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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.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.function.Predicate; |
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import java.util.function.UnaryOperator; |
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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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* <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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* @param <E> the type of elements held in this deque |
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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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* We guarantee that all array cells not holding deque elements |
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* are always null. |
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*/ |
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private transient E[] elements; |
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transient Object[] elements; |
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|
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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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/** |
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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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/** |
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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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* arbitrary number 0 <= head < elements.length if the deque is empty. |
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*/ |
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private static final int MIN_INITIAL_CAPACITY = 8; |
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transient int head; |
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|
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// ****** Array allocation and resizing utilities ****** |
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/** Number of elements in this collection. */ |
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transient int size; |
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|
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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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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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* The maximum size of array to allocate. |
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* Some VMs reserve some header words in an array. |
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* Attempts to allocate larger arrays may result in |
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* OutOfMemoryError: Requested array size exceeds VM limit |
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*/ |
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private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
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|
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/** |
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* Increases the capacity of this deque by at least the given amount. |
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* |
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* @param needed the required minimum extra capacity; must be positive |
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*/ |
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private void grow(int needed) { |
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// overflow-conscious code |
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// checkInvariants(); |
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int oldCapacity = elements.length; |
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int newCapacity; |
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// Double size if small; else grow by 50% |
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int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1); |
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if (jump < needed |
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|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0) |
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newCapacity = newCapacity(needed, jump); |
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elements = Arrays.copyOf(elements, newCapacity); |
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if (oldCapacity - head < size) { |
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// wrap around; slide first leg forward to end of array |
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int newSpace = newCapacity - oldCapacity; |
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System.arraycopy(elements, head, |
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elements, head + newSpace, |
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oldCapacity - head); |
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Arrays.fill(elements, head, head + newSpace, null); |
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head += newSpace; |
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} |
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// checkInvariants(); |
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} |
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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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/** Capacity calculation for edge conditions, especially overflow. */ |
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private int newCapacity(int needed, int jump) { |
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int oldCapacity = elements.length; |
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int minCapacity; |
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if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) { |
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if (minCapacity < 0) |
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throw new IllegalStateException("Sorry, deque too big"); |
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return Integer.MAX_VALUE; |
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} |
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elements = (E[]) new Object[initialCapacity]; |
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if (needed > jump) |
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return minCapacity; |
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return (oldCapacity + jump - MAX_ARRAY_SIZE < 0) |
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? oldCapacity + jump |
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: MAX_ARRAY_SIZE; |
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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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* Increases the internal storage of this collection, if necessary, |
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* to ensure that it can hold at least the given number of elements. |
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* |
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* @param minCapacity the desired minimum capacity |
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* @since 9 |
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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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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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head = 0; |
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tail = n; |
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public void ensureCapacity(int minCapacity) { |
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if (minCapacity > elements.length) |
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grow(minCapacity - elements.length); |
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// checkInvariants(); |
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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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* Minimizes the internal storage of this collection. |
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* |
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* @return its argument |
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* @since 9 |
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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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public void trimToSize() { |
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if (size < elements.length) { |
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elements = toArray(); |
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head = 0; |
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} |
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return a; |
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// checkInvariants(); |
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} |
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|
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/** |
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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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/** |
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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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* @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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elements = new Object[numElements]; |
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} |
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|
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/** |
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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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Object[] elements = c.toArray(); |
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// defend against c.toArray (incorrectly) not returning Object[] |
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// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652) |
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if (elements.getClass() != Object[].class) |
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elements = Arrays.copyOf(elements, size, Object[].class); |
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for (Object obj : elements) |
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Objects.requireNonNull(obj); |
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size = elements.length; |
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this.elements = elements; |
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} |
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|
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/** |
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* Returns the array index of the last element. |
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* May return invalid index -1 if there are no elements. |
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*/ |
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final int tail() { |
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return add(head, size - 1, elements.length); |
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} |
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|
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/** |
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* Adds i and j, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus. |
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*/ |
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static final int add(int i, int j, int modulus) { |
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if ((i += j) - modulus >= 0) i -= modulus; |
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return i; |
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} |
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|
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/** |
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* Increments i, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus. |
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*/ |
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static final int inc(int i, int modulus) { |
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if (++i == modulus) i = 0; |
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return i; |
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} |
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|
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/** |
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* Decrements i, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus. |
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*/ |
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static final int dec(int i, int modulus) { |
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if (--i < 0) i += modulus; |
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return i; |
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} |
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|
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/** |
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* Returns element at array index i. |
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*/ |
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@SuppressWarnings("unchecked") |
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final E elementAt(int i) { |
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return (E) elements[i]; |
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} |
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|
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/** |
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* A version of elementAt that checks for null elements. |
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* This check doesn't catch all possible comodifications, |
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* but does catch ones that corrupt traversal. |
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*/ |
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E checkedElementAt(Object[] elements, int i) { |
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@SuppressWarnings("unchecked") E e = (E) elements[i]; |
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if (e == null) |
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throw new ConcurrentModificationException(); |
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return e; |
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} |
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|
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// The main insertion and extraction methods are addFirst, |
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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(); |
266 |
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elements[head = (head - 1) & (elements.length - 1)] = e; |
267 |
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if (head == tail) |
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doubleCapacity(); |
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// checkInvariants(); |
265 |
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Objects.requireNonNull(e); |
266 |
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Object[] elements; |
267 |
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int capacity, s = size; |
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while (s == (capacity = (elements = this.elements).length)) |
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grow(1); |
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elements[head = dec(head, capacity)] = e; |
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size = s + 1; |
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} |
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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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* This method is equivalent to {@link #add} and {@link #push}. |
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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 |
280 |
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* @throws NullPointerException if the specified element is null |
281 |
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*/ |
282 |
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public void addLast(E e) { |
283 |
< |
if (e == null) |
284 |
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throw new NullPointerException(); |
285 |
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elements[tail] = e; |
286 |
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if ( (tail = (tail + 1) & (elements.length - 1)) == head) |
287 |
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doubleCapacity(); |
283 |
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// checkInvariants(); |
284 |
> |
Objects.requireNonNull(e); |
285 |
> |
Object[] elements; |
286 |
> |
int capacity, s = size; |
287 |
> |
while (s == (capacity = (elements = this.elements).length)) |
288 |
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grow(1); |
289 |
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elements[add(head, s, capacity)] = e; |
290 |
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size = s + 1; |
291 |
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} |
292 |
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|
293 |
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/** |
294 |
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* Adds all of the elements in the specified collection at the end |
295 |
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* of this deque, as if by calling {@link #addLast} on each one, |
296 |
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* in the order that they are returned by the collection's |
297 |
> |
* iterator. |
298 |
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* |
299 |
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* @param c the elements to be inserted into this deque |
300 |
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* @return {@code true} if this deque changed as a result of the call |
301 |
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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
303 |
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*/ |
304 |
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@Override |
305 |
> |
public boolean addAll(Collection<? extends E> c) { |
306 |
> |
// checkInvariants(); |
307 |
> |
Object[] a, elements; |
308 |
> |
int len, capacity, s = size; |
309 |
> |
if ((len = (a = c.toArray()).length) == 0) |
310 |
> |
return false; |
311 |
> |
while ((capacity = (elements = this.elements).length) - s < len) |
312 |
> |
grow(len - (capacity - s)); |
313 |
> |
int i = add(head, s, capacity); |
314 |
> |
for (Object x : a) { |
315 |
> |
Objects.requireNonNull(x); |
316 |
> |
elements[i] = x; |
317 |
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i = inc(i, capacity); |
318 |
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size++; |
319 |
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} |
320 |
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return true; |
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} |
322 |
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|
323 |
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/** |
324 |
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* Inserts the specified element at the front of this deque. |
325 |
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* |
326 |
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* @param e the element to add |
327 |
< |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
327 |
> |
* @return {@code true} (as specified by {@link Deque#offerFirst}) |
328 |
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* @throws NullPointerException if the specified element is null |
329 |
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*/ |
330 |
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public boolean offerFirst(E e) { |
336 |
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* Inserts the specified element at the end of this deque. |
337 |
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* |
338 |
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* @param e the element to add |
339 |
< |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
339 |
> |
* @return {@code true} (as specified by {@link Deque#offerLast}) |
340 |
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* @throws NullPointerException if the specified element is null |
341 |
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*/ |
342 |
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public boolean offerLast(E e) { |
348 |
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* @throws NoSuchElementException {@inheritDoc} |
349 |
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*/ |
350 |
|
public E removeFirst() { |
351 |
+ |
// checkInvariants(); |
352 |
|
E x = pollFirst(); |
353 |
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if (x == null) |
354 |
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throw new NoSuchElementException(); |
359 |
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* @throws NoSuchElementException {@inheritDoc} |
360 |
|
*/ |
361 |
|
public E removeLast() { |
362 |
+ |
// checkInvariants(); |
363 |
|
E x = pollLast(); |
364 |
|
if (x == null) |
365 |
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throw new NoSuchElementException(); |
367 |
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} |
368 |
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|
369 |
|
public E pollFirst() { |
370 |
< |
int h = head; |
371 |
< |
E result = elements[h]; // Element is null if deque empty |
372 |
< |
if (result == null) |
370 |
> |
// checkInvariants(); |
371 |
> |
final int s, h; |
372 |
> |
if ((s = size) == 0) |
373 |
|
return null; |
374 |
< |
elements[h] = null; // Must null out slot |
375 |
< |
head = (h + 1) & (elements.length - 1); |
376 |
< |
return result; |
374 |
> |
final Object[] elements = this.elements; |
375 |
> |
@SuppressWarnings("unchecked") E e = (E) elements[h = head]; |
376 |
> |
elements[h] = null; |
377 |
> |
head = inc(h, elements.length); |
378 |
> |
size = s - 1; |
379 |
> |
return e; |
380 |
|
} |
381 |
|
|
382 |
|
public E pollLast() { |
383 |
< |
int t = (tail - 1) & (elements.length - 1); |
384 |
< |
E result = elements[t]; |
385 |
< |
if (result == null) |
383 |
> |
// checkInvariants(); |
384 |
> |
final int s, tail; |
385 |
> |
if ((s = size) == 0) |
386 |
|
return null; |
387 |
< |
elements[t] = null; |
388 |
< |
tail = t; |
389 |
< |
return result; |
387 |
> |
final Object[] elements = this.elements; |
388 |
> |
@SuppressWarnings("unchecked") |
389 |
> |
E e = (E) elements[tail = add(head, s - 1, elements.length)]; |
390 |
> |
elements[tail] = null; |
391 |
> |
size = s - 1; |
392 |
> |
return e; |
393 |
|
} |
394 |
|
|
395 |
|
/** |
396 |
|
* @throws NoSuchElementException {@inheritDoc} |
397 |
|
*/ |
398 |
|
public E getFirst() { |
399 |
< |
E x = elements[head]; |
400 |
< |
if (x == null) |
401 |
< |
throw new NoSuchElementException(); |
289 |
< |
return x; |
399 |
> |
// checkInvariants(); |
400 |
> |
if (size == 0) throw new NoSuchElementException(); |
401 |
> |
return elementAt(head); |
402 |
|
} |
403 |
|
|
404 |
|
/** |
405 |
|
* @throws NoSuchElementException {@inheritDoc} |
406 |
|
*/ |
407 |
|
public E getLast() { |
408 |
< |
E x = elements[(tail - 1) & (elements.length - 1)]; |
409 |
< |
if (x == null) |
410 |
< |
throw new NoSuchElementException(); |
299 |
< |
return x; |
408 |
> |
// checkInvariants(); |
409 |
> |
if (size == 0) throw new NoSuchElementException(); |
410 |
> |
return elementAt(tail()); |
411 |
|
} |
412 |
|
|
413 |
|
public E peekFirst() { |
414 |
< |
return elements[head]; // elements[head] is null if deque empty |
414 |
> |
// checkInvariants(); |
415 |
> |
return (size == 0) ? null : elementAt(head); |
416 |
|
} |
417 |
|
|
418 |
|
public E peekLast() { |
419 |
< |
return elements[(tail - 1) & (elements.length - 1)]; |
419 |
> |
// checkInvariants(); |
420 |
> |
return (size == 0) ? null : elementAt(tail()); |
421 |
|
} |
422 |
|
|
423 |
|
/** |
424 |
|
* Removes the first occurrence of the specified element in this |
425 |
|
* deque (when traversing the deque from head to tail). |
426 |
|
* If the deque does not contain the element, it is unchanged. |
427 |
< |
* More formally, removes the first element <tt>e</tt> such that |
428 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
429 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
427 |
> |
* More formally, removes the first element {@code e} such that |
428 |
> |
* {@code o.equals(e)} (if such an element exists). |
429 |
> |
* Returns {@code true} if this deque contained the specified element |
430 |
|
* (or equivalently, if this deque changed as a result of the call). |
431 |
|
* |
432 |
|
* @param o element to be removed from this deque, if present |
433 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
433 |
> |
* @return {@code true} if the deque contained the specified element |
434 |
|
*/ |
435 |
|
public boolean removeFirstOccurrence(Object o) { |
436 |
< |
if (o == null) |
437 |
< |
return false; |
438 |
< |
int mask = elements.length - 1; |
439 |
< |
int i = head; |
440 |
< |
E x; |
441 |
< |
while ( (x = elements[i]) != null) { |
442 |
< |
if (o.equals(x)) { |
443 |
< |
delete(i); |
444 |
< |
return true; |
436 |
> |
// checkInvariants(); |
437 |
> |
if (o != null) { |
438 |
> |
final Object[] elements = this.elements; |
439 |
> |
final int capacity = elements.length; |
440 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) { |
441 |
> |
if (o.equals(elements[i])) { |
442 |
> |
delete(i); |
443 |
> |
return true; |
444 |
> |
} |
445 |
|
} |
333 |
– |
i = (i + 1) & mask; |
446 |
|
} |
447 |
|
return false; |
448 |
|
} |
451 |
|
* Removes the last occurrence of the specified element in this |
452 |
|
* deque (when traversing the deque from head to tail). |
453 |
|
* If the deque does not contain the element, it is unchanged. |
454 |
< |
* More formally, removes the last element <tt>e</tt> such that |
455 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
456 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
454 |
> |
* More formally, removes the last element {@code e} such that |
455 |
> |
* {@code o.equals(e)} (if such an element exists). |
456 |
> |
* Returns {@code true} if this deque contained the specified element |
457 |
|
* (or equivalently, if this deque changed as a result of the call). |
458 |
|
* |
459 |
|
* @param o element to be removed from this deque, if present |
460 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
460 |
> |
* @return {@code true} if the deque contained the specified element |
461 |
|
*/ |
462 |
|
public boolean removeLastOccurrence(Object o) { |
463 |
< |
if (o == null) |
464 |
< |
return false; |
465 |
< |
int mask = elements.length - 1; |
466 |
< |
int i = (tail - 1) & mask; |
467 |
< |
E x; |
468 |
< |
while ( (x = elements[i]) != null) { |
469 |
< |
if (o.equals(x)) { |
470 |
< |
delete(i); |
471 |
< |
return true; |
463 |
> |
if (o != null) { |
464 |
> |
final Object[] elements = this.elements; |
465 |
> |
final int capacity = elements.length; |
466 |
> |
for (int k = size, i = add(head, k - 1, capacity); |
467 |
> |
--k >= 0; i = dec(i, capacity)) { |
468 |
> |
if (o.equals(elements[i])) { |
469 |
> |
delete(i); |
470 |
> |
return true; |
471 |
> |
} |
472 |
|
} |
361 |
– |
i = (i - 1) & mask; |
473 |
|
} |
474 |
|
return false; |
475 |
|
} |
482 |
|
* <p>This method is equivalent to {@link #addLast}. |
483 |
|
* |
484 |
|
* @param e the element to add |
485 |
< |
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
485 |
> |
* @return {@code true} (as specified by {@link Collection#add}) |
486 |
|
* @throws NullPointerException if the specified element is null |
487 |
|
*/ |
488 |
|
public boolean add(E e) { |
496 |
|
* <p>This method is equivalent to {@link #offerLast}. |
497 |
|
* |
498 |
|
* @param e the element to add |
499 |
< |
* @return <tt>true</tt> (as per the spec for {@link Queue#offer}) |
499 |
> |
* @return {@code true} (as specified by {@link Queue#offer}) |
500 |
|
* @throws NullPointerException if the specified element is null |
501 |
|
*/ |
502 |
|
public boolean offer(E e) { |
505 |
|
|
506 |
|
/** |
507 |
|
* Retrieves and removes the head of the queue represented by this deque. |
508 |
< |
* This method differs from {@link #poll} only in that it throws an |
508 |
> |
* |
509 |
> |
* This method differs from {@link #poll poll} only in that it throws an |
510 |
|
* exception if this deque is empty. |
511 |
|
* |
512 |
|
* <p>This method is equivalent to {@link #removeFirst}. |
521 |
|
/** |
522 |
|
* Retrieves and removes the head of the queue represented by this deque |
523 |
|
* (in other words, the first element of this deque), or returns |
524 |
< |
* <tt>null</tt> if this deque is empty. |
524 |
> |
* {@code null} if this deque is empty. |
525 |
|
* |
526 |
|
* <p>This method is equivalent to {@link #pollFirst}. |
527 |
|
* |
528 |
|
* @return the head of the queue represented by this deque, or |
529 |
< |
* <tt>null</tt> if this deque is empty |
529 |
> |
* {@code null} if this deque is empty |
530 |
|
*/ |
531 |
|
public E poll() { |
532 |
|
return pollFirst(); |
534 |
|
|
535 |
|
/** |
536 |
|
* Retrieves, but does not remove, the head of the queue represented by |
537 |
< |
* this deque. This method differs from {@link #peek} only in that it |
538 |
< |
* throws an exception if this deque is empty. |
537 |
> |
* this deque. This method differs from {@link #peek peek} only in |
538 |
> |
* that it throws an exception if this deque is empty. |
539 |
|
* |
540 |
|
* <p>This method is equivalent to {@link #getFirst}. |
541 |
|
* |
548 |
|
|
549 |
|
/** |
550 |
|
* Retrieves, but does not remove, the head of the queue represented by |
551 |
< |
* this deque, or returns <tt>null</tt> if this deque is empty. |
551 |
> |
* this deque, or returns {@code null} if this deque is empty. |
552 |
|
* |
553 |
|
* <p>This method is equivalent to {@link #peekFirst}. |
554 |
|
* |
555 |
|
* @return the head of the queue represented by this deque, or |
556 |
< |
* <tt>null</tt> if this deque is empty |
556 |
> |
* {@code null} if this deque is empty |
557 |
|
*/ |
558 |
|
public E peek() { |
559 |
|
return peekFirst(); |
589 |
|
} |
590 |
|
|
591 |
|
/** |
592 |
< |
* Removes the element at the specified position in the elements array, |
593 |
< |
* adjusting head and tail as necessary. This can result in motion of |
594 |
< |
* elements backwards or forwards in the array. |
592 |
> |
* Removes the element at the specified position in the elements array. |
593 |
> |
* This can result in forward or backwards motion of array elements. |
594 |
> |
* We optimize for least element motion. |
595 |
|
* |
596 |
|
* <p>This method is called delete rather than remove to emphasize |
597 |
|
* that its semantics differ from those of {@link List#remove(int)}. |
598 |
|
* |
599 |
|
* @return true if elements moved backwards |
600 |
|
*/ |
601 |
< |
private boolean delete(int i) { |
602 |
< |
int mask = elements.length - 1; |
603 |
< |
|
604 |
< |
// Invariant: head <= i < tail mod circularity |
605 |
< |
if (((i - head) & mask) >= ((tail - head) & mask)) |
606 |
< |
throw new ConcurrentModificationException(); |
607 |
< |
|
608 |
< |
// Case 1: Deque doesn't wrap |
609 |
< |
// Case 2: Deque does wrap and removed element is in the head portion |
610 |
< |
if (i >= head) { |
611 |
< |
System.arraycopy(elements, head, elements, head + 1, i - head); |
612 |
< |
elements[head] = null; |
613 |
< |
head = (head + 1) & mask; |
601 |
> |
boolean delete(int i) { |
602 |
> |
// checkInvariants(); |
603 |
> |
final Object[] elements = this.elements; |
604 |
> |
final int capacity = elements.length; |
605 |
> |
final int h = head; |
606 |
> |
int front; // number of elements before to-be-deleted elt |
607 |
> |
if ((front = i - h) < 0) front += capacity; |
608 |
> |
final int back = size - front - 1; // number of elements after |
609 |
> |
if (front < back) { |
610 |
> |
// move front elements forwards |
611 |
> |
if (h <= i) { |
612 |
> |
System.arraycopy(elements, h, elements, h + 1, front); |
613 |
> |
} else { // Wrap around |
614 |
> |
System.arraycopy(elements, 0, elements, 1, i); |
615 |
> |
elements[0] = elements[capacity - 1]; |
616 |
> |
System.arraycopy(elements, h, elements, h + 1, front - (i + 1)); |
617 |
> |
} |
618 |
> |
elements[h] = null; |
619 |
> |
head = inc(h, capacity); |
620 |
> |
size--; |
621 |
> |
// checkInvariants(); |
622 |
|
return false; |
623 |
+ |
} else { |
624 |
+ |
// move back elements backwards |
625 |
+ |
int tail = tail(); |
626 |
+ |
if (i <= tail) { |
627 |
+ |
System.arraycopy(elements, i + 1, elements, i, back); |
628 |
+ |
} else { // Wrap around |
629 |
+ |
int firstLeg = capacity - (i + 1); |
630 |
+ |
System.arraycopy(elements, i + 1, elements, i, firstLeg); |
631 |
+ |
elements[capacity - 1] = elements[0]; |
632 |
+ |
System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1); |
633 |
+ |
} |
634 |
+ |
elements[tail] = null; |
635 |
+ |
size--; |
636 |
+ |
// checkInvariants(); |
637 |
+ |
return true; |
638 |
|
} |
504 |
– |
|
505 |
– |
// Case 3: Deque wraps and removed element is in the tail portion |
506 |
– |
tail--; |
507 |
– |
System.arraycopy(elements, i + 1, elements, i, tail - i); |
508 |
– |
elements[tail] = null; |
509 |
– |
return true; |
639 |
|
} |
640 |
|
|
641 |
|
// *** Collection Methods *** |
646 |
|
* @return the number of elements in this deque |
647 |
|
*/ |
648 |
|
public int size() { |
649 |
< |
return (tail - head) & (elements.length - 1); |
649 |
> |
return size; |
650 |
|
} |
651 |
|
|
652 |
|
/** |
653 |
< |
* Returns <tt>true</tt> if this deque contains no elements. |
653 |
> |
* Returns {@code true} if this deque contains no elements. |
654 |
|
* |
655 |
< |
* @return <tt>true</tt> if this deque contains no elements |
655 |
> |
* @return {@code true} if this deque contains no elements |
656 |
|
*/ |
657 |
|
public boolean isEmpty() { |
658 |
< |
return head == tail; |
658 |
> |
return size == 0; |
659 |
|
} |
660 |
|
|
661 |
|
/** |
664 |
|
* order that elements would be dequeued (via successive calls to |
665 |
|
* {@link #remove} or popped (via successive calls to {@link #pop}). |
666 |
|
* |
667 |
< |
* @return an <tt>Iterator</tt> over the elements in this deque |
667 |
> |
* @return an iterator over the elements in this deque |
668 |
|
*/ |
669 |
|
public Iterator<E> iterator() { |
670 |
|
return new DeqIterator(); |
671 |
|
} |
672 |
|
|
673 |
+ |
public Iterator<E> descendingIterator() { |
674 |
+ |
return new DescendingIterator(); |
675 |
+ |
} |
676 |
+ |
|
677 |
|
private class DeqIterator implements Iterator<E> { |
678 |
< |
/** |
679 |
< |
* Index of element to be returned by subsequent call to next. |
547 |
< |
*/ |
548 |
< |
private int cursor = head; |
678 |
> |
/** Index of element to be returned by subsequent call to next. */ |
679 |
> |
int cursor; |
680 |
|
|
681 |
< |
/** |
682 |
< |
* Tail recorded at construction (also in remove), to stop |
552 |
< |
* iterator and also to check for comodification. |
553 |
< |
*/ |
554 |
< |
private int fence = tail; |
681 |
> |
/** Number of elements yet to be returned. */ |
682 |
> |
int remaining = size; |
683 |
|
|
684 |
|
/** |
685 |
|
* Index of element returned by most recent call to next. |
686 |
|
* Reset to -1 if element is deleted by a call to remove. |
687 |
|
*/ |
688 |
< |
private int lastRet = -1; |
688 |
> |
int lastRet = -1; |
689 |
> |
|
690 |
> |
DeqIterator() { cursor = head; } |
691 |
|
|
692 |
< |
public boolean hasNext() { |
693 |
< |
return cursor != fence; |
692 |
> |
int advance(int i, int modulus) { |
693 |
> |
return inc(i, modulus); |
694 |
|
} |
695 |
|
|
696 |
< |
public E next() { |
697 |
< |
E result; |
698 |
< |
if (cursor == fence) |
696 |
> |
void doRemove() { |
697 |
> |
if (delete(lastRet)) |
698 |
> |
// if left-shifted, undo advance in next() |
699 |
> |
cursor = dec(cursor, elements.length); |
700 |
> |
} |
701 |
> |
|
702 |
> |
public final boolean hasNext() { |
703 |
> |
return remaining > 0; |
704 |
> |
} |
705 |
> |
|
706 |
> |
public final E next() { |
707 |
> |
if (remaining == 0) |
708 |
|
throw new NoSuchElementException(); |
709 |
< |
// This check doesn't catch all possible comodifications, |
571 |
< |
// but does catch the ones that corrupt traversal |
572 |
< |
if (tail != fence || (result = elements[cursor]) == null) |
573 |
< |
throw new ConcurrentModificationException(); |
709 |
> |
E e = checkedElementAt(elements, cursor); |
710 |
|
lastRet = cursor; |
711 |
< |
cursor = (cursor + 1) & (elements.length - 1); |
712 |
< |
return result; |
711 |
> |
cursor = advance(cursor, elements.length); |
712 |
> |
remaining--; |
713 |
> |
return e; |
714 |
|
} |
715 |
|
|
716 |
< |
public void remove() { |
716 |
> |
public final void remove() { |
717 |
|
if (lastRet < 0) |
718 |
|
throw new IllegalStateException(); |
719 |
< |
if (delete(lastRet)) |
583 |
< |
cursor--; |
719 |
> |
doRemove(); |
720 |
|
lastRet = -1; |
721 |
< |
fence = tail; |
721 |
> |
} |
722 |
> |
|
723 |
> |
public final void forEachRemaining(Consumer<? super E> action) { |
724 |
> |
Objects.requireNonNull(action); |
725 |
> |
final Object[] elements = ArrayDeque.this.elements; |
726 |
> |
final int capacity = elements.length; |
727 |
> |
int k = remaining; |
728 |
> |
remaining = 0; |
729 |
> |
for (int i = cursor; --k >= 0; i = advance(i, capacity)) |
730 |
> |
action.accept(checkedElementAt(elements, i)); |
731 |
> |
} |
732 |
> |
} |
733 |
> |
|
734 |
> |
private class DescendingIterator extends DeqIterator { |
735 |
> |
DescendingIterator() { cursor = tail(); } |
736 |
> |
|
737 |
> |
@Override int advance(int i, int modulus) { |
738 |
> |
return dec(i, modulus); |
739 |
> |
} |
740 |
> |
|
741 |
> |
@Override void doRemove() { |
742 |
> |
if (!delete(lastRet)) |
743 |
> |
// if right-shifted, undo advance in next |
744 |
> |
cursor = inc(cursor, elements.length); |
745 |
|
} |
746 |
|
} |
747 |
|
|
748 |
|
/** |
749 |
< |
* Returns <tt>true</tt> if this deque contains the specified element. |
750 |
< |
* More formally, returns <tt>true</tt> if and only if this deque contains |
751 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
749 |
> |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
750 |
> |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
751 |
> |
* deque. |
752 |
> |
* |
753 |
> |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
754 |
> |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
755 |
> |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
756 |
> |
* the reporting of additional characteristic values. |
757 |
> |
* |
758 |
> |
* @return a {@code Spliterator} over the elements in this deque |
759 |
> |
* @since 1.8 |
760 |
> |
*/ |
761 |
> |
public Spliterator<E> spliterator() { |
762 |
> |
return new ArrayDequeSpliterator(); |
763 |
> |
} |
764 |
> |
|
765 |
> |
final class ArrayDequeSpliterator implements Spliterator<E> { |
766 |
> |
private int cursor; |
767 |
> |
private int remaining; // -1 until late-binding first use |
768 |
> |
|
769 |
> |
/** Constructs late-binding spliterator over all elements. */ |
770 |
> |
ArrayDequeSpliterator() { |
771 |
> |
this.remaining = -1; |
772 |
> |
} |
773 |
> |
|
774 |
> |
/** Constructs spliterator over the given slice. */ |
775 |
> |
ArrayDequeSpliterator(int cursor, int count) { |
776 |
> |
this.cursor = cursor; |
777 |
> |
this.remaining = count; |
778 |
> |
} |
779 |
> |
|
780 |
> |
/** Ensures late-binding initialization; then returns remaining. */ |
781 |
> |
private int remaining() { |
782 |
> |
if (remaining < 0) { |
783 |
> |
cursor = head; |
784 |
> |
remaining = size; |
785 |
> |
} |
786 |
> |
return remaining; |
787 |
> |
} |
788 |
> |
|
789 |
> |
public ArrayDequeSpliterator trySplit() { |
790 |
> |
final int mid; |
791 |
> |
if ((mid = remaining() >> 1) > 0) { |
792 |
> |
int oldCursor = cursor; |
793 |
> |
cursor = add(cursor, mid, elements.length); |
794 |
> |
remaining -= mid; |
795 |
> |
return new ArrayDequeSpliterator(oldCursor, mid); |
796 |
> |
} |
797 |
> |
return null; |
798 |
> |
} |
799 |
> |
|
800 |
> |
public void forEachRemaining(Consumer<? super E> action) { |
801 |
> |
Objects.requireNonNull(action); |
802 |
> |
final Object[] elements = ArrayDeque.this.elements; |
803 |
> |
final int capacity = elements.length; |
804 |
> |
int k = remaining(); |
805 |
> |
remaining = 0; |
806 |
> |
for (int i = cursor; --k >= 0; i = inc(i, capacity)) |
807 |
> |
action.accept(checkedElementAt(elements, i)); |
808 |
> |
} |
809 |
> |
|
810 |
> |
public boolean tryAdvance(Consumer<? super E> action) { |
811 |
> |
Objects.requireNonNull(action); |
812 |
> |
if (remaining() == 0) |
813 |
> |
return false; |
814 |
> |
action.accept(checkedElementAt(elements, cursor)); |
815 |
> |
cursor = inc(cursor, elements.length); |
816 |
> |
remaining--; |
817 |
> |
return true; |
818 |
> |
} |
819 |
> |
|
820 |
> |
public long estimateSize() { |
821 |
> |
return remaining(); |
822 |
> |
} |
823 |
> |
|
824 |
> |
public int characteristics() { |
825 |
> |
return Spliterator.NONNULL |
826 |
> |
| Spliterator.ORDERED |
827 |
> |
| Spliterator.SIZED |
828 |
> |
| Spliterator.SUBSIZED; |
829 |
> |
} |
830 |
> |
} |
831 |
> |
|
832 |
> |
@Override |
833 |
> |
public void forEach(Consumer<? super E> action) { |
834 |
> |
// checkInvariants(); |
835 |
> |
Objects.requireNonNull(action); |
836 |
> |
final Object[] elements = this.elements; |
837 |
> |
final int capacity = elements.length; |
838 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
839 |
> |
action.accept(elementAt(i)); |
840 |
> |
// checkInvariants(); |
841 |
> |
} |
842 |
> |
|
843 |
> |
/** |
844 |
> |
* Replaces each element of this deque with the result of applying the |
845 |
> |
* operator to that element, as specified by {@link List#replaceAll}. |
846 |
> |
* |
847 |
> |
* @param operator the operator to apply to each element |
848 |
> |
* @since 9 |
849 |
> |
*/ |
850 |
> |
public void replaceAll(UnaryOperator<E> operator) { |
851 |
> |
Objects.requireNonNull(operator); |
852 |
> |
final Object[] elements = this.elements; |
853 |
> |
final int capacity = elements.length; |
854 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
855 |
> |
elements[i] = operator.apply(elementAt(i)); |
856 |
> |
// checkInvariants(); |
857 |
> |
} |
858 |
> |
|
859 |
> |
/** |
860 |
> |
* @throws NullPointerException {@inheritDoc} |
861 |
> |
*/ |
862 |
> |
@Override |
863 |
> |
public boolean removeIf(Predicate<? super E> filter) { |
864 |
> |
Objects.requireNonNull(filter); |
865 |
> |
return bulkRemove(filter); |
866 |
> |
} |
867 |
> |
|
868 |
> |
/** |
869 |
> |
* @throws NullPointerException {@inheritDoc} |
870 |
> |
*/ |
871 |
> |
@Override |
872 |
> |
public boolean removeAll(Collection<?> c) { |
873 |
> |
Objects.requireNonNull(c); |
874 |
> |
return bulkRemove(e -> c.contains(e)); |
875 |
> |
} |
876 |
> |
|
877 |
> |
/** |
878 |
> |
* @throws NullPointerException {@inheritDoc} |
879 |
> |
*/ |
880 |
> |
@Override |
881 |
> |
public boolean retainAll(Collection<?> c) { |
882 |
> |
Objects.requireNonNull(c); |
883 |
> |
return bulkRemove(e -> !c.contains(e)); |
884 |
> |
} |
885 |
> |
|
886 |
> |
/** Implementation of bulk remove methods. */ |
887 |
> |
private boolean bulkRemove(Predicate<? super E> filter) { |
888 |
> |
// checkInvariants(); |
889 |
> |
final Object[] elements = this.elements; |
890 |
> |
final int capacity = elements.length; |
891 |
> |
int i = head, j = i, remaining = size, deleted = 0; |
892 |
> |
try { |
893 |
> |
for (; remaining > 0; remaining--, i = inc(i, capacity)) { |
894 |
> |
@SuppressWarnings("unchecked") E e = (E) elements[i]; |
895 |
> |
if (filter.test(e)) |
896 |
> |
deleted++; |
897 |
> |
else { |
898 |
> |
if (j != i) |
899 |
> |
elements[j] = e; |
900 |
> |
j = inc(j, capacity); |
901 |
> |
} |
902 |
> |
} |
903 |
> |
return deleted > 0; |
904 |
> |
} catch (Throwable ex) { |
905 |
> |
for (; remaining > 0; |
906 |
> |
remaining--, i = inc(i, capacity), j = inc(j, capacity)) |
907 |
> |
elements[j] = elements[i]; |
908 |
> |
throw ex; |
909 |
> |
} finally { |
910 |
> |
size -= deleted; |
911 |
> |
for (; --deleted >= 0; j = inc(j, capacity)) |
912 |
> |
elements[j] = null; |
913 |
> |
// checkInvariants(); |
914 |
> |
} |
915 |
> |
} |
916 |
> |
|
917 |
> |
/** |
918 |
> |
* Returns {@code true} if this deque contains the specified element. |
919 |
> |
* More formally, returns {@code true} if and only if this deque contains |
920 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
921 |
|
* |
922 |
|
* @param o object to be checked for containment in this deque |
923 |
< |
* @return <tt>true</tt> if this deque contains the specified element |
923 |
> |
* @return {@code true} if this deque contains the specified element |
924 |
|
*/ |
925 |
|
public boolean contains(Object o) { |
926 |
< |
if (o == null) |
927 |
< |
return false; |
928 |
< |
int mask = elements.length - 1; |
929 |
< |
int i = head; |
930 |
< |
E x; |
931 |
< |
while ( (x = elements[i]) != null) { |
604 |
< |
if (o.equals(x)) |
605 |
< |
return true; |
606 |
< |
i = (i + 1) & mask; |
926 |
> |
if (o != null) { |
927 |
> |
final Object[] elements = this.elements; |
928 |
> |
final int capacity = elements.length; |
929 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
930 |
> |
if (o.equals(elements[i])) |
931 |
> |
return true; |
932 |
|
} |
933 |
|
return false; |
934 |
|
} |
936 |
|
/** |
937 |
|
* Removes a single instance of the specified element from this deque. |
938 |
|
* If the deque does not contain the element, it is unchanged. |
939 |
< |
* More formally, removes the first element <tt>e</tt> such that |
940 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
941 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
939 |
> |
* More formally, removes the first element {@code e} such that |
940 |
> |
* {@code o.equals(e)} (if such an element exists). |
941 |
> |
* Returns {@code true} if this deque contained the specified element |
942 |
|
* (or equivalently, if this deque changed as a result of the call). |
943 |
|
* |
944 |
< |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
944 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
945 |
|
* |
946 |
|
* @param o element to be removed from this deque, if present |
947 |
< |
* @return <tt>true</tt> if this deque contained the specified element |
947 |
> |
* @return {@code true} if this deque contained the specified element |
948 |
|
*/ |
949 |
|
public boolean remove(Object o) { |
950 |
|
return removeFirstOccurrence(o); |
955 |
|
* The deque will be empty after this call returns. |
956 |
|
*/ |
957 |
|
public void clear() { |
958 |
< |
int h = head; |
959 |
< |
int t = tail; |
960 |
< |
if (h != t) { // clear all cells |
961 |
< |
head = tail = 0; |
962 |
< |
int i = h; |
963 |
< |
int mask = elements.length - 1; |
964 |
< |
do { |
965 |
< |
elements[i] = null; |
966 |
< |
i = (i + 1) & mask; |
642 |
< |
} while (i != t); |
958 |
> |
final Object[] elements = this.elements; |
959 |
> |
final int capacity = elements.length; |
960 |
> |
final int h = this.head; |
961 |
> |
final int s = size; |
962 |
> |
if (capacity - h >= s) |
963 |
> |
Arrays.fill(elements, h, h + s, null); |
964 |
> |
else { |
965 |
> |
Arrays.fill(elements, h, capacity, null); |
966 |
> |
Arrays.fill(elements, 0, s - capacity + h, null); |
967 |
|
} |
968 |
+ |
size = head = 0; |
969 |
+ |
// checkInvariants(); |
970 |
|
} |
971 |
|
|
972 |
|
/** |
983 |
|
* @return an array containing all of the elements in this deque |
984 |
|
*/ |
985 |
|
public Object[] toArray() { |
986 |
< |
return copyElements(new Object[size()]); |
986 |
> |
final int head = this.head; |
987 |
> |
final int firstLeg; |
988 |
> |
Object[] a = Arrays.copyOfRange(elements, head, head + size); |
989 |
> |
if ((firstLeg = elements.length - head) < size) |
990 |
> |
System.arraycopy(elements, 0, a, firstLeg, size - firstLeg); |
991 |
> |
return a; |
992 |
|
} |
993 |
|
|
994 |
|
/** |
1002 |
|
* <p>If this deque fits in the specified array with room to spare |
1003 |
|
* (i.e., the array has more elements than this deque), the element in |
1004 |
|
* the array immediately following the end of the deque is set to |
1005 |
< |
* <tt>null</tt>. |
1005 |
> |
* {@code null}. |
1006 |
|
* |
1007 |
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
1008 |
|
* array-based and collection-based APIs. Further, this method allows |
1009 |
|
* precise control over the runtime type of the output array, and may, |
1010 |
|
* under certain circumstances, be used to save allocation costs. |
1011 |
|
* |
1012 |
< |
* <p>Suppose <tt>x</tt> is a deque known to contain only strings. |
1012 |
> |
* <p>Suppose {@code x} is a deque known to contain only strings. |
1013 |
|
* The following code can be used to dump the deque into a newly |
1014 |
< |
* allocated array of <tt>String</tt>: |
1014 |
> |
* allocated array of {@code String}: |
1015 |
|
* |
1016 |
< |
* <pre> |
686 |
< |
* String[] y = x.toArray(new String[0]);</pre> |
1016 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
1017 |
|
* |
1018 |
< |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
1019 |
< |
* <tt>toArray()</tt>. |
1018 |
> |
* Note that {@code toArray(new Object[0])} is identical in function to |
1019 |
> |
* {@code toArray()}. |
1020 |
|
* |
1021 |
|
* @param a the array into which the elements of the deque are to |
1022 |
|
* be stored, if it is big enough; otherwise, a new array of the |
1027 |
|
* this deque |
1028 |
|
* @throws NullPointerException if the specified array is null |
1029 |
|
*/ |
1030 |
+ |
@SuppressWarnings("unchecked") |
1031 |
|
public <T> T[] toArray(T[] a) { |
1032 |
< |
int size = size(); |
1033 |
< |
if (a.length < size) |
1034 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
1035 |
< |
a.getClass().getComponentType(), size); |
1036 |
< |
copyElements(a); |
1037 |
< |
if (a.length > size) |
1038 |
< |
a[size] = null; |
1032 |
> |
final Object[] elements = this.elements; |
1033 |
> |
final int head = this.head; |
1034 |
> |
final int firstLeg; |
1035 |
> |
boolean wrap = (firstLeg = elements.length - head) < size; |
1036 |
> |
if (size > a.length) { |
1037 |
> |
a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
1038 |
> |
a.getClass()); |
1039 |
> |
} else { |
1040 |
> |
System.arraycopy(elements, head, a, 0, wrap ? firstLeg : size); |
1041 |
> |
if (size < a.length) |
1042 |
> |
a[size] = null; |
1043 |
> |
} |
1044 |
> |
if (wrap) |
1045 |
> |
System.arraycopy(elements, 0, a, firstLeg, size - firstLeg); |
1046 |
|
return a; |
1047 |
|
} |
1048 |
|
|
1055 |
|
*/ |
1056 |
|
public ArrayDeque<E> clone() { |
1057 |
|
try { |
1058 |
+ |
@SuppressWarnings("unchecked") |
1059 |
|
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
1060 |
< |
// These two lines are currently faster than cloning the array: |
722 |
< |
result.elements = (E[]) new Object[elements.length]; |
723 |
< |
System.arraycopy(elements, 0, result.elements, 0, elements.length); |
1060 |
> |
result.elements = Arrays.copyOf(elements, elements.length); |
1061 |
|
return result; |
725 |
– |
|
1062 |
|
} catch (CloneNotSupportedException e) { |
1063 |
|
throw new AssertionError(); |
1064 |
|
} |
1065 |
|
} |
1066 |
|
|
731 |
– |
/** |
732 |
– |
* Appease the serialization gods. |
733 |
– |
*/ |
1067 |
|
private static final long serialVersionUID = 2340985798034038923L; |
1068 |
|
|
1069 |
|
/** |
1070 |
< |
* Serialize this deque. |
1070 |
> |
* Saves this deque to a stream (that is, serializes it). |
1071 |
|
* |
1072 |
< |
* @serialData The current size (<tt>int</tt>) of the deque, |
1072 |
> |
* @param s the stream |
1073 |
> |
* @throws java.io.IOException if an I/O error occurs |
1074 |
> |
* @serialData The current size ({@code int}) of the deque, |
1075 |
|
* followed by all of its elements (each an object reference) in |
1076 |
|
* first-to-last order. |
1077 |
|
*/ |
1078 |
< |
private void writeObject(ObjectOutputStream s) throws IOException { |
1078 |
> |
private void writeObject(java.io.ObjectOutputStream s) |
1079 |
> |
throws java.io.IOException { |
1080 |
|
s.defaultWriteObject(); |
1081 |
|
|
1082 |
|
// Write out size |
747 |
– |
int size = size(); |
1083 |
|
s.writeInt(size); |
1084 |
|
|
1085 |
|
// Write out elements in order. |
1086 |
< |
int i = head; |
1087 |
< |
int mask = elements.length - 1; |
1088 |
< |
for (int j = 0; j < size; j++) { |
1086 |
> |
final Object[] elements = this.elements; |
1087 |
> |
final int capacity = elements.length; |
1088 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
1089 |
|
s.writeObject(elements[i]); |
755 |
– |
i = (i + 1) & mask; |
756 |
– |
} |
1090 |
|
} |
1091 |
|
|
1092 |
|
/** |
1093 |
< |
* Deserialize this deque. |
1093 |
> |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1094 |
> |
* @param s the stream |
1095 |
> |
* @throws ClassNotFoundException if the class of a serialized object |
1096 |
> |
* could not be found |
1097 |
> |
* @throws java.io.IOException if an I/O error occurs |
1098 |
|
*/ |
1099 |
< |
private void readObject(ObjectInputStream s) |
1100 |
< |
throws IOException, ClassNotFoundException { |
1099 |
> |
private void readObject(java.io.ObjectInputStream s) |
1100 |
> |
throws java.io.IOException, ClassNotFoundException { |
1101 |
|
s.defaultReadObject(); |
1102 |
|
|
1103 |
|
// Read in size and allocate array |
1104 |
< |
int size = s.readInt(); |
768 |
< |
allocateElements(size); |
769 |
< |
head = 0; |
770 |
< |
tail = size; |
1104 |
> |
elements = new Object[size = s.readInt()]; |
1105 |
|
|
1106 |
|
// Read in all elements in the proper order. |
1107 |
|
for (int i = 0; i < size; i++) |
1108 |
< |
elements[i] = (E)s.readObject(); |
1108 |
> |
elements[i] = s.readObject(); |
1109 |
> |
} |
1110 |
|
|
1111 |
+ |
/** debugging */ |
1112 |
+ |
private void checkInvariants() { |
1113 |
+ |
try { |
1114 |
+ |
int capacity = elements.length; |
1115 |
+ |
assert size >= 0 && size <= capacity; |
1116 |
+ |
assert head >= 0 && ((capacity == 0 && head == 0 && size == 0) |
1117 |
+ |
|| head < capacity); |
1118 |
+ |
assert size == 0 |
1119 |
+ |
|| (elements[head] != null && elements[tail()] != null); |
1120 |
+ |
assert size == capacity |
1121 |
+ |
|| (elements[dec(head, capacity)] == null |
1122 |
+ |
&& elements[inc(tail(), capacity)] == null); |
1123 |
+ |
} catch (Throwable t) { |
1124 |
+ |
System.err.printf("head=%d size=%d capacity=%d%n", |
1125 |
+ |
head, size, elements.length); |
1126 |
+ |
System.err.printf("elements=%s%n", |
1127 |
+ |
Arrays.toString(elements)); |
1128 |
+ |
throw t; |
1129 |
+ |
} |
1130 |
|
} |
1131 |
+ |
|
1132 |
|
} |