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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 : jsr166 1.111 * #iterator()} and the Spliterator provided in method {@link #spliterator()}
58 :     * are <em>not</em> guaranteed to traverse the elements of
59 : dl 1.52 * 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 : jsr166 1.98 * O(log(n)) time for the enqueuing and dequeuing 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 : jsr166 1.101 * @param <E> the type of elements held in this queue
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 : jsr166 1.107 int size;
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 : jsr166 1.106 transient int modCount; // 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 1.106 * Creates a {@code PriorityQueue} with the default initial capacity and
141 :     * whose elements are ordered according to the specified comparator.
142 :     *
143 :     * @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 :     * @since 1.8
147 :     */
148 :     public PriorityQueue(Comparator<? super E> comparator) {
149 :     this(DEFAULT_INITIAL_CAPACITY, comparator);
150 :     }
151 :    
152 :     /**
153 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial capacity
154 : tim 1.2 * that orders its elements according to the specified comparator.
155 :     *
156 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
157 : jsr166 1.63 * @param comparator the comparator that will be used to order this
158 :     * priority queue. If {@code null}, the {@linkplain Comparable
159 :     * natural ordering} of the elements will be used.
160 :     * @throws IllegalArgumentException if {@code initialCapacity} is
161 : dl 1.52 * less than 1
162 : tim 1.2 */
163 : dl 1.52 public PriorityQueue(int initialCapacity,
164 : dholmes 1.23 Comparator<? super E> comparator) {
165 : dl 1.55 // Note: This restriction of at least one is not actually needed,
166 :     // but continues for 1.5 compatibility
167 : tim 1.2 if (initialCapacity < 1)
168 : dholmes 1.15 throw new IllegalArgumentException();
169 : dl 1.55 this.queue = new Object[initialCapacity];
170 : tim 1.2 this.comparator = comparator;
171 : tim 1.1 }
172 : jsr166 1.56
173 : dl 1.22 /**
174 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
175 :     * specified collection. If the specified collection is an instance of
176 :     * a {@link SortedSet} or is another {@code PriorityQueue}, this
177 :     * priority queue will be ordered according to the same ordering.
178 :     * Otherwise, this priority queue will be ordered according to the
179 :     * {@linkplain Comparable natural ordering} of its elements.
180 : tim 1.2 *
181 : dl 1.52 * @param c the collection whose elements are to be placed
182 :     * into this priority queue
183 : tim 1.2 * @throws ClassCastException if elements of the specified collection
184 :     * cannot be compared to one another according to the priority
185 : dl 1.52 * queue's ordering
186 :     * @throws NullPointerException if the specified collection or any
187 :     * of its elements are null
188 : tim 1.2 */
189 : jsr166 1.70 @SuppressWarnings("unchecked")
190 : tim 1.16 public PriorityQueue(Collection<? extends E> c) {
191 : jsr166 1.70 if (c instanceof SortedSet<?>) {
192 :     SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
193 :     this.comparator = (Comparator<? super E>) ss.comparator();
194 :     initElementsFromCollection(ss);
195 :     }
196 :     else if (c instanceof PriorityQueue<?>) {
197 :     PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
198 :     this.comparator = (Comparator<? super E>) pq.comparator();
199 :     initFromPriorityQueue(pq);
200 :     }
201 : dl 1.55 else {
202 : jsr166 1.70 this.comparator = null;
203 :     initFromCollection(c);
204 : tim 1.2 }
205 : dl 1.22 }
206 :    
207 :     /**
208 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
209 : dl 1.55 * specified priority queue. This priority queue will be
210 : dl 1.52 * ordered according to the same ordering as the given priority
211 :     * queue.
212 :     *
213 :     * @param c the priority queue whose elements are to be placed
214 :     * into this priority queue
215 : jsr166 1.63 * @throws ClassCastException if elements of {@code c} cannot be
216 :     * compared to one another according to {@code c}'s
217 : dl 1.52 * ordering
218 :     * @throws NullPointerException if the specified priority queue or any
219 :     * of its elements are null
220 : dl 1.22 */
221 : jsr166 1.70 @SuppressWarnings("unchecked")
222 : dl 1.22 public PriorityQueue(PriorityQueue<? extends E> c) {
223 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
224 :     initFromPriorityQueue(c);
225 : dl 1.22 }
226 : dholmes 1.18
227 : dl 1.22 /**
228 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
229 :     * specified sorted set. This priority queue will be ordered
230 : dl 1.52 * according to the same ordering as the given sorted set.
231 :     *
232 :     * @param c the sorted set whose elements are to be placed
233 : jsr166 1.63 * into this priority queue
234 : dl 1.52 * @throws ClassCastException if elements of the specified sorted
235 :     * set cannot be compared to one another according to the
236 :     * sorted set's ordering
237 :     * @throws NullPointerException if the specified sorted set or any
238 :     * of its elements are null
239 : dl 1.22 */
240 : jsr166 1.70 @SuppressWarnings("unchecked")
241 : dl 1.22 public PriorityQueue(SortedSet<? extends E> c) {
242 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
243 :     initElementsFromCollection(c);
244 :     }
245 :    
246 :     private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
247 :     if (c.getClass() == PriorityQueue.class) {
248 :     this.queue = c.toArray();
249 :     this.size = c.size();
250 :     } else {
251 :     initFromCollection(c);
252 :     }
253 :     }
254 :    
255 :     private void initElementsFromCollection(Collection<? extends E> c) {
256 :     Object[] a = c.toArray();
257 :     // If c.toArray incorrectly doesn't return Object[], copy it.
258 :     if (a.getClass() != Object[].class)
259 :     a = Arrays.copyOf(a, a.length, Object[].class);
260 :     int len = a.length;
261 :     if (len == 1 || this.comparator != null)
262 : jsr166 1.106 for (Object e : a)
263 :     if (e == null)
264 : jsr166 1.70 throw new NullPointerException();
265 :     this.queue = a;
266 :     this.size = a.length;
267 : tim 1.1 }
268 :    
269 : dl 1.22 /**
270 : jsr166 1.63 * Initializes queue array with elements from the given Collection.
271 :     *
272 : dl 1.55 * @param c the collection
273 : dl 1.22 */
274 : dl 1.55 private void initFromCollection(Collection<? extends E> c) {
275 : jsr166 1.70 initElementsFromCollection(c);
276 :     heapify();
277 : jsr166 1.56 }
278 : dl 1.55
279 :     /**
280 : jsr166 1.70 * The maximum size of array to allocate.
281 :     * Some VMs reserve some header words in an array.
282 :     * Attempts to allocate larger arrays may result in
283 :     * OutOfMemoryError: Requested array size exceeds VM limit
284 :     */
285 :     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
286 :    
287 :     /**
288 : dl 1.55 * Increases the capacity of the array.
289 :     *
290 :     * @param minCapacity the desired minimum capacity
291 :     */
292 :     private void grow(int minCapacity) {
293 : jsr166 1.68 int oldCapacity = queue.length;
294 : dl 1.55 // Double size if small; else grow by 50%
295 : jsr166 1.70 int newCapacity = oldCapacity + ((oldCapacity < 64) ?
296 :     (oldCapacity + 2) :
297 :     (oldCapacity >> 1));
298 :     // overflow-conscious code
299 :     if (newCapacity - MAX_ARRAY_SIZE > 0)
300 :     newCapacity = hugeCapacity(minCapacity);
301 : dl 1.55 queue = Arrays.copyOf(queue, newCapacity);
302 : dl 1.22 }
303 : dl 1.36
304 : jsr166 1.70 private static int hugeCapacity(int minCapacity) {
305 :     if (minCapacity < 0) // overflow
306 :     throw new OutOfMemoryError();
307 :     return (minCapacity > MAX_ARRAY_SIZE) ?
308 :     Integer.MAX_VALUE :
309 :     MAX_ARRAY_SIZE;
310 :     }
311 :    
312 : tim 1.2 /**
313 : dl 1.42 * Inserts the specified element into this priority queue.
314 : tim 1.2 *
315 : jsr166 1.63 * @return {@code true} (as specified by {@link Collection#add})
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 : tim 1.2 */
321 : dl 1.52 public boolean add(E e) {
322 :     return offer(e);
323 :     }
324 :    
325 :     /**
326 :     * Inserts the specified element into this priority queue.
327 :     *
328 : jsr166 1.63 * @return {@code true} (as specified by {@link Queue#offer})
329 : dl 1.52 * @throws ClassCastException if the specified element cannot be
330 :     * compared with elements currently in this priority queue
331 :     * according to the priority queue's ordering
332 :     * @throws NullPointerException if the specified element is null
333 :     */
334 :     public boolean offer(E e) {
335 :     if (e == null)
336 : dholmes 1.11 throw new NullPointerException();
337 :     modCount++;
338 : dl 1.55 int i = size;
339 :     if (i >= queue.length)
340 :     grow(i + 1);
341 : jsr166 1.109 siftUp(i, e);
342 : dl 1.55 size = i + 1;
343 : dholmes 1.11 return true;
344 :     }
345 :    
346 : dl 1.81 @SuppressWarnings("unchecked")
347 : dl 1.40 public E peek() {
348 : jsr166 1.73 return (size == 0) ? null : (E) queue[0];
349 : tim 1.1 }
350 :    
351 : dl 1.52 private int indexOf(Object o) {
352 : jsr166 1.68 if (o != null) {
353 : dl 1.55 for (int i = 0; i < size; i++)
354 :     if (o.equals(queue[i]))
355 :     return i;
356 :     }
357 : dl 1.52 return -1;
358 :     }
359 :    
360 :     /**
361 :     * Removes a single instance of the specified element from this queue,
362 : jsr166 1.63 * if it is present. More formally, removes an element {@code e} such
363 :     * that {@code o.equals(e)}, if this queue contains one or more such
364 :     * elements. Returns {@code true} if and only if this queue contained
365 :     * the specified element (or equivalently, if this queue changed as a
366 :     * result of the call).
367 : dl 1.52 *
368 :     * @param o element to be removed from this queue, if present
369 : jsr166 1.63 * @return {@code true} if this queue changed as a result of the call
370 : dl 1.52 */
371 :     public boolean remove(Object o) {
372 : jsr166 1.68 int i = indexOf(o);
373 :     if (i == -1)
374 :     return false;
375 :     else {
376 :     removeAt(i);
377 :     return true;
378 :     }
379 : dl 1.52 }
380 : dholmes 1.11
381 : jsr166 1.56 /**
382 : dl 1.55 * Version of remove using reference equality, not equals.
383 : jsr166 1.59 * Needed by iterator.remove.
384 : jsr166 1.56 *
385 : dl 1.55 * @param o element to be removed from this queue, if present
386 : jsr166 1.63 * @return {@code true} if removed
387 : dl 1.55 */
388 :     boolean removeEq(Object o) {
389 : jsr166 1.68 for (int i = 0; i < size; i++) {
390 :     if (o == queue[i]) {
391 : dl 1.55 removeAt(i);
392 :     return true;
393 :     }
394 :     }
395 :     return false;
396 :     }
397 :    
398 : dholmes 1.11 /**
399 : jsr166 1.63 * Returns {@code true} if this queue contains the specified element.
400 :     * More formally, returns {@code true} if and only if this queue contains
401 :     * at least one element {@code e} such that {@code o.equals(e)}.
402 : dholmes 1.23 *
403 : dl 1.52 * @param o object to be checked for containment in this queue
404 : jsr166 1.63 * @return {@code true} if this queue contains the specified element
405 : dholmes 1.11 */
406 : dl 1.52 public boolean contains(Object o) {
407 : jsr166 1.100 return indexOf(o) >= 0;
408 : tim 1.14 }
409 : dholmes 1.11
410 : dl 1.49 /**
411 : jsr166 1.63 * Returns an array containing all of the elements in this queue.
412 : dl 1.52 * The elements are in no particular order.
413 :     *
414 :     * <p>The returned array will be "safe" in that no references to it are
415 : jsr166 1.63 * maintained by this queue. (In other words, this method must allocate
416 : dl 1.52 * a new array). The caller is thus free to modify the returned array.
417 :     *
418 : jsr166 1.63 * <p>This method acts as bridge between array-based and collection-based
419 :     * APIs.
420 :     *
421 : jsr166 1.59 * @return an array containing all of the elements in this queue
422 : dl 1.49 */
423 : dl 1.52 public Object[] toArray() {
424 : dl 1.55 return Arrays.copyOf(queue, size);
425 : dl 1.52 }
426 : tim 1.2
427 : dl 1.52 /**
428 : jsr166 1.63 * Returns an array containing all of the elements in this queue; the
429 :     * runtime type of the returned array is that of the specified array.
430 :     * The returned array elements are in no particular order.
431 :     * If the queue fits in the specified array, it is returned therein.
432 :     * Otherwise, a new array is allocated with the runtime type of the
433 :     * specified array and the size of this queue.
434 : dl 1.52 *
435 :     * <p>If the queue fits in the specified array with room to spare
436 :     * (i.e., the array has more elements than the queue), the element in
437 :     * the array immediately following the end of the collection is set to
438 : jsr166 1.63 * {@code null}.
439 :     *
440 :     * <p>Like the {@link #toArray()} method, this method acts as bridge between
441 :     * array-based and collection-based APIs. Further, this method allows
442 :     * precise control over the runtime type of the output array, and may,
443 :     * under certain circumstances, be used to save allocation costs.
444 :     *
445 : jsr166 1.80 * <p>Suppose {@code x} is a queue known to contain only strings.
446 : jsr166 1.63 * The following code can be used to dump the queue into a newly
447 : jsr166 1.80 * allocated array of {@code String}:
448 : jsr166 1.63 *
449 : jsr166 1.104 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
450 : jsr166 1.63 *
451 : jsr166 1.80 * Note that {@code toArray(new Object[0])} is identical in function to
452 :     * {@code toArray()}.
453 : dl 1.52 *
454 :     * @param a the array into which the elements of the queue are to
455 :     * be stored, if it is big enough; otherwise, a new array of the
456 :     * same runtime type is allocated for this purpose.
457 : jsr166 1.63 * @return an array containing all of the elements in this queue
458 : dl 1.52 * @throws ArrayStoreException if the runtime type of the specified array
459 :     * is not a supertype of the runtime type of every element in
460 :     * this queue
461 :     * @throws NullPointerException if the specified array is null
462 :     */
463 : jsr166 1.84 @SuppressWarnings("unchecked")
464 : dl 1.52 public <T> T[] toArray(T[] a) {
465 : jsr166 1.85 final int size = this.size;
466 : dl 1.52 if (a.length < size)
467 :     // Make a new array of a's runtime type, but my contents:
468 : dl 1.55 return (T[]) Arrays.copyOf(queue, size, a.getClass());
469 : jsr166 1.68 System.arraycopy(queue, 0, a, 0, size);
470 : dl 1.52 if (a.length > size)
471 :     a[size] = null;
472 :     return a;
473 : tim 1.1 }
474 : tim 1.2
475 : dholmes 1.23 /**
476 :     * Returns an iterator over the elements in this queue. The iterator
477 :     * does not return the elements in any particular order.
478 :     *
479 : dl 1.52 * @return an iterator over the elements in this queue
480 : dholmes 1.23 */
481 : tim 1.2 public Iterator<E> iterator() {
482 : dl 1.7 return new Itr();
483 : tim 1.2 }
484 :    
485 : dl 1.55 private final class Itr implements Iterator<E> {
486 : dl 1.7 /**
487 :     * Index (into queue array) of element to be returned by
488 : tim 1.2 * subsequent call to next.
489 : dl 1.7 */
490 : jsr166 1.99 private int cursor;
491 : tim 1.2
492 : dl 1.7 /**
493 : dl 1.36 * Index of element returned by most recent call to next,
494 :     * unless that element came from the forgetMeNot list.
495 : dl 1.55 * Set to -1 if element is deleted by a call to remove.
496 : dl 1.7 */
497 : dl 1.55 private int lastRet = -1;
498 : dl 1.7
499 :     /**
500 : dl 1.55 * A queue of elements that were moved from the unvisited portion of
501 : dl 1.36 * the heap into the visited portion as a result of "unlucky" element
502 :     * removals during the iteration. (Unlucky element removals are those
503 : dl 1.55 * that require a siftup instead of a siftdown.) We must visit all of
504 : dl 1.36 * the elements in this list to complete the iteration. We do this
505 :     * after we've completed the "normal" iteration.
506 :     *
507 :     * We expect that most iterations, even those involving removals,
508 : jsr166 1.63 * will not need to store elements in this field.
509 : dl 1.36 */
510 : jsr166 1.99 private ArrayDeque<E> forgetMeNot;
511 : dl 1.36
512 :     /**
513 :     * Element returned by the most recent call to next iff that
514 :     * element was drawn from the forgetMeNot list.
515 :     */
516 : jsr166 1.99 private E lastRetElt;
517 : dl 1.55
518 :     /**
519 :     * The modCount value that the iterator believes that the backing
520 : jsr166 1.63 * Queue should have. If this expectation is violated, the iterator
521 : dl 1.55 * has detected concurrent modification.
522 :     */
523 :     private int expectedModCount = modCount;
524 : dl 1.35
525 : dl 1.7 public boolean hasNext() {
526 : jsr166 1.56 return cursor < size ||
527 : dl 1.55 (forgetMeNot != null && !forgetMeNot.isEmpty());
528 : dl 1.7 }
529 :    
530 : dl 1.81 @SuppressWarnings("unchecked")
531 : dl 1.7 public E next() {
532 : dl 1.55 if (expectedModCount != modCount)
533 :     throw new ConcurrentModificationException();
534 : jsr166 1.56 if (cursor < size)
535 : dl 1.55 return (E) queue[lastRet = cursor++];
536 :     if (forgetMeNot != null) {
537 :     lastRet = -1;
538 :     lastRetElt = forgetMeNot.poll();
539 : jsr166 1.56 if (lastRetElt != null)
540 : dl 1.55 return lastRetElt;
541 : dl 1.36 }
542 : dl 1.55 throw new NoSuchElementException();
543 : dl 1.7 }
544 : tim 1.2
545 : dl 1.7 public void remove() {
546 : dl 1.55 if (expectedModCount != modCount)
547 :     throw new ConcurrentModificationException();
548 :     if (lastRet != -1) {
549 : dl 1.36 E moved = PriorityQueue.this.removeAt(lastRet);
550 : dl 1.55 lastRet = -1;
551 : jsr166 1.56 if (moved == null)
552 : dl 1.36 cursor--;
553 : dl 1.55 else {
554 : dl 1.36 if (forgetMeNot == null)
555 : dl 1.89 forgetMeNot = new ArrayDeque<>();
556 : dl 1.36 forgetMeNot.add(moved);
557 : jsr166 1.56 }
558 : jsr166 1.63 } else if (lastRetElt != null) {
559 : dl 1.55 PriorityQueue.this.removeEq(lastRetElt);
560 : dl 1.36 lastRetElt = null;
561 : jsr166 1.63 } else {
562 :     throw new IllegalStateException();
563 : jsr166 1.68 }
564 : tim 1.2 expectedModCount = modCount;
565 : dl 1.7 }
566 : tim 1.2 }
567 :    
568 : tim 1.1 public int size() {
569 : tim 1.2 return size;
570 : tim 1.1 }
571 : tim 1.2
572 :     /**
573 : dl 1.52 * Removes all of the elements from this priority queue.
574 : dl 1.49 * The queue will be empty after this call returns.
575 : tim 1.2 */
576 :     public void clear() {
577 :     modCount++;
578 : dl 1.55 for (int i = 0; i < size; i++)
579 : tim 1.2 queue[i] = null;
580 :     size = 0;
581 :     }
582 :    
583 : dl 1.81 @SuppressWarnings("unchecked")
584 : dl 1.40 public E poll() {
585 : dl 1.36 if (size == 0)
586 : dl 1.40 return null;
587 : dl 1.55 int s = --size;
588 : dl 1.36 modCount++;
589 : jsr166 1.63 E result = (E) queue[0];
590 :     E x = (E) queue[s];
591 : dl 1.55 queue[s] = null;
592 :     if (s != 0)
593 :     siftDown(0, x);
594 : dl 1.36 return result;
595 :     }
596 :    
597 :     /**
598 : dl 1.55 * Removes the ith element from queue.
599 : tim 1.2 *
600 : dl 1.55 * Normally this method leaves the elements at up to i-1,
601 :     * inclusive, untouched. Under these circumstances, it returns
602 :     * null. Occasionally, in order to maintain the heap invariant,
603 :     * it must swap a later element of the list with one earlier than
604 :     * i. Under these circumstances, this method returns the element
605 :     * that was previously at the end of the list and is now at some
606 :     * position before i. This fact is used by iterator.remove so as to
607 : jsr166 1.63 * avoid missing traversing elements.
608 : tim 1.2 */
609 : dl 1.81 @SuppressWarnings("unchecked")
610 : jsr166 1.107 E removeAt(int i) {
611 : jsr166 1.74 // assert i >= 0 && i < size;
612 : tim 1.2 modCount++;
613 : dl 1.55 int s = --size;
614 :     if (s == i) // removed last element
615 :     queue[i] = null;
616 :     else {
617 :     E moved = (E) queue[s];
618 : jsr166 1.56 queue[s] = null;
619 : dl 1.55 siftDown(i, moved);
620 : dl 1.36 if (queue[i] == moved) {
621 : dl 1.55 siftUp(i, moved);
622 : dl 1.36 if (queue[i] != moved)
623 :     return moved;
624 :     }
625 : dl 1.35 }
626 : dl 1.36 return null;
627 : tim 1.1 }
628 :    
629 : tim 1.2 /**
630 : dl 1.55 * Inserts item x at position k, maintaining heap invariant by
631 :     * promoting x up the tree until it is greater than or equal to
632 :     * its parent, or is the root.
633 :     *
634 :     * To simplify and speed up coercions and comparisons. the
635 :     * Comparable and Comparator versions are separated into different
636 :     * methods that are otherwise identical. (Similarly for siftDown.)
637 : jsr166 1.56 *
638 : dl 1.55 * @param k the position to fill
639 :     * @param x the item to insert
640 :     */
641 :     private void siftUp(int k, E x) {
642 : jsr166 1.56 if (comparator != null)
643 : dl 1.55 siftUpUsingComparator(k, x);
644 :     else
645 :     siftUpComparable(k, x);
646 :     }
647 :    
648 : dl 1.81 @SuppressWarnings("unchecked")
649 : dl 1.55 private void siftUpComparable(int k, E x) {
650 :     Comparable<? super E> key = (Comparable<? super E>) x;
651 :     while (k > 0) {
652 :     int parent = (k - 1) >>> 1;
653 :     Object e = queue[parent];
654 : jsr166 1.63 if (key.compareTo((E) e) >= 0)
655 : dl 1.55 break;
656 :     queue[k] = e;
657 :     k = parent;
658 :     }
659 :     queue[k] = key;
660 :     }
661 :    
662 : dl 1.81 @SuppressWarnings("unchecked")
663 : dl 1.55 private void siftUpUsingComparator(int k, E x) {
664 :     while (k > 0) {
665 :     int parent = (k - 1) >>> 1;
666 :     Object e = queue[parent];
667 : jsr166 1.63 if (comparator.compare(x, (E) e) >= 0)
668 : dl 1.55 break;
669 :     queue[k] = e;
670 :     k = parent;
671 :     }
672 :     queue[k] = x;
673 :     }
674 :    
675 :     /**
676 :     * Inserts item x at position k, maintaining heap invariant by
677 :     * demoting x down the tree repeatedly until it is less than or
678 :     * equal to its children or is a leaf.
679 :     *
680 :     * @param k the position to fill
681 :     * @param x the item to insert
682 :     */
683 :     private void siftDown(int k, E x) {
684 : jsr166 1.56 if (comparator != null)
685 : dl 1.55 siftDownUsingComparator(k, x);
686 :     else
687 :     siftDownComparable(k, x);
688 :     }
689 :    
690 : dl 1.81 @SuppressWarnings("unchecked")
691 : dl 1.55 private void siftDownComparable(int k, E x) {
692 :     Comparable<? super E> key = (Comparable<? super E>)x;
693 :     int half = size >>> 1; // loop while a non-leaf
694 :     while (k < half) {
695 :     int child = (k << 1) + 1; // assume left child is least
696 :     Object c = queue[child];
697 :     int right = child + 1;
698 :     if (right < size &&
699 : jsr166 1.63 ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
700 : dl 1.55 c = queue[child = right];
701 : jsr166 1.63 if (key.compareTo((E) c) <= 0)
702 : dl 1.55 break;
703 :     queue[k] = c;
704 :     k = child;
705 :     }
706 :     queue[k] = key;
707 :     }
708 :    
709 : dl 1.81 @SuppressWarnings("unchecked")
710 : dl 1.55 private void siftDownUsingComparator(int k, E x) {
711 :     int half = size >>> 1;
712 :     while (k < half) {
713 :     int child = (k << 1) + 1;
714 :     Object c = queue[child];
715 :     int right = child + 1;
716 :     if (right < size &&
717 : jsr166 1.63 comparator.compare((E) c, (E) queue[right]) > 0)
718 : jsr166 1.56 c = queue[child = right];
719 : jsr166 1.63 if (comparator.compare(x, (E) c) <= 0)
720 : dl 1.55 break;
721 :     queue[k] = c;
722 :     k = child;
723 : tim 1.2 }
724 : dl 1.55 queue[k] = x;
725 : dl 1.36 }
726 : dl 1.35
727 : dl 1.36 /**
728 :     * Establishes the heap invariant (described above) in the entire tree,
729 :     * assuming nothing about the order of the elements prior to the call.
730 : jsr166 1.112 * This classic algorithm due to Floyd (1964) is known to be O(size).
731 : dl 1.36 */
732 : dl 1.81 @SuppressWarnings("unchecked")
733 : dl 1.36 private void heapify() {
734 : jsr166 1.56 for (int i = (size >>> 1) - 1; i >= 0; i--)
735 : jsr166 1.63 siftDown(i, (E) queue[i]);
736 : tim 1.2 }
737 :    
738 : dholmes 1.23 /**
739 : dl 1.52 * Returns the comparator used to order the elements in this
740 : jsr166 1.63 * queue, or {@code null} if this queue is sorted according to
741 : dl 1.52 * the {@linkplain Comparable natural ordering} of its elements.
742 :     *
743 :     * @return the comparator used to order this queue, or
744 : jsr166 1.63 * {@code null} if this queue is sorted according to the
745 :     * natural ordering of its elements
746 : dholmes 1.23 */
747 : tim 1.16 public Comparator<? super E> comparator() {
748 : tim 1.2 return comparator;
749 :     }
750 : dl 1.5
751 :     /**
752 : jsr166 1.77 * Saves this queue to a stream (that is, serializes it).
753 : dl 1.5 *
754 : jsr166 1.110 * @param s the stream
755 :     * @throws java.io.IOException if an I/O error occurs
756 : dl 1.5 * @serialData The length of the array backing the instance is
757 : jsr166 1.63 * emitted (int), followed by all of its elements
758 :     * (each an {@code Object}) in the proper order.
759 : dl 1.5 */
760 : dl 1.22 private void writeObject(java.io.ObjectOutputStream s)
761 : jsr166 1.75 throws java.io.IOException {
762 : dl 1.7 // Write out element count, and any hidden stuff
763 :     s.defaultWriteObject();
764 : dl 1.5
765 : jsr166 1.63 // Write out array length, for compatibility with 1.5 version
766 :     s.writeInt(Math.max(2, size + 1));
767 : dl 1.5
768 : jsr166 1.64 // Write out all elements in the "proper order".
769 : jsr166 1.63 for (int i = 0; i < size; i++)
770 : dl 1.5 s.writeObject(queue[i]);
771 :     }
772 :    
773 :     /**
774 : dl 1.81 * Reconstitutes the {@code PriorityQueue} instance from a stream
775 :     * (that is, deserializes it).
776 :     *
777 :     * @param s the stream
778 : jsr166 1.97 * @throws ClassNotFoundException if the class of a serialized object
779 :     * could not be found
780 :     * @throws java.io.IOException if an I/O error occurs
781 : dl 1.5 */
782 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
783 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
784 : dl 1.7 // Read in size, and any hidden stuff
785 :     s.defaultReadObject();
786 : dl 1.5
787 : jsr166 1.63 // Read in (and discard) array length
788 :     s.readInt();
789 :    
790 : jsr166 1.68 queue = new Object[size];
791 : dl 1.5
792 : jsr166 1.64 // Read in all elements.
793 : jsr166 1.63 for (int i = 0; i < size; i++)
794 :     queue[i] = s.readObject();
795 : jsr166 1.64
796 : jsr166 1.68 // Elements are guaranteed to be in "proper order", but the
797 :     // spec has never explained what that might be.
798 :     heapify();
799 : dl 1.5 }
800 : dl 1.81
801 : jsr166 1.106 /**
802 :     * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
803 :     * and <em>fail-fast</em> {@link Spliterator} over the elements in this
804 : jsr166 1.111 * queue. The spliterator does not traverse elements in any particular order
805 :     * (the {@link Spliterator#ORDERED ORDERED} characteristic is not reported).
806 : jsr166 1.106 *
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 1.108 /** 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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