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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 void grow(int needed) { |
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// overflow-conscious code |
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// checkInvariants(); |
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int oldCapacity = elements.length; |
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int newCapacity; |
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// Double size if small; else grow by 50% |
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int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1); |
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if (jump < needed |
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|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0) |
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newCapacity = newCapacity(needed, jump); |
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elements = Arrays.copyOf(elements, newCapacity); |
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if (oldCapacity - head < size) { |
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// wrap around; slide first leg forward to end of array |
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int newSpace = newCapacity - oldCapacity; |
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System.arraycopy(elements, head, |
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elements, head + newSpace, |
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oldCapacity - head); |
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Arrays.fill(elements, head, head + newSpace, null); |
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head += newSpace; |
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} |
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// checkInvariants(); |
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} |
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|
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/** Capacity calculation for edge conditions, especially overflow. */ |
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private int newCapacity(int needed, int jump) { |
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int oldCapacity = elements.length; |
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int minCapacity; |
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if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) { |
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if (minCapacity < 0) |
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throw new IllegalStateException("Sorry, deque too big"); |
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return Integer.MAX_VALUE; |
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} |
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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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*/ |
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/* TODO: public */ private 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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/* TODO: public */ private 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[] elements = c.toArray(); |
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// defend against c.toArray (incorrectly) not returning Object[] |
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// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652) |
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if (elements.getClass() != Object[].class) |
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elements = Arrays.copyOf(elements, size, Object[].class); |
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for (Object obj : elements) |
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Objects.requireNonNull(obj); |
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size = elements.length; |
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this.elements = elements; |
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} |
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|
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/** |
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* Increments i, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus. |
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*/ |
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static final int inc(int i, int modulus) { |
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if (++i == modulus) i = 0; |
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return i; |
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} |
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|
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/** |
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* Decrements i, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus. |
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*/ |
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static final int dec(int i, int modulus) { |
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if (--i < 0) i += modulus; |
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return i; |
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} |
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|
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/** |
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* Adds i and j, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus. |
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*/ |
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static final int add(int i, int j, int modulus) { |
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if ((i += j) - modulus >= 0) i -= modulus; |
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return i; |
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} |
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|
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/** |
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* Returns the array index of the last element. |
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* May return invalid index -1 if there are no elements. |
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*/ |
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final int tail() { |
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return add(head, size - 1, elements.length); |
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} |
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|
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/** |
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* Returns element at array index i. |
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*/ |
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@SuppressWarnings("unchecked") |
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final E elementAt(int i) { |
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return (E) elements[i]; |
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} |
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|
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/** |
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* A version of elementAt that checks for null elements. |
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* This check doesn't catch all possible comodifications, |
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* but does catch ones that corrupt traversal. |
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*/ |
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E checkedElementAt(Object[] elements, int i) { |
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@SuppressWarnings("unchecked") E e = (E) elements[i]; |
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if (e == null) |
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throw new ConcurrentModificationException(); |
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return e; |
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} |
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|
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// The main insertion and extraction methods are addFirst, |
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// 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[] elements; |
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int capacity, s = size; |
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while (s == (capacity = (elements = this.elements).length)) |
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grow(1); |
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elements[head = dec(head, capacity)] = e; |
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size = s + 1; |
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} |
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|
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/** |
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* Inserts the specified element at the end of this deque. |
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* |
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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[] elements; |
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int capacity, s = size; |
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while (s == (capacity = (elements = this.elements).length)) |
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grow(1); |
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elements[add(head, s, capacity)] = e; |
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size = s + 1; |
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} |
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|
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/** |
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* 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. |
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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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*/ |
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@Override |
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public boolean addAll(Collection<? extends E> c) { |
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// checkInvariants(); |
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Object[] a, elements; |
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int newcomers, capacity, s = size; |
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if ((newcomers = (a = c.toArray()).length) == 0) |
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return false; |
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while ((capacity = (elements = this.elements).length) - s < newcomers) |
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grow(newcomers - (capacity - s)); |
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int i = add(head, s, capacity); |
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for (Object x : a) { |
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Objects.requireNonNull(x); |
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elements[i] = x; |
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i = inc(i, capacity); |
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size++; |
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} |
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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 front of this deque. |
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* |
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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 |
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*/ |
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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. |
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* |
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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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*/ |
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public boolean offerLast(E e) { |
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addLast(e); |
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return true; |
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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 removeFirst() { |
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// checkInvariants(); |
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E x = pollFirst(); |
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if (x == null) |
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throw new NoSuchElementException(); |
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return x; |
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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 x = pollLast(); |
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if (x == null) |
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throw new NoSuchElementException(); |
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return x; |
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} |
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|
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public E pollFirst() { |
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// checkInvariants(); |
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final int s, h; |
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if ((s = size) == 0) |
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return null; |
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final Object[] elements = this.elements; |
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@SuppressWarnings("unchecked") E e = (E) elements[h = head]; |
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elements[h] = null; |
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head = inc(h, elements.length); |
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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; |
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final Object[] elements = this.elements; |
385 |
@SuppressWarnings("unchecked") |
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E e = (E) elements[tail = add(head, s - 1, elements.length)]; |
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elements[tail] = null; |
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size = s - 1; |
389 |
return e; |
390 |
} |
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|
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
394 |
*/ |
395 |
public E getFirst() { |
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// checkInvariants(); |
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if (size == 0) throw new NoSuchElementException(); |
398 |
return elementAt(head); |
399 |
} |
400 |
|
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/** |
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* @throws NoSuchElementException {@inheritDoc} |
403 |
*/ |
404 |
public E getLast() { |
405 |
// checkInvariants(); |
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if (size == 0) throw new NoSuchElementException(); |
407 |
return elementAt(tail()); |
408 |
} |
409 |
|
410 |
public E peekFirst() { |
411 |
// checkInvariants(); |
412 |
return (size == 0) ? null : elementAt(head); |
413 |
} |
414 |
|
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public E peekLast() { |
416 |
// checkInvariants(); |
417 |
return (size == 0) ? null : elementAt(tail()); |
418 |
} |
419 |
|
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/** |
421 |
* Removes the first occurrence of the specified element in this |
422 |
* deque (when traversing the deque from head to tail). |
423 |
* If the deque does not contain the element, it is unchanged. |
424 |
* More formally, removes the first element {@code e} such that |
425 |
* {@code o.equals(e)} (if such an element exists). |
426 |
* Returns {@code true} if this deque contained the specified element |
427 |
* (or equivalently, if this deque changed as a result of the call). |
428 |
* |
429 |
* @param o element to be removed from this deque, if present |
430 |
* @return {@code true} if the deque contained the specified element |
431 |
*/ |
432 |
public boolean removeFirstOccurrence(Object o) { |
433 |
// checkInvariants(); |
434 |
if (o != null) { |
435 |
final Object[] elements = this.elements; |
436 |
final int capacity = elements.length; |
437 |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) { |
438 |
if (o.equals(elements[i])) { |
439 |
delete(i); |
440 |
return true; |
441 |
} |
442 |
} |
443 |
} |
444 |
return false; |
445 |
} |
446 |
|
447 |
/** |
448 |
* Removes the last occurrence of the specified element in this |
449 |
* deque (when traversing the deque from head to tail). |
450 |
* If the deque does not contain the element, it is unchanged. |
451 |
* More formally, removes the last element {@code e} such that |
452 |
* {@code o.equals(e)} (if such an element exists). |
453 |
* Returns {@code true} if this deque contained the specified element |
454 |
* (or equivalently, if this deque changed as a result of the call). |
455 |
* |
456 |
* @param o element to be removed from this deque, if present |
457 |
* @return {@code true} if the deque contained the specified element |
458 |
*/ |
459 |
public boolean removeLastOccurrence(Object o) { |
460 |
if (o != null) { |
461 |
final Object[] elements = this.elements; |
462 |
final int capacity = elements.length; |
463 |
for (int k = size, i = add(head, k - 1, capacity); |
464 |
--k >= 0; i = dec(i, capacity)) { |
465 |
if (o.equals(elements[i])) { |
466 |
delete(i); |
467 |
return true; |
468 |
} |
469 |
} |
470 |
} |
471 |
return false; |
472 |
} |
473 |
|
474 |
// *** Queue methods *** |
475 |
|
476 |
/** |
477 |
* Inserts the specified element at the end of this deque. |
478 |
* |
479 |
* <p>This method is equivalent to {@link #addLast}. |
480 |
* |
481 |
* @param e the element to add |
482 |
* @return {@code true} (as specified by {@link Collection#add}) |
483 |
* @throws NullPointerException if the specified element is null |
484 |
*/ |
485 |
public boolean add(E e) { |
486 |
addLast(e); |
487 |
return true; |
488 |
} |
489 |
|
490 |
/** |
491 |
* Inserts the specified element at the end of this deque. |
492 |
* |
493 |
* <p>This method is equivalent to {@link #offerLast}. |
494 |
* |
495 |
* @param e the element to add |
496 |
* @return {@code true} (as specified by {@link Queue#offer}) |
497 |
* @throws NullPointerException if the specified element is null |
498 |
*/ |
499 |
public boolean offer(E e) { |
500 |
return offerLast(e); |
501 |
} |
502 |
|
503 |
/** |
504 |
* Retrieves and removes the head of the queue represented by this deque. |
505 |
* |
506 |
* This method differs from {@link #poll poll} only in that it throws an |
507 |
* exception if this deque is empty. |
508 |
* |
509 |
* <p>This method is equivalent to {@link #removeFirst}. |
510 |
* |
511 |
* @return the head of the queue represented by this deque |
512 |
* @throws NoSuchElementException {@inheritDoc} |
513 |
*/ |
514 |
public E remove() { |
515 |
return removeFirst(); |
516 |
} |
517 |
|
518 |
/** |
519 |
* Retrieves and removes the head of the queue represented by this deque |
520 |
* (in other words, the first element of this deque), or returns |
521 |
* {@code null} if this deque is empty. |
522 |
* |
523 |
* <p>This method is equivalent to {@link #pollFirst}. |
524 |
* |
525 |
* @return the head of the queue represented by this deque, or |
526 |
* {@code null} if this deque is empty |
527 |
*/ |
528 |
public E poll() { |
529 |
return pollFirst(); |
530 |
} |
531 |
|
532 |
/** |
533 |
* Retrieves, but does not remove, the head of the queue represented by |
534 |
* this deque. This method differs from {@link #peek peek} only in |
535 |
* that it throws an exception if this deque is empty. |
536 |
* |
537 |
* <p>This method is equivalent to {@link #getFirst}. |
538 |
* |
539 |
* @return the head of the queue represented by this deque |
540 |
* @throws NoSuchElementException {@inheritDoc} |
541 |
*/ |
542 |
public E element() { |
543 |
return getFirst(); |
544 |
} |
545 |
|
546 |
/** |
547 |
* Retrieves, but does not remove, the head of the queue represented by |
548 |
* this deque, or returns {@code null} if this deque is empty. |
549 |
* |
550 |
* <p>This method is equivalent to {@link #peekFirst}. |
551 |
* |
552 |
* @return the head of the queue represented by this deque, or |
553 |
* {@code null} if this deque is empty |
554 |
*/ |
555 |
public E peek() { |
556 |
return peekFirst(); |
557 |
} |
558 |
|
559 |
// *** Stack methods *** |
560 |
|
561 |
/** |
562 |
* Pushes an element onto the stack represented by this deque. In other |
563 |
* words, inserts the element at the front of this deque. |
564 |
* |
565 |
* <p>This method is equivalent to {@link #addFirst}. |
566 |
* |
567 |
* @param e the element to push |
568 |
* @throws NullPointerException if the specified element is null |
569 |
*/ |
570 |
public void push(E e) { |
571 |
addFirst(e); |
572 |
} |
573 |
|
574 |
/** |
575 |
* Pops an element from the stack represented by this deque. In other |
576 |
* words, removes and returns the first element of this deque. |
577 |
* |
578 |
* <p>This method is equivalent to {@link #removeFirst()}. |
579 |
* |
580 |
* @return the element at the front of this deque (which is the top |
581 |
* of the stack represented by this deque) |
582 |
* @throws NoSuchElementException {@inheritDoc} |
583 |
*/ |
584 |
public E pop() { |
585 |
return removeFirst(); |
586 |
} |
587 |
|
588 |
/** |
589 |
* Removes the element at the specified position in the elements array. |
590 |
* This can result in forward or backwards motion of array elements. |
591 |
* We optimize for least element motion. |
592 |
* |
593 |
* <p>This method is called delete rather than remove to emphasize |
594 |
* that its semantics differ from those of {@link List#remove(int)}. |
595 |
* |
596 |
* @return true if elements moved backwards |
597 |
*/ |
598 |
boolean delete(int i) { |
599 |
// checkInvariants(); |
600 |
final Object[] elements = this.elements; |
601 |
final int capacity = elements.length; |
602 |
final int h = head; |
603 |
int front; // number of elements before to-be-deleted elt |
604 |
if ((front = i - h) < 0) front += capacity; |
605 |
final int back = size - front - 1; // number of elements after |
606 |
if (front < back) { |
607 |
// move front elements forwards |
608 |
if (h <= i) { |
609 |
System.arraycopy(elements, h, elements, h + 1, front); |
610 |
} else { // Wrap around |
611 |
System.arraycopy(elements, 0, elements, 1, i); |
612 |
elements[0] = elements[capacity - 1]; |
613 |
System.arraycopy(elements, h, elements, h + 1, front - (i + 1)); |
614 |
} |
615 |
elements[h] = null; |
616 |
head = inc(h, capacity); |
617 |
size--; |
618 |
// checkInvariants(); |
619 |
return false; |
620 |
} else { |
621 |
// move back elements backwards |
622 |
int tail = tail(); |
623 |
if (i <= tail) { |
624 |
System.arraycopy(elements, i + 1, elements, i, back); |
625 |
} else { // Wrap around |
626 |
int firstLeg = capacity - (i + 1); |
627 |
System.arraycopy(elements, i + 1, elements, i, firstLeg); |
628 |
elements[capacity - 1] = elements[0]; |
629 |
System.arraycopy(elements, 1, elements, 0, back - firstLeg - 1); |
630 |
} |
631 |
elements[tail] = null; |
632 |
size--; |
633 |
// checkInvariants(); |
634 |
return true; |
635 |
} |
636 |
} |
637 |
|
638 |
// *** Collection Methods *** |
639 |
|
640 |
/** |
641 |
* Returns the number of elements in this deque. |
642 |
* |
643 |
* @return the number of elements in this deque |
644 |
*/ |
645 |
public int size() { |
646 |
return size; |
647 |
} |
648 |
|
649 |
/** |
650 |
* Returns {@code true} if this deque contains no elements. |
651 |
* |
652 |
* @return {@code true} if this deque contains no elements |
653 |
*/ |
654 |
public boolean isEmpty() { |
655 |
return size == 0; |
656 |
} |
657 |
|
658 |
/** |
659 |
* Returns an iterator over the elements in this deque. The elements |
660 |
* will be ordered from first (head) to last (tail). This is the same |
661 |
* order that elements would be dequeued (via successive calls to |
662 |
* {@link #remove} or popped (via successive calls to {@link #pop}). |
663 |
* |
664 |
* @return an iterator over the elements in this deque |
665 |
*/ |
666 |
public Iterator<E> iterator() { |
667 |
return new DeqIterator(); |
668 |
} |
669 |
|
670 |
public Iterator<E> descendingIterator() { |
671 |
return new DescendingIterator(); |
672 |
} |
673 |
|
674 |
private class DeqIterator implements Iterator<E> { |
675 |
/** Index of element to be returned by subsequent call to next. */ |
676 |
int cursor; |
677 |
|
678 |
/** Number of elements yet to be returned. */ |
679 |
int remaining = size; |
680 |
|
681 |
/** |
682 |
* Index of element returned by most recent call to next. |
683 |
* Reset to -1 if element is deleted by a call to remove. |
684 |
*/ |
685 |
int lastRet = -1; |
686 |
|
687 |
DeqIterator() { cursor = head; } |
688 |
|
689 |
int advance(int i, int modulus) { |
690 |
return inc(i, modulus); |
691 |
} |
692 |
|
693 |
void doRemove() { |
694 |
if (delete(lastRet)) |
695 |
// if left-shifted, undo advance in next() |
696 |
cursor = dec(cursor, elements.length); |
697 |
} |
698 |
|
699 |
public final boolean hasNext() { |
700 |
return remaining > 0; |
701 |
} |
702 |
|
703 |
public final E next() { |
704 |
if (remaining == 0) |
705 |
throw new NoSuchElementException(); |
706 |
E e = checkedElementAt(elements, cursor); |
707 |
lastRet = cursor; |
708 |
cursor = advance(cursor, elements.length); |
709 |
remaining--; |
710 |
return e; |
711 |
} |
712 |
|
713 |
public final void remove() { |
714 |
if (lastRet < 0) |
715 |
throw new IllegalStateException(); |
716 |
doRemove(); |
717 |
lastRet = -1; |
718 |
} |
719 |
|
720 |
public final void forEachRemaining(Consumer<? super E> action) { |
721 |
Objects.requireNonNull(action); |
722 |
final Object[] elements = ArrayDeque.this.elements; |
723 |
final int capacity = elements.length; |
724 |
int k = remaining; |
725 |
remaining = 0; |
726 |
for (int i = cursor; --k >= 0; i = advance(i, capacity)) |
727 |
action.accept(checkedElementAt(elements, i)); |
728 |
} |
729 |
} |
730 |
|
731 |
private class DescendingIterator extends DeqIterator { |
732 |
DescendingIterator() { cursor = tail(); } |
733 |
|
734 |
@Override int advance(int i, int modulus) { |
735 |
return dec(i, modulus); |
736 |
} |
737 |
|
738 |
@Override void doRemove() { |
739 |
if (!delete(lastRet)) |
740 |
// if right-shifted, undo advance in next |
741 |
cursor = inc(cursor, elements.length); |
742 |
} |
743 |
} |
744 |
|
745 |
/** |
746 |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
747 |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
748 |
* deque. |
749 |
* |
750 |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
751 |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
752 |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
753 |
* the reporting of additional characteristic values. |
754 |
* |
755 |
* @return a {@code Spliterator} over the elements in this deque |
756 |
* @since 1.8 |
757 |
*/ |
758 |
public Spliterator<E> spliterator() { |
759 |
return new ArrayDequeSpliterator(); |
760 |
} |
761 |
|
762 |
final class ArrayDequeSpliterator implements Spliterator<E> { |
763 |
private int cursor; |
764 |
private int remaining; // -1 until late-binding first use |
765 |
|
766 |
/** Constructs late-binding spliterator over all elements. */ |
767 |
ArrayDequeSpliterator() { |
768 |
this.remaining = -1; |
769 |
} |
770 |
|
771 |
/** Constructs spliterator over the given slice. */ |
772 |
ArrayDequeSpliterator(int cursor, int count) { |
773 |
this.cursor = cursor; |
774 |
this.remaining = count; |
775 |
} |
776 |
|
777 |
/** Ensures late-binding initialization; then returns remaining. */ |
778 |
private int remaining() { |
779 |
if (remaining < 0) { |
780 |
cursor = head; |
781 |
remaining = size; |
782 |
} |
783 |
return remaining; |
784 |
} |
785 |
|
786 |
public ArrayDequeSpliterator trySplit() { |
787 |
final int mid; |
788 |
if ((mid = remaining() >> 1) > 0) { |
789 |
int oldCursor = cursor; |
790 |
cursor = add(cursor, mid, elements.length); |
791 |
remaining -= mid; |
792 |
return new ArrayDequeSpliterator(oldCursor, mid); |
793 |
} |
794 |
return null; |
795 |
} |
796 |
|
797 |
public void forEachRemaining(Consumer<? super E> action) { |
798 |
Objects.requireNonNull(action); |
799 |
final Object[] elements = ArrayDeque.this.elements; |
800 |
final int capacity = elements.length; |
801 |
int k = remaining(); |
802 |
remaining = 0; |
803 |
for (int i = cursor; --k >= 0; i = inc(i, capacity)) |
804 |
action.accept(checkedElementAt(elements, i)); |
805 |
} |
806 |
|
807 |
public boolean tryAdvance(Consumer<? super E> action) { |
808 |
Objects.requireNonNull(action); |
809 |
if (remaining() == 0) |
810 |
return false; |
811 |
action.accept(checkedElementAt(elements, cursor)); |
812 |
cursor = inc(cursor, elements.length); |
813 |
remaining--; |
814 |
return true; |
815 |
} |
816 |
|
817 |
public long estimateSize() { |
818 |
return remaining(); |
819 |
} |
820 |
|
821 |
public int characteristics() { |
822 |
return Spliterator.NONNULL |
823 |
| Spliterator.ORDERED |
824 |
| Spliterator.SIZED |
825 |
| Spliterator.SUBSIZED; |
826 |
} |
827 |
} |
828 |
|
829 |
@Override |
830 |
public void forEach(Consumer<? super E> action) { |
831 |
// checkInvariants(); |
832 |
Objects.requireNonNull(action); |
833 |
final Object[] elements = this.elements; |
834 |
final int capacity = elements.length; |
835 |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
836 |
action.accept(elementAt(i)); |
837 |
// checkInvariants(); |
838 |
} |
839 |
|
840 |
/** |
841 |
* Replaces each element of this deque with the result of applying the |
842 |
* operator to that element, as specified by {@link List#replaceAll}. |
843 |
* |
844 |
* @param operator the operator to apply to each element |
845 |
*/ |
846 |
/* TODO: public */ private void replaceAll(UnaryOperator<E> operator) { |
847 |
Objects.requireNonNull(operator); |
848 |
final Object[] elements = this.elements; |
849 |
final int capacity = elements.length; |
850 |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
851 |
elements[i] = operator.apply(elementAt(i)); |
852 |
// checkInvariants(); |
853 |
} |
854 |
|
855 |
/** |
856 |
* @throws NullPointerException {@inheritDoc} |
857 |
*/ |
858 |
@Override |
859 |
public boolean removeIf(Predicate<? super E> filter) { |
860 |
Objects.requireNonNull(filter); |
861 |
return bulkRemove(filter); |
862 |
} |
863 |
|
864 |
/** |
865 |
* @throws NullPointerException {@inheritDoc} |
866 |
*/ |
867 |
@Override |
868 |
public boolean removeAll(Collection<?> c) { |
869 |
Objects.requireNonNull(c); |
870 |
return bulkRemove(e -> c.contains(e)); |
871 |
} |
872 |
|
873 |
/** |
874 |
* @throws NullPointerException {@inheritDoc} |
875 |
*/ |
876 |
@Override |
877 |
public boolean retainAll(Collection<?> c) { |
878 |
Objects.requireNonNull(c); |
879 |
return bulkRemove(e -> !c.contains(e)); |
880 |
} |
881 |
|
882 |
/** Implementation of bulk remove methods. */ |
883 |
private boolean bulkRemove(Predicate<? super E> filter) { |
884 |
// checkInvariants(); |
885 |
final Object[] elements = this.elements; |
886 |
final int capacity = elements.length; |
887 |
int i = head, j = i, remaining = size, deleted = 0; |
888 |
try { |
889 |
for (; remaining > 0; remaining--, i = inc(i, capacity)) { |
890 |
@SuppressWarnings("unchecked") E e = (E) elements[i]; |
891 |
if (filter.test(e)) |
892 |
deleted++; |
893 |
else { |
894 |
if (j != i) |
895 |
elements[j] = e; |
896 |
j = inc(j, capacity); |
897 |
} |
898 |
} |
899 |
return deleted > 0; |
900 |
} catch (Throwable ex) { |
901 |
if (deleted > 0) |
902 |
for (; remaining > 0; |
903 |
remaining--, i = inc(i, capacity), j = inc(j, capacity)) |
904 |
elements[j] = elements[i]; |
905 |
throw ex; |
906 |
} finally { |
907 |
size -= deleted; |
908 |
for (; --deleted >= 0; j = inc(j, capacity)) |
909 |
elements[j] = null; |
910 |
// checkInvariants(); |
911 |
} |
912 |
} |
913 |
|
914 |
/** |
915 |
* Returns {@code true} if this deque contains the specified element. |
916 |
* More formally, returns {@code true} if and only if this deque contains |
917 |
* at least one element {@code e} such that {@code o.equals(e)}. |
918 |
* |
919 |
* @param o object to be checked for containment in this deque |
920 |
* @return {@code true} if this deque contains the specified element |
921 |
*/ |
922 |
public boolean contains(Object o) { |
923 |
if (o != null) { |
924 |
final Object[] elements = this.elements; |
925 |
final int capacity = elements.length; |
926 |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
927 |
if (o.equals(elements[i])) |
928 |
return true; |
929 |
} |
930 |
return false; |
931 |
} |
932 |
|
933 |
/** |
934 |
* Removes a single instance of the specified element from this deque. |
935 |
* If the deque does not contain the element, it is unchanged. |
936 |
* More formally, removes the first element {@code e} such that |
937 |
* {@code o.equals(e)} (if such an element exists). |
938 |
* Returns {@code true} if this deque contained the specified element |
939 |
* (or equivalently, if this deque changed as a result of the call). |
940 |
* |
941 |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
942 |
* |
943 |
* @param o element to be removed from this deque, if present |
944 |
* @return {@code true} if this deque contained the specified element |
945 |
*/ |
946 |
public boolean remove(Object o) { |
947 |
return removeFirstOccurrence(o); |
948 |
} |
949 |
|
950 |
/** |
951 |
* Removes all of the elements from this deque. |
952 |
* The deque will be empty after this call returns. |
953 |
*/ |
954 |
public void clear() { |
955 |
final Object[] elements = this.elements; |
956 |
final int capacity = elements.length; |
957 |
final int h = this.head; |
958 |
final int s = size; |
959 |
if (capacity - h >= s) |
960 |
Arrays.fill(elements, h, h + s, null); |
961 |
else { |
962 |
Arrays.fill(elements, h, capacity, null); |
963 |
Arrays.fill(elements, 0, s - capacity + h, null); |
964 |
} |
965 |
size = head = 0; |
966 |
// checkInvariants(); |
967 |
} |
968 |
|
969 |
/** |
970 |
* Returns an array containing all of the elements in this deque |
971 |
* in proper sequence (from first to last element). |
972 |
* |
973 |
* <p>The returned array will be "safe" in that no references to it are |
974 |
* maintained by this deque. (In other words, this method must allocate |
975 |
* a new array). The caller is thus free to modify the returned array. |
976 |
* |
977 |
* <p>This method acts as bridge between array-based and collection-based |
978 |
* APIs. |
979 |
* |
980 |
* @return an array containing all of the elements in this deque |
981 |
*/ |
982 |
public Object[] toArray() { |
983 |
final int head = this.head; |
984 |
final int firstLeg; |
985 |
Object[] a = Arrays.copyOfRange(elements, head, head + size); |
986 |
if ((firstLeg = elements.length - head) < size) |
987 |
System.arraycopy(elements, 0, a, firstLeg, size - firstLeg); |
988 |
return a; |
989 |
} |
990 |
|
991 |
/** |
992 |
* Returns an array containing all of the elements in this deque in |
993 |
* proper sequence (from first to last element); the runtime type of the |
994 |
* returned array is that of the specified array. If the deque fits in |
995 |
* the specified array, it is returned therein. Otherwise, a new array |
996 |
* is allocated with the runtime type of the specified array and the |
997 |
* size of this deque. |
998 |
* |
999 |
* <p>If this deque fits in the specified array with room to spare |
1000 |
* (i.e., the array has more elements than this deque), the element in |
1001 |
* the array immediately following the end of the deque is set to |
1002 |
* {@code null}. |
1003 |
* |
1004 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
1005 |
* array-based and collection-based APIs. Further, this method allows |
1006 |
* precise control over the runtime type of the output array, and may, |
1007 |
* under certain circumstances, be used to save allocation costs. |
1008 |
* |
1009 |
* <p>Suppose {@code x} is a deque known to contain only strings. |
1010 |
* The following code can be used to dump the deque into a newly |
1011 |
* allocated array of {@code String}: |
1012 |
* |
1013 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
1014 |
* |
1015 |
* Note that {@code toArray(new Object[0])} is identical in function to |
1016 |
* {@code toArray()}. |
1017 |
* |
1018 |
* @param a the array into which the elements of the deque are to |
1019 |
* be stored, if it is big enough; otherwise, a new array of the |
1020 |
* same runtime type is allocated for this purpose |
1021 |
* @return an array containing all of the elements in this deque |
1022 |
* @throws ArrayStoreException if the runtime type of the specified array |
1023 |
* is not a supertype of the runtime type of every element in |
1024 |
* this deque |
1025 |
* @throws NullPointerException if the specified array is null |
1026 |
*/ |
1027 |
@SuppressWarnings("unchecked") |
1028 |
public <T> T[] toArray(T[] a) { |
1029 |
final Object[] elements = this.elements; |
1030 |
final int head = this.head; |
1031 |
final int firstLeg; |
1032 |
boolean wrap = (firstLeg = elements.length - head) < size; |
1033 |
if (size > a.length) { |
1034 |
a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
1035 |
a.getClass()); |
1036 |
} else { |
1037 |
System.arraycopy(elements, head, a, 0, wrap ? firstLeg : size); |
1038 |
if (size < a.length) |
1039 |
a[size] = null; |
1040 |
} |
1041 |
if (wrap) |
1042 |
System.arraycopy(elements, 0, a, firstLeg, size - firstLeg); |
1043 |
return a; |
1044 |
} |
1045 |
|
1046 |
// *** Object methods *** |
1047 |
|
1048 |
/** |
1049 |
* Returns a copy of this deque. |
1050 |
* |
1051 |
* @return a copy of this deque |
1052 |
*/ |
1053 |
public ArrayDeque<E> clone() { |
1054 |
try { |
1055 |
@SuppressWarnings("unchecked") |
1056 |
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
1057 |
result.elements = Arrays.copyOf(elements, elements.length); |
1058 |
return result; |
1059 |
} catch (CloneNotSupportedException e) { |
1060 |
throw new AssertionError(); |
1061 |
} |
1062 |
} |
1063 |
|
1064 |
private static final long serialVersionUID = 2340985798034038923L; |
1065 |
|
1066 |
/** |
1067 |
* Saves this deque to a stream (that is, serializes it). |
1068 |
* |
1069 |
* @param s the stream |
1070 |
* @throws java.io.IOException if an I/O error occurs |
1071 |
* @serialData The current size ({@code int}) of the deque, |
1072 |
* followed by all of its elements (each an object reference) in |
1073 |
* first-to-last order. |
1074 |
*/ |
1075 |
private void writeObject(java.io.ObjectOutputStream s) |
1076 |
throws java.io.IOException { |
1077 |
s.defaultWriteObject(); |
1078 |
|
1079 |
// Write out size |
1080 |
s.writeInt(size); |
1081 |
|
1082 |
// Write out elements in order. |
1083 |
final Object[] elements = this.elements; |
1084 |
final int capacity = elements.length; |
1085 |
for (int k = size, i = head; --k >= 0; i = inc(i, capacity)) |
1086 |
s.writeObject(elements[i]); |
1087 |
} |
1088 |
|
1089 |
/** |
1090 |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1091 |
* @param s the stream |
1092 |
* @throws ClassNotFoundException if the class of a serialized object |
1093 |
* could not be found |
1094 |
* @throws java.io.IOException if an I/O error occurs |
1095 |
*/ |
1096 |
private void readObject(java.io.ObjectInputStream s) |
1097 |
throws java.io.IOException, ClassNotFoundException { |
1098 |
s.defaultReadObject(); |
1099 |
|
1100 |
// Read in size and allocate array |
1101 |
elements = new Object[size = s.readInt()]; |
1102 |
|
1103 |
// Read in all elements in the proper order. |
1104 |
for (int i = 0; i < size; i++) |
1105 |
elements[i] = s.readObject(); |
1106 |
} |
1107 |
|
1108 |
/** debugging */ |
1109 |
private void checkInvariants() { |
1110 |
try { |
1111 |
int capacity = elements.length; |
1112 |
assert size >= 0 && size <= capacity; |
1113 |
assert head >= 0 && ((capacity == 0 && head == 0 && size == 0) |
1114 |
|| head < capacity); |
1115 |
assert size == 0 |
1116 |
|| (elements[head] != null && elements[tail()] != null); |
1117 |
assert size == capacity |
1118 |
|| (elements[dec(head, capacity)] == null |
1119 |
&& elements[inc(tail(), capacity)] == null); |
1120 |
} catch (Throwable t) { |
1121 |
System.err.printf("head=%d size=%d capacity=%d%n", |
1122 |
head, size, elements.length); |
1123 |
System.err.printf("elements=%s%n", |
1124 |
Arrays.toString(elements)); |
1125 |
throw t; |
1126 |
} |
1127 |
} |
1128 |
|
1129 |
} |