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/* |
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* Written by Josh Bloch of Google Inc. and released to the public domain, |
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* as explained at http://creativecommons.org/licenses/publicdomain. |
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*/ |
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package java.util; |
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import java.io.*; |
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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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1.2 |
* {@link Stack} when used as a stack, and faster than {@link LinkedList} |
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1.1 |
* when used as a queue. |
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* |
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* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time. |
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* Exceptions include {@link #remove(Object) remove}, {@link |
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* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence |
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* removeLastOccurrence}, {@link #contains contains }, {@link #iterator |
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* iterator.remove()}, and the bulk operations, all of which run in linear |
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* time. |
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* |
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* <p>The iterators returned by this class's <tt>iterator</tt> method are |
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* <i>fail-fast</i>: If the deque is modified at any time after the iterator |
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* is created, in any way except through the iterator's own remove method, the |
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* iterator will generally throw a {@link ConcurrentModificationException}. |
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* Thus, in the face of concurrent modification, the iterator fails quickly |
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* and cleanly, rather than risking arbitrary, non-deterministic behavior at |
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* an undetermined time in the 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 <tt>ConcurrentModificationException</tt> 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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* optional methods of the {@link Collection} and {@link |
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* Iterator} interfaces. This class is a member of the <a |
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* href="{@docRoot}/../guide/collections/index.html"> Java Collections |
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* Framework</a>. |
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* |
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* @author Josh Bloch and Doug Lea |
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* @since 1.6 |
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* @param <E> the type of elements held in this collection |
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*/ |
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public class ArrayDeque<E> extends AbstractCollection<E> |
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implements Deque<E>, Cloneable, Serializable |
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{ |
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/** |
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* The array in which the elements of in the deque are stored. |
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* The capacity of the deque is the length of this array, which is |
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* always a power of two. The array is never allowed to become |
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* full, except transiently within an addX method where it is |
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* resized (see doubleCapacity) immediately upon becoming full, |
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* thus avoiding head and tail wrapping around to equal each |
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* other. We also guarantee that all array cells not holding |
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* deque elements are always null. |
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*/ |
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private transient E[] elements; |
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/** |
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* The index of the element at the head of the deque (which is the |
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* element that would be removed by remove() or pop()); or an |
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* arbitrary number equal to tail if the deque is empty. |
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*/ |
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private transient int head; |
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/** |
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* The index at which the next element would be added to the tail |
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* of the deque (via addLast(E), add(E), or push(E)). |
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*/ |
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private transient int tail; |
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/** |
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* The minimum capacity that we'll use for a newly created deque. |
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* Must be a power of 2. |
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*/ |
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private static final int MIN_INITIAL_CAPACITY = 8; |
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// ****** Array allocation and resizing utilities ****** |
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/** |
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* Allocate empty array to hold the given number of elements. |
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* |
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* @param numElements the number of elements to hold. |
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*/ |
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private void allocateElements(int numElements) { |
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int initialCapacity = MIN_INITIAL_CAPACITY; |
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// Find the best power of two to hold elements. |
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// Tests "<=" because arrays aren't kept full. |
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if (numElements >= initialCapacity) { |
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initialCapacity = numElements; |
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initialCapacity |= (initialCapacity >>> 1); |
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initialCapacity |= (initialCapacity >>> 2); |
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initialCapacity |= (initialCapacity >>> 4); |
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initialCapacity |= (initialCapacity >>> 8); |
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initialCapacity |= (initialCapacity >>> 16); |
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initialCapacity++; |
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if (initialCapacity < 0) // Too many elements, must back off |
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initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements |
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} |
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elements = (E[]) new Object[initialCapacity]; |
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} |
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/** |
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* Double the capacity of this deque. Call only when full, i.e., |
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* when head and tail have wrapped around to become equal. |
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*/ |
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private void doubleCapacity() { |
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assert head == tail; |
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int p = head; |
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int n = elements.length; |
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int r = n - p; // number of elements to the right of p |
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int newCapacity = n << 1; |
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if (newCapacity < 0) |
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throw new IllegalStateException("Sorry, deque too big"); |
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Object[] a = new Object[newCapacity]; |
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System.arraycopy(elements, p, a, 0, r); |
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System.arraycopy(elements, 0, a, r, p); |
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elements = (E[])a; |
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head = 0; |
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tail = n; |
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} |
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/** |
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* Copy the elements from our element array into the specified array, |
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* in order (from first to last element in the deque). It is assumed |
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* that the array is large enough to hold all elements in the deque. |
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* |
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* @return its argument |
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*/ |
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private <T> T[] copyElements(T[] a) { |
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if (head < tail) { |
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System.arraycopy(elements, head, a, 0, size()); |
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} else if (head > tail) { |
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int headPortionLen = elements.length - head; |
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System.arraycopy(elements, head, a, 0, headPortionLen); |
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System.arraycopy(elements, 0, a, headPortionLen, tail); |
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} |
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return a; |
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} |
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/** |
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* Constructs an empty array deque with the 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 = (E[]) new Object[16]; |
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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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allocateElements(numElements); |
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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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allocateElements(c.size()); |
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addAll(c); |
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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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* Inserts the specified element to the front this deque. |
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* |
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* @param e the element to insert |
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* @throws NullPointerException if <tt>e</tt> is null |
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*/ |
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public void addFirst(E e) { |
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if (e == null) |
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throw new NullPointerException(); |
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elements[head = (head - 1) & (elements.length - 1)] = e; |
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if (head == tail) |
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doubleCapacity(); |
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} |
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/** |
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* Inserts the specified element to the end this deque. |
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* This method is equivalent to {@link Collection#add} and |
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* {@link #push}. |
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* |
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* @param e the element to insert |
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* @throws NullPointerException if <tt>e</tt> is null |
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*/ |
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public void addLast(E e) { |
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if (e == null) |
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throw new NullPointerException(); |
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elements[tail] = e; |
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if ( (tail = (tail + 1) & (elements.length - 1)) == head) |
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doubleCapacity(); |
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} |
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/** |
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* Retrieves and removes the first element of this deque, or |
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* <tt>null</tt> if this deque is empty. |
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* |
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* @return the first element of this deque, or <tt>null</tt> if |
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* this deque is empty |
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*/ |
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public E pollFirst() { |
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int h = head; |
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E result = elements[h]; // Element is null if deque empty |
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if (result == null) |
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return null; |
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elements[h] = null; // Must null out slot |
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head = (h + 1) & (elements.length - 1); |
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return result; |
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} |
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/** |
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* Retrieves and removes the last element of this deque, or |
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* <tt>null</tt> if this deque is empty. |
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* |
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* @return the last element of this deque, or <tt>null</tt> if |
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* this deque is empty |
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*/ |
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public E pollLast() { |
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int t = (tail - 1) & (elements.length - 1); |
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E result = elements[t]; |
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if (result == null) |
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return null; |
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elements[t] = null; |
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tail = t; |
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return result; |
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} |
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/** |
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* Inserts the specified element to the front this deque. |
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* |
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* @param e the element to insert |
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* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
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* @throws NullPointerException if <tt>e</tt> 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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* Inserts the specified element to the end this deque. |
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* |
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* @param e the element to insert |
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* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
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* @throws NullPointerException if <tt>e</tt> 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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} |
273 |
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274 |
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/** |
275 |
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* Retrieves and removes the first element of this deque. This method |
276 |
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* differs from the <tt>pollFirst</tt> method in that it throws an |
277 |
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* exception if this deque is empty. |
278 |
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* |
279 |
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* @return the first element of this deque |
280 |
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* @throws NoSuchElementException if this deque is empty |
281 |
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*/ |
282 |
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public E removeFirst() { |
283 |
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E x = pollFirst(); |
284 |
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if (x == null) |
285 |
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throw new NoSuchElementException(); |
286 |
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return x; |
287 |
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} |
288 |
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289 |
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/** |
290 |
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* Retrieves and removes the last element of this deque. This method |
291 |
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* differs from the <tt>pollLast</tt> method in that it throws an |
292 |
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* exception if this deque is empty. |
293 |
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* |
294 |
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* @return the last element of this deque |
295 |
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* @throws NoSuchElementException if this deque is empty |
296 |
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*/ |
297 |
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public E removeLast() { |
298 |
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E x = pollLast(); |
299 |
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if (x == null) |
300 |
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throw new NoSuchElementException(); |
301 |
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return x; |
302 |
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} |
303 |
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304 |
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/** |
305 |
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* Retrieves, but does not remove, the first element of this deque, |
306 |
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* returning <tt>null</tt> if this deque is empty. |
307 |
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* |
308 |
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* @return the first element of this deque, or <tt>null</tt> if |
309 |
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* this deque is empty |
310 |
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*/ |
311 |
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public E peekFirst() { |
312 |
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return elements[head]; // elements[head] is null if deque empty |
313 |
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} |
314 |
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315 |
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/** |
316 |
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* Retrieves, but does not remove, the last element of this deque, |
317 |
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* returning <tt>null</tt> if this deque is empty. |
318 |
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* |
319 |
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* @return the last element of this deque, or <tt>null</tt> if this deque |
320 |
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* is empty |
321 |
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*/ |
322 |
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public E peekLast() { |
323 |
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return elements[(tail - 1) & (elements.length - 1)]; |
324 |
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} |
325 |
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326 |
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/** |
327 |
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* Retrieves, but does not remove, the first element of this |
328 |
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* deque. This method differs from the <tt>peek</tt> method only |
329 |
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* in that it throws an exception if this deque is empty. |
330 |
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* |
331 |
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* @return the first element of this deque |
332 |
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* @throws NoSuchElementException if this deque is empty |
333 |
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*/ |
334 |
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public E getFirst() { |
335 |
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E x = elements[head]; |
336 |
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if (x == null) |
337 |
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throw new NoSuchElementException(); |
338 |
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return x; |
339 |
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} |
340 |
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341 |
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/** |
342 |
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* Retrieves, but does not remove, the last element of this |
343 |
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* deque. This method differs from the <tt>peek</tt> method only |
344 |
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* in that it throws an exception if this deque is empty. |
345 |
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* |
346 |
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* @return the last element of this deque |
347 |
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* @throws NoSuchElementException if this deque is empty |
348 |
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*/ |
349 |
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public E getLast() { |
350 |
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E x = elements[(tail - 1) & (elements.length - 1)]; |
351 |
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if (x == null) |
352 |
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throw new NoSuchElementException(); |
353 |
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return x; |
354 |
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} |
355 |
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356 |
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/** |
357 |
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* Removes the first occurrence of the specified element in this |
358 |
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* deque (when traversing the deque from head to tail). If the deque |
359 |
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* does not contain the element, it is unchanged. |
360 |
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* |
361 |
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* @param e element to be removed from this deque, if present |
362 |
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* @return <tt>true</tt> if the deque contained the specified element |
363 |
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*/ |
364 |
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public boolean removeFirstOccurrence(Object e) { |
365 |
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if (e == null) |
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return false; |
367 |
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int mask = elements.length - 1; |
368 |
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int i = head; |
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E x; |
370 |
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while ( (x = elements[i]) != null) { |
371 |
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if (e.equals(x)) { |
372 |
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delete(i); |
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return true; |
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} |
375 |
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i = (i + 1) & mask; |
376 |
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} |
377 |
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return false; |
378 |
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} |
379 |
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380 |
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/** |
381 |
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* Removes the last occurrence of the specified element in this |
382 |
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* deque (when traversing the deque from head to tail). If the deque |
383 |
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* does not contain the element, it is unchanged. |
384 |
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* |
385 |
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* @param e element to be removed from this deque, if present |
386 |
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* @return <tt>true</tt> if the deque contained the specified element |
387 |
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*/ |
388 |
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public boolean removeLastOccurrence(Object e) { |
389 |
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if (e == null) |
390 |
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return false; |
391 |
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int mask = elements.length - 1; |
392 |
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int i = (tail - 1) & mask; |
393 |
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E x; |
394 |
|
|
while ( (x = elements[i]) != null) { |
395 |
|
|
if (e.equals(x)) { |
396 |
|
|
delete(i); |
397 |
|
|
return true; |
398 |
|
|
} |
399 |
|
|
i = (i - 1) & mask; |
400 |
|
|
} |
401 |
|
|
return false; |
402 |
|
|
} |
403 |
|
|
|
404 |
|
|
// *** Queue methods *** |
405 |
|
|
|
406 |
|
|
/** |
407 |
|
|
* Inserts the specified element to the end of this deque. |
408 |
|
|
* |
409 |
|
|
* <p>This method is equivalent to {@link #offerLast}. |
410 |
|
|
* |
411 |
|
|
* @param e the element to insert |
412 |
|
|
* @return <tt>true</tt> (as per the spec for {@link Queue#offer}) |
413 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
414 |
|
|
*/ |
415 |
|
|
public boolean offer(E e) { |
416 |
|
|
return offerLast(e); |
417 |
|
|
} |
418 |
|
|
|
419 |
|
|
/** |
420 |
|
|
* Inserts the specified element to the end of this deque. |
421 |
|
|
* |
422 |
|
|
* <p>This method is equivalent to {@link #addLast}. |
423 |
|
|
* |
424 |
|
|
* @param e the element to insert |
425 |
|
|
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
426 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
427 |
|
|
*/ |
428 |
|
|
public boolean add(E e) { |
429 |
|
|
addLast(e); |
430 |
|
|
return true; |
431 |
|
|
} |
432 |
|
|
|
433 |
|
|
/** |
434 |
|
|
* Retrieves and removes the head of the queue represented by |
435 |
|
|
* this deque, or <tt>null</tt> if this deque is empty. In other words, |
436 |
|
|
* retrieves and removes the first element of this deque, or <tt>null</tt> |
437 |
|
|
* if this deque is empty. |
438 |
|
|
* |
439 |
|
|
* <p>This method is equivalent to {@link #pollFirst}. |
440 |
|
|
* |
441 |
|
|
* @return the first element of this deque, or <tt>null</tt> if |
442 |
|
|
* this deque is empty |
443 |
|
|
*/ |
444 |
|
|
public E poll() { |
445 |
|
|
return pollFirst(); |
446 |
|
|
} |
447 |
|
|
|
448 |
|
|
/** |
449 |
|
|
* Retrieves and removes the head of the queue represented by this deque. |
450 |
|
|
* This method differs from the <tt>poll</tt> method in that it throws an |
451 |
|
|
* exception if this deque is empty. |
452 |
|
|
* |
453 |
|
|
* <p>This method is equivalent to {@link #removeFirst}. |
454 |
|
|
* |
455 |
|
|
* @return the head of the queue represented by this deque |
456 |
|
|
* @throws NoSuchElementException if this deque is empty |
457 |
|
|
*/ |
458 |
|
|
public E remove() { |
459 |
|
|
return removeFirst(); |
460 |
|
|
} |
461 |
|
|
|
462 |
|
|
/** |
463 |
|
|
* Retrieves, but does not remove, the head of the queue represented by |
464 |
|
|
* this deque, returning <tt>null</tt> if this deque is empty. |
465 |
|
|
* |
466 |
|
|
* <p>This method is equivalent to {@link #peekFirst} |
467 |
|
|
* |
468 |
|
|
* @return the head of the queue represented by this deque, or |
469 |
|
|
* <tt>null</tt> if this deque is empty |
470 |
|
|
*/ |
471 |
|
|
public E peek() { |
472 |
|
|
return peekFirst(); |
473 |
|
|
} |
474 |
|
|
|
475 |
|
|
/** |
476 |
|
|
* Retrieves, but does not remove, the head of the queue represented by |
477 |
|
|
* this deque. This method differs from the <tt>peek</tt> method only in |
478 |
|
|
* that it throws an exception if this deque is empty. |
479 |
|
|
* |
480 |
|
|
* <p>This method is equivalent to {@link #getFirst} |
481 |
|
|
* |
482 |
|
|
* @return the head of the queue represented by this deque |
483 |
|
|
* @throws NoSuchElementException if this deque is empty |
484 |
|
|
*/ |
485 |
|
|
public E element() { |
486 |
|
|
return getFirst(); |
487 |
|
|
} |
488 |
|
|
|
489 |
|
|
// *** Stack methods *** |
490 |
|
|
|
491 |
|
|
/** |
492 |
|
|
* Pushes an element onto the stack represented by this deque. In other |
493 |
|
|
* words, inserts the element to the front this deque. |
494 |
|
|
* |
495 |
|
|
* <p>This method is equivalent to {@link #addFirst}. |
496 |
|
|
* |
497 |
|
|
* @param e the element to push |
498 |
|
|
* @throws NullPointerException if <tt>e</tt> is null |
499 |
|
|
*/ |
500 |
|
|
public void push(E e) { |
501 |
|
|
addFirst(e); |
502 |
|
|
} |
503 |
|
|
|
504 |
|
|
/** |
505 |
|
|
* Pops an element from the stack represented by this deque. In other |
506 |
dl |
1.2 |
* words, removes and returns the first element of this deque. |
507 |
dl |
1.1 |
* |
508 |
|
|
* <p>This method is equivalent to {@link #removeFirst()}. |
509 |
|
|
* |
510 |
|
|
* @return the element at the front of this deque (which is the top |
511 |
|
|
* of the stack represented by this deque) |
512 |
|
|
* @throws NoSuchElementException if this deque is empty |
513 |
|
|
*/ |
514 |
|
|
public E pop() { |
515 |
|
|
return removeFirst(); |
516 |
|
|
} |
517 |
|
|
|
518 |
|
|
/** |
519 |
|
|
* Remove the element at the specified position in the elements array, |
520 |
|
|
* adjusting head, tail, and size as necessary. This can result in |
521 |
|
|
* motion of elements backwards or forwards in the array. |
522 |
|
|
* |
523 |
dl |
1.3 |
* <p>This method is called delete rather than remove to emphasize |
524 |
dl |
1.2 |
* that its semantics differ from those of List.remove(int). |
525 |
dl |
1.1 |
* |
526 |
|
|
* @return true if elements moved backwards |
527 |
|
|
*/ |
528 |
|
|
private boolean delete(int i) { |
529 |
|
|
// Case 1: Deque doesn't wrap |
530 |
|
|
// Case 2: Deque does wrap and removed element is in the head portion |
531 |
|
|
if ((head < tail || tail == 0) || i >= head) { |
532 |
|
|
System.arraycopy(elements, head, elements, head + 1, i - head); |
533 |
|
|
elements[head] = null; |
534 |
|
|
head = (head + 1) & (elements.length - 1); |
535 |
|
|
return false; |
536 |
|
|
} |
537 |
|
|
|
538 |
|
|
// Case 3: Deque wraps and removed element is in the tail portion |
539 |
|
|
tail--; |
540 |
|
|
System.arraycopy(elements, i + 1, elements, i, tail - i); |
541 |
|
|
elements[tail] = null; |
542 |
|
|
return true; |
543 |
|
|
} |
544 |
|
|
|
545 |
|
|
// *** Collection Methods *** |
546 |
|
|
|
547 |
|
|
/** |
548 |
|
|
* Returns the number of elements in this deque. |
549 |
|
|
* |
550 |
|
|
* @return the number of elements in this deque |
551 |
|
|
*/ |
552 |
|
|
public int size() { |
553 |
|
|
return (tail - head) & (elements.length - 1); |
554 |
|
|
} |
555 |
|
|
|
556 |
|
|
/** |
557 |
|
|
* Returns <tt>true</tt> if this collection contains no elements.<p> |
558 |
|
|
* |
559 |
|
|
* @return <tt>true</tt> if this collection contains no elements. |
560 |
|
|
*/ |
561 |
|
|
public boolean isEmpty() { |
562 |
|
|
return head == tail; |
563 |
|
|
} |
564 |
|
|
|
565 |
|
|
/** |
566 |
|
|
* Returns an iterator over the elements in this deque. The elements |
567 |
|
|
* will be ordered from first (head) to last (tail). This is the same |
568 |
|
|
* order that elements would be dequeued (via successive calls to |
569 |
|
|
* {@link #remove} or popped (via successive calls to {@link #pop}). |
570 |
|
|
* |
571 |
|
|
* @return an <tt>Iterator</tt> over the elements in this deque |
572 |
|
|
*/ |
573 |
|
|
public Iterator<E> iterator() { |
574 |
|
|
return new DeqIterator(); |
575 |
|
|
} |
576 |
|
|
|
577 |
|
|
private class DeqIterator implements Iterator<E> { |
578 |
|
|
/** |
579 |
|
|
* Index of element to be returned by subsequent call to next. |
580 |
|
|
*/ |
581 |
|
|
private int cursor = head; |
582 |
|
|
|
583 |
|
|
/** |
584 |
|
|
* Tail recorded at construction (also in remove), to stop |
585 |
|
|
* iterator and also to check for comodification. |
586 |
|
|
*/ |
587 |
|
|
private int fence = tail; |
588 |
|
|
|
589 |
|
|
/** |
590 |
|
|
* Index of element returned by most recent call to next. |
591 |
|
|
* Reset to -1 if element is deleted by a call to remove. |
592 |
|
|
*/ |
593 |
|
|
private int lastRet = -1; |
594 |
|
|
|
595 |
|
|
public boolean hasNext() { |
596 |
|
|
return cursor != fence; |
597 |
|
|
} |
598 |
|
|
|
599 |
|
|
public E next() { |
600 |
|
|
E result; |
601 |
|
|
if (cursor == fence) |
602 |
|
|
throw new NoSuchElementException(); |
603 |
|
|
// This check doesn't catch all possible comodifications, |
604 |
|
|
// but does catch the ones that corrupt traversal |
605 |
|
|
if (tail != fence || (result = elements[cursor]) == null) |
606 |
|
|
throw new ConcurrentModificationException(); |
607 |
|
|
lastRet = cursor; |
608 |
|
|
cursor = (cursor + 1) & (elements.length - 1); |
609 |
|
|
return result; |
610 |
|
|
} |
611 |
|
|
|
612 |
|
|
public void remove() { |
613 |
|
|
if (lastRet < 0) |
614 |
|
|
throw new IllegalStateException(); |
615 |
|
|
if (delete(lastRet)) |
616 |
|
|
cursor--; |
617 |
|
|
lastRet = -1; |
618 |
|
|
fence = tail; |
619 |
|
|
} |
620 |
|
|
} |
621 |
|
|
|
622 |
|
|
/** |
623 |
|
|
* Returns <tt>true</tt> if this deque contains the specified |
624 |
|
|
* element. More formally, returns <tt>true</tt> if and only if this |
625 |
|
|
* deque contains at least one element <tt>e</tt> such that |
626 |
|
|
* <tt>e.equals(o)</tt>. |
627 |
|
|
* |
628 |
|
|
* @param o object to be checked for containment in this deque |
629 |
|
|
* @return <tt>true</tt> if this deque contains the specified element |
630 |
|
|
*/ |
631 |
|
|
public boolean contains(Object o) { |
632 |
|
|
if (o == null) |
633 |
|
|
return false; |
634 |
|
|
int mask = elements.length - 1; |
635 |
|
|
int i = head; |
636 |
|
|
E x; |
637 |
|
|
while ( (x = elements[i]) != null) { |
638 |
|
|
if (o.equals(x)) |
639 |
|
|
return true; |
640 |
|
|
i = (i + 1) & mask; |
641 |
|
|
} |
642 |
|
|
return false; |
643 |
|
|
} |
644 |
|
|
|
645 |
|
|
/** |
646 |
|
|
* Removes a single instance of the specified element from this deque. |
647 |
|
|
* This method is equivalent to {@link #removeFirstOccurrence}. |
648 |
|
|
* |
649 |
|
|
* @param e element to be removed from this deque, if present |
650 |
|
|
* @return <tt>true</tt> if this deque contained the specified element |
651 |
|
|
*/ |
652 |
|
|
public boolean remove(Object e) { |
653 |
|
|
return removeFirstOccurrence(e); |
654 |
|
|
} |
655 |
|
|
|
656 |
|
|
/** |
657 |
|
|
* Removes all of the elements from this deque. |
658 |
|
|
*/ |
659 |
|
|
public void clear() { |
660 |
|
|
int h = head; |
661 |
|
|
int t = tail; |
662 |
|
|
if (h != t) { // clear all cells |
663 |
|
|
head = tail = 0; |
664 |
|
|
int i = h; |
665 |
|
|
int mask = elements.length - 1; |
666 |
|
|
do { |
667 |
|
|
elements[i] = null; |
668 |
|
|
i = (i + 1) & mask; |
669 |
|
|
} while(i != t); |
670 |
|
|
} |
671 |
|
|
} |
672 |
|
|
|
673 |
|
|
/** |
674 |
|
|
* Returns an array containing all of the elements in this list |
675 |
|
|
* in the correct order. |
676 |
|
|
* |
677 |
|
|
* @return an array containing all of the elements in this list |
678 |
|
|
* in the correct order |
679 |
|
|
*/ |
680 |
|
|
public Object[] toArray() { |
681 |
|
|
return copyElements(new Object[size()]); |
682 |
|
|
} |
683 |
|
|
|
684 |
|
|
/** |
685 |
|
|
* Returns an array containing all of the elements in this deque in the |
686 |
|
|
* correct order; the runtime type of the returned array is that of the |
687 |
|
|
* specified array. If the deque fits in the specified array, it is |
688 |
|
|
* returned therein. Otherwise, a new array is allocated with the runtime |
689 |
|
|
* type of the specified array and the size of this deque. |
690 |
|
|
* |
691 |
|
|
* <p>If the deque fits in the specified array with room to spare (i.e., |
692 |
|
|
* the array has more elements than the deque), the element in the array |
693 |
|
|
* immediately following the end of the collection is set to <tt>null</tt>. |
694 |
|
|
* |
695 |
|
|
* @param a the array into which the elements of the deque are to |
696 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
697 |
|
|
* same runtime type is allocated for this purpose |
698 |
|
|
* @return an array containing the elements of the deque |
699 |
|
|
* @throws ArrayStoreException if the runtime type of a is not a supertype |
700 |
|
|
* of the runtime type of every element in this deque |
701 |
|
|
*/ |
702 |
|
|
public <T> T[] toArray(T[] a) { |
703 |
|
|
int size = size(); |
704 |
|
|
if (a.length < size) |
705 |
|
|
a = (T[])java.lang.reflect.Array.newInstance( |
706 |
|
|
a.getClass().getComponentType(), size); |
707 |
|
|
copyElements(a); |
708 |
|
|
if (a.length > size) |
709 |
|
|
a[size] = null; |
710 |
|
|
return a; |
711 |
|
|
} |
712 |
|
|
|
713 |
|
|
// *** Object methods *** |
714 |
|
|
|
715 |
|
|
/** |
716 |
|
|
* Returns a copy of this deque. |
717 |
|
|
* |
718 |
|
|
* @return a copy of this deque |
719 |
|
|
*/ |
720 |
|
|
public ArrayDeque<E> clone() { |
721 |
|
|
try { |
722 |
|
|
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
723 |
|
|
// These two lines are currently faster than cloning the array: |
724 |
|
|
result.elements = (E[]) new Object[elements.length]; |
725 |
|
|
System.arraycopy(elements, 0, result.elements, 0, elements.length); |
726 |
|
|
return result; |
727 |
|
|
|
728 |
|
|
} catch (CloneNotSupportedException e) { |
729 |
|
|
throw new AssertionError(); |
730 |
|
|
} |
731 |
|
|
} |
732 |
|
|
|
733 |
|
|
/** |
734 |
|
|
* Appease the serialization gods. |
735 |
|
|
*/ |
736 |
|
|
private static final long serialVersionUID = 2340985798034038923L; |
737 |
|
|
|
738 |
|
|
/** |
739 |
|
|
* Serialize this deque. |
740 |
|
|
* |
741 |
|
|
* @serialData The current size (<tt>int</tt>) of the deque, |
742 |
|
|
* followed by all of its elements (each an object reference) in |
743 |
|
|
* first-to-last order. |
744 |
|
|
*/ |
745 |
|
|
private void writeObject(ObjectOutputStream s) throws IOException { |
746 |
|
|
s.defaultWriteObject(); |
747 |
|
|
|
748 |
|
|
// Write out size |
749 |
|
|
int size = size(); |
750 |
|
|
s.writeInt(size); |
751 |
|
|
|
752 |
|
|
// Write out elements in order. |
753 |
|
|
int i = head; |
754 |
|
|
int mask = elements.length - 1; |
755 |
|
|
for (int j = 0; j < size; j++) { |
756 |
|
|
s.writeObject(elements[i]); |
757 |
|
|
i = (i + 1) & mask; |
758 |
|
|
} |
759 |
|
|
} |
760 |
|
|
|
761 |
|
|
/** |
762 |
|
|
* Deserialize this deque. |
763 |
|
|
*/ |
764 |
|
|
private void readObject(ObjectInputStream s) |
765 |
|
|
throws IOException, ClassNotFoundException { |
766 |
|
|
s.defaultReadObject(); |
767 |
|
|
|
768 |
|
|
// Read in size and allocate array |
769 |
|
|
int size = s.readInt(); |
770 |
|
|
allocateElements(size); |
771 |
|
|
head = 0; |
772 |
|
|
tail = size; |
773 |
|
|
|
774 |
|
|
// Read in all elements in the proper order. |
775 |
|
|
for (int i = 0; i < size; i++) |
776 |
|
|
elements[i] = (E)s.readObject(); |
777 |
|
|
|
778 |
|
|
} |
779 |
|
|
} |