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Revision 1.57 by jsr166, Mon Nov 28 02:44:06 2005 UTC vs.
Revision 1.67 by jsr166, Sun May 20 07:54:01 2007 UTC

# Line 1 | Line 1
1   /*
2 < * %W% %E%
2 > * Copyright 2003-2006 Sun Microsystems, Inc.  All Rights Reserved.
3 > * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4   *
5 < * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
6 < * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
5 > * This code is free software; you can redistribute it and/or modify it
6 > * under the terms of the GNU General Public License version 2 only, as
7 > * published by the Free Software Foundation.  Sun designates this
8 > * particular file as subject to the "Classpath" exception as provided
9 > * by Sun in the LICENSE file that accompanied this code.
10 > *
11 > * This code is distributed in the hope that it will be useful, but WITHOUT
12 > * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 > * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 > * version 2 for more details (a copy is included in the LICENSE file that
15 > * accompanied this code).
16 > *
17 > * You should have received a copy of the GNU General Public License version
18 > * 2 along with this work; if not, write to the Free Software Foundation,
19 > * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 > *
21 > * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 > * CA 95054 USA or visit www.sun.com if you need additional information or
23 > * have any questions.
24   */
25  
26   package java.util;
9 import java.util.*; // for javadoc (till 6280605 is fixed)
27  
28   /**
29 < * An unbounded priority {@linkplain Queue queue} based on a priority
30 < * heap.  The elements of the priority queue are ordered according to
31 < * their {@linkplain Comparable natural ordering}, or by a {@link
32 < * Comparator} provided at queue construction time, depending on which
33 < * constructor is used.  A priority queue does not permit
34 < * <tt>null</tt> elements.  A priority queue relying on natural
35 < * ordering also does not permit insertion of non-comparable objects
36 < * (doing so may result in <tt>ClassCastException</tt>).
29 > * An unbounded priority {@linkplain Queue queue} based on a priority heap.
30 > * The elements of the priority queue are ordered according to their
31 > * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
32 > * provided at queue construction time, depending on which constructor is
33 > * used.  A priority queue does not permit {@code null} elements.
34 > * A priority queue relying on natural ordering also does not permit
35 > * insertion of non-comparable objects (doing so may result in
36 > * {@code ClassCastException}).
37   *
38   * <p>The <em>head</em> of this queue is the <em>least</em> element
39   * with respect to the specified ordering.  If multiple elements are
40   * tied for least value, the head is one of those elements -- ties are
41 < * broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,
42 < * <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the
41 > * broken arbitrarily.  The queue retrieval operations {@code poll},
42 > * {@code remove}, {@code peek}, and {@code element} access the
43   * element at the head of the queue.
44   *
45   * <p>A priority queue is unbounded, but has an internal
# Line 37 | Line 54 | import java.util.*; // for javadoc (till
54   * Iterator} interfaces.  The Iterator provided in method {@link
55   * #iterator()} is <em>not</em> guaranteed to traverse the elements of
56   * the priority queue in any particular order. If you need ordered
57 < * traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.
57 > * traversal, consider using {@code Arrays.sort(pq.toArray())}.
58   *
59   * <p> <strong>Note that this implementation is not synchronized.</strong>
60 < * Multiple threads should not access a <tt>PriorityQueue</tt>
61 < * instance concurrently if any of the threads modifies the list
62 < * structurally. Instead, use the thread-safe {@link
60 > * Multiple threads should not access a {@code PriorityQueue}
61 > * instance concurrently if any of the threads modifies the queue.
62 > * Instead, use the thread-safe {@link
63   * java.util.concurrent.PriorityBlockingQueue} class.
64   *
65 < * <p>Implementation note: this implementation provides O(log(n)) time
66 < * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
67 < * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
68 < * <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
69 < * constant time for the retrieval methods (<tt>peek</tt>,
70 < * <tt>element</tt>, and <tt>size</tt>).
65 > * <p>Implementation note: this implementation provides
66 > * O(log(n)) time for the enqueing and dequeing methods
67 > * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
68 > * linear time for the {@code remove(Object)} and {@code contains(Object)}
69 > * methods; and constant time for the retrieval methods
70 > * ({@code peek}, {@code element}, and {@code size}).
71   *
72   * <p>This class is a member of the
73 < * <a href="{@docRoot}/../guide/collections/index.html">
73 > * <a href="{@docRoot}/../technotes/guides/collections/index.html">
74   * Java Collections Framework</a>.
75 + *
76   * @since 1.5
77 < * @version 1.8, 08/27/05
78 < * @author Josh Bloch
77 > * @version %I%, %G%
78 > * @author Josh Bloch, Doug Lea
79   * @param <E> the type of elements held in this collection
80   */
81   public class PriorityQueue<E> extends AbstractQueue<E>
# Line 95 | Line 113 | public class PriorityQueue<E> extends Ab
113      private transient int modCount = 0;
114  
115      /**
116 <     * Creates a <tt>PriorityQueue</tt> with the default initial
116 >     * Creates a {@code PriorityQueue} with the default initial
117       * capacity (11) that orders its elements according to their
118       * {@linkplain Comparable natural ordering}.
119       */
# Line 104 | Line 122 | public class PriorityQueue<E> extends Ab
122      }
123  
124      /**
125 <     * Creates a <tt>PriorityQueue</tt> with the specified initial
125 >     * Creates a {@code PriorityQueue} with the specified initial
126       * capacity that orders its elements according to their
127       * {@linkplain Comparable natural ordering}.
128       *
129       * @param initialCapacity the initial capacity for this priority queue
130 <     * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
131 <     * than 1
130 >     * @throws IllegalArgumentException if {@code initialCapacity} is less
131 >     *         than 1
132       */
133      public PriorityQueue(int initialCapacity) {
134          this(initialCapacity, null);
135      }
136  
137      /**
138 <     * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
138 >     * Creates a {@code PriorityQueue} with the specified initial capacity
139       * that orders its elements according to the specified comparator.
140       *
141       * @param  initialCapacity the initial capacity for this priority queue
142 <     * @param  comparator the comparator that will be used to order
143 <     *         this priority queue.  If <tt>null</tt>, the <i>natural
144 <     *         ordering</i> of the elements will be used.
145 <     * @throws IllegalArgumentException if <tt>initialCapacity</tt> is
142 >     * @param  comparator the comparator that will be used to order this
143 >     *         priority queue.  If {@code null}, the {@linkplain Comparable
144 >     *         natural ordering} of the elements will be used.
145 >     * @throws IllegalArgumentException if {@code initialCapacity} is
146       *         less than 1
147       */
148      public PriorityQueue(int initialCapacity,
# Line 138 | Line 156 | public class PriorityQueue<E> extends Ab
156      }
157  
158      /**
159 <     * Creates a <tt>PriorityQueue</tt> containing the elements in the
160 <     * specified collection.   If the specified collection is an
161 <     * instance of a {@link java.util.SortedSet} or is another
162 <     * <tt>PriorityQueue</tt>, the priority queue will be ordered
163 <     * according to the same ordering.  Otherwise, this priority queue
164 <     * will be ordered according to the natural ordering of its elements.
159 >     * Creates a {@code PriorityQueue} containing the elements in the
160 >     * specified collection.  If the specified collection is an instance of
161 >     * a {@link SortedSet} or is another {@code PriorityQueue}, this
162 >     * priority queue will be ordered according to the same ordering.
163 >     * Otherwise, this priority queue will be ordered according to the
164 >     * {@linkplain Comparable natural ordering} of its elements.
165       *
166       * @param  c the collection whose elements are to be placed
167       *         into this priority queue
# Line 168 | Line 186 | public class PriorityQueue<E> extends Ab
186      }
187  
188      /**
189 <     * Creates a <tt>PriorityQueue</tt> containing the elements in the
189 >     * Creates a {@code PriorityQueue} containing the elements in the
190       * specified priority queue.  This priority queue will be
191       * ordered according to the same ordering as the given priority
192       * queue.
193       *
194       * @param  c the priority queue whose elements are to be placed
195       *         into this priority queue
196 <     * @throws ClassCastException if elements of <tt>c</tt> cannot be
197 <     *         compared to one another according to <tt>c</tt>'s
196 >     * @throws ClassCastException if elements of {@code c} cannot be
197 >     *         compared to one another according to {@code c}'s
198       *         ordering
199       * @throws NullPointerException if the specified priority queue or any
200       *         of its elements are null
# Line 187 | Line 205 | public class PriorityQueue<E> extends Ab
205      }
206  
207      /**
208 <     * Creates a <tt>PriorityQueue</tt> containing the elements in the
209 <     * specified sorted set.  This priority queue will be ordered
208 >     * Creates a {@code PriorityQueue} containing the elements in the
209 >     * specified sorted set.   This priority queue will be ordered
210       * according to the same ordering as the given sorted set.
211       *
212       * @param  c the sorted set whose elements are to be placed
213 <     *         into this priority queue.
213 >     *         into this priority queue
214       * @throws ClassCastException if elements of the specified sorted
215       *         set cannot be compared to one another according to the
216       *         sorted set's ordering
# Line 205 | Line 223 | public class PriorityQueue<E> extends Ab
223      }
224  
225      /**
226 <     * Initialize queue array with elements from the given Collection.
226 >     * Initializes queue array with elements from the given Collection.
227 >     *
228       * @param c the collection
229       */
230      private void initFromCollection(Collection<? extends E> c) {
# Line 229 | Line 248 | public class PriorityQueue<E> extends Ab
248          // Double size if small; else grow by 50%
249          int newCapacity = ((oldCapacity < 64)?
250                             ((oldCapacity + 1) * 2):
251 <                           ((oldCapacity * 3) / 2));
251 >                           ((oldCapacity / 2) * 3));
252 >        if (newCapacity < 0) // overflow
253 >            newCapacity = Integer.MAX_VALUE;
254          if (newCapacity < minCapacity)
255              newCapacity = minCapacity;
256          queue = Arrays.copyOf(queue, newCapacity);
# Line 238 | Line 259 | public class PriorityQueue<E> extends Ab
259      /**
260       * Inserts the specified element into this priority queue.
261       *
262 <     * @return <tt>true</tt> (as specified by {@link Collection#add})
262 >     * @return {@code true} (as specified by {@link Collection#add})
263       * @throws ClassCastException if the specified element cannot be
264       *         compared with elements currently in this priority queue
265       *         according to the priority queue's ordering
# Line 251 | Line 272 | public class PriorityQueue<E> extends Ab
272      /**
273       * Inserts the specified element into this priority queue.
274       *
275 <     * @return <tt>true</tt> (as specified by {@link Queue#offer})
275 >     * @return {@code true} (as specified by {@link Queue#offer})
276       * @throws ClassCastException if the specified element cannot be
277       *         compared with elements currently in this priority queue
278       *         according to the priority queue's ordering
# Line 289 | Line 310 | public class PriorityQueue<E> extends Ab
310  
311      /**
312       * Removes a single instance of the specified element from this queue,
313 <     * if it is present.  More formally, removes an element <tt>e</tt> such
314 <     * that <tt>o.equals(e)</tt>, if this queue contains one or more such
315 <     * elements.  Returns true if this queue contained the specified element
316 <     * (or equivalently, if this queue changed as a result of the call).
313 >     * if it is present.  More formally, removes an element {@code e} such
314 >     * that {@code o.equals(e)}, if this queue contains one or more such
315 >     * elements.  Returns {@code true} if and only if this queue contained
316 >     * the specified element (or equivalently, if this queue changed as a
317 >     * result of the call).
318       *
319       * @param o element to be removed from this queue, if present
320 <     * @return <tt>true</tt> if this queue changed as a result of the call
320 >     * @return {@code true} if this queue changed as a result of the call
321       */
322      public boolean remove(Object o) {
323          int i = indexOf(o);
# Line 309 | Line 331 | public class PriorityQueue<E> extends Ab
331  
332      /**
333       * Version of remove using reference equality, not equals.
334 <     * Needed by iterator.remove
334 >     * Needed by iterator.remove.
335       *
336       * @param o element to be removed from this queue, if present
337 <     * @return <tt>true</tt> if removed.
337 >     * @return {@code true} if removed
338       */
339      boolean removeEq(Object o) {
340          for (int i = 0; i < size; i++) {
# Line 325 | Line 347 | public class PriorityQueue<E> extends Ab
347      }
348  
349      /**
350 <     * Returns <tt>true</tt> if this queue contains the specified element.
351 <     * More formally, returns <tt>true</tt> if and only if this queue contains
352 <     * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
350 >     * Returns {@code true} if this queue contains the specified element.
351 >     * More formally, returns {@code true} if and only if this queue contains
352 >     * at least one element {@code e} such that {@code o.equals(e)}.
353       *
354       * @param o object to be checked for containment in this queue
355 <     * @return <tt>true</tt> if this queue contains the specified element
355 >     * @return {@code true} if this queue contains the specified element
356       */
357      public boolean contains(Object o) {
358          return indexOf(o) != -1;
359      }
360  
361      /**
362 <     * Returns an array containing all of the elements in this queue,
362 >     * Returns an array containing all of the elements in this queue.
363       * The elements are in no particular order.
364       *
365       * <p>The returned array will be "safe" in that no references to it are
366 <     * maintained by this list.  (In other words, this method must allocate
366 >     * maintained by this queue.  (In other words, this method must allocate
367       * a new array).  The caller is thus free to modify the returned array.
368       *
369 <     * @return an array containing all of the elements in this queue.
369 >     * <p>This method acts as bridge between array-based and collection-based
370 >     * APIs.
371 >     *
372 >     * @return an array containing all of the elements in this queue
373       */
374      public Object[] toArray() {
375          return Arrays.copyOf(queue, size);
376      }
377  
378      /**
379 <     * Returns an array containing all of the elements in this queue.
380 <     * The elements are in no particular order.  The runtime type of
381 <     * the returned array is that of the specified array.  If the queue
382 <     * fits in the specified array, it is returned therein.
383 <     * Otherwise, a new array is allocated with the runtime type of
384 <     * the specified array and the size of this queue.
379 >     * Returns an array containing all of the elements in this queue; the
380 >     * runtime type of the returned array is that of the specified array.
381 >     * The returned array elements are in no particular order.
382 >     * If the queue fits in the specified array, it is returned therein.
383 >     * Otherwise, a new array is allocated with the runtime type of the
384 >     * specified array and the size of this queue.
385       *
386       * <p>If the queue fits in the specified array with room to spare
387       * (i.e., the array has more elements than the queue), the element in
388       * the array immediately following the end of the collection is set to
389 <     * <tt>null</tt>.  (This is useful in determining the length of the
390 <     * queue <i>only</i> if the caller knows that the queue does not contain
391 <     * any null elements.)
389 >     * {@code null}.
390 >     *
391 >     * <p>Like the {@link #toArray()} method, this method acts as bridge between
392 >     * array-based and collection-based APIs.  Further, this method allows
393 >     * precise control over the runtime type of the output array, and may,
394 >     * under certain circumstances, be used to save allocation costs.
395 >     *
396 >     * <p>Suppose <tt>x</tt> is a queue known to contain only strings.
397 >     * The following code can be used to dump the queue into a newly
398 >     * allocated array of <tt>String</tt>:
399 >     *
400 >     * <pre>
401 >     *     String[] y = x.toArray(new String[0]);</pre>
402 >     *
403 >     * Note that <tt>toArray(new Object[0])</tt> is identical in function to
404 >     * <tt>toArray()</tt>.
405       *
406       * @param a the array into which the elements of the queue are to
407       *          be stored, if it is big enough; otherwise, a new array of the
408       *          same runtime type is allocated for this purpose.
409 <     * @return an array containing the elements of the queue
409 >     * @return an array containing all of the elements in this queue
410       * @throws ArrayStoreException if the runtime type of the specified array
411       *         is not a supertype of the runtime type of every element in
412       *         this queue
# Line 417 | Line 455 | public class PriorityQueue<E> extends Ab
455           * after we've completed the "normal" iteration.
456           *
457           * We expect that most iterations, even those involving removals,
458 <         * will not use need to store elements in this field.
458 >         * will not need to store elements in this field.
459           */
460          private ArrayDeque<E> forgetMeNot = null;
461  
# Line 429 | Line 467 | public class PriorityQueue<E> extends Ab
467  
468          /**
469           * The modCount value that the iterator believes that the backing
470 <         * List should have.  If this expectation is violated, the iterator
470 >         * Queue should have.  If this expectation is violated, the iterator
471           * has detected concurrent modification.
472           */
473          private int expectedModCount = modCount;
# Line 456 | Line 494 | public class PriorityQueue<E> extends Ab
494          public void remove() {
495              if (expectedModCount != modCount)
496                  throw new ConcurrentModificationException();
459            if (lastRet == -1 && lastRetElt == null)
460                throw new IllegalStateException();
497              if (lastRet != -1) {
498                  E moved = PriorityQueue.this.removeAt(lastRet);
499                  lastRet = -1;
# Line 468 | Line 504 | public class PriorityQueue<E> extends Ab
504                          forgetMeNot = new ArrayDeque<E>();
505                      forgetMeNot.add(moved);
506                  }
507 <            } else {
507 >            } else if (lastRetElt != null) {
508                  PriorityQueue.this.removeEq(lastRetElt);
509                  lastRetElt = null;
510 <            }
510 >            } else {
511 >                throw new IllegalStateException();
512 >            }
513              expectedModCount = modCount;
514          }
477
515      }
516  
517      public int size() {
# Line 497 | Line 534 | public class PriorityQueue<E> extends Ab
534              return null;
535          int s = --size;
536          modCount++;
537 <        E result = (E)queue[0];
538 <        E x = (E)queue[s];
537 >        E result = (E) queue[0];
538 >        E x = (E) queue[s];
539          queue[s] = null;
540          if (s != 0)
541              siftDown(0, x);
# Line 515 | Line 552 | public class PriorityQueue<E> extends Ab
552       * i.  Under these circumstances, this method returns the element
553       * that was previously at the end of the list and is now at some
554       * position before i. This fact is used by iterator.remove so as to
555 <     * avoid missing traverseing elements.
555 >     * avoid missing traversing elements.
556       */
557      private E removeAt(int i) {
558          assert i >= 0 && i < size;
# Line 560 | Line 597 | public class PriorityQueue<E> extends Ab
597          while (k > 0) {
598              int parent = (k - 1) >>> 1;
599              Object e = queue[parent];
600 <            if (key.compareTo((E)e) >= 0)
600 >            if (key.compareTo((E) e) >= 0)
601                  break;
602              queue[k] = e;
603              k = parent;
# Line 572 | Line 609 | public class PriorityQueue<E> extends Ab
609          while (k > 0) {
610              int parent = (k - 1) >>> 1;
611              Object e = queue[parent];
612 <            if (comparator.compare(x, (E)e) >= 0)
612 >            if (comparator.compare(x, (E) e) >= 0)
613                  break;
614              queue[k] = e;
615              k = parent;
# Line 603 | Line 640 | public class PriorityQueue<E> extends Ab
640              Object c = queue[child];
641              int right = child + 1;
642              if (right < size &&
643 <                ((Comparable<? super E>)c).compareTo((E)queue[right]) > 0)
643 >                ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
644                  c = queue[child = right];
645 <            if (key.compareTo((E)c) <= 0)
645 >            if (key.compareTo((E) c) <= 0)
646                  break;
647              queue[k] = c;
648              k = child;
# Line 620 | Line 657 | public class PriorityQueue<E> extends Ab
657              Object c = queue[child];
658              int right = child + 1;
659              if (right < size &&
660 <                comparator.compare((E)c, (E)queue[right]) > 0)
660 >                comparator.compare((E) c, (E) queue[right]) > 0)
661                  c = queue[child = right];
662 <            if (comparator.compare(x, (E)c) <= 0)
662 >            if (comparator.compare(x, (E) c) <= 0)
663                  break;
664              queue[k] = c;
665              k = child;
# Line 636 | Line 673 | public class PriorityQueue<E> extends Ab
673       */
674      private void heapify() {
675          for (int i = (size >>> 1) - 1; i >= 0; i--)
676 <            siftDown(i, (E)queue[i]);
676 >            siftDown(i, (E) queue[i]);
677      }
678  
679      /**
680       * Returns the comparator used to order the elements in this
681 <     * queue, or <tt>null</tt> if this queue is sorted according to
681 >     * queue, or {@code null} if this queue is sorted according to
682       * the {@linkplain Comparable natural ordering} of its elements.
683       *
684       * @return the comparator used to order this queue, or
685 <     *         <tt>null</tt> if this queue is sorted according to the
686 <     *         natural ordering of its elements.
685 >     *         {@code null} if this queue is sorted according to the
686 >     *         natural ordering of its elements
687       */
688      public Comparator<? super E> comparator() {
689          return comparator;
690      }
691  
692      /**
693 <     * Save the state of the instance to a stream (that
694 <     * is, serialize it).
693 >     * Saves the state of the instance to a stream (that
694 >     * is, serializes it).
695       *
696       * @serialData The length of the array backing the instance is
697 <     * emitted (int), followed by all of its elements (each an
698 <     * <tt>Object</tt>) in the proper order.
697 >     *             emitted (int), followed by all of its elements
698 >     *             (each an {@code Object}) in the proper order.
699       * @param s the stream
700       */
701      private void writeObject(java.io.ObjectOutputStream s)
# Line 666 | Line 703 | public class PriorityQueue<E> extends Ab
703          // Write out element count, and any hidden stuff
704          s.defaultWriteObject();
705  
706 <        // Write out array length
707 <        // For compatibility with 1.5 version, must be at least 2.
671 <        s.writeInt(Math.max(2, queue.length));
706 >        // Write out array length, for compatibility with 1.5 version
707 >        s.writeInt(Math.max(2, size + 1));
708  
709 <        // Write out all elements in the proper order.
710 <        for (int i=0; i<size; i++)
709 >        // Write out all elements in the "proper order".
710 >        for (int i = 0; i < size; i++)
711              s.writeObject(queue[i]);
712      }
713  
714      /**
715 <     * Reconstitute the <tt>PriorityQueue</tt> instance from a stream
716 <     * (that is, deserialize it).
715 >     * Reconstitutes the {@code PriorityQueue} instance from a stream
716 >     * (that is, deserializes it).
717 >     *
718       * @param s the stream
719       */
720      private void readObject(java.io.ObjectInputStream s)
# Line 685 | Line 722 | public class PriorityQueue<E> extends Ab
722          // Read in size, and any hidden stuff
723          s.defaultReadObject();
724  
725 <        // Read in array length and allocate array
726 <        int arrayLength = s.readInt();
727 <        queue = new Object[arrayLength];
728 <
692 <        // Read in all elements in the proper order.
693 <        for (int i=0; i<size; i++)
694 <            queue[i] = (E) s.readObject();
695 <    }
725 >        // Read in (and discard) array length
726 >        s.readInt();
727 >
728 >        queue = new Object[size];
729  
730 +        // Read in all elements.
731 +        for (int i = 0; i < size; i++)
732 +            queue[i] = s.readObject();
733 +
734 +        // Elements are guaranteed to be in "proper order", but the
735 +        // spec has never explained what that might be.
736 +        heapify();
737 +    }
738   }

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