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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 : dl 1.43 * permit insertion of non-comparable objects (doing so may result
19 : dl 1.42 * 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 : dl 1.45 * @param <E> the type of elements held in this collection
63 : tim 1.2 */
64 :     public class PriorityQueue<E> extends AbstractQueue<E>
65 : dl 1.22 implements Queue<E>, java.io.Serializable {
66 : dholmes 1.11
67 : dl 1.31 private static final long serialVersionUID = -7720805057305804111L;
68 : dl 1.30
69 : tim 1.2 private static final int DEFAULT_INITIAL_CAPACITY = 11;
70 : tim 1.1
71 : tim 1.2 /**
72 :     * Priority queue represented as a balanced binary heap: the two children
73 :     * of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is
74 :     * ordered by comparator, or by the elements' natural ordering, if
75 : brian 1.6 * comparator is null: For each node n in the heap and each descendant d
76 :     * of n, n <= d.
77 : tim 1.2 *
78 : brian 1.6 * The element with the lowest value is in queue[1], assuming the queue is
79 :     * nonempty. (A one-based array is used in preference to the traditional
80 :     * zero-based array to simplify parent and child calculations.)
81 : tim 1.2 *
82 :     * queue.length must be >= 2, even if size == 0.
83 :     */
84 : tim 1.16 private transient Object[] queue;
85 : tim 1.1
86 : tim 1.2 /**
87 :     * The number of elements in the priority queue.
88 :     */
89 :     private int size = 0;
90 : tim 1.1
91 : tim 1.2 /**
92 :     * The comparator, or null if priority queue uses elements'
93 :     * natural ordering.
94 :     */
95 : tim 1.16 private final Comparator<? super E> comparator;
96 : tim 1.2
97 :     /**
98 :     * The number of times this priority queue has been
99 :     * <i>structurally modified</i>. See AbstractList for gory details.
100 :     */
101 : dl 1.5 private transient int modCount = 0;
102 : tim 1.2
103 :     /**
104 : dholmes 1.21 * Creates a <tt>PriorityQueue</tt> with the default initial capacity
105 : dl 1.7 * (11) that orders its elements according to their natural
106 : tim 1.24 * ordering (using <tt>Comparable</tt>).
107 : tim 1.2 */
108 :     public PriorityQueue() {
109 : dholmes 1.11 this(DEFAULT_INITIAL_CAPACITY, null);
110 : tim 1.1 }
111 : tim 1.2
112 :     /**
113 : dholmes 1.21 * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
114 : dl 1.7 * that orders its elements according to their natural ordering
115 : tim 1.24 * (using <tt>Comparable</tt>).
116 : tim 1.2 *
117 :     * @param initialCapacity the initial capacity for this priority queue.
118 : dholmes 1.23 * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
119 :     * than 1
120 : tim 1.2 */
121 :     public PriorityQueue(int initialCapacity) {
122 :     this(initialCapacity, null);
123 : tim 1.1 }
124 : tim 1.2
125 :     /**
126 : dholmes 1.21 * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
127 : tim 1.2 * that orders its elements according to the specified comparator.
128 :     *
129 :     * @param initialCapacity the initial capacity for this priority queue.
130 :     * @param comparator the comparator used to order this priority queue.
131 : dholmes 1.11 * If <tt>null</tt> then the order depends on the elements' natural
132 :     * ordering.
133 : dholmes 1.15 * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
134 :     * than 1
135 : tim 1.2 */
136 : dholmes 1.23 public PriorityQueue(int initialCapacity,
137 :     Comparator<? super E> comparator) {
138 : tim 1.2 if (initialCapacity < 1)
139 : dholmes 1.15 throw new IllegalArgumentException();
140 : tim 1.16 this.queue = new Object[initialCapacity + 1];
141 : tim 1.2 this.comparator = comparator;
142 : tim 1.1 }
143 :    
144 : tim 1.2 /**
145 : dl 1.22 * Common code to initialize underlying queue array across
146 :     * constructors below.
147 :     */
148 :     private void initializeArray(Collection<? extends E> c) {
149 :     int sz = c.size();
150 :     int initialCapacity = (int)Math.min((sz * 110L) / 100,
151 :     Integer.MAX_VALUE - 1);
152 :     if (initialCapacity < 1)
153 :     initialCapacity = 1;
154 :    
155 :     this.queue = new Object[initialCapacity + 1];
156 :     }
157 :    
158 :     /**
159 :     * Initially fill elements of the queue array under the
160 :     * knowledge that it is sorted or is another PQ, in which
161 : dl 1.36 * case we can just place the elements in the order presented.
162 : dl 1.22 */
163 :     private void fillFromSorted(Collection<? extends E> c) {
164 :     for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
165 :     queue[++size] = i.next();
166 :     }
167 :    
168 :     /**
169 : dl 1.36 * Initially fill elements of the queue array that is not to our knowledge
170 :     * sorted, so we must rearrange the elements to guarantee the heap
171 :     * invariant.
172 : dl 1.22 */
173 :     private void fillFromUnsorted(Collection<? extends E> c) {
174 :     for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
175 : dl 1.36 queue[++size] = i.next();
176 :     heapify();
177 : dl 1.22 }
178 :    
179 :     /**
180 :     * Creates a <tt>PriorityQueue</tt> containing the elements in the
181 :     * specified collection. The priority queue has an initial
182 :     * capacity of 110% of the size of the specified collection or 1
183 :     * if the collection is empty. If the specified collection is an
184 : tim 1.25 * instance of a {@link java.util.SortedSet} or is another
185 : dl 1.22 * <tt>PriorityQueue</tt>, the priority queue will be sorted
186 :     * according to the same comparator, or according to its elements'
187 :     * natural order if the collection is sorted according to its
188 :     * elements' natural order. Otherwise, the priority queue is
189 :     * ordered according to its elements' natural order.
190 : tim 1.2 *
191 : dholmes 1.15 * @param c the collection whose elements are to be placed
192 : tim 1.2 * into this priority queue.
193 :     * @throws ClassCastException if elements of the specified collection
194 :     * cannot be compared to one another according to the priority
195 :     * queue's ordering.
196 : dholmes 1.15 * @throws NullPointerException if <tt>c</tt> or any element within it
197 :     * is <tt>null</tt>
198 : tim 1.2 */
199 : tim 1.16 public PriorityQueue(Collection<? extends E> c) {
200 : dl 1.22 initializeArray(c);
201 : dl 1.27 if (c instanceof SortedSet) {
202 : dl 1.28 // @fixme double-cast workaround for compiler
203 :     SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
204 : dl 1.22 comparator = (Comparator<? super E>)s.comparator();
205 :     fillFromSorted(s);
206 : dl 1.27 } else if (c instanceof PriorityQueue) {
207 : dl 1.22 PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
208 :     comparator = (Comparator<? super E>)s.comparator();
209 :     fillFromSorted(s);
210 : tim 1.26 } else {
211 : tim 1.2 comparator = null;
212 : dl 1.22 fillFromUnsorted(c);
213 : tim 1.2 }
214 : dl 1.22 }
215 :    
216 :     /**
217 :     * Creates a <tt>PriorityQueue</tt> containing the elements in the
218 :     * specified collection. The priority queue has an initial
219 :     * capacity of 110% of the size of the specified collection or 1
220 :     * if the collection is empty. This priority queue will be sorted
221 :     * according to the same comparator as the given collection, or
222 :     * according to its elements' natural order if the collection is
223 :     * sorted according to its elements' natural order.
224 :     *
225 :     * @param c the collection whose elements are to be placed
226 :     * into this priority queue.
227 :     * @throws ClassCastException if elements of the specified collection
228 :     * cannot be compared to one another according to the priority
229 :     * queue's ordering.
230 :     * @throws NullPointerException if <tt>c</tt> or any element within it
231 :     * is <tt>null</tt>
232 :     */
233 :     public PriorityQueue(PriorityQueue<? extends E> c) {
234 :     initializeArray(c);
235 :     comparator = (Comparator<? super E>)c.comparator();
236 :     fillFromSorted(c);
237 :     }
238 : dholmes 1.18
239 : dl 1.22 /**
240 :     * Creates a <tt>PriorityQueue</tt> containing the elements in the
241 :     * specified collection. The priority queue has an initial
242 :     * capacity of 110% of the size of the specified collection or 1
243 :     * if the collection is empty. This priority queue will be sorted
244 :     * according to the same comparator as the given collection, or
245 :     * according to its elements' natural order if the collection is
246 :     * sorted according to its elements' natural order.
247 :     *
248 :     * @param c the collection whose elements are to be placed
249 :     * into this priority queue.
250 :     * @throws ClassCastException if elements of the specified collection
251 :     * cannot be compared to one another according to the priority
252 :     * queue's ordering.
253 :     * @throws NullPointerException if <tt>c</tt> or any element within it
254 :     * is <tt>null</tt>
255 :     */
256 :     public PriorityQueue(SortedSet<? extends E> c) {
257 :     initializeArray(c);
258 :     comparator = (Comparator<? super E>)c.comparator();
259 :     fillFromSorted(c);
260 : tim 1.1 }
261 :    
262 : dl 1.22 /**
263 :     * Resize array, if necessary, to be able to hold given index
264 :     */
265 :     private void grow(int index) {
266 :     int newlen = queue.length;
267 :     if (index < newlen) // don't need to grow
268 :     return;
269 :     if (index == Integer.MAX_VALUE)
270 :     throw new OutOfMemoryError();
271 :     while (newlen <= index) {
272 :     if (newlen >= Integer.MAX_VALUE / 2) // avoid overflow
273 :     newlen = Integer.MAX_VALUE;
274 :     else
275 :     newlen <<= 2;
276 :     }
277 :     Object[] newQueue = new Object[newlen];
278 :     System.arraycopy(queue, 0, newQueue, 0, queue.length);
279 :     queue = newQueue;
280 :     }
281 :    
282 : dl 1.36
283 : tim 1.2 /**
284 : dl 1.42 * Inserts the specified element into this priority queue.
285 : tim 1.2 *
286 : dholmes 1.11 * @return <tt>true</tt>
287 :     * @throws ClassCastException if the specified element cannot be compared
288 :     * with elements currently in the priority queue according
289 :     * to the priority queue's ordering.
290 : dholmes 1.18 * @throws NullPointerException if the specified element is <tt>null</tt>.
291 : tim 1.2 */
292 : dholmes 1.18 public boolean offer(E o) {
293 :     if (o == null)
294 : dholmes 1.11 throw new NullPointerException();
295 :     modCount++;
296 :     ++size;
297 :    
298 :     // Grow backing store if necessary
299 : dl 1.22 if (size >= queue.length)
300 :     grow(size);
301 : dholmes 1.11
302 : dholmes 1.18 queue[size] = o;
303 : dholmes 1.11 fixUp(size);
304 :     return true;
305 :     }
306 :    
307 : dl 1.40 public E peek() {
308 : tim 1.2 if (size == 0)
309 :     return null;
310 : tim 1.16 return (E) queue[1];
311 : tim 1.1 }
312 :    
313 : dholmes 1.23 // Collection Methods - the first two override to update docs
314 : dholmes 1.11
315 :     /**
316 : dholmes 1.23 * Adds the specified element to this queue.
317 :     * @return <tt>true</tt> (as per the general contract of
318 :     * <tt>Collection.add</tt>).
319 :     *
320 : dl 1.40 * @throws NullPointerException if the specified element is <tt>null</tt>.
321 : dholmes 1.15 * @throws ClassCastException if the specified element cannot be compared
322 :     * with elements currently in the priority queue according
323 :     * to the priority queue's ordering.
324 : dholmes 1.11 */
325 : dholmes 1.18 public boolean add(E o) {
326 : dl 1.41 return offer(o);
327 : tim 1.14 }
328 : dholmes 1.11
329 : dl 1.12 public boolean remove(Object o) {
330 : dholmes 1.11 if (o == null)
331 : dholmes 1.15 return false;
332 : tim 1.2
333 :     if (comparator == null) {
334 :     for (int i = 1; i <= size; i++) {
335 : tim 1.16 if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
336 : dl 1.36 removeAt(i);
337 : tim 1.2 return true;
338 :     }
339 :     }
340 :     } else {
341 :     for (int i = 1; i <= size; i++) {
342 : tim 1.16 if (comparator.compare((E)queue[i], (E)o) == 0) {
343 : dl 1.36 removeAt(i);
344 : tim 1.2 return true;
345 :     }
346 :     }
347 :     }
348 : tim 1.1 return false;
349 :     }
350 : tim 1.2
351 : dholmes 1.23 /**
352 :     * Returns an iterator over the elements in this queue. The iterator
353 :     * does not return the elements in any particular order.
354 :     *
355 :     * @return an iterator over the elements in this queue.
356 :     */
357 : tim 1.2 public Iterator<E> iterator() {
358 : dl 1.7 return new Itr();
359 : tim 1.2 }
360 :    
361 :     private class Itr implements Iterator<E> {
362 : dl 1.35
363 : dl 1.7 /**
364 :     * Index (into queue array) of element to be returned by
365 : tim 1.2 * subsequent call to next.
366 : dl 1.7 */
367 :     private int cursor = 1;
368 : tim 1.2
369 : dl 1.7 /**
370 : dl 1.36 * Index of element returned by most recent call to next,
371 :     * unless that element came from the forgetMeNot list.
372 :     * Reset to 0 if element is deleted by a call to remove.
373 : dl 1.7 */
374 :     private int lastRet = 0;
375 :    
376 :     /**
377 :     * The modCount value that the iterator believes that the backing
378 :     * List should have. If this expectation is violated, the iterator
379 :     * has detected concurrent modification.
380 :     */
381 :     private int expectedModCount = modCount;
382 : tim 1.2
383 : dl 1.36 /**
384 :     * A list of elements that were moved from the unvisited portion of
385 :     * the heap into the visited portion as a result of "unlucky" element
386 :     * removals during the iteration. (Unlucky element removals are those
387 :     * that require a fixup instead of a fixdown.) We must visit all of
388 :     * the elements in this list to complete the iteration. We do this
389 :     * after we've completed the "normal" iteration.
390 :     *
391 :     * We expect that most iterations, even those involving removals,
392 :     * will not use need to store elements in this field.
393 :     */
394 :     private ArrayList<E> forgetMeNot = null;
395 :    
396 :     /**
397 :     * Element returned by the most recent call to next iff that
398 :     * element was drawn from the forgetMeNot list.
399 :     */
400 :     private Object lastRetElt = null;
401 : dl 1.35
402 : dl 1.7 public boolean hasNext() {
403 : dl 1.36 return cursor <= size || forgetMeNot != null;
404 : dl 1.7 }
405 :    
406 :     public E next() {
407 : tim 1.2 checkForComodification();
408 : dl 1.36 E result;
409 :     if (cursor <= size) {
410 :     result = (E) queue[cursor];
411 :     lastRet = cursor++;
412 :     }
413 :     else if (forgetMeNot == null)
414 : dl 1.7 throw new NoSuchElementException();
415 : dl 1.36 else {
416 :     int remaining = forgetMeNot.size();
417 :     result = forgetMeNot.remove(remaining - 1);
418 :     if (remaining == 1)
419 :     forgetMeNot = null;
420 :     lastRet = 0;
421 :     lastRetElt = result;
422 :     }
423 : tim 1.2 return result;
424 : dl 1.7 }
425 : tim 1.2
426 : dl 1.7 public void remove() {
427 : tim 1.2 checkForComodification();
428 :    
429 : dl 1.36 if (lastRet != 0) {
430 :     E moved = PriorityQueue.this.removeAt(lastRet);
431 :     lastRet = 0;
432 :     if (moved == null) {
433 :     cursor--;
434 :     } else {
435 :     if (forgetMeNot == null)
436 : dl 1.37 forgetMeNot = new ArrayList<E>();
437 : dl 1.36 forgetMeNot.add(moved);
438 :     }
439 :     } else if (lastRetElt != null) {
440 :     PriorityQueue.this.remove(lastRetElt);
441 :     lastRetElt = null;
442 :     } else {
443 :     throw new IllegalStateException();
444 : dl 1.35 }
445 :    
446 : tim 1.2 expectedModCount = modCount;
447 : dl 1.7 }
448 : tim 1.2
449 : dl 1.7 final void checkForComodification() {
450 :     if (modCount != expectedModCount)
451 :     throw new ConcurrentModificationException();
452 :     }
453 : tim 1.2 }
454 :    
455 : tim 1.1 public int size() {
456 : tim 1.2 return size;
457 : tim 1.1 }
458 : tim 1.2
459 :     /**
460 :     * Remove all elements from the priority queue.
461 :     */
462 :     public void clear() {
463 :     modCount++;
464 :    
465 :     // Null out element references to prevent memory leak
466 :     for (int i=1; i<=size; i++)
467 :     queue[i] = null;
468 :    
469 :     size = 0;
470 :     }
471 :    
472 : dl 1.40 public E poll() {
473 : dl 1.36 if (size == 0)
474 : dl 1.40 return null;
475 : dl 1.36 modCount++;
476 :    
477 :     E result = (E) queue[1];
478 :     queue[1] = queue[size];
479 :     queue[size--] = null; // Drop extra ref to prevent memory leak
480 :     if (size > 1)
481 :     fixDown(1);
482 :    
483 :     return result;
484 :     }
485 :    
486 :     /**
487 :     * Removes and returns the ith element from queue. (Recall that queue
488 :     * is one-based, so 1 <= i <= size.)
489 : tim 1.2 *
490 : dl 1.36 * Normally this method leaves the elements at positions from 1 up to i-1,
491 :     * inclusive, untouched. Under these circumstances, it returns null.
492 :     * Occasionally, in order to maintain the heap invariant, it must move
493 :     * the last element of the list to some index in the range [2, i-1],
494 :     * and move the element previously at position (i/2) to position i.
495 :     * Under these circumstances, this method returns the element that was
496 :     * previously at the end of the list and is now at some position between
497 :     * 2 and i-1 inclusive.
498 : tim 1.2 */
499 : dl 1.36 private E removeAt(int i) {
500 :     assert i > 0 && i <= size;
501 : tim 1.2 modCount++;
502 :    
503 : dl 1.36 E moved = (E) queue[size];
504 :     queue[i] = moved;
505 : tim 1.2 queue[size--] = null; // Drop extra ref to prevent memory leak
506 : dl 1.35 if (i <= size) {
507 : tim 1.2 fixDown(i);
508 : dl 1.36 if (queue[i] == moved) {
509 :     fixUp(i);
510 :     if (queue[i] != moved)
511 :     return moved;
512 :     }
513 : dl 1.35 }
514 : dl 1.36 return null;
515 : tim 1.1 }
516 :    
517 : tim 1.2 /**
518 :     * Establishes the heap invariant (described above) assuming the heap
519 :     * satisfies the invariant except possibly for the leaf-node indexed by k
520 :     * (which may have a nextExecutionTime less than its parent's).
521 :     *
522 :     * This method functions by "promoting" queue[k] up the hierarchy
523 :     * (by swapping it with its parent) repeatedly until queue[k]
524 :     * is greater than or equal to its parent.
525 :     */
526 :     private void fixUp(int k) {
527 :     if (comparator == null) {
528 :     while (k > 1) {
529 :     int j = k >> 1;
530 : tim 1.16 if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
531 : tim 1.2 break;
532 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
533 : tim 1.2 k = j;
534 :     }
535 :     } else {
536 :     while (k > 1) {
537 : dl 1.35 int j = k >>> 1;
538 : tim 1.16 if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
539 : tim 1.2 break;
540 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
541 : tim 1.2 k = j;
542 :     }
543 :     }
544 :     }
545 :    
546 :     /**
547 :     * Establishes the heap invariant (described above) in the subtree
548 :     * rooted at k, which is assumed to satisfy the heap invariant except
549 :     * possibly for node k itself (which may be greater than its children).
550 :     *
551 :     * This method functions by "demoting" queue[k] down the hierarchy
552 :     * (by swapping it with its smaller child) repeatedly until queue[k]
553 :     * is less than or equal to its children.
554 :     */
555 :     private void fixDown(int k) {
556 :     int j;
557 :     if (comparator == null) {
558 : dl 1.33 while ((j = k << 1) <= size && (j > 0)) {
559 : dl 1.35 if (j<size &&
560 :     ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
561 : tim 1.2 j++; // j indexes smallest kid
562 : dl 1.35
563 : tim 1.16 if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
564 : tim 1.2 break;
565 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
566 : tim 1.2 k = j;
567 :     }
568 :     } else {
569 : dl 1.33 while ((j = k << 1) <= size && (j > 0)) {
570 : dl 1.35 if (j<size &&
571 :     comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
572 : tim 1.2 j++; // j indexes smallest kid
573 : tim 1.16 if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
574 : tim 1.2 break;
575 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
576 : tim 1.2 k = j;
577 :     }
578 :     }
579 : dl 1.36 }
580 : dl 1.35
581 : dl 1.36 /**
582 :     * Establishes the heap invariant (described above) in the entire tree,
583 :     * assuming nothing about the order of the elements prior to the call.
584 :     */
585 :     private void heapify() {
586 :     for (int i = size/2; i >= 1; i--)
587 :     fixDown(i);
588 : tim 1.2 }
589 :    
590 : dholmes 1.23 /**
591 :     * Returns the comparator used to order this collection, or <tt>null</tt>
592 :     * if this collection is sorted according to its elements natural ordering
593 : tim 1.24 * (using <tt>Comparable</tt>).
594 : dholmes 1.23 *
595 :     * @return the comparator used to order this collection, or <tt>null</tt>
596 :     * if this collection is sorted according to its elements natural ordering.
597 :     */
598 : tim 1.16 public Comparator<? super E> comparator() {
599 : tim 1.2 return comparator;
600 :     }
601 : dl 1.5
602 :     /**
603 :     * Save the state of the instance to a stream (that
604 :     * is, serialize it).
605 :     *
606 :     * @serialData The length of the array backing the instance is
607 :     * emitted (int), followed by all of its elements (each an
608 :     * <tt>Object</tt>) in the proper order.
609 : dl 1.7 * @param s the stream
610 : dl 1.5 */
611 : dl 1.22 private void writeObject(java.io.ObjectOutputStream s)
612 : dl 1.5 throws java.io.IOException{
613 : dl 1.7 // Write out element count, and any hidden stuff
614 :     s.defaultWriteObject();
615 : dl 1.5
616 :     // Write out array length
617 :     s.writeInt(queue.length);
618 :    
619 : dl 1.7 // Write out all elements in the proper order.
620 : dl 1.39 for (int i=1; i<=size; i++)
621 : dl 1.5 s.writeObject(queue[i]);
622 :     }
623 :    
624 :     /**
625 :     * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
626 :     * deserialize it).
627 : dl 1.7 * @param s the stream
628 : dl 1.5 */
629 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
630 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
631 : dl 1.7 // Read in size, and any hidden stuff
632 :     s.defaultReadObject();
633 : dl 1.5
634 :     // Read in array length and allocate array
635 :     int arrayLength = s.readInt();
636 : tim 1.16 queue = new Object[arrayLength];
637 : dl 1.5
638 : dl 1.7 // Read in all elements in the proper order.
639 : dl 1.39 for (int i=1; i<=size; i++)
640 : dl 1.37 queue[i] = (E) s.readObject();
641 : dl 1.5 }
642 :    
643 : tim 1.1 }

Doug Lea
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