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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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import java.util.function.UnaryOperator; |
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|
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/** |
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* Resizable-array implementation of the {@link Deque} interface. Array |
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* 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}/../technotes/guides/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @author Josh Bloch and Doug Lea |
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* @param <E> the type of elements held in this deque |
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* @since 1.6 |
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*/ |
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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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* 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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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 if the deque is empty. |
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*/ |
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transient int head; |
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|
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/** Number of elements in this collection. */ |
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transient int size; |
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|
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/** |
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* 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 Object[] grow(int needed) { |
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// overflow-conscious code |
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// checkInvariants(); |
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final 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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return elements; |
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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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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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* 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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if (size < elements.length) { |
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elements = toArray(); |
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head = 0; |
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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]; |
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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 = new Object[numElements]; |
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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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Object[] es = c.toArray(); |
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// defend against c.toArray (incorrectly) not returning Object[] |
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// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652) |
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if (es.getClass() != Object[].class) |
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es = Arrays.copyOf(es, es.length, Object[].class); |
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for (Object obj : es) |
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Objects.requireNonNull(obj); |
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this.elements = es; |
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this.size = es.length; |
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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 - 1; |
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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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private 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. It's a little |
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* surprising that javac allows this abuse of generics. |
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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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// checkInvariants(); |
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Objects.requireNonNull(e); |
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Object[] es; |
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int capacity, h; |
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final int s; |
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if ((s = size) == (capacity = (es = elements).length)) |
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capacity = (es = grow(1)).length; |
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if ((h = head - 1) < 0) h = capacity - 1; |
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es[head = h] = 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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/** |
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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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// checkInvariants(); |
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Objects.requireNonNull(e); |
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Object[] es; |
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int capacity; |
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final int s; |
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if ((s = size) == (capacity = (es = elements).length)) |
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capacity = (es = grow(1)).length; |
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es[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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|
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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 |
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* iterator. |
304 |
* |
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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 |
307 |
* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
309 |
*/ |
310 |
public boolean addAll(Collection<? extends E> c) { |
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final int s = size, needed = c.size() - (elements.length - s); |
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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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} |
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|
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/** |
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* Inserts the specified element at the front of this deque. |
321 |
* |
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* @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 |
325 |
*/ |
326 |
public boolean offerFirst(E e) { |
327 |
addFirst(e); |
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return true; |
329 |
} |
330 |
|
331 |
/** |
332 |
* Inserts the specified element at the end of this deque. |
333 |
* |
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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 |
337 |
*/ |
338 |
public boolean offerLast(E e) { |
339 |
addLast(e); |
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return true; |
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} |
342 |
|
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
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*/ |
346 |
public E removeFirst() { |
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// checkInvariants(); |
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E e = pollFirst(); |
349 |
if (e == null) |
350 |
throw new NoSuchElementException(); |
351 |
return e; |
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} |
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|
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
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*/ |
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public E removeLast() { |
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// checkInvariants(); |
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E e = pollLast(); |
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if (e == null) |
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throw new NoSuchElementException(); |
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return e; |
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} |
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|
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public E pollFirst() { |
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// checkInvariants(); |
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int s, h; |
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if ((s = size) <= 0) |
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return null; |
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final Object[] es = elements; |
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@SuppressWarnings("unchecked") E e = (E) es[h = head]; |
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es[h] = null; |
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if (++h >= es.length) h = 0; |
374 |
head = h; |
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size = s - 1; |
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return e; |
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} |
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|
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public E pollLast() { |
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// checkInvariants(); |
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final int s, tail; |
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if ((s = size) <= 0) |
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return null; |
384 |
final Object[] es = elements; |
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@SuppressWarnings("unchecked") |
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E e = (E) es[tail = add(head, s - 1, es.length)]; |
387 |
es[tail] = null; |
388 |
size = s - 1; |
389 |
return e; |
390 |
} |
391 |
|
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/** |
393 |
* @throws NoSuchElementException {@inheritDoc} |
394 |
*/ |
395 |
public E getFirst() { |
396 |
// checkInvariants(); |
397 |
if (size <= 0) throw new NoSuchElementException(); |
398 |
return elementAt(head); |
399 |
} |
400 |
|
401 |
/** |
402 |
* @throws NoSuchElementException {@inheritDoc} |
403 |
*/ |
404 |
@SuppressWarnings("unchecked") |
405 |
public E getLast() { |
406 |
// checkInvariants(); |
407 |
final int s; |
408 |
if ((s = size) <= 0) throw new NoSuchElementException(); |
409 |
final Object[] es = elements; |
410 |
return (E) es[add(head, s - 1, es.length)]; |
411 |
} |
412 |
|
413 |
public E peekFirst() { |
414 |
// checkInvariants(); |
415 |
return (size <= 0) ? null : elementAt(head); |
416 |
} |
417 |
|
418 |
@SuppressWarnings("unchecked") |
419 |
public E peekLast() { |
420 |
// checkInvariants(); |
421 |
final int s; |
422 |
if ((s = size) <= 0) return null; |
423 |
final Object[] es = elements; |
424 |
return (E) es[add(head, s - 1, es.length)]; |
425 |
} |
426 |
|
427 |
/** |
428 |
* Removes the first occurrence of the specified element in this |
429 |
* deque (when traversing the deque from head to tail). |
430 |
* If the deque does not contain the element, it is unchanged. |
431 |
* More formally, removes the first element {@code e} such that |
432 |
* {@code o.equals(e)} (if such an element exists). |
433 |
* Returns {@code true} if this deque contained the specified element |
434 |
* (or equivalently, if this deque changed as a result of the call). |
435 |
* |
436 |
* @param o element to be removed from this deque, if present |
437 |
* @return {@code true} if the deque contained the specified element |
438 |
*/ |
439 |
public boolean removeFirstOccurrence(Object o) { |
440 |
if (o != null) { |
441 |
final Object[] es = elements; |
442 |
int i, end, to, todo; |
443 |
todo = (end = (i = head) + size) |
444 |
- (to = (es.length - end >= 0) ? end : es.length); |
445 |
for (;; to = todo, todo = 0, i = 0) { |
446 |
for (; i < to; i++) |
447 |
if (o.equals(es[i])) { |
448 |
delete(i); |
449 |
return true; |
450 |
} |
451 |
if (todo == 0) break; |
452 |
} |
453 |
} |
454 |
return false; |
455 |
} |
456 |
|
457 |
/** |
458 |
* Removes the last occurrence of the specified element in this |
459 |
* deque (when traversing the deque from head to tail). |
460 |
* If the deque does not contain the element, it is unchanged. |
461 |
* More formally, removes the last element {@code e} such that |
462 |
* {@code o.equals(e)} (if such an element exists). |
463 |
* Returns {@code true} if this deque contained the specified element |
464 |
* (or equivalently, if this deque changed as a result of the call). |
465 |
* |
466 |
* @param o element to be removed from this deque, if present |
467 |
* @return {@code true} if the deque contained the specified element |
468 |
*/ |
469 |
public boolean removeLastOccurrence(Object o) { |
470 |
if (o != null) { |
471 |
final Object[] es = elements; |
472 |
int i, to, end, todo; |
473 |
todo = (to = ((end = (i = tail()) - size) >= -1) ? end : -1) - end; |
474 |
for (;; to = (i = es.length - 1) - todo, todo = 0) { |
475 |
for (; i > to; i--) |
476 |
if (o.equals(es[i])) { |
477 |
delete(i); |
478 |
return true; |
479 |
} |
480 |
if (todo == 0) break; |
481 |
} |
482 |
} |
483 |
return false; |
484 |
} |
485 |
|
486 |
// *** Queue methods *** |
487 |
|
488 |
/** |
489 |
* Inserts the specified element at the end of this deque. |
490 |
* |
491 |
* <p>This method is equivalent to {@link #addLast}. |
492 |
* |
493 |
* @param e the element to add |
494 |
* @return {@code true} (as specified by {@link Collection#add}) |
495 |
* @throws NullPointerException if the specified element is null |
496 |
*/ |
497 |
public boolean add(E e) { |
498 |
addLast(e); |
499 |
return true; |
500 |
} |
501 |
|
502 |
/** |
503 |
* Inserts the specified element at the end of this deque. |
504 |
* |
505 |
* <p>This method is equivalent to {@link #offerLast}. |
506 |
* |
507 |
* @param e the element to add |
508 |
* @return {@code true} (as specified by {@link Queue#offer}) |
509 |
* @throws NullPointerException if the specified element is null |
510 |
*/ |
511 |
public boolean offer(E e) { |
512 |
return offerLast(e); |
513 |
} |
514 |
|
515 |
/** |
516 |
* Retrieves and removes the head of the queue represented by this deque. |
517 |
* |
518 |
* This method differs from {@link #poll poll} only in that it throws an |
519 |
* exception if this deque is empty. |
520 |
* |
521 |
* <p>This method is equivalent to {@link #removeFirst}. |
522 |
* |
523 |
* @return the head of the queue represented by this deque |
524 |
* @throws NoSuchElementException {@inheritDoc} |
525 |
*/ |
526 |
public E remove() { |
527 |
return removeFirst(); |
528 |
} |
529 |
|
530 |
/** |
531 |
* Retrieves and removes the head of the queue represented by this deque |
532 |
* (in other words, the first element of this deque), or returns |
533 |
* {@code null} if this deque is empty. |
534 |
* |
535 |
* <p>This method is equivalent to {@link #pollFirst}. |
536 |
* |
537 |
* @return the head of the queue represented by this deque, or |
538 |
* {@code null} if this deque is empty |
539 |
*/ |
540 |
public E poll() { |
541 |
return pollFirst(); |
542 |
} |
543 |
|
544 |
/** |
545 |
* Retrieves, but does not remove, the head of the queue represented by |
546 |
* this deque. This method differs from {@link #peek peek} only in |
547 |
* that it throws an exception if this deque is empty. |
548 |
* |
549 |
* <p>This method is equivalent to {@link #getFirst}. |
550 |
* |
551 |
* @return the head of the queue represented by this deque |
552 |
* @throws NoSuchElementException {@inheritDoc} |
553 |
*/ |
554 |
public E element() { |
555 |
return getFirst(); |
556 |
} |
557 |
|
558 |
/** |
559 |
* Retrieves, but does not remove, the head of the queue represented by |
560 |
* this deque, or returns {@code null} if this deque is empty. |
561 |
* |
562 |
* <p>This method is equivalent to {@link #peekFirst}. |
563 |
* |
564 |
* @return the head of the queue represented by this deque, or |
565 |
* {@code null} if this deque is empty |
566 |
*/ |
567 |
public E peek() { |
568 |
return peekFirst(); |
569 |
} |
570 |
|
571 |
// *** Stack methods *** |
572 |
|
573 |
/** |
574 |
* Pushes an element onto the stack represented by this deque. In other |
575 |
* words, inserts the element at the front of this deque. |
576 |
* |
577 |
* <p>This method is equivalent to {@link #addFirst}. |
578 |
* |
579 |
* @param e the element to push |
580 |
* @throws NullPointerException if the specified element is null |
581 |
*/ |
582 |
public void push(E e) { |
583 |
addFirst(e); |
584 |
} |
585 |
|
586 |
/** |
587 |
* Pops an element from the stack represented by this deque. In other |
588 |
* words, removes and returns the first element of this deque. |
589 |
* |
590 |
* <p>This method is equivalent to {@link #removeFirst()}. |
591 |
* |
592 |
* @return the element at the front of this deque (which is the top |
593 |
* of the stack represented by this deque) |
594 |
* @throws NoSuchElementException {@inheritDoc} |
595 |
*/ |
596 |
public E pop() { |
597 |
return removeFirst(); |
598 |
} |
599 |
|
600 |
/** |
601 |
* Removes the element at the specified position in the elements array. |
602 |
* This can result in forward or backwards motion of array elements. |
603 |
* We optimize for least element motion. |
604 |
* |
605 |
* <p>This method is called delete rather than remove to emphasize |
606 |
* that its semantics differ from those of {@link List#remove(int)}. |
607 |
* |
608 |
* @return true if elements moved backwards |
609 |
*/ |
610 |
boolean delete(int i) { |
611 |
// checkInvariants(); |
612 |
final Object[] es = elements; |
613 |
final int capacity = es.length; |
614 |
final int h = head; |
615 |
int front; // number of elements before to-be-deleted elt |
616 |
if ((front = i - h) < 0) front += capacity; |
617 |
final int back = size - front - 1; // number of elements after |
618 |
if (front < back) { |
619 |
// move front elements forwards |
620 |
if (h <= i) { |
621 |
System.arraycopy(es, h, es, h + 1, front); |
622 |
} else { // Wrap around |
623 |
System.arraycopy(es, 0, es, 1, i); |
624 |
es[0] = es[capacity - 1]; |
625 |
System.arraycopy(es, h, es, h + 1, front - (i + 1)); |
626 |
} |
627 |
es[h] = null; |
628 |
if ((head = (h + 1)) >= capacity) head = 0; |
629 |
size--; |
630 |
// checkInvariants(); |
631 |
return false; |
632 |
} else { |
633 |
// move back elements backwards |
634 |
int tail = tail(); |
635 |
if (i <= tail) { |
636 |
System.arraycopy(es, i + 1, es, i, back); |
637 |
} else { // Wrap around |
638 |
int firstLeg = capacity - (i + 1); |
639 |
System.arraycopy(es, i + 1, es, i, firstLeg); |
640 |
es[capacity - 1] = es[0]; |
641 |
System.arraycopy(es, 1, es, 0, back - firstLeg - 1); |
642 |
} |
643 |
es[tail] = null; |
644 |
size--; |
645 |
// checkInvariants(); |
646 |
return true; |
647 |
} |
648 |
} |
649 |
|
650 |
// *** Collection Methods *** |
651 |
|
652 |
/** |
653 |
* Returns the number of elements in this deque. |
654 |
* |
655 |
* @return the number of elements in this deque |
656 |
*/ |
657 |
public int size() { |
658 |
return size; |
659 |
} |
660 |
|
661 |
/** |
662 |
* Returns {@code true} if this deque contains no elements. |
663 |
* |
664 |
* @return {@code true} if this deque contains no elements |
665 |
*/ |
666 |
public boolean isEmpty() { |
667 |
return size == 0; |
668 |
} |
669 |
|
670 |
/** |
671 |
* Returns an iterator over the elements in this deque. The elements |
672 |
* will be ordered from first (head) to last (tail). This is the same |
673 |
* order that elements would be dequeued (via successive calls to |
674 |
* {@link #remove} or popped (via successive calls to {@link #pop}). |
675 |
* |
676 |
* @return an iterator over the elements in this deque |
677 |
*/ |
678 |
public Iterator<E> iterator() { |
679 |
return new DeqIterator(); |
680 |
} |
681 |
|
682 |
public Iterator<E> descendingIterator() { |
683 |
return new DescendingIterator(); |
684 |
} |
685 |
|
686 |
private class DeqIterator implements Iterator<E> { |
687 |
/** Index of element to be returned by subsequent call to next. */ |
688 |
int cursor; |
689 |
|
690 |
/** Number of elements yet to be returned. */ |
691 |
int remaining = size; |
692 |
|
693 |
/** |
694 |
* Index of element returned by most recent call to next. |
695 |
* Reset to -1 if element is deleted by a call to remove. |
696 |
*/ |
697 |
int lastRet = -1; |
698 |
|
699 |
DeqIterator() { cursor = head; } |
700 |
|
701 |
public final boolean hasNext() { |
702 |
return remaining > 0; |
703 |
} |
704 |
|
705 |
public E next() { |
706 |
if (remaining <= 0) |
707 |
throw new NoSuchElementException(); |
708 |
final Object[] es = elements; |
709 |
E e = nonNullElementAt(es, cursor); |
710 |
lastRet = cursor; |
711 |
if (++cursor >= es.length) cursor = 0; |
712 |
remaining--; |
713 |
return e; |
714 |
} |
715 |
|
716 |
void postDelete(boolean leftShifted) { |
717 |
if (leftShifted) |
718 |
if (--cursor < 0) cursor = elements.length - 1; |
719 |
} |
720 |
|
721 |
public final void remove() { |
722 |
if (lastRet < 0) |
723 |
throw new IllegalStateException(); |
724 |
postDelete(delete(lastRet)); |
725 |
lastRet = -1; |
726 |
} |
727 |
|
728 |
public void forEachRemaining(Consumer<? super E> action) { |
729 |
Objects.requireNonNull(action); |
730 |
final int k; |
731 |
if ((k = remaining) > 0) { |
732 |
remaining = 0; |
733 |
ArrayDeque.forEachRemaining(action, elements, cursor, k); |
734 |
if ((lastRet = cursor + k - 1) >= elements.length) |
735 |
lastRet -= elements.length; |
736 |
} |
737 |
} |
738 |
} |
739 |
|
740 |
private class DescendingIterator extends DeqIterator { |
741 |
DescendingIterator() { cursor = tail(); } |
742 |
|
743 |
public final E next() { |
744 |
if (remaining <= 0) |
745 |
throw new NoSuchElementException(); |
746 |
final Object[] es = elements; |
747 |
E e = nonNullElementAt(es, cursor); |
748 |
lastRet = cursor; |
749 |
if (--cursor < 0) cursor = es.length - 1; |
750 |
remaining--; |
751 |
return e; |
752 |
} |
753 |
|
754 |
void postDelete(boolean leftShifted) { |
755 |
if (!leftShifted) |
756 |
if (++cursor >= elements.length) cursor = 0; |
757 |
} |
758 |
|
759 |
public final void forEachRemaining(Consumer<? super E> action) { |
760 |
Objects.requireNonNull(action); |
761 |
final int k; |
762 |
if ((k = remaining) > 0) { |
763 |
remaining = 0; |
764 |
final Object[] es = elements; |
765 |
int i, end, to, todo; |
766 |
todo = (to = ((end = (i = cursor) - k) >= -1) ? end : -1) - end; |
767 |
for (;; to = (i = es.length - 1) - todo, todo = 0) { |
768 |
for (; i > to; i--) |
769 |
action.accept(nonNullElementAt(es, i)); |
770 |
if (todo == 0) break; |
771 |
} |
772 |
if ((lastRet = cursor - (k - 1)) < 0) |
773 |
lastRet += es.length; |
774 |
} |
775 |
} |
776 |
} |
777 |
|
778 |
/** |
779 |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
780 |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
781 |
* deque. |
782 |
* |
783 |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
784 |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
785 |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
786 |
* the reporting of additional characteristic values. |
787 |
* |
788 |
* @return a {@code Spliterator} over the elements in this deque |
789 |
* @since 1.8 |
790 |
*/ |
791 |
public Spliterator<E> spliterator() { |
792 |
return new ArrayDequeSpliterator(); |
793 |
} |
794 |
|
795 |
final class ArrayDequeSpliterator implements Spliterator<E> { |
796 |
private int cursor; |
797 |
private int remaining; // -1 until late-binding first use |
798 |
|
799 |
/** Constructs late-binding spliterator over all elements. */ |
800 |
ArrayDequeSpliterator() { |
801 |
this.remaining = -1; |
802 |
} |
803 |
|
804 |
/** Constructs spliterator over the given slice. */ |
805 |
ArrayDequeSpliterator(int cursor, int count) { |
806 |
this.cursor = cursor; |
807 |
this.remaining = count; |
808 |
} |
809 |
|
810 |
/** Ensures late-binding initialization; then returns remaining. */ |
811 |
private int remaining() { |
812 |
if (remaining < 0) { |
813 |
cursor = head; |
814 |
remaining = size; |
815 |
} |
816 |
return remaining; |
817 |
} |
818 |
|
819 |
public ArrayDequeSpliterator trySplit() { |
820 |
final int mid; |
821 |
if ((mid = remaining() >> 1) > 0) { |
822 |
int oldCursor = cursor; |
823 |
cursor = add(cursor, mid, elements.length); |
824 |
remaining -= mid; |
825 |
return new ArrayDequeSpliterator(oldCursor, mid); |
826 |
} |
827 |
return null; |
828 |
} |
829 |
|
830 |
public void forEachRemaining(Consumer<? super E> action) { |
831 |
Objects.requireNonNull(action); |
832 |
final int k = remaining(); // side effect! |
833 |
remaining = 0; |
834 |
ArrayDeque.forEachRemaining(action, elements, cursor, k); |
835 |
} |
836 |
|
837 |
public boolean tryAdvance(Consumer<? super E> action) { |
838 |
Objects.requireNonNull(action); |
839 |
final int k; |
840 |
if ((k = remaining()) <= 0) |
841 |
return false; |
842 |
action.accept(nonNullElementAt(elements, cursor)); |
843 |
if (++cursor >= elements.length) cursor = 0; |
844 |
remaining = k - 1; |
845 |
return true; |
846 |
} |
847 |
|
848 |
public long estimateSize() { |
849 |
return remaining(); |
850 |
} |
851 |
|
852 |
public int characteristics() { |
853 |
return Spliterator.NONNULL |
854 |
| Spliterator.ORDERED |
855 |
| Spliterator.SIZED |
856 |
| Spliterator.SUBSIZED; |
857 |
} |
858 |
} |
859 |
|
860 |
@SuppressWarnings("unchecked") |
861 |
public void forEach(Consumer<? super E> action) { |
862 |
Objects.requireNonNull(action); |
863 |
final Object[] es = elements; |
864 |
int i, end, to, todo; |
865 |
todo = (end = (i = head) + size) |
866 |
- (to = (es.length - end >= 0) ? end : es.length); |
867 |
for (;; to = todo, todo = 0, i = 0) { |
868 |
for (; i < to; i++) |
869 |
action.accept((E) es[i]); |
870 |
if (todo == 0) break; |
871 |
} |
872 |
// checkInvariants(); |
873 |
} |
874 |
|
875 |
/** |
876 |
* Calls action on remaining elements, starting at index i and |
877 |
* traversing in ascending order. A variant of forEach that also |
878 |
* checks for concurrent modification, for use in iterators. |
879 |
*/ |
880 |
static <E> void forEachRemaining( |
881 |
Consumer<? super E> action, Object[] es, int i, int remaining) { |
882 |
int end, to, todo; |
883 |
todo = (end = i + remaining) |
884 |
- (to = (es.length - end >= 0) ? end : es.length); |
885 |
for (;; to = todo, todo = 0, i = 0) { |
886 |
for (; i < to; i++) |
887 |
action.accept(nonNullElementAt(es, i)); |
888 |
if (todo == 0) break; |
889 |
} |
890 |
} |
891 |
|
892 |
/** |
893 |
* Replaces each element of this deque with the result of applying the |
894 |
* operator to that element, as specified by {@link List#replaceAll}. |
895 |
* |
896 |
* @param operator the operator to apply to each element |
897 |
* @since TBD |
898 |
*/ |
899 |
@SuppressWarnings("unchecked") |
900 |
/* public */ void replaceAll(UnaryOperator<E> operator) { |
901 |
Objects.requireNonNull(operator); |
902 |
final Object[] es = elements; |
903 |
int i, end, to, todo; |
904 |
todo = (end = (i = head) + size) |
905 |
- (to = (es.length - end >= 0) ? end : es.length); |
906 |
for (;; to = todo, todo = 0, i = 0) { |
907 |
for (; i < to; i++) |
908 |
es[i] = operator.apply((E) es[i]); |
909 |
if (todo == 0) break; |
910 |
} |
911 |
// checkInvariants(); |
912 |
} |
913 |
|
914 |
/** |
915 |
* @throws NullPointerException {@inheritDoc} |
916 |
*/ |
917 |
public boolean removeIf(Predicate<? super E> filter) { |
918 |
Objects.requireNonNull(filter); |
919 |
return bulkRemove(filter); |
920 |
} |
921 |
|
922 |
/** |
923 |
* @throws NullPointerException {@inheritDoc} |
924 |
*/ |
925 |
public boolean removeAll(Collection<?> c) { |
926 |
Objects.requireNonNull(c); |
927 |
return bulkRemove(e -> c.contains(e)); |
928 |
} |
929 |
|
930 |
/** |
931 |
* @throws NullPointerException {@inheritDoc} |
932 |
*/ |
933 |
public boolean retainAll(Collection<?> c) { |
934 |
Objects.requireNonNull(c); |
935 |
return bulkRemove(e -> !c.contains(e)); |
936 |
} |
937 |
|
938 |
/** Implementation of bulk remove methods. */ |
939 |
@SuppressWarnings("unchecked") |
940 |
private boolean bulkRemove(Predicate<? super E> filter) { |
941 |
// checkInvariants(); |
942 |
final Object[] es = elements; |
943 |
int i, end, to, todo; |
944 |
todo = (end = (i = head) + size) |
945 |
- (to = (es.length - end >= 0) ? end : es.length); |
946 |
// Optimize for initial run of non-removed elements |
947 |
findFirstRemoved: |
948 |
for (;; to = todo, todo = 0, i = 0) { |
949 |
for (; i < to; i++) |
950 |
if (filter.test((E) es[i])) |
951 |
break findFirstRemoved; |
952 |
if (todo == 0) return false; |
953 |
} |
954 |
bulkRemoveModified(filter, i, to, todo); |
955 |
return true; |
956 |
} |
957 |
|
958 |
/** |
959 |
* Helper for bulkRemove, in case of at least one deletion. |
960 |
* @param i valid index of first element to be deleted |
961 |
*/ |
962 |
@SuppressWarnings("unchecked") |
963 |
private void bulkRemoveModified( |
964 |
Predicate<? super E> filter, int i, int to, int todo) { |
965 |
final Object[] es = elements; |
966 |
final int capacity = es.length; |
967 |
// a two-finger algorithm, with hare i and tortoise j |
968 |
int j = i++; |
969 |
try { |
970 |
for (;;) { |
971 |
E e; |
972 |
// In this loop, i and j are on the same leg, with i > j |
973 |
for (; i < to; i++) |
974 |
if (!filter.test(e = (E) es[i])) |
975 |
es[j++] = e; |
976 |
if (todo == 0) break; |
977 |
// In this loop, j is on the first leg, i on the second |
978 |
for (to = todo, todo = 0, i = 0; i < to && j < capacity; i++) |
979 |
if (!filter.test(e = (E) es[i])) |
980 |
es[j++] = e; |
981 |
if (i >= to) break; |
982 |
j = 0; // j rejoins i on second leg |
983 |
} |
984 |
bulkRemoveClear(es, j, i); |
985 |
// checkInvariants(); |
986 |
} catch (Throwable ex) { |
987 |
// copy remaining elements |
988 |
for (int remaining = (to - i) + todo; --remaining >= 0;) { |
989 |
es[j] = es[i]; |
990 |
if (++i >= capacity) i = 0; |
991 |
if (++j >= capacity) j = 0; |
992 |
} |
993 |
bulkRemoveClear(es, j, i); |
994 |
// checkInvariants(); |
995 |
throw ex; |
996 |
} |
997 |
} |
998 |
|
999 |
/** |
1000 |
* Nulls out all elements from index j upto index i. |
1001 |
*/ |
1002 |
private void bulkRemoveClear(Object[] es, int j, int i) { |
1003 |
int deleted; |
1004 |
if ((deleted = i - j) <= 0) deleted += es.length; |
1005 |
size -= deleted; |
1006 |
circularClear(es, j, deleted); |
1007 |
} |
1008 |
|
1009 |
/** |
1010 |
* Returns {@code true} if this deque contains the specified element. |
1011 |
* More formally, returns {@code true} if and only if this deque contains |
1012 |
* at least one element {@code e} such that {@code o.equals(e)}. |
1013 |
* |
1014 |
* @param o object to be checked for containment in this deque |
1015 |
* @return {@code true} if this deque contains the specified element |
1016 |
*/ |
1017 |
public boolean contains(Object o) { |
1018 |
if (o != null) { |
1019 |
final Object[] es = elements; |
1020 |
int i, end, to, todo; |
1021 |
todo = (end = (i = head) + size) |
1022 |
- (to = (es.length - end >= 0) ? end : es.length); |
1023 |
for (;; to = todo, todo = 0, i = 0) { |
1024 |
for (; i < to; i++) |
1025 |
if (o.equals(es[i])) |
1026 |
return true; |
1027 |
if (todo == 0) break; |
1028 |
} |
1029 |
} |
1030 |
return false; |
1031 |
} |
1032 |
|
1033 |
/** |
1034 |
* Removes a single instance of the specified element from this deque. |
1035 |
* If the deque does not contain the element, it is unchanged. |
1036 |
* More formally, removes the first element {@code e} such that |
1037 |
* {@code o.equals(e)} (if such an element exists). |
1038 |
* Returns {@code true} if this deque contained the specified element |
1039 |
* (or equivalently, if this deque changed as a result of the call). |
1040 |
* |
1041 |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
1042 |
* |
1043 |
* @param o element to be removed from this deque, if present |
1044 |
* @return {@code true} if this deque contained the specified element |
1045 |
*/ |
1046 |
public boolean remove(Object o) { |
1047 |
return removeFirstOccurrence(o); |
1048 |
} |
1049 |
|
1050 |
/** |
1051 |
* Removes all of the elements from this deque. |
1052 |
* The deque will be empty after this call returns. |
1053 |
*/ |
1054 |
public void clear() { |
1055 |
circularClear(elements, head, size); |
1056 |
size = head = 0; |
1057 |
// checkInvariants(); |
1058 |
} |
1059 |
|
1060 |
/** |
1061 |
* Nulls out count elements, starting at array index from. |
1062 |
* Special case (from == es.length) is treated the same as (from == 0). |
1063 |
*/ |
1064 |
private static void circularClear(Object[] es, int from, int count) { |
1065 |
int end, to, todo; |
1066 |
todo = (end = from + count) |
1067 |
- (to = (es.length - end >= 0) ? end : es.length); |
1068 |
for (;; to = todo, todo = 0, from = 0) { |
1069 |
Arrays.fill(es, from, to, null); |
1070 |
if (todo == 0) break; |
1071 |
} |
1072 |
} |
1073 |
|
1074 |
/** |
1075 |
* Returns an array containing all of the elements in this deque |
1076 |
* in proper sequence (from first to last element). |
1077 |
* |
1078 |
* <p>The returned array will be "safe" in that no references to it are |
1079 |
* maintained by this deque. (In other words, this method must allocate |
1080 |
* a new array). The caller is thus free to modify the returned array. |
1081 |
* |
1082 |
* <p>This method acts as bridge between array-based and collection-based |
1083 |
* APIs. |
1084 |
* |
1085 |
* @return an array containing all of the elements in this deque |
1086 |
*/ |
1087 |
public Object[] toArray() { |
1088 |
return toArray(Object[].class); |
1089 |
} |
1090 |
|
1091 |
private <T> T[] toArray(Class<T[]> klazz) { |
1092 |
final Object[] es = elements; |
1093 |
final T[] a; |
1094 |
final int head, len, end, todo; |
1095 |
todo = size - (len = Math.min(size, es.length - (head = this.head))); |
1096 |
if ((end = head + size) >= 0) { |
1097 |
a = Arrays.copyOfRange(es, head, end, klazz); |
1098 |
} else { |
1099 |
// integer overflow! |
1100 |
a = Arrays.copyOfRange(es, 0, size, klazz); |
1101 |
System.arraycopy(es, head, a, 0, len); |
1102 |
} |
1103 |
if (todo > 0) |
1104 |
System.arraycopy(es, 0, a, len, todo); |
1105 |
return a; |
1106 |
} |
1107 |
|
1108 |
/** |
1109 |
* Returns an array containing all of the elements in this deque in |
1110 |
* proper sequence (from first to last element); the runtime type of the |
1111 |
* returned array is that of the specified array. If the deque fits in |
1112 |
* the specified array, it is returned therein. Otherwise, a new array |
1113 |
* is allocated with the runtime type of the specified array and the |
1114 |
* size of this deque. |
1115 |
* |
1116 |
* <p>If this deque fits in the specified array with room to spare |
1117 |
* (i.e., the array has more elements than this deque), the element in |
1118 |
* the array immediately following the end of the deque is set to |
1119 |
* {@code null}. |
1120 |
* |
1121 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
1122 |
* array-based and collection-based APIs. Further, this method allows |
1123 |
* precise control over the runtime type of the output array, and may, |
1124 |
* under certain circumstances, be used to save allocation costs. |
1125 |
* |
1126 |
* <p>Suppose {@code x} is a deque known to contain only strings. |
1127 |
* The following code can be used to dump the deque into a newly |
1128 |
* allocated array of {@code String}: |
1129 |
* |
1130 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
1131 |
* |
1132 |
* Note that {@code toArray(new Object[0])} is identical in function to |
1133 |
* {@code toArray()}. |
1134 |
* |
1135 |
* @param a the array into which the elements of the deque are to |
1136 |
* be stored, if it is big enough; otherwise, a new array of the |
1137 |
* same runtime type is allocated for this purpose |
1138 |
* @return an array containing all of the elements in this deque |
1139 |
* @throws ArrayStoreException if the runtime type of the specified array |
1140 |
* is not a supertype of the runtime type of every element in |
1141 |
* this deque |
1142 |
* @throws NullPointerException if the specified array is null |
1143 |
*/ |
1144 |
@SuppressWarnings("unchecked") |
1145 |
public <T> T[] toArray(T[] a) { |
1146 |
final int size; |
1147 |
if ((size = this.size) > a.length) |
1148 |
return toArray((Class<T[]>) a.getClass()); |
1149 |
final Object[] es = elements; |
1150 |
int i, j, len, todo; |
1151 |
todo = size - (len = Math.min(size, es.length - (i = head))); |
1152 |
for (j = 0;; j += len, len = todo, todo = 0, i = 0) { |
1153 |
System.arraycopy(es, i, a, j, len); |
1154 |
if (todo == 0) break; |
1155 |
} |
1156 |
if (size < a.length) |
1157 |
a[size] = null; |
1158 |
return a; |
1159 |
} |
1160 |
|
1161 |
// *** Object methods *** |
1162 |
|
1163 |
/** |
1164 |
* Returns a copy of this deque. |
1165 |
* |
1166 |
* @return a copy of this deque |
1167 |
*/ |
1168 |
public ArrayDeque<E> clone() { |
1169 |
try { |
1170 |
@SuppressWarnings("unchecked") |
1171 |
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
1172 |
result.elements = Arrays.copyOf(elements, elements.length); |
1173 |
return result; |
1174 |
} catch (CloneNotSupportedException e) { |
1175 |
throw new AssertionError(); |
1176 |
} |
1177 |
} |
1178 |
|
1179 |
private static final long serialVersionUID = 2340985798034038923L; |
1180 |
|
1181 |
/** |
1182 |
* Saves this deque to a stream (that is, serializes it). |
1183 |
* |
1184 |
* @param s the stream |
1185 |
* @throws java.io.IOException if an I/O error occurs |
1186 |
* @serialData The current size ({@code int}) of the deque, |
1187 |
* followed by all of its elements (each an object reference) in |
1188 |
* first-to-last order. |
1189 |
*/ |
1190 |
private void writeObject(java.io.ObjectOutputStream s) |
1191 |
throws java.io.IOException { |
1192 |
s.defaultWriteObject(); |
1193 |
|
1194 |
// Write out size |
1195 |
s.writeInt(size); |
1196 |
|
1197 |
// Write out elements in order. |
1198 |
final Object[] es = elements; |
1199 |
int i, end, to, todo; |
1200 |
todo = (end = (i = head) + size) |
1201 |
- (to = (es.length - end >= 0) ? end : es.length); |
1202 |
for (;; to = todo, todo = 0, i = 0) { |
1203 |
for (; i < to; i++) |
1204 |
s.writeObject(es[i]); |
1205 |
if (todo == 0) break; |
1206 |
} |
1207 |
} |
1208 |
|
1209 |
/** |
1210 |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1211 |
* @param s the stream |
1212 |
* @throws ClassNotFoundException if the class of a serialized object |
1213 |
* could not be found |
1214 |
* @throws java.io.IOException if an I/O error occurs |
1215 |
*/ |
1216 |
private void readObject(java.io.ObjectInputStream s) |
1217 |
throws java.io.IOException, ClassNotFoundException { |
1218 |
s.defaultReadObject(); |
1219 |
|
1220 |
// Read in size and allocate array |
1221 |
elements = new Object[size = s.readInt()]; |
1222 |
|
1223 |
// Read in all elements in the proper order. |
1224 |
for (int i = 0; i < size; i++) |
1225 |
elements[i] = s.readObject(); |
1226 |
} |
1227 |
|
1228 |
/** debugging */ |
1229 |
void checkInvariants() { |
1230 |
try { |
1231 |
int capacity = elements.length; |
1232 |
// assert size >= 0 && size <= capacity; |
1233 |
// assert head >= 0; |
1234 |
// assert capacity == 0 || head < capacity; |
1235 |
// assert size == 0 || elements[head] != null; |
1236 |
// assert size == 0 || elements[tail()] != null; |
1237 |
// assert size == capacity || elements[dec(head, capacity)] == null; |
1238 |
// assert size == capacity || elements[inc(tail(), capacity)] == null; |
1239 |
} catch (Throwable t) { |
1240 |
System.err.printf("head=%d size=%d capacity=%d%n", |
1241 |
head, size, elements.length); |
1242 |
System.err.printf("elements=%s%n", |
1243 |
Arrays.toString(elements)); |
1244 |
throw t; |
1245 |
} |
1246 |
} |
1247 |
|
1248 |
} |