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/* |
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* Written by Josh Bloch of Google Inc. and released to the public domain, |
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* as explained at http://creativecommons.org/publicdomain/zero/1.0/. |
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*/ |
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|
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package java.util; |
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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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// OPENJDK import jdk.internal.access.SharedSecrets; |
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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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* deques have no capacity restrictions; they grow as necessary to support |
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* usage. They are not thread-safe; in the absence of external |
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* synchronization, they do not support concurrent access by multiple threads. |
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* Null elements are prohibited. This class is likely to be faster than |
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* {@link Stack} when used as a stack, and faster than {@link LinkedList} |
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* when used as a queue. |
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* |
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* <p>Most {@code ArrayDeque} operations run in amortized constant time. |
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* Exceptions include |
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* {@link #remove(Object) remove}, |
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* {@link #removeFirstOccurrence removeFirstOccurrence}, |
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* {@link #removeLastOccurrence removeLastOccurrence}, |
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* {@link #contains contains}, |
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* {@link #iterator iterator.remove()}, |
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* and the bulk operations, all of which run in linear time. |
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* |
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* <p>The iterators returned by this class's {@link #iterator() iterator} |
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* method are <em>fail-fast</em>: If the deque is modified at any time after |
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* the iterator is created, in any way except through the iterator's own |
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* {@code remove} method, the iterator will generally throw a {@link |
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* ConcurrentModificationException}. Thus, in the face of concurrent |
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* modification, the iterator fails quickly and cleanly, rather than risking |
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* arbitrary, non-deterministic behavior at an undetermined time in the |
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* future. |
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* |
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
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* as it is, generally speaking, impossible to make any hard guarantees in the |
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* presence of unsynchronized concurrent modification. Fail-fast iterators |
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* throw {@code ConcurrentModificationException} on a best-effort basis. |
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* Therefore, it would be wrong to write a program that depended on this |
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* exception for its correctness: <i>the fail-fast behavior of iterators |
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* should be used only to detect bugs.</i> |
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* |
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* <p>This class and its iterator implement all of the |
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* <em>optional</em> methods of the {@link Collection} and {@link |
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* Iterator} interfaces. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> |
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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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*/ |
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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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* VMs excel at optimizing simple array loops where indices are |
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* incrementing or decrementing over a valid slice, e.g. |
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* |
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* for (int i = start; i < end; i++) ... elements[i] |
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* |
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* Because in a circular array, elements are in general stored in |
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* two disjoint such slices, we help the VM by writing unusual |
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* nested loops for all traversals over the elements. Having only |
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* one hot inner loop body instead of two or three eases human |
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* maintenance and encourages VM loop inlining into the caller. |
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*/ |
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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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* All array cells not holding deque elements are always null. |
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* The array always has at least one null slot (at tail). |
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*/ |
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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 0 <= head < elements.length equal to tail if |
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* the deque is empty. |
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*/ |
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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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* elements[tail] is always null. |
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*/ |
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transient int tail; |
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|
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/** |
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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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final int oldCapacity = elements.length; |
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int newCapacity; |
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// Double capacity 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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final Object[] es = elements = Arrays.copyOf(elements, newCapacity); |
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// Exceptionally, here tail == head needs to be disambiguated |
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if (tail < head || (tail == head && es[head] != null)) { |
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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(es, head, |
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es, head + newSpace, |
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oldCapacity - head); |
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for (int i = head, to = (head += newSpace); i < to; i++) |
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es[i] = null; |
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} |
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// checkInvariants(); |
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} |
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|
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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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final int oldCapacity = elements.length, 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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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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/** |
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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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/* public */ void ensureCapacity(int minCapacity) { |
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int needed; |
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if ((needed = (minCapacity + 1 - elements.length)) > 0) |
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grow(needed); |
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// checkInvariants(); |
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} |
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|
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/** |
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* Minimizes the internal storage of this collection. |
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* |
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* @since TBD |
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*/ |
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/* public */ void trimToSize() { |
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int size; |
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if ((size = size()) + 1 < elements.length) { |
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elements = toArray(new Object[size + 1]); |
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head = 0; |
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tail = size; |
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} |
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// checkInvariants(); |
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} |
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|
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/** |
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* Constructs an empty array deque with an initial capacity |
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* sufficient to hold 16 elements. |
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*/ |
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public ArrayDeque() { |
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elements = new Object[16 + 1]; |
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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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*/ |
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public ArrayDeque(int numElements) { |
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elements = |
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new Object[(numElements < 1) ? 1 : |
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(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE : |
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numElements + 1]; |
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} |
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|
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/** |
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* Constructs a deque containing the elements of the specified |
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* collection, in the order they are returned by the collection's |
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* iterator. (The first element returned by the collection's |
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* iterator becomes the first element, or <i>front</i> of the |
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* deque.) |
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* |
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* @param c the collection whose elements are to be placed into the deque |
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* @throws NullPointerException if the specified collection is null |
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*/ |
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public ArrayDeque(Collection<? extends E> c) { |
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this(c.size()); |
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copyElements(c); |
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} |
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|
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/** |
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* Circularly 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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* Circularly 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 - 1; |
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return i; |
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} |
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|
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/** |
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* Circularly adds the given distance to index i, mod modulus. |
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* Precondition: 0 <= i < modulus, 0 <= distance <= modulus. |
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* @return index 0 <= i < modulus |
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*/ |
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static final int inc(int i, int distance, int modulus) { |
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if ((i += distance) - 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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* Subtracts j from i, mod modulus. |
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* Index i must be logically ahead of index j. |
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* Precondition: 0 <= i < modulus, 0 <= j < modulus. |
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* @return the "circular distance" from j to i; corner case i == j |
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* is disambiguated to "empty", returning 0. |
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*/ |
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static final int sub(int i, int j, int modulus) { |
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if ((i -= j) < 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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* This is a slight abuse of generics, accepted by javac. |
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*/ |
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@SuppressWarnings("unchecked") |
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static final <E> E elementAt(Object[] es, int i) { |
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return (E) es[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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static final <E> E nonNullElementAt(Object[] es, int i) { |
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@SuppressWarnings("unchecked") E e = (E) es[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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// addLast, pollFirst, pollLast. The other methods are defined in |
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// terms of these. |
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|
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/** |
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* Inserts the specified element at the front of this deque. |
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* |
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* @param e the element to add |
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* @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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final Object[] es = elements; |
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es[head = dec(head, es.length)] = e; |
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if (head == tail) |
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grow(1); |
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// checkInvariants(); |
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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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* |
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* <p>This method is equivalent to {@link #add}. |
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* |
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* @param e the element to add |
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* @throws NullPointerException if the specified element is null |
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*/ |
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public void addLast(E e) { |
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if (e == null) |
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throw new NullPointerException(); |
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final Object[] es = elements; |
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es[tail] = e; |
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if (head == (tail = inc(tail, es.length))) |
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grow(1); |
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// checkInvariants(); |
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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 |
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* 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 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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*/ |
323 |
public boolean addAll(Collection<? extends E> c) { |
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final int s, needed; |
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if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0) |
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grow(needed); |
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copyElements(c); |
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// checkInvariants(); |
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return size() > s; |
330 |
} |
331 |
|
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private void copyElements(Collection<? extends E> c) { |
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c.forEach(this::addLast); |
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} |
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|
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/** |
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* Inserts the specified element at the front of this deque. |
338 |
* |
339 |
* @param e the element to add |
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* @return {@code true} (as specified by {@link Deque#offerFirst}) |
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* @throws NullPointerException if the specified element is null |
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*/ |
343 |
public boolean offerFirst(E e) { |
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addFirst(e); |
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return true; |
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} |
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|
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/** |
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* Inserts the specified element at the end of this deque. |
350 |
* |
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* @param e the element to add |
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* @return {@code true} (as specified by {@link Deque#offerLast}) |
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* @throws NullPointerException if the specified element is null |
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*/ |
355 |
public boolean offerLast(E e) { |
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addLast(e); |
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return true; |
358 |
} |
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|
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
362 |
*/ |
363 |
public E removeFirst() { |
364 |
E e = pollFirst(); |
365 |
if (e == null) |
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throw new NoSuchElementException(); |
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// checkInvariants(); |
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return e; |
369 |
} |
370 |
|
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
373 |
*/ |
374 |
public E removeLast() { |
375 |
E e = pollLast(); |
376 |
if (e == null) |
377 |
throw new NoSuchElementException(); |
378 |
// checkInvariants(); |
379 |
return e; |
380 |
} |
381 |
|
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public E pollFirst() { |
383 |
final Object[] es; |
384 |
final int h; |
385 |
E e = elementAt(es = elements, h = head); |
386 |
if (e != null) { |
387 |
es[h] = null; |
388 |
head = inc(h, es.length); |
389 |
} |
390 |
// checkInvariants(); |
391 |
return e; |
392 |
} |
393 |
|
394 |
public E pollLast() { |
395 |
final Object[] es; |
396 |
final int t; |
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E e = elementAt(es = elements, t = dec(tail, es.length)); |
398 |
if (e != null) |
399 |
es[tail = t] = null; |
400 |
// checkInvariants(); |
401 |
return e; |
402 |
} |
403 |
|
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/** |
405 |
* @throws NoSuchElementException {@inheritDoc} |
406 |
*/ |
407 |
public E getFirst() { |
408 |
E e = elementAt(elements, head); |
409 |
if (e == null) |
410 |
throw new NoSuchElementException(); |
411 |
// checkInvariants(); |
412 |
return e; |
413 |
} |
414 |
|
415 |
/** |
416 |
* @throws NoSuchElementException {@inheritDoc} |
417 |
*/ |
418 |
public E getLast() { |
419 |
final Object[] es = elements; |
420 |
E e = elementAt(es, dec(tail, es.length)); |
421 |
if (e == null) |
422 |
throw new NoSuchElementException(); |
423 |
// checkInvariants(); |
424 |
return e; |
425 |
} |
426 |
|
427 |
public E peekFirst() { |
428 |
// checkInvariants(); |
429 |
return elementAt(elements, head); |
430 |
} |
431 |
|
432 |
public E peekLast() { |
433 |
// checkInvariants(); |
434 |
final Object[] es; |
435 |
return elementAt(es = elements, dec(tail, es.length)); |
436 |
} |
437 |
|
438 |
/** |
439 |
* Removes the first occurrence of the specified element in this |
440 |
* deque (when traversing the deque from head to tail). |
441 |
* If the deque does not contain the element, it is unchanged. |
442 |
* More formally, removes the first element {@code e} such that |
443 |
* {@code o.equals(e)} (if such an element exists). |
444 |
* Returns {@code true} if this deque contained the specified element |
445 |
* (or equivalently, if this deque changed as a result of the call). |
446 |
* |
447 |
* @param o element to be removed from this deque, if present |
448 |
* @return {@code true} if the deque contained the specified element |
449 |
*/ |
450 |
public boolean removeFirstOccurrence(Object o) { |
451 |
if (o != null) { |
452 |
final Object[] es = elements; |
453 |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
454 |
; i = 0, to = end) { |
455 |
for (; i < to; i++) |
456 |
if (o.equals(es[i])) { |
457 |
delete(i); |
458 |
return true; |
459 |
} |
460 |
if (to == end) break; |
461 |
} |
462 |
} |
463 |
return false; |
464 |
} |
465 |
|
466 |
/** |
467 |
* Removes the last occurrence of the specified element in this |
468 |
* deque (when traversing the deque from head to tail). |
469 |
* If the deque does not contain the element, it is unchanged. |
470 |
* More formally, removes the last element {@code e} such that |
471 |
* {@code o.equals(e)} (if such an element exists). |
472 |
* Returns {@code true} if this deque contained the specified element |
473 |
* (or equivalently, if this deque changed as a result of the call). |
474 |
* |
475 |
* @param o element to be removed from this deque, if present |
476 |
* @return {@code true} if the deque contained the specified element |
477 |
*/ |
478 |
public boolean removeLastOccurrence(Object o) { |
479 |
if (o != null) { |
480 |
final Object[] es = elements; |
481 |
for (int i = tail, end = head, to = (i >= end) ? end : 0; |
482 |
; i = es.length, to = end) { |
483 |
for (i--; i > to - 1; i--) |
484 |
if (o.equals(es[i])) { |
485 |
delete(i); |
486 |
return true; |
487 |
} |
488 |
if (to == end) break; |
489 |
} |
490 |
} |
491 |
return false; |
492 |
} |
493 |
|
494 |
// *** Queue methods *** |
495 |
|
496 |
/** |
497 |
* Inserts the specified element at the end of this deque. |
498 |
* |
499 |
* <p>This method is equivalent to {@link #addLast}. |
500 |
* |
501 |
* @param e the element to add |
502 |
* @return {@code true} (as specified by {@link Collection#add}) |
503 |
* @throws NullPointerException if the specified element is null |
504 |
*/ |
505 |
public boolean add(E e) { |
506 |
addLast(e); |
507 |
return true; |
508 |
} |
509 |
|
510 |
/** |
511 |
* Inserts the specified element at the end of this deque. |
512 |
* |
513 |
* <p>This method is equivalent to {@link #offerLast}. |
514 |
* |
515 |
* @param e the element to add |
516 |
* @return {@code true} (as specified by {@link Queue#offer}) |
517 |
* @throws NullPointerException if the specified element is null |
518 |
*/ |
519 |
public boolean offer(E e) { |
520 |
return offerLast(e); |
521 |
} |
522 |
|
523 |
/** |
524 |
* Retrieves and removes the head of the queue represented by this deque. |
525 |
* |
526 |
* This method differs from {@link #poll() poll()} only in that it |
527 |
* throws an exception if this deque is empty. |
528 |
* |
529 |
* <p>This method is equivalent to {@link #removeFirst}. |
530 |
* |
531 |
* @return the head of the queue represented by this deque |
532 |
* @throws NoSuchElementException {@inheritDoc} |
533 |
*/ |
534 |
public E remove() { |
535 |
return removeFirst(); |
536 |
} |
537 |
|
538 |
/** |
539 |
* Retrieves and removes the head of the queue represented by this deque |
540 |
* (in other words, the first element of this deque), or returns |
541 |
* {@code null} if this deque is empty. |
542 |
* |
543 |
* <p>This method is equivalent to {@link #pollFirst}. |
544 |
* |
545 |
* @return the head of the queue represented by this deque, or |
546 |
* {@code null} if this deque is empty |
547 |
*/ |
548 |
public E poll() { |
549 |
return pollFirst(); |
550 |
} |
551 |
|
552 |
/** |
553 |
* Retrieves, but does not remove, the head of the queue represented by |
554 |
* this deque. This method differs from {@link #peek peek} only in |
555 |
* that it throws an exception if this deque is empty. |
556 |
* |
557 |
* <p>This method is equivalent to {@link #getFirst}. |
558 |
* |
559 |
* @return the head of the queue represented by this deque |
560 |
* @throws NoSuchElementException {@inheritDoc} |
561 |
*/ |
562 |
public E element() { |
563 |
return getFirst(); |
564 |
} |
565 |
|
566 |
/** |
567 |
* Retrieves, but does not remove, the head of the queue represented by |
568 |
* this deque, or returns {@code null} if this deque is empty. |
569 |
* |
570 |
* <p>This method is equivalent to {@link #peekFirst}. |
571 |
* |
572 |
* @return the head of the queue represented by this deque, or |
573 |
* {@code null} if this deque is empty |
574 |
*/ |
575 |
public E peek() { |
576 |
return peekFirst(); |
577 |
} |
578 |
|
579 |
// *** Stack methods *** |
580 |
|
581 |
/** |
582 |
* Pushes an element onto the stack represented by this deque. In other |
583 |
* words, inserts the element at the front of this deque. |
584 |
* |
585 |
* <p>This method is equivalent to {@link #addFirst}. |
586 |
* |
587 |
* @param e the element to push |
588 |
* @throws NullPointerException if the specified element is null |
589 |
*/ |
590 |
public void push(E e) { |
591 |
addFirst(e); |
592 |
} |
593 |
|
594 |
/** |
595 |
* Pops an element from the stack represented by this deque. In other |
596 |
* words, removes and returns the first element of this deque. |
597 |
* |
598 |
* <p>This method is equivalent to {@link #removeFirst()}. |
599 |
* |
600 |
* @return the element at the front of this deque (which is the top |
601 |
* of the stack represented by this deque) |
602 |
* @throws NoSuchElementException {@inheritDoc} |
603 |
*/ |
604 |
public E pop() { |
605 |
return removeFirst(); |
606 |
} |
607 |
|
608 |
/** |
609 |
* Removes the element at the specified position in the elements array. |
610 |
* This can result in forward or backwards motion of array elements. |
611 |
* We optimize for least element motion. |
612 |
* |
613 |
* <p>This method is called delete rather than remove to emphasize |
614 |
* that its semantics differ from those of {@link List#remove(int)}. |
615 |
* |
616 |
* @return true if elements near tail moved backwards |
617 |
*/ |
618 |
boolean delete(int i) { |
619 |
// checkInvariants(); |
620 |
final Object[] es = elements; |
621 |
final int capacity = es.length; |
622 |
final int h, t; |
623 |
// number of elements before to-be-deleted elt |
624 |
final int front = sub(i, h = head, capacity); |
625 |
// number of elements after to-be-deleted elt |
626 |
final int back = sub(t = tail, i, capacity) - 1; |
627 |
if (front < back) { |
628 |
// move front elements forwards |
629 |
if (h <= i) { |
630 |
System.arraycopy(es, h, es, h + 1, front); |
631 |
} else { // Wrap around |
632 |
System.arraycopy(es, 0, es, 1, i); |
633 |
es[0] = es[capacity - 1]; |
634 |
System.arraycopy(es, h, es, h + 1, front - (i + 1)); |
635 |
} |
636 |
es[h] = null; |
637 |
head = inc(h, capacity); |
638 |
// checkInvariants(); |
639 |
return false; |
640 |
} else { |
641 |
// move back elements backwards |
642 |
tail = dec(t, capacity); |
643 |
if (i <= tail) { |
644 |
System.arraycopy(es, i + 1, es, i, back); |
645 |
} else { // Wrap around |
646 |
System.arraycopy(es, i + 1, es, i, capacity - (i + 1)); |
647 |
es[capacity - 1] = es[0]; |
648 |
System.arraycopy(es, 1, es, 0, t - 1); |
649 |
} |
650 |
es[tail] = null; |
651 |
// checkInvariants(); |
652 |
return true; |
653 |
} |
654 |
} |
655 |
|
656 |
// *** Collection Methods *** |
657 |
|
658 |
/** |
659 |
* Returns the number of elements in this deque. |
660 |
* |
661 |
* @return the number of elements in this deque |
662 |
*/ |
663 |
public int size() { |
664 |
return sub(tail, head, elements.length); |
665 |
} |
666 |
|
667 |
/** |
668 |
* Returns {@code true} if this deque contains no elements. |
669 |
* |
670 |
* @return {@code true} if this deque contains no elements |
671 |
*/ |
672 |
public boolean isEmpty() { |
673 |
return head == tail; |
674 |
} |
675 |
|
676 |
/** |
677 |
* Returns an iterator over the elements in this deque. The elements |
678 |
* will be ordered from first (head) to last (tail). This is the same |
679 |
* order that elements would be dequeued (via successive calls to |
680 |
* {@link #remove} or popped (via successive calls to {@link #pop}). |
681 |
* |
682 |
* @return an iterator over the elements in this deque |
683 |
*/ |
684 |
public Iterator<E> iterator() { |
685 |
return new DeqIterator(); |
686 |
} |
687 |
|
688 |
public Iterator<E> descendingIterator() { |
689 |
return new DescendingIterator(); |
690 |
} |
691 |
|
692 |
private class DeqIterator implements Iterator<E> { |
693 |
/** Index of element to be returned by subsequent call to next. */ |
694 |
int cursor; |
695 |
|
696 |
/** Number of elements yet to be returned. */ |
697 |
int remaining = size(); |
698 |
|
699 |
/** |
700 |
* Index of element returned by most recent call to next. |
701 |
* Reset to -1 if element is deleted by a call to remove. |
702 |
*/ |
703 |
int lastRet = -1; |
704 |
|
705 |
DeqIterator() { cursor = head; } |
706 |
|
707 |
public final boolean hasNext() { |
708 |
return remaining > 0; |
709 |
} |
710 |
|
711 |
public E next() { |
712 |
if (remaining <= 0) |
713 |
throw new NoSuchElementException(); |
714 |
final Object[] es = elements; |
715 |
E e = nonNullElementAt(es, cursor); |
716 |
cursor = inc(lastRet = cursor, es.length); |
717 |
remaining--; |
718 |
return e; |
719 |
} |
720 |
|
721 |
void postDelete(boolean leftShifted) { |
722 |
if (leftShifted) |
723 |
cursor = dec(cursor, elements.length); |
724 |
} |
725 |
|
726 |
public final void remove() { |
727 |
if (lastRet < 0) |
728 |
throw new IllegalStateException(); |
729 |
postDelete(delete(lastRet)); |
730 |
lastRet = -1; |
731 |
} |
732 |
|
733 |
public void forEachRemaining(Consumer<? super E> action) { |
734 |
Objects.requireNonNull(action); |
735 |
int r; |
736 |
if ((r = remaining) <= 0) |
737 |
return; |
738 |
remaining = 0; |
739 |
final Object[] es = elements; |
740 |
if (es[cursor] == null || sub(tail, cursor, es.length) != r) |
741 |
throw new ConcurrentModificationException(); |
742 |
for (int i = cursor, end = tail, to = (i <= end) ? end : es.length; |
743 |
; i = 0, to = end) { |
744 |
for (; i < to; i++) |
745 |
action.accept(elementAt(es, i)); |
746 |
if (to == end) { |
747 |
if (end != tail) |
748 |
throw new ConcurrentModificationException(); |
749 |
lastRet = dec(end, es.length); |
750 |
break; |
751 |
} |
752 |
} |
753 |
} |
754 |
} |
755 |
|
756 |
private class DescendingIterator extends DeqIterator { |
757 |
DescendingIterator() { cursor = dec(tail, elements.length); } |
758 |
|
759 |
public final E next() { |
760 |
if (remaining <= 0) |
761 |
throw new NoSuchElementException(); |
762 |
final Object[] es = elements; |
763 |
E e = nonNullElementAt(es, cursor); |
764 |
cursor = dec(lastRet = cursor, es.length); |
765 |
remaining--; |
766 |
return e; |
767 |
} |
768 |
|
769 |
void postDelete(boolean leftShifted) { |
770 |
if (!leftShifted) |
771 |
cursor = inc(cursor, elements.length); |
772 |
} |
773 |
|
774 |
public final void forEachRemaining(Consumer<? super E> action) { |
775 |
Objects.requireNonNull(action); |
776 |
int r; |
777 |
if ((r = remaining) <= 0) |
778 |
return; |
779 |
remaining = 0; |
780 |
final Object[] es = elements; |
781 |
if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r) |
782 |
throw new ConcurrentModificationException(); |
783 |
for (int i = cursor, end = head, to = (i >= end) ? end : 0; |
784 |
; i = es.length - 1, to = end) { |
785 |
// hotspot generates faster code than for: i >= to ! |
786 |
for (; i > to - 1; i--) |
787 |
action.accept(elementAt(es, i)); |
788 |
if (to == end) { |
789 |
if (end != head) |
790 |
throw new ConcurrentModificationException(); |
791 |
lastRet = end; |
792 |
break; |
793 |
} |
794 |
} |
795 |
} |
796 |
} |
797 |
|
798 |
/** |
799 |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
800 |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
801 |
* deque. |
802 |
* |
803 |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
804 |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
805 |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
806 |
* the reporting of additional characteristic values. |
807 |
* |
808 |
* @return a {@code Spliterator} over the elements in this deque |
809 |
* @since 1.8 |
810 |
*/ |
811 |
public Spliterator<E> spliterator() { |
812 |
return new DeqSpliterator(); |
813 |
} |
814 |
|
815 |
final class DeqSpliterator implements Spliterator<E> { |
816 |
private int fence; // -1 until first use |
817 |
private int cursor; // current index, modified on traverse/split |
818 |
|
819 |
/** Constructs late-binding spliterator over all elements. */ |
820 |
DeqSpliterator() { |
821 |
this.fence = -1; |
822 |
} |
823 |
|
824 |
/** Constructs spliterator over the given range. */ |
825 |
DeqSpliterator(int origin, int fence) { |
826 |
// assert 0 <= origin && origin < elements.length; |
827 |
// assert 0 <= fence && fence < elements.length; |
828 |
this.cursor = origin; |
829 |
this.fence = fence; |
830 |
} |
831 |
|
832 |
/** Ensures late-binding initialization; then returns fence. */ |
833 |
private int getFence() { // force initialization |
834 |
int t; |
835 |
if ((t = fence) < 0) { |
836 |
t = fence = tail; |
837 |
cursor = head; |
838 |
} |
839 |
return t; |
840 |
} |
841 |
|
842 |
public DeqSpliterator trySplit() { |
843 |
final Object[] es = elements; |
844 |
final int i, n; |
845 |
return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0) |
846 |
? null |
847 |
: new DeqSpliterator(i, cursor = inc(i, n, es.length)); |
848 |
} |
849 |
|
850 |
public void forEachRemaining(Consumer<? super E> action) { |
851 |
if (action == null) |
852 |
throw new NullPointerException(); |
853 |
final int end = getFence(), cursor = this.cursor; |
854 |
final Object[] es = elements; |
855 |
if (cursor != end) { |
856 |
this.cursor = end; |
857 |
// null check at both ends of range is sufficient |
858 |
if (es[cursor] == null || es[dec(end, es.length)] == null) |
859 |
throw new ConcurrentModificationException(); |
860 |
for (int i = cursor, to = (i <= end) ? end : es.length; |
861 |
; i = 0, to = end) { |
862 |
for (; i < to; i++) |
863 |
action.accept(elementAt(es, i)); |
864 |
if (to == end) break; |
865 |
} |
866 |
} |
867 |
} |
868 |
|
869 |
public boolean tryAdvance(Consumer<? super E> action) { |
870 |
Objects.requireNonNull(action); |
871 |
final Object[] es = elements; |
872 |
if (fence < 0) { fence = tail; cursor = head; } // late-binding |
873 |
final int i; |
874 |
if ((i = cursor) == fence) |
875 |
return false; |
876 |
E e = nonNullElementAt(es, i); |
877 |
cursor = inc(i, es.length); |
878 |
action.accept(e); |
879 |
return true; |
880 |
} |
881 |
|
882 |
public long estimateSize() { |
883 |
return sub(getFence(), cursor, elements.length); |
884 |
} |
885 |
|
886 |
public int characteristics() { |
887 |
return Spliterator.NONNULL |
888 |
| Spliterator.ORDERED |
889 |
| Spliterator.SIZED |
890 |
| Spliterator.SUBSIZED; |
891 |
} |
892 |
} |
893 |
|
894 |
/** |
895 |
* @throws NullPointerException {@inheritDoc} |
896 |
*/ |
897 |
public void forEach(Consumer<? super E> action) { |
898 |
Objects.requireNonNull(action); |
899 |
final Object[] es = elements; |
900 |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
901 |
; i = 0, to = end) { |
902 |
for (; i < to; i++) |
903 |
action.accept(elementAt(es, i)); |
904 |
if (to == end) { |
905 |
if (end != tail) throw new ConcurrentModificationException(); |
906 |
break; |
907 |
} |
908 |
} |
909 |
// checkInvariants(); |
910 |
} |
911 |
|
912 |
/** |
913 |
* Replaces each element of this deque with the result of applying the |
914 |
* operator to that element, as specified by {@link List#replaceAll}. |
915 |
* |
916 |
* @param operator the operator to apply to each element |
917 |
* @since TBD |
918 |
*/ |
919 |
/* public */ void replaceAll(java.util.function.UnaryOperator<E> operator) { |
920 |
Objects.requireNonNull(operator); |
921 |
final Object[] es = elements; |
922 |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
923 |
; i = 0, to = end) { |
924 |
for (; i < to; i++) |
925 |
es[i] = operator.apply(elementAt(es, i)); |
926 |
if (to == end) { |
927 |
if (end != tail) throw new ConcurrentModificationException(); |
928 |
break; |
929 |
} |
930 |
} |
931 |
// checkInvariants(); |
932 |
} |
933 |
|
934 |
/** |
935 |
* @throws NullPointerException {@inheritDoc} |
936 |
*/ |
937 |
public boolean removeIf(Predicate<? super E> filter) { |
938 |
Objects.requireNonNull(filter); |
939 |
return bulkRemove(filter); |
940 |
} |
941 |
|
942 |
/** |
943 |
* @throws NullPointerException {@inheritDoc} |
944 |
*/ |
945 |
public boolean removeAll(Collection<?> c) { |
946 |
Objects.requireNonNull(c); |
947 |
return bulkRemove(e -> c.contains(e)); |
948 |
} |
949 |
|
950 |
/** |
951 |
* @throws NullPointerException {@inheritDoc} |
952 |
*/ |
953 |
public boolean retainAll(Collection<?> c) { |
954 |
Objects.requireNonNull(c); |
955 |
return bulkRemove(e -> !c.contains(e)); |
956 |
} |
957 |
|
958 |
/** Implementation of bulk remove methods. */ |
959 |
private boolean bulkRemove(Predicate<? super E> filter) { |
960 |
// checkInvariants(); |
961 |
final Object[] es = elements; |
962 |
// Optimize for initial run of survivors |
963 |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
964 |
; i = 0, to = end) { |
965 |
for (; i < to; i++) |
966 |
if (filter.test(elementAt(es, i))) |
967 |
return bulkRemoveModified(filter, i); |
968 |
if (to == end) { |
969 |
if (end != tail) throw new ConcurrentModificationException(); |
970 |
break; |
971 |
} |
972 |
} |
973 |
return false; |
974 |
} |
975 |
|
976 |
// A tiny bit set implementation |
977 |
|
978 |
private static long[] nBits(int n) { |
979 |
return new long[((n - 1) >> 6) + 1]; |
980 |
} |
981 |
private static void setBit(long[] bits, int i) { |
982 |
bits[i >> 6] |= 1L << i; |
983 |
} |
984 |
private static boolean isClear(long[] bits, int i) { |
985 |
return (bits[i >> 6] & (1L << i)) == 0; |
986 |
} |
987 |
|
988 |
/** |
989 |
* Helper for bulkRemove, in case of at least one deletion. |
990 |
* Tolerate predicates that reentrantly access the collection for |
991 |
* read (but writers still get CME), so traverse once to find |
992 |
* elements to delete, a second pass to physically expunge. |
993 |
* |
994 |
* @param beg valid index of first element to be deleted |
995 |
*/ |
996 |
private boolean bulkRemoveModified( |
997 |
Predicate<? super E> filter, final int beg) { |
998 |
final Object[] es = elements; |
999 |
final int capacity = es.length; |
1000 |
final int end = tail; |
1001 |
final long[] deathRow = nBits(sub(end, beg, capacity)); |
1002 |
deathRow[0] = 1L; // set bit 0 |
1003 |
for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
1004 |
; i = 0, to = end, k -= capacity) { |
1005 |
for (; i < to; i++) |
1006 |
if (filter.test(elementAt(es, i))) |
1007 |
setBit(deathRow, i - k); |
1008 |
if (to == end) break; |
1009 |
} |
1010 |
// a two-finger traversal, with hare i reading, tortoise w writing |
1011 |
int w = beg; |
1012 |
for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
1013 |
; w = 0) { // w rejoins i on second leg |
1014 |
// In this loop, i and w are on the same leg, with i > w |
1015 |
for (; i < to; i++) |
1016 |
if (isClear(deathRow, i - k)) |
1017 |
es[w++] = es[i]; |
1018 |
if (to == end) break; |
1019 |
// In this loop, w is on the first leg, i on the second |
1020 |
for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++) |
1021 |
if (isClear(deathRow, i - k)) |
1022 |
es[w++] = es[i]; |
1023 |
if (i >= to) { |
1024 |
if (w == capacity) w = 0; // "corner" case |
1025 |
break; |
1026 |
} |
1027 |
} |
1028 |
if (end != tail) throw new ConcurrentModificationException(); |
1029 |
circularClear(es, tail = w, end); |
1030 |
// checkInvariants(); |
1031 |
return true; |
1032 |
} |
1033 |
|
1034 |
/** |
1035 |
* Returns {@code true} if this deque contains the specified element. |
1036 |
* More formally, returns {@code true} if and only if this deque contains |
1037 |
* at least one element {@code e} such that {@code o.equals(e)}. |
1038 |
* |
1039 |
* @param o object to be checked for containment in this deque |
1040 |
* @return {@code true} if this deque contains the specified element |
1041 |
*/ |
1042 |
public boolean contains(Object o) { |
1043 |
if (o != null) { |
1044 |
final Object[] es = elements; |
1045 |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
1046 |
; i = 0, to = end) { |
1047 |
for (; i < to; i++) |
1048 |
if (o.equals(es[i])) |
1049 |
return true; |
1050 |
if (to == end) break; |
1051 |
} |
1052 |
} |
1053 |
return false; |
1054 |
} |
1055 |
|
1056 |
/** |
1057 |
* Removes a single instance of the specified element from this deque. |
1058 |
* If the deque does not contain the element, it is unchanged. |
1059 |
* More formally, removes the first element {@code e} such that |
1060 |
* {@code o.equals(e)} (if such an element exists). |
1061 |
* Returns {@code true} if this deque contained the specified element |
1062 |
* (or equivalently, if this deque changed as a result of the call). |
1063 |
* |
1064 |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
1065 |
* |
1066 |
* @param o element to be removed from this deque, if present |
1067 |
* @return {@code true} if this deque contained the specified element |
1068 |
*/ |
1069 |
public boolean remove(Object o) { |
1070 |
return removeFirstOccurrence(o); |
1071 |
} |
1072 |
|
1073 |
/** |
1074 |
* Removes all of the elements from this deque. |
1075 |
* The deque will be empty after this call returns. |
1076 |
*/ |
1077 |
public void clear() { |
1078 |
circularClear(elements, head, tail); |
1079 |
head = tail = 0; |
1080 |
// checkInvariants(); |
1081 |
} |
1082 |
|
1083 |
/** |
1084 |
* Nulls out slots starting at array index i, upto index end. |
1085 |
* Condition i == end means "empty" - nothing to do. |
1086 |
*/ |
1087 |
private static void circularClear(Object[] es, int i, int end) { |
1088 |
// assert 0 <= i && i < es.length; |
1089 |
// assert 0 <= end && end < es.length; |
1090 |
for (int to = (i <= end) ? end : es.length; |
1091 |
; i = 0, to = end) { |
1092 |
for (; i < to; i++) es[i] = null; |
1093 |
if (to == end) break; |
1094 |
} |
1095 |
} |
1096 |
|
1097 |
/** |
1098 |
* Returns an array containing all of the elements in this deque |
1099 |
* in proper sequence (from first to last element). |
1100 |
* |
1101 |
* <p>The returned array will be "safe" in that no references to it are |
1102 |
* maintained by this deque. (In other words, this method must allocate |
1103 |
* a new array). The caller is thus free to modify the returned array. |
1104 |
* |
1105 |
* <p>This method acts as bridge between array-based and collection-based |
1106 |
* APIs. |
1107 |
* |
1108 |
* @return an array containing all of the elements in this deque |
1109 |
*/ |
1110 |
public Object[] toArray() { |
1111 |
return toArray(Object[].class); |
1112 |
} |
1113 |
|
1114 |
private <T> T[] toArray(Class<T[]> klazz) { |
1115 |
final Object[] es = elements; |
1116 |
final T[] a; |
1117 |
final int head = this.head, tail = this.tail, end; |
1118 |
if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) { |
1119 |
// Uses null extension feature of copyOfRange |
1120 |
a = Arrays.copyOfRange(es, head, end, klazz); |
1121 |
} else { |
1122 |
// integer overflow! |
1123 |
a = Arrays.copyOfRange(es, 0, end - head, klazz); |
1124 |
System.arraycopy(es, head, a, 0, es.length - head); |
1125 |
} |
1126 |
if (end != tail) |
1127 |
System.arraycopy(es, 0, a, es.length - head, tail); |
1128 |
return a; |
1129 |
} |
1130 |
|
1131 |
/** |
1132 |
* Returns an array containing all of the elements in this deque in |
1133 |
* proper sequence (from first to last element); the runtime type of the |
1134 |
* returned array is that of the specified array. If the deque fits in |
1135 |
* the specified array, it is returned therein. Otherwise, a new array |
1136 |
* is allocated with the runtime type of the specified array and the |
1137 |
* size of this deque. |
1138 |
* |
1139 |
* <p>If this deque fits in the specified array with room to spare |
1140 |
* (i.e., the array has more elements than this deque), the element in |
1141 |
* the array immediately following the end of the deque is set to |
1142 |
* {@code null}. |
1143 |
* |
1144 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
1145 |
* array-based and collection-based APIs. Further, this method allows |
1146 |
* precise control over the runtime type of the output array, and may, |
1147 |
* under certain circumstances, be used to save allocation costs. |
1148 |
* |
1149 |
* <p>Suppose {@code x} is a deque known to contain only strings. |
1150 |
* The following code can be used to dump the deque into a newly |
1151 |
* allocated array of {@code String}: |
1152 |
* |
1153 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
1154 |
* |
1155 |
* Note that {@code toArray(new Object[0])} is identical in function to |
1156 |
* {@code toArray()}. |
1157 |
* |
1158 |
* @param a the array into which the elements of the deque are to |
1159 |
* be stored, if it is big enough; otherwise, a new array of the |
1160 |
* same runtime type is allocated for this purpose |
1161 |
* @return an array containing all of the elements in this deque |
1162 |
* @throws ArrayStoreException if the runtime type of the specified array |
1163 |
* is not a supertype of the runtime type of every element in |
1164 |
* this deque |
1165 |
* @throws NullPointerException if the specified array is null |
1166 |
*/ |
1167 |
@SuppressWarnings("unchecked") |
1168 |
public <T> T[] toArray(T[] a) { |
1169 |
final int size; |
1170 |
if ((size = size()) > a.length) |
1171 |
return toArray((Class<T[]>) a.getClass()); |
1172 |
final Object[] es = elements; |
1173 |
for (int i = head, j = 0, len = Math.min(size, es.length - i); |
1174 |
; i = 0, len = tail) { |
1175 |
System.arraycopy(es, i, a, j, len); |
1176 |
if ((j += len) == size) break; |
1177 |
} |
1178 |
if (size < a.length) |
1179 |
a[size] = null; |
1180 |
return a; |
1181 |
} |
1182 |
|
1183 |
// *** Object methods *** |
1184 |
|
1185 |
/** |
1186 |
* Returns a copy of this deque. |
1187 |
* |
1188 |
* @return a copy of this deque |
1189 |
*/ |
1190 |
public ArrayDeque<E> clone() { |
1191 |
try { |
1192 |
@SuppressWarnings("unchecked") |
1193 |
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
1194 |
result.elements = Arrays.copyOf(elements, elements.length); |
1195 |
return result; |
1196 |
} catch (CloneNotSupportedException e) { |
1197 |
throw new AssertionError(); |
1198 |
} |
1199 |
} |
1200 |
|
1201 |
// OPENJDK @java.io.Serial |
1202 |
private static final long serialVersionUID = 2340985798034038923L; |
1203 |
|
1204 |
/** |
1205 |
* Saves this deque to a stream (that is, serializes it). |
1206 |
* |
1207 |
* @param s the stream |
1208 |
* @throws java.io.IOException if an I/O error occurs |
1209 |
* @serialData The current size ({@code int}) of the deque, |
1210 |
* followed by all of its elements (each an object reference) in |
1211 |
* first-to-last order. |
1212 |
*/ |
1213 |
// OPENJDK @java.io.Serial |
1214 |
private void writeObject(java.io.ObjectOutputStream s) |
1215 |
throws java.io.IOException { |
1216 |
s.defaultWriteObject(); |
1217 |
|
1218 |
// Write out size |
1219 |
s.writeInt(size()); |
1220 |
|
1221 |
// Write out elements in order. |
1222 |
final Object[] es = elements; |
1223 |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
1224 |
; i = 0, to = end) { |
1225 |
for (; i < to; i++) |
1226 |
s.writeObject(es[i]); |
1227 |
if (to == end) break; |
1228 |
} |
1229 |
} |
1230 |
|
1231 |
/** |
1232 |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1233 |
* @param s the stream |
1234 |
* @throws ClassNotFoundException if the class of a serialized object |
1235 |
* could not be found |
1236 |
* @throws java.io.IOException if an I/O error occurs |
1237 |
*/ |
1238 |
// OPENJDK @java.io.Serial |
1239 |
private void readObject(java.io.ObjectInputStream s) |
1240 |
throws java.io.IOException, ClassNotFoundException { |
1241 |
s.defaultReadObject(); |
1242 |
|
1243 |
// Read in size and allocate array |
1244 |
int size = s.readInt(); |
1245 |
jsr166.Platform.checkArray(s, Object[].class, size + 1); |
1246 |
elements = new Object[size + 1]; |
1247 |
this.tail = size; |
1248 |
|
1249 |
// Read in all elements in the proper order. |
1250 |
for (int i = 0; i < size; i++) |
1251 |
elements[i] = s.readObject(); |
1252 |
} |
1253 |
|
1254 |
/** debugging */ |
1255 |
void checkInvariants() { |
1256 |
// Use head and tail fields with empty slot at tail strategy. |
1257 |
// head == tail disambiguates to "empty". |
1258 |
try { |
1259 |
int capacity = elements.length; |
1260 |
// assert 0 <= head && head < capacity; |
1261 |
// assert 0 <= tail && tail < capacity; |
1262 |
// assert capacity > 0; |
1263 |
// assert size() < capacity; |
1264 |
// assert head == tail || elements[head] != null; |
1265 |
// assert elements[tail] == null; |
1266 |
// assert head == tail || elements[dec(tail, capacity)] != null; |
1267 |
} catch (Throwable t) { |
1268 |
System.err.printf("head=%d tail=%d capacity=%d%n", |
1269 |
head, tail, elements.length); |
1270 |
System.err.printf("elements=%s%n", |
1271 |
Arrays.toString(elements)); |
1272 |
throw t; |
1273 |
} |
1274 |
} |
1275 |
|
1276 |
} |