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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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* Written by Josh Bloch of Google Inc. and released to the public domain, |
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* as explained at http://creativecommons.org/publicdomain/zero/1.0/. |
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*/ |
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package java.util; |
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import java.util.Spliterator; |
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import java.io.Serializable; |
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import java.util.function.Consumer; |
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import java.util.stream.Stream; |
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import java.util.stream.Streams; |
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import java.util.function.Block; |
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/** |
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* Resizable-array implementation of the {@link Deque} interface. Array |
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* when used as a queue. |
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* |
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* <p>Most {@code ArrayDeque} operations run in amortized constant time. |
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* Exceptions include {@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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* 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 {@code iterator} 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 {@code remove} |
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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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* @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, java.io.Serializable |
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implements Deque<E>, Cloneable, Serializable |
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{ |
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/** |
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* The array in which the elements of the deque are stored. |
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} |
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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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* |
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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 an initial capacity |
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* sufficient to hold 16 elements. |
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*/ |
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} |
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} |
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/** |
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* This class is nearly a mirror-image of DeqIterator, using tail |
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* instead of head for initial cursor, and head instead of tail |
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* for fence. |
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*/ |
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private class DescendingIterator implements Iterator<E> { |
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/* |
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* This class is nearly a mirror-image of DeqIterator, using |
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* tail instead of head for initial cursor, and head instead of |
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* tail for fence. |
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*/ |
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private int cursor = tail; |
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private int fence = head; |
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private int lastRet = -1; |
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* Returns {@code true} if this deque contained the specified element |
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* (or equivalently, if this deque changed as a result of the call). |
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* |
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* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
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* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
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* |
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* @param o element to be removed from this deque, if present |
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* @return {@code true} if this deque contained the specified element |
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* @return an array containing all of the elements in this deque |
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*/ |
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public Object[] toArray() { |
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return copyElements(new Object[size()]); |
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final int head = this.head; |
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final int tail = this.tail; |
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boolean wrap = (tail < head); |
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int end = wrap ? tail + elements.length : tail; |
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Object[] a = Arrays.copyOfRange(elements, head, end); |
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if (wrap) |
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System.arraycopy(elements, 0, a, elements.length - head, tail); |
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return a; |
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} |
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/** |
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*/ |
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@SuppressWarnings("unchecked") |
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public <T> T[] toArray(T[] a) { |
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int size = size(); |
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if (a.length < size) |
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a = (T[])java.lang.reflect.Array.newInstance( |
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a.getClass().getComponentType(), size); |
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copyElements(a); |
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if (a.length > size) |
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a[size] = null; |
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final int head = this.head; |
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final int tail = this.tail; |
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boolean wrap = (tail < head); |
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int size = (tail - head) + (wrap ? elements.length : 0); |
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int firstLeg = size - (wrap ? tail : 0); |
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int len = a.length; |
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if (size > len) { |
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a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
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a.getClass()); |
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} else { |
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System.arraycopy(elements, head, a, 0, firstLeg); |
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if (size < len) |
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a[size] = null; |
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} |
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if (wrap) |
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System.arraycopy(elements, 0, a, firstLeg, tail); |
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return a; |
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} |
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elements[i] = s.readObject(); |
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} |
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public Stream<E> stream() { |
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int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED; |
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return Streams.stream |
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(() -> new DeqSpliterator<E>(this, head, tail), flags); |
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} |
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public Stream<E> parallelStream() { |
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int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED; |
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return Streams.parallelStream |
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(() -> new DeqSpliterator<E>(this, head, tail), flags); |
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public Spliterator<E> spliterator() { |
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return new DeqSpliterator<E>(this, -1, -1); |
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} |
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static final class DeqSpliterator<E> implements Spliterator<E> { |
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private final ArrayDeque<E> deq; |
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private final int fence; // initially tail |
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private int index; // current index, modified on traverse/split |
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private int fence; // -1 until first use |
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private int index; // current index, modified on traverse/split |
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/** Create new spliterator covering the given array and range */ |
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/** Creates new spliterator covering the given array and range */ |
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DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) { |
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this.deq = deq; this.index = origin; this.fence = fence; |
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this.deq = deq; |
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this.index = origin; |
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this.fence = fence; |
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} |
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private int getFence() { // force initialization |
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int t; |
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if ((t = fence) < 0) { |
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t = fence = deq.tail; |
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index = deq.head; |
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} |
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return t; |
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} |
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public DeqSpliterator<E> trySplit() { |
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int n = deq.elements.length; |
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int h = index, t = fence; |
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public Spliterator<E> trySplit() { |
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int t = getFence(), h = index, n = deq.elements.length; |
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if (h != t && ((h + 1) & (n - 1)) != t) { |
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if (h > t) |
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t += n; |
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int m = ((h + t) >>> 1) & (n - 1); |
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return new DeqSpliterator<E>(deq, h, index = m); |
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return new DeqSpliterator<>(deq, h, index = m); |
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} |
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return null; |
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} |
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public void forEach(Block<? super E> block) { |
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if (block == null) |
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public void forEach(Consumer<? super E> consumer) { |
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if (consumer == null) |
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throw new NullPointerException(); |
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Object[] a = deq.elements; |
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int m = a.length - 1, f = fence, i = index; |
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int m = a.length - 1, f = getFence(), i = index; |
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index = f; |
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while (i != f) { |
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@SuppressWarnings("unchecked") E e = (E)a[i]; |
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i = (i + 1) & m; |
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if (e == null) |
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throw new ConcurrentModificationException(); |
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block.accept(e); |
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consumer.accept(e); |
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} |
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} |
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public boolean tryAdvance(Block<? super E> block) { |
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if (block == null) |
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public boolean tryAdvance(Consumer<? super E> consumer) { |
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if (consumer == null) |
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throw new NullPointerException(); |
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Object[] a = deq.elements; |
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int m = a.length - 1, i = index; |
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int m = a.length - 1, f = getFence(), i = index; |
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if (i != fence) { |
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@SuppressWarnings("unchecked") E e = (E)a[i]; |
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index = (i + 1) & m; |
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if (e == null) |
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throw new ConcurrentModificationException(); |
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block.accept(e); |
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consumer.accept(e); |
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return true; |
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} |
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return false; |
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} |
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// Other spliterator methods |
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public long estimateSize() { |
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int n = fence - index; |
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int n = getFence() - index; |
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if (n < 0) |
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n += deq.elements.length; |
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return (long)n; |
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return (long) n; |
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} |
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|
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@Override |
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public int characteristics() { |
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return Spliterator.ORDERED | Spliterator.SIZED | |
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Spliterator.NONNULL | Spliterator.SUBSIZED; |
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} |
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public boolean hasExactSize() { return true; } |
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public boolean hasExactSplits() { return true; } |
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} |
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} |
