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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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/* |
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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.util.Spliterator; |
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import java.util.stream.Stream; |
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import java.util.stream.Streams; |
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import java.util.function.Block; |
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|
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import java.io.Serializable; |
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import java.util.function.Consumer; |
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|
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/** |
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* Resizable-array implementation of the {@link Deque} interface. Array |
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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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* <p>Most {@code ArrayDeque} operations run in amortized constant time. |
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* Exceptions include |
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* {@link #remove(Object) remove}, |
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* {@link #removeFirstOccurrence removeFirstOccurrence}, |
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* {@link #removeLastOccurrence removeLastOccurrence}, |
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* {@link #contains contains}, |
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* {@link #iterator iterator.remove()}, |
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* and the bulk operations, all of which run in linear time. |
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* |
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* <p>The iterators returned by this class's {@link #iterator() iterator} |
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* method are <em>fail-fast</em>: If the deque is modified at any time after |
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* the iterator is created, in any way except through the iterator's own |
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* {@code remove} 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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* <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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* throw {@code ConcurrentModificationException} 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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* @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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* @param <E> the type of elements held in this deque |
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*/ |
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public class ArrayDeque<E> extends AbstractCollection<E> |
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implements Deque<E>, Cloneable, java.io.Serializable |
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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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} |
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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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/** |
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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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E result = (E) elements[h]; |
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// Element is null if deque empty |
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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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if (result != 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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} |
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return result; |
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} |
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|
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int t = (tail - 1) & (elements.length - 1); |
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@SuppressWarnings("unchecked") |
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E result = (E) elements[t]; |
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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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if (result != null) { |
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elements[t] = null; |
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tail = t; |
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} |
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return result; |
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} |
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|
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* @return {@code true} if the deque contained the specified element |
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*/ |
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public boolean removeFirstOccurrence(Object o) { |
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if (o == null) |
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return false; |
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int mask = elements.length - 1; |
321 |
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int i = head; |
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Object x; |
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while ( (x = elements[i]) != null) { |
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if (o.equals(x)) { |
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delete(i); |
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return true; |
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if (o != null) { |
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int mask = elements.length - 1; |
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int i = head; |
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for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) { |
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if (o.equals(x)) { |
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delete(i); |
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return true; |
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} |
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} |
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i = (i + 1) & mask; |
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} |
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return false; |
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} |
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* @return {@code true} if the deque contained the specified element |
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*/ |
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public boolean removeLastOccurrence(Object o) { |
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if (o == null) |
345 |
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return false; |
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int mask = elements.length - 1; |
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int i = (tail - 1) & mask; |
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Object x; |
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while ( (x = elements[i]) != null) { |
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if (o.equals(x)) { |
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delete(i); |
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return true; |
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if (o != null) { |
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int mask = elements.length - 1; |
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int i = (tail - 1) & mask; |
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for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) { |
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if (o.equals(x)) { |
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delete(i); |
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return true; |
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} |
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} |
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i = (i - 1) & mask; |
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} |
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return false; |
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} |
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} |
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} |
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|
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+ |
/** |
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* This class is nearly a mirror-image of DeqIterator, using tail |
613 |
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* instead of head for initial cursor, and head instead of tail |
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* for fence. |
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*/ |
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private class DescendingIterator implements Iterator<E> { |
662 |
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/* |
663 |
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* This class is nearly a mirror-image of DeqIterator, using |
664 |
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* tail instead of head for initial cursor, and head instead of |
665 |
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* tail for fence. |
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*/ |
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private int cursor = tail; |
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private int fence = head; |
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private int lastRet = -1; |
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* @return {@code true} if this deque contains the specified element |
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*/ |
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public boolean contains(Object o) { |
657 |
< |
if (o == null) |
658 |
< |
return false; |
659 |
< |
int mask = elements.length - 1; |
660 |
< |
int i = head; |
661 |
< |
Object x; |
662 |
< |
while ( (x = elements[i]) != null) { |
663 |
< |
if (o.equals(x)) |
714 |
< |
return true; |
715 |
< |
i = (i + 1) & mask; |
657 |
> |
if (o != null) { |
658 |
> |
int mask = elements.length - 1; |
659 |
> |
int i = head; |
660 |
> |
for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) { |
661 |
> |
if (o.equals(x)) |
662 |
> |
return true; |
663 |
> |
} |
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} |
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return false; |
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} |
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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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* |
676 |
< |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
676 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
677 |
|
* |
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|
* @param o element to be removed from this deque, if present |
679 |
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* @return {@code true} if this deque contained the specified element |
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* @return an array containing all of the elements in this deque |
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*/ |
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public Object[] toArray() { |
717 |
< |
return copyElements(new Object[size()]); |
717 |
> |
final int head = this.head; |
718 |
> |
final int tail = this.tail; |
719 |
> |
boolean wrap = (tail < head); |
720 |
> |
int end = wrap ? tail + elements.length : tail; |
721 |
> |
Object[] a = Arrays.copyOfRange(elements, head, end); |
722 |
> |
if (wrap) |
723 |
> |
System.arraycopy(elements, 0, a, elements.length - head, tail); |
724 |
> |
return a; |
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|
} |
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|
|
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|
/** |
746 |
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* The following code can be used to dump the deque into a newly |
747 |
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* allocated array of {@code String}: |
748 |
|
* |
749 |
< |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
749 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
750 |
|
* |
751 |
|
* Note that {@code toArray(new Object[0])} is identical in function to |
752 |
|
* {@code toArray()}. |
762 |
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*/ |
763 |
|
@SuppressWarnings("unchecked") |
764 |
|
public <T> T[] toArray(T[] a) { |
765 |
< |
int size = size(); |
766 |
< |
if (a.length < size) |
767 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
768 |
< |
a.getClass().getComponentType(), size); |
769 |
< |
copyElements(a); |
770 |
< |
if (a.length > size) |
771 |
< |
a[size] = null; |
765 |
> |
final int head = this.head; |
766 |
> |
final int tail = this.tail; |
767 |
> |
boolean wrap = (tail < head); |
768 |
> |
int size = (tail - head) + (wrap ? elements.length : 0); |
769 |
> |
int firstLeg = size - (wrap ? tail : 0); |
770 |
> |
int len = a.length; |
771 |
> |
if (size > len) { |
772 |
> |
a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
773 |
> |
a.getClass()); |
774 |
> |
} else { |
775 |
> |
System.arraycopy(elements, head, a, 0, firstLeg); |
776 |
> |
if (size < len) |
777 |
> |
a[size] = null; |
778 |
> |
} |
779 |
> |
if (wrap) |
780 |
> |
System.arraycopy(elements, 0, a, firstLeg, tail); |
781 |
|
return a; |
782 |
|
} |
783 |
|
|
804 |
|
/** |
805 |
|
* Saves this deque to a stream (that is, serializes it). |
806 |
|
* |
807 |
+ |
* @param s the stream |
808 |
+ |
* @throws java.io.IOException if an I/O error occurs |
809 |
|
* @serialData The current size ({@code int}) of the deque, |
810 |
|
* followed by all of its elements (each an object reference) in |
811 |
|
* first-to-last order. |
825 |
|
|
826 |
|
/** |
827 |
|
* Reconstitutes this deque from a stream (that is, deserializes it). |
828 |
+ |
* @param s the stream |
829 |
+ |
* @throws ClassNotFoundException if the class of a serialized object |
830 |
+ |
* could not be found |
831 |
+ |
* @throws java.io.IOException if an I/O error occurs |
832 |
|
*/ |
833 |
|
private void readObject(java.io.ObjectInputStream s) |
834 |
|
throws java.io.IOException, ClassNotFoundException { |
845 |
|
elements[i] = s.readObject(); |
846 |
|
} |
847 |
|
|
848 |
< |
public Stream<E> stream() { |
849 |
< |
int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED; |
880 |
< |
return Streams.stream |
881 |
< |
(() -> new DeqSpliterator<E>(this, head, tail), flags); |
882 |
< |
} |
883 |
< |
public Stream<E> parallelStream() { |
884 |
< |
int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED; |
885 |
< |
return Streams.parallelStream |
886 |
< |
(() -> new DeqSpliterator<E>(this, head, tail), flags); |
848 |
> |
public Spliterator<E> spliterator() { |
849 |
> |
return new DeqSpliterator<E>(this, -1, -1); |
850 |
|
} |
851 |
|
|
852 |
< |
|
890 |
< |
static final class DeqSpliterator<E> implements Spliterator<E>, Iterator<E> { |
852 |
> |
static final class DeqSpliterator<E> implements Spliterator<E> { |
853 |
|
private final ArrayDeque<E> deq; |
854 |
< |
private final Object[] array; |
855 |
< |
private final int fence; // initially tail |
894 |
< |
private int index; // current index, modified on traverse/split |
854 |
> |
private int fence; // -1 until first use |
855 |
> |
private int index; // current index, modified on traverse/split |
856 |
|
|
857 |
< |
/** Create new spliterator covering the given array and range */ |
857 |
> |
/** Creates new spliterator covering the given array and range */ |
858 |
|
DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) { |
859 |
< |
this.deq = deq; this.array = deq.elements; |
860 |
< |
this.index = origin; this.fence = fence; |
859 |
> |
this.deq = deq; |
860 |
> |
this.index = origin; |
861 |
> |
this.fence = fence; |
862 |
> |
} |
863 |
> |
|
864 |
> |
private int getFence() { // force initialization |
865 |
> |
int t; |
866 |
> |
if ((t = fence) < 0) { |
867 |
> |
t = fence = deq.tail; |
868 |
> |
index = deq.head; |
869 |
> |
} |
870 |
> |
return t; |
871 |
|
} |
872 |
|
|
873 |
< |
public DeqSpliterator<E> trySplit() { |
874 |
< |
int n = array.length; |
904 |
< |
int h = index, t = fence; |
873 |
> |
public Spliterator<E> trySplit() { |
874 |
> |
int t = getFence(), h = index, n = deq.elements.length; |
875 |
|
if (h != t && ((h + 1) & (n - 1)) != t) { |
876 |
|
if (h > t) |
877 |
|
t += n; |
878 |
|
int m = ((h + t) >>> 1) & (n - 1); |
879 |
< |
return new DeqSpliterator<E>(deq, h, index = m); |
879 |
> |
return new DeqSpliterator<>(deq, h, index = m); |
880 |
|
} |
881 |
|
return null; |
882 |
|
} |
883 |
|
|
884 |
< |
@SuppressWarnings("unchecked") |
885 |
< |
public void forEach(Block<? super E> block) { |
916 |
< |
if (block == null) |
884 |
> |
public void forEachRemaining(Consumer<? super E> consumer) { |
885 |
> |
if (consumer == null) |
886 |
|
throw new NullPointerException(); |
887 |
< |
Object[] a = array; |
888 |
< |
if (a != deq.elements) |
920 |
< |
throw new ConcurrentModificationException(); |
921 |
< |
int m = a.length - 1, f = fence, i = index; |
887 |
> |
Object[] a = deq.elements; |
888 |
> |
int m = a.length - 1, f = getFence(), i = index; |
889 |
|
index = f; |
890 |
|
while (i != f) { |
891 |
< |
Object e = a[i]; |
891 |
> |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
892 |
> |
i = (i + 1) & m; |
893 |
|
if (e == null) |
894 |
|
throw new ConcurrentModificationException(); |
895 |
< |
block.accept((E)e); |
928 |
< |
i = (i + 1) & m; |
895 |
> |
consumer.accept(e); |
896 |
|
} |
897 |
|
} |
898 |
|
|
899 |
< |
@SuppressWarnings("unchecked") |
900 |
< |
public boolean tryAdvance(Block<? super E> block) { |
934 |
< |
if (block == null) |
899 |
> |
public boolean tryAdvance(Consumer<? super E> consumer) { |
900 |
> |
if (consumer == null) |
901 |
|
throw new NullPointerException(); |
902 |
< |
Object[] a = array; |
903 |
< |
if (a != deq.elements) |
904 |
< |
throw new ConcurrentModificationException(); |
905 |
< |
int m = a.length - 1, i = index; |
906 |
< |
if (i != fence) { |
941 |
< |
Object e = a[i]; |
902 |
> |
Object[] a = deq.elements; |
903 |
> |
int m = a.length - 1, f = getFence(), i = index; |
904 |
> |
if (i != f) { |
905 |
> |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
906 |
> |
index = (i + 1) & m; |
907 |
|
if (e == null) |
908 |
|
throw new ConcurrentModificationException(); |
909 |
< |
block.accept((E)e); |
945 |
< |
index = (i + 1) & m; |
909 |
> |
consumer.accept(e); |
910 |
|
return true; |
911 |
|
} |
912 |
|
return false; |
913 |
|
} |
914 |
|
|
915 |
< |
// Iterator support |
916 |
< |
public Iterator<E> iterator() { |
917 |
< |
return this; |
918 |
< |
} |
919 |
< |
|
956 |
< |
public boolean hasNext() { |
957 |
< |
return index >= 0 && index != fence; |
958 |
< |
} |
959 |
< |
|
960 |
< |
@SuppressWarnings("unchecked") |
961 |
< |
public E next() { |
962 |
< |
if (index < 0 || index == fence) |
963 |
< |
throw new NoSuchElementException(); |
964 |
< |
Object[] a = array; |
965 |
< |
if (a != deq.elements) |
966 |
< |
throw new ConcurrentModificationException(); |
967 |
< |
Object e = a[index]; |
968 |
< |
if (e == null) |
969 |
< |
throw new ConcurrentModificationException(); |
970 |
< |
index = (index + 1) & (a.length - 1); |
971 |
< |
return (E) e; |
915 |
> |
public long estimateSize() { |
916 |
> |
int n = getFence() - index; |
917 |
> |
if (n < 0) |
918 |
> |
n += deq.elements.length; |
919 |
> |
return (long) n; |
920 |
|
} |
921 |
|
|
922 |
< |
public void remove() { throw new UnsupportedOperationException(); } |
923 |
< |
|
924 |
< |
// Other spliterator methods |
925 |
< |
public long estimateSize() { |
978 |
< |
int n = fence - index; |
979 |
< |
if (n < 0) |
980 |
< |
n += array.length; |
981 |
< |
return (long)n; |
922 |
> |
@Override |
923 |
> |
public int characteristics() { |
924 |
> |
return Spliterator.ORDERED | Spliterator.SIZED | |
925 |
> |
Spliterator.NONNULL | Spliterator.SUBSIZED; |
926 |
|
} |
983 |
– |
public boolean hasExactSize() { return true; } |
984 |
– |
public boolean hasExactSplits() { return true; } |
927 |
|
} |
928 |
|
|
929 |
|
} |