--- jsr166/src/main/java/util/PriorityQueue.java 2008/05/18 23:47:56 1.68
+++ jsr166/src/main/java/util/PriorityQueue.java 2019/08/30 18:05:39 1.132
@@ -1,12 +1,12 @@
/*
- * Copyright 2003-2006 Sun Microsystems, Inc. All Rights Reserved.
+ * Copyright (c) 2003, 2019, 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. Sun designates this
+ * published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
- * by Sun in the LICENSE file that accompanied this code.
+ * 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
@@ -18,13 +18,18 @@
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
- * CA 95054 USA or visit www.sun.com if you need additional information or
- * have any questions.
+ * 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;
+// OPENJDK 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
@@ -52,35 +57,37 @@ package java.util;
*
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
+ * #iterator()} and the Spliterator provided in method {@link #spliterator()}
+ * are 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.
+ *
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 enqueing and dequeing methods
+ * 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
- * @version %I%, %G%
* @author Josh Bloch, Doug Lea
- * @param the type of elements held in this collection
+ * @param the type of elements held in this queue
*/
+@SuppressWarnings("unchecked")
public class PriorityQueue extends AbstractQueue
implements java.io.Serializable {
+ // OPENJDK @java.io.Serial
private static final long serialVersionUID = -7720805057305804111L;
private static final int DEFAULT_INITIAL_CAPACITY = 11;
@@ -93,12 +100,12 @@ public class PriorityQueue extends Ab
* heap and each descendant d of n, n <= d. The element with the
* lowest value is in queue[0], assuming the queue is nonempty.
*/
- private transient Object[] queue;
+ transient Object[] queue; // non-private to simplify nested class access
/**
* The number of elements in the priority queue.
*/
- private int size = 0;
+ int size;
/**
* The comparator, or null if priority queue uses elements'
@@ -110,7 +117,7 @@ public class PriorityQueue extends Ab
* The number of times this priority queue has been
* structurally modified. See AbstractList for gory details.
*/
- private transient int modCount = 0;
+ transient int modCount; // non-private to simplify nested class access
/**
* Creates a {@code PriorityQueue} with the default initial
@@ -135,6 +142,19 @@ public class PriorityQueue extends Ab
}
/**
+ * 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.
*
@@ -172,16 +192,19 @@ public class PriorityQueue extends Ab
* of its elements are null
*/
public PriorityQueue(Collection extends E> c) {
- initFromCollection(c);
- if (c instanceof SortedSet)
- comparator = (Comparator super E>)
- ((SortedSet extends E>)c).comparator();
- else if (c instanceof PriorityQueue)
- comparator = (Comparator super E>)
- ((PriorityQueue extends E>)c).comparator();
+ 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 {
- comparator = null;
- heapify();
+ this.comparator = null;
+ initFromCollection(c);
}
}
@@ -200,8 +223,8 @@ public class PriorityQueue extends Ab
* of its elements are null
*/
public PriorityQueue(PriorityQueue extends E> c) {
- comparator = (Comparator super E>)c.comparator();
- initFromCollection(c);
+ this.comparator = (Comparator super E>) c.comparator();
+ initFromPriorityQueue(c);
}
/**
@@ -218,8 +241,36 @@ public class PriorityQueue extends Ab
* of its elements are null
*/
public PriorityQueue(SortedSet extends E> c) {
- comparator = (Comparator super E>)c.comparator();
- initFromCollection(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.toArray incorrectly doesn't return Object[], copy it.
+ if (es.getClass() != Object[].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;
}
/**
@@ -228,12 +279,8 @@ public class PriorityQueue extends Ab
* @param c the collection
*/
private void initFromCollection(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);
- queue = a;
- size = a.length;
+ initElementsFromCollection(c);
+ heapify();
}
/**
@@ -242,17 +289,12 @@ public class PriorityQueue extends Ab
* @param minCapacity the desired minimum capacity
*/
private void grow(int minCapacity) {
- if (minCapacity < 0) // overflow
- throw new OutOfMemoryError();
int oldCapacity = queue.length;
// Double size if small; else grow by 50%
- int newCapacity = ((oldCapacity < 64)?
- ((oldCapacity + 1) * 2):
- ((oldCapacity / 2) * 3));
- if (newCapacity < 0) // overflow
- newCapacity = Integer.MAX_VALUE;
- if (newCapacity < minCapacity)
- newCapacity = minCapacity;
+ int newCapacity = ArraysSupport.newLength(oldCapacity,
+ minCapacity - oldCapacity, /* minimum growth */
+ oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1
+ /* preferred growth */);
queue = Arrays.copyOf(queue, newCapacity);
}
@@ -285,24 +327,20 @@ public class PriorityQueue extends Ab
int i = size;
if (i >= queue.length)
grow(i + 1);
+ siftUp(i, e);
size = i + 1;
- if (i == 0)
- queue[0] = e;
- else
- siftUp(i, e);
return true;
}
public E peek() {
- if (size == 0)
- return null;
return (E) queue[0];
}
private int indexOf(Object o) {
if (o != null) {
- for (int i = 0; i < size; i++)
- if (o.equals(queue[i]))
+ final Object[] es = queue;
+ for (int i = 0, n = size; i < n; i++)
+ if (o.equals(es[i]))
return i;
}
return -1;
@@ -330,20 +368,18 @@ public class PriorityQueue extends Ab
}
/**
- * Version of remove using reference equality, not equals.
- * Needed by iterator.remove.
+ * Identity-based version for use in Itr.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]) {
+ void removeEq(Object o) {
+ final Object[] es = queue;
+ for (int i = 0, n = size; i < n; i++) {
+ if (o == es[i]) {
removeAt(i);
- return true;
+ break;
}
}
- return false;
}
/**
@@ -355,7 +391,7 @@ public class PriorityQueue extends Ab
* @return {@code true} if this queue contains the specified element
*/
public boolean contains(Object o) {
- return indexOf(o) != -1;
+ return indexOf(o) >= 0;
}
/**
@@ -393,15 +429,14 @@ public class PriorityQueue extends Ab
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
- * Suppose x is a queue known to contain only strings.
+ *
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 String:
+ * allocated array of {@code String}:
*
- *
- * String[] y = x.toArray(new String[0]);
+ * {@code String[] y = x.toArray(new String[0]);}
*
- * Note that toArray(new Object[0]) is identical in function to
- * toArray().
+ * 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
@@ -413,6 +448,7 @@ public class PriorityQueue extends Ab
* @throws NullPointerException if the specified array is null
*/
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());
@@ -437,7 +473,7 @@ public class PriorityQueue extends Ab
* Index (into queue array) of element to be returned by
* subsequent call to next.
*/
- private int cursor = 0;
+ private int cursor;
/**
* Index of element returned by most recent call to next,
@@ -457,13 +493,13 @@ public class PriorityQueue extends Ab
* We expect that most iterations, even those involving removals,
* will not need to store elements in this field.
*/
- private ArrayDeque forgetMeNot = null;
+ private ArrayDeque forgetMeNot;
/**
* Element returned by the most recent call to next iff that
* element was drawn from the forgetMeNot list.
*/
- private E lastRetElt = null;
+ private E lastRetElt;
/**
* The modCount value that the iterator believes that the backing
@@ -472,6 +508,8 @@ public class PriorityQueue extends Ab
*/
private int expectedModCount = modCount;
+ Itr() {} // prevent access constructor creation
+
public boolean hasNext() {
return cursor < size ||
(forgetMeNot != null && !forgetMeNot.isEmpty());
@@ -501,7 +539,7 @@ public class PriorityQueue extends Ab
cursor--;
else {
if (forgetMeNot == null)
- forgetMeNot = new ArrayDeque();
+ forgetMeNot = new ArrayDeque<>();
forgetMeNot.add(moved);
}
} else if (lastRetElt != null) {
@@ -524,21 +562,29 @@ public class PriorityQueue extends Ab
*/
public void clear() {
modCount++;
- for (int i = 0; i < size; i++)
- queue[i] = null;
+ final Object[] es = queue;
+ for (int i = 0, n = size; i < n; i++)
+ es[i] = null;
size = 0;
}
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);
+ 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;
}
@@ -554,19 +600,20 @@ public class PriorityQueue extends Ab
* position before i. This fact is used by iterator.remove so as to
* avoid missing traversing elements.
*/
- private E removeAt(int i) {
- assert i >= 0 && i < size;
+ E removeAt(int i) {
+ // assert i >= 0 && i < size;
+ final Object[] es = queue;
modCount++;
int s = --size;
if (s == i) // removed last element
- queue[i] = null;
+ es[i] = null;
else {
- E moved = (E) queue[s];
- queue[s] = null;
+ E moved = (E) es[s];
+ es[s] = null;
siftDown(i, moved);
- if (queue[i] == moved) {
+ if (es[i] == moved) {
siftUp(i, moved);
- if (queue[i] != moved)
+ if (es[i] != moved)
return moved;
}
}
@@ -578,7 +625,7 @@ public class PriorityQueue extends Ab
* 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
+ * 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.)
*
@@ -587,34 +634,35 @@ public class PriorityQueue extends Ab
*/
private void siftUp(int k, E x) {
if (comparator != null)
- siftUpUsingComparator(k, x);
+ siftUpUsingComparator(k, x, queue, comparator);
else
- siftUpComparable(k, x);
+ siftUpComparable(k, x, queue);
}
- private void siftUpComparable(int k, E x) {
- Comparable super E> key = (Comparable super E>) x;
+ private static 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 = queue[parent];
- if (key.compareTo((E) e) >= 0)
+ Object e = es[parent];
+ if (key.compareTo((T) e) >= 0)
break;
- queue[k] = e;
+ es[k] = e;
k = parent;
}
- queue[k] = key;
+ es[k] = key;
}
- private void siftUpUsingComparator(int k, E x) {
+ private static void siftUpUsingComparator(
+ int k, T x, Object[] es, Comparator super T> cmp) {
while (k > 0) {
int parent = (k - 1) >>> 1;
- Object e = queue[parent];
- if (comparator.compare(x, (E) e) >= 0)
+ Object e = es[parent];
+ if (cmp.compare(x, (T) e) >= 0)
break;
- queue[k] = e;
+ es[k] = e;
k = parent;
}
- queue[k] = x;
+ es[k] = x;
}
/**
@@ -627,53 +675,63 @@ public class PriorityQueue extends Ab
*/
private void siftDown(int k, E x) {
if (comparator != null)
- siftDownUsingComparator(k, x);
+ siftDownUsingComparator(k, x, queue, size, comparator);
else
- siftDownComparable(k, x);
+ siftDownComparable(k, x, queue, size);
}
- private void siftDownComparable(int k, E x) {
- Comparable super E> key = (Comparable super E>)x;
- int half = size >>> 1; // loop while a non-leaf
+ private static 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 = queue[child];
+ Object c = es[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)
+ if (right < n &&
+ ((Comparable super T>) c).compareTo((T) es[right]) > 0)
+ c = es[child = right];
+ if (key.compareTo((T) c) <= 0)
break;
- queue[k] = c;
+ es[k] = c;
k = child;
}
- queue[k] = key;
+ es[k] = key;
}
- private void siftDownUsingComparator(int k, E x) {
- int half = size >>> 1;
+ private static 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 = queue[child];
+ Object c = es[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)
+ if (right < n && cmp.compare((T) c, (T) es[right]) > 0)
+ c = es[child = right];
+ if (cmp.compare(x, (T) c) <= 0)
break;
- queue[k] = c;
+ es[k] = c;
k = child;
}
- queue[k] = x;
+ 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() {
- for (int i = (size >>> 1) - 1; i >= 0; i--)
- siftDown(i, (E) queue[i]);
+ 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);
}
/**
@@ -690,16 +748,17 @@ public class PriorityQueue extends Ab
}
/**
- * Saves the state of the instance to a stream (that
- * is, serializes it).
+ * 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.
- * @param s the stream
*/
+ // OPENJDK @java.io.Serial
private void writeObject(java.io.ObjectOutputStream s)
- throws java.io.IOException{
+ throws java.io.IOException {
// Write out element count, and any hidden stuff
s.defaultWriteObject();
@@ -707,8 +766,9 @@ public class PriorityQueue extends Ab
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]);
+ final Object[] es = queue;
+ for (int i = 0, n = size; i < n; i++)
+ s.writeObject(es[i]);
}
/**
@@ -716,7 +776,11 @@ public class PriorityQueue extends Ab
* (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
*/
+ // OPENJDK @java.io.Serial
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in size, and any hidden stuff
@@ -725,14 +789,185 @@ public class PriorityQueue extends Ab
// Read in (and discard) array length
s.readInt();
- queue = new Object[size];
+ jsr166.Platform.checkArray(s, Object[].class, size);
+ final Object[] es = queue = new Object[Math.max(size, 1)];
// Read in all elements.
- for (int i = 0; i < size; i++)
- queue[i] = s.readObject();
+ 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 late-binding
+ * and fail-fast {@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).
+ *
+ * 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 spliterator() {
+ return new PriorityQueueSpliterator(0, -1, 0);
+ }
+
+ final class PriorityQueueSpliterator implements Spliterator {
+ 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();
+ }
}