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/* |
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* Written by Josh Bloch of Google Inc. and released to the public domain, |
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* as explained at http://creativecommons.org/licenses/publicdomain. |
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* as explained at http://creativecommons.org/publicdomain/zero/1.0/. |
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*/ |
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package java.util; |
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import java.io.*; |
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|
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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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import jdk.internal.misc.SharedSecrets; |
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/** |
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* Resizable-array implementation of the {@link Deque} interface. Array |
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* {@link Stack} when used as a stack, and faster than {@link LinkedList} |
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* when used as a queue. |
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* |
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* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time. |
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* Exceptions include {@link #remove(Object) remove}, {@link |
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* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence |
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* removeLastOccurrence}, {@link #contains contains}, {@link #iterator |
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* iterator.remove()}, and the bulk operations, all of which run in linear |
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* time. |
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* <p>Most {@code ArrayDeque} operations run in amortized constant time. |
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* Exceptions include |
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* {@link #remove(Object) remove}, |
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* {@link #removeFirstOccurrence removeFirstOccurrence}, |
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* {@link #removeLastOccurrence removeLastOccurrence}, |
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* {@link #contains contains}, |
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* {@link #iterator iterator.remove()}, |
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* and the bulk operations, all of which run in linear time. |
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* |
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* <p>The iterators returned by this class's <tt>iterator</tt> method are |
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* <i>fail-fast</i>: If the deque is modified at any time after the iterator |
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* is created, in any way except through the iterator's own <tt>remove</tt> |
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* method, the iterator will generally throw a {@link |
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* <p>The iterators returned by this class's {@link #iterator() iterator} |
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* method are <em>fail-fast</em>: If the deque is modified at any time after |
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* the iterator is created, in any way except through the iterator's own |
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* {@code remove} method, the iterator will generally throw a {@link |
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* ConcurrentModificationException}. Thus, in the face of concurrent |
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* modification, the iterator fails quickly and cleanly, rather than risking |
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* arbitrary, non-deterministic behavior at an undetermined time in the |
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
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* as it is, generally speaking, impossible to make any hard guarantees in the |
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* presence of unsynchronized concurrent modification. Fail-fast iterators |
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* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
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* throw {@code ConcurrentModificationException} on a best-effort basis. |
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* Therefore, it would be wrong to write a program that depended on this |
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* exception for its correctness: <i>the fail-fast behavior of iterators |
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* should be used only to detect bugs.</i> |
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* 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}/../guide/collections/index.html"> |
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* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework"> |
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* Java Collections Framework</a>. |
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* |
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* @author Josh Bloch and Doug Lea |
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* @param <E> the type of elements held in this deque |
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* @since 1.6 |
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* @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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* VMs excel at optimizing simple array loops where indices are |
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* incrementing or decrementing over a valid slice, e.g. |
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* |
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* for (int i = start; i < end; i++) ... elements[i] |
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* |
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* Because in a circular array, elements are in general stored in |
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* two disjoint such slices, we help the VM by writing unusual |
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* nested loops for all traversals over the elements. Having only |
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* one hot inner loop body instead of two or three eases human |
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* maintenance and encourages VM loop inlining into the caller. |
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*/ |
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|
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/** |
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* The array in which the elements of the deque are stored. |
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* 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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* All array cells not holding deque elements are always null. |
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* The array always has at least one null slot (at tail). |
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*/ |
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private transient E[] elements; |
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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 equal to tail if the deque is empty. |
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* arbitrary number 0 <= head < elements.length equal to tail if |
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* the deque is empty. |
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*/ |
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private transient int head; |
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transient int head; |
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|
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/** |
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* The index at which the next element would be added to the tail |
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* of the deque (via addLast(E), add(E), or push(E)). |
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* of the deque (via addLast(E), add(E), or push(E)); |
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* elements[tail] is always null. |
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*/ |
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private transient int tail; |
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transient int tail; |
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|
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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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|
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// ****** Array allocation and resizing utilities ****** |
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|
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/** |
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* Allocate empty array to hold the given number of elements. |
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* |
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* @param numElements the number of elements to hold |
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*/ |
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private void allocateElements(int numElements) { |
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int initialCapacity = MIN_INITIAL_CAPACITY; |
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// Find the best power of two to hold elements. |
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// Tests "<=" because arrays aren't kept full. |
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if (numElements >= initialCapacity) { |
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initialCapacity = numElements; |
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initialCapacity |= (initialCapacity >>> 1); |
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initialCapacity |= (initialCapacity >>> 2); |
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initialCapacity |= (initialCapacity >>> 4); |
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initialCapacity |= (initialCapacity >>> 8); |
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initialCapacity |= (initialCapacity >>> 16); |
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initialCapacity++; |
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* The maximum size of array to allocate. |
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* Some VMs reserve some header words in an array. |
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* Attempts to allocate larger arrays may result in |
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* OutOfMemoryError: Requested array size exceeds VM limit |
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*/ |
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private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
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|
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/** |
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* Increases the capacity of this deque by at least the given amount. |
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* |
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* @param needed the required minimum extra capacity; must be positive |
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*/ |
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private void grow(int needed) { |
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// overflow-conscious code |
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final int oldCapacity = elements.length; |
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int newCapacity; |
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// Double capacity if small; else grow by 50% |
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int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1); |
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if (jump < needed |
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|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0) |
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newCapacity = newCapacity(needed, jump); |
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final Object[] es = elements = Arrays.copyOf(elements, newCapacity); |
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// Exceptionally, here tail == head needs to be disambiguated |
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if (tail < head || (tail == head && es[head] != null)) { |
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// wrap around; slide first leg forward to end of array |
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int newSpace = newCapacity - oldCapacity; |
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System.arraycopy(es, head, |
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es, head + newSpace, |
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oldCapacity - head); |
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for (int i = head, to = (head += newSpace); i < to; i++) |
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es[i] = null; |
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} |
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// checkInvariants(); |
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} |
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|
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if (initialCapacity < 0) // Too many elements, must back off |
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initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements |
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/** Capacity calculation for edge conditions, especially overflow. */ |
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private int newCapacity(int needed, int jump) { |
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final int oldCapacity = elements.length, minCapacity; |
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if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) { |
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if (minCapacity < 0) |
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throw new IllegalStateException("Sorry, deque too big"); |
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return Integer.MAX_VALUE; |
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} |
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elements = (E[]) new Object[initialCapacity]; |
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if (needed > jump) |
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return minCapacity; |
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return (oldCapacity + jump - MAX_ARRAY_SIZE < 0) |
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? oldCapacity + jump |
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: MAX_ARRAY_SIZE; |
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} |
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/** |
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* Double the capacity of this deque. Call only when full, i.e., |
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* when head and tail have wrapped around to become equal. |
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* Increases the internal storage of this collection, if necessary, |
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* to ensure that it can hold at least the given number of elements. |
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* |
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* @param minCapacity the desired minimum capacity |
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* @since TBD |
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*/ |
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private void doubleCapacity() { |
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assert head == tail; |
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int p = head; |
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int n = elements.length; |
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int r = n - p; // number of elements to the right of p |
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int newCapacity = n << 1; |
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if (newCapacity < 0) |
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throw new IllegalStateException("Sorry, deque too big"); |
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Object[] a = new Object[newCapacity]; |
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System.arraycopy(elements, p, a, 0, r); |
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System.arraycopy(elements, 0, a, r, p); |
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elements = (E[])a; |
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head = 0; |
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tail = n; |
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/* public */ void ensureCapacity(int minCapacity) { |
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int needed; |
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if ((needed = (minCapacity + 1 - elements.length)) > 0) |
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grow(needed); |
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// checkInvariants(); |
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} |
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/** |
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* Copies the elements from our element array into the specified array, |
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* in order (from first to last element in the deque). It is assumed |
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* that the array is large enough to hold all elements in the deque. |
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* Minimizes the internal storage of this collection. |
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* |
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* @return its argument |
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* @since TBD |
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*/ |
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private <T> T[] copyElements(T[] a) { |
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if (head < tail) { |
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System.arraycopy(elements, head, a, 0, size()); |
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} else if (head > tail) { |
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int headPortionLen = elements.length - head; |
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System.arraycopy(elements, head, a, 0, headPortionLen); |
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System.arraycopy(elements, 0, a, headPortionLen, tail); |
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/* public */ void trimToSize() { |
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int size; |
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if ((size = size()) + 1 < elements.length) { |
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elements = toArray(new Object[size + 1]); |
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head = 0; |
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tail = size; |
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} |
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return a; |
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// checkInvariants(); |
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} |
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|
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/** |
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* sufficient to hold 16 elements. |
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*/ |
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public ArrayDeque() { |
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elements = (E[]) new Object[16]; |
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elements = new Object[16]; |
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} |
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|
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/** |
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* Constructs an empty array deque with an initial capacity |
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* sufficient to hold the specified number of elements. |
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* |
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* @param numElements lower bound on initial capacity of the deque |
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* @param numElements lower bound on initial capacity of the deque |
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*/ |
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public ArrayDeque(int numElements) { |
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allocateElements(numElements); |
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elements = |
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new Object[(numElements < 1) ? 1 : |
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(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE : |
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numElements + 1]; |
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} |
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|
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/** |
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* @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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this(c.size()); |
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copyElements(c); |
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} |
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|
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/** |
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* Circularly increments i, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus. |
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*/ |
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static final int inc(int i, int modulus) { |
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if (++i >= modulus) i = 0; |
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return i; |
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} |
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|
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/** |
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* Circularly decrements i, mod modulus. |
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* Precondition and postcondition: 0 <= i < modulus. |
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*/ |
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static final int dec(int i, int modulus) { |
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if (--i < 0) i = modulus - 1; |
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return i; |
231 |
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} |
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|
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/** |
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* Circularly adds the given distance to index i, mod modulus. |
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* Precondition: 0 <= i < modulus, 0 <= distance <= modulus. |
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* @return index 0 <= i < modulus |
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*/ |
238 |
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static final int inc(int i, int distance, int modulus) { |
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if ((i += distance) - modulus >= 0) i -= modulus; |
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return i; |
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} |
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|
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/** |
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* Subtracts j from i, mod modulus. |
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* Index i must be logically ahead of index j. |
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* Precondition: 0 <= i < modulus, 0 <= j < modulus. |
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* @return the "circular distance" from j to i; corner case i == j |
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* is disambiguated to "empty", returning 0. |
249 |
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*/ |
250 |
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static final int sub(int i, int j, int modulus) { |
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if ((i -= j) < 0) i += modulus; |
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return i; |
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} |
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|
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/** |
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* Returns element at array index i. |
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* This is a slight abuse of generics, accepted by javac. |
258 |
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*/ |
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@SuppressWarnings("unchecked") |
260 |
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static final <E> E elementAt(Object[] es, int i) { |
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return (E) es[i]; |
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} |
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|
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/** |
265 |
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* A version of elementAt that checks for null elements. |
266 |
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* This check doesn't catch all possible comodifications, |
267 |
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* but does catch ones that corrupt traversal. |
268 |
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*/ |
269 |
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static final <E> E nonNullElementAt(Object[] es, int i) { |
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@SuppressWarnings("unchecked") E e = (E) es[i]; |
271 |
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if (e == null) |
272 |
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throw new ConcurrentModificationException(); |
273 |
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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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public void addFirst(E e) { |
287 |
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if (e == null) |
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throw new NullPointerException(); |
289 |
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elements[head = (head - 1) & (elements.length - 1)] = e; |
289 |
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final Object[] es = elements; |
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es[head = dec(head, es.length)] = e; |
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if (head == tail) |
292 |
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doubleCapacity(); |
292 |
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grow(1); |
293 |
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// checkInvariants(); |
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} |
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|
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/** |
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* Inserts the specified element at the end of this deque. |
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* This method is equivalent to {@link #add} and {@link #push}. |
298 |
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* |
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* <p>This method is equivalent to {@link #add}. |
300 |
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* |
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* @param e the element to add |
302 |
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* @throws NullPointerException if the specified element is null |
304 |
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public void addLast(E e) { |
305 |
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if (e == null) |
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throw new NullPointerException(); |
307 |
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elements[tail] = e; |
308 |
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if ( (tail = (tail + 1) & (elements.length - 1)) == head) |
309 |
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doubleCapacity(); |
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final Object[] es = elements; |
308 |
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es[tail] = e; |
309 |
> |
if (head == (tail = inc(tail, es.length))) |
310 |
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grow(1); |
311 |
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// checkInvariants(); |
312 |
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} |
313 |
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|
314 |
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/** |
315 |
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* Adds all of the elements in the specified collection at the end |
316 |
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* of this deque, as if by calling {@link #addLast} on each one, |
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* in the order that they are returned by the collection's iterator. |
318 |
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* |
319 |
> |
* @param c the elements to be inserted into this deque |
320 |
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* @return {@code true} if this deque changed as a result of the call |
321 |
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* @throws NullPointerException if the specified collection or any |
322 |
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* of its elements are null |
323 |
> |
*/ |
324 |
> |
public boolean addAll(Collection<? extends E> c) { |
325 |
> |
final int s, needed; |
326 |
> |
if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0) |
327 |
> |
grow(needed); |
328 |
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copyElements(c); |
329 |
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// checkInvariants(); |
330 |
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return size() > s; |
331 |
> |
} |
332 |
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|
333 |
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private void copyElements(Collection<? extends E> c) { |
334 |
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c.forEach(this::addLast); |
335 |
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} |
336 |
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|
337 |
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/** |
338 |
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* Inserts the specified element at the front of this deque. |
339 |
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* |
340 |
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* @param e the element to add |
341 |
< |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerFirst}) |
341 |
> |
* @return {@code true} (as specified by {@link Deque#offerFirst}) |
342 |
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* @throws NullPointerException if the specified element is null |
343 |
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*/ |
344 |
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public boolean offerFirst(E e) { |
350 |
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* Inserts the specified element at the end of this deque. |
351 |
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* |
352 |
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* @param e the element to add |
353 |
< |
* @return <tt>true</tt> (as per the spec for {@link Deque#offerLast}) |
353 |
> |
* @return {@code true} (as specified by {@link Deque#offerLast}) |
354 |
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* @throws NullPointerException if the specified element is null |
355 |
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*/ |
356 |
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public boolean offerLast(E e) { |
362 |
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* @throws NoSuchElementException {@inheritDoc} |
363 |
|
*/ |
364 |
|
public E removeFirst() { |
365 |
< |
E x = pollFirst(); |
366 |
< |
if (x == null) |
365 |
> |
E e = pollFirst(); |
366 |
> |
if (e == null) |
367 |
|
throw new NoSuchElementException(); |
368 |
< |
return x; |
368 |
> |
// checkInvariants(); |
369 |
> |
return e; |
370 |
|
} |
371 |
|
|
372 |
|
/** |
373 |
|
* @throws NoSuchElementException {@inheritDoc} |
374 |
|
*/ |
375 |
|
public E removeLast() { |
376 |
< |
E x = pollLast(); |
377 |
< |
if (x == null) |
376 |
> |
E e = pollLast(); |
377 |
> |
if (e == null) |
378 |
|
throw new NoSuchElementException(); |
379 |
< |
return x; |
379 |
> |
// checkInvariants(); |
380 |
> |
return e; |
381 |
|
} |
382 |
|
|
383 |
|
public E pollFirst() { |
384 |
< |
int h = head; |
385 |
< |
E result = elements[h]; // Element is null if deque empty |
386 |
< |
if (result == null) |
387 |
< |
return null; |
388 |
< |
elements[h] = null; // Must null out slot |
389 |
< |
head = (h + 1) & (elements.length - 1); |
390 |
< |
return result; |
384 |
> |
final Object[] es; |
385 |
> |
final int h; |
386 |
> |
E e = elementAt(es = elements, h = head); |
387 |
> |
if (e != null) { |
388 |
> |
es[h] = null; |
389 |
> |
head = inc(h, es.length); |
390 |
> |
} |
391 |
> |
// checkInvariants(); |
392 |
> |
return e; |
393 |
|
} |
394 |
|
|
395 |
|
public E pollLast() { |
396 |
< |
int t = (tail - 1) & (elements.length - 1); |
397 |
< |
E result = elements[t]; |
398 |
< |
if (result == null) |
399 |
< |
return null; |
400 |
< |
elements[t] = null; |
401 |
< |
tail = t; |
402 |
< |
return result; |
396 |
> |
final Object[] es; |
397 |
> |
final int t; |
398 |
> |
E e = elementAt(es = elements, t = dec(tail, es.length)); |
399 |
> |
if (e != null) |
400 |
> |
es[tail = t] = null; |
401 |
> |
// checkInvariants(); |
402 |
> |
return e; |
403 |
|
} |
404 |
|
|
405 |
|
/** |
406 |
|
* @throws NoSuchElementException {@inheritDoc} |
407 |
|
*/ |
408 |
|
public E getFirst() { |
409 |
< |
E x = elements[head]; |
410 |
< |
if (x == null) |
409 |
> |
E e = elementAt(elements, head); |
410 |
> |
if (e == null) |
411 |
|
throw new NoSuchElementException(); |
412 |
< |
return x; |
412 |
> |
// checkInvariants(); |
413 |
> |
return e; |
414 |
|
} |
415 |
|
|
416 |
|
/** |
417 |
|
* @throws NoSuchElementException {@inheritDoc} |
418 |
|
*/ |
419 |
|
public E getLast() { |
420 |
< |
E x = elements[(tail - 1) & (elements.length - 1)]; |
421 |
< |
if (x == null) |
420 |
> |
final Object[] es = elements; |
421 |
> |
E e = elementAt(es, dec(tail, es.length)); |
422 |
> |
if (e == null) |
423 |
|
throw new NoSuchElementException(); |
424 |
< |
return x; |
424 |
> |
// checkInvariants(); |
425 |
> |
return e; |
426 |
|
} |
427 |
|
|
428 |
|
public E peekFirst() { |
429 |
< |
return elements[head]; // elements[head] is null if deque empty |
429 |
> |
// checkInvariants(); |
430 |
> |
return elementAt(elements, head); |
431 |
|
} |
432 |
|
|
433 |
|
public E peekLast() { |
434 |
< |
return elements[(tail - 1) & (elements.length - 1)]; |
434 |
> |
// checkInvariants(); |
435 |
> |
final Object[] es; |
436 |
> |
return elementAt(es = elements, dec(tail, es.length)); |
437 |
|
} |
438 |
|
|
439 |
|
/** |
440 |
|
* Removes the first occurrence of the specified element in this |
441 |
|
* deque (when traversing the deque from head to tail). |
442 |
|
* If the deque does not contain the element, it is unchanged. |
443 |
< |
* More formally, removes the first element <tt>e</tt> such that |
444 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
445 |
< |
* Returns true if this deque contained the specified element (or |
446 |
< |
* equivalently, if this deque changed as a result of the call). |
443 |
> |
* More formally, removes the first element {@code e} such that |
444 |
> |
* {@code o.equals(e)} (if such an element exists). |
445 |
> |
* Returns {@code true} if this deque contained the specified element |
446 |
> |
* (or equivalently, if this deque changed as a result of the call). |
447 |
|
* |
448 |
|
* @param o element to be removed from this deque, if present |
449 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
449 |
> |
* @return {@code true} if the deque contained the specified element |
450 |
|
*/ |
451 |
|
public boolean removeFirstOccurrence(Object o) { |
452 |
< |
if (o == null) |
453 |
< |
return false; |
454 |
< |
int mask = elements.length - 1; |
455 |
< |
int i = head; |
456 |
< |
E x; |
457 |
< |
while ( (x = elements[i]) != null) { |
458 |
< |
if (o.equals(x)) { |
459 |
< |
delete(i); |
460 |
< |
return true; |
452 |
> |
if (o != null) { |
453 |
> |
final Object[] es = elements; |
454 |
> |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
455 |
> |
; i = 0, to = end) { |
456 |
> |
for (; i < to; i++) |
457 |
> |
if (o.equals(es[i])) { |
458 |
> |
delete(i); |
459 |
> |
return true; |
460 |
> |
} |
461 |
> |
if (to == end) break; |
462 |
|
} |
333 |
– |
i = (i + 1) & mask; |
463 |
|
} |
464 |
|
return false; |
465 |
|
} |
468 |
|
* Removes the last occurrence of the specified element in this |
469 |
|
* deque (when traversing the deque from head to tail). |
470 |
|
* If the deque does not contain the element, it is unchanged. |
471 |
< |
* More formally, removes the last element <tt>e</tt> such that |
472 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
473 |
< |
* Returns true if this deque contained the specified element (or |
474 |
< |
* equivalently, if this deque changed as a result of the call). |
471 |
> |
* More formally, removes the last element {@code e} such that |
472 |
> |
* {@code o.equals(e)} (if such an element exists). |
473 |
> |
* Returns {@code true} if this deque contained the specified element |
474 |
> |
* (or equivalently, if this deque changed as a result of the call). |
475 |
|
* |
476 |
|
* @param o element to be removed from this deque, if present |
477 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
477 |
> |
* @return {@code true} if the deque contained the specified element |
478 |
|
*/ |
479 |
|
public boolean removeLastOccurrence(Object o) { |
480 |
< |
if (o == null) |
481 |
< |
return false; |
482 |
< |
int mask = elements.length - 1; |
483 |
< |
int i = (tail - 1) & mask; |
484 |
< |
E x; |
485 |
< |
while ( (x = elements[i]) != null) { |
486 |
< |
if (o.equals(x)) { |
487 |
< |
delete(i); |
488 |
< |
return true; |
480 |
> |
if (o != null) { |
481 |
> |
final Object[] es = elements; |
482 |
> |
for (int i = tail, end = head, to = (i >= end) ? end : 0; |
483 |
> |
; i = es.length, to = end) { |
484 |
> |
for (i--; i > to - 1; i--) |
485 |
> |
if (o.equals(es[i])) { |
486 |
> |
delete(i); |
487 |
> |
return true; |
488 |
> |
} |
489 |
> |
if (to == end) break; |
490 |
|
} |
361 |
– |
i = (i - 1) & mask; |
491 |
|
} |
492 |
|
return false; |
493 |
|
} |
500 |
|
* <p>This method is equivalent to {@link #addLast}. |
501 |
|
* |
502 |
|
* @param e the element to add |
503 |
< |
* @return <tt>true</tt> (as per the spec for {@link Collection#add}) |
503 |
> |
* @return {@code true} (as specified by {@link Collection#add}) |
504 |
|
* @throws NullPointerException if the specified element is null |
505 |
|
*/ |
506 |
|
public boolean add(E e) { |
514 |
|
* <p>This method is equivalent to {@link #offerLast}. |
515 |
|
* |
516 |
|
* @param e the element to add |
517 |
< |
* @return <tt>true</tt> (as per the spec for {@link Queue#offer}) |
517 |
> |
* @return {@code true} (as specified by {@link Queue#offer}) |
518 |
|
* @throws NullPointerException if the specified element is null |
519 |
|
*/ |
520 |
|
public boolean offer(E e) { |
523 |
|
|
524 |
|
/** |
525 |
|
* Retrieves and removes the head of the queue represented by this deque. |
526 |
< |
* This method differs from {@link #poll} only in that it throws an |
527 |
< |
* exception if this deque is empty. |
526 |
> |
* |
527 |
> |
* This method differs from {@link #poll() poll()} only in that it |
528 |
> |
* throws an exception if this deque is empty. |
529 |
|
* |
530 |
|
* <p>This method is equivalent to {@link #removeFirst}. |
531 |
|
* |
539 |
|
/** |
540 |
|
* Retrieves and removes the head of the queue represented by this deque |
541 |
|
* (in other words, the first element of this deque), or returns |
542 |
< |
* <tt>null</tt> if this deque is empty. |
542 |
> |
* {@code null} if this deque is empty. |
543 |
|
* |
544 |
|
* <p>This method is equivalent to {@link #pollFirst}. |
545 |
|
* |
546 |
|
* @return the head of the queue represented by this deque, or |
547 |
< |
* <tt>null</tt> if this deque is empty |
547 |
> |
* {@code null} if this deque is empty |
548 |
|
*/ |
549 |
|
public E poll() { |
550 |
|
return pollFirst(); |
552 |
|
|
553 |
|
/** |
554 |
|
* Retrieves, but does not remove, the head of the queue represented by |
555 |
< |
* this deque. This method differs from {@link #peek} only in that it |
556 |
< |
* throws an exception if this deque is empty. |
555 |
> |
* this deque. This method differs from {@link #peek peek} only in |
556 |
> |
* that it throws an exception if this deque is empty. |
557 |
|
* |
558 |
|
* <p>This method is equivalent to {@link #getFirst}. |
559 |
|
* |
566 |
|
|
567 |
|
/** |
568 |
|
* Retrieves, but does not remove, the head of the queue represented by |
569 |
< |
* this deque, or returns <tt>null</tt> if this deque is empty. |
569 |
> |
* this deque, or returns {@code null} if this deque is empty. |
570 |
|
* |
571 |
|
* <p>This method is equivalent to {@link #peekFirst}. |
572 |
|
* |
573 |
|
* @return the head of the queue represented by this deque, or |
574 |
< |
* <tt>null</tt> if this deque is empty |
574 |
> |
* {@code null} if this deque is empty |
575 |
|
*/ |
576 |
|
public E peek() { |
577 |
|
return peekFirst(); |
607 |
|
} |
608 |
|
|
609 |
|
/** |
610 |
< |
* Removes the element at the specified position in the elements array, |
611 |
< |
* adjusting head and tail as necessary. This can result in motion of |
612 |
< |
* elements backwards or forwards in the array. |
610 |
> |
* Removes the element at the specified position in the elements array. |
611 |
> |
* This can result in forward or backwards motion of array elements. |
612 |
> |
* We optimize for least element motion. |
613 |
|
* |
614 |
|
* <p>This method is called delete rather than remove to emphasize |
615 |
|
* that its semantics differ from those of {@link List#remove(int)}. |
616 |
|
* |
617 |
< |
* @return true if elements moved backwards |
617 |
> |
* @return true if elements near tail moved backwards |
618 |
|
*/ |
619 |
< |
private boolean delete(int i) { |
620 |
< |
int mask = elements.length - 1; |
621 |
< |
|
622 |
< |
// Invariant: head <= i < tail mod circularity |
623 |
< |
if (((i - head) & mask) >= ((tail - head) & mask)) |
624 |
< |
throw new ConcurrentModificationException(); |
625 |
< |
|
626 |
< |
// Case 1: Deque doesn't wrap |
627 |
< |
// Case 2: Deque does wrap and removed element is in the head portion |
628 |
< |
if (i >= head) { |
629 |
< |
System.arraycopy(elements, head, elements, head + 1, i - head); |
630 |
< |
elements[head] = null; |
631 |
< |
head = (head + 1) & mask; |
619 |
> |
boolean delete(int i) { |
620 |
> |
// checkInvariants(); |
621 |
> |
final Object[] es = elements; |
622 |
> |
final int capacity = es.length; |
623 |
> |
final int h, t; |
624 |
> |
// number of elements before to-be-deleted elt |
625 |
> |
final int front = sub(i, h = head, capacity); |
626 |
> |
// number of elements after to-be-deleted elt |
627 |
> |
final int back = sub(t = tail, i, capacity) - 1; |
628 |
> |
if (front < back) { |
629 |
> |
// move front elements forwards |
630 |
> |
if (h <= i) { |
631 |
> |
System.arraycopy(es, h, es, h + 1, front); |
632 |
> |
} else { // Wrap around |
633 |
> |
System.arraycopy(es, 0, es, 1, i); |
634 |
> |
es[0] = es[capacity - 1]; |
635 |
> |
System.arraycopy(es, h, es, h + 1, front - (i + 1)); |
636 |
> |
} |
637 |
> |
es[h] = null; |
638 |
> |
head = inc(h, capacity); |
639 |
> |
// checkInvariants(); |
640 |
|
return false; |
641 |
+ |
} else { |
642 |
+ |
// move back elements backwards |
643 |
+ |
tail = dec(t, capacity); |
644 |
+ |
if (i <= tail) { |
645 |
+ |
System.arraycopy(es, i + 1, es, i, back); |
646 |
+ |
} else { // Wrap around |
647 |
+ |
System.arraycopy(es, i + 1, es, i, capacity - (i + 1)); |
648 |
+ |
es[capacity - 1] = es[0]; |
649 |
+ |
System.arraycopy(es, 1, es, 0, t - 1); |
650 |
+ |
} |
651 |
+ |
es[tail] = null; |
652 |
+ |
// checkInvariants(); |
653 |
+ |
return true; |
654 |
|
} |
504 |
– |
|
505 |
– |
// Case 3: Deque wraps and removed element is in the tail portion |
506 |
– |
tail--; |
507 |
– |
System.arraycopy(elements, i + 1, elements, i, tail - i); |
508 |
– |
elements[tail] = null; |
509 |
– |
return true; |
655 |
|
} |
656 |
|
|
657 |
|
// *** Collection Methods *** |
662 |
|
* @return the number of elements in this deque |
663 |
|
*/ |
664 |
|
public int size() { |
665 |
< |
return (tail - head) & (elements.length - 1); |
665 |
> |
return sub(tail, head, elements.length); |
666 |
|
} |
667 |
|
|
668 |
|
/** |
669 |
< |
* Returns <tt>true</tt> if this deque contains no elements. |
669 |
> |
* Returns {@code true} if this deque contains no elements. |
670 |
|
* |
671 |
< |
* @return <tt>true</tt> if this deque contains no elements |
671 |
> |
* @return {@code true} if this deque contains no elements |
672 |
|
*/ |
673 |
|
public boolean isEmpty() { |
674 |
|
return head == tail; |
680 |
|
* order that elements would be dequeued (via successive calls to |
681 |
|
* {@link #remove} or popped (via successive calls to {@link #pop}). |
682 |
|
* |
683 |
< |
* @return an <tt>Iterator</tt> over the elements in this deque |
683 |
> |
* @return an iterator over the elements in this deque |
684 |
|
*/ |
685 |
|
public Iterator<E> iterator() { |
686 |
|
return new DeqIterator(); |
687 |
|
} |
688 |
|
|
689 |
+ |
public Iterator<E> descendingIterator() { |
690 |
+ |
return new DescendingIterator(); |
691 |
+ |
} |
692 |
+ |
|
693 |
|
private class DeqIterator implements Iterator<E> { |
694 |
< |
/** |
695 |
< |
* Index of element to be returned by subsequent call to next. |
547 |
< |
*/ |
548 |
< |
private int cursor = head; |
694 |
> |
/** Index of element to be returned by subsequent call to next. */ |
695 |
> |
int cursor; |
696 |
|
|
697 |
< |
/** |
698 |
< |
* Tail recorded at construction (also in remove), to stop |
552 |
< |
* iterator and also to check for comodification. |
553 |
< |
*/ |
554 |
< |
private int fence = tail; |
697 |
> |
/** Number of elements yet to be returned. */ |
698 |
> |
int remaining = size(); |
699 |
|
|
700 |
|
/** |
701 |
|
* Index of element returned by most recent call to next. |
702 |
|
* Reset to -1 if element is deleted by a call to remove. |
703 |
|
*/ |
704 |
< |
private int lastRet = -1; |
704 |
> |
int lastRet = -1; |
705 |
> |
|
706 |
> |
DeqIterator() { cursor = head; } |
707 |
|
|
708 |
< |
public boolean hasNext() { |
709 |
< |
return cursor != fence; |
708 |
> |
public final boolean hasNext() { |
709 |
> |
return remaining > 0; |
710 |
|
} |
711 |
|
|
712 |
|
public E next() { |
713 |
< |
E result; |
568 |
< |
if (cursor == fence) |
713 |
> |
if (remaining <= 0) |
714 |
|
throw new NoSuchElementException(); |
715 |
< |
// This check doesn't catch all possible comodifications, |
716 |
< |
// but does catch the ones that corrupt traversal |
717 |
< |
if (tail != fence || (result = elements[cursor]) == null) |
718 |
< |
throw new ConcurrentModificationException(); |
719 |
< |
lastRet = cursor; |
720 |
< |
cursor = (cursor + 1) & (elements.length - 1); |
721 |
< |
return result; |
715 |
> |
final Object[] es = elements; |
716 |
> |
E e = nonNullElementAt(es, cursor); |
717 |
> |
cursor = inc(lastRet = cursor, es.length); |
718 |
> |
remaining--; |
719 |
> |
return e; |
720 |
> |
} |
721 |
> |
|
722 |
> |
void postDelete(boolean leftShifted) { |
723 |
> |
if (leftShifted) |
724 |
> |
cursor = dec(cursor, elements.length); |
725 |
|
} |
726 |
|
|
727 |
< |
public void remove() { |
727 |
> |
public final void remove() { |
728 |
|
if (lastRet < 0) |
729 |
|
throw new IllegalStateException(); |
730 |
< |
if (delete(lastRet)) |
583 |
< |
cursor--; |
730 |
> |
postDelete(delete(lastRet)); |
731 |
|
lastRet = -1; |
732 |
< |
fence = tail; |
732 |
> |
} |
733 |
> |
|
734 |
> |
public void forEachRemaining(Consumer<? super E> action) { |
735 |
> |
Objects.requireNonNull(action); |
736 |
> |
int r; |
737 |
> |
if ((r = remaining) <= 0) |
738 |
> |
return; |
739 |
> |
remaining = 0; |
740 |
> |
final Object[] es = elements; |
741 |
> |
if (es[cursor] == null || sub(tail, cursor, es.length) != r) |
742 |
> |
throw new ConcurrentModificationException(); |
743 |
> |
for (int i = cursor, end = tail, to = (i <= end) ? end : es.length; |
744 |
> |
; i = 0, to = end) { |
745 |
> |
for (; i < to; i++) |
746 |
> |
action.accept(elementAt(es, i)); |
747 |
> |
if (to == end) { |
748 |
> |
if (end != tail) |
749 |
> |
throw new ConcurrentModificationException(); |
750 |
> |
lastRet = dec(end, es.length); |
751 |
> |
break; |
752 |
> |
} |
753 |
> |
} |
754 |
> |
} |
755 |
> |
} |
756 |
> |
|
757 |
> |
private class DescendingIterator extends DeqIterator { |
758 |
> |
DescendingIterator() { cursor = dec(tail, elements.length); } |
759 |
> |
|
760 |
> |
public final E next() { |
761 |
> |
if (remaining <= 0) |
762 |
> |
throw new NoSuchElementException(); |
763 |
> |
final Object[] es = elements; |
764 |
> |
E e = nonNullElementAt(es, cursor); |
765 |
> |
cursor = dec(lastRet = cursor, es.length); |
766 |
> |
remaining--; |
767 |
> |
return e; |
768 |
> |
} |
769 |
> |
|
770 |
> |
void postDelete(boolean leftShifted) { |
771 |
> |
if (!leftShifted) |
772 |
> |
cursor = inc(cursor, elements.length); |
773 |
> |
} |
774 |
> |
|
775 |
> |
public final void forEachRemaining(Consumer<? super E> action) { |
776 |
> |
Objects.requireNonNull(action); |
777 |
> |
int r; |
778 |
> |
if ((r = remaining) <= 0) |
779 |
> |
return; |
780 |
> |
remaining = 0; |
781 |
> |
final Object[] es = elements; |
782 |
> |
if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r) |
783 |
> |
throw new ConcurrentModificationException(); |
784 |
> |
for (int i = cursor, end = head, to = (i >= end) ? end : 0; |
785 |
> |
; i = es.length - 1, to = end) { |
786 |
> |
// hotspot generates faster code than for: i >= to ! |
787 |
> |
for (; i > to - 1; i--) |
788 |
> |
action.accept(elementAt(es, i)); |
789 |
> |
if (to == end) { |
790 |
> |
if (end != head) |
791 |
> |
throw new ConcurrentModificationException(); |
792 |
> |
lastRet = end; |
793 |
> |
break; |
794 |
> |
} |
795 |
> |
} |
796 |
|
} |
797 |
|
} |
798 |
|
|
799 |
|
/** |
800 |
< |
* Returns <tt>true</tt> if this deque contains the specified element. |
801 |
< |
* More formally, returns <tt>true</tt> if and only if this deque contains |
802 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
800 |
> |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
801 |
> |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
802 |
> |
* deque. |
803 |
> |
* |
804 |
> |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
805 |
> |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
806 |
> |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
807 |
> |
* the reporting of additional characteristic values. |
808 |
> |
* |
809 |
> |
* @return a {@code Spliterator} over the elements in this deque |
810 |
> |
* @since 1.8 |
811 |
> |
*/ |
812 |
> |
public Spliterator<E> spliterator() { |
813 |
> |
return new DeqSpliterator(); |
814 |
> |
} |
815 |
> |
|
816 |
> |
final class DeqSpliterator implements Spliterator<E> { |
817 |
> |
private int fence; // -1 until first use |
818 |
> |
private int cursor; // current index, modified on traverse/split |
819 |
> |
|
820 |
> |
/** Constructs late-binding spliterator over all elements. */ |
821 |
> |
DeqSpliterator() { |
822 |
> |
this.fence = -1; |
823 |
> |
} |
824 |
> |
|
825 |
> |
/** Constructs spliterator over the given range. */ |
826 |
> |
DeqSpliterator(int origin, int fence) { |
827 |
> |
// assert 0 <= origin && origin < elements.length; |
828 |
> |
// assert 0 <= fence && fence < elements.length; |
829 |
> |
this.cursor = origin; |
830 |
> |
this.fence = fence; |
831 |
> |
} |
832 |
> |
|
833 |
> |
/** Ensures late-binding initialization; then returns fence. */ |
834 |
> |
private int getFence() { // force initialization |
835 |
> |
int t; |
836 |
> |
if ((t = fence) < 0) { |
837 |
> |
t = fence = tail; |
838 |
> |
cursor = head; |
839 |
> |
} |
840 |
> |
return t; |
841 |
> |
} |
842 |
> |
|
843 |
> |
public DeqSpliterator trySplit() { |
844 |
> |
final Object[] es = elements; |
845 |
> |
final int i, n; |
846 |
> |
return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0) |
847 |
> |
? null |
848 |
> |
: new DeqSpliterator(i, cursor = inc(i, n, es.length)); |
849 |
> |
} |
850 |
> |
|
851 |
> |
public void forEachRemaining(Consumer<? super E> action) { |
852 |
> |
if (action == null) |
853 |
> |
throw new NullPointerException(); |
854 |
> |
final int end = getFence(), cursor = this.cursor; |
855 |
> |
final Object[] es = elements; |
856 |
> |
if (cursor != end) { |
857 |
> |
this.cursor = end; |
858 |
> |
// null check at both ends of range is sufficient |
859 |
> |
if (es[cursor] == null || es[dec(end, es.length)] == null) |
860 |
> |
throw new ConcurrentModificationException(); |
861 |
> |
for (int i = cursor, to = (i <= end) ? end : es.length; |
862 |
> |
; i = 0, to = end) { |
863 |
> |
for (; i < to; i++) |
864 |
> |
action.accept(elementAt(es, i)); |
865 |
> |
if (to == end) break; |
866 |
> |
} |
867 |
> |
} |
868 |
> |
} |
869 |
> |
|
870 |
> |
public boolean tryAdvance(Consumer<? super E> action) { |
871 |
> |
Objects.requireNonNull(action); |
872 |
> |
final Object[] es = elements; |
873 |
> |
if (fence < 0) { fence = tail; cursor = head; } // late-binding |
874 |
> |
final int i; |
875 |
> |
if ((i = cursor) == fence) |
876 |
> |
return false; |
877 |
> |
E e = nonNullElementAt(es, i); |
878 |
> |
cursor = inc(i, es.length); |
879 |
> |
action.accept(e); |
880 |
> |
return true; |
881 |
> |
} |
882 |
> |
|
883 |
> |
public long estimateSize() { |
884 |
> |
return sub(getFence(), cursor, elements.length); |
885 |
> |
} |
886 |
> |
|
887 |
> |
public int characteristics() { |
888 |
> |
return Spliterator.NONNULL |
889 |
> |
| Spliterator.ORDERED |
890 |
> |
| Spliterator.SIZED |
891 |
> |
| Spliterator.SUBSIZED; |
892 |
> |
} |
893 |
> |
} |
894 |
> |
|
895 |
> |
/** |
896 |
> |
* @throws NullPointerException {@inheritDoc} |
897 |
> |
*/ |
898 |
> |
public void forEach(Consumer<? super E> action) { |
899 |
> |
Objects.requireNonNull(action); |
900 |
> |
final Object[] es = elements; |
901 |
> |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
902 |
> |
; i = 0, to = end) { |
903 |
> |
for (; i < to; i++) |
904 |
> |
action.accept(elementAt(es, i)); |
905 |
> |
if (to == end) { |
906 |
> |
if (end != tail) throw new ConcurrentModificationException(); |
907 |
> |
break; |
908 |
> |
} |
909 |
> |
} |
910 |
> |
// checkInvariants(); |
911 |
> |
} |
912 |
> |
|
913 |
> |
/** |
914 |
> |
* Replaces each element of this deque with the result of applying the |
915 |
> |
* operator to that element, as specified by {@link List#replaceAll}. |
916 |
> |
* |
917 |
> |
* @param operator the operator to apply to each element |
918 |
> |
* @since TBD |
919 |
> |
*/ |
920 |
> |
/* public */ void replaceAll(UnaryOperator<E> operator) { |
921 |
> |
Objects.requireNonNull(operator); |
922 |
> |
final Object[] es = elements; |
923 |
> |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
924 |
> |
; i = 0, to = end) { |
925 |
> |
for (; i < to; i++) |
926 |
> |
es[i] = operator.apply(elementAt(es, i)); |
927 |
> |
if (to == end) { |
928 |
> |
if (end != tail) throw new ConcurrentModificationException(); |
929 |
> |
break; |
930 |
> |
} |
931 |
> |
} |
932 |
> |
// checkInvariants(); |
933 |
> |
} |
934 |
> |
|
935 |
> |
/** |
936 |
> |
* @throws NullPointerException {@inheritDoc} |
937 |
> |
*/ |
938 |
> |
public boolean removeIf(Predicate<? super E> filter) { |
939 |
> |
Objects.requireNonNull(filter); |
940 |
> |
return bulkRemove(filter); |
941 |
> |
} |
942 |
> |
|
943 |
> |
/** |
944 |
> |
* @throws NullPointerException {@inheritDoc} |
945 |
> |
*/ |
946 |
> |
public boolean removeAll(Collection<?> c) { |
947 |
> |
Objects.requireNonNull(c); |
948 |
> |
return bulkRemove(e -> c.contains(e)); |
949 |
> |
} |
950 |
> |
|
951 |
> |
/** |
952 |
> |
* @throws NullPointerException {@inheritDoc} |
953 |
> |
*/ |
954 |
> |
public boolean retainAll(Collection<?> c) { |
955 |
> |
Objects.requireNonNull(c); |
956 |
> |
return bulkRemove(e -> !c.contains(e)); |
957 |
> |
} |
958 |
> |
|
959 |
> |
/** Implementation of bulk remove methods. */ |
960 |
> |
private boolean bulkRemove(Predicate<? super E> filter) { |
961 |
> |
// checkInvariants(); |
962 |
> |
final Object[] es = elements; |
963 |
> |
// Optimize for initial run of survivors |
964 |
> |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
965 |
> |
; i = 0, to = end) { |
966 |
> |
for (; i < to; i++) |
967 |
> |
if (filter.test(elementAt(es, i))) |
968 |
> |
return bulkRemoveModified(filter, i); |
969 |
> |
if (to == end) { |
970 |
> |
if (end != tail) throw new ConcurrentModificationException(); |
971 |
> |
break; |
972 |
> |
} |
973 |
> |
} |
974 |
> |
return false; |
975 |
> |
} |
976 |
> |
|
977 |
> |
// A tiny bit set implementation |
978 |
> |
|
979 |
> |
private static long[] nBits(int n) { |
980 |
> |
return new long[((n - 1) >> 6) + 1]; |
981 |
> |
} |
982 |
> |
private static void setBit(long[] bits, int i) { |
983 |
> |
bits[i >> 6] |= 1L << i; |
984 |
> |
} |
985 |
> |
private static boolean isClear(long[] bits, int i) { |
986 |
> |
return (bits[i >> 6] & (1L << i)) == 0; |
987 |
> |
} |
988 |
> |
|
989 |
> |
/** |
990 |
> |
* Helper for bulkRemove, in case of at least one deletion. |
991 |
> |
* Tolerate predicates that reentrantly access the collection for |
992 |
> |
* read (but writers still get CME), so traverse once to find |
993 |
> |
* elements to delete, a second pass to physically expunge. |
994 |
> |
* |
995 |
> |
* @param beg valid index of first element to be deleted |
996 |
> |
*/ |
997 |
> |
private boolean bulkRemoveModified( |
998 |
> |
Predicate<? super E> filter, final int beg) { |
999 |
> |
final Object[] es = elements; |
1000 |
> |
final int capacity = es.length; |
1001 |
> |
final int end = tail; |
1002 |
> |
final long[] deathRow = nBits(sub(end, beg, capacity)); |
1003 |
> |
deathRow[0] = 1L; // set bit 0 |
1004 |
> |
for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
1005 |
> |
; i = 0, to = end, k -= capacity) { |
1006 |
> |
for (; i < to; i++) |
1007 |
> |
if (filter.test(elementAt(es, i))) |
1008 |
> |
setBit(deathRow, i - k); |
1009 |
> |
if (to == end) break; |
1010 |
> |
} |
1011 |
> |
// a two-finger traversal, with hare i reading, tortoise w writing |
1012 |
> |
int w = beg; |
1013 |
> |
for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
1014 |
> |
; w = 0) { // w rejoins i on second leg |
1015 |
> |
// In this loop, i and w are on the same leg, with i > w |
1016 |
> |
for (; i < to; i++) |
1017 |
> |
if (isClear(deathRow, i - k)) |
1018 |
> |
es[w++] = es[i]; |
1019 |
> |
if (to == end) break; |
1020 |
> |
// In this loop, w is on the first leg, i on the second |
1021 |
> |
for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++) |
1022 |
> |
if (isClear(deathRow, i - k)) |
1023 |
> |
es[w++] = es[i]; |
1024 |
> |
if (i >= to) { |
1025 |
> |
if (w == capacity) w = 0; // "corner" case |
1026 |
> |
break; |
1027 |
> |
} |
1028 |
> |
} |
1029 |
> |
if (end != tail) throw new ConcurrentModificationException(); |
1030 |
> |
circularClear(es, tail = w, end); |
1031 |
> |
// checkInvariants(); |
1032 |
> |
return true; |
1033 |
> |
} |
1034 |
> |
|
1035 |
> |
/** |
1036 |
> |
* Returns {@code true} if this deque contains the specified element. |
1037 |
> |
* More formally, returns {@code true} if and only if this deque contains |
1038 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
1039 |
|
* |
1040 |
|
* @param o object to be checked for containment in this deque |
1041 |
< |
* @return <tt>true</tt> if this deque contains the specified element |
1041 |
> |
* @return {@code true} if this deque contains the specified element |
1042 |
|
*/ |
1043 |
|
public boolean contains(Object o) { |
1044 |
< |
if (o == null) |
1045 |
< |
return false; |
1046 |
< |
int mask = elements.length - 1; |
1047 |
< |
int i = head; |
1048 |
< |
E x; |
1049 |
< |
while ( (x = elements[i]) != null) { |
1050 |
< |
if (o.equals(x)) |
1051 |
< |
return true; |
1052 |
< |
i = (i + 1) & mask; |
1044 |
> |
if (o != null) { |
1045 |
> |
final Object[] es = elements; |
1046 |
> |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
1047 |
> |
; i = 0, to = end) { |
1048 |
> |
for (; i < to; i++) |
1049 |
> |
if (o.equals(es[i])) |
1050 |
> |
return true; |
1051 |
> |
if (to == end) break; |
1052 |
> |
} |
1053 |
|
} |
1054 |
|
return false; |
1055 |
|
} |
1057 |
|
/** |
1058 |
|
* Removes a single instance of the specified element from this deque. |
1059 |
|
* If the deque does not contain the element, it is unchanged. |
1060 |
< |
* More formally, removes the first element <tt>e</tt> such that |
1061 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
1062 |
< |
* Returns true if this deque contained the specified element (or |
1063 |
< |
* equivalently, if this deque changed as a result of the call). |
1060 |
> |
* More formally, removes the first element {@code e} such that |
1061 |
> |
* {@code o.equals(e)} (if such an element exists). |
1062 |
> |
* Returns {@code true} if this deque contained the specified element |
1063 |
> |
* (or equivalently, if this deque changed as a result of the call). |
1064 |
|
* |
1065 |
< |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
1065 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
1066 |
|
* |
1067 |
|
* @param o element to be removed from this deque, if present |
1068 |
< |
* @return <tt>true</tt> if this deque contained the specified element |
1068 |
> |
* @return {@code true} if this deque contained the specified element |
1069 |
|
*/ |
1070 |
|
public boolean remove(Object o) { |
1071 |
|
return removeFirstOccurrence(o); |
1076 |
|
* The deque will be empty after this call returns. |
1077 |
|
*/ |
1078 |
|
public void clear() { |
1079 |
< |
int h = head; |
1080 |
< |
int t = tail; |
1081 |
< |
if (h != t) { // clear all cells |
1082 |
< |
head = tail = 0; |
1083 |
< |
int i = h; |
1084 |
< |
int mask = elements.length - 1; |
1085 |
< |
do { |
1086 |
< |
elements[i] = null; |
1087 |
< |
i = (i + 1) & mask; |
1088 |
< |
} while (i != t); |
1079 |
> |
circularClear(elements, head, tail); |
1080 |
> |
head = tail = 0; |
1081 |
> |
// checkInvariants(); |
1082 |
> |
} |
1083 |
> |
|
1084 |
> |
/** |
1085 |
> |
* Nulls out slots starting at array index i, upto index end. |
1086 |
> |
* Condition i == end means "empty" - nothing to do. |
1087 |
> |
*/ |
1088 |
> |
private static void circularClear(Object[] es, int i, int end) { |
1089 |
> |
// assert 0 <= i && i < es.length; |
1090 |
> |
// assert 0 <= end && end < es.length; |
1091 |
> |
for (int to = (i <= end) ? end : es.length; |
1092 |
> |
; i = 0, to = end) { |
1093 |
> |
for (; i < to; i++) es[i] = null; |
1094 |
> |
if (to == end) break; |
1095 |
|
} |
1096 |
|
} |
1097 |
|
|
1102 |
|
* <p>The returned array will be "safe" in that no references to it are |
1103 |
|
* maintained by this deque. (In other words, this method must allocate |
1104 |
|
* a new array). The caller is thus free to modify the returned array. |
1105 |
< |
* |
1105 |
> |
* |
1106 |
|
* <p>This method acts as bridge between array-based and collection-based |
1107 |
|
* APIs. |
1108 |
|
* |
1109 |
|
* @return an array containing all of the elements in this deque |
1110 |
|
*/ |
1111 |
|
public Object[] toArray() { |
1112 |
< |
return copyElements(new Object[size()]); |
1112 |
> |
return toArray(Object[].class); |
1113 |
> |
} |
1114 |
> |
|
1115 |
> |
private <T> T[] toArray(Class<T[]> klazz) { |
1116 |
> |
final Object[] es = elements; |
1117 |
> |
final T[] a; |
1118 |
> |
final int head = this.head, tail = this.tail, end; |
1119 |
> |
if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) { |
1120 |
> |
// Uses null extension feature of copyOfRange |
1121 |
> |
a = Arrays.copyOfRange(es, head, end, klazz); |
1122 |
> |
} else { |
1123 |
> |
// integer overflow! |
1124 |
> |
a = Arrays.copyOfRange(es, 0, end - head, klazz); |
1125 |
> |
System.arraycopy(es, head, a, 0, es.length - head); |
1126 |
> |
} |
1127 |
> |
if (end != tail) |
1128 |
> |
System.arraycopy(es, 0, a, es.length - head, tail); |
1129 |
> |
return a; |
1130 |
|
} |
1131 |
|
|
1132 |
|
/** |
1140 |
|
* <p>If this deque fits in the specified array with room to spare |
1141 |
|
* (i.e., the array has more elements than this deque), the element in |
1142 |
|
* the array immediately following the end of the deque is set to |
1143 |
< |
* <tt>null</tt>. |
1143 |
> |
* {@code null}. |
1144 |
|
* |
1145 |
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
1146 |
|
* array-based and collection-based APIs. Further, this method allows |
1147 |
|
* precise control over the runtime type of the output array, and may, |
1148 |
|
* under certain circumstances, be used to save allocation costs. |
1149 |
|
* |
1150 |
< |
* <p>Suppose <tt>x</tt> is a deque known to contain only strings. |
1150 |
> |
* <p>Suppose {@code x} is a deque known to contain only strings. |
1151 |
|
* The following code can be used to dump the deque into a newly |
1152 |
< |
* allocated array of <tt>String</tt>: |
1152 |
> |
* allocated array of {@code String}: |
1153 |
|
* |
1154 |
< |
* <pre> |
686 |
< |
* String[] y = x.toArray(new String[0]);</pre> |
1154 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
1155 |
|
* |
1156 |
< |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
1157 |
< |
* <tt>toArray()</tt>. |
1156 |
> |
* Note that {@code toArray(new Object[0])} is identical in function to |
1157 |
> |
* {@code toArray()}. |
1158 |
|
* |
1159 |
|
* @param a the array into which the elements of the deque are to |
1160 |
|
* be stored, if it is big enough; otherwise, a new array of the |
1165 |
|
* this deque |
1166 |
|
* @throws NullPointerException if the specified array is null |
1167 |
|
*/ |
1168 |
+ |
@SuppressWarnings("unchecked") |
1169 |
|
public <T> T[] toArray(T[] a) { |
1170 |
< |
int size = size(); |
1171 |
< |
if (a.length < size) |
1172 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
1173 |
< |
a.getClass().getComponentType(), size); |
1174 |
< |
copyElements(a); |
1175 |
< |
if (a.length > size) |
1170 |
> |
final int size; |
1171 |
> |
if ((size = size()) > a.length) |
1172 |
> |
return toArray((Class<T[]>) a.getClass()); |
1173 |
> |
final Object[] es = elements; |
1174 |
> |
for (int i = head, j = 0, len = Math.min(size, es.length - i); |
1175 |
> |
; i = 0, len = tail) { |
1176 |
> |
System.arraycopy(es, i, a, j, len); |
1177 |
> |
if ((j += len) == size) break; |
1178 |
> |
} |
1179 |
> |
if (size < a.length) |
1180 |
|
a[size] = null; |
1181 |
|
return a; |
1182 |
|
} |
1190 |
|
*/ |
1191 |
|
public ArrayDeque<E> clone() { |
1192 |
|
try { |
1193 |
+ |
@SuppressWarnings("unchecked") |
1194 |
|
ArrayDeque<E> result = (ArrayDeque<E>) super.clone(); |
1195 |
< |
// These two lines are currently faster than cloning the array: |
722 |
< |
result.elements = (E[]) new Object[elements.length]; |
723 |
< |
System.arraycopy(elements, 0, result.elements, 0, elements.length); |
1195 |
> |
result.elements = Arrays.copyOf(elements, elements.length); |
1196 |
|
return result; |
725 |
– |
|
1197 |
|
} catch (CloneNotSupportedException e) { |
1198 |
|
throw new AssertionError(); |
1199 |
|
} |
1200 |
|
} |
1201 |
|
|
731 |
– |
/** |
732 |
– |
* Appease the serialization gods. |
733 |
– |
*/ |
1202 |
|
private static final long serialVersionUID = 2340985798034038923L; |
1203 |
|
|
1204 |
|
/** |
1205 |
< |
* Serialize this deque. |
1205 |
> |
* Saves this deque to a stream (that is, serializes it). |
1206 |
|
* |
1207 |
< |
* @serialData The current size (<tt>int</tt>) of the deque, |
1207 |
> |
* @param s the stream |
1208 |
> |
* @throws java.io.IOException if an I/O error occurs |
1209 |
> |
* @serialData The current size ({@code int}) of the deque, |
1210 |
|
* followed by all of its elements (each an object reference) in |
1211 |
|
* first-to-last order. |
1212 |
|
*/ |
1213 |
< |
private void writeObject(ObjectOutputStream s) throws IOException { |
1213 |
> |
private void writeObject(java.io.ObjectOutputStream s) |
1214 |
> |
throws java.io.IOException { |
1215 |
|
s.defaultWriteObject(); |
1216 |
|
|
1217 |
|
// Write out size |
1218 |
< |
int size = size(); |
748 |
< |
s.writeInt(size); |
1218 |
> |
s.writeInt(size()); |
1219 |
|
|
1220 |
|
// Write out elements in order. |
1221 |
< |
int i = head; |
1222 |
< |
int mask = elements.length - 1; |
1223 |
< |
for (int j = 0; j < size; j++) { |
1224 |
< |
s.writeObject(elements[i]); |
1225 |
< |
i = (i + 1) & mask; |
1221 |
> |
final Object[] es = elements; |
1222 |
> |
for (int i = head, end = tail, to = (i <= end) ? end : es.length; |
1223 |
> |
; i = 0, to = end) { |
1224 |
> |
for (; i < to; i++) |
1225 |
> |
s.writeObject(es[i]); |
1226 |
> |
if (to == end) break; |
1227 |
|
} |
1228 |
|
} |
1229 |
|
|
1230 |
|
/** |
1231 |
< |
* Deserialize this deque. |
1231 |
> |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1232 |
> |
* @param s the stream |
1233 |
> |
* @throws ClassNotFoundException if the class of a serialized object |
1234 |
> |
* could not be found |
1235 |
> |
* @throws java.io.IOException if an I/O error occurs |
1236 |
|
*/ |
1237 |
< |
private void readObject(ObjectInputStream s) |
1238 |
< |
throws IOException, ClassNotFoundException { |
1237 |
> |
private void readObject(java.io.ObjectInputStream s) |
1238 |
> |
throws java.io.IOException, ClassNotFoundException { |
1239 |
|
s.defaultReadObject(); |
1240 |
|
|
1241 |
|
// Read in size and allocate array |
1242 |
|
int size = s.readInt(); |
1243 |
< |
allocateElements(size); |
1244 |
< |
head = 0; |
1245 |
< |
tail = size; |
1243 |
> |
SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size + 1); |
1244 |
> |
elements = new Object[size + 1]; |
1245 |
> |
this.tail = size; |
1246 |
|
|
1247 |
|
// Read in all elements in the proper order. |
1248 |
|
for (int i = 0; i < size; i++) |
1249 |
< |
elements[i] = (E)s.readObject(); |
1249 |
> |
elements[i] = s.readObject(); |
1250 |
> |
} |
1251 |
|
|
1252 |
+ |
/** debugging */ |
1253 |
+ |
void checkInvariants() { |
1254 |
+ |
// Use head and tail fields with empty slot at tail strategy. |
1255 |
+ |
// head == tail disambiguates to "empty". |
1256 |
+ |
try { |
1257 |
+ |
int capacity = elements.length; |
1258 |
+ |
// assert 0 <= head && head < capacity; |
1259 |
+ |
// assert 0 <= tail && tail < capacity; |
1260 |
+ |
// assert capacity > 0; |
1261 |
+ |
// assert size() < capacity; |
1262 |
+ |
// assert head == tail || elements[head] != null; |
1263 |
+ |
// assert elements[tail] == null; |
1264 |
+ |
// assert head == tail || elements[dec(tail, capacity)] != null; |
1265 |
+ |
} catch (Throwable t) { |
1266 |
+ |
System.err.printf("head=%d tail=%d capacity=%d%n", |
1267 |
+ |
head, tail, elements.length); |
1268 |
+ |
System.err.printf("elements=%s%n", |
1269 |
+ |
Arrays.toString(elements)); |
1270 |
+ |
throw t; |
1271 |
+ |
} |
1272 |
|
} |
1273 |
+ |
|
1274 |
|
} |