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1 : dl 1.38 /*
2 :     * %W% %E%
3 :     *
4 : jsr166 1.48 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5 : dl 1.38 * 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 1.47 implements 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 1.46 SortedSet<? extends E> s = (SortedSet<? extends E>)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 1.49 /**
329 :     * Removes a single instance of the specified element from this
330 :     * collection, if it is present.
331 :     */
332 : dl 1.12 public boolean remove(Object o) {
333 : dholmes 1.11 if (o == null)
334 : dholmes 1.15 return false;
335 : tim 1.2
336 :     if (comparator == null) {
337 :     for (int i = 1; i <= size; i++) {
338 : tim 1.16 if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
339 : dl 1.36 removeAt(i);
340 : tim 1.2 return true;
341 :     }
342 :     }
343 :     } else {
344 :     for (int i = 1; i <= size; i++) {
345 : tim 1.16 if (comparator.compare((E)queue[i], (E)o) == 0) {
346 : dl 1.36 removeAt(i);
347 : tim 1.2 return true;
348 :     }
349 :     }
350 :     }
351 : tim 1.1 return false;
352 :     }
353 : tim 1.2
354 : dholmes 1.23 /**
355 :     * Returns an iterator over the elements in this queue. The iterator
356 :     * does not return the elements in any particular order.
357 :     *
358 :     * @return an iterator over the elements in this queue.
359 :     */
360 : tim 1.2 public Iterator<E> iterator() {
361 : dl 1.7 return new Itr();
362 : tim 1.2 }
363 :    
364 :     private class Itr implements Iterator<E> {
365 : dl 1.35
366 : dl 1.7 /**
367 :     * Index (into queue array) of element to be returned by
368 : tim 1.2 * subsequent call to next.
369 : dl 1.7 */
370 :     private int cursor = 1;
371 : tim 1.2
372 : dl 1.7 /**
373 : dl 1.36 * Index of element returned by most recent call to next,
374 :     * unless that element came from the forgetMeNot list.
375 :     * Reset to 0 if element is deleted by a call to remove.
376 : dl 1.7 */
377 :     private int lastRet = 0;
378 :    
379 :     /**
380 :     * The modCount value that the iterator believes that the backing
381 :     * List should have. If this expectation is violated, the iterator
382 :     * has detected concurrent modification.
383 :     */
384 :     private int expectedModCount = modCount;
385 : tim 1.2
386 : dl 1.36 /**
387 :     * A list of elements that were moved from the unvisited portion of
388 :     * the heap into the visited portion as a result of "unlucky" element
389 :     * removals during the iteration. (Unlucky element removals are those
390 :     * that require a fixup instead of a fixdown.) We must visit all of
391 :     * the elements in this list to complete the iteration. We do this
392 :     * after we've completed the "normal" iteration.
393 :     *
394 :     * We expect that most iterations, even those involving removals,
395 :     * will not use need to store elements in this field.
396 :     */
397 :     private ArrayList<E> forgetMeNot = null;
398 :    
399 :     /**
400 :     * Element returned by the most recent call to next iff that
401 :     * element was drawn from the forgetMeNot list.
402 :     */
403 :     private Object lastRetElt = null;
404 : dl 1.35
405 : dl 1.7 public boolean hasNext() {
406 : dl 1.36 return cursor <= size || forgetMeNot != null;
407 : dl 1.7 }
408 :    
409 :     public E next() {
410 : tim 1.2 checkForComodification();
411 : dl 1.36 E result;
412 :     if (cursor <= size) {
413 :     result = (E) queue[cursor];
414 :     lastRet = cursor++;
415 :     }
416 :     else if (forgetMeNot == null)
417 : dl 1.7 throw new NoSuchElementException();
418 : dl 1.36 else {
419 :     int remaining = forgetMeNot.size();
420 :     result = forgetMeNot.remove(remaining - 1);
421 :     if (remaining == 1)
422 :     forgetMeNot = null;
423 :     lastRet = 0;
424 :     lastRetElt = result;
425 :     }
426 : tim 1.2 return result;
427 : dl 1.7 }
428 : tim 1.2
429 : dl 1.7 public void remove() {
430 : tim 1.2 checkForComodification();
431 :    
432 : dl 1.36 if (lastRet != 0) {
433 :     E moved = PriorityQueue.this.removeAt(lastRet);
434 :     lastRet = 0;
435 :     if (moved == null) {
436 :     cursor--;
437 :     } else {
438 :     if (forgetMeNot == null)
439 : dl 1.37 forgetMeNot = new ArrayList<E>();
440 : dl 1.36 forgetMeNot.add(moved);
441 :     }
442 :     } else if (lastRetElt != null) {
443 :     PriorityQueue.this.remove(lastRetElt);
444 :     lastRetElt = null;
445 :     } else {
446 :     throw new IllegalStateException();
447 : dl 1.35 }
448 :    
449 : tim 1.2 expectedModCount = modCount;
450 : dl 1.7 }
451 : tim 1.2
452 : dl 1.7 final void checkForComodification() {
453 :     if (modCount != expectedModCount)
454 :     throw new ConcurrentModificationException();
455 :     }
456 : tim 1.2 }
457 :    
458 : tim 1.1 public int size() {
459 : tim 1.2 return size;
460 : tim 1.1 }
461 : tim 1.2
462 :     /**
463 : dl 1.49 * Removes all elements from the priority queue.
464 :     * The queue will be empty after this call returns.
465 : tim 1.2 */
466 :     public void clear() {
467 :     modCount++;
468 :    
469 :     // Null out element references to prevent memory leak
470 :     for (int i=1; i<=size; i++)
471 :     queue[i] = null;
472 :    
473 :     size = 0;
474 :     }
475 :    
476 : dl 1.40 public E poll() {
477 : dl 1.36 if (size == 0)
478 : dl 1.40 return null;
479 : dl 1.36 modCount++;
480 :    
481 :     E result = (E) queue[1];
482 :     queue[1] = queue[size];
483 :     queue[size--] = null; // Drop extra ref to prevent memory leak
484 :     if (size > 1)
485 :     fixDown(1);
486 :    
487 :     return result;
488 :     }
489 :    
490 :     /**
491 :     * Removes and returns the ith element from queue. (Recall that queue
492 :     * is one-based, so 1 <= i <= size.)
493 : tim 1.2 *
494 : dl 1.36 * Normally this method leaves the elements at positions from 1 up to i-1,
495 :     * inclusive, untouched. Under these circumstances, it returns null.
496 :     * Occasionally, in order to maintain the heap invariant, it must move
497 :     * the last element of the list to some index in the range [2, i-1],
498 :     * and move the element previously at position (i/2) to position i.
499 :     * Under these circumstances, this method returns the element that was
500 :     * previously at the end of the list and is now at some position between
501 :     * 2 and i-1 inclusive.
502 : tim 1.2 */
503 : dl 1.36 private E removeAt(int i) {
504 :     assert i > 0 && i <= size;
505 : tim 1.2 modCount++;
506 :    
507 : dl 1.36 E moved = (E) queue[size];
508 :     queue[i] = moved;
509 : tim 1.2 queue[size--] = null; // Drop extra ref to prevent memory leak
510 : dl 1.35 if (i <= size) {
511 : tim 1.2 fixDown(i);
512 : dl 1.36 if (queue[i] == moved) {
513 :     fixUp(i);
514 :     if (queue[i] != moved)
515 :     return moved;
516 :     }
517 : dl 1.35 }
518 : dl 1.36 return null;
519 : tim 1.1 }
520 :    
521 : tim 1.2 /**
522 :     * Establishes the heap invariant (described above) assuming the heap
523 :     * satisfies the invariant except possibly for the leaf-node indexed by k
524 :     * (which may have a nextExecutionTime less than its parent's).
525 :     *
526 :     * This method functions by "promoting" queue[k] up the hierarchy
527 :     * (by swapping it with its parent) repeatedly until queue[k]
528 :     * is greater than or equal to its parent.
529 :     */
530 :     private void fixUp(int k) {
531 :     if (comparator == null) {
532 :     while (k > 1) {
533 :     int j = k >> 1;
534 : tim 1.16 if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
535 : tim 1.2 break;
536 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
537 : tim 1.2 k = j;
538 :     }
539 :     } else {
540 :     while (k > 1) {
541 : dl 1.35 int j = k >>> 1;
542 : tim 1.16 if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
543 : tim 1.2 break;
544 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
545 : tim 1.2 k = j;
546 :     }
547 :     }
548 :     }
549 :    
550 :     /**
551 :     * Establishes the heap invariant (described above) in the subtree
552 :     * rooted at k, which is assumed to satisfy the heap invariant except
553 :     * possibly for node k itself (which may be greater than its children).
554 :     *
555 :     * This method functions by "demoting" queue[k] down the hierarchy
556 :     * (by swapping it with its smaller child) repeatedly until queue[k]
557 :     * is less than or equal to its children.
558 :     */
559 :     private void fixDown(int k) {
560 :     int j;
561 :     if (comparator == null) {
562 : dl 1.33 while ((j = k << 1) <= size && (j > 0)) {
563 : dl 1.35 if (j<size &&
564 :     ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
565 : tim 1.2 j++; // j indexes smallest kid
566 : dl 1.35
567 : tim 1.16 if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
568 : tim 1.2 break;
569 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
570 : tim 1.2 k = j;
571 :     }
572 :     } else {
573 : dl 1.33 while ((j = k << 1) <= size && (j > 0)) {
574 : dl 1.35 if (j<size &&
575 :     comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
576 : tim 1.2 j++; // j indexes smallest kid
577 : tim 1.16 if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
578 : tim 1.2 break;
579 : tim 1.16 Object tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
580 : tim 1.2 k = j;
581 :     }
582 :     }
583 : dl 1.36 }
584 : dl 1.35
585 : dl 1.36 /**
586 :     * Establishes the heap invariant (described above) in the entire tree,
587 :     * assuming nothing about the order of the elements prior to the call.
588 :     */
589 :     private void heapify() {
590 :     for (int i = size/2; i >= 1; i--)
591 :     fixDown(i);
592 : tim 1.2 }
593 :    
594 : dholmes 1.23 /**
595 :     * Returns the comparator used to order this collection, or <tt>null</tt>
596 :     * if this collection is sorted according to its elements natural ordering
597 : tim 1.24 * (using <tt>Comparable</tt>).
598 : dholmes 1.23 *
599 :     * @return the comparator used to order this collection, or <tt>null</tt>
600 :     * if this collection is sorted according to its elements natural ordering.
601 :     */
602 : tim 1.16 public Comparator<? super E> comparator() {
603 : tim 1.2 return comparator;
604 :     }
605 : dl 1.5
606 :     /**
607 :     * Save the state of the instance to a stream (that
608 :     * is, serialize it).
609 :     *
610 :     * @serialData The length of the array backing the instance is
611 :     * emitted (int), followed by all of its elements (each an
612 :     * <tt>Object</tt>) in the proper order.
613 : dl 1.7 * @param s the stream
614 : dl 1.5 */
615 : dl 1.22 private void writeObject(java.io.ObjectOutputStream s)
616 : dl 1.5 throws java.io.IOException{
617 : dl 1.7 // Write out element count, and any hidden stuff
618 :     s.defaultWriteObject();
619 : dl 1.5
620 :     // Write out array length
621 :     s.writeInt(queue.length);
622 :    
623 : dl 1.7 // Write out all elements in the proper order.
624 : dl 1.39 for (int i=1; i<=size; i++)
625 : dl 1.5 s.writeObject(queue[i]);
626 :     }
627 :    
628 :     /**
629 :     * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
630 :     * deserialize it).
631 : dl 1.7 * @param s the stream
632 : dl 1.5 */
633 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
634 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
635 : dl 1.7 // Read in size, and any hidden stuff
636 :     s.defaultReadObject();
637 : dl 1.5
638 :     // Read in array length and allocate array
639 :     int arrayLength = s.readInt();
640 : tim 1.16 queue = new Object[arrayLength];
641 : dl 1.5
642 : dl 1.7 // Read in all elements in the proper order.
643 : dl 1.39 for (int i=1; i<=size; i++)
644 : dl 1.37 queue[i] = (E) s.readObject();
645 : dl 1.5 }
646 :    
647 : tim 1.1 }

Doug Lea
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