--- jsr166/src/main/java/util/PriorityQueue.java 2005/11/28 02:44:06 1.57
+++ jsr166/src/main/java/util/PriorityQueue.java 2015/09/20 16:20:21 1.107
@@ -1,28 +1,47 @@
/*
- * %W% %E%
+ * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
- * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+ * 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.*; // for javadoc (till 6280605 is fixed)
+
+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
- * null elements. A priority queue relying on natural
- * ordering also does not permit insertion of non-comparable objects
- * (doing so may result in ClassCastException).
+ * 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 poll,
- * remove, peek, and element access the
+ * 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
@@ -37,28 +56,28 @@ import java.util.*; // for javadoc (till
* 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 Arrays.sort(pq.toArray()).
+ * traversal, consider using {@code Arrays.sort(pq.toArray())}.
*
- *
Note that this implementation is not synchronized.
- * Multiple threads should not access a PriorityQueue
- * instance concurrently if any of the threads modifies the list
- * structurally. Instead, use the thread-safe {@link
+ *
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 insertion methods (offer, poll,
- * remove() and add) methods; linear time for the
- * remove(Object) and contains(Object) methods; and
- * constant time for the retrieval methods (peek,
- * element, and size).
+ *
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
- * @version 1.8, 08/27/05
- * @author Josh Bloch
- * @param the type of elements held in this collection
+ * @author Josh Bloch, Doug Lea
+ * @param the type of elements held in this queue
*/
public class PriorityQueue extends AbstractQueue
implements java.io.Serializable {
@@ -75,12 +94,12 @@ 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'
@@ -92,10 +111,10 @@ 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 PriorityQueue with the default initial
+ * Creates a {@code PriorityQueue} with the default initial
* capacity (11) that orders its elements according to their
* {@linkplain Comparable natural ordering}.
*/
@@ -104,27 +123,40 @@ public class PriorityQueue extends Ab
}
/**
- * Creates a PriorityQueue with the specified initial
+ * 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 initialCapacity is less
- * than 1
+ * @throws IllegalArgumentException if {@code initialCapacity} is less
+ * than 1
*/
public PriorityQueue(int initialCapacity) {
this(initialCapacity, null);
}
/**
- * Creates a PriorityQueue with the specified initial capacity
+ * 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 null, the natural
- * ordering of the elements will be used.
- * @throws IllegalArgumentException if initialCapacity is
+ * @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,
@@ -138,12 +170,12 @@ public class PriorityQueue extends Ab
}
/**
- * Creates a PriorityQueue containing the elements in the
- * specified collection. If the specified collection is an
- * instance of a {@link java.util.SortedSet} or is another
- * PriorityQueue, the priority queue will be ordered
- * according to the same ordering. Otherwise, this priority queue
- * will be ordered according to the natural ordering of its elements.
+ * 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
@@ -153,92 +185,133 @@ public class PriorityQueue extends Ab
* @throws NullPointerException if the specified collection or any
* of its elements are null
*/
+ @SuppressWarnings("unchecked")
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);
}
}
/**
- * Creates a PriorityQueue containing the elements in the
+ * 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 c cannot be
- * compared to one another according to c's
+ * @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) {
- comparator = (Comparator super E>)c.comparator();
- initFromCollection(c);
+ this.comparator = (Comparator super E>) c.comparator();
+ initFromPriorityQueue(c);
}
/**
- * Creates a PriorityQueue containing the elements in the
- * specified sorted set. This priority queue will be ordered
+ * 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.
+ * 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) {
- comparator = (Comparator super E>)c.comparator();
- initFromCollection(c);
+ this.comparator = (Comparator super E>) c.comparator();
+ initElementsFromCollection(c);
}
- /**
- * Initialize queue array with elements from the given Collection.
- * @param c the collection
- */
- private void initFromCollection(Collection extends E> 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);
- queue = a;
- size = a.length;
+ 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) {
- if (minCapacity < 0) // overflow
- throw new OutOfMemoryError();
- int oldCapacity = queue.length;
+ int oldCapacity = queue.length;
// Double size if small; else grow by 50%
- int newCapacity = ((oldCapacity < 64)?
- ((oldCapacity + 1) * 2):
- ((oldCapacity * 3) / 2));
- if (newCapacity < minCapacity)
- newCapacity = minCapacity;
+ 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 true (as specified by {@link Collection#add})
+ * @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
@@ -251,7 +324,7 @@ public class PriorityQueue extends Ab
/**
* Inserts the specified element into this priority queue.
*
- * @return true (as specified by {@link Queue#offer})
+ * @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
@@ -272,14 +345,13 @@ public class PriorityQueue extends Ab
return true;
}
+ @SuppressWarnings("unchecked")
public E peek() {
- if (size == 0)
- return null;
- return (E) queue[0];
+ return (size == 0) ? null : (E) queue[0];
}
private int indexOf(Object o) {
- if (o != null) {
+ if (o != null) {
for (int i = 0; i < size; i++)
if (o.equals(queue[i]))
return i;
@@ -289,34 +361,35 @@ public class PriorityQueue extends Ab
/**
* Removes a single instance of the specified element from this queue,
- * if it is present. More formally, removes an element e such
- * that o.equals(e), if this queue contains one or more such
- * elements. Returns true if this queue contained the specified element
- * (or equivalently, if this queue changed as a result of the call).
+ * 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 true if this queue changed as a result of the call
+ * @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;
- }
+ 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
+ * Needed by iterator.remove.
*
* @param o element to be removed from this queue, if present
- * @return true if removed.
+ * @return {@code true} if removed
*/
boolean removeEq(Object o) {
- for (int i = 0; i < size; i++) {
- if (o == queue[i]) {
+ for (int i = 0; i < size; i++) {
+ if (o == queue[i]) {
removeAt(i);
return true;
}
@@ -325,60 +398,77 @@ public class PriorityQueue extends Ab
}
/**
- * Returns true if this queue contains the specified element.
- * More formally, returns true if and only if this queue contains
- * at least one element e such that o.equals(e).
+ * 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 true if this queue contains the specified element
+ * @return {@code true} if this queue contains the specified element
*/
public boolean contains(Object o) {
- return indexOf(o) != -1;
+ return indexOf(o) >= 0;
}
/**
- * Returns an array containing all of the elements in this queue,
+ * 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 list. (In other words, this method must allocate
+ * maintained by this queue. (In other words, this method must allocate
* a new array). The caller is thus free to modify the returned array.
*
- * @return an array containing all of the elements in this queue.
+ *
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 elements are in no particular order. The runtime type of
- * the returned array is that of the specified array. 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.
+ * 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
- * null. (This is useful in determining the length of the
- * queue only if the caller knows that the queue does not contain
- * any null elements.)
+ * {@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 the elements of the queue
+ * @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);
+ System.arraycopy(queue, 0, a, 0, size);
if (a.length > size)
a[size] = null;
return a;
@@ -399,7 +489,7 @@ 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,
@@ -417,19 +507,19 @@ public class PriorityQueue extends Ab
* after we've completed the "normal" iteration.
*
* We expect that most iterations, even those involving removals,
- * will not use need to store elements in this field.
+ * 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
- * List should have. If this expectation is violated, the iterator
+ * Queue should have. If this expectation is violated, the iterator
* has detected concurrent modification.
*/
private int expectedModCount = modCount;
@@ -439,6 +529,7 @@ public class PriorityQueue extends Ab
(forgetMeNot != null && !forgetMeNot.isEmpty());
}
+ @SuppressWarnings("unchecked")
public E next() {
if (expectedModCount != modCount)
throw new ConcurrentModificationException();
@@ -456,8 +547,6 @@ public class PriorityQueue extends Ab
public void remove() {
if (expectedModCount != modCount)
throw new ConcurrentModificationException();
- if (lastRet == -1 && lastRetElt == null)
- throw new IllegalStateException();
if (lastRet != -1) {
E moved = PriorityQueue.this.removeAt(lastRet);
lastRet = -1;
@@ -465,16 +554,17 @@ public class PriorityQueue extends Ab
cursor--;
else {
if (forgetMeNot == null)
- forgetMeNot = new ArrayDeque();
+ forgetMeNot = new ArrayDeque<>();
forgetMeNot.add(moved);
}
- } else {
+ } else if (lastRetElt != null) {
PriorityQueue.this.removeEq(lastRetElt);
lastRetElt = null;
+ } else {
+ throw new IllegalStateException();
}
expectedModCount = modCount;
}
-
}
public int size() {
@@ -492,13 +582,14 @@ public class PriorityQueue extends Ab
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];
+ E result = (E) queue[0];
+ E x = (E) queue[s];
queue[s] = null;
if (s != 0)
siftDown(0, x);
@@ -515,10 +606,11 @@ public class PriorityQueue extends Ab
* 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 traverseing elements.
+ * avoid missing traversing elements.
*/
- private E removeAt(int i) {
- assert i >= 0 && i < size;
+ @SuppressWarnings("unchecked")
+ E removeAt(int i) {
+ // assert i >= 0 && i < size;
modCount++;
int s = --size;
if (s == i) // removed last element
@@ -555,12 +647,13 @@ public class PriorityQueue extends Ab
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)
+ if (key.compareTo((E) e) >= 0)
break;
queue[k] = e;
k = parent;
@@ -568,11 +661,12 @@ public class PriorityQueue extends Ab
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)
+ if (comparator.compare(x, (E) e) >= 0)
break;
queue[k] = e;
k = parent;
@@ -595,6 +689,7 @@ public class PriorityQueue extends Ab
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
@@ -603,9 +698,9 @@ public class PriorityQueue extends Ab
Object c = queue[child];
int right = child + 1;
if (right < size &&
- ((Comparable super E>)c).compareTo((E)queue[right]) > 0)
+ ((Comparable super E>) c).compareTo((E) queue[right]) > 0)
c = queue[child = right];
- if (key.compareTo((E)c) <= 0)
+ if (key.compareTo((E) c) <= 0)
break;
queue[k] = c;
k = child;
@@ -613,6 +708,7 @@ public class PriorityQueue extends Ab
queue[k] = key;
}
+ @SuppressWarnings("unchecked")
private void siftDownUsingComparator(int k, E x) {
int half = size >>> 1;
while (k < half) {
@@ -620,9 +716,9 @@ public class PriorityQueue extends Ab
Object c = queue[child];
int right = child + 1;
if (right < size &&
- comparator.compare((E)c, (E)queue[right]) > 0)
+ comparator.compare((E) c, (E) queue[right]) > 0)
c = queue[child = right];
- if (comparator.compare(x, (E)c) <= 0)
+ if (comparator.compare(x, (E) c) <= 0)
break;
queue[k] = c;
k = child;
@@ -634,64 +730,180 @@ public class PriorityQueue extends Ab
* 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]);
+ siftDown(i, (E) queue[i]);
}
/**
* Returns the comparator used to order the elements in this
- * queue, or null if this queue is sorted according to
+ * 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
- * null if this queue is sorted according to the
- * natural ordering of its elements.
+ * {@code null} if this queue is sorted according to the
+ * natural ordering of its elements
*/
public Comparator super E> comparator() {
return comparator;
}
/**
- * Save the state of the instance to a stream (that
- * is, serialize it).
+ * 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
- * Object) in the proper order.
+ * 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{
+ throws java.io.IOException {
// Write out element count, and any hidden stuff
s.defaultWriteObject();
- // Write out array length
- // For compatibility with 1.5 version, must be at least 2.
- s.writeInt(Math.max(2, queue.length));
+ // 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; iPriorityQueue instance from a stream
- * (that is, deserialize it).
+ * 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 array length and allocate array
- int arrayLength = s.readInt();
- queue = new Object[arrayLength];
-
- // Read in all elements in the proper order.
- for (int i=0; ilate-binding
+ * and fail-fast {@link Spliterator} over the elements in this
+ * queue.
+ *
+ * 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<>(this, 0, -1, 0);
+ }
+
+ static final class PriorityQueueSpliterator implements Spliterator {
+ /*
+ * This is very similar to ArrayList Spliterator, except for
+ * extra null checks.
+ */
+ 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 PriorityQueueSpliterator 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 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;
+ }
+ }
}