--- jsr166/src/main/java/util/PriorityQueue.java 2003/05/14 21:30:45 1.1 +++ jsr166/src/main/java/util/PriorityQueue.java 2015/02/17 18:55:39 1.104 @@ -1,64 +1,881 @@ +/* + * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. Oracle designates this + * particular file as subject to the "Classpath" exception as provided + * by Oracle in the LICENSE file that accompanied this code. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + */ + package java.util; -import java.util.*; +import java.util.function.Consumer; /** - * An unbounded (resizable) priority queue based on a priority - * heap.The take operation returns the least element with respect to - * the given ordering. (If more than one element is tied for least - * value, one of them is arbitrarily chosen to be returned -- no - * guarantees are made for ordering across ties.) Ordering follows the - * java.util.Collection conventions: Either the elements must be - * Comparable, or a Comparator must be supplied. Comparison failures - * throw ClassCastExceptions during insertions and extractions. - **/ -public class PriorityQueue extends AbstractCollection implements Queue { - public PriorityQueue(int initialCapacity) {} - public PriorityQueue(int initialCapacity, Comparator comparator) {} + * An unbounded priority {@linkplain Queue queue} based on a priority heap. + * The elements of the priority queue are ordered according to their + * {@linkplain Comparable natural ordering}, or by a {@link Comparator} + * provided at queue construction time, depending on which constructor is + * used. A priority queue does not permit {@code null} elements. + * A priority queue relying on natural ordering also does not permit + * insertion of non-comparable objects (doing so may result in + * {@code ClassCastException}). + * + *

The head of this queue is the least element + * with respect to the specified ordering. If multiple elements are + * tied for least value, the head is one of those elements -- ties are + * broken arbitrarily. The queue retrieval operations {@code poll}, + * {@code remove}, {@code peek}, and {@code element} access the + * element at the head of the queue. + * + *

A priority queue is unbounded, but has an internal + * capacity governing the size of an array used to store the + * elements on the queue. It is always at least as large as the queue + * size. As elements are added to a priority queue, its capacity + * grows automatically. The details of the growth policy are not + * specified. + * + *

This class and its iterator implement all of the + * optional methods of the {@link Collection} and {@link + * Iterator} interfaces. The Iterator provided in method {@link + * #iterator()} is not guaranteed to traverse the elements of + * the priority queue in any particular order. If you need ordered + * traversal, consider using {@code Arrays.sort(pq.toArray())}. + * + *

Note that this implementation is not synchronized. + * Multiple threads should not access a {@code PriorityQueue} + * instance concurrently if any of the threads modifies the queue. + * Instead, use the thread-safe {@link + * java.util.concurrent.PriorityBlockingQueue} class. + * + *

Implementation note: this implementation provides + * O(log(n)) time for the enqueuing and dequeuing methods + * ({@code offer}, {@code poll}, {@code remove()} and {@code add}); + * linear time for the {@code remove(Object)} and {@code contains(Object)} + * methods; and constant time for the retrieval methods + * ({@code peek}, {@code element}, and {@code size}). + * + *

This class is a member of the + * + * Java Collections Framework. + * + * @since 1.5 + * @author Josh Bloch, Doug Lea + * @param the type of elements held in this queue + */ +public class PriorityQueue extends AbstractQueue + implements java.io.Serializable { - public PriorityQueue(int initialCapacity, Collection initialElements) {} + private static final long serialVersionUID = -7720805057305804111L; - public PriorityQueue(int initialCapacity, Comparator comparator, Collection initialElements) {} + private static final int DEFAULT_INITIAL_CAPACITY = 11; - public boolean add(E x) { - return false; + /** + * Priority queue represented as a balanced binary heap: the two + * children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The + * priority queue is ordered by comparator, or by the elements' + * natural ordering, if comparator is null: For each node n in the + * heap and each descendant d of n, n <= d. The element with the + * lowest value is in queue[0], assuming the queue is nonempty. + */ + transient Object[] queue; // non-private to simplify nested class access + + /** + * The number of elements in the priority queue. + */ + private int size; + + /** + * The comparator, or null if priority queue uses elements' + * natural ordering. + */ + private final Comparator comparator; + + /** + * The number of times this priority queue has been + * structurally modified. See AbstractList for gory details. + */ + transient int modCount = 0; // non-private to simplify nested class access + + /** + * Creates a {@code PriorityQueue} with the default initial + * capacity (11) that orders its elements according to their + * {@linkplain Comparable natural ordering}. + */ + public PriorityQueue() { + this(DEFAULT_INITIAL_CAPACITY, null); } - public boolean offer(E x) { - return false; + + /** + * Creates a {@code PriorityQueue} with the specified initial + * capacity that orders its elements according to their + * {@linkplain Comparable natural ordering}. + * + * @param initialCapacity the initial capacity for this priority queue + * @throws IllegalArgumentException if {@code initialCapacity} is less + * than 1 + */ + public PriorityQueue(int initialCapacity) { + this(initialCapacity, null); } - public boolean remove(Object x) { - return false; + + /** + * Creates a {@code PriorityQueue} with the specified initial capacity + * that orders its elements according to the specified comparator. + * + * @param initialCapacity the initial capacity for this priority queue + * @param comparator the comparator that will be used to order this + * priority queue. If {@code null}, the {@linkplain Comparable + * natural ordering} of the elements will be used. + * @throws IllegalArgumentException if {@code initialCapacity} is + * less than 1 + */ + public PriorityQueue(int initialCapacity, + Comparator comparator) { + // Note: This restriction of at least one is not actually needed, + // but continues for 1.5 compatibility + if (initialCapacity < 1) + throw new IllegalArgumentException(); + this.queue = new Object[initialCapacity]; + this.comparator = comparator; } - public E remove() { - return null; + /** + * Creates a {@code PriorityQueue} containing the elements in the + * specified collection. If the specified collection is an instance of + * a {@link SortedSet} or is another {@code PriorityQueue}, this + * priority queue will be ordered according to the same ordering. + * Otherwise, this priority queue will be ordered according to the + * {@linkplain Comparable natural ordering} of its elements. + * + * @param c the collection whose elements are to be placed + * into this priority queue + * @throws ClassCastException if elements of the specified collection + * cannot be compared to one another according to the priority + * queue's ordering + * @throws NullPointerException if the specified collection or any + * of its elements are null + */ + @SuppressWarnings("unchecked") + public PriorityQueue(Collection c) { + if (c instanceof SortedSet) { + SortedSet ss = (SortedSet) c; + this.comparator = (Comparator) ss.comparator(); + initElementsFromCollection(ss); + } + else if (c instanceof PriorityQueue) { + PriorityQueue pq = (PriorityQueue) c; + this.comparator = (Comparator) pq.comparator(); + initFromPriorityQueue(pq); + } + else { + this.comparator = null; + initFromCollection(c); + } } - public Iterator iterator() { - return null; + + /** + * Creates a {@code PriorityQueue} containing the elements in the + * specified priority queue. This priority queue will be + * ordered according to the same ordering as the given priority + * queue. + * + * @param c the priority queue whose elements are to be placed + * into this priority queue + * @throws ClassCastException if elements of {@code c} cannot be + * compared to one another according to {@code c}'s + * ordering + * @throws NullPointerException if the specified priority queue or any + * of its elements are null + */ + @SuppressWarnings("unchecked") + public PriorityQueue(PriorityQueue c) { + this.comparator = (Comparator) c.comparator(); + initFromPriorityQueue(c); } - public E element() { - return null; + /** + * Creates a {@code PriorityQueue} containing the elements in the + * specified sorted set. This priority queue will be ordered + * according to the same ordering as the given sorted set. + * + * @param c the sorted set whose elements are to be placed + * into this priority queue + * @throws ClassCastException if elements of the specified sorted + * set cannot be compared to one another according to the + * sorted set's ordering + * @throws NullPointerException if the specified sorted set or any + * of its elements are null + */ + @SuppressWarnings("unchecked") + public PriorityQueue(SortedSet c) { + this.comparator = (Comparator) c.comparator(); + initElementsFromCollection(c); } - public E poll() { - return null; + + private void initFromPriorityQueue(PriorityQueue c) { + if (c.getClass() == PriorityQueue.class) { + this.queue = c.toArray(); + this.size = c.size(); + } else { + initFromCollection(c); + } + } + + private void initElementsFromCollection(Collection c) { + Object[] a = c.toArray(); + // If c.toArray incorrectly doesn't return Object[], copy it. + if (a.getClass() != Object[].class) + a = Arrays.copyOf(a, a.length, Object[].class); + int len = a.length; + if (len == 1 || this.comparator != null) + for (int i = 0; i < len; i++) + if (a[i] == null) + throw new NullPointerException(); + this.queue = a; + this.size = a.length; } + + /** + * Initializes queue array with elements from the given Collection. + * + * @param c the collection + */ + private void initFromCollection(Collection c) { + initElementsFromCollection(c); + heapify(); + } + + /** + * The maximum size of array to allocate. + * Some VMs reserve some header words in an array. + * Attempts to allocate larger arrays may result in + * OutOfMemoryError: Requested array size exceeds VM limit + */ + private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; + + /** + * Increases the capacity of the array. + * + * @param minCapacity the desired minimum capacity + */ + private void grow(int minCapacity) { + int oldCapacity = queue.length; + // Double size if small; else grow by 50% + int newCapacity = oldCapacity + ((oldCapacity < 64) ? + (oldCapacity + 2) : + (oldCapacity >> 1)); + // overflow-conscious code + if (newCapacity - MAX_ARRAY_SIZE > 0) + newCapacity = hugeCapacity(minCapacity); + queue = Arrays.copyOf(queue, newCapacity); + } + + private static int hugeCapacity(int minCapacity) { + if (minCapacity < 0) // overflow + throw new OutOfMemoryError(); + return (minCapacity > MAX_ARRAY_SIZE) ? + Integer.MAX_VALUE : + MAX_ARRAY_SIZE; + } + + /** + * Inserts the specified element into this priority queue. + * + * @return {@code true} (as specified by {@link Collection#add}) + * @throws ClassCastException if the specified element cannot be + * compared with elements currently in this priority queue + * according to the priority queue's ordering + * @throws NullPointerException if the specified element is null + */ + public boolean add(E e) { + return offer(e); + } + + /** + * Inserts the specified element into this priority queue. + * + * @return {@code true} (as specified by {@link Queue#offer}) + * @throws ClassCastException if the specified element cannot be + * compared with elements currently in this priority queue + * according to the priority queue's ordering + * @throws NullPointerException if the specified element is null + */ + public boolean offer(E e) { + if (e == null) + throw new NullPointerException(); + modCount++; + int i = size; + if (i >= queue.length) + grow(i + 1); + size = i + 1; + if (i == 0) + queue[0] = e; + else + siftUp(i, e); + return true; + } + + @SuppressWarnings("unchecked") public E peek() { - return null; + return (size == 0) ? null : (E) queue[0]; + } + + private int indexOf(Object o) { + if (o != null) { + for (int i = 0; i < size; i++) + if (o.equals(queue[i])) + return i; + } + return -1; } - public boolean isEmpty() { + /** + * Removes a single instance of the specified element from this queue, + * if it is present. More formally, removes an element {@code e} such + * that {@code o.equals(e)}, if this queue contains one or more such + * elements. Returns {@code true} if and only if this queue contained + * the specified element (or equivalently, if this queue changed as a + * result of the call). + * + * @param o element to be removed from this queue, if present + * @return {@code true} if this queue changed as a result of the call + */ + public boolean remove(Object o) { + int i = indexOf(o); + if (i == -1) + return false; + else { + removeAt(i); + return true; + } + } + + /** + * Version of remove using reference equality, not equals. + * Needed by iterator.remove. + * + * @param o element to be removed from this queue, if present + * @return {@code true} if removed + */ + boolean removeEq(Object o) { + for (int i = 0; i < size; i++) { + if (o == queue[i]) { + removeAt(i); + return true; + } + } return false; } - public int size() { - return 0; + + /** + * Returns {@code true} if this queue contains the specified element. + * More formally, returns {@code true} if and only if this queue contains + * at least one element {@code e} such that {@code o.equals(e)}. + * + * @param o object to be checked for containment in this queue + * @return {@code true} if this queue contains the specified element + */ + public boolean contains(Object o) { + return indexOf(o) >= 0; } + + /** + * Returns an array containing all of the elements in this queue. + * The elements are in no particular order. + * + *

The returned array will be "safe" in that no references to it are + * maintained by this queue. (In other words, this method must allocate + * a new array). The caller is thus free to modify the returned array. + * + *

This method acts as bridge between array-based and collection-based + * APIs. + * + * @return an array containing all of the elements in this queue + */ public Object[] toArray() { - return null; + return Arrays.copyOf(queue, size); + } + + /** + * Returns an array containing all of the elements in this queue; the + * runtime type of the returned array is that of the specified array. + * The returned array elements are in no particular order. + * If the queue fits in the specified array, it is returned therein. + * Otherwise, a new array is allocated with the runtime type of the + * specified array and the size of this queue. + * + *

If the queue fits in the specified array with room to spare + * (i.e., the array has more elements than the queue), the element in + * the array immediately following the end of the collection is set to + * {@code null}. + * + *

Like the {@link #toArray()} method, this method acts as bridge between + * array-based and collection-based APIs. Further, this method allows + * precise control over the runtime type of the output array, and may, + * under certain circumstances, be used to save allocation costs. + * + *

Suppose {@code x} is a queue known to contain only strings. + * The following code can be used to dump the queue into a newly + * allocated array of {@code String}: + * + * 

 {@code String[] y = x.toArray(new String[0]);}
+ * + * Note that {@code toArray(new Object[0])} is identical in function to + * {@code toArray()}. + * + * @param a the array into which the elements of the queue are to + * be stored, if it is big enough; otherwise, a new array of the + * same runtime type is allocated for this purpose. + * @return an array containing all of the elements in this queue + * @throws ArrayStoreException if the runtime type of the specified array + * is not a supertype of the runtime type of every element in + * this queue + * @throws NullPointerException if the specified array is null + */ + @SuppressWarnings("unchecked") + public T[] toArray(T[] a) { + final int size = this.size; + if (a.length < size) + // Make a new array of a's runtime type, but my contents: + return (T[]) Arrays.copyOf(queue, size, a.getClass()); + System.arraycopy(queue, 0, a, 0, size); + if (a.length > size) + a[size] = null; + return a; + } + + /** + * Returns an iterator over the elements in this queue. The iterator + * does not return the elements in any particular order. + * + * @return an iterator over the elements in this queue + */ + public Iterator iterator() { + return new Itr(); + } + + private final class Itr implements Iterator { + /** + * Index (into queue array) of element to be returned by + * subsequent call to next. + */ + private int cursor; + + /** + * Index of element returned by most recent call to next, + * unless that element came from the forgetMeNot list. + * Set to -1 if element is deleted by a call to remove. + */ + private int lastRet = -1; + + /** + * A queue of elements that were moved from the unvisited portion of + * the heap into the visited portion as a result of "unlucky" element + * removals during the iteration. (Unlucky element removals are those + * that require a siftup instead of a siftdown.) We must visit all of + * the elements in this list to complete the iteration. We do this + * after we've completed the "normal" iteration. + * + * We expect that most iterations, even those involving removals, + * will not need to store elements in this field. + */ + private ArrayDeque forgetMeNot; + + /** + * Element returned by the most recent call to next iff that + * element was drawn from the forgetMeNot list. + */ + private E lastRetElt; + + /** + * The modCount value that the iterator believes that the backing + * Queue should have. If this expectation is violated, the iterator + * has detected concurrent modification. + */ + private int expectedModCount = modCount; + + public boolean hasNext() { + return cursor < size || + (forgetMeNot != null && !forgetMeNot.isEmpty()); + } + + @SuppressWarnings("unchecked") + public E next() { + if (expectedModCount != modCount) + throw new ConcurrentModificationException(); + if (cursor < size) + return (E) queue[lastRet = cursor++]; + if (forgetMeNot != null) { + lastRet = -1; + lastRetElt = forgetMeNot.poll(); + if (lastRetElt != null) + return lastRetElt; + } + throw new NoSuchElementException(); + } + + public void remove() { + if (expectedModCount != modCount) + throw new ConcurrentModificationException(); + if (lastRet != -1) { + E moved = PriorityQueue.this.removeAt(lastRet); + lastRet = -1; + if (moved == null) + cursor--; + else { + if (forgetMeNot == null) + forgetMeNot = new ArrayDeque<>(); + forgetMeNot.add(moved); + } + } else if (lastRetElt != null) { + PriorityQueue.this.removeEq(lastRetElt); + lastRetElt = null; + } else { + throw new IllegalStateException(); + } + expectedModCount = modCount; + } + } + + public int size() { + return size; + } + + /** + * Removes all of the elements from this priority queue. + * The queue will be empty after this call returns. + */ + public void clear() { + modCount++; + for (int i = 0; i < size; i++) + queue[i] = null; + size = 0; + } + + @SuppressWarnings("unchecked") + public E poll() { + if (size == 0) + return null; + int s = --size; + modCount++; + E result = (E) queue[0]; + E x = (E) queue[s]; + queue[s] = null; + if (s != 0) + siftDown(0, x); + return result; } - public T[] toArray(T[] array) { + /** + * Removes the ith element from queue. + * + * Normally this method leaves the elements at up to i-1, + * inclusive, untouched. Under these circumstances, it returns + * null. Occasionally, in order to maintain the heap invariant, + * it must swap a later element of the list with one earlier than + * i. Under these circumstances, this method returns the element + * that was previously at the end of the list and is now at some + * position before i. This fact is used by iterator.remove so as to + * avoid missing traversing elements. + */ + @SuppressWarnings("unchecked") + private E removeAt(int i) { + // assert i >= 0 && i < size; + modCount++; + int s = --size; + if (s == i) // removed last element + queue[i] = null; + else { + E moved = (E) queue[s]; + queue[s] = null; + siftDown(i, moved); + if (queue[i] == moved) { + siftUp(i, moved); + if (queue[i] != moved) + return moved; + } + } return null; } + /** + * Inserts item x at position k, maintaining heap invariant by + * promoting x up the tree until it is greater than or equal to + * its parent, or is the root. + * + * To simplify and speed up coercions and comparisons. the + * Comparable and Comparator versions are separated into different + * methods that are otherwise identical. (Similarly for siftDown.) + * + * @param k the position to fill + * @param x the item to insert + */ + private void siftUp(int k, E x) { + if (comparator != null) + siftUpUsingComparator(k, x); + else + siftUpComparable(k, x); + } + + @SuppressWarnings("unchecked") + private void siftUpComparable(int k, E x) { + Comparable key = (Comparable) x; + while (k > 0) { + int parent = (k - 1) >>> 1; + Object e = queue[parent]; + if (key.compareTo((E) e) >= 0) + break; + queue[k] = e; + k = parent; + } + queue[k] = key; + } + + @SuppressWarnings("unchecked") + private void siftUpUsingComparator(int k, E x) { + while (k > 0) { + int parent = (k - 1) >>> 1; + Object e = queue[parent]; + if (comparator.compare(x, (E) e) >= 0) + break; + queue[k] = e; + k = parent; + } + queue[k] = x; + } + + /** + * Inserts item x at position k, maintaining heap invariant by + * demoting x down the tree repeatedly until it is less than or + * equal to its children or is a leaf. + * + * @param k the position to fill + * @param x the item to insert + */ + private void siftDown(int k, E x) { + if (comparator != null) + siftDownUsingComparator(k, x); + else + siftDownComparable(k, x); + } + + @SuppressWarnings("unchecked") + private void siftDownComparable(int k, E x) { + Comparable key = (Comparable)x; + int half = size >>> 1; // loop while a non-leaf + while (k < half) { + int child = (k << 1) + 1; // assume left child is least + Object c = queue[child]; + int right = child + 1; + if (right < size && + ((Comparable) c).compareTo((E) queue[right]) > 0) + c = queue[child = right]; + if (key.compareTo((E) c) <= 0) + break; + queue[k] = c; + k = child; + } + queue[k] = key; + } + + @SuppressWarnings("unchecked") + private void siftDownUsingComparator(int k, E x) { + int half = size >>> 1; + while (k < half) { + int child = (k << 1) + 1; + Object c = queue[child]; + int right = child + 1; + if (right < size && + comparator.compare((E) c, (E) queue[right]) > 0) + c = queue[child = right]; + if (comparator.compare(x, (E) c) <= 0) + break; + queue[k] = c; + k = child; + } + queue[k] = x; + } + + /** + * Establishes the heap invariant (described above) in the entire tree, + * assuming nothing about the order of the elements prior to the call. + */ + @SuppressWarnings("unchecked") + private void heapify() { + for (int i = (size >>> 1) - 1; i >= 0; i--) + siftDown(i, (E) queue[i]); + } + + /** + * Returns the comparator used to order the elements in this + * queue, or {@code null} if this queue is sorted according to + * the {@linkplain Comparable natural ordering} of its elements. + * + * @return the comparator used to order this queue, or + * {@code null} if this queue is sorted according to the + * natural ordering of its elements + */ + public Comparator comparator() { + return comparator; + } + + /** + * Saves this queue to a stream (that is, serializes it). + * + * @serialData The length of the array backing the instance is + * emitted (int), followed by all of its elements + * (each an {@code Object}) in the proper order. + * @param s the stream + * @throws java.io.IOException if an I/O error occurs + */ + private void writeObject(java.io.ObjectOutputStream s) + throws java.io.IOException { + // Write out element count, and any hidden stuff + s.defaultWriteObject(); + + // Write out array length, for compatibility with 1.5 version + s.writeInt(Math.max(2, size + 1)); + + // Write out all elements in the "proper order". + for (int i = 0; i < size; i++) + s.writeObject(queue[i]); + } + + /** + * Reconstitutes the {@code PriorityQueue} instance from a stream + * (that is, deserializes it). + * + * @param s the stream + * @throws ClassNotFoundException if the class of a serialized object + * could not be found + * @throws java.io.IOException if an I/O error occurs + */ + private void readObject(java.io.ObjectInputStream s) + throws java.io.IOException, ClassNotFoundException { + // Read in size, and any hidden stuff + s.defaultReadObject(); + + // Read in (and discard) array length + s.readInt(); + + queue = new Object[size]; + + // Read in all elements. + for (int i = 0; i < size; i++) + queue[i] = s.readObject(); + + // Elements are guaranteed to be in "proper order", but the + // spec has never explained what that might be. + heapify(); + } + + public Spliterator spliterator() { + return new PriorityQueueSpliterator(this, 0, -1, 0); + } + + /** + * This is very similar to ArrayList Spliterator, except for extra + * null checks. + */ + static final class PriorityQueueSpliterator implements Spliterator { + private final PriorityQueue pq; + private int index; // current index, modified on advance/split + private int fence; // -1 until first use + private int expectedModCount; // initialized when fence set + + /** Creates new spliterator covering the given range */ + PriorityQueueSpliterator(PriorityQueue pq, int origin, int fence, + int expectedModCount) { + this.pq = pq; + this.index = origin; + this.fence = fence; + this.expectedModCount = expectedModCount; + } + + private int getFence() { // initialize fence to size on first use + int hi; + if ((hi = fence) < 0) { + expectedModCount = pq.modCount; + hi = fence = pq.size; + } + return hi; + } + + public Spliterator trySplit() { + int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; + return (lo >= mid) ? null : + new PriorityQueueSpliterator(pq, lo, index = mid, + expectedModCount); + } + + @SuppressWarnings("unchecked") + public void forEachRemaining(Consumer action) { + int i, hi, mc; // hoist accesses and checks from loop + PriorityQueue q; Object[] a; + if (action == null) + throw new NullPointerException(); + if ((q = pq) != null && (a = q.queue) != null) { + if ((hi = fence) < 0) { + mc = q.modCount; + hi = q.size; + } + else + mc = expectedModCount; + if ((i = index) >= 0 && (index = hi) <= a.length) { + for (E e;; ++i) { + if (i < hi) { + if ((e = (E) a[i]) == null) // must be CME + break; + action.accept(e); + } + else if (q.modCount != mc) + break; + else + return; + } + } + } + throw new ConcurrentModificationException(); + } + + public boolean tryAdvance(Consumer action) { + int hi = getFence(), lo = index; + if (lo >= 0 && lo < hi) { + index = lo + 1; + @SuppressWarnings("unchecked") E e = (E)pq.queue[lo]; + if (e == null) + throw new ConcurrentModificationException(); + action.accept(e); + if (pq.modCount != expectedModCount) + throw new ConcurrentModificationException(); + return true; + } + return false; + } + + public long estimateSize() { + return (long) (getFence() - index); + } + + public int characteristics() { + return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; + } + } }