[cvs] / jsr166 / src / main / java / util / PriorityQueue.java Repository:
ViewVC logotype

Annotation of /jsr166/src/main/java/util/PriorityQueue.java

Parent Directory Parent Directory | Revision Log Revision Log


Revision 1.99 - (view) (download)

1 : dl 1.38 /*
2 : dl 1.81 * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
3 : jsr166 1.67 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 : dl 1.38 *
5 : jsr166 1.67 * 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 : dl 1.81 * published by the Free Software Foundation. Oracle designates this
8 : jsr166 1.67 * particular file as subject to the "Classpath" exception as provided
9 : dl 1.81 * by Oracle in the LICENSE file that accompanied this code.
10 : jsr166 1.67 *
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 : jsr166 1.71 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 :     * or visit www.oracle.com if you need additional information or have any
23 :     * questions.
24 : dl 1.38 */
25 :    
26 :     package java.util;
27 : dl 1.89 import java.util.function.Consumer;
28 : dl 1.81 import java.util.stream.Stream;
29 : tim 1.1
30 :     /**
31 : jsr166 1.63 * An unbounded priority {@linkplain Queue queue} based on a priority heap.
32 :     * The elements of the priority queue are ordered according to their
33 :     * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
34 :     * provided at queue construction time, depending on which constructor is
35 :     * used. A priority queue does not permit {@code null} elements.
36 :     * A priority queue relying on natural ordering also does not permit
37 :     * insertion of non-comparable objects (doing so may result in
38 :     * {@code ClassCastException}).
39 : dl 1.40 *
40 : dl 1.41 * <p>The <em>head</em> of this queue is the <em>least</em> element
41 :     * with respect to the specified ordering. If multiple elements are
42 :     * tied for least value, the head is one of those elements -- ties are
43 : jsr166 1.63 * broken arbitrarily. The queue retrieval operations {@code poll},
44 :     * {@code remove}, {@code peek}, and {@code element} access the
45 : dl 1.42 * element at the head of the queue.
46 : tim 1.14 *
47 : dl 1.41 * <p>A priority queue is unbounded, but has an internal
48 :     * <i>capacity</i> governing the size of an array used to store the
49 : dl 1.40 * elements on the queue. It is always at least as large as the queue
50 :     * size. As elements are added to a priority queue, its capacity
51 :     * grows automatically. The details of the growth policy are not
52 :     * specified.
53 : tim 1.2 *
54 : dl 1.50 * <p>This class and its iterator implement all of the
55 :     * <em>optional</em> methods of the {@link Collection} and {@link
56 : dl 1.52 * Iterator} interfaces. The Iterator provided in method {@link
57 :     * #iterator()} is <em>not</em> guaranteed to traverse the elements of
58 :     * the priority queue in any particular order. If you need ordered
59 : jsr166 1.63 * traversal, consider using {@code Arrays.sort(pq.toArray())}.
60 : dl 1.29 *
61 : jsr166 1.82 * <p><strong>Note that this implementation is not synchronized.</strong>
62 : jsr166 1.63 * Multiple threads should not access a {@code PriorityQueue}
63 :     * instance concurrently if any of the threads modifies the queue.
64 :     * Instead, use the thread-safe {@link
65 : dl 1.88 * java.util.concurrent.PriorityBlockingQueue} class.
66 : dl 1.29 *
67 : jsr166 1.63 * <p>Implementation note: this implementation provides
68 : jsr166 1.98 * O(log(n)) time for the enqueuing and dequeuing methods
69 : jsr166 1.63 * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
70 :     * linear time for the {@code remove(Object)} and {@code contains(Object)}
71 :     * methods; and constant time for the retrieval methods
72 :     * ({@code peek}, {@code element}, and {@code size}).
73 : tim 1.2 *
74 :     * <p>This class is a member of the
75 : jsr166 1.65 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
76 : tim 1.2 * Java Collections Framework</a>.
77 : jsr166 1.63 *
78 : dl 1.7 * @since 1.5
79 : jsr166 1.63 * @author Josh Bloch, Doug Lea
80 : dl 1.45 * @param <E> the type of elements held in this collection
81 : tim 1.2 */
82 :     public class PriorityQueue<E> extends AbstractQueue<E>
83 : dl 1.47 implements java.io.Serializable {
84 : dholmes 1.11
85 : dl 1.31 private static final long serialVersionUID = -7720805057305804111L;
86 : dl 1.30
87 : tim 1.2 private static final int DEFAULT_INITIAL_CAPACITY = 11;
88 : tim 1.1
89 : tim 1.2 /**
90 : dl 1.55 * Priority queue represented as a balanced binary heap: the two
91 :     * children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The
92 :     * priority queue is ordered by comparator, or by the elements'
93 :     * natural ordering, if comparator is null: For each node n in the
94 :     * heap and each descendant d of n, n <= d. The element with the
95 :     * lowest value is in queue[0], assuming the queue is nonempty.
96 : tim 1.2 */
97 : dl 1.81 transient Object[] queue; // non-private to simplify nested class access
98 : tim 1.1
99 : tim 1.2 /**
100 :     * The number of elements in the priority queue.
101 :     */
102 : jsr166 1.99 private int size;
103 : tim 1.1
104 : tim 1.2 /**
105 :     * The comparator, or null if priority queue uses elements'
106 :     * natural ordering.
107 :     */
108 : tim 1.16 private final Comparator<? super E> comparator;
109 : tim 1.2
110 :     /**
111 :     * The number of times this priority queue has been
112 :     * <i>structurally modified</i>. See AbstractList for gory details.
113 :     */
114 : dl 1.81 transient int modCount = 0; // non-private to simplify nested class access
115 : tim 1.2
116 :     /**
117 : jsr166 1.63 * Creates a {@code PriorityQueue} with the default initial
118 : dl 1.52 * capacity (11) that orders its elements according to their
119 :     * {@linkplain Comparable natural ordering}.
120 : tim 1.2 */
121 :     public PriorityQueue() {
122 : dholmes 1.11 this(DEFAULT_INITIAL_CAPACITY, null);
123 : tim 1.1 }
124 : tim 1.2
125 :     /**
126 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial
127 : dl 1.52 * capacity that orders its elements according to their
128 :     * {@linkplain Comparable natural ordering}.
129 : tim 1.2 *
130 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
131 : jsr166 1.63 * @throws IllegalArgumentException if {@code initialCapacity} is less
132 :     * than 1
133 : tim 1.2 */
134 :     public PriorityQueue(int initialCapacity) {
135 :     this(initialCapacity, null);
136 : tim 1.1 }
137 : tim 1.2
138 :     /**
139 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial capacity
140 : tim 1.2 * that orders its elements according to the specified comparator.
141 :     *
142 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
143 : jsr166 1.63 * @param comparator the comparator that will be used to order this
144 :     * priority queue. If {@code null}, the {@linkplain Comparable
145 :     * natural ordering} of the elements will be used.
146 :     * @throws IllegalArgumentException if {@code initialCapacity} is
147 : dl 1.52 * less than 1
148 : tim 1.2 */
149 : dl 1.52 public PriorityQueue(int initialCapacity,
150 : dholmes 1.23 Comparator<? super E> comparator) {
151 : dl 1.55 // Note: This restriction of at least one is not actually needed,
152 :     // but continues for 1.5 compatibility
153 : tim 1.2 if (initialCapacity < 1)
154 : dholmes 1.15 throw new IllegalArgumentException();
155 : dl 1.55 this.queue = new Object[initialCapacity];
156 : tim 1.2 this.comparator = comparator;
157 : tim 1.1 }
158 : jsr166 1.56
159 : dl 1.22 /**
160 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
161 :     * specified collection. If the specified collection is an instance of
162 :     * a {@link SortedSet} or is another {@code PriorityQueue}, this
163 :     * priority queue will be ordered according to the same ordering.
164 :     * Otherwise, this priority queue will be ordered according to the
165 :     * {@linkplain Comparable natural ordering} of its elements.
166 : tim 1.2 *
167 : dl 1.52 * @param c the collection whose elements are to be placed
168 :     * into this priority queue
169 : tim 1.2 * @throws ClassCastException if elements of the specified collection
170 :     * cannot be compared to one another according to the priority
171 : dl 1.52 * queue's ordering
172 :     * @throws NullPointerException if the specified collection or any
173 :     * of its elements are null
174 : tim 1.2 */
175 : jsr166 1.70 @SuppressWarnings("unchecked")
176 : tim 1.16 public PriorityQueue(Collection<? extends E> c) {
177 : jsr166 1.70 if (c instanceof SortedSet<?>) {
178 :     SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
179 :     this.comparator = (Comparator<? super E>) ss.comparator();
180 :     initElementsFromCollection(ss);
181 :     }
182 :     else if (c instanceof PriorityQueue<?>) {
183 :     PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
184 :     this.comparator = (Comparator<? super E>) pq.comparator();
185 :     initFromPriorityQueue(pq);
186 :     }
187 : dl 1.55 else {
188 : jsr166 1.70 this.comparator = null;
189 :     initFromCollection(c);
190 : tim 1.2 }
191 : dl 1.22 }
192 :    
193 :     /**
194 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
195 : dl 1.55 * specified priority queue. This priority queue will be
196 : dl 1.52 * ordered according to the same ordering as the given priority
197 :     * queue.
198 :     *
199 :     * @param c the priority queue whose elements are to be placed
200 :     * into this priority queue
201 : jsr166 1.63 * @throws ClassCastException if elements of {@code c} cannot be
202 :     * compared to one another according to {@code c}'s
203 : dl 1.52 * ordering
204 :     * @throws NullPointerException if the specified priority queue or any
205 :     * of its elements are null
206 : dl 1.22 */
207 : jsr166 1.70 @SuppressWarnings("unchecked")
208 : dl 1.22 public PriorityQueue(PriorityQueue<? extends E> c) {
209 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
210 :     initFromPriorityQueue(c);
211 : dl 1.22 }
212 : dholmes 1.18
213 : dl 1.22 /**
214 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
215 :     * specified sorted set. This priority queue will be ordered
216 : dl 1.52 * according to the same ordering as the given sorted set.
217 :     *
218 :     * @param c the sorted set whose elements are to be placed
219 : jsr166 1.63 * into this priority queue
220 : dl 1.52 * @throws ClassCastException if elements of the specified sorted
221 :     * set cannot be compared to one another according to the
222 :     * sorted set's ordering
223 :     * @throws NullPointerException if the specified sorted set or any
224 :     * of its elements are null
225 : dl 1.22 */
226 : jsr166 1.70 @SuppressWarnings("unchecked")
227 : dl 1.22 public PriorityQueue(SortedSet<? extends E> c) {
228 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
229 :     initElementsFromCollection(c);
230 :     }
231 :    
232 :     private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
233 :     if (c.getClass() == PriorityQueue.class) {
234 :     this.queue = c.toArray();
235 :     this.size = c.size();
236 :     } else {
237 :     initFromCollection(c);
238 :     }
239 :     }
240 :    
241 :     private void initElementsFromCollection(Collection<? extends E> c) {
242 :     Object[] a = c.toArray();
243 :     // If c.toArray incorrectly doesn't return Object[], copy it.
244 :     if (a.getClass() != Object[].class)
245 :     a = Arrays.copyOf(a, a.length, Object[].class);
246 :     int len = a.length;
247 :     if (len == 1 || this.comparator != null)
248 :     for (int i = 0; i < len; i++)
249 :     if (a[i] == null)
250 :     throw new NullPointerException();
251 :     this.queue = a;
252 :     this.size = a.length;
253 : tim 1.1 }
254 :    
255 : dl 1.22 /**
256 : jsr166 1.63 * Initializes queue array with elements from the given Collection.
257 :     *
258 : dl 1.55 * @param c the collection
259 : dl 1.22 */
260 : dl 1.55 private void initFromCollection(Collection<? extends E> c) {
261 : jsr166 1.70 initElementsFromCollection(c);
262 :     heapify();
263 : jsr166 1.56 }
264 : dl 1.55
265 :     /**
266 : jsr166 1.70 * The maximum size of array to allocate.
267 :     * Some VMs reserve some header words in an array.
268 :     * Attempts to allocate larger arrays may result in
269 :     * OutOfMemoryError: Requested array size exceeds VM limit
270 :     */
271 :     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
272 :    
273 :     /**
274 : dl 1.55 * Increases the capacity of the array.
275 :     *
276 :     * @param minCapacity the desired minimum capacity
277 :     */
278 :     private void grow(int minCapacity) {
279 : jsr166 1.68 int oldCapacity = queue.length;
280 : dl 1.55 // Double size if small; else grow by 50%
281 : jsr166 1.70 int newCapacity = oldCapacity + ((oldCapacity < 64) ?
282 :     (oldCapacity + 2) :
283 :     (oldCapacity >> 1));
284 :     // overflow-conscious code
285 :     if (newCapacity - MAX_ARRAY_SIZE > 0)
286 :     newCapacity = hugeCapacity(minCapacity);
287 : dl 1.55 queue = Arrays.copyOf(queue, newCapacity);
288 : dl 1.22 }
289 : dl 1.36
290 : jsr166 1.70 private static int hugeCapacity(int minCapacity) {
291 :     if (minCapacity < 0) // overflow
292 :     throw new OutOfMemoryError();
293 :     return (minCapacity > MAX_ARRAY_SIZE) ?
294 :     Integer.MAX_VALUE :
295 :     MAX_ARRAY_SIZE;
296 :     }
297 :    
298 : tim 1.2 /**
299 : dl 1.42 * Inserts the specified element into this priority queue.
300 : tim 1.2 *
301 : jsr166 1.63 * @return {@code true} (as specified by {@link Collection#add})
302 : dl 1.52 * @throws ClassCastException if the specified element cannot be
303 :     * compared with elements currently in this priority queue
304 :     * according to the priority queue's ordering
305 :     * @throws NullPointerException if the specified element is null
306 : tim 1.2 */
307 : dl 1.52 public boolean add(E e) {
308 :     return offer(e);
309 :     }
310 :    
311 :     /**
312 :     * Inserts the specified element into this priority queue.
313 :     *
314 : jsr166 1.63 * @return {@code true} (as specified by {@link Queue#offer})
315 : dl 1.52 * @throws ClassCastException if the specified element cannot be
316 :     * compared with elements currently in this priority queue
317 :     * according to the priority queue's ordering
318 :     * @throws NullPointerException if the specified element is null
319 :     */
320 :     public boolean offer(E e) {
321 :     if (e == null)
322 : dholmes 1.11 throw new NullPointerException();
323 :     modCount++;
324 : dl 1.55 int i = size;
325 :     if (i >= queue.length)
326 :     grow(i + 1);
327 :     size = i + 1;
328 :     if (i == 0)
329 :     queue[0] = e;
330 :     else
331 :     siftUp(i, e);
332 : dholmes 1.11 return true;
333 :     }
334 :    
335 : dl 1.81 @SuppressWarnings("unchecked")
336 : dl 1.40 public E peek() {
337 : jsr166 1.73 return (size == 0) ? null : (E) queue[0];
338 : tim 1.1 }
339 :    
340 : dl 1.52 private int indexOf(Object o) {
341 : jsr166 1.68 if (o != null) {
342 : dl 1.55 for (int i = 0; i < size; i++)
343 :     if (o.equals(queue[i]))
344 :     return i;
345 :     }
346 : dl 1.52 return -1;
347 :     }
348 :    
349 :     /**
350 :     * Removes a single instance of the specified element from this queue,
351 : jsr166 1.63 * if it is present. More formally, removes an element {@code e} such
352 :     * that {@code o.equals(e)}, if this queue contains one or more such
353 :     * elements. Returns {@code true} if and only if this queue contained
354 :     * the specified element (or equivalently, if this queue changed as a
355 :     * result of the call).
356 : dl 1.52 *
357 :     * @param o element to be removed from this queue, if present
358 : jsr166 1.63 * @return {@code true} if this queue changed as a result of the call
359 : dl 1.52 */
360 :     public boolean remove(Object o) {
361 : jsr166 1.68 int i = indexOf(o);
362 :     if (i == -1)
363 :     return false;
364 :     else {
365 :     removeAt(i);
366 :     return true;
367 :     }
368 : dl 1.52 }
369 : dholmes 1.11
370 : jsr166 1.56 /**
371 : dl 1.55 * Version of remove using reference equality, not equals.
372 : jsr166 1.59 * Needed by iterator.remove.
373 : jsr166 1.56 *
374 : dl 1.55 * @param o element to be removed from this queue, if present
375 : jsr166 1.63 * @return {@code true} if removed
376 : dl 1.55 */
377 :     boolean removeEq(Object o) {
378 : jsr166 1.68 for (int i = 0; i < size; i++) {
379 :     if (o == queue[i]) {
380 : dl 1.55 removeAt(i);
381 :     return true;
382 :     }
383 :     }
384 :     return false;
385 :     }
386 :    
387 : dholmes 1.11 /**
388 : jsr166 1.63 * Returns {@code true} if this queue contains the specified element.
389 :     * More formally, returns {@code true} if and only if this queue contains
390 :     * at least one element {@code e} such that {@code o.equals(e)}.
391 : dholmes 1.23 *
392 : dl 1.52 * @param o object to be checked for containment in this queue
393 : jsr166 1.63 * @return {@code true} if this queue contains the specified element
394 : dholmes 1.11 */
395 : dl 1.52 public boolean contains(Object o) {
396 : jsr166 1.68 return indexOf(o) != -1;
397 : tim 1.14 }
398 : dholmes 1.11
399 : dl 1.49 /**
400 : jsr166 1.63 * Returns an array containing all of the elements in this queue.
401 : dl 1.52 * The elements are in no particular order.
402 :     *
403 :     * <p>The returned array will be "safe" in that no references to it are
404 : jsr166 1.63 * maintained by this queue. (In other words, this method must allocate
405 : dl 1.52 * a new array). The caller is thus free to modify the returned array.
406 :     *
407 : jsr166 1.63 * <p>This method acts as bridge between array-based and collection-based
408 :     * APIs.
409 :     *
410 : jsr166 1.59 * @return an array containing all of the elements in this queue
411 : dl 1.49 */
412 : dl 1.52 public Object[] toArray() {
413 : dl 1.55 return Arrays.copyOf(queue, size);
414 : dl 1.52 }
415 : tim 1.2
416 : dl 1.52 /**
417 : jsr166 1.63 * Returns an array containing all of the elements in this queue; the
418 :     * runtime type of the returned array is that of the specified array.
419 :     * The returned array elements are in no particular order.
420 :     * If the queue fits in the specified array, it is returned therein.
421 :     * Otherwise, a new array is allocated with the runtime type of the
422 :     * specified array and the size of this queue.
423 : dl 1.52 *
424 :     * <p>If the queue fits in the specified array with room to spare
425 :     * (i.e., the array has more elements than the queue), the element in
426 :     * the array immediately following the end of the collection is set to
427 : jsr166 1.63 * {@code null}.
428 :     *
429 :     * <p>Like the {@link #toArray()} method, this method acts as bridge between
430 :     * array-based and collection-based APIs. Further, this method allows
431 :     * precise control over the runtime type of the output array, and may,
432 :     * under certain circumstances, be used to save allocation costs.
433 :     *
434 : jsr166 1.80 * <p>Suppose {@code x} is a queue known to contain only strings.
435 : jsr166 1.63 * The following code can be used to dump the queue into a newly
436 : jsr166 1.80 * allocated array of {@code String}:
437 : jsr166 1.63 *
438 : jsr166 1.72 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
439 : jsr166 1.63 *
440 : jsr166 1.80 * Note that {@code toArray(new Object[0])} is identical in function to
441 :     * {@code toArray()}.
442 : dl 1.52 *
443 :     * @param a the array into which the elements of the queue are to
444 :     * be stored, if it is big enough; otherwise, a new array of the
445 :     * same runtime type is allocated for this purpose.
446 : jsr166 1.63 * @return an array containing all of the elements in this queue
447 : dl 1.52 * @throws ArrayStoreException if the runtime type of the specified array
448 :     * is not a supertype of the runtime type of every element in
449 :     * this queue
450 :     * @throws NullPointerException if the specified array is null
451 :     */
452 : jsr166 1.84 @SuppressWarnings("unchecked")
453 : dl 1.52 public <T> T[] toArray(T[] a) {
454 : jsr166 1.85 final int size = this.size;
455 : dl 1.52 if (a.length < size)
456 :     // Make a new array of a's runtime type, but my contents:
457 : dl 1.55 return (T[]) Arrays.copyOf(queue, size, a.getClass());
458 : jsr166 1.68 System.arraycopy(queue, 0, a, 0, size);
459 : dl 1.52 if (a.length > size)
460 :     a[size] = null;
461 :     return a;
462 : tim 1.1 }
463 : tim 1.2
464 : dholmes 1.23 /**
465 :     * Returns an iterator over the elements in this queue. The iterator
466 :     * does not return the elements in any particular order.
467 :     *
468 : dl 1.52 * @return an iterator over the elements in this queue
469 : dholmes 1.23 */
470 : tim 1.2 public Iterator<E> iterator() {
471 : dl 1.7 return new Itr();
472 : tim 1.2 }
473 :    
474 : dl 1.55 private final class Itr implements Iterator<E> {
475 : dl 1.7 /**
476 :     * Index (into queue array) of element to be returned by
477 : tim 1.2 * subsequent call to next.
478 : dl 1.7 */
479 : jsr166 1.99 private int cursor;
480 : tim 1.2
481 : dl 1.7 /**
482 : dl 1.36 * Index of element returned by most recent call to next,
483 :     * unless that element came from the forgetMeNot list.
484 : dl 1.55 * Set to -1 if element is deleted by a call to remove.
485 : dl 1.7 */
486 : dl 1.55 private int lastRet = -1;
487 : dl 1.7
488 :     /**
489 : dl 1.55 * A queue of elements that were moved from the unvisited portion of
490 : dl 1.36 * the heap into the visited portion as a result of "unlucky" element
491 :     * removals during the iteration. (Unlucky element removals are those
492 : dl 1.55 * that require a siftup instead of a siftdown.) We must visit all of
493 : dl 1.36 * the elements in this list to complete the iteration. We do this
494 :     * after we've completed the "normal" iteration.
495 :     *
496 :     * We expect that most iterations, even those involving removals,
497 : jsr166 1.63 * will not need to store elements in this field.
498 : dl 1.36 */
499 : jsr166 1.99 private ArrayDeque<E> forgetMeNot;
500 : dl 1.36
501 :     /**
502 :     * Element returned by the most recent call to next iff that
503 :     * element was drawn from the forgetMeNot list.
504 :     */
505 : jsr166 1.99 private E lastRetElt;
506 : dl 1.55
507 :     /**
508 :     * The modCount value that the iterator believes that the backing
509 : jsr166 1.63 * Queue should have. If this expectation is violated, the iterator
510 : dl 1.55 * has detected concurrent modification.
511 :     */
512 :     private int expectedModCount = modCount;
513 : dl 1.35
514 : dl 1.7 public boolean hasNext() {
515 : jsr166 1.56 return cursor < size ||
516 : dl 1.55 (forgetMeNot != null && !forgetMeNot.isEmpty());
517 : dl 1.7 }
518 :    
519 : dl 1.81 @SuppressWarnings("unchecked")
520 : dl 1.7 public E next() {
521 : dl 1.55 if (expectedModCount != modCount)
522 :     throw new ConcurrentModificationException();
523 : jsr166 1.56 if (cursor < size)
524 : dl 1.55 return (E) queue[lastRet = cursor++];
525 :     if (forgetMeNot != null) {
526 :     lastRet = -1;
527 :     lastRetElt = forgetMeNot.poll();
528 : jsr166 1.56 if (lastRetElt != null)
529 : dl 1.55 return lastRetElt;
530 : dl 1.36 }
531 : dl 1.55 throw new NoSuchElementException();
532 : dl 1.7 }
533 : tim 1.2
534 : dl 1.7 public void remove() {
535 : dl 1.55 if (expectedModCount != modCount)
536 :     throw new ConcurrentModificationException();
537 :     if (lastRet != -1) {
538 : dl 1.36 E moved = PriorityQueue.this.removeAt(lastRet);
539 : dl 1.55 lastRet = -1;
540 : jsr166 1.56 if (moved == null)
541 : dl 1.36 cursor--;
542 : dl 1.55 else {
543 : dl 1.36 if (forgetMeNot == null)
544 : dl 1.89 forgetMeNot = new ArrayDeque<>();
545 : dl 1.36 forgetMeNot.add(moved);
546 : jsr166 1.56 }
547 : jsr166 1.63 } else if (lastRetElt != null) {
548 : dl 1.55 PriorityQueue.this.removeEq(lastRetElt);
549 : dl 1.36 lastRetElt = null;
550 : jsr166 1.63 } else {
551 :     throw new IllegalStateException();
552 : jsr166 1.68 }
553 : tim 1.2 expectedModCount = modCount;
554 : dl 1.7 }
555 : tim 1.2 }
556 :    
557 : tim 1.1 public int size() {
558 : tim 1.2 return size;
559 : tim 1.1 }
560 : tim 1.2
561 :     /**
562 : dl 1.52 * Removes all of the elements from this priority queue.
563 : dl 1.49 * The queue will be empty after this call returns.
564 : tim 1.2 */
565 :     public void clear() {
566 :     modCount++;
567 : dl 1.55 for (int i = 0; i < size; i++)
568 : tim 1.2 queue[i] = null;
569 :     size = 0;
570 :     }
571 :    
572 : dl 1.81 @SuppressWarnings("unchecked")
573 : dl 1.40 public E poll() {
574 : dl 1.36 if (size == 0)
575 : dl 1.40 return null;
576 : dl 1.55 int s = --size;
577 : dl 1.36 modCount++;
578 : jsr166 1.63 E result = (E) queue[0];
579 :     E x = (E) queue[s];
580 : dl 1.55 queue[s] = null;
581 :     if (s != 0)
582 :     siftDown(0, x);
583 : dl 1.36 return result;
584 :     }
585 :    
586 :     /**
587 : dl 1.55 * Removes the ith element from queue.
588 : tim 1.2 *
589 : dl 1.55 * Normally this method leaves the elements at up to i-1,
590 :     * inclusive, untouched. Under these circumstances, it returns
591 :     * null. Occasionally, in order to maintain the heap invariant,
592 :     * it must swap a later element of the list with one earlier than
593 :     * i. Under these circumstances, this method returns the element
594 :     * that was previously at the end of the list and is now at some
595 :     * position before i. This fact is used by iterator.remove so as to
596 : jsr166 1.63 * avoid missing traversing elements.
597 : tim 1.2 */
598 : dl 1.81 @SuppressWarnings("unchecked")
599 : dl 1.52 private E removeAt(int i) {
600 : jsr166 1.74 // assert i >= 0 && i < size;
601 : tim 1.2 modCount++;
602 : dl 1.55 int s = --size;
603 :     if (s == i) // removed last element
604 :     queue[i] = null;
605 :     else {
606 :     E moved = (E) queue[s];
607 : jsr166 1.56 queue[s] = null;
608 : dl 1.55 siftDown(i, moved);
609 : dl 1.36 if (queue[i] == moved) {
610 : dl 1.55 siftUp(i, moved);
611 : dl 1.36 if (queue[i] != moved)
612 :     return moved;
613 :     }
614 : dl 1.35 }
615 : dl 1.36 return null;
616 : tim 1.1 }
617 :    
618 : tim 1.2 /**
619 : dl 1.55 * Inserts item x at position k, maintaining heap invariant by
620 :     * promoting x up the tree until it is greater than or equal to
621 :     * its parent, or is the root.
622 :     *
623 :     * To simplify and speed up coercions and comparisons. the
624 :     * Comparable and Comparator versions are separated into different
625 :     * methods that are otherwise identical. (Similarly for siftDown.)
626 : jsr166 1.56 *
627 : dl 1.55 * @param k the position to fill
628 :     * @param x the item to insert
629 :     */
630 :     private void siftUp(int k, E x) {
631 : jsr166 1.56 if (comparator != null)
632 : dl 1.55 siftUpUsingComparator(k, x);
633 :     else
634 :     siftUpComparable(k, x);
635 :     }
636 :    
637 : dl 1.81 @SuppressWarnings("unchecked")
638 : dl 1.55 private void siftUpComparable(int k, E x) {
639 :     Comparable<? super E> key = (Comparable<? super E>) x;
640 :     while (k > 0) {
641 :     int parent = (k - 1) >>> 1;
642 :     Object e = queue[parent];
643 : jsr166 1.63 if (key.compareTo((E) e) >= 0)
644 : dl 1.55 break;
645 :     queue[k] = e;
646 :     k = parent;
647 :     }
648 :     queue[k] = key;
649 :     }
650 :    
651 : dl 1.81 @SuppressWarnings("unchecked")
652 : dl 1.55 private void siftUpUsingComparator(int k, E x) {
653 :     while (k > 0) {
654 :     int parent = (k - 1) >>> 1;
655 :     Object e = queue[parent];
656 : jsr166 1.63 if (comparator.compare(x, (E) e) >= 0)
657 : dl 1.55 break;
658 :     queue[k] = e;
659 :     k = parent;
660 :     }
661 :     queue[k] = x;
662 :     }
663 :    
664 :     /**
665 :     * Inserts item x at position k, maintaining heap invariant by
666 :     * demoting x down the tree repeatedly until it is less than or
667 :     * equal to its children or is a leaf.
668 :     *
669 :     * @param k the position to fill
670 :     * @param x the item to insert
671 :     */
672 :     private void siftDown(int k, E x) {
673 : jsr166 1.56 if (comparator != null)
674 : dl 1.55 siftDownUsingComparator(k, x);
675 :     else
676 :     siftDownComparable(k, x);
677 :     }
678 :    
679 : dl 1.81 @SuppressWarnings("unchecked")
680 : dl 1.55 private void siftDownComparable(int k, E x) {
681 :     Comparable<? super E> key = (Comparable<? super E>)x;
682 :     int half = size >>> 1; // loop while a non-leaf
683 :     while (k < half) {
684 :     int child = (k << 1) + 1; // assume left child is least
685 :     Object c = queue[child];
686 :     int right = child + 1;
687 :     if (right < size &&
688 : jsr166 1.63 ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
689 : dl 1.55 c = queue[child = right];
690 : jsr166 1.63 if (key.compareTo((E) c) <= 0)
691 : dl 1.55 break;
692 :     queue[k] = c;
693 :     k = child;
694 :     }
695 :     queue[k] = key;
696 :     }
697 :    
698 : dl 1.81 @SuppressWarnings("unchecked")
699 : dl 1.55 private void siftDownUsingComparator(int k, E x) {
700 :     int half = size >>> 1;
701 :     while (k < half) {
702 :     int child = (k << 1) + 1;
703 :     Object c = queue[child];
704 :     int right = child + 1;
705 :     if (right < size &&
706 : jsr166 1.63 comparator.compare((E) c, (E) queue[right]) > 0)
707 : jsr166 1.56 c = queue[child = right];
708 : jsr166 1.63 if (comparator.compare(x, (E) c) <= 0)
709 : dl 1.55 break;
710 :     queue[k] = c;
711 :     k = child;
712 : tim 1.2 }
713 : dl 1.55 queue[k] = x;
714 : dl 1.36 }
715 : dl 1.35
716 : dl 1.36 /**
717 :     * Establishes the heap invariant (described above) in the entire tree,
718 :     * assuming nothing about the order of the elements prior to the call.
719 :     */
720 : dl 1.81 @SuppressWarnings("unchecked")
721 : dl 1.36 private void heapify() {
722 : jsr166 1.56 for (int i = (size >>> 1) - 1; i >= 0; i--)
723 : jsr166 1.63 siftDown(i, (E) queue[i]);
724 : tim 1.2 }
725 :    
726 : dholmes 1.23 /**
727 : dl 1.52 * Returns the comparator used to order the elements in this
728 : jsr166 1.63 * queue, or {@code null} if this queue is sorted according to
729 : dl 1.52 * the {@linkplain Comparable natural ordering} of its elements.
730 :     *
731 :     * @return the comparator used to order this queue, or
732 : jsr166 1.63 * {@code null} if this queue is sorted according to the
733 :     * natural ordering of its elements
734 : dholmes 1.23 */
735 : tim 1.16 public Comparator<? super E> comparator() {
736 : tim 1.2 return comparator;
737 :     }
738 : dl 1.5
739 :     /**
740 : jsr166 1.77 * Saves this queue to a stream (that is, serializes it).
741 : dl 1.5 *
742 :     * @serialData The length of the array backing the instance is
743 : jsr166 1.63 * emitted (int), followed by all of its elements
744 :     * (each an {@code Object}) in the proper order.
745 : dl 1.81 * @param s the stream
746 : jsr166 1.97 * @throws java.io.IOException if an I/O error occurs
747 : dl 1.5 */
748 : dl 1.22 private void writeObject(java.io.ObjectOutputStream s)
749 : jsr166 1.75 throws java.io.IOException {
750 : dl 1.7 // Write out element count, and any hidden stuff
751 :     s.defaultWriteObject();
752 : dl 1.5
753 : jsr166 1.63 // Write out array length, for compatibility with 1.5 version
754 :     s.writeInt(Math.max(2, size + 1));
755 : dl 1.5
756 : jsr166 1.64 // Write out all elements in the "proper order".
757 : jsr166 1.63 for (int i = 0; i < size; i++)
758 : dl 1.5 s.writeObject(queue[i]);
759 :     }
760 :    
761 :     /**
762 : dl 1.81 * Reconstitutes the {@code PriorityQueue} instance from a stream
763 :     * (that is, deserializes it).
764 :     *
765 :     * @param s the stream
766 : jsr166 1.97 * @throws ClassNotFoundException if the class of a serialized object
767 :     * could not be found
768 :     * @throws java.io.IOException if an I/O error occurs
769 : dl 1.5 */
770 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
771 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
772 : dl 1.7 // Read in size, and any hidden stuff
773 :     s.defaultReadObject();
774 : dl 1.5
775 : jsr166 1.63 // Read in (and discard) array length
776 :     s.readInt();
777 :    
778 : jsr166 1.68 queue = new Object[size];
779 : dl 1.5
780 : jsr166 1.64 // Read in all elements.
781 : jsr166 1.63 for (int i = 0; i < size; i++)
782 :     queue[i] = s.readObject();
783 : jsr166 1.64
784 : jsr166 1.68 // Elements are guaranteed to be in "proper order", but the
785 :     // spec has never explained what that might be.
786 :     heapify();
787 : dl 1.5 }
788 : dl 1.81
789 : dl 1.94 public Spliterator<E> spliterator() {
790 : dl 1.89 return new PriorityQueueSpliterator<E>(this, 0, -1, 0);
791 : dl 1.81 }
792 :    
793 : jsr166 1.93 /**
794 :     * This is very similar to ArrayList Spliterator, except for extra
795 :     * null checks.
796 :     */
797 : dl 1.86 static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
798 : dl 1.81 private final PriorityQueue<E> pq;
799 : dl 1.89 private int index; // current index, modified on advance/split
800 :     private int fence; // -1 until first use
801 :     private int expectedModCount; // initialized when fence set
802 : dl 1.81
803 : jsr166 1.92 /** Creates new spliterator covering the given range */
804 : dl 1.81 PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
805 :     int expectedModCount) {
806 : dl 1.89 this.pq = pq;
807 :     this.index = origin;
808 :     this.fence = fence;
809 : dl 1.81 this.expectedModCount = expectedModCount;
810 :     }
811 :    
812 : dl 1.89 private int getFence() { // initialize fence to size on first use
813 :     int hi;
814 :     if ((hi = fence) < 0) {
815 :     expectedModCount = pq.modCount;
816 :     hi = fence = pq.size;
817 :     }
818 :     return hi;
819 :     }
820 : jsr166 1.90
821 : dl 1.94 public Spliterator<E> trySplit() {
822 : dl 1.89 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
823 : dl 1.81 return (lo >= mid) ? null :
824 : jsr166 1.90 new PriorityQueueSpliterator<E>(pq, lo, index = mid,
825 : dl 1.86 expectedModCount);
826 : dl 1.81 }
827 :    
828 : dl 1.89 @SuppressWarnings("unchecked")
829 : dl 1.95 public void forEachRemaining(Consumer<? super E> action) {
830 : dl 1.89 int i, hi, mc; // hoist accesses and checks from loop
831 :     PriorityQueue<E> q; Object[] a;
832 :     if (action == null)
833 : dl 1.81 throw new NullPointerException();
834 : dl 1.89 if ((q = pq) != null && (a = q.queue) != null) {
835 :     if ((hi = fence) < 0) {
836 :     mc = q.modCount;
837 :     hi = q.size;
838 :     }
839 :     else
840 :     mc = expectedModCount;
841 :     if ((i = index) >= 0 && (index = hi) <= a.length) {
842 :     for (E e;; ++i) {
843 :     if (i < hi) {
844 :     if ((e = (E) a[i]) == null) // must be CME
845 :     break;
846 :     action.accept(e);
847 :     }
848 :     else if (q.modCount != mc)
849 :     break;
850 :     else
851 :     return;
852 :     }
853 :     }
854 : dl 1.81 }
855 : dl 1.89 throw new ConcurrentModificationException();
856 : dl 1.81 }
857 :    
858 : dl 1.89 public boolean tryAdvance(Consumer<? super E> action) {
859 :     int hi = getFence(), lo = index;
860 :     if (lo >= 0 && lo < hi) {
861 :     index = lo + 1;
862 :     @SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
863 :     if (e == null)
864 :     throw new ConcurrentModificationException();
865 :     action.accept(e);
866 : dl 1.86 if (pq.modCount != expectedModCount)
867 :     throw new ConcurrentModificationException();
868 : dl 1.81 return true;
869 :     }
870 :     return false;
871 :     }
872 :    
873 : jsr166 1.90 public long estimateSize() {
874 :     return (long) (getFence() - index);
875 : dl 1.89 }
876 :    
877 :     public int characteristics() {
878 :     return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
879 :     }
880 : dl 1.81 }
881 : tim 1.1 }

Doug Lea
ViewVC Help
Powered by ViewVC 1.0.8