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1 : dl 1.38 /*
2 :     * %W% %E%
3 :     *
4 :     * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
5 :     * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6 :     */
7 :    
8 :     package java.util;
9 : tim 1.1
10 :     /**
11 : dl 1.41 * An unbounded priority {@linkplain Queue queue} based on a priority
12 :     * heap. This queue orders elements according to an order specified
13 :     * at construction time, which is specified either according to their
14 :     * <i>natural order</i> (see {@link Comparable}), or according to a
15 :     * {@link java.util.Comparator}, depending on which constructor is
16 :     * used. A priority queue does not permit <tt>null</tt> elements.
17 : dl 1.42 * A priority queue relying on natural ordering also does not
18 :     * permit insertion of non-comparable objects (doing so results
19 :     * in <tt>ClassCastException</tt>).
20 : dl 1.40 *
21 : dl 1.41 * <p>The <em>head</em> of this queue is the <em>least</em> element
22 :     * with respect to the specified ordering. If multiple elements are
23 :     * tied for least value, the head is one of those elements -- ties are
24 : dl 1.42 * broken arbitrarily. The queue retrieval operations <tt>poll</tt>,
25 :     * <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the
26 :     * element at the head of the queue.
27 : tim 1.14 *
28 : dl 1.41 * <p>A priority queue is unbounded, but has an internal
29 :     * <i>capacity</i> governing the size of an array used to store the
30 : dl 1.40 * elements on the queue. It is always at least as large as the queue
31 :     * size. As elements are added to a priority queue, its capacity
32 :     * grows automatically. The details of the growth policy are not
33 :     * specified.
34 : tim 1.2 *
35 : dl 1.41 * <p>This class implements all of the <em>optional</em> methods of
36 :     * the {@link Collection} and {@link Iterator} interfaces. The
37 :     * Iterator provided in method {@link #iterator()} is <em>not</em>
38 : dl 1.29 * guaranteed to traverse the elements of the PriorityQueue in any
39 :     * particular order. If you need ordered traversal, consider using
40 :     * <tt>Arrays.sort(pq.toArray())</tt>.
41 :     *
42 :     * <p> <strong>Note that this implementation is not synchronized.</strong>
43 :     * Multiple threads should not access a <tt>PriorityQueue</tt>
44 :     * instance concurrently if any of the threads modifies the list
45 :     * structurally. Instead, use the thread-safe {@link
46 : dholmes 1.34 * java.util.concurrent.PriorityBlockingQueue} class.
47 : dl 1.29 *
48 :     *
49 : dholmes 1.11 * <p>Implementation note: this implementation provides O(log(n)) time
50 :     * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
51 :     * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
52 :     * <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
53 :     * constant time for the retrieval methods (<tt>peek</tt>,
54 :     * <tt>element</tt>, and <tt>size</tt>).
55 : tim 1.2 *
56 :     * <p>This class is a member of the
57 :     * <a href="{@docRoot}/../guide/collections/index.html">
58 :     * Java Collections Framework</a>.
59 : dl 1.7 * @since 1.5
60 : dl 1.38 * @version %I%, %G%
61 : dl 1.7 * @author Josh Bloch
62 : tim 1.2 */
63 :     public class PriorityQueue<E> extends AbstractQueue<E>
64 : dl 1.22 implements Queue<E>, java.io.Serializable {
65 : dholmes 1.11
66 : dl 1.31 private static final long serialVersionUID = -7720805057305804111L;
67 : dl 1.30
68 : tim 1.2 private static final int DEFAULT_INITIAL_CAPACITY = 11;
69 : tim 1.1
70 : tim 1.2 /**
71 :     * Priority queue represented as a balanced binary heap: the two children
72 :     * of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is
73 :     * ordered by comparator, or by the elements' natural ordering, if
74 : brian 1.6 * comparator is null: For each node n in the heap and each descendant d
75 :     * of n, n <= d.
76 : tim 1.2 *
77 : brian 1.6 * The element with the lowest value is in queue[1], assuming the queue is
78 :     * nonempty. (A one-based array is used in preference to the traditional
79 :     * zero-based array to simplify parent and child calculations.)
80 : tim 1.2 *
81 :     * queue.length must be >= 2, even if size == 0.
82 :     */
83 : tim 1.16 private transient Object[] queue;
84 : tim 1.1
85 : tim 1.2 /**
86 :     * The number of elements in the priority queue.
87 :     */
88 :     private int size = 0;
89 : tim 1.1
90 : tim 1.2 /**
91 :     * The comparator, or null if priority queue uses elements'
92 :     * natural ordering.
93 :     */
94 : tim 1.16 private final Comparator<? super E> comparator;
95 : tim 1.2
96 :     /**
97 :     * The number of times this priority queue has been
98 :     * <i>structurally modified</i>. See AbstractList for gory details.
99 :     */
100 : dl 1.5 private transient int modCount = 0;
101 : tim 1.2
102 :     /**
103 : dholmes 1.21 * Creates a <tt>PriorityQueue</tt> with the default initial capacity
104 : dl 1.7 * (11) that orders its elements according to their natural
105 : tim 1.24 * ordering (using <tt>Comparable</tt>).
106 : tim 1.2 */
107 :     public PriorityQueue() {
108 : dholmes 1.11 this(DEFAULT_INITIAL_CAPACITY, null);
109 : tim 1.1 }
110 : tim 1.2
111 :     /**
112 : dholmes 1.21 * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
113 : dl 1.7 * that orders its elements according to their natural ordering
114 : tim 1.24 * (using <tt>Comparable</tt>).
115 : tim 1.2 *
116 :     * @param initialCapacity the initial capacity for this priority queue.
117 : dholmes 1.23 * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
118 :     * than 1
119 : tim 1.2 */
120 :     public PriorityQueue(int initialCapacity) {
121 :     this(initialCapacity, null);
122 : tim 1.1 }
123 : tim 1.2
124 :     /**
125 : dholmes 1.21 * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
126 : tim 1.2 * that orders its elements according to the specified comparator.
127 :     *
128 :     * @param initialCapacity the initial capacity for this priority queue.
129 :     * @param comparator the comparator used to order this priority queue.
130 : dholmes 1.11 * If <tt>null</tt> then the order depends on the elements' natural
131 :     * ordering.
132 : dholmes 1.15 * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
133 :     * than 1
134 : tim 1.2 */
135 : dholmes 1.23 public PriorityQueue(int initialCapacity,
136 :     Comparator<? super E> comparator) {
137 : tim 1.2 if (initialCapacity < 1)
138 : dholmes 1.15 throw new IllegalArgumentException();
139 : tim 1.16 this.queue = new Object[initialCapacity + 1];
140 : tim 1.2 this.comparator = comparator;
141 : tim 1.1 }
142 :    
143 : tim 1.2 /**
144 : dl 1.22 * Common code to initialize underlying queue array across
145 :     * constructors below.
146 :     */
147 :     private void initializeArray(Collection<? extends E> c) {
148 :     int sz = c.size();
149 :     int initialCapacity = (int)Math.min((sz * 110L) / 100,
150 :     Integer.MAX_VALUE - 1);
151 :     if (initialCapacity < 1)
152 :     initialCapacity = 1;
153 :    
154 :     this.queue = new Object[initialCapacity + 1];
155 :     }
156 :    
157 :     /**
158 :     * Initially fill elements of the queue array under the
159 :     * knowledge that it is sorted or is another PQ, in which
160 : dl 1.36 * case we can just place the elements in the order presented.
161 : dl 1.22 */
162 :     private void fillFromSorted(Collection<? extends E> c) {
163 :     for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
164 :     queue[++size] = i.next();
165 :     }
166 :    
167 :     /**
168 : dl 1.36 * Initially fill elements of the queue array that is not to our knowledge
169 :     * sorted, so we must rearrange the elements to guarantee the heap
170 :     * invariant.
171 : dl 1.22 */
172 :     private void fillFromUnsorted(Collection<? extends E> c) {
173 :     for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
174 : dl 1.36 queue[++size] = i.next();
175 :     heapify();
176 : dl 1.22 }
177 :    
178 :     /**
179 :     * Creates a <tt>PriorityQueue</tt> containing the elements in the
180 :     * specified collection. The priority queue has an initial
181 :     * capacity of 110% of the size of the specified collection or 1
182 :     * if the collection is empty. If the specified collection is an
183 : tim 1.25 * instance of a {@link java.util.SortedSet} or is another
184 : dl 1.22 * <tt>PriorityQueue</tt>, the priority queue will be sorted
185 :     * according to the same comparator, or according to its elements'
186 :     * natural order if the collection is sorted according to its
187 :     * elements' natural order. Otherwise, the priority queue is
188 :     * ordered according to its elements' natural order.
189 : tim 1.2 *
190 : dholmes 1.15 * @param c the collection whose elements are to be placed
191 : tim 1.2 * into this priority queue.
192 :     * @throws ClassCastException if elements of the specified collection
193 :     * cannot be compared to one another according to the priority
194 :     * queue's ordering.
195 : dholmes 1.15 * @throws NullPointerException if <tt>c</tt> or any element within it
196 :     * is <tt>null</tt>
197 : tim 1.2 */
198 : tim 1.16 public PriorityQueue(Collection<? extends E> c) {
199 : dl 1.22 initializeArray(c);
200 : dl 1.27 if (c instanceof SortedSet) {
201 : dl 1.28 // @fixme double-cast workaround for compiler
202 :     SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
203 : dl 1.22 comparator = (Comparator<? super E>)s.comparator();
204 :     fillFromSorted(s);
205 : dl 1.27 } else if (c instanceof PriorityQueue) {
206 : dl 1.22 PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
207 :     comparator = (Comparator<? super E>)s.comparator();
208 :     fillFromSorted(s);
209 : tim 1.26 } else {
210 : tim 1.2 comparator = null;
211 : dl 1.22 fillFromUnsorted(c);
212 : tim 1.2 }
213 : dl 1.22 }
214 :    
215 :     /**
216 :     * Creates a <tt>PriorityQueue</tt> containing the elements in the
217 :     * specified collection. The priority queue has an initial
218 :     * capacity of 110% of the size of the specified collection or 1
219 :     * if the collection is empty. This priority queue will be sorted
220 :     * according to the same comparator as the given collection, or
221 :     * according to its elements' natural order if the collection is
222 :     * sorted according to its elements' natural order.
223 :     *
224 :     * @param c the collection whose elements are to be placed
225 :     * into this priority queue.
226 :     * @throws ClassCastException if elements of the specified collection
227 :     * cannot be compared to one another according to the priority
228 :     * queue's ordering.
229 :     * @throws NullPointerException if <tt>c</tt> or any element within it
230 :     * is <tt>null</tt>
231 :     */
232 :     public PriorityQueue(PriorityQueue<? extends E> c) {
233 :     initializeArray(c);
234 :     comparator = (Comparator<? super E>)c.comparator();
235 :     fillFromSorted(c);
236 :     }
237 : dholmes 1.18
238 : dl 1.22 /**
239 :     * Creates a <tt>PriorityQueue</tt> containing the elements in the
240 :     * specified collection. The priority queue has an initial
241 :     * capacity of 110% of the size of the specified collection or 1
242 :     * if the collection is empty. This priority queue will be sorted
243 :     * according to the same comparator as the given collection, or
244 :     * according to its elements' natural order if the collection is
245 :     * sorted according to its elements' natural order.
246 :     *
247 :     * @param c the collection whose elements are to be placed
248 :     * into this priority queue.
249 :     * @throws ClassCastException if elements of the specified collection
250 :     * cannot be compared to one another according to the priority
251 :     * queue's ordering.
252 :     * @throws NullPointerException if <tt>c</tt> or any element within it
253 :     * is <tt>null</tt>
254 :     */
255 :     public PriorityQueue(SortedSet<? extends E> c) {
256 :     initializeArray(c);
257 :     comparator = (Comparator<? super E>)c.comparator();
258 :     fillFromSorted(c);
259 : tim 1.1 }
260 :    
261 : dl 1.22 /**
262 :     * Resize array, if necessary, to be able to hold given index
263 :     */
264 :     private void grow(int index) {
265 :     int newlen = queue.length;
266 :     if (index < newlen) // don't need to grow
267 :     return;
268 :     if (index == Integer.MAX_VALUE)
269 :     throw new OutOfMemoryError();
270 :     while (newlen <= index) {
271 :     if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow
272 :     newlen = Integer.MAX_VALUE;
273 :     else
274 :     newlen <<= 2;
275 :     }
276 :     Object[] newQueue = new Object[newlen];
277 :     System.arraycopy(queue, 0, newQueue, 0, queue.length);
278 :     queue = newQueue;
279 :     }
280 :    
281 : dl 1.36
282 : tim 1.2 /**
283 : dl 1.42 * Inserts the specified element into this priority queue.
284 : tim 1.2 *
285 : dholmes 1.11 * @return <tt>true</tt>
286 :     * @throws ClassCastException if the specified element cannot be compared
287 :     * with elements currently in the priority queue according
288 :     * to the priority queue's ordering.
289 : dholmes 1.18 * @throws NullPointerException if the specified element is <tt>null</tt>.
290 : tim 1.2 */
291 : dholmes 1.18 public boolean offer(E o) {
292 :     if (o == null)
293 : dholmes 1.11 throw new NullPointerException();
294 :     modCount++;
295 :     ++size;
296 :    
297 :     // Grow backing store if necessary
298 : dl 1.22 if (size >= queue.length)
299 :     grow(size);
300 : dholmes 1.11
301 : dholmes 1.18 queue[size] = o;
302 : dholmes 1.11 fixUp(size);
303 :     return true;
304 :     }
305 :    
306 : dl 1.40 public E peek() {
307 : tim 1.2 if (size == 0)
308 :     return null;
309 : tim 1.16 return (E) queue[1];
310 : tim 1.1 }
311 :    
312 : dholmes 1.23 // Collection Methods - the first two override to update docs
313 : dholmes 1.11
314 :     /**
315 : dholmes 1.23 * Adds the specified element to this queue.
316 :     * @return <tt>true</tt> (as per the general contract of
317 :     * <tt>Collection.add</tt>).
318 :     *
319 : dl 1.40 * @throws NullPointerException if the specified element is <tt>null</tt>.
320 : dholmes 1.15 * @throws ClassCastException if the specified element cannot be compared
321 :     * with elements currently in the priority queue according
322 :     * to the priority queue's ordering.
323 : dholmes 1.11 */
324 : dholmes 1.18 public boolean add(E o) {
325 : dl 1.41 return offer(o);
326 : tim 1.14 }
327 : dholmes 1.11
328 : dl 1.12 public boolean remove(Object o) {
329 : dholmes 1.11 if (o == null)
330 : dholmes 1.15 return false;
331 : tim 1.2
332 :     if (comparator == null) {
333 :     for (int i = 1; i <= size; i++) {
334 : tim 1.16 if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
335 : dl 1.36 removeAt(i);
336 : tim 1.2 return true;
337 :     }
338 :     }
339 :     } else {
340 :     for (int i = 1; i <= size; i++) {
341 : tim 1.16 if (comparator.compare((E)queue[i], (E)o) == 0) {
342 : dl 1.36 removeAt(i);
343 : tim 1.2 return true;
344 :     }
345 :     }
346 :     }
347 : tim 1.1 return false;
348 :     }
349 : tim 1.2
350 : dholmes 1.23 /**
351 :     * Returns an iterator over the elements in this queue. The iterator
352 :     * does not return the elements in any particular order.
353 :     *
354 :     * @return an iterator over the elements in this queue.
355 :     */
356 : tim 1.2 public Iterator<E> iterator() {
357 : dl 1.7 return new Itr();
358 : tim 1.2 }
359 :    
360 :     private class Itr implements Iterator<E> {
361 : dl 1.35
362 : dl 1.7 /**
363 :     * Index (into queue array) of element to be returned by
364 : tim 1.2 * subsequent call to next.
365 : dl 1.7 */
366 :     private int cursor = 1;
367 : tim 1.2
368 : dl 1.7 /**
369 : dl 1.36 * Index of element returned by most recent call to next,
370 :     * unless that element came from the forgetMeNot list.
371 :     * Reset to 0 if element is deleted by a call to remove.
372 : dl 1.7 */
373 :     private int lastRet = 0;
374 :    
375 :     /**
376 :     * The modCount value that the iterator believes that the backing
377 :     * List should have. If this expectation is violated, the iterator
378 :     * has detected concurrent modification.
379 :     */
380 :     private int expectedModCount = modCount;
381 : tim 1.2
382 : dl 1.36 /**
383 :     * A list of elements that were moved from the unvisited portion of
384 :     * the heap into the visited portion as a result of "unlucky" element
385 :     * removals during the iteration. (Unlucky element removals are those
386 :     * that require a fixup instead of a fixdown.) We must visit all of
387 :     * the elements in this list to complete the iteration. We do this
388 :     * after we've completed the "normal" iteration.
389 :     *
390 :     * We expect that most iterations, even those involving removals,
391 :     * will not use need to store elements in this field.
392 :     */
393 :     private ArrayList<E> forgetMeNot = null;
394 :    
395 :     /**
396 :     * Element returned by the most recent call to next iff that
397 :     * element was drawn from the forgetMeNot list.
398 :     */
399 :     private Object lastRetElt = null;
400 : dl 1.35
401 : dl 1.7 public boolean hasNext() {
402 : dl 1.36 return cursor <= size || forgetMeNot != null;
403 : dl 1.7 }
404 :    
405 :     public E next() {
406 : tim 1.2 checkForComodification();
407 : dl 1.36 E result;
408 :     if (cursor <= size) {
409 :     result = (E) queue[cursor];
410 :     lastRet = cursor++;
411 :     }
412 :     else if (forgetMeNot == null)
413 : dl 1.7 throw new NoSuchElementException();
414 : dl 1.36 else {
415 :     int remaining = forgetMeNot.size();
416 :     result = forgetMeNot.remove(remaining - 1);
417 :     if (remaining == 1)
418 :     forgetMeNot = null;
419 :     lastRet = 0;
420 :     lastRetElt = result;
421 :     }
422 : tim 1.2 return result;
423 : dl 1.7 }
424 : tim 1.2
425 : dl 1.7 public void remove() {
426 : tim 1.2 checkForComodification();
427 :    
428 : dl 1.36 if (lastRet != 0) {
429 :     E moved = PriorityQueue.this.removeAt(lastRet);
430 :     lastRet = 0;
431 :     if (moved == null) {
432 :     cursor--;
433 :     } else {
434 :     if (forgetMeNot == null)
435 : dl 1.37 forgetMeNot = new ArrayList<E>();
436 : dl 1.36 forgetMeNot.add(moved);
437 :     }
438 :     } else if (lastRetElt != null) {
439 :     PriorityQueue.this.remove(lastRetElt);
440 :     lastRetElt = null;
441 :     } else {
442 :     throw new IllegalStateException();
443 : dl 1.35 }
444 :    
445 : tim 1.2 expectedModCount = modCount;
446 : dl 1.7 }
447 : tim 1.2
448 : dl 1.7 final void checkForComodification() {
449 :     if (modCount != expectedModCount)
450 :     throw new ConcurrentModificationException();
451 :     }
452 : tim 1.2 }
453 :    
454 : tim 1.1 public int size() {
455 : tim 1.2 return size;
456 : tim 1.1 }
457 : tim 1.2
458 :     /**
459 :     * Remove all elements from the priority queue.
460 :     */
461 :     public void clear() {
462 :     modCount++;
463 :    
464 :     // Null out element references to prevent memory leak
465 :     for (int i=1; i<=size; i++)
466 :     queue[i] = null;
467 :    
468 :     size = 0;
469 :     }
470 :    
471 : dl 1.40 public E poll() {
472 : dl 1.36 if (size == 0)
473 : dl 1.40 return null;
474 : dl 1.36 modCount++;
475 :    
476 :     E result = (E) queue[1];
477 :     queue[1] = queue[size];
478 :     queue[size--] = null; // Drop extra ref to prevent memory leak
479 :     if (size > 1)
480 :     fixDown(1);
481 :    
482 :     return result;
483 :     }
484 :    
485 :     /**
486 :     * Removes and returns the ith element from queue. (Recall that queue
487 :     * is one-based, so 1 <= i <= size.)
488 : tim 1.2 *
489 : dl 1.36 * Normally this method leaves the elements at positions from 1 up to i-1,
490 :     * inclusive, untouched. Under these circumstances, it returns null.
491 :     * Occasionally, in order to maintain the heap invariant, it must move
492 :     * the last element of the list to some index in the range [2, i-1],
493 :     * and move the element previously at position (i/2) to position i.
494 :     * Under these circumstances, this method returns the element that was
495 :     * previously at the end of the list and is now at some position between
496 :     * 2 and i-1 inclusive.
497 : tim 1.2 */
498 : dl 1.36 private E removeAt(int i) {
499 :     assert i > 0 && i <= size;
500 : tim 1.2 modCount++;
501 :    
502 : dl 1.36 E moved = (E) queue[size];
503 :     queue[i] = moved;
504 : tim 1.2 queue[size--] = null; // Drop extra ref to prevent memory leak
505 : dl 1.35 if (i <= size) {
506 : tim 1.2 fixDown(i);
507 : dl 1.36 if (queue[i] == moved) {
508 :     fixUp(i);
509 :     if (queue[i] != moved)
510 :     return moved;
511 :     }
512 : dl 1.35 }
513 : dl 1.36 return null;
514 : tim 1.1 }
515 :    
516 : tim 1.2 /**
517 :     * Establishes the heap invariant (described above) assuming the heap
518 :     * satisfies the invariant except possibly for the leaf-node indexed by k
519 :     * (which may have a nextExecutionTime less than its parent's).
520 :     *
521 :     * This method functions by "promoting" queue[k] up the hierarchy
522 :     * (by swapping it with its parent) repeatedly until queue[k]
523 :     * is greater than or equal to its parent.
524 :     */
525 :     private void fixUp(int k) {
526 :     if (comparator == null) {
527 :     while (k > 1) {
528 :     int j = k >> 1;
529 : tim 1.16 if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
530 : tim 1.2 break;
531 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
532 : tim 1.2 k = j;
533 :     }
534 :     } else {
535 :     while (k > 1) {
536 : dl 1.35 int j = k >>> 1;
537 : tim 1.16 if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
538 : tim 1.2 break;
539 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
540 : tim 1.2 k = j;
541 :     }
542 :     }
543 :     }
544 :    
545 :     /**
546 :     * Establishes the heap invariant (described above) in the subtree
547 :     * rooted at k, which is assumed to satisfy the heap invariant except
548 :     * possibly for node k itself (which may be greater than its children).
549 :     *
550 :     * This method functions by "demoting" queue[k] down the hierarchy
551 :     * (by swapping it with its smaller child) repeatedly until queue[k]
552 :     * is less than or equal to its children.
553 :     */
554 :     private void fixDown(int k) {
555 :     int j;
556 :     if (comparator == null) {
557 : dl 1.33 while ((j = k << 1) <= size && (j > 0)) {
558 : dl 1.35 if (j<size &&
559 :     ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
560 : tim 1.2 j++; // j indexes smallest kid
561 : dl 1.35
562 : tim 1.16 if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
563 : tim 1.2 break;
564 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
565 : tim 1.2 k = j;
566 :     }
567 :     } else {
568 : dl 1.33 while ((j = k << 1) <= size && (j > 0)) {
569 : dl 1.35 if (j<size &&
570 :     comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
571 : tim 1.2 j++; // j indexes smallest kid
572 : tim 1.16 if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
573 : tim 1.2 break;
574 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
575 : tim 1.2 k = j;
576 :     }
577 :     }
578 : dl 1.36 }
579 : dl 1.35
580 : dl 1.36 /**
581 :     * Establishes the heap invariant (described above) in the entire tree,
582 :     * assuming nothing about the order of the elements prior to the call.
583 :     */
584 :     private void heapify() {
585 :     for (int i = size/2; i >= 1; i--)
586 :     fixDown(i);
587 : tim 1.2 }
588 :    
589 : dholmes 1.23 /**
590 :     * Returns the comparator used to order this collection, or <tt>null</tt>
591 :     * if this collection is sorted according to its elements natural ordering
592 : tim 1.24 * (using <tt>Comparable</tt>).
593 : dholmes 1.23 *
594 :     * @return the comparator used to order this collection, or <tt>null</tt>
595 :     * if this collection is sorted according to its elements natural ordering.
596 :     */
597 : tim 1.16 public Comparator<? super E> comparator() {
598 : tim 1.2 return comparator;
599 :     }
600 : dl 1.5
601 :     /**
602 :     * Save the state of the instance to a stream (that
603 :     * is, serialize it).
604 :     *
605 :     * @serialData The length of the array backing the instance is
606 :     * emitted (int), followed by all of its elements (each an
607 :     * <tt>Object</tt>) in the proper order.
608 : dl 1.7 * @param s the stream
609 : dl 1.5 */
610 : dl 1.22 private void writeObject(java.io.ObjectOutputStream s)
611 : dl 1.5 throws java.io.IOException{
612 : dl 1.7 // Write out element count, and any hidden stuff
613 :     s.defaultWriteObject();
614 : dl 1.5
615 :     // Write out array length
616 :     s.writeInt(queue.length);
617 :    
618 : dl 1.7 // Write out all elements in the proper order.
619 : dl 1.39 for (int i=1; i<=size; i++)
620 : dl 1.5 s.writeObject(queue[i]);
621 :     }
622 :    
623 :     /**
624 :     * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
625 :     * deserialize it).
626 : dl 1.7 * @param s the stream
627 : dl 1.5 */
628 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
629 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
630 : dl 1.7 // Read in size, and any hidden stuff
631 :     s.defaultReadObject();
632 : dl 1.5
633 :     // Read in array length and allocate array
634 :     int arrayLength = s.readInt();
635 : tim 1.16 queue = new Object[arrayLength];
636 : dl 1.5
637 : dl 1.7 // Read in all elements in the proper order.
638 : dl 1.39 for (int i=1; i<=size; i++)
639 : dl 1.37 queue[i] = (E) s.readObject();
640 : dl 1.5 }
641 :    
642 : tim 1.1 }

Doug Lea
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