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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/licenses/publicdomain. |
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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.*; // for javadoc (till 6280605 is fixed) |
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import java.io.*; |
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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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import java.util.stream.Stream; |
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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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* <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 <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>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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* 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}/../guide/collections/index.html"> |
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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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* @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, Serializable |
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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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transient Object[] elements; // non-private to simplify nested class access |
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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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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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transient int tail; |
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|
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/** |
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* The minimum capacity that we'll use for a newly created deque. |
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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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* Allocates 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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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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elements = 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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* Doubles 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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Object[] a = 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 = (E[])a; |
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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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/** |
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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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public ArrayDeque() { |
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elements = (E[]) new Object[16]; |
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elements = new Object[16]; |
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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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* @return {@code true} (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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* 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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* @return {@code true} (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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|
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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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@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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|
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public E pollLast() { |
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int t = (tail - 1) & (elements.length - 1); |
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E result = elements[t]; |
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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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* @throws NoSuchElementException {@inheritDoc} |
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*/ |
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public E getFirst() { |
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E x = elements[head]; |
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if (x == null) |
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@SuppressWarnings("unchecked") |
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E result = (E) elements[head]; |
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if (result == null) |
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throw new NoSuchElementException(); |
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return x; |
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return result; |
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} |
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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 getLast() { |
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E x = elements[(tail - 1) & (elements.length - 1)]; |
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if (x == null) |
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> |
@SuppressWarnings("unchecked") |
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> |
E result = (E) elements[(tail - 1) & (elements.length - 1)]; |
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if (result == null) |
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throw new NoSuchElementException(); |
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return x; |
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return result; |
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} |
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|
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+ |
@SuppressWarnings("unchecked") |
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public E peekFirst() { |
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return elements[head]; // elements[head] is null if deque empty |
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// elements[head] is null if deque empty |
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return (E) elements[head]; |
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} |
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|
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+ |
@SuppressWarnings("unchecked") |
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public E peekLast() { |
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return elements[(tail - 1) & (elements.length - 1)]; |
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> |
return (E) elements[(tail - 1) & (elements.length - 1)]; |
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} |
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|
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/** |
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* Removes the first occurrence of the specified element in this |
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* deque (when traversing the deque from head to tail). |
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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 <tt>e</tt> such that |
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< |
* <tt>o.equals(e)</tt> (if such an element exists). |
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* Returns <tt>true</tt> if this deque contained the specified element |
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> |
* More formally, removes the first element {@code e} such that |
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> |
* {@code o.equals(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 <tt>true</tt> if the deque contained the specified element |
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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; |
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< |
int i = head; |
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< |
E 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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* Removes the last occurrence of the specified element in this |
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* deque (when traversing the deque from head to tail). |
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* If the deque does not contain the element, it is unchanged. |
| 336 |
< |
* More formally, removes the last element <tt>e</tt> such that |
| 337 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
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< |
* Returns <tt>true</tt> if this deque contained the specified element |
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> |
* More formally, removes the last element {@code e} such that |
| 337 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 338 |
> |
* 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 <tt>true</tt> if the deque contained the specified element |
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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) { |
| 345 |
< |
if (o == null) |
| 346 |
< |
return false; |
| 347 |
< |
int mask = elements.length - 1; |
| 348 |
< |
int i = (tail - 1) & mask; |
| 349 |
< |
E x; |
| 350 |
< |
while ( (x = elements[i]) != null) { |
| 351 |
< |
if (o.equals(x)) { |
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< |
delete(i); |
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< |
return true; |
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> |
if (o != null) { |
| 346 |
> |
int mask = elements.length - 1; |
| 347 |
> |
int i = (tail - 1) & mask; |
| 348 |
> |
for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) { |
| 349 |
> |
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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|
* <p>This method is equivalent to {@link #addLast}. |
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|
* |
| 365 |
|
* @param e the element to add |
| 366 |
< |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
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> |
* @return {@code true} (as specified by {@link Collection#add}) |
| 367 |
|
* @throws NullPointerException if the specified element is null |
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|
*/ |
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|
public boolean add(E e) { |
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* <p>This method is equivalent to {@link #offerLast}. |
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* |
| 379 |
|
* @param e the element to add |
| 380 |
< |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
| 380 |
> |
* @return {@code true} (as specified by {@link Queue#offer}) |
| 381 |
|
* @throws NullPointerException if the specified element is null |
| 382 |
|
*/ |
| 383 |
|
public boolean offer(E e) { |
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|
/** |
| 403 |
|
* Retrieves and removes the head of the queue represented by this deque |
| 404 |
|
* (in other words, the first element of this deque), or returns |
| 405 |
< |
* <tt>null</tt> if this deque is empty. |
| 405 |
> |
* {@code null} if this deque is empty. |
| 406 |
|
* |
| 407 |
|
* <p>This method is equivalent to {@link #pollFirst}. |
| 408 |
|
* |
| 409 |
|
* @return the head of the queue represented by this deque, or |
| 410 |
< |
* <tt>null</tt> if this deque is empty |
| 410 |
> |
* {@code null} if this deque is empty |
| 411 |
|
*/ |
| 412 |
|
public E poll() { |
| 413 |
|
return pollFirst(); |
| 429 |
|
|
| 430 |
|
/** |
| 431 |
|
* Retrieves, but does not remove, the head of the queue represented by |
| 432 |
< |
* this deque, or returns <tt>null</tt> if this deque is empty. |
| 432 |
> |
* this deque, or returns {@code null} if this deque is empty. |
| 433 |
|
* |
| 434 |
|
* <p>This method is equivalent to {@link #peekFirst}. |
| 435 |
|
* |
| 436 |
|
* @return the head of the queue represented by this deque, or |
| 437 |
< |
* <tt>null</tt> if this deque is empty |
| 437 |
> |
* {@code null} if this deque is empty |
| 438 |
|
*/ |
| 439 |
|
public E peek() { |
| 440 |
|
return peekFirst(); |
| 469 |
|
return removeFirst(); |
| 470 |
|
} |
| 471 |
|
|
| 472 |
+ |
private void checkInvariants() { |
| 473 |
+ |
assert elements[tail] == null; |
| 474 |
+ |
assert head == tail ? elements[head] == null : |
| 475 |
+ |
(elements[head] != null && |
| 476 |
+ |
elements[(tail - 1) & (elements.length - 1)] != null); |
| 477 |
+ |
assert elements[(head - 1) & (elements.length - 1)] == null; |
| 478 |
+ |
} |
| 479 |
+ |
|
| 480 |
|
/** |
| 481 |
|
* Removes the element at the specified position in the elements array, |
| 482 |
|
* adjusting head and tail as necessary. This can result in motion of |
| 488 |
|
* @return true if elements moved backwards |
| 489 |
|
*/ |
| 490 |
|
private boolean delete(int i) { |
| 491 |
< |
int mask = elements.length - 1; |
| 492 |
< |
|
| 493 |
< |
// Invariant: head <= i < tail mod circularity |
| 494 |
< |
if (((i - head) & mask) >= ((tail - head) & mask)) |
| 495 |
< |
throw new ConcurrentModificationException(); |
| 496 |
< |
|
| 497 |
< |
// Case 1: Deque doesn't wrap |
| 498 |
< |
// Case 2: Deque does wrap and removed element is in the head portion |
| 499 |
< |
if (i >= head) { |
| 500 |
< |
System.arraycopy(elements, head, elements, head + 1, i - head); |
| 501 |
< |
elements[head] = null; |
| 502 |
< |
head = (head + 1) & mask; |
| 491 |
> |
checkInvariants(); |
| 492 |
> |
final Object[] elements = this.elements; |
| 493 |
> |
final int mask = elements.length - 1; |
| 494 |
> |
final int h = head; |
| 495 |
> |
final int t = tail; |
| 496 |
> |
final int front = (i - h) & mask; |
| 497 |
> |
final int back = (t - i) & mask; |
| 498 |
> |
|
| 499 |
> |
// Invariant: head <= i < tail mod circularity |
| 500 |
> |
if (front >= ((t - h) & mask)) |
| 501 |
> |
throw new ConcurrentModificationException(); |
| 502 |
> |
|
| 503 |
> |
// Optimize for least element motion |
| 504 |
> |
if (front < back) { |
| 505 |
> |
if (h <= i) { |
| 506 |
> |
System.arraycopy(elements, h, elements, h + 1, front); |
| 507 |
> |
} else { // Wrap around |
| 508 |
> |
System.arraycopy(elements, 0, elements, 1, i); |
| 509 |
> |
elements[0] = elements[mask]; |
| 510 |
> |
System.arraycopy(elements, h, elements, h + 1, mask - h); |
| 511 |
> |
} |
| 512 |
> |
elements[h] = null; |
| 513 |
> |
head = (h + 1) & mask; |
| 514 |
|
return false; |
| 515 |
+ |
} else { |
| 516 |
+ |
if (i < t) { // Copy the null tail as well |
| 517 |
+ |
System.arraycopy(elements, i + 1, elements, i, back); |
| 518 |
+ |
tail = t - 1; |
| 519 |
+ |
} else { // Wrap around |
| 520 |
+ |
System.arraycopy(elements, i + 1, elements, i, mask - i); |
| 521 |
+ |
elements[mask] = elements[0]; |
| 522 |
+ |
System.arraycopy(elements, 1, elements, 0, t); |
| 523 |
+ |
tail = (t - 1) & mask; |
| 524 |
+ |
} |
| 525 |
+ |
return true; |
| 526 |
|
} |
| 507 |
– |
|
| 508 |
– |
// Case 3: Deque wraps and removed element is in the tail portion |
| 509 |
– |
tail--; |
| 510 |
– |
System.arraycopy(elements, i + 1, elements, i, tail - i); |
| 511 |
– |
elements[tail] = null; |
| 512 |
– |
return true; |
| 527 |
|
} |
| 528 |
|
|
| 529 |
|
// *** Collection Methods *** |
| 538 |
|
} |
| 539 |
|
|
| 540 |
|
/** |
| 541 |
< |
* Returns <tt>true</tt> if this deque contains no elements. |
| 541 |
> |
* Returns {@code true} if this deque contains no elements. |
| 542 |
|
* |
| 543 |
< |
* @return <tt>true</tt> if this deque contains no elements |
| 543 |
> |
* @return {@code true} if this deque contains no elements |
| 544 |
|
*/ |
| 545 |
|
public boolean isEmpty() { |
| 546 |
|
return head == tail; |
| 585 |
|
} |
| 586 |
|
|
| 587 |
|
public E next() { |
| 574 |
– |
E result; |
| 588 |
|
if (cursor == fence) |
| 589 |
|
throw new NoSuchElementException(); |
| 590 |
+ |
@SuppressWarnings("unchecked") |
| 591 |
+ |
E result = (E) elements[cursor]; |
| 592 |
|
// This check doesn't catch all possible comodifications, |
| 593 |
|
// but does catch the ones that corrupt traversal |
| 594 |
< |
if (tail != fence || (result = elements[cursor]) == null) |
| 594 |
> |
if (tail != fence || result == null) |
| 595 |
|
throw new ConcurrentModificationException(); |
| 596 |
|
lastRet = cursor; |
| 597 |
|
cursor = (cursor + 1) & (elements.length - 1); |
| 601 |
|
public void remove() { |
| 602 |
|
if (lastRet < 0) |
| 603 |
|
throw new IllegalStateException(); |
| 604 |
< |
if (delete(lastRet)) // if left-shifted, undo increment in next() |
| 604 |
> |
if (delete(lastRet)) { // if left-shifted, undo increment in next() |
| 605 |
|
cursor = (cursor - 1) & (elements.length - 1); |
| 606 |
+ |
fence = tail; |
| 607 |
+ |
} |
| 608 |
|
lastRet = -1; |
| 592 |
– |
fence = tail; |
| 609 |
|
} |
| 610 |
|
} |
| 611 |
|
|
| 612 |
< |
|
| 612 |
> |
/** |
| 613 |
> |
* This class is nearly a mirror-image of DeqIterator, using tail |
| 614 |
> |
* instead of head for initial cursor, and head instead of tail |
| 615 |
> |
* for fence. |
| 616 |
> |
*/ |
| 617 |
|
private class DescendingIterator implements Iterator<E> { |
| 618 |
< |
/* |
| 619 |
< |
* This class is nearly a mirror-image of DeqIterator, using |
| 620 |
< |
* (tail-1) instead of head for initial cursor, (head-1) |
| 601 |
< |
* instead of tail for fence, and elements.length instead of -1 |
| 602 |
< |
* for sentinel. It shares the same structure, but not many |
| 603 |
< |
* actual lines of code. |
| 604 |
< |
*/ |
| 605 |
< |
private int cursor = (tail - 1) & (elements.length - 1); |
| 606 |
< |
private int fence = (head - 1) & (elements.length - 1); |
| 607 |
< |
private int lastRet = elements.length; |
| 618 |
> |
private int cursor = tail; |
| 619 |
> |
private int fence = head; |
| 620 |
> |
private int lastRet = -1; |
| 621 |
|
|
| 622 |
|
public boolean hasNext() { |
| 623 |
|
return cursor != fence; |
| 624 |
|
} |
| 625 |
|
|
| 626 |
|
public E next() { |
| 614 |
– |
E result; |
| 627 |
|
if (cursor == fence) |
| 628 |
|
throw new NoSuchElementException(); |
| 629 |
< |
if (((head - 1) & (elements.length - 1)) != fence || |
| 630 |
< |
(result = elements[cursor]) == null) |
| 629 |
> |
cursor = (cursor - 1) & (elements.length - 1); |
| 630 |
> |
@SuppressWarnings("unchecked") |
| 631 |
> |
E result = (E) elements[cursor]; |
| 632 |
> |
if (head != fence || result == null) |
| 633 |
|
throw new ConcurrentModificationException(); |
| 634 |
|
lastRet = cursor; |
| 621 |
– |
cursor = (cursor - 1) & (elements.length - 1); |
| 635 |
|
return result; |
| 636 |
|
} |
| 637 |
|
|
| 638 |
|
public void remove() { |
| 639 |
< |
if (lastRet >= elements.length) |
| 639 |
> |
if (lastRet < 0) |
| 640 |
|
throw new IllegalStateException(); |
| 641 |
< |
if (!delete(lastRet)) |
| 641 |
> |
if (!delete(lastRet)) { |
| 642 |
|
cursor = (cursor + 1) & (elements.length - 1); |
| 643 |
< |
lastRet = elements.length; |
| 644 |
< |
fence = (head - 1) & (elements.length - 1); |
| 643 |
> |
fence = head; |
| 644 |
> |
} |
| 645 |
> |
lastRet = -1; |
| 646 |
|
} |
| 647 |
|
} |
| 648 |
|
|
| 649 |
|
/** |
| 650 |
< |
* Returns <tt>true</tt> if this deque contains the specified element. |
| 651 |
< |
* More formally, returns <tt>true</tt> if and only if this deque contains |
| 652 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
| 650 |
> |
* Returns {@code true} if this deque contains the specified element. |
| 651 |
> |
* More formally, returns {@code true} if and only if this deque contains |
| 652 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
| 653 |
|
* |
| 654 |
|
* @param o object to be checked for containment in this deque |
| 655 |
< |
* @return <tt>true</tt> if this deque contains the specified element |
| 655 |
> |
* @return {@code true} if this deque contains the specified element |
| 656 |
|
*/ |
| 657 |
|
public boolean contains(Object o) { |
| 658 |
< |
if (o == null) |
| 659 |
< |
return false; |
| 660 |
< |
int mask = elements.length - 1; |
| 661 |
< |
int i = head; |
| 662 |
< |
E x; |
| 663 |
< |
while ( (x = elements[i]) != null) { |
| 664 |
< |
if (o.equals(x)) |
| 651 |
< |
return true; |
| 652 |
< |
i = (i + 1) & mask; |
| 658 |
> |
if (o != null) { |
| 659 |
> |
int mask = elements.length - 1; |
| 660 |
> |
int i = head; |
| 661 |
> |
for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) { |
| 662 |
> |
if (o.equals(x)) |
| 663 |
> |
return true; |
| 664 |
> |
} |
| 665 |
|
} |
| 666 |
|
return false; |
| 667 |
|
} |
| 669 |
|
/** |
| 670 |
|
* Removes a single instance of the specified element from this deque. |
| 671 |
|
* If the deque does not contain the element, it is unchanged. |
| 672 |
< |
* More formally, removes the first element <tt>e</tt> such that |
| 673 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
| 674 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
| 672 |
> |
* More formally, removes the first element {@code e} such that |
| 673 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 674 |
> |
* Returns {@code true} if this deque contained the specified element |
| 675 |
|
* (or equivalently, if this deque changed as a result of the call). |
| 676 |
|
* |
| 677 |
< |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
| 677 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
| 678 |
|
* |
| 679 |
|
* @param o element to be removed from this deque, if present |
| 680 |
< |
* @return <tt>true</tt> if this deque contained the specified element |
| 680 |
> |
* @return {@code true} if this deque contained the specified element |
| 681 |
|
*/ |
| 682 |
|
public boolean remove(Object o) { |
| 683 |
|
return removeFirstOccurrence(o); |
| 715 |
|
* @return an array containing all of the elements in this deque |
| 716 |
|
*/ |
| 717 |
|
public Object[] toArray() { |
| 718 |
< |
return copyElements(new Object[size()]); |
| 718 |
> |
final int head = this.head; |
| 719 |
> |
final int tail = this.tail; |
| 720 |
> |
boolean wrap = (tail < head); |
| 721 |
> |
int end = wrap ? tail + elements.length : tail; |
| 722 |
> |
Object[] a = Arrays.copyOfRange(elements, head, end); |
| 723 |
> |
if (wrap) |
| 724 |
> |
System.arraycopy(elements, 0, a, elements.length - head, tail); |
| 725 |
> |
return a; |
| 726 |
|
} |
| 727 |
|
|
| 728 |
|
/** |
| 736 |
|
* <p>If this deque fits in the specified array with room to spare |
| 737 |
|
* (i.e., the array has more elements than this deque), the element in |
| 738 |
|
* the array immediately following the end of the deque is set to |
| 739 |
< |
* <tt>null</tt>. |
| 739 |
> |
* {@code null}. |
| 740 |
|
* |
| 741 |
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
| 742 |
|
* array-based and collection-based APIs. Further, this method allows |
| 743 |
|
* precise control over the runtime type of the output array, and may, |
| 744 |
|
* under certain circumstances, be used to save allocation costs. |
| 745 |
|
* |
| 746 |
< |
* <p>Suppose <tt>x</tt> is a deque known to contain only strings. |
| 746 |
> |
* <p>Suppose {@code x} is a deque known to contain only strings. |
| 747 |
|
* The following code can be used to dump the deque into a newly |
| 748 |
< |
* allocated array of <tt>String</tt>: |
| 748 |
> |
* allocated array of {@code String}: |
| 749 |
|
* |
| 750 |
< |
* <pre> |
| 732 |
< |
* String[] y = x.toArray(new String[0]);</pre> |
| 750 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
| 751 |
|
* |
| 752 |
< |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
| 753 |
< |
* <tt>toArray()</tt>. |
| 752 |
> |
* Note that {@code toArray(new Object[0])} is identical in function to |
| 753 |
> |
* {@code toArray()}. |
| 754 |
|
* |
| 755 |
|
* @param a the array into which the elements of the deque are to |
| 756 |
|
* be stored, if it is big enough; otherwise, a new array of the |
| 761 |
|
* this deque |
| 762 |
|
* @throws NullPointerException if the specified array is null |
| 763 |
|
*/ |
| 764 |
+ |
@SuppressWarnings("unchecked") |
| 765 |
|
public <T> T[] toArray(T[] a) { |
| 766 |
< |
int size = size(); |
| 767 |
< |
if (a.length < size) |
| 768 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
| 769 |
< |
a.getClass().getComponentType(), size); |
| 770 |
< |
copyElements(a); |
| 771 |
< |
if (a.length > size) |
| 772 |
< |
a[size] = null; |
| 766 |
> |
final int head = this.head; |
| 767 |
> |
final int tail = this.tail; |
| 768 |
> |
boolean wrap = (tail < head); |
| 769 |
> |
int size = (tail - head) + (wrap ? elements.length : 0); |
| 770 |
> |
int firstLeg = size - (wrap ? tail : 0); |
| 771 |
> |
int len = a.length; |
| 772 |
> |
if (size > len) { |
| 773 |
> |
a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
| 774 |
> |
a.getClass()); |
| 775 |
> |
} else { |
| 776 |
> |
System.arraycopy(elements, head, a, 0, firstLeg); |
| 777 |
> |
if (size < len) |
| 778 |
> |
a[size] = null; |
| 779 |
> |
} |
| 780 |
> |
if (wrap) |
| 781 |
> |
System.arraycopy(elements, 0, a, firstLeg, tail); |
| 782 |
|
return a; |
| 783 |
|
} |
| 784 |
|
|
| 791 |
|
*/ |
| 792 |
|
public ArrayDeque<E> clone() { |
| 793 |
|
try { |
| 794 |
+ |
@SuppressWarnings("unchecked") |
| 795 |
|
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
| 796 |
< |
// These two lines are currently faster than cloning the array: |
| 768 |
< |
result.elements = (E[]) new Object[elements.length]; |
| 769 |
< |
System.arraycopy(elements, 0, result.elements, 0, elements.length); |
| 796 |
> |
result.elements = Arrays.copyOf(elements, elements.length); |
| 797 |
|
return result; |
| 771 |
– |
|
| 798 |
|
} catch (CloneNotSupportedException e) { |
| 799 |
|
throw new AssertionError(); |
| 800 |
|
} |
| 801 |
|
} |
| 802 |
|
|
| 777 |
– |
/** |
| 778 |
– |
* Appease the serialization gods. |
| 779 |
– |
*/ |
| 803 |
|
private static final long serialVersionUID = 2340985798034038923L; |
| 804 |
|
|
| 805 |
|
/** |
| 806 |
< |
* Serialize this deque. |
| 806 |
> |
* Saves this deque to a stream (that is, serializes it). |
| 807 |
|
* |
| 808 |
< |
* @serialData The current size (<tt>int</tt>) of the deque, |
| 808 |
> |
* @param s the stream |
| 809 |
> |
* @throws java.io.IOException if an I/O error occurs |
| 810 |
> |
* @serialData The current size ({@code int}) of the deque, |
| 811 |
|
* followed by all of its elements (each an object reference) in |
| 812 |
|
* first-to-last order. |
| 813 |
|
*/ |
| 814 |
< |
private void writeObject(ObjectOutputStream s) throws IOException { |
| 814 |
> |
private void writeObject(java.io.ObjectOutputStream s) |
| 815 |
> |
throws java.io.IOException { |
| 816 |
|
s.defaultWriteObject(); |
| 817 |
|
|
| 818 |
|
// Write out size |
| 825 |
|
} |
| 826 |
|
|
| 827 |
|
/** |
| 828 |
< |
* Deserialize this deque. |
| 828 |
> |
* Reconstitutes this deque from a stream (that is, deserializes it). |
| 829 |
> |
* @param s the stream |
| 830 |
> |
* @throws ClassNotFoundException if the class of a serialized object |
| 831 |
> |
* could not be found |
| 832 |
> |
* @throws java.io.IOException if an I/O error occurs |
| 833 |
|
*/ |
| 834 |
< |
private void readObject(ObjectInputStream s) |
| 835 |
< |
throws IOException, ClassNotFoundException { |
| 834 |
> |
private void readObject(java.io.ObjectInputStream s) |
| 835 |
> |
throws java.io.IOException, ClassNotFoundException { |
| 836 |
|
s.defaultReadObject(); |
| 837 |
|
|
| 838 |
|
// Read in size and allocate array |
| 843 |
|
|
| 844 |
|
// Read in all elements in the proper order. |
| 845 |
|
for (int i = 0; i < size; i++) |
| 846 |
< |
elements[i] = (E)s.readObject(); |
| 846 |
> |
elements[i] = s.readObject(); |
| 847 |
> |
} |
| 848 |
|
|
| 849 |
+ |
public Spliterator<E> spliterator() { |
| 850 |
+ |
return new DeqSpliterator<E>(this, -1, -1); |
| 851 |
|
} |
| 852 |
+ |
|
| 853 |
+ |
static final class DeqSpliterator<E> implements Spliterator<E> { |
| 854 |
+ |
private final ArrayDeque<E> deq; |
| 855 |
+ |
private int fence; // -1 until first use |
| 856 |
+ |
private int index; // current index, modified on traverse/split |
| 857 |
+ |
|
| 858 |
+ |
/** Creates new spliterator covering the given array and range */ |
| 859 |
+ |
DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) { |
| 860 |
+ |
this.deq = deq; |
| 861 |
+ |
this.index = origin; |
| 862 |
+ |
this.fence = fence; |
| 863 |
+ |
} |
| 864 |
+ |
|
| 865 |
+ |
private int getFence() { // force initialization |
| 866 |
+ |
int t; |
| 867 |
+ |
if ((t = fence) < 0) { |
| 868 |
+ |
t = fence = deq.tail; |
| 869 |
+ |
index = deq.head; |
| 870 |
+ |
} |
| 871 |
+ |
return t; |
| 872 |
+ |
} |
| 873 |
+ |
|
| 874 |
+ |
public Spliterator<E> trySplit() { |
| 875 |
+ |
int t = getFence(), h = index, n = deq.elements.length; |
| 876 |
+ |
if (h != t && ((h + 1) & (n - 1)) != t) { |
| 877 |
+ |
if (h > t) |
| 878 |
+ |
t += n; |
| 879 |
+ |
int m = ((h + t) >>> 1) & (n - 1); |
| 880 |
+ |
return new DeqSpliterator<>(deq, h, index = m); |
| 881 |
+ |
} |
| 882 |
+ |
return null; |
| 883 |
+ |
} |
| 884 |
+ |
|
| 885 |
+ |
public void forEachRemaining(Consumer<? super E> consumer) { |
| 886 |
+ |
if (consumer == null) |
| 887 |
+ |
throw new NullPointerException(); |
| 888 |
+ |
Object[] a = deq.elements; |
| 889 |
+ |
int m = a.length - 1, f = getFence(), i = index; |
| 890 |
+ |
index = f; |
| 891 |
+ |
while (i != f) { |
| 892 |
+ |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
| 893 |
+ |
i = (i + 1) & m; |
| 894 |
+ |
if (e == null) |
| 895 |
+ |
throw new ConcurrentModificationException(); |
| 896 |
+ |
consumer.accept(e); |
| 897 |
+ |
} |
| 898 |
+ |
} |
| 899 |
+ |
|
| 900 |
+ |
public boolean tryAdvance(Consumer<? super E> consumer) { |
| 901 |
+ |
if (consumer == null) |
| 902 |
+ |
throw new NullPointerException(); |
| 903 |
+ |
Object[] a = deq.elements; |
| 904 |
+ |
int m = a.length - 1, f = getFence(), i = index; |
| 905 |
+ |
if (i != fence) { |
| 906 |
+ |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
| 907 |
+ |
index = (i + 1) & m; |
| 908 |
+ |
if (e == null) |
| 909 |
+ |
throw new ConcurrentModificationException(); |
| 910 |
+ |
consumer.accept(e); |
| 911 |
+ |
return true; |
| 912 |
+ |
} |
| 913 |
+ |
return false; |
| 914 |
+ |
} |
| 915 |
+ |
|
| 916 |
+ |
public long estimateSize() { |
| 917 |
+ |
int n = getFence() - index; |
| 918 |
+ |
if (n < 0) |
| 919 |
+ |
n += deq.elements.length; |
| 920 |
+ |
return (long) n; |
| 921 |
+ |
} |
| 922 |
+ |
|
| 923 |
+ |
@Override |
| 924 |
+ |
public int characteristics() { |
| 925 |
+ |
return Spliterator.ORDERED | Spliterator.SIZED | |
| 926 |
+ |
Spliterator.NONNULL | Spliterator.SUBSIZED; |
| 927 |
+ |
} |
| 928 |
+ |
} |
| 929 |
+ |
|
| 930 |
|
} |
