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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 :     import java.util.stream.Streams;
30 : tim 1.1
31 :     /**
32 : jsr166 1.63 * An unbounded priority {@linkplain Queue queue} based on a priority heap.
33 :     * The elements of the priority queue are ordered according to their
34 :     * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
35 :     * provided at queue construction time, depending on which constructor is
36 :     * used. A priority queue does not permit {@code null} elements.
37 :     * A priority queue relying on natural ordering also does not permit
38 :     * insertion of non-comparable objects (doing so may result in
39 :     * {@code ClassCastException}).
40 : dl 1.40 *
41 : dl 1.41 * <p>The <em>head</em> of this queue is the <em>least</em> element
42 :     * with respect to the specified ordering. If multiple elements are
43 :     * tied for least value, the head is one of those elements -- ties are
44 : jsr166 1.63 * broken arbitrarily. The queue retrieval operations {@code poll},
45 :     * {@code remove}, {@code peek}, and {@code element} access the
46 : dl 1.42 * element at the head of the queue.
47 : tim 1.14 *
48 : dl 1.41 * <p>A priority queue is unbounded, but has an internal
49 :     * <i>capacity</i> governing the size of an array used to store the
50 : dl 1.40 * elements on the queue. It is always at least as large as the queue
51 :     * size. As elements are added to a priority queue, its capacity
52 :     * grows automatically. The details of the growth policy are not
53 :     * specified.
54 : tim 1.2 *
55 : dl 1.50 * <p>This class and its iterator implement all of the
56 :     * <em>optional</em> methods of the {@link Collection} and {@link
57 : dl 1.52 * Iterator} interfaces. The Iterator provided in method {@link
58 :     * #iterator()} is <em>not</em> guaranteed to traverse the elements of
59 :     * the priority queue in any particular order. If you need ordered
60 : jsr166 1.63 * traversal, consider using {@code Arrays.sort(pq.toArray())}.
61 : dl 1.29 *
62 : jsr166 1.82 * <p><strong>Note that this implementation is not synchronized.</strong>
63 : jsr166 1.63 * Multiple threads should not access a {@code PriorityQueue}
64 :     * instance concurrently if any of the threads modifies the queue.
65 :     * Instead, use the thread-safe {@link
66 : dl 1.88 * java.util.concurrent.PriorityBlockingQueue} class.
67 : dl 1.29 *
68 : jsr166 1.63 * <p>Implementation note: this implementation provides
69 : dl 1.81 * O(log(n)) time for the enqueing and dequeing methods
70 : jsr166 1.63 * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
71 :     * linear time for the {@code remove(Object)} and {@code contains(Object)}
72 :     * methods; and constant time for the retrieval methods
73 :     * ({@code peek}, {@code element}, and {@code size}).
74 : tim 1.2 *
75 :     * <p>This class is a member of the
76 : jsr166 1.65 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
77 : tim 1.2 * Java Collections Framework</a>.
78 : jsr166 1.63 *
79 : dl 1.7 * @since 1.5
80 : jsr166 1.63 * @author Josh Bloch, Doug Lea
81 : dl 1.45 * @param <E> the type of elements held in this collection
82 : tim 1.2 */
83 :     public class PriorityQueue<E> extends AbstractQueue<E>
84 : dl 1.47 implements java.io.Serializable {
85 : dholmes 1.11
86 : dl 1.31 private static final long serialVersionUID = -7720805057305804111L;
87 : dl 1.30
88 : tim 1.2 private static final int DEFAULT_INITIAL_CAPACITY = 11;
89 : tim 1.1
90 : tim 1.2 /**
91 : dl 1.55 * Priority queue represented as a balanced binary heap: the two
92 :     * children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The
93 :     * priority queue is ordered by comparator, or by the elements'
94 :     * natural ordering, if comparator is null: For each node n in the
95 :     * heap and each descendant d of n, n <= d. The element with the
96 :     * lowest value is in queue[0], assuming the queue is nonempty.
97 : tim 1.2 */
98 : dl 1.81 transient Object[] queue; // non-private to simplify nested class access
99 : tim 1.1
100 : tim 1.2 /**
101 :     * The number of elements in the priority queue.
102 :     */
103 :     private int size = 0;
104 : tim 1.1
105 : tim 1.2 /**
106 :     * The comparator, or null if priority queue uses elements'
107 :     * natural ordering.
108 :     */
109 : tim 1.16 private final Comparator<? super E> comparator;
110 : tim 1.2
111 :     /**
112 :     * The number of times this priority queue has been
113 :     * <i>structurally modified</i>. See AbstractList for gory details.
114 :     */
115 : dl 1.81 transient int modCount = 0; // non-private to simplify nested class access
116 : tim 1.2
117 :     /**
118 : jsr166 1.63 * Creates a {@code PriorityQueue} with the default initial
119 : dl 1.52 * capacity (11) that orders its elements according to their
120 :     * {@linkplain Comparable natural ordering}.
121 : tim 1.2 */
122 :     public PriorityQueue() {
123 : dholmes 1.11 this(DEFAULT_INITIAL_CAPACITY, null);
124 : tim 1.1 }
125 : tim 1.2
126 :     /**
127 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial
128 : dl 1.52 * capacity that orders its elements according to their
129 :     * {@linkplain Comparable natural ordering}.
130 : tim 1.2 *
131 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
132 : jsr166 1.63 * @throws IllegalArgumentException if {@code initialCapacity} is less
133 :     * than 1
134 : tim 1.2 */
135 :     public PriorityQueue(int initialCapacity) {
136 :     this(initialCapacity, null);
137 : tim 1.1 }
138 : tim 1.2
139 :     /**
140 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial capacity
141 : tim 1.2 * that orders its elements according to the specified comparator.
142 :     *
143 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
144 : jsr166 1.63 * @param comparator the comparator that will be used to order this
145 :     * priority queue. If {@code null}, the {@linkplain Comparable
146 :     * natural ordering} of the elements will be used.
147 :     * @throws IllegalArgumentException if {@code initialCapacity} is
148 : dl 1.52 * less than 1
149 : tim 1.2 */
150 : dl 1.52 public PriorityQueue(int initialCapacity,
151 : dholmes 1.23 Comparator<? super E> comparator) {
152 : dl 1.55 // Note: This restriction of at least one is not actually needed,
153 :     // but continues for 1.5 compatibility
154 : tim 1.2 if (initialCapacity < 1)
155 : dholmes 1.15 throw new IllegalArgumentException();
156 : dl 1.55 this.queue = new Object[initialCapacity];
157 : tim 1.2 this.comparator = comparator;
158 : tim 1.1 }
159 : jsr166 1.56
160 : dl 1.22 /**
161 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
162 :     * specified collection. If the specified collection is an instance of
163 :     * a {@link SortedSet} or is another {@code PriorityQueue}, this
164 :     * priority queue will be ordered according to the same ordering.
165 :     * Otherwise, this priority queue will be ordered according to the
166 :     * {@linkplain Comparable natural ordering} of its elements.
167 : tim 1.2 *
168 : dl 1.52 * @param c the collection whose elements are to be placed
169 :     * into this priority queue
170 : tim 1.2 * @throws ClassCastException if elements of the specified collection
171 :     * cannot be compared to one another according to the priority
172 : dl 1.52 * queue's ordering
173 :     * @throws NullPointerException if the specified collection or any
174 :     * of its elements are null
175 : tim 1.2 */
176 : jsr166 1.70 @SuppressWarnings("unchecked")
177 : tim 1.16 public PriorityQueue(Collection<? extends E> c) {
178 : jsr166 1.70 if (c instanceof SortedSet<?>) {
179 :     SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
180 :     this.comparator = (Comparator<? super E>) ss.comparator();
181 :     initElementsFromCollection(ss);
182 :     }
183 :     else if (c instanceof PriorityQueue<?>) {
184 :     PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
185 :     this.comparator = (Comparator<? super E>) pq.comparator();
186 :     initFromPriorityQueue(pq);
187 :     }
188 : dl 1.55 else {
189 : jsr166 1.70 this.comparator = null;
190 :     initFromCollection(c);
191 : tim 1.2 }
192 : dl 1.22 }
193 :    
194 :     /**
195 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
196 : dl 1.55 * specified priority queue. This priority queue will be
197 : dl 1.52 * ordered according to the same ordering as the given priority
198 :     * queue.
199 :     *
200 :     * @param c the priority queue whose elements are to be placed
201 :     * into this priority queue
202 : jsr166 1.63 * @throws ClassCastException if elements of {@code c} cannot be
203 :     * compared to one another according to {@code c}'s
204 : dl 1.52 * ordering
205 :     * @throws NullPointerException if the specified priority queue or any
206 :     * of its elements are null
207 : dl 1.22 */
208 : jsr166 1.70 @SuppressWarnings("unchecked")
209 : dl 1.22 public PriorityQueue(PriorityQueue<? extends E> c) {
210 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
211 :     initFromPriorityQueue(c);
212 : dl 1.22 }
213 : dholmes 1.18
214 : dl 1.22 /**
215 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
216 :     * specified sorted set. This priority queue will be ordered
217 : dl 1.52 * according to the same ordering as the given sorted set.
218 :     *
219 :     * @param c the sorted set whose elements are to be placed
220 : jsr166 1.63 * into this priority queue
221 : dl 1.52 * @throws ClassCastException if elements of the specified sorted
222 :     * set cannot be compared to one another according to the
223 :     * sorted set's ordering
224 :     * @throws NullPointerException if the specified sorted set or any
225 :     * of its elements are null
226 : dl 1.22 */
227 : jsr166 1.70 @SuppressWarnings("unchecked")
228 : dl 1.22 public PriorityQueue(SortedSet<? extends E> c) {
229 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
230 :     initElementsFromCollection(c);
231 :     }
232 :    
233 :     private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
234 :     if (c.getClass() == PriorityQueue.class) {
235 :     this.queue = c.toArray();
236 :     this.size = c.size();
237 :     } else {
238 :     initFromCollection(c);
239 :     }
240 :     }
241 :    
242 :     private void initElementsFromCollection(Collection<? extends E> c) {
243 :     Object[] a = c.toArray();
244 :     // If c.toArray incorrectly doesn't return Object[], copy it.
245 :     if (a.getClass() != Object[].class)
246 :     a = Arrays.copyOf(a, a.length, Object[].class);
247 :     int len = a.length;
248 :     if (len == 1 || this.comparator != null)
249 :     for (int i = 0; i < len; i++)
250 :     if (a[i] == null)
251 :     throw new NullPointerException();
252 :     this.queue = a;
253 :     this.size = a.length;
254 : tim 1.1 }
255 :    
256 : dl 1.22 /**
257 : jsr166 1.63 * Initializes queue array with elements from the given Collection.
258 :     *
259 : dl 1.55 * @param c the collection
260 : dl 1.22 */
261 : dl 1.55 private void initFromCollection(Collection<? extends E> c) {
262 : jsr166 1.70 initElementsFromCollection(c);
263 :     heapify();
264 : jsr166 1.56 }
265 : dl 1.55
266 :     /**
267 : jsr166 1.70 * The maximum size of array to allocate.
268 :     * Some VMs reserve some header words in an array.
269 :     * Attempts to allocate larger arrays may result in
270 :     * OutOfMemoryError: Requested array size exceeds VM limit
271 :     */
272 :     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
273 :    
274 :     /**
275 : dl 1.55 * Increases the capacity of the array.
276 :     *
277 :     * @param minCapacity the desired minimum capacity
278 :     */
279 :     private void grow(int minCapacity) {
280 : jsr166 1.68 int oldCapacity = queue.length;
281 : dl 1.55 // Double size if small; else grow by 50%
282 : jsr166 1.70 int newCapacity = oldCapacity + ((oldCapacity < 64) ?
283 :     (oldCapacity + 2) :
284 :     (oldCapacity >> 1));
285 :     // overflow-conscious code
286 :     if (newCapacity - MAX_ARRAY_SIZE > 0)
287 :     newCapacity = hugeCapacity(minCapacity);
288 : dl 1.55 queue = Arrays.copyOf(queue, newCapacity);
289 : dl 1.22 }
290 : dl 1.36
291 : jsr166 1.70 private static int hugeCapacity(int minCapacity) {
292 :     if (minCapacity < 0) // overflow
293 :     throw new OutOfMemoryError();
294 :     return (minCapacity > MAX_ARRAY_SIZE) ?
295 :     Integer.MAX_VALUE :
296 :     MAX_ARRAY_SIZE;
297 :     }
298 :    
299 : tim 1.2 /**
300 : dl 1.42 * Inserts the specified element into this priority queue.
301 : tim 1.2 *
302 : jsr166 1.63 * @return {@code true} (as specified by {@link Collection#add})
303 : dl 1.52 * @throws ClassCastException if the specified element cannot be
304 :     * compared with elements currently in this priority queue
305 :     * according to the priority queue's ordering
306 :     * @throws NullPointerException if the specified element is null
307 : tim 1.2 */
308 : dl 1.52 public boolean add(E e) {
309 :     return offer(e);
310 :     }
311 :    
312 :     /**
313 :     * Inserts the specified element into this priority queue.
314 :     *
315 : jsr166 1.63 * @return {@code true} (as specified by {@link Queue#offer})
316 : dl 1.52 * @throws ClassCastException if the specified element cannot be
317 :     * compared with elements currently in this priority queue
318 :     * according to the priority queue's ordering
319 :     * @throws NullPointerException if the specified element is null
320 :     */
321 :     public boolean offer(E e) {
322 :     if (e == null)
323 : dholmes 1.11 throw new NullPointerException();
324 :     modCount++;
325 : dl 1.55 int i = size;
326 :     if (i >= queue.length)
327 :     grow(i + 1);
328 :     size = i + 1;
329 :     if (i == 0)
330 :     queue[0] = e;
331 :     else
332 :     siftUp(i, e);
333 : dholmes 1.11 return true;
334 :     }
335 :    
336 : dl 1.81 @SuppressWarnings("unchecked")
337 : dl 1.40 public E peek() {
338 : jsr166 1.73 return (size == 0) ? null : (E) queue[0];
339 : tim 1.1 }
340 :    
341 : dl 1.52 private int indexOf(Object o) {
342 : jsr166 1.68 if (o != null) {
343 : dl 1.55 for (int i = 0; i < size; i++)
344 :     if (o.equals(queue[i]))
345 :     return i;
346 :     }
347 : dl 1.52 return -1;
348 :     }
349 :    
350 :     /**
351 :     * Removes a single instance of the specified element from this queue,
352 : jsr166 1.63 * if it is present. More formally, removes an element {@code e} such
353 :     * that {@code o.equals(e)}, if this queue contains one or more such
354 :     * elements. Returns {@code true} if and only if this queue contained
355 :     * the specified element (or equivalently, if this queue changed as a
356 :     * result of the call).
357 : dl 1.52 *
358 :     * @param o element to be removed from this queue, if present
359 : jsr166 1.63 * @return {@code true} if this queue changed as a result of the call
360 : dl 1.52 */
361 :     public boolean remove(Object o) {
362 : jsr166 1.68 int i = indexOf(o);
363 :     if (i == -1)
364 :     return false;
365 :     else {
366 :     removeAt(i);
367 :     return true;
368 :     }
369 : dl 1.52 }
370 : dholmes 1.11
371 : jsr166 1.56 /**
372 : dl 1.55 * Version of remove using reference equality, not equals.
373 : jsr166 1.59 * Needed by iterator.remove.
374 : jsr166 1.56 *
375 : dl 1.55 * @param o element to be removed from this queue, if present
376 : jsr166 1.63 * @return {@code true} if removed
377 : dl 1.55 */
378 :     boolean removeEq(Object o) {
379 : jsr166 1.68 for (int i = 0; i < size; i++) {
380 :     if (o == queue[i]) {
381 : dl 1.55 removeAt(i);
382 :     return true;
383 :     }
384 :     }
385 :     return false;
386 :     }
387 :    
388 : dholmes 1.11 /**
389 : jsr166 1.63 * Returns {@code true} if this queue contains the specified element.
390 :     * More formally, returns {@code true} if and only if this queue contains
391 :     * at least one element {@code e} such that {@code o.equals(e)}.
392 : dholmes 1.23 *
393 : dl 1.52 * @param o object to be checked for containment in this queue
394 : jsr166 1.63 * @return {@code true} if this queue contains the specified element
395 : dholmes 1.11 */
396 : dl 1.52 public boolean contains(Object o) {
397 : jsr166 1.68 return indexOf(o) != -1;
398 : tim 1.14 }
399 : dholmes 1.11
400 : dl 1.49 /**
401 : jsr166 1.63 * Returns an array containing all of the elements in this queue.
402 : dl 1.52 * The elements are in no particular order.
403 :     *
404 :     * <p>The returned array will be "safe" in that no references to it are
405 : jsr166 1.63 * maintained by this queue. (In other words, this method must allocate
406 : dl 1.52 * a new array). The caller is thus free to modify the returned array.
407 :     *
408 : jsr166 1.63 * <p>This method acts as bridge between array-based and collection-based
409 :     * APIs.
410 :     *
411 : jsr166 1.59 * @return an array containing all of the elements in this queue
412 : dl 1.49 */
413 : dl 1.52 public Object[] toArray() {
414 : dl 1.55 return Arrays.copyOf(queue, size);
415 : dl 1.52 }
416 : tim 1.2
417 : dl 1.52 /**
418 : jsr166 1.63 * Returns an array containing all of the elements in this queue; the
419 :     * runtime type of the returned array is that of the specified array.
420 :     * The returned array elements are in no particular order.
421 :     * If the queue fits in the specified array, it is returned therein.
422 :     * Otherwise, a new array is allocated with the runtime type of the
423 :     * specified array and the size of this queue.
424 : dl 1.52 *
425 :     * <p>If the queue fits in the specified array with room to spare
426 :     * (i.e., the array has more elements than the queue), the element in
427 :     * the array immediately following the end of the collection is set to
428 : jsr166 1.63 * {@code null}.
429 :     *
430 :     * <p>Like the {@link #toArray()} method, this method acts as bridge between
431 :     * array-based and collection-based APIs. Further, this method allows
432 :     * precise control over the runtime type of the output array, and may,
433 :     * under certain circumstances, be used to save allocation costs.
434 :     *
435 : jsr166 1.80 * <p>Suppose {@code x} is a queue known to contain only strings.
436 : jsr166 1.63 * The following code can be used to dump the queue into a newly
437 : jsr166 1.80 * allocated array of {@code String}:
438 : jsr166 1.63 *
439 : jsr166 1.72 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
440 : jsr166 1.63 *
441 : jsr166 1.80 * Note that {@code toArray(new Object[0])} is identical in function to
442 :     * {@code toArray()}.
443 : dl 1.52 *
444 :     * @param a the array into which the elements of the queue are to
445 :     * be stored, if it is big enough; otherwise, a new array of the
446 :     * same runtime type is allocated for this purpose.
447 : jsr166 1.63 * @return an array containing all of the elements in this queue
448 : dl 1.52 * @throws ArrayStoreException if the runtime type of the specified array
449 :     * is not a supertype of the runtime type of every element in
450 :     * this queue
451 :     * @throws NullPointerException if the specified array is null
452 :     */
453 : jsr166 1.84 @SuppressWarnings("unchecked")
454 : dl 1.52 public <T> T[] toArray(T[] a) {
455 : jsr166 1.85 final int size = this.size;
456 : dl 1.52 if (a.length < size)
457 :     // Make a new array of a's runtime type, but my contents:
458 : dl 1.55 return (T[]) Arrays.copyOf(queue, size, a.getClass());
459 : jsr166 1.68 System.arraycopy(queue, 0, a, 0, size);
460 : dl 1.52 if (a.length > size)
461 :     a[size] = null;
462 :     return a;
463 : tim 1.1 }
464 : tim 1.2
465 : dholmes 1.23 /**
466 :     * Returns an iterator over the elements in this queue. The iterator
467 :     * does not return the elements in any particular order.
468 :     *
469 : dl 1.52 * @return an iterator over the elements in this queue
470 : dholmes 1.23 */
471 : tim 1.2 public Iterator<E> iterator() {
472 : dl 1.7 return new Itr();
473 : tim 1.2 }
474 :    
475 : dl 1.55 private final class Itr implements Iterator<E> {
476 : dl 1.7 /**
477 :     * Index (into queue array) of element to be returned by
478 : tim 1.2 * subsequent call to next.
479 : dl 1.7 */
480 : dl 1.55 private int cursor = 0;
481 : tim 1.2
482 : dl 1.7 /**
483 : dl 1.36 * Index of element returned by most recent call to next,
484 :     * unless that element came from the forgetMeNot list.
485 : dl 1.55 * Set to -1 if element is deleted by a call to remove.
486 : dl 1.7 */
487 : dl 1.55 private int lastRet = -1;
488 : dl 1.7
489 :     /**
490 : dl 1.55 * A queue of elements that were moved from the unvisited portion of
491 : dl 1.36 * the heap into the visited portion as a result of "unlucky" element
492 :     * removals during the iteration. (Unlucky element removals are those
493 : dl 1.55 * that require a siftup instead of a siftdown.) We must visit all of
494 : dl 1.36 * the elements in this list to complete the iteration. We do this
495 :     * after we've completed the "normal" iteration.
496 :     *
497 :     * We expect that most iterations, even those involving removals,
498 : jsr166 1.63 * will not need to store elements in this field.
499 : dl 1.36 */
500 : dl 1.55 private ArrayDeque<E> forgetMeNot = null;
501 : dl 1.36
502 :     /**
503 :     * Element returned by the most recent call to next iff that
504 :     * element was drawn from the forgetMeNot list.
505 :     */
506 : dl 1.55 private E lastRetElt = null;
507 :    
508 :     /**
509 :     * The modCount value that the iterator believes that the backing
510 : jsr166 1.63 * Queue should have. If this expectation is violated, the iterator
511 : dl 1.55 * has detected concurrent modification.
512 :     */
513 :     private int expectedModCount = modCount;
514 : dl 1.35
515 : dl 1.7 public boolean hasNext() {
516 : jsr166 1.56 return cursor < size ||
517 : dl 1.55 (forgetMeNot != null && !forgetMeNot.isEmpty());
518 : dl 1.7 }
519 :    
520 : dl 1.81 @SuppressWarnings("unchecked")
521 : dl 1.7 public E next() {
522 : dl 1.55 if (expectedModCount != modCount)
523 :     throw new ConcurrentModificationException();
524 : jsr166 1.56 if (cursor < size)
525 : dl 1.55 return (E) queue[lastRet = cursor++];
526 :     if (forgetMeNot != null) {
527 :     lastRet = -1;
528 :     lastRetElt = forgetMeNot.poll();
529 : jsr166 1.56 if (lastRetElt != null)
530 : dl 1.55 return lastRetElt;
531 : dl 1.36 }
532 : dl 1.55 throw new NoSuchElementException();
533 : dl 1.7 }
534 : tim 1.2
535 : dl 1.7 public void remove() {
536 : dl 1.55 if (expectedModCount != modCount)
537 :     throw new ConcurrentModificationException();
538 :     if (lastRet != -1) {
539 : dl 1.36 E moved = PriorityQueue.this.removeAt(lastRet);
540 : dl 1.55 lastRet = -1;
541 : jsr166 1.56 if (moved == null)
542 : dl 1.36 cursor--;
543 : dl 1.55 else {
544 : dl 1.36 if (forgetMeNot == null)
545 : dl 1.89 forgetMeNot = new ArrayDeque<>();
546 : dl 1.36 forgetMeNot.add(moved);
547 : jsr166 1.56 }
548 : jsr166 1.63 } else if (lastRetElt != null) {
549 : dl 1.55 PriorityQueue.this.removeEq(lastRetElt);
550 : dl 1.36 lastRetElt = null;
551 : jsr166 1.63 } else {
552 :     throw new IllegalStateException();
553 : jsr166 1.68 }
554 : tim 1.2 expectedModCount = modCount;
555 : dl 1.7 }
556 : tim 1.2 }
557 :    
558 : tim 1.1 public int size() {
559 : tim 1.2 return size;
560 : tim 1.1 }
561 : tim 1.2
562 :     /**
563 : dl 1.52 * Removes all of the elements from this priority queue.
564 : dl 1.49 * The queue will be empty after this call returns.
565 : tim 1.2 */
566 :     public void clear() {
567 :     modCount++;
568 : dl 1.55 for (int i = 0; i < size; i++)
569 : tim 1.2 queue[i] = null;
570 :     size = 0;
571 :     }
572 :    
573 : dl 1.81 @SuppressWarnings("unchecked")
574 : dl 1.40 public E poll() {
575 : dl 1.36 if (size == 0)
576 : dl 1.40 return null;
577 : dl 1.55 int s = --size;
578 : dl 1.36 modCount++;
579 : jsr166 1.63 E result = (E) queue[0];
580 :     E x = (E) queue[s];
581 : dl 1.55 queue[s] = null;
582 :     if (s != 0)
583 :     siftDown(0, x);
584 : dl 1.36 return result;
585 :     }
586 :    
587 :     /**
588 : dl 1.55 * Removes the ith element from queue.
589 : tim 1.2 *
590 : dl 1.55 * Normally this method leaves the elements at up to i-1,
591 :     * inclusive, untouched. Under these circumstances, it returns
592 :     * null. Occasionally, in order to maintain the heap invariant,
593 :     * it must swap a later element of the list with one earlier than
594 :     * i. Under these circumstances, this method returns the element
595 :     * that was previously at the end of the list and is now at some
596 :     * position before i. This fact is used by iterator.remove so as to
597 : jsr166 1.63 * avoid missing traversing elements.
598 : tim 1.2 */
599 : dl 1.81 @SuppressWarnings("unchecked")
600 : dl 1.52 private E removeAt(int i) {
601 : jsr166 1.74 // assert i >= 0 && i < size;
602 : tim 1.2 modCount++;
603 : dl 1.55 int s = --size;
604 :     if (s == i) // removed last element
605 :     queue[i] = null;
606 :     else {
607 :     E moved = (E) queue[s];
608 : jsr166 1.56 queue[s] = null;
609 : dl 1.55 siftDown(i, moved);
610 : dl 1.36 if (queue[i] == moved) {
611 : dl 1.55 siftUp(i, moved);
612 : dl 1.36 if (queue[i] != moved)
613 :     return moved;
614 :     }
615 : dl 1.35 }
616 : dl 1.36 return null;
617 : tim 1.1 }
618 :    
619 : tim 1.2 /**
620 : dl 1.55 * Inserts item x at position k, maintaining heap invariant by
621 :     * promoting x up the tree until it is greater than or equal to
622 :     * its parent, or is the root.
623 :     *
624 :     * To simplify and speed up coercions and comparisons. the
625 :     * Comparable and Comparator versions are separated into different
626 :     * methods that are otherwise identical. (Similarly for siftDown.)
627 : jsr166 1.56 *
628 : dl 1.55 * @param k the position to fill
629 :     * @param x the item to insert
630 :     */
631 :     private void siftUp(int k, E x) {
632 : jsr166 1.56 if (comparator != null)
633 : dl 1.55 siftUpUsingComparator(k, x);
634 :     else
635 :     siftUpComparable(k, x);
636 :     }
637 :    
638 : dl 1.81 @SuppressWarnings("unchecked")
639 : dl 1.55 private void siftUpComparable(int k, E x) {
640 :     Comparable<? super E> key = (Comparable<? super E>) x;
641 :     while (k > 0) {
642 :     int parent = (k - 1) >>> 1;
643 :     Object e = queue[parent];
644 : jsr166 1.63 if (key.compareTo((E) e) >= 0)
645 : dl 1.55 break;
646 :     queue[k] = e;
647 :     k = parent;
648 :     }
649 :     queue[k] = key;
650 :     }
651 :    
652 : dl 1.81 @SuppressWarnings("unchecked")
653 : dl 1.55 private void siftUpUsingComparator(int k, E x) {
654 :     while (k > 0) {
655 :     int parent = (k - 1) >>> 1;
656 :     Object e = queue[parent];
657 : jsr166 1.63 if (comparator.compare(x, (E) e) >= 0)
658 : dl 1.55 break;
659 :     queue[k] = e;
660 :     k = parent;
661 :     }
662 :     queue[k] = x;
663 :     }
664 :    
665 :     /**
666 :     * Inserts item x at position k, maintaining heap invariant by
667 :     * demoting x down the tree repeatedly until it is less than or
668 :     * equal to its children or is a leaf.
669 :     *
670 :     * @param k the position to fill
671 :     * @param x the item to insert
672 :     */
673 :     private void siftDown(int k, E x) {
674 : jsr166 1.56 if (comparator != null)
675 : dl 1.55 siftDownUsingComparator(k, x);
676 :     else
677 :     siftDownComparable(k, x);
678 :     }
679 :    
680 : dl 1.81 @SuppressWarnings("unchecked")
681 : dl 1.55 private void siftDownComparable(int k, E x) {
682 :     Comparable<? super E> key = (Comparable<? super E>)x;
683 :     int half = size >>> 1; // loop while a non-leaf
684 :     while (k < half) {
685 :     int child = (k << 1) + 1; // assume left child is least
686 :     Object c = queue[child];
687 :     int right = child + 1;
688 :     if (right < size &&
689 : jsr166 1.63 ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
690 : dl 1.55 c = queue[child = right];
691 : jsr166 1.63 if (key.compareTo((E) c) <= 0)
692 : dl 1.55 break;
693 :     queue[k] = c;
694 :     k = child;
695 :     }
696 :     queue[k] = key;
697 :     }
698 :    
699 : dl 1.81 @SuppressWarnings("unchecked")
700 : dl 1.55 private void siftDownUsingComparator(int k, E x) {
701 :     int half = size >>> 1;
702 :     while (k < half) {
703 :     int child = (k << 1) + 1;
704 :     Object c = queue[child];
705 :     int right = child + 1;
706 :     if (right < size &&
707 : jsr166 1.63 comparator.compare((E) c, (E) queue[right]) > 0)
708 : jsr166 1.56 c = queue[child = right];
709 : jsr166 1.63 if (comparator.compare(x, (E) c) <= 0)
710 : dl 1.55 break;
711 :     queue[k] = c;
712 :     k = child;
713 : tim 1.2 }
714 : dl 1.55 queue[k] = x;
715 : dl 1.36 }
716 : dl 1.35
717 : dl 1.36 /**
718 :     * Establishes the heap invariant (described above) in the entire tree,
719 :     * assuming nothing about the order of the elements prior to the call.
720 :     */
721 : dl 1.81 @SuppressWarnings("unchecked")
722 : dl 1.36 private void heapify() {
723 : jsr166 1.56 for (int i = (size >>> 1) - 1; i >= 0; i--)
724 : jsr166 1.63 siftDown(i, (E) queue[i]);
725 : tim 1.2 }
726 :    
727 : dholmes 1.23 /**
728 : dl 1.52 * Returns the comparator used to order the elements in this
729 : jsr166 1.63 * queue, or {@code null} if this queue is sorted according to
730 : dl 1.52 * the {@linkplain Comparable natural ordering} of its elements.
731 :     *
732 :     * @return the comparator used to order this queue, or
733 : jsr166 1.63 * {@code null} if this queue is sorted according to the
734 :     * natural ordering of its elements
735 : dholmes 1.23 */
736 : tim 1.16 public Comparator<? super E> comparator() {
737 : tim 1.2 return comparator;
738 :     }
739 : dl 1.5
740 :     /**
741 : jsr166 1.77 * Saves this queue to a stream (that is, serializes it).
742 : dl 1.5 *
743 :     * @serialData The length of the array backing the instance is
744 : jsr166 1.63 * emitted (int), followed by all of its elements
745 :     * (each an {@code Object}) in the proper order.
746 : dl 1.81 * @param s the stream
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 : dl 1.5 */
767 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
768 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
769 : dl 1.7 // Read in size, and any hidden stuff
770 :     s.defaultReadObject();
771 : dl 1.5
772 : jsr166 1.63 // Read in (and discard) array length
773 :     s.readInt();
774 :    
775 : jsr166 1.68 queue = new Object[size];
776 : dl 1.5
777 : jsr166 1.64 // Read in all elements.
778 : jsr166 1.63 for (int i = 0; i < size; i++)
779 :     queue[i] = s.readObject();
780 : jsr166 1.64
781 : jsr166 1.68 // Elements are guaranteed to be in "proper order", but the
782 :     // spec has never explained what that might be.
783 :     heapify();
784 : dl 1.5 }
785 : dl 1.81
786 : dl 1.89 final Spliterator<E> spliterator() {
787 :     return new PriorityQueueSpliterator<E>(this, 0, -1, 0);
788 : dl 1.81 }
789 :    
790 :     public Stream<E> stream() {
791 : dl 1.89 return Streams.stream(spliterator());
792 : dl 1.81 }
793 : dl 1.89
794 : dl 1.81 public Stream<E> parallelStream() {
795 : dl 1.89 return Streams.parallelStream(spliterator());
796 : dl 1.81 }
797 :    
798 : dl 1.86 static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
799 : dl 1.89 /*
800 :     * This is very similar to ArrayList Spliterator, except for
801 :     * extra null checks.
802 :     */
803 : dl 1.81 private final PriorityQueue<E> pq;
804 : dl 1.89 private int index; // current index, modified on advance/split
805 :     private int fence; // -1 until first use
806 :     private int expectedModCount; // initialized when fence set
807 : dl 1.81
808 : jsr166 1.91 /** Creates new spliterator covering the given range */
809 : dl 1.81 PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
810 :     int expectedModCount) {
811 : dl 1.89 this.pq = pq;
812 :     this.index = origin;
813 :     this.fence = fence;
814 : dl 1.81 this.expectedModCount = expectedModCount;
815 :     }
816 :    
817 : dl 1.89 private int getFence() { // initialize fence to size on first use
818 :     int hi;
819 :     if ((hi = fence) < 0) {
820 :     expectedModCount = pq.modCount;
821 :     hi = fence = pq.size;
822 :     }
823 :     return hi;
824 :     }
825 : jsr166 1.90
826 : dl 1.81 public PriorityQueueSpliterator<E> trySplit() {
827 : dl 1.89 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
828 : dl 1.81 return (lo >= mid) ? null :
829 : jsr166 1.90 new PriorityQueueSpliterator<E>(pq, lo, index = mid,
830 : dl 1.86 expectedModCount);
831 : dl 1.81 }
832 :    
833 : dl 1.89 @SuppressWarnings("unchecked")
834 :     public void forEach(Consumer<? super E> action) {
835 :     int i, hi, mc; // hoist accesses and checks from loop
836 :     PriorityQueue<E> q; Object[] a;
837 :     if (action == null)
838 : dl 1.81 throw new NullPointerException();
839 : dl 1.89 if ((q = pq) != null && (a = q.queue) != null) {
840 :     if ((hi = fence) < 0) {
841 :     mc = q.modCount;
842 :     hi = q.size;
843 :     }
844 :     else
845 :     mc = expectedModCount;
846 :     if ((i = index) >= 0 && (index = hi) <= a.length) {
847 :     for (E e;; ++i) {
848 :     if (i < hi) {
849 :     if ((e = (E) a[i]) == null) // must be CME
850 :     break;
851 :     action.accept(e);
852 :     }
853 :     else if (q.modCount != mc)
854 :     break;
855 :     else
856 :     return;
857 :     }
858 :     }
859 : dl 1.81 }
860 : dl 1.89 throw new ConcurrentModificationException();
861 : dl 1.81 }
862 :    
863 : dl 1.89 public boolean tryAdvance(Consumer<? super E> action) {
864 :     int hi = getFence(), lo = index;
865 :     if (lo >= 0 && lo < hi) {
866 :     index = lo + 1;
867 :     @SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
868 :     if (e == null)
869 :     throw new ConcurrentModificationException();
870 :     action.accept(e);
871 : dl 1.86 if (pq.modCount != expectedModCount)
872 :     throw new ConcurrentModificationException();
873 : dl 1.81 return true;
874 :     }
875 :     return false;
876 :     }
877 :    
878 : jsr166 1.90 public long estimateSize() {
879 :     return (long) (getFence() - index);
880 : dl 1.89 }
881 :    
882 :     public int characteristics() {
883 :     return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
884 :     }
885 : dl 1.81 }
886 : tim 1.1 }

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