("unchecked") |
2 | 800 |
public <T> T[] toArray(T[] a) { |
801 |
int size = size(); |
|
802 |
if (a.length < size) |
|
803 |
a = (T[])java.lang.reflect.Array.newInstance( |
|
804 |
a.getClass().getComponentType(), size); |
|
805 |
copyElements(a); |
|
806 |
if (a.length > size) |
|
807 |
a[size] = null; |
|
808 |
return a; |
|
809 |
} |
|
810 |
||
811 |
// *** Object methods *** |
|
812 |
||
813 |
/** |
|
814 |
* Returns a copy of this deque. |
|
815 |
* |
|
816 |
* @return a copy of this deque |
|
817 |
*/ |
|
818 |
public ArrayDeque<E> clone() { |
|
819 |
try { |
|
12448 | 820 |
@SuppressWarnings("unchecked") |
821 |
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
|
2 | 822 |
result.elements = Arrays.copyOf(elements, elements.length); |
823 |
return result; |
|
824 |
||
825 |
} catch (CloneNotSupportedException e) { |
|
826 |
throw new AssertionError(); |
|
827 |
} |
|
828 |
} |
|
829 |
||
830 |
/** |
|
831 |
* Appease the serialization gods. |
|
832 |
*/ |
|
833 |
private static final long serialVersionUID = 2340985798034038923L; |
|
834 |
||
835 |
/** |
|
836 |
* Serialize this deque. |
|
837 |
* |
|
838 |
* @serialData The current size (<tt>int</tt>) of the deque, |
|
839 |
* followed by all of its elements (each an object reference) in |
|
840 |
* first-to-last order. |
|
841 |
*/ |
|
842 |
private void writeObject(ObjectOutputStream s) throws IOException { |
|
843 |
s.defaultWriteObject(); |
|
844 |
||
845 |
// Write out size |
|
846 |
s.writeInt(size()); |
|
847 |
||
848 |
// Write out elements in order. |
|
849 |
int mask = elements.length - 1; |
|
850 |
for (int i = head; i != tail; i = (i + 1) & mask) |
|
851 |
s.writeObject(elements[i]); |
|
852 |
} |
|
853 |
||
854 |
/** |
|
855 |
* Deserialize this deque. |
|
856 |
*/ |
|
12448 | 857 |
@SuppressWarnings("unchecked") |
2 | 858 |
private void readObject(ObjectInputStream s) |
859 |
throws IOException, ClassNotFoundException { |
|
860 |
s.defaultReadObject(); |
|
861 |
||
862 |
// Read in size and allocate array |
|
863 |
int size = s.readInt(); |
|
864 |
allocateElements(size); |
|
865 |
head = 0; |
|
866 |
tail = size; |
|
867 |
||
868 |
// Read in all elements in the proper order. |
|
869 |
for (int i = 0; i < size; i++) |
|
870 |
elements[i] = (E)s.readObject(); |
|
871 |
} |
|
872 |
} |