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1 : dl 1.38 /*
2 : jsr166 1.106 * Copyright (c) 2003, 2013, 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 : jsr166 1.102
28 : dl 1.89 import java.util.function.Consumer;
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 : jsr166 1.101 * @param <E> the type of elements held in this queue
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 1.107 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 : jsr166 1.106 transient int modCount; // 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 1.106 * Creates a {@code PriorityQueue} with the default initial capacity and
140 :     * whose elements are ordered according to the specified comparator.
141 :     *
142 :     * @param comparator the comparator that will be used to order this
143 :     * priority queue. If {@code null}, the {@linkplain Comparable
144 :     * natural ordering} of the elements will be used.
145 :     * @since 1.8
146 :     */
147 :     public PriorityQueue(Comparator<? super E> comparator) {
148 :     this(DEFAULT_INITIAL_CAPACITY, comparator);
149 :     }
150 :    
151 :     /**
152 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial capacity
153 : tim 1.2 * that orders its elements according to the specified comparator.
154 :     *
155 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
156 : jsr166 1.63 * @param comparator the comparator that will be used to order this
157 :     * priority queue. If {@code null}, the {@linkplain Comparable
158 :     * natural ordering} of the elements will be used.
159 :     * @throws IllegalArgumentException if {@code initialCapacity} is
160 : dl 1.52 * less than 1
161 : tim 1.2 */
162 : dl 1.52 public PriorityQueue(int initialCapacity,
163 : dholmes 1.23 Comparator<? super E> comparator) {
164 : dl 1.55 // Note: This restriction of at least one is not actually needed,
165 :     // but continues for 1.5 compatibility
166 : tim 1.2 if (initialCapacity < 1)
167 : dholmes 1.15 throw new IllegalArgumentException();
168 : dl 1.55 this.queue = new Object[initialCapacity];
169 : tim 1.2 this.comparator = comparator;
170 : tim 1.1 }
171 : jsr166 1.56
172 : dl 1.22 /**
173 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
174 :     * specified collection. If the specified collection is an instance of
175 :     * a {@link SortedSet} or is another {@code PriorityQueue}, this
176 :     * priority queue will be ordered according to the same ordering.
177 :     * Otherwise, this priority queue will be ordered according to the
178 :     * {@linkplain Comparable natural ordering} of its elements.
179 : tim 1.2 *
180 : dl 1.52 * @param c the collection whose elements are to be placed
181 :     * into this priority queue
182 : tim 1.2 * @throws ClassCastException if elements of the specified collection
183 :     * cannot be compared to one another according to the priority
184 : dl 1.52 * queue's ordering
185 :     * @throws NullPointerException if the specified collection or any
186 :     * of its elements are null
187 : tim 1.2 */
188 : jsr166 1.70 @SuppressWarnings("unchecked")
189 : tim 1.16 public PriorityQueue(Collection<? extends E> c) {
190 : jsr166 1.70 if (c instanceof SortedSet<?>) {
191 :     SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
192 :     this.comparator = (Comparator<? super E>) ss.comparator();
193 :     initElementsFromCollection(ss);
194 :     }
195 :     else if (c instanceof PriorityQueue<?>) {
196 :     PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
197 :     this.comparator = (Comparator<? super E>) pq.comparator();
198 :     initFromPriorityQueue(pq);
199 :     }
200 : dl 1.55 else {
201 : jsr166 1.70 this.comparator = null;
202 :     initFromCollection(c);
203 : tim 1.2 }
204 : dl 1.22 }
205 :    
206 :     /**
207 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
208 : dl 1.55 * specified priority queue. This priority queue will be
209 : dl 1.52 * ordered according to the same ordering as the given priority
210 :     * queue.
211 :     *
212 :     * @param c the priority queue whose elements are to be placed
213 :     * into this priority queue
214 : jsr166 1.63 * @throws ClassCastException if elements of {@code c} cannot be
215 :     * compared to one another according to {@code c}'s
216 : dl 1.52 * ordering
217 :     * @throws NullPointerException if the specified priority queue or any
218 :     * of its elements are null
219 : dl 1.22 */
220 : jsr166 1.70 @SuppressWarnings("unchecked")
221 : dl 1.22 public PriorityQueue(PriorityQueue<? extends E> c) {
222 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
223 :     initFromPriorityQueue(c);
224 : dl 1.22 }
225 : dholmes 1.18
226 : dl 1.22 /**
227 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
228 :     * specified sorted set. This priority queue will be ordered
229 : dl 1.52 * according to the same ordering as the given sorted set.
230 :     *
231 :     * @param c the sorted set whose elements are to be placed
232 : jsr166 1.63 * into this priority queue
233 : dl 1.52 * @throws ClassCastException if elements of the specified sorted
234 :     * set cannot be compared to one another according to the
235 :     * sorted set's ordering
236 :     * @throws NullPointerException if the specified sorted set or any
237 :     * of its elements are null
238 : dl 1.22 */
239 : jsr166 1.70 @SuppressWarnings("unchecked")
240 : dl 1.22 public PriorityQueue(SortedSet<? extends E> c) {
241 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
242 :     initElementsFromCollection(c);
243 :     }
244 :    
245 :     private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
246 :     if (c.getClass() == PriorityQueue.class) {
247 :     this.queue = c.toArray();
248 :     this.size = c.size();
249 :     } else {
250 :     initFromCollection(c);
251 :     }
252 :     }
253 :    
254 :     private void initElementsFromCollection(Collection<? extends E> c) {
255 :     Object[] a = c.toArray();
256 :     // If c.toArray incorrectly doesn't return Object[], copy it.
257 :     if (a.getClass() != Object[].class)
258 :     a = Arrays.copyOf(a, a.length, Object[].class);
259 :     int len = a.length;
260 :     if (len == 1 || this.comparator != null)
261 : jsr166 1.106 for (Object e : a)
262 :     if (e == null)
263 : jsr166 1.70 throw new NullPointerException();
264 :     this.queue = a;
265 :     this.size = a.length;
266 : tim 1.1 }
267 :    
268 : dl 1.22 /**
269 : jsr166 1.63 * Initializes queue array with elements from the given Collection.
270 :     *
271 : dl 1.55 * @param c the collection
272 : dl 1.22 */
273 : dl 1.55 private void initFromCollection(Collection<? extends E> c) {
274 : jsr166 1.70 initElementsFromCollection(c);
275 :     heapify();
276 : jsr166 1.56 }
277 : dl 1.55
278 :     /**
279 : jsr166 1.70 * The maximum size of array to allocate.
280 :     * Some VMs reserve some header words in an array.
281 :     * Attempts to allocate larger arrays may result in
282 :     * OutOfMemoryError: Requested array size exceeds VM limit
283 :     */
284 :     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
285 :    
286 :     /**
287 : dl 1.55 * Increases the capacity of the array.
288 :     *
289 :     * @param minCapacity the desired minimum capacity
290 :     */
291 :     private void grow(int minCapacity) {
292 : jsr166 1.68 int oldCapacity = queue.length;
293 : dl 1.55 // Double size if small; else grow by 50%
294 : jsr166 1.70 int newCapacity = oldCapacity + ((oldCapacity < 64) ?
295 :     (oldCapacity + 2) :
296 :     (oldCapacity >> 1));
297 :     // overflow-conscious code
298 :     if (newCapacity - MAX_ARRAY_SIZE > 0)
299 :     newCapacity = hugeCapacity(minCapacity);
300 : dl 1.55 queue = Arrays.copyOf(queue, newCapacity);
301 : dl 1.22 }
302 : dl 1.36
303 : jsr166 1.70 private static int hugeCapacity(int minCapacity) {
304 :     if (minCapacity < 0) // overflow
305 :     throw new OutOfMemoryError();
306 :     return (minCapacity > MAX_ARRAY_SIZE) ?
307 :     Integer.MAX_VALUE :
308 :     MAX_ARRAY_SIZE;
309 :     }
310 :    
311 : tim 1.2 /**
312 : dl 1.42 * Inserts the specified element into this priority queue.
313 : tim 1.2 *
314 : jsr166 1.63 * @return {@code true} (as specified by {@link Collection#add})
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 : tim 1.2 */
320 : dl 1.52 public boolean add(E e) {
321 :     return offer(e);
322 :     }
323 :    
324 :     /**
325 :     * Inserts the specified element into this priority queue.
326 :     *
327 : jsr166 1.63 * @return {@code true} (as specified by {@link Queue#offer})
328 : dl 1.52 * @throws ClassCastException if the specified element cannot be
329 :     * compared with elements currently in this priority queue
330 :     * according to the priority queue's ordering
331 :     * @throws NullPointerException if the specified element is null
332 :     */
333 :     public boolean offer(E e) {
334 :     if (e == null)
335 : dholmes 1.11 throw new NullPointerException();
336 :     modCount++;
337 : dl 1.55 int i = size;
338 :     if (i >= queue.length)
339 :     grow(i + 1);
340 :     size = i + 1;
341 :     if (i == 0)
342 :     queue[0] = e;
343 :     else
344 :     siftUp(i, e);
345 : dholmes 1.11 return true;
346 :     }
347 :    
348 : dl 1.81 @SuppressWarnings("unchecked")
349 : dl 1.40 public E peek() {
350 : jsr166 1.73 return (size == 0) ? null : (E) queue[0];
351 : tim 1.1 }
352 :    
353 : dl 1.52 private int indexOf(Object o) {
354 : jsr166 1.68 if (o != null) {
355 : dl 1.55 for (int i = 0; i < size; i++)
356 :     if (o.equals(queue[i]))
357 :     return i;
358 :     }
359 : dl 1.52 return -1;
360 :     }
361 :    
362 :     /**
363 :     * Removes a single instance of the specified element from this queue,
364 : jsr166 1.63 * if it is present. More formally, removes an element {@code e} such
365 :     * that {@code o.equals(e)}, if this queue contains one or more such
366 :     * elements. Returns {@code true} if and only if this queue contained
367 :     * the specified element (or equivalently, if this queue changed as a
368 :     * result of the call).
369 : dl 1.52 *
370 :     * @param o element to be removed from this queue, if present
371 : jsr166 1.63 * @return {@code true} if this queue changed as a result of the call
372 : dl 1.52 */
373 :     public boolean remove(Object o) {
374 : jsr166 1.68 int i = indexOf(o);
375 :     if (i == -1)
376 :     return false;
377 :     else {
378 :     removeAt(i);
379 :     return true;
380 :     }
381 : dl 1.52 }
382 : dholmes 1.11
383 : jsr166 1.56 /**
384 : dl 1.55 * Version of remove using reference equality, not equals.
385 : jsr166 1.59 * Needed by iterator.remove.
386 : jsr166 1.56 *
387 : dl 1.55 * @param o element to be removed from this queue, if present
388 : jsr166 1.63 * @return {@code true} if removed
389 : dl 1.55 */
390 :     boolean removeEq(Object o) {
391 : jsr166 1.68 for (int i = 0; i < size; i++) {
392 :     if (o == queue[i]) {
393 : dl 1.55 removeAt(i);
394 :     return true;
395 :     }
396 :     }
397 :     return false;
398 :     }
399 :    
400 : dholmes 1.11 /**
401 : jsr166 1.63 * Returns {@code true} if this queue contains the specified element.
402 :     * More formally, returns {@code true} if and only if this queue contains
403 :     * at least one element {@code e} such that {@code o.equals(e)}.
404 : dholmes 1.23 *
405 : dl 1.52 * @param o object to be checked for containment in this queue
406 : jsr166 1.63 * @return {@code true} if this queue contains the specified element
407 : dholmes 1.11 */
408 : dl 1.52 public boolean contains(Object o) {
409 : jsr166 1.100 return indexOf(o) >= 0;
410 : tim 1.14 }
411 : dholmes 1.11
412 : dl 1.49 /**
413 : jsr166 1.63 * Returns an array containing all of the elements in this queue.
414 : dl 1.52 * The elements are in no particular order.
415 :     *
416 :     * <p>The returned array will be "safe" in that no references to it are
417 : jsr166 1.63 * maintained by this queue. (In other words, this method must allocate
418 : dl 1.52 * a new array). The caller is thus free to modify the returned array.
419 :     *
420 : jsr166 1.63 * <p>This method acts as bridge between array-based and collection-based
421 :     * APIs.
422 :     *
423 : jsr166 1.59 * @return an array containing all of the elements in this queue
424 : dl 1.49 */
425 : dl 1.52 public Object[] toArray() {
426 : dl 1.55 return Arrays.copyOf(queue, size);
427 : dl 1.52 }
428 : tim 1.2
429 : dl 1.52 /**
430 : jsr166 1.63 * Returns an array containing all of the elements in this queue; the
431 :     * runtime type of the returned array is that of the specified array.
432 :     * The returned array elements are in no particular order.
433 :     * If the queue fits in the specified array, it is returned therein.
434 :     * Otherwise, a new array is allocated with the runtime type of the
435 :     * specified array and the size of this queue.
436 : dl 1.52 *
437 :     * <p>If the queue fits in the specified array with room to spare
438 :     * (i.e., the array has more elements than the queue), the element in
439 :     * the array immediately following the end of the collection is set to
440 : jsr166 1.63 * {@code null}.
441 :     *
442 :     * <p>Like the {@link #toArray()} method, this method acts as bridge between
443 :     * array-based and collection-based APIs. Further, this method allows
444 :     * precise control over the runtime type of the output array, and may,
445 :     * under certain circumstances, be used to save allocation costs.
446 :     *
447 : jsr166 1.80 * <p>Suppose {@code x} is a queue known to contain only strings.
448 : jsr166 1.63 * The following code can be used to dump the queue into a newly
449 : jsr166 1.80 * allocated array of {@code String}:
450 : jsr166 1.63 *
451 : jsr166 1.104 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
452 : jsr166 1.63 *
453 : jsr166 1.80 * Note that {@code toArray(new Object[0])} is identical in function to
454 :     * {@code toArray()}.
455 : dl 1.52 *
456 :     * @param a the array into which the elements of the queue are to
457 :     * be stored, if it is big enough; otherwise, a new array of the
458 :     * same runtime type is allocated for this purpose.
459 : jsr166 1.63 * @return an array containing all of the elements in this queue
460 : dl 1.52 * @throws ArrayStoreException if the runtime type of the specified array
461 :     * is not a supertype of the runtime type of every element in
462 :     * this queue
463 :     * @throws NullPointerException if the specified array is null
464 :     */
465 : jsr166 1.84 @SuppressWarnings("unchecked")
466 : dl 1.52 public <T> T[] toArray(T[] a) {
467 : jsr166 1.85 final int size = this.size;
468 : dl 1.52 if (a.length < size)
469 :     // Make a new array of a's runtime type, but my contents:
470 : dl 1.55 return (T[]) Arrays.copyOf(queue, size, a.getClass());
471 : jsr166 1.68 System.arraycopy(queue, 0, a, 0, size);
472 : dl 1.52 if (a.length > size)
473 :     a[size] = null;
474 :     return a;
475 : tim 1.1 }
476 : tim 1.2
477 : dholmes 1.23 /**
478 :     * Returns an iterator over the elements in this queue. The iterator
479 :     * does not return the elements in any particular order.
480 :     *
481 : dl 1.52 * @return an iterator over the elements in this queue
482 : dholmes 1.23 */
483 : tim 1.2 public Iterator<E> iterator() {
484 : dl 1.7 return new Itr();
485 : tim 1.2 }
486 :    
487 : dl 1.55 private final class Itr implements Iterator<E> {
488 : dl 1.7 /**
489 :     * Index (into queue array) of element to be returned by
490 : tim 1.2 * subsequent call to next.
491 : dl 1.7 */
492 : jsr166 1.99 private int cursor;
493 : tim 1.2
494 : dl 1.7 /**
495 : dl 1.36 * Index of element returned by most recent call to next,
496 :     * unless that element came from the forgetMeNot list.
497 : dl 1.55 * Set to -1 if element is deleted by a call to remove.
498 : dl 1.7 */
499 : dl 1.55 private int lastRet = -1;
500 : dl 1.7
501 :     /**
502 : dl 1.55 * A queue of elements that were moved from the unvisited portion of
503 : dl 1.36 * the heap into the visited portion as a result of "unlucky" element
504 :     * removals during the iteration. (Unlucky element removals are those
505 : dl 1.55 * that require a siftup instead of a siftdown.) We must visit all of
506 : dl 1.36 * the elements in this list to complete the iteration. We do this
507 :     * after we've completed the "normal" iteration.
508 :     *
509 :     * We expect that most iterations, even those involving removals,
510 : jsr166 1.63 * will not need to store elements in this field.
511 : dl 1.36 */
512 : jsr166 1.99 private ArrayDeque<E> forgetMeNot;
513 : dl 1.36
514 :     /**
515 :     * Element returned by the most recent call to next iff that
516 :     * element was drawn from the forgetMeNot list.
517 :     */
518 : jsr166 1.99 private E lastRetElt;
519 : dl 1.55
520 :     /**
521 :     * The modCount value that the iterator believes that the backing
522 : jsr166 1.63 * Queue should have. If this expectation is violated, the iterator
523 : dl 1.55 * has detected concurrent modification.
524 :     */
525 :     private int expectedModCount = modCount;
526 : dl 1.35
527 : dl 1.7 public boolean hasNext() {
528 : jsr166 1.56 return cursor < size ||
529 : dl 1.55 (forgetMeNot != null && !forgetMeNot.isEmpty());
530 : dl 1.7 }
531 :    
532 : dl 1.81 @SuppressWarnings("unchecked")
533 : dl 1.7 public E next() {
534 : dl 1.55 if (expectedModCount != modCount)
535 :     throw new ConcurrentModificationException();
536 : jsr166 1.56 if (cursor < size)
537 : dl 1.55 return (E) queue[lastRet = cursor++];
538 :     if (forgetMeNot != null) {
539 :     lastRet = -1;
540 :     lastRetElt = forgetMeNot.poll();
541 : jsr166 1.56 if (lastRetElt != null)
542 : dl 1.55 return lastRetElt;
543 : dl 1.36 }
544 : dl 1.55 throw new NoSuchElementException();
545 : dl 1.7 }
546 : tim 1.2
547 : dl 1.7 public void remove() {
548 : dl 1.55 if (expectedModCount != modCount)
549 :     throw new ConcurrentModificationException();
550 :     if (lastRet != -1) {
551 : dl 1.36 E moved = PriorityQueue.this.removeAt(lastRet);
552 : dl 1.55 lastRet = -1;
553 : jsr166 1.56 if (moved == null)
554 : dl 1.36 cursor--;
555 : dl 1.55 else {
556 : dl 1.36 if (forgetMeNot == null)
557 : dl 1.89 forgetMeNot = new ArrayDeque<>();
558 : dl 1.36 forgetMeNot.add(moved);
559 : jsr166 1.56 }
560 : jsr166 1.63 } else if (lastRetElt != null) {
561 : dl 1.55 PriorityQueue.this.removeEq(lastRetElt);
562 : dl 1.36 lastRetElt = null;
563 : jsr166 1.63 } else {
564 :     throw new IllegalStateException();
565 : jsr166 1.68 }
566 : tim 1.2 expectedModCount = modCount;
567 : dl 1.7 }
568 : tim 1.2 }
569 :    
570 : tim 1.1 public int size() {
571 : tim 1.2 return size;
572 : tim 1.1 }
573 : tim 1.2
574 :     /**
575 : dl 1.52 * Removes all of the elements from this priority queue.
576 : dl 1.49 * The queue will be empty after this call returns.
577 : tim 1.2 */
578 :     public void clear() {
579 :     modCount++;
580 : dl 1.55 for (int i = 0; i < size; i++)
581 : tim 1.2 queue[i] = null;
582 :     size = 0;
583 :     }
584 :    
585 : dl 1.81 @SuppressWarnings("unchecked")
586 : dl 1.40 public E poll() {
587 : dl 1.36 if (size == 0)
588 : dl 1.40 return null;
589 : dl 1.55 int s = --size;
590 : dl 1.36 modCount++;
591 : jsr166 1.63 E result = (E) queue[0];
592 :     E x = (E) queue[s];
593 : dl 1.55 queue[s] = null;
594 :     if (s != 0)
595 :     siftDown(0, x);
596 : dl 1.36 return result;
597 :     }
598 :    
599 :     /**
600 : dl 1.55 * Removes the ith element from queue.
601 : tim 1.2 *
602 : dl 1.55 * Normally this method leaves the elements at up to i-1,
603 :     * inclusive, untouched. Under these circumstances, it returns
604 :     * null. Occasionally, in order to maintain the heap invariant,
605 :     * it must swap a later element of the list with one earlier than
606 :     * i. Under these circumstances, this method returns the element
607 :     * that was previously at the end of the list and is now at some
608 :     * position before i. This fact is used by iterator.remove so as to
609 : jsr166 1.63 * avoid missing traversing elements.
610 : tim 1.2 */
611 : dl 1.81 @SuppressWarnings("unchecked")
612 : jsr166 1.107 E removeAt(int i) {
613 : jsr166 1.74 // assert i >= 0 && i < size;
614 : tim 1.2 modCount++;
615 : dl 1.55 int s = --size;
616 :     if (s == i) // removed last element
617 :     queue[i] = null;
618 :     else {
619 :     E moved = (E) queue[s];
620 : jsr166 1.56 queue[s] = null;
621 : dl 1.55 siftDown(i, moved);
622 : dl 1.36 if (queue[i] == moved) {
623 : dl 1.55 siftUp(i, moved);
624 : dl 1.36 if (queue[i] != moved)
625 :     return moved;
626 :     }
627 : dl 1.35 }
628 : dl 1.36 return null;
629 : tim 1.1 }
630 :    
631 : tim 1.2 /**
632 : dl 1.55 * Inserts item x at position k, maintaining heap invariant by
633 :     * promoting x up the tree until it is greater than or equal to
634 :     * its parent, or is the root.
635 :     *
636 :     * To simplify and speed up coercions and comparisons. the
637 :     * Comparable and Comparator versions are separated into different
638 :     * methods that are otherwise identical. (Similarly for siftDown.)
639 : jsr166 1.56 *
640 : dl 1.55 * @param k the position to fill
641 :     * @param x the item to insert
642 :     */
643 :     private void siftUp(int k, E x) {
644 : jsr166 1.56 if (comparator != null)
645 : dl 1.55 siftUpUsingComparator(k, x);
646 :     else
647 :     siftUpComparable(k, x);
648 :     }
649 :    
650 : dl 1.81 @SuppressWarnings("unchecked")
651 : dl 1.55 private void siftUpComparable(int k, E x) {
652 :     Comparable<? super E> key = (Comparable<? super E>) x;
653 :     while (k > 0) {
654 :     int parent = (k - 1) >>> 1;
655 :     Object e = queue[parent];
656 : jsr166 1.63 if (key.compareTo((E) e) >= 0)
657 : dl 1.55 break;
658 :     queue[k] = e;
659 :     k = parent;
660 :     }
661 :     queue[k] = key;
662 :     }
663 :    
664 : dl 1.81 @SuppressWarnings("unchecked")
665 : dl 1.55 private void siftUpUsingComparator(int k, E x) {
666 :     while (k > 0) {
667 :     int parent = (k - 1) >>> 1;
668 :     Object e = queue[parent];
669 : jsr166 1.63 if (comparator.compare(x, (E) e) >= 0)
670 : dl 1.55 break;
671 :     queue[k] = e;
672 :     k = parent;
673 :     }
674 :     queue[k] = x;
675 :     }
676 :    
677 :     /**
678 :     * Inserts item x at position k, maintaining heap invariant by
679 :     * demoting x down the tree repeatedly until it is less than or
680 :     * equal to its children or is a leaf.
681 :     *
682 :     * @param k the position to fill
683 :     * @param x the item to insert
684 :     */
685 :     private void siftDown(int k, E x) {
686 : jsr166 1.56 if (comparator != null)
687 : dl 1.55 siftDownUsingComparator(k, x);
688 :     else
689 :     siftDownComparable(k, x);
690 :     }
691 :    
692 : dl 1.81 @SuppressWarnings("unchecked")
693 : dl 1.55 private void siftDownComparable(int k, E x) {
694 :     Comparable<? super E> key = (Comparable<? super E>)x;
695 :     int half = size >>> 1; // loop while a non-leaf
696 :     while (k < half) {
697 :     int child = (k << 1) + 1; // assume left child is least
698 :     Object c = queue[child];
699 :     int right = child + 1;
700 :     if (right < size &&
701 : jsr166 1.63 ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
702 : dl 1.55 c = queue[child = right];
703 : jsr166 1.63 if (key.compareTo((E) c) <= 0)
704 : dl 1.55 break;
705 :     queue[k] = c;
706 :     k = child;
707 :     }
708 :     queue[k] = key;
709 :     }
710 :    
711 : dl 1.81 @SuppressWarnings("unchecked")
712 : dl 1.55 private void siftDownUsingComparator(int k, E x) {
713 :     int half = size >>> 1;
714 :     while (k < half) {
715 :     int child = (k << 1) + 1;
716 :     Object c = queue[child];
717 :     int right = child + 1;
718 :     if (right < size &&
719 : jsr166 1.63 comparator.compare((E) c, (E) queue[right]) > 0)
720 : jsr166 1.56 c = queue[child = right];
721 : jsr166 1.63 if (comparator.compare(x, (E) c) <= 0)
722 : dl 1.55 break;
723 :     queue[k] = c;
724 :     k = child;
725 : tim 1.2 }
726 : dl 1.55 queue[k] = x;
727 : dl 1.36 }
728 : dl 1.35
729 : dl 1.36 /**
730 :     * Establishes the heap invariant (described above) in the entire tree,
731 :     * assuming nothing about the order of the elements prior to the call.
732 :     */
733 : dl 1.81 @SuppressWarnings("unchecked")
734 : dl 1.36 private void heapify() {
735 : jsr166 1.56 for (int i = (size >>> 1) - 1; i >= 0; i--)
736 : jsr166 1.63 siftDown(i, (E) queue[i]);
737 : tim 1.2 }
738 :    
739 : dholmes 1.23 /**
740 : dl 1.52 * Returns the comparator used to order the elements in this
741 : jsr166 1.63 * queue, or {@code null} if this queue is sorted according to
742 : dl 1.52 * the {@linkplain Comparable natural ordering} of its elements.
743 :     *
744 :     * @return the comparator used to order this queue, or
745 : jsr166 1.63 * {@code null} if this queue is sorted according to the
746 :     * natural ordering of its elements
747 : dholmes 1.23 */
748 : tim 1.16 public Comparator<? super E> comparator() {
749 : tim 1.2 return comparator;
750 :     }
751 : dl 1.5
752 :     /**
753 : jsr166 1.77 * Saves this queue to a stream (that is, serializes it).
754 : dl 1.5 *
755 :     * @serialData The length of the array backing the instance is
756 : jsr166 1.63 * emitted (int), followed by all of its elements
757 :     * (each an {@code Object}) in the proper order.
758 : dl 1.81 * @param s the stream
759 : jsr166 1.97 * @throws java.io.IOException if an I/O error occurs
760 : dl 1.5 */
761 : dl 1.22 private void writeObject(java.io.ObjectOutputStream s)
762 : jsr166 1.75 throws java.io.IOException {
763 : dl 1.7 // Write out element count, and any hidden stuff
764 :     s.defaultWriteObject();
765 : dl 1.5
766 : jsr166 1.63 // Write out array length, for compatibility with 1.5 version
767 :     s.writeInt(Math.max(2, size + 1));
768 : dl 1.5
769 : jsr166 1.64 // Write out all elements in the "proper order".
770 : jsr166 1.63 for (int i = 0; i < size; i++)
771 : dl 1.5 s.writeObject(queue[i]);
772 :     }
773 :    
774 :     /**
775 : dl 1.81 * Reconstitutes the {@code PriorityQueue} instance from a stream
776 :     * (that is, deserializes it).
777 :     *
778 :     * @param s the stream
779 : jsr166 1.97 * @throws ClassNotFoundException if the class of a serialized object
780 :     * could not be found
781 :     * @throws java.io.IOException if an I/O error occurs
782 : dl 1.5 */
783 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
784 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
785 : dl 1.7 // Read in size, and any hidden stuff
786 :     s.defaultReadObject();
787 : dl 1.5
788 : jsr166 1.63 // Read in (and discard) array length
789 :     s.readInt();
790 :    
791 : jsr166 1.68 queue = new Object[size];
792 : dl 1.5
793 : jsr166 1.64 // Read in all elements.
794 : jsr166 1.63 for (int i = 0; i < size; i++)
795 :     queue[i] = s.readObject();
796 : jsr166 1.64
797 : jsr166 1.68 // Elements are guaranteed to be in "proper order", but the
798 :     // spec has never explained what that might be.
799 :     heapify();
800 : dl 1.5 }
801 : dl 1.81
802 : jsr166 1.106 /**
803 :     * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
804 :     * and <em>fail-fast</em> {@link Spliterator} over the elements in this
805 :     * queue.
806 :     *
807 :     * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
808 :     * {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.
809 :     * Overriding implementations should document the reporting of additional
810 :     * characteristic values.
811 :     *
812 :     * @return a {@code Spliterator} over the elements in this queue
813 :     * @since 1.8
814 :     */
815 :     public final Spliterator<E> spliterator() {
816 :     return new PriorityQueueSpliterator<>(this, 0, -1, 0);
817 : dl 1.81 }
818 :    
819 : dl 1.86 static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
820 : jsr166 1.106 /*
821 :     * This is very similar to ArrayList Spliterator, except for
822 :     * extra null checks.
823 :     */
824 : dl 1.81 private final PriorityQueue<E> pq;
825 : dl 1.89 private int index; // current index, modified on advance/split
826 :     private int fence; // -1 until first use
827 :     private int expectedModCount; // initialized when fence set
828 : dl 1.81
829 : jsr166 1.92 /** Creates new spliterator covering the given range */
830 : dl 1.81 PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
831 : jsr166 1.107 int expectedModCount) {
832 : dl 1.89 this.pq = pq;
833 :     this.index = origin;
834 :     this.fence = fence;
835 : dl 1.81 this.expectedModCount = expectedModCount;
836 :     }
837 :    
838 : dl 1.89 private int getFence() { // initialize fence to size on first use
839 :     int hi;
840 :     if ((hi = fence) < 0) {
841 :     expectedModCount = pq.modCount;
842 :     hi = fence = pq.size;
843 :     }
844 :     return hi;
845 :     }
846 : jsr166 1.90
847 : jsr166 1.106 public PriorityQueueSpliterator<E> trySplit() {
848 : dl 1.89 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
849 : dl 1.81 return (lo >= mid) ? null :
850 : jsr166 1.106 new PriorityQueueSpliterator<>(pq, lo, index = mid,
851 :     expectedModCount);
852 : dl 1.81 }
853 :    
854 : dl 1.89 @SuppressWarnings("unchecked")
855 : dl 1.95 public void forEachRemaining(Consumer<? super E> action) {
856 : dl 1.89 int i, hi, mc; // hoist accesses and checks from loop
857 :     PriorityQueue<E> q; Object[] a;
858 :     if (action == null)
859 : dl 1.81 throw new NullPointerException();
860 : dl 1.89 if ((q = pq) != null && (a = q.queue) != null) {
861 :     if ((hi = fence) < 0) {
862 :     mc = q.modCount;
863 :     hi = q.size;
864 :     }
865 :     else
866 :     mc = expectedModCount;
867 :     if ((i = index) >= 0 && (index = hi) <= a.length) {
868 :     for (E e;; ++i) {
869 :     if (i < hi) {
870 :     if ((e = (E) a[i]) == null) // must be CME
871 :     break;
872 :     action.accept(e);
873 :     }
874 :     else if (q.modCount != mc)
875 :     break;
876 :     else
877 :     return;
878 :     }
879 :     }
880 : dl 1.81 }
881 : dl 1.89 throw new ConcurrentModificationException();
882 : dl 1.81 }
883 :    
884 : dl 1.89 public boolean tryAdvance(Consumer<? super E> action) {
885 : jsr166 1.106 if (action == null)
886 :     throw new NullPointerException();
887 : dl 1.89 int hi = getFence(), lo = index;
888 :     if (lo >= 0 && lo < hi) {
889 :     index = lo + 1;
890 :     @SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
891 :     if (e == null)
892 :     throw new ConcurrentModificationException();
893 :     action.accept(e);
894 : dl 1.86 if (pq.modCount != expectedModCount)
895 :     throw new ConcurrentModificationException();
896 : dl 1.81 return true;
897 :     }
898 :     return false;
899 :     }
900 :    
901 : jsr166 1.90 public long estimateSize() {
902 :     return (long) (getFence() - index);
903 : dl 1.89 }
904 :    
905 :     public int characteristics() {
906 :     return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
907 :     }
908 : dl 1.81 }
909 : tim 1.1 }

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