--- jsr166/src/main/java/util/PriorityQueue.java 2011/12/02 14:37:32 1.76
+++ jsr166/src/main/java/util/PriorityQueue.java 2016/11/30 18:12:52 1.114
@@ -1,12 +1,12 @@
/*
- * Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
+ * 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. 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
@@ -25,6 +25,8 @@
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
@@ -52,18 +54,19 @@ 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
@@ -75,9 +78,8 @@ package java.util;
*
* @since 1.5
* @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 {
@@ -93,12 +95,12 @@ 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 +112,7 @@ 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 +137,19 @@ 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.
*
@@ -244,8 +259,8 @@ public class PriorityQueue extends Ab
a = Arrays.copyOf(a, a.length, Object[].class);
int len = a.length;
if (len == 1 || this.comparator != null)
- for (int i = 0; i < len; i++)
- if (a[i] == null)
+ for (Object e : a)
+ if (e == null)
throw new NullPointerException();
this.queue = a;
this.size = a.length;
@@ -323,14 +338,12 @@ 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;
}
+ @SuppressWarnings("unchecked")
public E peek() {
return (size == 0) ? null : (E) queue[0];
}
@@ -391,7 +404,7 @@ 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;
}
/**
@@ -429,14 +442,14 @@ 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}:
*
- *
{@code 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
@@ -447,7 +460,9 @@ public class PriorityQueue extends Ab
* 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());
@@ -472,7 +487,7 @@ 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,
@@ -492,13 +507,13 @@ 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
@@ -512,6 +527,7 @@ public class PriorityQueue extends Ab
(forgetMeNot != null && !forgetMeNot.isEmpty());
}
+ @SuppressWarnings("unchecked")
public E next() {
if (expectedModCount != modCount)
throw new ConcurrentModificationException();
@@ -536,7 +552,7 @@ public class PriorityQueue extends Ab
cursor--;
else {
if (forgetMeNot == null)
- forgetMeNot = new ArrayDeque();
+ forgetMeNot = new ArrayDeque<>();
forgetMeNot.add(moved);
}
} else if (lastRetElt != null) {
@@ -564,6 +580,7 @@ public class PriorityQueue extends Ab
size = 0;
}
+ @SuppressWarnings("unchecked")
public E poll() {
if (size == 0)
return null;
@@ -589,7 +606,8 @@ 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) {
+ @SuppressWarnings("unchecked")
+ E removeAt(int i) {
// assert i >= 0 && i < size;
modCount++;
int s = --size;
@@ -627,6 +645,7 @@ 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) {
@@ -640,6 +659,7 @@ 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;
@@ -667,6 +687,7 @@ 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
@@ -685,6 +706,7 @@ public class PriorityQueue extends Ab
queue[k] = key;
}
+ @SuppressWarnings("unchecked")
private void siftDownUsingComparator(int k, E x) {
int half = size >>> 1;
while (k < half) {
@@ -705,10 +727,18 @@ 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.
+ * This classic algorithm due to Floyd (1964) is known to be O(size).
*/
+ @SuppressWarnings("unchecked")
private void heapify() {
- for (int i = (size >>> 1) - 1; i >= 0; i--)
- siftDown(i, (E) queue[i]);
+ final Object[] es = queue;
+ final int half = (size >>> 1) - 1;
+ if (comparator == null)
+ for (int i = half; i >= 0; i--)
+ siftDownComparable(i, (E) es[i]);
+ else
+ for (int i = half; i >= 0; i--)
+ siftDownUsingComparator(i, (E) es[i]);
}
/**
@@ -725,13 +755,13 @@ 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
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
@@ -751,6 +781,9 @@ 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
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
@@ -770,4 +803,109 @@ public class PriorityQueue extends Ab
// 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 {
+ /*
+ * This is very similar to ArrayList Spliterator, except for
+ * extra null checks.
+ */
+ 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);
+ }
+
+ @SuppressWarnings("unchecked")
+ public void forEachRemaining(Consumer super E> action) {
+ int i, hi, mc; // hoist accesses and checks from loop
+ final Object[] a;
+ if (action == null)
+ throw new NullPointerException();
+ if ((a = queue) != null) {
+ if ((hi = fence) < 0) {
+ mc = modCount;
+ hi = 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 (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)queue[lo];
+ if (e == null)
+ throw new ConcurrentModificationException();
+ action.accept(e);
+ if (modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+ return true;
+ }
+ return false;
+ }
+
+ public long estimateSize() {
+ return getFence() - index;
+ }
+
+ public int characteristics() {
+ return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
+ }
+ }
}