| /* | |
| * Copyright (c) 2003, 2025, 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; | |
| import java.util.function.Predicate; | |
| import jdk.internal.access.SharedSecrets; | |
| import jdk.internal.util.ArraysSupport; | |
| /** | |
| * 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()} and the Spliterator provided in method {@link #spliterator()} | |
| * are <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}/java.base/java/util/package-summary.html#CollectionsFramework"> | |
| * Java Collections Framework</a>. | |
| * | |
| * @since 1.5 | |
| * @author Josh Bloch, Doug Lea | |
| * @param <E> the type of elements held in this queue | |
| */ | |
| @SuppressWarnings("unchecked") | |
| public class PriorityQueue<E> extends AbstractQueue<E> | |
| implements java.io.Serializable { | |
| @java.io.Serial | |
| 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 | |
| /** | |
| * @serial The number of elements in the priority queue. | |
| */ | |
| int size; | |
| /** | |
| * @serial The comparator, or null if priority queue uses elements' | |
| * natural ordering. | |
| */ | |
| @SuppressWarnings("serial") // Conditionally serializable | |
| 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 | |
| */ | |
| 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 | |
| */ | |
| 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 | |
| */ | |
| public PriorityQueue(SortedSet<? extends E> c) { | |
| this.comparator = (Comparator<? super E>) c.comparator(); | |
| initElementsFromCollection(c); | |
| } | |
| /** Ensures that queue[0] exists, helping peek() and poll(). */ | |
| private static Object[] ensureNonEmpty(Object[] es) { | |
| return (es.length > 0) ? es : new Object[1]; | |
| } | |
| private void initFromPriorityQueue(PriorityQueue<? extends E> c) { | |
| if (c.getClass() == PriorityQueue.class) { | |
| this.queue = ensureNonEmpty(c.toArray()); | |
| this.size = c.size(); | |
| } else { | |
| initFromCollection(c); | |
| } | |
| } | |
| private void initElementsFromCollection(Collection<? extends E> c) { | |
| Object[] es = c.toArray(); | |
| int len = es.length; | |
| if (c.getClass() != ArrayList.class) | |
| es = Arrays.copyOf(es, len, Object[].class); | |
| if (len == 1 || this.comparator != null) | |
| for (Object e : es) | |
| if (e == null) | |
| throw new NullPointerException(); | |
| this.queue = ensureNonEmpty(es); | |
| this.size = len; | |
| } | |
| /** | |
| * Initializes queue array with elements from the given Collection. | |
| * | |
| * @param c the collection | |
| */ | |
| private void initFromCollection(Collection<? extends E> c) { | |
| initElementsFromCollection(c); | |
| heapify(); | |
| } | |
| /** | |
| * 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 = ArraysSupport.newLength(oldCapacity, | |
| minCapacity - oldCapacity, /* minimum growth */ | |
| oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1 | |
| /* preferred growth */); | |
| queue = Arrays.copyOf(queue, newCapacity); | |
| } | |
| /** | |
| * 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); | |
| siftUp(i, e); | |
| size = i + 1; | |
| return true; | |
| } | |
| public E peek() { | |
| return (E) queue[0]; | |
| } | |
| private int indexOf(Object o) { | |
| if (o != null) { | |
| final Object[] es = queue; | |
| for (int i = 0, n = size; i < n; i++) | |
| if (o.equals(es[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; | |
| } | |
| } | |
| /** | |
| * Identity-based version for use in Itr.remove. | |
| * | |
| * @param o element to be removed from this queue, if present | |
| */ | |
| void removeEq(Object o) { | |
| final Object[] es = queue; | |
| for (int i = 0, n = size; i < n; i++) { | |
| if (o == es[i]) { | |
| removeAt(i); | |
| break; | |
| } | |
| } | |
| } | |
| /** | |
| * 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 | |
| */ | |
| 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; | |
| Itr() {} // prevent access constructor creation | |
| public boolean hasNext() { | |
| return cursor < size || | |
| (forgetMeNot != null && !forgetMeNot.isEmpty()); | |
| } | |
| 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++; | |
| final Object[] es = queue; | |
| for (int i = 0, n = size; i < n; i++) | |
| es[i] = null; | |
| size = 0; | |
| } | |
| public E poll() { | |
| final Object[] es; | |
| final E result; | |
| if ((result = (E) ((es = queue)[0])) != null) { | |
| modCount++; | |
| final int n; | |
| final E x = (E) es[(n = --size)]; | |
| es[n] = null; | |
| if (n > 0) { | |
| final Comparator<? super E> cmp; | |
| if ((cmp = comparator) == null) | |
| siftDownComparable(0, x, es, n); | |
| else | |
| siftDownUsingComparator(0, x, es, n, cmp); | |
| } | |
| } | |
| 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. | |
| */ | |
| E removeAt(int i) { | |
| // assert i >= 0 && i < size; | |
| final Object[] es = queue; | |
| modCount++; | |
| int s = --size; | |
| if (s == i) // removed last element | |
| es[i] = null; | |
| else { | |
| E moved = (E) es[s]; | |
| es[s] = null; | |
| siftDown(i, moved); | |
| if (es[i] == moved) { | |
| siftUp(i, moved); | |
| if (es[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, queue, comparator); | |
| else | |
| siftUpComparable(k, x, queue); | |
| } | |
| private static <T> void siftUpComparable(int k, T x, Object[] es) { | |
| Comparable<? super T> key = (Comparable<? super T>) x; | |
| while (k > 0) { | |
| int parent = (k - 1) >>> 1; | |
| Object e = es[parent]; | |
| if (key.compareTo((T) e) >= 0) | |
| break; | |
| es[k] = e; | |
| k = parent; | |
| } | |
| es[k] = key; | |
| } | |
| private static <T> void siftUpUsingComparator( | |
| int k, T x, Object[] es, Comparator<? super T> cmp) { | |
| while (k > 0) { | |
| int parent = (k - 1) >>> 1; | |
| Object e = es[parent]; | |
| if (cmp.compare(x, (T) e) >= 0) | |
| break; | |
| es[k] = e; | |
| k = parent; | |
| } | |
| es[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, queue, size, comparator); | |
| else | |
| siftDownComparable(k, x, queue, size); | |
| } | |
| private static <T> void siftDownComparable(int k, T x, Object[] es, int n) { | |
| // assert n > 0; | |
| Comparable<? super T> key = (Comparable<? super T>)x; | |
| int half = n >>> 1; // loop while a non-leaf | |
| while (k < half) { | |
| int child = (k << 1) + 1; // assume left child is least | |
| Object c = es[child]; | |
| int right = child + 1; | |
| if (right < n && | |
| ((Comparable<? super T>) c).compareTo((T) es[right]) > 0) | |
| c = es[child = right]; | |
| if (key.compareTo((T) c) <= 0) | |
| break; | |
| es[k] = c; | |
| k = child; | |
| } | |
| es[k] = key; | |
| } | |
| private static <T> void siftDownUsingComparator( | |
| int k, T x, Object[] es, int n, Comparator<? super T> cmp) { | |
| // assert n > 0; | |
| int half = n >>> 1; | |
| while (k < half) { | |
| int child = (k << 1) + 1; | |
| Object c = es[child]; | |
| int right = child + 1; | |
| if (right < n && cmp.compare((T) c, (T) es[right]) > 0) | |
| c = es[child = right]; | |
| if (cmp.compare(x, (T) c) <= 0) | |
| break; | |
| es[k] = c; | |
| k = child; | |
| } | |
| es[k] = x; | |
| } | |
| /** | |
| * Establishes the heap invariant (described above) in the entire tree, | |
| * assuming nothing about the order of the elements prior to the call. | |
| * This classic algorithm due to Floyd (1964) is known to be O(size). | |
| */ | |
| private void heapify() { | |
| final Object[] es = queue; | |
| int n = size, i = (n >>> 1) - 1; | |
| final Comparator<? super E> cmp; | |
| if ((cmp = comparator) == null) | |
| for (; i >= 0; i--) | |
| siftDownComparable(i, (E) es[i], es, n); | |
| else | |
| for (; i >= 0; i--) | |
| siftDownUsingComparator(i, (E) es[i], es, n, cmp); | |
| } | |
| /** | |
| * 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). | |
| * | |
| * @param s the stream | |
| * @throws java.io.IOException if an I/O error occurs | |
| * @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. | |
| */ | |
| @java.io.Serial | |
| 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". | |
| final Object[] es = queue; | |
| for (int i = 0, n = size; i < n; i++) | |
| s.writeObject(es[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 | |
| */ | |
| @java.io.Serial | |
| 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(); | |
| SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size); | |
| final Object[] es = queue = new Object[Math.max(size, 1)]; | |
| // Read in all elements. | |
| for (int i = 0, n = size; i < n; i++) | |
| es[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. The spliterator does not traverse elements in any particular order | |
| * (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported). | |
| * | |
| * <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(0, -1, 0); | |
| } | |
| final class PriorityQueueSpliterator implements Spliterator<E> { | |
| 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(int origin, int fence, int expectedModCount) { | |
| 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 = modCount; | |
| hi = fence = size; | |
| } | |
| return hi; | |
| } | |
| public PriorityQueueSpliterator trySplit() { | |
| int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; | |
| return (lo >= mid) ? null : | |
| new PriorityQueueSpliterator(lo, index = mid, expectedModCount); | |
| } | |
| public void forEachRemaining(Consumer<? super E> action) { | |
| if (action == null) | |
| throw new NullPointerException(); | |
| if (fence < 0) { fence = size; expectedModCount = modCount; } | |
| final Object[] es = queue; | |
| int i, hi; E e; | |
| for (i = index, index = hi = fence; i < hi; i++) { | |
| if ((e = (E) es[i]) == null) | |
| break; // must be CME | |
| action.accept(e); | |
| } | |
| if (modCount != expectedModCount) | |
| throw new ConcurrentModificationException(); | |
| } | |
| public boolean tryAdvance(Consumer<? super E> action) { | |
| if (action == null) | |
| throw new NullPointerException(); | |
| if (fence < 0) { fence = size; expectedModCount = modCount; } | |
| int i; | |
| if ((i = index) < fence) { | |
| index = i + 1; | |
| E e; | |
| if ((e = (E) queue[i]) == null | |
| || modCount != expectedModCount) | |
| throw new ConcurrentModificationException(); | |
| action.accept(e); | |
| return true; | |
| } | |
| return false; | |
| } | |
| public long estimateSize() { | |
| return getFence() - index; | |
| } | |
| public int characteristics() { | |
| return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL; | |
| } | |
| } | |
| /** | |
| * @throws NullPointerException {@inheritDoc} | |
| */ | |
| public boolean removeIf(Predicate<? super E> filter) { | |
| Objects.requireNonNull(filter); | |
| return bulkRemove(filter); | |
| } | |
| /** | |
| * @throws NullPointerException {@inheritDoc} | |
| */ | |
| public boolean removeAll(Collection<?> c) { | |
| Objects.requireNonNull(c); | |
| return bulkRemove(e -> c.contains(e)); | |
| } | |
| /** | |
| * @throws NullPointerException {@inheritDoc} | |
| */ | |
| public boolean retainAll(Collection<?> c) { | |
| Objects.requireNonNull(c); | |
| return bulkRemove(e -> !c.contains(e)); | |
| } | |
| // A tiny bit set implementation | |
| private static long[] nBits(int n) { | |
| return new long[((n - 1) >> 6) + 1]; | |
| } | |
| private static void setBit(long[] bits, int i) { | |
| bits[i >> 6] |= 1L << i; | |
| } | |
| private static boolean isClear(long[] bits, int i) { | |
| return (bits[i >> 6] & (1L << i)) == 0; | |
| } | |
| /** Implementation of bulk remove methods. */ | |
| private boolean bulkRemove(Predicate<? super E> filter) { | |
| final int expectedModCount = ++modCount; | |
| final Object[] es = queue; | |
| final int end = size; | |
| int i; | |
| // Optimize for initial run of survivors | |
| for (i = 0; i < end && !filter.test((E) es[i]); i++) | |
| ; | |
| if (i >= end) { | |
| if (modCount != expectedModCount) | |
| throw new ConcurrentModificationException(); | |
| return false; | |
| } | |
| // Tolerate predicates that reentrantly access the collection for | |
| // read (but writers still get CME), so traverse once to find | |
| // elements to delete, a second pass to physically expunge. | |
| final int beg = i; | |
| final long[] deathRow = nBits(end - beg); | |
| deathRow[0] = 1L; // set bit 0 | |
| for (i = beg + 1; i < end; i++) | |
| if (filter.test((E) es[i])) | |
| setBit(deathRow, i - beg); | |
| if (modCount != expectedModCount) | |
| throw new ConcurrentModificationException(); | |
| int w = beg; | |
| for (i = beg; i < end; i++) | |
| if (isClear(deathRow, i - beg)) | |
| es[w++] = es[i]; | |
| for (i = size = w; i < end; i++) | |
| es[i] = null; | |
| heapify(); | |
| return true; | |
| } | |
| /** | |
| * @throws NullPointerException {@inheritDoc} | |
| */ | |
| public void forEach(Consumer<? super E> action) { | |
| Objects.requireNonNull(action); | |
| final int expectedModCount = modCount; | |
| final Object[] es = queue; | |
| for (int i = 0, n = size; i < n; i++) | |
| action.accept((E) es[i]); | |
| if (expectedModCount != modCount) | |
| throw new ConcurrentModificationException(); | |
| } | |
| } |