| /* |
| * Copyright (c) 2003, 2013, 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.function.Consumer; |
| |
| /** |
| * 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}). |
| * |
| * <p>The <em>head</em> of this queue is the <em>least</em> 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. |
| * |
| * <p>A priority queue is unbounded, but has an internal |
| * <i>capacity</i> 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. |
| * |
| * <p>This class and its iterator implement all of the |
| * <em>optional</em> methods of the {@link Collection} and {@link |
| * Iterator} interfaces. The Iterator provided in method {@link |
| * #iterator()} is <em>not</em> 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())}. |
| * |
| * <p><strong>Note that this implementation is not synchronized.</strong> |
| * 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. |
| * |
| * <p>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}). |
| * |
| * <p>This class is a member of the |
| * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @since 1.5 |
| * @author Josh Bloch, Doug Lea |
| * @param <E> the type of elements held in this queue |
| */ |
| public class PriorityQueue<E> extends AbstractQueue<E> |
| implements java.io.Serializable { |
| |
| private static final long serialVersionUID = -7720805057305804111L; |
| |
| private static final int DEFAULT_INITIAL_CAPACITY = 11; |
| |
| /** |
| * 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. |
| */ |
| int size; |
| |
| /** |
| * The comparator, or null if priority queue uses elements' |
| * natural ordering. |
| */ |
| private final Comparator<? super E> comparator; |
| |
| /** |
| * The number of times this priority queue has been |
| * <i>structurally modified</i>. See AbstractList for gory details. |
| */ |
| transient int modCount; // 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); |
| } |
| |
| /** |
| * 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); |
| } |
| |
| /** |
| * Creates a {@code PriorityQueue} with the default initial capacity and |
| * whose elements are ordered according to the specified comparator. |
| * |
| * @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. |
| * @since 1.8 |
| */ |
| public PriorityQueue(Comparator<? super E> comparator) { |
| this(DEFAULT_INITIAL_CAPACITY, comparator); |
| } |
| |
| /** |
| * 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<? super E> 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; |
| } |
| |
| /** |
| * 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<? extends E> c) { |
| if (c instanceof SortedSet<?>) { |
| SortedSet<? extends E> ss = (SortedSet<? extends E>) c; |
| this.comparator = (Comparator<? super E>) ss.comparator(); |
| initElementsFromCollection(ss); |
| } |
| else if (c instanceof PriorityQueue<?>) { |
| PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c; |
| this.comparator = (Comparator<? super E>) pq.comparator(); |
| initFromPriorityQueue(pq); |
| } |
| else { |
| this.comparator = null; |
| initFromCollection(c); |
| } |
| } |
| |
| /** |
| * 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<? extends E> c) { |
| this.comparator = (Comparator<? super E>) c.comparator(); |
| initFromPriorityQueue(c); |
| } |
| |
| /** |
| * 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<? extends E> c) { |
| this.comparator = (Comparator<? super E>) c.comparator(); |
| initElementsFromCollection(c); |
| } |
| |
| private void initFromPriorityQueue(PriorityQueue<? extends E> c) { |
| if (c.getClass() == PriorityQueue.class) { |
| this.queue = c.toArray(); |
| this.size = c.size(); |
| } else { |
| initFromCollection(c); |
| } |
| } |
| |
| private void initElementsFromCollection(Collection<? extends E> 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 (Object e : a) |
| if (e == 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<? extends E> 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 (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; |
| } |
| |
| /** |
| * 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; |
| } |
| |
| /** |
| * 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. |
| * |
| * <p>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. |
| * |
| * <p>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 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. |
| * |
| * <p>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}. |
| * |
| * <p>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. |
| * |
| * <p>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}: |
| * |
| * <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
| * |
| * 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> 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<E> iterator() { |
| return new Itr(); |
| } |
| |
| private final class Itr implements Iterator<E> { |
| /** |
| * 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<E> 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; |
| } |
| |
| /** |
| * 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") |
| 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<? super E> key = (Comparable<? super E>) 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<? super E> key = (Comparable<? super E>)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<? super E>) 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<? super E> 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(); |
| } |
| |
| /** |
| * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
| * and <em>fail-fast</em> {@link Spliterator} over the elements in this |
| * queue. |
| * |
| * <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
| * {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}. |
| * Overriding implementations should document the reporting of additional |
| * characteristic values. |
| * |
| * @return a {@code Spliterator} over the elements in this queue |
| * @since 1.8 |
| */ |
| public final Spliterator<E> spliterator() { |
| return new PriorityQueueSpliterator<>(this, 0, -1, 0); |
| } |
| |
| static final class PriorityQueueSpliterator<E> implements Spliterator<E> { |
| /* |
| * This is very similar to ArrayList Spliterator, except for |
| * extra null checks. |
| */ |
| private final PriorityQueue<E> 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<E> 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 PriorityQueueSpliterator<E> 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<? super E> action) { |
| int i, hi, mc; // hoist accesses and checks from loop |
| PriorityQueue<E> 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<? super E> action) { |
| if (action == null) |
| throw new NullPointerException(); |
| 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; |
| } |
| } |
| } |
