28 |
|
* elements are added to a priority queue, its capacity grows |
29 |
|
* automatically. The details of the growth policy are not specified. |
30 |
|
* |
31 |
+ |
* <p>The Iterator provided in method {@link #iterator()} is <em>not</em> |
32 |
+ |
* guaranteed to traverse the elements of the PriorityQueue in any |
33 |
+ |
* particular order. If you need ordered traversal, consider using |
34 |
+ |
* <tt>Arrays.sort(pq.toArray())</tt>. |
35 |
+ |
* |
36 |
+ |
* <p> <strong>Note that this implementation is not synchronized.</strong> |
37 |
+ |
* Multiple threads should not access a <tt>PriorityQueue</tt> |
38 |
+ |
* instance concurrently if any of the threads modifies the list |
39 |
+ |
* structurally. Instead, use the thread-safe {@link |
40 |
+ |
* java.util.concurrent.BlockingPriorityQueue} class. |
41 |
+ |
* |
42 |
+ |
* |
43 |
|
* <p>Implementation note: this implementation provides O(log(n)) time |
44 |
|
* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>, |
45 |
|
* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the |
56 |
|
public class PriorityQueue<E> extends AbstractQueue<E> |
57 |
|
implements Queue<E>, java.io.Serializable { |
58 |
|
|
59 |
+ |
private static final long serialVersionUID = -7720805057305804111L; |
60 |
+ |
|
61 |
|
private static final int DEFAULT_INITIAL_CAPACITY = 11; |
62 |
|
|
63 |
|
/** |
190 |
|
*/ |
191 |
|
public PriorityQueue(Collection<? extends E> c) { |
192 |
|
initializeArray(c); |
193 |
< |
if (c instanceof SortedSet<? extends E>) { |
194 |
< |
SortedSet<? extends E> s = (SortedSet<? extends E>) c; |
193 |
> |
if (c instanceof SortedSet) { |
194 |
> |
// @fixme double-cast workaround for compiler |
195 |
> |
SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c; |
196 |
|
comparator = (Comparator<? super E>)s.comparator(); |
197 |
|
fillFromSorted(s); |
198 |
< |
} else if (c instanceof PriorityQueue<? extends E>) { |
198 |
> |
} else if (c instanceof PriorityQueue) { |
199 |
|
PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c; |
200 |
|
comparator = (Comparator<? super E>)s.comparator(); |
201 |
|
fillFromSorted(s); |
431 |
|
checkForComodification(); |
432 |
|
|
433 |
|
PriorityQueue.this.remove(lastRet); |
434 |
< |
if (lastRet < cursor) |
420 |
< |
cursor--; |
434 |
> |
cursor--; |
435 |
|
lastRet = 0; |
436 |
|
expectedModCount = modCount; |
437 |
|
} |
463 |
|
* Removes and returns the ith element from queue. Recall |
464 |
|
* that queue is one-based, so 1 <= i <= size. |
465 |
|
* |
452 |
– |
* XXX: Could further special-case i==size, but is it worth it? |
453 |
– |
* XXX: Could special-case i==0, but is it worth it? |
466 |
|
*/ |
467 |
|
private E remove(int i) { |
468 |
|
assert i <= size; |
517 |
|
private void fixDown(int k) { |
518 |
|
int j; |
519 |
|
if (comparator == null) { |
520 |
< |
while ((j = k << 1) <= size) { |
520 |
> |
while ((j = k << 1) <= size && (j > 0)) { |
521 |
|
if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0) |
522 |
|
j++; // j indexes smallest kid |
523 |
|
if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0) |
526 |
|
k = j; |
527 |
|
} |
528 |
|
} else { |
529 |
< |
while ((j = k << 1) <= size) { |
529 |
> |
while ((j = k << 1) <= size && (j > 0)) { |
530 |
|
if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0) |
531 |
|
j++; // j indexes smallest kid |
532 |
|
if (comparator.compare((E)queue[k], (E)queue[j]) <= 0) |