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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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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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* 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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* 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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* 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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* arbitrary number 0 <= head < elements.length 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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/** |
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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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/** Number of elements in this collection. */ |
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transient int size; |
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/** |
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* The minimum capacity that we'll use for a newly created deque. |
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* Must be a power of 2. |
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*/ |
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private static final int MIN_INITIAL_CAPACITY = 8; |
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// ****** Array allocation and resizing utilities ****** |
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/** |
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* Allocate empty array to hold the given number of elements. |
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* |
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* @param numElements the number of elements to hold |
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*/ |
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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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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 TBD |
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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 TBD |
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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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* @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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size = elements.length; |
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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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this.elements = elements; |
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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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* 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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* 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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* 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(); |
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< |
elements[head = (head - 1) & (elements.length - 1)] = e; |
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< |
if (head == tail) |
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< |
doubleCapacity(); |
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> |
// checkInvariants(); |
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> |
Objects.requireNonNull(e); |
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> |
final Object[] elements; |
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> |
final int capacity, s; |
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> |
if ((s = size) == (capacity = (elements = this.elements).length)) |
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addFirstSlowPath(e); |
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else |
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elements[head = dec(head, capacity)] = e; |
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size = s + 1; |
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// checkInvariants(); |
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} |
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> |
|
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> |
private void addFirstSlowPath(E e) { |
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grow(1); |
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final Object[] elements = this.elements; |
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elements[head = dec(head, elements.length)] = e; |
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} |
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|
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/** |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public void addLast(E e) { |
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< |
if (e == null) |
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< |
throw new NullPointerException(); |
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< |
elements[tail] = e; |
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< |
if ( (tail = (tail + 1) & (elements.length - 1)) == head) |
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< |
doubleCapacity(); |
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> |
// checkInvariants(); |
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> |
Objects.requireNonNull(e); |
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> |
final Object[] elements; |
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> |
final int capacity, s; |
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> |
if ((s = size) == (capacity = (elements = this.elements).length)) |
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> |
addLastSlowPath(e); |
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else |
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> |
elements[add(head, s, capacity)] = e; |
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> |
size = s + 1; |
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> |
// checkInvariants(); |
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> |
} |
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> |
|
| 303 |
> |
private void addLastSlowPath(E e) { |
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> |
grow(1); |
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> |
final Object[] elements = this.elements; |
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elements[add(head, size, elements.length)] = e; |
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> |
} |
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> |
|
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> |
/** |
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> |
* Adds all of the elements in the specified collection at the end |
| 311 |
> |
* of this deque, as if by calling {@link #addLast} on each one, |
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> |
* in the order that they are returned by the collection's |
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* iterator. |
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* |
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> |
* @param c the elements to be inserted into this deque |
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> |
* @return {@code true} if this deque changed as a result of the call |
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> |
* @throws NullPointerException if the specified collection or any |
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> |
* of its elements are null |
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> |
*/ |
| 320 |
> |
public boolean addAll(Collection<? extends E> c) { |
| 321 |
> |
final int s = size, needed = c.size() - (elements.length - s); |
| 322 |
> |
if (needed > 0) |
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> |
grow(needed); |
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> |
c.forEach((e) -> addLast(e)); |
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> |
// checkInvariants(); |
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> |
return size > s; |
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} |
| 328 |
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|
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/** |
| 330 |
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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 |
| 333 |
< |
* @return <tt>true</tt> (as specified by {@link Deque#offerFirst}) |
| 333 |
> |
* @return {@code true} (as specified by {@link Deque#offerFirst}) |
| 334 |
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* @throws NullPointerException if the specified element is null |
| 335 |
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*/ |
| 336 |
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public boolean offerFirst(E e) { |
| 342 |
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* Inserts the specified element at the end of this deque. |
| 343 |
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* |
| 344 |
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* @param e the element to add |
| 345 |
< |
* @return <tt>true</tt> (as specified by {@link Deque#offerLast}) |
| 345 |
> |
* @return {@code true} (as specified by {@link Deque#offerLast}) |
| 346 |
|
* @throws NullPointerException if the specified element is null |
| 347 |
|
*/ |
| 348 |
|
public boolean offerLast(E e) { |
| 354 |
|
* @throws NoSuchElementException {@inheritDoc} |
| 355 |
|
*/ |
| 356 |
|
public E removeFirst() { |
| 357 |
< |
E x = pollFirst(); |
| 358 |
< |
if (x == null) |
| 357 |
> |
// checkInvariants(); |
| 358 |
> |
E e = pollFirst(); |
| 359 |
> |
if (e == null) |
| 360 |
|
throw new NoSuchElementException(); |
| 361 |
< |
return x; |
| 361 |
> |
return e; |
| 362 |
|
} |
| 363 |
|
|
| 364 |
|
/** |
| 365 |
|
* @throws NoSuchElementException {@inheritDoc} |
| 366 |
|
*/ |
| 367 |
|
public E removeLast() { |
| 368 |
< |
E x = pollLast(); |
| 369 |
< |
if (x == null) |
| 368 |
> |
// checkInvariants(); |
| 369 |
> |
E e = pollLast(); |
| 370 |
> |
if (e == null) |
| 371 |
|
throw new NoSuchElementException(); |
| 372 |
< |
return x; |
| 372 |
> |
return e; |
| 373 |
|
} |
| 374 |
|
|
| 375 |
|
public E pollFirst() { |
| 376 |
< |
int h = head; |
| 377 |
< |
E result = elements[h]; // Element is null if deque empty |
| 378 |
< |
if (result == null) |
| 376 |
> |
// checkInvariants(); |
| 377 |
> |
final int s, h; |
| 378 |
> |
if ((s = size) == 0) |
| 379 |
|
return null; |
| 380 |
< |
elements[h] = null; // Must null out slot |
| 381 |
< |
head = (h + 1) & (elements.length - 1); |
| 382 |
< |
return result; |
| 380 |
> |
final Object[] elements = this.elements; |
| 381 |
> |
@SuppressWarnings("unchecked") E e = (E) elements[h = head]; |
| 382 |
> |
elements[h] = null; |
| 383 |
> |
head = inc(h, elements.length); |
| 384 |
> |
size = s - 1; |
| 385 |
> |
return e; |
| 386 |
|
} |
| 387 |
|
|
| 388 |
|
public E pollLast() { |
| 389 |
< |
int t = (tail - 1) & (elements.length - 1); |
| 390 |
< |
E result = elements[t]; |
| 391 |
< |
if (result == null) |
| 389 |
> |
// checkInvariants(); |
| 390 |
> |
final int s, tail; |
| 391 |
> |
if ((s = size) == 0) |
| 392 |
|
return null; |
| 393 |
< |
elements[t] = null; |
| 394 |
< |
tail = t; |
| 395 |
< |
return result; |
| 393 |
> |
final Object[] elements = this.elements; |
| 394 |
> |
@SuppressWarnings("unchecked") |
| 395 |
> |
E e = (E) elements[tail = add(head, s - 1, elements.length)]; |
| 396 |
> |
elements[tail] = null; |
| 397 |
> |
size = s - 1; |
| 398 |
> |
return e; |
| 399 |
|
} |
| 400 |
|
|
| 401 |
|
/** |
| 402 |
|
* @throws NoSuchElementException {@inheritDoc} |
| 403 |
|
*/ |
| 404 |
|
public E getFirst() { |
| 405 |
< |
E x = elements[head]; |
| 406 |
< |
if (x == null) |
| 407 |
< |
throw new NoSuchElementException(); |
| 290 |
< |
return x; |
| 405 |
> |
// checkInvariants(); |
| 406 |
> |
if (size == 0) throw new NoSuchElementException(); |
| 407 |
> |
return elementAt(head); |
| 408 |
|
} |
| 409 |
|
|
| 410 |
|
/** |
| 411 |
|
* @throws NoSuchElementException {@inheritDoc} |
| 412 |
|
*/ |
| 413 |
|
public E getLast() { |
| 414 |
< |
E x = elements[(tail - 1) & (elements.length - 1)]; |
| 415 |
< |
if (x == null) |
| 416 |
< |
throw new NoSuchElementException(); |
| 300 |
< |
return x; |
| 414 |
> |
// checkInvariants(); |
| 415 |
> |
if (size == 0) throw new NoSuchElementException(); |
| 416 |
> |
return elementAt(tail()); |
| 417 |
|
} |
| 418 |
|
|
| 419 |
|
public E peekFirst() { |
| 420 |
< |
return elements[head]; // elements[head] is null if deque empty |
| 420 |
> |
// checkInvariants(); |
| 421 |
> |
return (size == 0) ? null : elementAt(head); |
| 422 |
|
} |
| 423 |
|
|
| 424 |
|
public E peekLast() { |
| 425 |
< |
return elements[(tail - 1) & (elements.length - 1)]; |
| 425 |
> |
// checkInvariants(); |
| 426 |
> |
return (size == 0) ? null : elementAt(tail()); |
| 427 |
|
} |
| 428 |
|
|
| 429 |
|
/** |
| 430 |
|
* Removes the first occurrence of the specified element in this |
| 431 |
|
* deque (when traversing the deque from head to tail). |
| 432 |
|
* If the deque does not contain the element, it is unchanged. |
| 433 |
< |
* More formally, removes the first element <tt>e</tt> such that |
| 434 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
| 435 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
| 433 |
> |
* More formally, removes the first element {@code e} such that |
| 434 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 435 |
> |
* Returns {@code true} if this deque contained the specified element |
| 436 |
|
* (or equivalently, if this deque changed as a result of the call). |
| 437 |
|
* |
| 438 |
|
* @param o element to be removed from this deque, if present |
| 439 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
| 439 |
> |
* @return {@code true} if the deque contained the specified element |
| 440 |
|
*/ |
| 441 |
|
public boolean removeFirstOccurrence(Object o) { |
| 442 |
< |
if (o == null) |
| 443 |
< |
return false; |
| 444 |
< |
int mask = elements.length - 1; |
| 445 |
< |
int i = head; |
| 446 |
< |
E x; |
| 447 |
< |
while ( (x = elements[i]) != null) { |
| 448 |
< |
if (o.equals(x)) { |
| 449 |
< |
delete(i); |
| 450 |
< |
return true; |
| 442 |
> |
// checkInvariants(); |
| 443 |
> |
if (o != null) { |
| 444 |
> |
final Object[] elements = this.elements; |
| 445 |
> |
final int capacity = elements.length; |
| 446 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) { |
| 447 |
> |
if (o.equals(elements[i])) { |
| 448 |
> |
delete(i); |
| 449 |
> |
return true; |
| 450 |
> |
} |
| 451 |
|
} |
| 334 |
– |
i = (i + 1) & mask; |
| 452 |
|
} |
| 453 |
|
return false; |
| 454 |
|
} |
| 457 |
|
* Removes the last occurrence of the specified element in this |
| 458 |
|
* deque (when traversing the deque from head to tail). |
| 459 |
|
* If the deque does not contain the element, it is unchanged. |
| 460 |
< |
* More formally, removes the last element <tt>e</tt> such that |
| 461 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
| 462 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
| 460 |
> |
* More formally, removes the last element {@code e} such that |
| 461 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 462 |
> |
* Returns {@code true} if this deque contained the specified element |
| 463 |
|
* (or equivalently, if this deque changed as a result of the call). |
| 464 |
|
* |
| 465 |
|
* @param o element to be removed from this deque, if present |
| 466 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
| 466 |
> |
* @return {@code true} if the deque contained the specified element |
| 467 |
|
*/ |
| 468 |
|
public boolean removeLastOccurrence(Object o) { |
| 469 |
< |
if (o == null) |
| 470 |
< |
return false; |
| 471 |
< |
int mask = elements.length - 1; |
| 472 |
< |
int i = (tail - 1) & mask; |
| 473 |
< |
E x; |
| 474 |
< |
while ( (x = elements[i]) != null) { |
| 475 |
< |
if (o.equals(x)) { |
| 476 |
< |
delete(i); |
| 477 |
< |
return true; |
| 469 |
> |
if (o != null) { |
| 470 |
> |
final Object[] elements = this.elements; |
| 471 |
> |
final int capacity = elements.length; |
| 472 |
> |
for (int k = size, i = add(head, k - 1, capacity); |
| 473 |
> |
--k >= 0; i = dec(i, capacity)) { |
| 474 |
> |
if (o.equals(elements[i])) { |
| 475 |
> |
delete(i); |
| 476 |
> |
return true; |
| 477 |
> |
} |
| 478 |
|
} |
| 362 |
– |
i = (i - 1) & mask; |
| 479 |
|
} |
| 480 |
|
return false; |
| 481 |
|
} |
| 488 |
|
* <p>This method is equivalent to {@link #addLast}. |
| 489 |
|
* |
| 490 |
|
* @param e the element to add |
| 491 |
< |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
| 491 |
> |
* @return {@code true} (as specified by {@link Collection#add}) |
| 492 |
|
* @throws NullPointerException if the specified element is null |
| 493 |
|
*/ |
| 494 |
|
public boolean add(E e) { |
| 502 |
|
* <p>This method is equivalent to {@link #offerLast}. |
| 503 |
|
* |
| 504 |
|
* @param e the element to add |
| 505 |
< |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
| 505 |
> |
* @return {@code true} (as specified by {@link Queue#offer}) |
| 506 |
|
* @throws NullPointerException if the specified element is null |
| 507 |
|
*/ |
| 508 |
|
public boolean offer(E e) { |
| 527 |
|
/** |
| 528 |
|
* Retrieves and removes the head of the queue represented by this deque |
| 529 |
|
* (in other words, the first element of this deque), or returns |
| 530 |
< |
* <tt>null</tt> if this deque is empty. |
| 530 |
> |
* {@code null} if this deque is empty. |
| 531 |
|
* |
| 532 |
|
* <p>This method is equivalent to {@link #pollFirst}. |
| 533 |
|
* |
| 534 |
|
* @return the head of the queue represented by this deque, or |
| 535 |
< |
* <tt>null</tt> if this deque is empty |
| 535 |
> |
* {@code null} if this deque is empty |
| 536 |
|
*/ |
| 537 |
|
public E poll() { |
| 538 |
|
return pollFirst(); |
| 554 |
|
|
| 555 |
|
/** |
| 556 |
|
* Retrieves, but does not remove, the head of the queue represented by |
| 557 |
< |
* this deque, or returns <tt>null</tt> if this deque is empty. |
| 557 |
> |
* this deque, or returns {@code null} if this deque is empty. |
| 558 |
|
* |
| 559 |
|
* <p>This method is equivalent to {@link #peekFirst}. |
| 560 |
|
* |
| 561 |
|
* @return the head of the queue represented by this deque, or |
| 562 |
< |
* <tt>null</tt> if this deque is empty |
| 562 |
> |
* {@code null} if this deque is empty |
| 563 |
|
*/ |
| 564 |
|
public E peek() { |
| 565 |
|
return peekFirst(); |
| 594 |
|
return removeFirst(); |
| 595 |
|
} |
| 596 |
|
|
| 481 |
– |
private void checkInvariants() { |
| 482 |
– |
assert elements[tail] == null; |
| 483 |
– |
assert head == tail ? elements[head] == null : |
| 484 |
– |
(elements[head] != null && |
| 485 |
– |
elements[(tail - 1) & (elements.length - 1)] != null); |
| 486 |
– |
assert elements[(head - 1) & (elements.length - 1)] == null; |
| 487 |
– |
} |
| 488 |
– |
|
| 597 |
|
/** |
| 598 |
< |
* Removes the element at the specified position in the elements array, |
| 599 |
< |
* adjusting head and tail as necessary. This can result in motion of |
| 600 |
< |
* elements backwards or forwards in the array. |
| 598 |
> |
* Removes the element at the specified position in the elements array. |
| 599 |
> |
* This can result in forward or backwards motion of array elements. |
| 600 |
> |
* We optimize for least element motion. |
| 601 |
|
* |
| 602 |
|
* <p>This method is called delete rather than remove to emphasize |
| 603 |
|
* that its semantics differ from those of {@link List#remove(int)}. |
| 604 |
|
* |
| 605 |
|
* @return true if elements moved backwards |
| 606 |
|
*/ |
| 607 |
< |
private boolean delete(int i) { |
| 608 |
< |
checkInvariants(); |
| 609 |
< |
final E[] elements = this.elements; |
| 610 |
< |
final int mask = elements.length - 1; |
| 607 |
> |
boolean delete(int i) { |
| 608 |
> |
// checkInvariants(); |
| 609 |
> |
final Object[] elements = this.elements; |
| 610 |
> |
final int capacity = elements.length; |
| 611 |
|
final int h = head; |
| 612 |
< |
final int t = tail; |
| 613 |
< |
final int front = (i - h) & mask; |
| 614 |
< |
final int back = (t - i) & mask; |
| 507 |
< |
|
| 508 |
< |
// Invariant: head <= i < tail mod circularity |
| 509 |
< |
if (front >= ((t - h) & mask)) |
| 510 |
< |
throw new ConcurrentModificationException(); |
| 511 |
< |
|
| 512 |
< |
// Optimize for least element motion |
| 612 |
> |
int front; // number of elements before to-be-deleted elt |
| 613 |
> |
if ((front = i - h) < 0) front += capacity; |
| 614 |
> |
final int back = size - front - 1; // number of elements after |
| 615 |
|
if (front < back) { |
| 616 |
+ |
// move front elements forwards |
| 617 |
|
if (h <= i) { |
| 618 |
|
System.arraycopy(elements, h, elements, h + 1, front); |
| 619 |
|
} else { // Wrap around |
| 620 |
|
System.arraycopy(elements, 0, elements, 1, i); |
| 621 |
< |
elements[0] = elements[mask]; |
| 622 |
< |
System.arraycopy(elements, h, elements, h + 1, mask - h); |
| 621 |
> |
elements[0] = elements[capacity - 1]; |
| 622 |
> |
System.arraycopy(elements, h, elements, h + 1, front - (i + 1)); |
| 623 |
|
} |
| 624 |
|
elements[h] = null; |
| 625 |
< |
head = (h + 1) & mask; |
| 625 |
> |
head = inc(h, capacity); |
| 626 |
> |
size--; |
| 627 |
> |
// checkInvariants(); |
| 628 |
|
return false; |
| 629 |
|
} else { |
| 630 |
< |
if (i < t) { // Copy the null tail as well |
| 630 |
> |
// move back elements backwards |
| 631 |
> |
int tail = tail(); |
| 632 |
> |
if (i <= tail) { |
| 633 |
|
System.arraycopy(elements, i + 1, elements, i, back); |
| 527 |
– |
tail = t - 1; |
| 634 |
|
} else { // Wrap around |
| 635 |
< |
System.arraycopy(elements, i + 1, elements, i, mask - i); |
| 636 |
< |
elements[mask] = elements[0]; |
| 637 |
< |
System.arraycopy(elements, 1, elements, 0, t); |
| 638 |
< |
tail = (t - 1) & mask; |
| 635 |
> |
int firstLeg = capacity - (i + 1); |
| 636 |
> |
System.arraycopy(elements, i + 1, elements, i, firstLeg); |
| 637 |
> |
elements[capacity - 1] = elements[0]; |
| 638 |
> |
System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1); |
| 639 |
|
} |
| 640 |
+ |
elements[tail] = null; |
| 641 |
+ |
size--; |
| 642 |
+ |
// checkInvariants(); |
| 643 |
|
return true; |
| 644 |
|
} |
| 645 |
|
} |
| 652 |
|
* @return the number of elements in this deque |
| 653 |
|
*/ |
| 654 |
|
public int size() { |
| 655 |
< |
return (tail - head) & (elements.length - 1); |
| 655 |
> |
return size; |
| 656 |
|
} |
| 657 |
|
|
| 658 |
|
/** |
| 659 |
< |
* Returns <tt>true</tt> if this deque contains no elements. |
| 659 |
> |
* Returns {@code true} if this deque contains no elements. |
| 660 |
|
* |
| 661 |
< |
* @return <tt>true</tt> if this deque contains no elements |
| 661 |
> |
* @return {@code true} if this deque contains no elements |
| 662 |
|
*/ |
| 663 |
|
public boolean isEmpty() { |
| 664 |
< |
return head == tail; |
| 664 |
> |
return size == 0; |
| 665 |
|
} |
| 666 |
|
|
| 667 |
|
/** |
| 681 |
|
} |
| 682 |
|
|
| 683 |
|
private class DeqIterator implements Iterator<E> { |
| 684 |
< |
/** |
| 685 |
< |
* Index of element to be returned by subsequent call to next. |
| 577 |
< |
*/ |
| 578 |
< |
private int cursor = head; |
| 684 |
> |
/** Index of element to be returned by subsequent call to next. */ |
| 685 |
> |
int cursor; |
| 686 |
|
|
| 687 |
< |
/** |
| 688 |
< |
* Tail recorded at construction (also in remove), to stop |
| 582 |
< |
* iterator and also to check for comodification. |
| 583 |
< |
*/ |
| 584 |
< |
private int fence = tail; |
| 687 |
> |
/** Number of elements yet to be returned. */ |
| 688 |
> |
int remaining = size; |
| 689 |
|
|
| 690 |
|
/** |
| 691 |
|
* Index of element returned by most recent call to next. |
| 692 |
|
* Reset to -1 if element is deleted by a call to remove. |
| 693 |
|
*/ |
| 694 |
< |
private int lastRet = -1; |
| 694 |
> |
int lastRet = -1; |
| 695 |
> |
|
| 696 |
> |
DeqIterator() { cursor = head; } |
| 697 |
|
|
| 698 |
< |
public boolean hasNext() { |
| 699 |
< |
return cursor != fence; |
| 698 |
> |
public final boolean hasNext() { |
| 699 |
> |
return remaining > 0; |
| 700 |
|
} |
| 701 |
|
|
| 702 |
|
public E next() { |
| 703 |
< |
if (cursor == fence) |
| 703 |
> |
if (remaining == 0) |
| 704 |
|
throw new NoSuchElementException(); |
| 705 |
< |
E result = elements[cursor]; |
| 600 |
< |
// This check doesn't catch all possible comodifications, |
| 601 |
< |
// but does catch the ones that corrupt traversal |
| 602 |
< |
if (tail != fence || result == null) |
| 603 |
< |
throw new ConcurrentModificationException(); |
| 705 |
> |
E e = checkedElementAt(elements, cursor); |
| 706 |
|
lastRet = cursor; |
| 707 |
< |
cursor = (cursor + 1) & (elements.length - 1); |
| 708 |
< |
return result; |
| 707 |
> |
cursor = inc(cursor, elements.length); |
| 708 |
> |
remaining--; |
| 709 |
> |
return e; |
| 710 |
> |
} |
| 711 |
> |
|
| 712 |
> |
void postDelete(boolean leftShifted) { |
| 713 |
> |
if (leftShifted) |
| 714 |
> |
cursor = dec(cursor, elements.length); // undo inc in next |
| 715 |
|
} |
| 716 |
|
|
| 717 |
< |
public void remove() { |
| 717 |
> |
public final void remove() { |
| 718 |
|
if (lastRet < 0) |
| 719 |
|
throw new IllegalStateException(); |
| 720 |
< |
if (delete(lastRet)) { // if left-shifted, undo increment in next() |
| 613 |
< |
cursor = (cursor - 1) & (elements.length - 1); |
| 614 |
< |
fence = tail; |
| 615 |
< |
} |
| 720 |
> |
postDelete(delete(lastRet)); |
| 721 |
|
lastRet = -1; |
| 722 |
|
} |
| 618 |
– |
} |
| 619 |
– |
|
| 620 |
– |
private class DescendingIterator implements Iterator<E> { |
| 621 |
– |
/* |
| 622 |
– |
* This class is nearly a mirror-image of DeqIterator, using |
| 623 |
– |
* tail instead of head for initial cursor, and head instead of |
| 624 |
– |
* tail for fence. |
| 625 |
– |
*/ |
| 626 |
– |
private int cursor = tail; |
| 627 |
– |
private int fence = head; |
| 628 |
– |
private int lastRet = -1; |
| 723 |
|
|
| 724 |
< |
public boolean hasNext() { |
| 725 |
< |
return cursor != fence; |
| 724 |
> |
public void forEachRemaining(Consumer<? super E> action) { |
| 725 |
> |
Objects.requireNonNull(action); |
| 726 |
> |
final Object[] elements = ArrayDeque.this.elements; |
| 727 |
> |
final int capacity = elements.length; |
| 728 |
> |
int k = remaining; |
| 729 |
> |
remaining = 0; |
| 730 |
> |
for (int i = cursor; --k >= 0; i = inc(i, capacity)) |
| 731 |
> |
action.accept(checkedElementAt(elements, i)); |
| 732 |
|
} |
| 733 |
+ |
} |
| 734 |
|
|
| 735 |
< |
public E next() { |
| 736 |
< |
if (cursor == fence) |
| 735 |
> |
private class DescendingIterator extends DeqIterator { |
| 736 |
> |
DescendingIterator() { cursor = tail(); } |
| 737 |
> |
|
| 738 |
> |
public final E next() { |
| 739 |
> |
if (remaining == 0) |
| 740 |
|
throw new NoSuchElementException(); |
| 741 |
< |
cursor = (cursor - 1) & (elements.length - 1); |
| 638 |
< |
E result = elements[cursor]; |
| 639 |
< |
if (head != fence || result == null) |
| 640 |
< |
throw new ConcurrentModificationException(); |
| 741 |
> |
E e = checkedElementAt(elements, cursor); |
| 742 |
|
lastRet = cursor; |
| 743 |
< |
return result; |
| 743 |
> |
cursor = dec(cursor, elements.length); |
| 744 |
> |
remaining--; |
| 745 |
> |
return e; |
| 746 |
|
} |
| 747 |
|
|
| 748 |
< |
public void remove() { |
| 749 |
< |
if (lastRet < 0) |
| 750 |
< |
throw new IllegalStateException(); |
| 751 |
< |
if (!delete(lastRet)) { |
| 752 |
< |
cursor = (cursor + 1) & (elements.length - 1); |
| 753 |
< |
fence = head; |
| 748 |
> |
void postDelete(boolean leftShifted) { |
| 749 |
> |
if (!leftShifted) |
| 750 |
> |
cursor = inc(cursor, elements.length); // undo dec in next |
| 751 |
> |
} |
| 752 |
> |
|
| 753 |
> |
public final void forEachRemaining(Consumer<? super E> action) { |
| 754 |
> |
Objects.requireNonNull(action); |
| 755 |
> |
final Object[] elements = ArrayDeque.this.elements; |
| 756 |
> |
final int capacity = elements.length; |
| 757 |
> |
int k = remaining; |
| 758 |
> |
remaining = 0; |
| 759 |
> |
for (int i = cursor; --k >= 0; i = dec(i, capacity)) |
| 760 |
> |
action.accept(checkedElementAt(elements, i)); |
| 761 |
> |
} |
| 762 |
> |
} |
| 763 |
> |
|
| 764 |
> |
/** |
| 765 |
> |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
| 766 |
> |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
| 767 |
> |
* deque. |
| 768 |
> |
* |
| 769 |
> |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
| 770 |
> |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
| 771 |
> |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
| 772 |
> |
* the reporting of additional characteristic values. |
| 773 |
> |
* |
| 774 |
> |
* @return a {@code Spliterator} over the elements in this deque |
| 775 |
> |
* @since 1.8 |
| 776 |
> |
*/ |
| 777 |
> |
public Spliterator<E> spliterator() { |
| 778 |
> |
return new ArrayDequeSpliterator(); |
| 779 |
> |
} |
| 780 |
> |
|
| 781 |
> |
final class ArrayDequeSpliterator implements Spliterator<E> { |
| 782 |
> |
private int cursor; |
| 783 |
> |
private int remaining; // -1 until late-binding first use |
| 784 |
> |
|
| 785 |
> |
/** Constructs late-binding spliterator over all elements. */ |
| 786 |
> |
ArrayDequeSpliterator() { |
| 787 |
> |
this.remaining = -1; |
| 788 |
> |
} |
| 789 |
> |
|
| 790 |
> |
/** Constructs spliterator over the given slice. */ |
| 791 |
> |
ArrayDequeSpliterator(int cursor, int count) { |
| 792 |
> |
this.cursor = cursor; |
| 793 |
> |
this.remaining = count; |
| 794 |
> |
} |
| 795 |
> |
|
| 796 |
> |
/** Ensures late-binding initialization; then returns remaining. */ |
| 797 |
> |
private int remaining() { |
| 798 |
> |
if (remaining < 0) { |
| 799 |
> |
cursor = head; |
| 800 |
> |
remaining = size; |
| 801 |
|
} |
| 802 |
< |
lastRet = -1; |
| 802 |
> |
return remaining; |
| 803 |
> |
} |
| 804 |
> |
|
| 805 |
> |
public ArrayDequeSpliterator trySplit() { |
| 806 |
> |
final int mid; |
| 807 |
> |
if ((mid = remaining() >> 1) > 0) { |
| 808 |
> |
int oldCursor = cursor; |
| 809 |
> |
cursor = add(cursor, mid, elements.length); |
| 810 |
> |
remaining -= mid; |
| 811 |
> |
return new ArrayDequeSpliterator(oldCursor, mid); |
| 812 |
> |
} |
| 813 |
> |
return null; |
| 814 |
> |
} |
| 815 |
> |
|
| 816 |
> |
public void forEachRemaining(Consumer<? super E> action) { |
| 817 |
> |
Objects.requireNonNull(action); |
| 818 |
> |
final Object[] elements = ArrayDeque.this.elements; |
| 819 |
> |
final int capacity = elements.length; |
| 820 |
> |
int k = remaining(); |
| 821 |
> |
remaining = 0; |
| 822 |
> |
for (int i = cursor; --k >= 0; i = inc(i, capacity)) |
| 823 |
> |
action.accept(checkedElementAt(elements, i)); |
| 824 |
> |
} |
| 825 |
> |
|
| 826 |
> |
public boolean tryAdvance(Consumer<? super E> action) { |
| 827 |
> |
Objects.requireNonNull(action); |
| 828 |
> |
if (remaining() == 0) |
| 829 |
> |
return false; |
| 830 |
> |
action.accept(checkedElementAt(elements, cursor)); |
| 831 |
> |
cursor = inc(cursor, elements.length); |
| 832 |
> |
remaining--; |
| 833 |
> |
return true; |
| 834 |
> |
} |
| 835 |
> |
|
| 836 |
> |
public long estimateSize() { |
| 837 |
> |
return remaining(); |
| 838 |
> |
} |
| 839 |
> |
|
| 840 |
> |
public int characteristics() { |
| 841 |
> |
return Spliterator.NONNULL |
| 842 |
> |
| Spliterator.ORDERED |
| 843 |
> |
| Spliterator.SIZED |
| 844 |
> |
| Spliterator.SUBSIZED; |
| 845 |
> |
} |
| 846 |
> |
} |
| 847 |
> |
|
| 848 |
> |
public void forEach(Consumer<? super E> action) { |
| 849 |
> |
// checkInvariants(); |
| 850 |
> |
Objects.requireNonNull(action); |
| 851 |
> |
final Object[] elements = this.elements; |
| 852 |
> |
final int capacity = elements.length; |
| 853 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
| 854 |
> |
action.accept(elementAt(i)); |
| 855 |
> |
// checkInvariants(); |
| 856 |
> |
} |
| 857 |
> |
|
| 858 |
> |
/** |
| 859 |
> |
* Replaces each element of this deque with the result of applying the |
| 860 |
> |
* operator to that element, as specified by {@link List#replaceAll}. |
| 861 |
> |
* |
| 862 |
> |
* @param operator the operator to apply to each element |
| 863 |
> |
* @since TBD |
| 864 |
> |
*/ |
| 865 |
> |
/* public */ void replaceAll(UnaryOperator<E> operator) { |
| 866 |
> |
Objects.requireNonNull(operator); |
| 867 |
> |
final Object[] elements = this.elements; |
| 868 |
> |
final int capacity = elements.length; |
| 869 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
| 870 |
> |
elements[i] = operator.apply(elementAt(i)); |
| 871 |
> |
// checkInvariants(); |
| 872 |
> |
} |
| 873 |
> |
|
| 874 |
> |
/** |
| 875 |
> |
* @throws NullPointerException {@inheritDoc} |
| 876 |
> |
*/ |
| 877 |
> |
public boolean removeIf(Predicate<? super E> filter) { |
| 878 |
> |
Objects.requireNonNull(filter); |
| 879 |
> |
return bulkRemove(filter); |
| 880 |
> |
} |
| 881 |
> |
|
| 882 |
> |
/** |
| 883 |
> |
* @throws NullPointerException {@inheritDoc} |
| 884 |
> |
*/ |
| 885 |
> |
public boolean removeAll(Collection<?> c) { |
| 886 |
> |
Objects.requireNonNull(c); |
| 887 |
> |
return bulkRemove(e -> c.contains(e)); |
| 888 |
> |
} |
| 889 |
> |
|
| 890 |
> |
/** |
| 891 |
> |
* @throws NullPointerException {@inheritDoc} |
| 892 |
> |
*/ |
| 893 |
> |
public boolean retainAll(Collection<?> c) { |
| 894 |
> |
Objects.requireNonNull(c); |
| 895 |
> |
return bulkRemove(e -> !c.contains(e)); |
| 896 |
> |
} |
| 897 |
> |
|
| 898 |
> |
/** Implementation of bulk remove methods. */ |
| 899 |
> |
private boolean bulkRemove(Predicate<? super E> filter) { |
| 900 |
> |
// checkInvariants(); |
| 901 |
> |
final Object[] elements = this.elements; |
| 902 |
> |
final int capacity = elements.length; |
| 903 |
> |
int i = head, j = i, remaining = size, deleted = 0; |
| 904 |
> |
try { |
| 905 |
> |
for (; remaining > 0; remaining--, i = inc(i, capacity)) { |
| 906 |
> |
@SuppressWarnings("unchecked") E e = (E) elements[i]; |
| 907 |
> |
if (filter.test(e)) |
| 908 |
> |
deleted++; |
| 909 |
> |
else { |
| 910 |
> |
if (j != i) |
| 911 |
> |
elements[j] = e; |
| 912 |
> |
j = inc(j, capacity); |
| 913 |
> |
} |
| 914 |
> |
} |
| 915 |
> |
return deleted > 0; |
| 916 |
> |
} catch (Throwable ex) { |
| 917 |
> |
if (deleted > 0) |
| 918 |
> |
for (; remaining > 0; |
| 919 |
> |
remaining--, i = inc(i, capacity), j = inc(j, capacity)) |
| 920 |
> |
elements[j] = elements[i]; |
| 921 |
> |
throw ex; |
| 922 |
> |
} finally { |
| 923 |
> |
size -= deleted; |
| 924 |
> |
for (; --deleted >= 0; j = inc(j, capacity)) |
| 925 |
> |
elements[j] = null; |
| 926 |
> |
// checkInvariants(); |
| 927 |
|
} |
| 928 |
|
} |
| 929 |
|
|
| 930 |
|
/** |
| 931 |
< |
* Returns <tt>true</tt> if this deque contains the specified element. |
| 932 |
< |
* More formally, returns <tt>true</tt> if and only if this deque contains |
| 933 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
| 931 |
> |
* Returns {@code true} if this deque contains the specified element. |
| 932 |
> |
* More formally, returns {@code true} if and only if this deque contains |
| 933 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
| 934 |
|
* |
| 935 |
|
* @param o object to be checked for containment in this deque |
| 936 |
< |
* @return <tt>true</tt> if this deque contains the specified element |
| 936 |
> |
* @return {@code true} if this deque contains the specified element |
| 937 |
|
*/ |
| 938 |
|
public boolean contains(Object o) { |
| 939 |
< |
if (o == null) |
| 940 |
< |
return false; |
| 941 |
< |
int mask = elements.length - 1; |
| 942 |
< |
int i = head; |
| 943 |
< |
E x; |
| 944 |
< |
while ( (x = elements[i]) != null) { |
| 671 |
< |
if (o.equals(x)) |
| 672 |
< |
return true; |
| 673 |
< |
i = (i + 1) & mask; |
| 939 |
> |
if (o != null) { |
| 940 |
> |
final Object[] elements = this.elements; |
| 941 |
> |
final int capacity = elements.length; |
| 942 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
| 943 |
> |
if (o.equals(elements[i])) |
| 944 |
> |
return true; |
| 945 |
|
} |
| 946 |
|
return false; |
| 947 |
|
} |
| 949 |
|
/** |
| 950 |
|
* Removes a single instance of the specified element from this deque. |
| 951 |
|
* If the deque does not contain the element, it is unchanged. |
| 952 |
< |
* More formally, removes the first element <tt>e</tt> such that |
| 953 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
| 954 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
| 952 |
> |
* More formally, removes the first element {@code e} such that |
| 953 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 954 |
> |
* Returns {@code true} if this deque contained the specified element |
| 955 |
|
* (or equivalently, if this deque changed as a result of the call). |
| 956 |
|
* |
| 957 |
< |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
| 957 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
| 958 |
|
* |
| 959 |
|
* @param o element to be removed from this deque, if present |
| 960 |
< |
* @return <tt>true</tt> if this deque contained the specified element |
| 960 |
> |
* @return {@code true} if this deque contained the specified element |
| 961 |
|
*/ |
| 962 |
|
public boolean remove(Object o) { |
| 963 |
|
return removeFirstOccurrence(o); |
| 968 |
|
* The deque will be empty after this call returns. |
| 969 |
|
*/ |
| 970 |
|
public void clear() { |
| 971 |
< |
int h = head; |
| 972 |
< |
int t = tail; |
| 973 |
< |
if (h != t) { // clear all cells |
| 974 |
< |
head = tail = 0; |
| 975 |
< |
int i = h; |
| 976 |
< |
int mask = elements.length - 1; |
| 977 |
< |
do { |
| 707 |
< |
elements[i] = null; |
| 708 |
< |
i = (i + 1) & mask; |
| 709 |
< |
} while (i != t); |
| 971 |
> |
final Object[] elements = this.elements; |
| 972 |
> |
final int capacity = elements.length, tail = head + size; |
| 973 |
> |
if (capacity - tail >= 0) |
| 974 |
> |
Arrays.fill(elements, head, tail, null); |
| 975 |
> |
else { |
| 976 |
> |
Arrays.fill(elements, head, capacity, null); |
| 977 |
> |
Arrays.fill(elements, 0, tail - capacity, null); |
| 978 |
|
} |
| 979 |
+ |
size = head = 0; |
| 980 |
+ |
// checkInvariants(); |
| 981 |
|
} |
| 982 |
|
|
| 983 |
|
/** |
| 994 |
|
* @return an array containing all of the elements in this deque |
| 995 |
|
*/ |
| 996 |
|
public Object[] toArray() { |
| 997 |
< |
return copyElements(new Object[size()]); |
| 997 |
> |
return toArray(Object[].class); |
| 998 |
> |
} |
| 999 |
> |
|
| 1000 |
> |
private <T> T[] toArray(Class<T[]> klazz) { |
| 1001 |
> |
final Object[] elements = this.elements; |
| 1002 |
> |
final int capacity = elements.length; |
| 1003 |
> |
final int head = this.head, tail = head + size; |
| 1004 |
> |
final T[] a; |
| 1005 |
> |
if (tail >= 0) { |
| 1006 |
> |
a = Arrays.copyOfRange(elements, head, tail, klazz); |
| 1007 |
> |
} else { |
| 1008 |
> |
// integer overflow! |
| 1009 |
> |
a = Arrays.copyOfRange(elements, 0, size, klazz); |
| 1010 |
> |
System.arraycopy(elements, head, a, 0, capacity - head); |
| 1011 |
> |
} |
| 1012 |
> |
if (tail - capacity > 0) |
| 1013 |
> |
System.arraycopy(elements, 0, a, capacity - head, tail - capacity); |
| 1014 |
> |
return a; |
| 1015 |
|
} |
| 1016 |
|
|
| 1017 |
|
/** |
| 1025 |
|
* <p>If this deque fits in the specified array with room to spare |
| 1026 |
|
* (i.e., the array has more elements than this deque), the element in |
| 1027 |
|
* the array immediately following the end of the deque is set to |
| 1028 |
< |
* <tt>null</tt>. |
| 1028 |
> |
* {@code null}. |
| 1029 |
|
* |
| 1030 |
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
| 1031 |
|
* array-based and collection-based APIs. Further, this method allows |
| 1032 |
|
* precise control over the runtime type of the output array, and may, |
| 1033 |
|
* under certain circumstances, be used to save allocation costs. |
| 1034 |
|
* |
| 1035 |
< |
* <p>Suppose <tt>x</tt> is a deque known to contain only strings. |
| 1035 |
> |
* <p>Suppose {@code x} is a deque known to contain only strings. |
| 1036 |
|
* The following code can be used to dump the deque into a newly |
| 1037 |
< |
* allocated array of <tt>String</tt>: |
| 1037 |
> |
* allocated array of {@code String}: |
| 1038 |
|
* |
| 1039 |
< |
* <pre> |
| 753 |
< |
* String[] y = x.toArray(new String[0]);</pre> |
| 1039 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
| 1040 |
|
* |
| 1041 |
< |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
| 1042 |
< |
* <tt>toArray()</tt>. |
| 1041 |
> |
* Note that {@code toArray(new Object[0])} is identical in function to |
| 1042 |
> |
* {@code toArray()}. |
| 1043 |
|
* |
| 1044 |
|
* @param a the array into which the elements of the deque are to |
| 1045 |
|
* be stored, if it is big enough; otherwise, a new array of the |
| 1050 |
|
* this deque |
| 1051 |
|
* @throws NullPointerException if the specified array is null |
| 1052 |
|
*/ |
| 1053 |
+ |
@SuppressWarnings("unchecked") |
| 1054 |
|
public <T> T[] toArray(T[] a) { |
| 1055 |
< |
int size = size(); |
| 1056 |
< |
if (a.length < size) |
| 1057 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
| 1058 |
< |
a.getClass().getComponentType(), size); |
| 1059 |
< |
copyElements(a); |
| 1060 |
< |
if (a.length > size) |
| 1055 |
> |
final int size = this.size; |
| 1056 |
> |
if (size > a.length) |
| 1057 |
> |
return toArray((Class<T[]>) a.getClass()); |
| 1058 |
> |
final Object[] elements = this.elements; |
| 1059 |
> |
final int capacity = elements.length; |
| 1060 |
> |
final int head = this.head, tail = head + size; |
| 1061 |
> |
if (capacity - tail >= 0) |
| 1062 |
> |
System.arraycopy(elements, head, a, 0, size); |
| 1063 |
> |
else { |
| 1064 |
> |
System.arraycopy(elements, head, a, 0, capacity - head); |
| 1065 |
> |
System.arraycopy(elements, 0, a, capacity - head, tail - capacity); |
| 1066 |
> |
} |
| 1067 |
> |
if (size < a.length) |
| 1068 |
|
a[size] = null; |
| 1069 |
|
return a; |
| 1070 |
|
} |
| 1078 |
|
*/ |
| 1079 |
|
public ArrayDeque<E> clone() { |
| 1080 |
|
try { |
| 1081 |
+ |
@SuppressWarnings("unchecked") |
| 1082 |
|
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
| 1083 |
|
result.elements = Arrays.copyOf(elements, elements.length); |
| 1084 |
|
return result; |
| 790 |
– |
|
| 1085 |
|
} catch (CloneNotSupportedException e) { |
| 1086 |
|
throw new AssertionError(); |
| 1087 |
|
} |
| 1088 |
|
} |
| 1089 |
|
|
| 796 |
– |
/** |
| 797 |
– |
* Appease the serialization gods. |
| 798 |
– |
*/ |
| 1090 |
|
private static final long serialVersionUID = 2340985798034038923L; |
| 1091 |
|
|
| 1092 |
|
/** |
| 1093 |
< |
* Serialize this deque. |
| 1093 |
> |
* Saves this deque to a stream (that is, serializes it). |
| 1094 |
|
* |
| 1095 |
< |
* @serialData The current size (<tt>int</tt>) of the deque, |
| 1095 |
> |
* @param s the stream |
| 1096 |
> |
* @throws java.io.IOException if an I/O error occurs |
| 1097 |
> |
* @serialData The current size ({@code int}) of the deque, |
| 1098 |
|
* followed by all of its elements (each an object reference) in |
| 1099 |
|
* first-to-last order. |
| 1100 |
|
*/ |
| 1101 |
< |
private void writeObject(ObjectOutputStream s) throws IOException { |
| 1101 |
> |
private void writeObject(java.io.ObjectOutputStream s) |
| 1102 |
> |
throws java.io.IOException { |
| 1103 |
|
s.defaultWriteObject(); |
| 1104 |
|
|
| 1105 |
|
// Write out size |
| 1106 |
< |
s.writeInt(size()); |
| 1106 |
> |
s.writeInt(size); |
| 1107 |
|
|
| 1108 |
|
// Write out elements in order. |
| 1109 |
< |
int mask = elements.length - 1; |
| 1110 |
< |
for (int i = head; i != tail; i = (i + 1) & mask) |
| 1109 |
> |
final Object[] elements = this.elements; |
| 1110 |
> |
final int capacity = elements.length; |
| 1111 |
> |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
| 1112 |
|
s.writeObject(elements[i]); |
| 1113 |
|
} |
| 1114 |
|
|
| 1115 |
|
/** |
| 1116 |
< |
* Deserialize this deque. |
| 1116 |
> |
* Reconstitutes this deque from a stream (that is, deserializes it). |
| 1117 |
> |
* @param s the stream |
| 1118 |
> |
* @throws ClassNotFoundException if the class of a serialized object |
| 1119 |
> |
* could not be found |
| 1120 |
> |
* @throws java.io.IOException if an I/O error occurs |
| 1121 |
|
*/ |
| 1122 |
< |
private void readObject(ObjectInputStream s) |
| 1123 |
< |
throws IOException, ClassNotFoundException { |
| 1122 |
> |
private void readObject(java.io.ObjectInputStream s) |
| 1123 |
> |
throws java.io.IOException, ClassNotFoundException { |
| 1124 |
|
s.defaultReadObject(); |
| 1125 |
|
|
| 1126 |
|
// Read in size and allocate array |
| 1127 |
< |
int size = s.readInt(); |
| 829 |
< |
allocateElements(size); |
| 830 |
< |
head = 0; |
| 831 |
< |
tail = size; |
| 1127 |
> |
elements = new Object[size = s.readInt()]; |
| 1128 |
|
|
| 1129 |
|
// Read in all elements in the proper order. |
| 1130 |
|
for (int i = 0; i < size; i++) |
| 1131 |
< |
elements[i] = (E)s.readObject(); |
| 1131 |
> |
elements[i] = s.readObject(); |
| 1132 |
|
} |
| 1133 |
+ |
|
| 1134 |
+ |
/** debugging */ |
| 1135 |
+ |
private void checkInvariants() { |
| 1136 |
+ |
try { |
| 1137 |
+ |
int capacity = elements.length; |
| 1138 |
+ |
assert size >= 0 && size <= capacity; |
| 1139 |
+ |
assert head >= 0 && ((capacity == 0 && head == 0 && size == 0) |
| 1140 |
+ |
|| head < capacity); |
| 1141 |
+ |
assert size == 0 |
| 1142 |
+ |
|| (elements[head] != null && elements[tail()] != null); |
| 1143 |
+ |
assert size == capacity |
| 1144 |
+ |
|| (elements[dec(head, capacity)] == null |
| 1145 |
+ |
&& elements[inc(tail(), capacity)] == null); |
| 1146 |
+ |
} catch (Throwable t) { |
| 1147 |
+ |
System.err.printf("head=%d size=%d capacity=%d%n", |
| 1148 |
+ |
head, size, elements.length); |
| 1149 |
+ |
System.err.printf("elements=%s%n", |
| 1150 |
+ |
Arrays.toString(elements)); |
| 1151 |
+ |
throw t; |
| 1152 |
+ |
} |
| 1153 |
+ |
} |
| 1154 |
+ |
|
| 1155 |
|
} |
