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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 1.81 import java.util.stream.Stream;
28 :     import java.util.Spliterator;
29 :     import java.util.stream.Streams;
30 :     import java.util.function.Block;
31 : tim 1.1
32 :     /**
33 : jsr166 1.63 * An unbounded priority {@linkplain Queue queue} based on a priority heap.
34 :     * The elements of the priority queue are ordered according to their
35 :     * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
36 :     * provided at queue construction time, depending on which constructor is
37 :     * used. A priority queue does not permit {@code null} elements.
38 :     * A priority queue relying on natural ordering also does not permit
39 :     * insertion of non-comparable objects (doing so may result in
40 :     * {@code ClassCastException}).
41 : dl 1.40 *
42 : dl 1.41 * <p>The <em>head</em> of this queue is the <em>least</em> element
43 :     * with respect to the specified ordering. If multiple elements are
44 :     * tied for least value, the head is one of those elements -- ties are
45 : jsr166 1.63 * broken arbitrarily. The queue retrieval operations {@code poll},
46 :     * {@code remove}, {@code peek}, and {@code element} access the
47 : dl 1.42 * element at the head of the queue.
48 : tim 1.14 *
49 : dl 1.41 * <p>A priority queue is unbounded, but has an internal
50 :     * <i>capacity</i> governing the size of an array used to store the
51 : dl 1.40 * elements on the queue. It is always at least as large as the queue
52 :     * size. As elements are added to a priority queue, its capacity
53 :     * grows automatically. The details of the growth policy are not
54 :     * specified.
55 : tim 1.2 *
56 : dl 1.50 * <p>This class and its iterator implement all of the
57 :     * <em>optional</em> methods of the {@link Collection} and {@link
58 : dl 1.52 * Iterator} interfaces. The Iterator provided in method {@link
59 :     * #iterator()} is <em>not</em> guaranteed to traverse the elements of
60 :     * the priority queue in any particular order. If you need ordered
61 : jsr166 1.63 * traversal, consider using {@code Arrays.sort(pq.toArray())}.
62 : dl 1.29 *
63 : jsr166 1.82 * <p><strong>Note that this implementation is not synchronized.</strong>
64 : jsr166 1.63 * Multiple threads should not access a {@code PriorityQueue}
65 :     * instance concurrently if any of the threads modifies the queue.
66 :     * Instead, use the thread-safe {@link
67 : dholmes 1.34 * java.util.concurrent.PriorityBlockingQueue} class.
68 : dl 1.29 *
69 : jsr166 1.63 * <p>Implementation note: this implementation provides
70 : dl 1.81 * O(log(n)) time for the enqueing and dequeing methods
71 : jsr166 1.63 * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
72 :     * linear time for the {@code remove(Object)} and {@code contains(Object)}
73 :     * methods; and constant time for the retrieval methods
74 :     * ({@code peek}, {@code element}, and {@code size}).
75 : tim 1.2 *
76 :     * <p>This class is a member of the
77 : jsr166 1.65 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
78 : tim 1.2 * Java Collections Framework</a>.
79 : jsr166 1.63 *
80 : dl 1.7 * @since 1.5
81 : jsr166 1.63 * @author Josh Bloch, Doug Lea
82 : dl 1.45 * @param <E> the type of elements held in this collection
83 : tim 1.2 */
84 :     public class PriorityQueue<E> extends AbstractQueue<E>
85 : dl 1.47 implements java.io.Serializable {
86 : dholmes 1.11
87 : dl 1.31 private static final long serialVersionUID = -7720805057305804111L;
88 : dl 1.30
89 : tim 1.2 private static final int DEFAULT_INITIAL_CAPACITY = 11;
90 : tim 1.1
91 : tim 1.2 /**
92 : dl 1.55 * Priority queue represented as a balanced binary heap: the two
93 :     * children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The
94 :     * priority queue is ordered by comparator, or by the elements'
95 :     * natural ordering, if comparator is null: For each node n in the
96 :     * heap and each descendant d of n, n <= d. The element with the
97 :     * lowest value is in queue[0], assuming the queue is nonempty.
98 : tim 1.2 */
99 : dl 1.81 transient Object[] queue; // non-private to simplify nested class access
100 : tim 1.1
101 : tim 1.2 /**
102 :     * The number of elements in the priority queue.
103 :     */
104 :     private int size = 0;
105 : tim 1.1
106 : tim 1.2 /**
107 :     * The comparator, or null if priority queue uses elements'
108 :     * natural ordering.
109 :     */
110 : tim 1.16 private final Comparator<? super E> comparator;
111 : tim 1.2
112 :     /**
113 :     * The number of times this priority queue has been
114 :     * <i>structurally modified</i>. See AbstractList for gory details.
115 :     */
116 : dl 1.81 transient int modCount = 0; // non-private to simplify nested class access
117 : tim 1.2
118 :     /**
119 : jsr166 1.63 * Creates a {@code PriorityQueue} with the default initial
120 : dl 1.52 * capacity (11) that orders its elements according to their
121 :     * {@linkplain Comparable natural ordering}.
122 : tim 1.2 */
123 :     public PriorityQueue() {
124 : dholmes 1.11 this(DEFAULT_INITIAL_CAPACITY, null);
125 : tim 1.1 }
126 : tim 1.2
127 :     /**
128 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial
129 : dl 1.52 * capacity that orders its elements according to their
130 :     * {@linkplain Comparable natural ordering}.
131 : tim 1.2 *
132 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
133 : jsr166 1.63 * @throws IllegalArgumentException if {@code initialCapacity} is less
134 :     * than 1
135 : tim 1.2 */
136 :     public PriorityQueue(int initialCapacity) {
137 :     this(initialCapacity, null);
138 : tim 1.1 }
139 : tim 1.2
140 :     /**
141 : jsr166 1.63 * Creates a {@code PriorityQueue} with the specified initial capacity
142 : tim 1.2 * that orders its elements according to the specified comparator.
143 :     *
144 : dl 1.52 * @param initialCapacity the initial capacity for this priority queue
145 : jsr166 1.63 * @param comparator the comparator that will be used to order this
146 :     * priority queue. If {@code null}, the {@linkplain Comparable
147 :     * natural ordering} of the elements will be used.
148 :     * @throws IllegalArgumentException if {@code initialCapacity} is
149 : dl 1.52 * less than 1
150 : tim 1.2 */
151 : dl 1.52 public PriorityQueue(int initialCapacity,
152 : dholmes 1.23 Comparator<? super E> comparator) {
153 : dl 1.55 // Note: This restriction of at least one is not actually needed,
154 :     // but continues for 1.5 compatibility
155 : tim 1.2 if (initialCapacity < 1)
156 : dholmes 1.15 throw new IllegalArgumentException();
157 : dl 1.55 this.queue = new Object[initialCapacity];
158 : tim 1.2 this.comparator = comparator;
159 : tim 1.1 }
160 : jsr166 1.56
161 : dl 1.22 /**
162 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
163 :     * specified collection. If the specified collection is an instance of
164 :     * a {@link SortedSet} or is another {@code PriorityQueue}, this
165 :     * priority queue will be ordered according to the same ordering.
166 :     * Otherwise, this priority queue will be ordered according to the
167 :     * {@linkplain Comparable natural ordering} of its elements.
168 : tim 1.2 *
169 : dl 1.52 * @param c the collection whose elements are to be placed
170 :     * into this priority queue
171 : tim 1.2 * @throws ClassCastException if elements of the specified collection
172 :     * cannot be compared to one another according to the priority
173 : dl 1.52 * queue's ordering
174 :     * @throws NullPointerException if the specified collection or any
175 :     * of its elements are null
176 : tim 1.2 */
177 : jsr166 1.70 @SuppressWarnings("unchecked")
178 : tim 1.16 public PriorityQueue(Collection<? extends E> c) {
179 : jsr166 1.70 if (c instanceof SortedSet<?>) {
180 :     SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
181 :     this.comparator = (Comparator<? super E>) ss.comparator();
182 :     initElementsFromCollection(ss);
183 :     }
184 :     else if (c instanceof PriorityQueue<?>) {
185 :     PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
186 :     this.comparator = (Comparator<? super E>) pq.comparator();
187 :     initFromPriorityQueue(pq);
188 :     }
189 : dl 1.55 else {
190 : jsr166 1.70 this.comparator = null;
191 :     initFromCollection(c);
192 : tim 1.2 }
193 : dl 1.22 }
194 :    
195 :     /**
196 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
197 : dl 1.55 * specified priority queue. This priority queue will be
198 : dl 1.52 * ordered according to the same ordering as the given priority
199 :     * queue.
200 :     *
201 :     * @param c the priority queue whose elements are to be placed
202 :     * into this priority queue
203 : jsr166 1.63 * @throws ClassCastException if elements of {@code c} cannot be
204 :     * compared to one another according to {@code c}'s
205 : dl 1.52 * ordering
206 :     * @throws NullPointerException if the specified priority queue or any
207 :     * of its elements are null
208 : dl 1.22 */
209 : jsr166 1.70 @SuppressWarnings("unchecked")
210 : dl 1.22 public PriorityQueue(PriorityQueue<? extends E> c) {
211 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
212 :     initFromPriorityQueue(c);
213 : dl 1.22 }
214 : dholmes 1.18
215 : dl 1.22 /**
216 : jsr166 1.63 * Creates a {@code PriorityQueue} containing the elements in the
217 :     * specified sorted set. This priority queue will be ordered
218 : dl 1.52 * according to the same ordering as the given sorted set.
219 :     *
220 :     * @param c the sorted set whose elements are to be placed
221 : jsr166 1.63 * into this priority queue
222 : dl 1.52 * @throws ClassCastException if elements of the specified sorted
223 :     * set cannot be compared to one another according to the
224 :     * sorted set's ordering
225 :     * @throws NullPointerException if the specified sorted set or any
226 :     * of its elements are null
227 : dl 1.22 */
228 : jsr166 1.70 @SuppressWarnings("unchecked")
229 : dl 1.22 public PriorityQueue(SortedSet<? extends E> c) {
230 : jsr166 1.70 this.comparator = (Comparator<? super E>) c.comparator();
231 :     initElementsFromCollection(c);
232 :     }
233 :    
234 :     private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
235 :     if (c.getClass() == PriorityQueue.class) {
236 :     this.queue = c.toArray();
237 :     this.size = c.size();
238 :     } else {
239 :     initFromCollection(c);
240 :     }
241 :     }
242 :    
243 :     private void initElementsFromCollection(Collection<? extends E> c) {
244 :     Object[] a = c.toArray();
245 :     // If c.toArray incorrectly doesn't return Object[], copy it.
246 :     if (a.getClass() != Object[].class)
247 :     a = Arrays.copyOf(a, a.length, Object[].class);
248 :     int len = a.length;
249 :     if (len == 1 || this.comparator != null)
250 :     for (int i = 0; i < len; i++)
251 :     if (a[i] == null)
252 :     throw new NullPointerException();
253 :     this.queue = a;
254 :     this.size = a.length;
255 : tim 1.1 }
256 :    
257 : dl 1.22 /**
258 : jsr166 1.63 * Initializes queue array with elements from the given Collection.
259 :     *
260 : dl 1.55 * @param c the collection
261 : dl 1.22 */
262 : dl 1.55 private void initFromCollection(Collection<? extends E> c) {
263 : jsr166 1.70 initElementsFromCollection(c);
264 :     heapify();
265 : jsr166 1.56 }
266 : dl 1.55
267 :     /**
268 : jsr166 1.70 * The maximum size of array to allocate.
269 :     * Some VMs reserve some header words in an array.
270 :     * Attempts to allocate larger arrays may result in
271 :     * OutOfMemoryError: Requested array size exceeds VM limit
272 :     */
273 :     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
274 :    
275 :     /**
276 : dl 1.55 * Increases the capacity of the array.
277 :     *
278 :     * @param minCapacity the desired minimum capacity
279 :     */
280 :     private void grow(int minCapacity) {
281 : jsr166 1.68 int oldCapacity = queue.length;
282 : dl 1.55 // Double size if small; else grow by 50%
283 : jsr166 1.70 int newCapacity = oldCapacity + ((oldCapacity < 64) ?
284 :     (oldCapacity + 2) :
285 :     (oldCapacity >> 1));
286 :     // overflow-conscious code
287 :     if (newCapacity - MAX_ARRAY_SIZE > 0)
288 :     newCapacity = hugeCapacity(minCapacity);
289 : dl 1.55 queue = Arrays.copyOf(queue, newCapacity);
290 : dl 1.22 }
291 : dl 1.36
292 : jsr166 1.70 private static int hugeCapacity(int minCapacity) {
293 :     if (minCapacity < 0) // overflow
294 :     throw new OutOfMemoryError();
295 :     return (minCapacity > MAX_ARRAY_SIZE) ?
296 :     Integer.MAX_VALUE :
297 :     MAX_ARRAY_SIZE;
298 :     }
299 :    
300 : tim 1.2 /**
301 : dl 1.42 * Inserts the specified element into this priority queue.
302 : tim 1.2 *
303 : jsr166 1.63 * @return {@code true} (as specified by {@link Collection#add})
304 : dl 1.52 * @throws ClassCastException if the specified element cannot be
305 :     * compared with elements currently in this priority queue
306 :     * according to the priority queue's ordering
307 :     * @throws NullPointerException if the specified element is null
308 : tim 1.2 */
309 : dl 1.52 public boolean add(E e) {
310 :     return offer(e);
311 :     }
312 :    
313 :     /**
314 :     * Inserts the specified element into this priority queue.
315 :     *
316 : jsr166 1.63 * @return {@code true} (as specified by {@link Queue#offer})
317 : dl 1.52 * @throws ClassCastException if the specified element cannot be
318 :     * compared with elements currently in this priority queue
319 :     * according to the priority queue's ordering
320 :     * @throws NullPointerException if the specified element is null
321 :     */
322 :     public boolean offer(E e) {
323 :     if (e == null)
324 : dholmes 1.11 throw new NullPointerException();
325 :     modCount++;
326 : dl 1.55 int i = size;
327 :     if (i >= queue.length)
328 :     grow(i + 1);
329 :     size = i + 1;
330 :     if (i == 0)
331 :     queue[0] = e;
332 :     else
333 :     siftUp(i, e);
334 : dholmes 1.11 return true;
335 :     }
336 :    
337 : dl 1.81 @SuppressWarnings("unchecked")
338 : dl 1.40 public E peek() {
339 : jsr166 1.73 return (size == 0) ? null : (E) queue[0];
340 : tim 1.1 }
341 :    
342 : dl 1.52 private int indexOf(Object o) {
343 : jsr166 1.68 if (o != null) {
344 : dl 1.55 for (int i = 0; i < size; i++)
345 :     if (o.equals(queue[i]))
346 :     return i;
347 :     }
348 : dl 1.52 return -1;
349 :     }
350 :    
351 :     /**
352 :     * Removes a single instance of the specified element from this queue,
353 : jsr166 1.63 * if it is present. More formally, removes an element {@code e} such
354 :     * that {@code o.equals(e)}, if this queue contains one or more such
355 :     * elements. Returns {@code true} if and only if this queue contained
356 :     * the specified element (or equivalently, if this queue changed as a
357 :     * result of the call).
358 : dl 1.52 *
359 :     * @param o element to be removed from this queue, if present
360 : jsr166 1.63 * @return {@code true} if this queue changed as a result of the call
361 : dl 1.52 */
362 :     public boolean remove(Object o) {
363 : jsr166 1.68 int i = indexOf(o);
364 :     if (i == -1)
365 :     return false;
366 :     else {
367 :     removeAt(i);
368 :     return true;
369 :     }
370 : dl 1.52 }
371 : dholmes 1.11
372 : jsr166 1.56 /**
373 : dl 1.55 * Version of remove using reference equality, not equals.
374 : jsr166 1.59 * Needed by iterator.remove.
375 : jsr166 1.56 *
376 : dl 1.55 * @param o element to be removed from this queue, if present
377 : jsr166 1.63 * @return {@code true} if removed
378 : dl 1.55 */
379 :     boolean removeEq(Object o) {
380 : jsr166 1.68 for (int i = 0; i < size; i++) {
381 :     if (o == queue[i]) {
382 : dl 1.55 removeAt(i);
383 :     return true;
384 :     }
385 :     }
386 :     return false;
387 :     }
388 :    
389 : dholmes 1.11 /**
390 : jsr166 1.63 * Returns {@code true} if this queue contains the specified element.
391 :     * More formally, returns {@code true} if and only if this queue contains
392 :     * at least one element {@code e} such that {@code o.equals(e)}.
393 : dholmes 1.23 *
394 : dl 1.52 * @param o object to be checked for containment in this queue
395 : jsr166 1.63 * @return {@code true} if this queue contains the specified element
396 : dholmes 1.11 */
397 : dl 1.52 public boolean contains(Object o) {
398 : jsr166 1.68 return indexOf(o) != -1;
399 : tim 1.14 }
400 : dholmes 1.11
401 : dl 1.49 /**
402 : jsr166 1.63 * Returns an array containing all of the elements in this queue.
403 : dl 1.52 * The elements are in no particular order.
404 :     *
405 :     * <p>The returned array will be "safe" in that no references to it are
406 : jsr166 1.63 * maintained by this queue. (In other words, this method must allocate
407 : dl 1.52 * a new array). The caller is thus free to modify the returned array.
408 :     *
409 : jsr166 1.63 * <p>This method acts as bridge between array-based and collection-based
410 :     * APIs.
411 :     *
412 : jsr166 1.59 * @return an array containing all of the elements in this queue
413 : dl 1.49 */
414 : dl 1.52 public Object[] toArray() {
415 : dl 1.55 return Arrays.copyOf(queue, size);
416 : dl 1.52 }
417 : tim 1.2
418 : dl 1.52 /**
419 : jsr166 1.63 * Returns an array containing all of the elements in this queue; the
420 :     * runtime type of the returned array is that of the specified array.
421 :     * The returned array elements are in no particular order.
422 :     * If the queue fits in the specified array, it is returned therein.
423 :     * Otherwise, a new array is allocated with the runtime type of the
424 :     * specified array and the size of this queue.
425 : dl 1.52 *
426 :     * <p>If the queue fits in the specified array with room to spare
427 :     * (i.e., the array has more elements than the queue), the element in
428 :     * the array immediately following the end of the collection is set to
429 : jsr166 1.63 * {@code null}.
430 :     *
431 :     * <p>Like the {@link #toArray()} method, this method acts as bridge between
432 :     * array-based and collection-based APIs. Further, this method allows
433 :     * precise control over the runtime type of the output array, and may,
434 :     * under certain circumstances, be used to save allocation costs.
435 :     *
436 : jsr166 1.80 * <p>Suppose {@code x} is a queue known to contain only strings.
437 : jsr166 1.63 * The following code can be used to dump the queue into a newly
438 : jsr166 1.80 * allocated array of {@code String}:
439 : jsr166 1.63 *
440 : jsr166 1.72 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
441 : jsr166 1.63 *
442 : jsr166 1.80 * Note that {@code toArray(new Object[0])} is identical in function to
443 :     * {@code toArray()}.
444 : dl 1.52 *
445 :     * @param a the array into which the elements of the queue are to
446 :     * be stored, if it is big enough; otherwise, a new array of the
447 :     * same runtime type is allocated for this purpose.
448 : jsr166 1.63 * @return an array containing all of the elements in this queue
449 : dl 1.52 * @throws ArrayStoreException if the runtime type of the specified array
450 :     * is not a supertype of the runtime type of every element in
451 :     * this queue
452 :     * @throws NullPointerException if the specified array is null
453 :     */
454 : jsr166 1.84 @SuppressWarnings("unchecked")
455 : dl 1.52 public <T> T[] toArray(T[] a) {
456 : jsr166 1.85 final int size = this.size;
457 : dl 1.52 if (a.length < size)
458 :     // Make a new array of a's runtime type, but my contents:
459 : dl 1.55 return (T[]) Arrays.copyOf(queue, size, a.getClass());
460 : jsr166 1.68 System.arraycopy(queue, 0, a, 0, size);
461 : dl 1.52 if (a.length > size)
462 :     a[size] = null;
463 :     return a;
464 : tim 1.1 }
465 : tim 1.2
466 : dholmes 1.23 /**
467 :     * Returns an iterator over the elements in this queue. The iterator
468 :     * does not return the elements in any particular order.
469 :     *
470 : dl 1.52 * @return an iterator over the elements in this queue
471 : dholmes 1.23 */
472 : tim 1.2 public Iterator<E> iterator() {
473 : dl 1.7 return new Itr();
474 : tim 1.2 }
475 :    
476 : dl 1.55 private final class Itr implements Iterator<E> {
477 : dl 1.7 /**
478 :     * Index (into queue array) of element to be returned by
479 : tim 1.2 * subsequent call to next.
480 : dl 1.7 */
481 : dl 1.55 private int cursor = 0;
482 : tim 1.2
483 : dl 1.7 /**
484 : dl 1.36 * Index of element returned by most recent call to next,
485 :     * unless that element came from the forgetMeNot list.
486 : dl 1.55 * Set to -1 if element is deleted by a call to remove.
487 : dl 1.7 */
488 : dl 1.55 private int lastRet = -1;
489 : dl 1.7
490 :     /**
491 : dl 1.55 * A queue of elements that were moved from the unvisited portion of
492 : dl 1.36 * the heap into the visited portion as a result of "unlucky" element
493 :     * removals during the iteration. (Unlucky element removals are those
494 : dl 1.55 * that require a siftup instead of a siftdown.) We must visit all of
495 : dl 1.36 * the elements in this list to complete the iteration. We do this
496 :     * after we've completed the "normal" iteration.
497 :     *
498 :     * We expect that most iterations, even those involving removals,
499 : jsr166 1.63 * will not need to store elements in this field.
500 : dl 1.36 */
501 : dl 1.55 private ArrayDeque<E> forgetMeNot = null;
502 : dl 1.36
503 :     /**
504 :     * Element returned by the most recent call to next iff that
505 :     * element was drawn from the forgetMeNot list.
506 :     */
507 : dl 1.55 private E lastRetElt = null;
508 :    
509 :     /**
510 :     * The modCount value that the iterator believes that the backing
511 : jsr166 1.63 * Queue should have. If this expectation is violated, the iterator
512 : dl 1.55 * has detected concurrent modification.
513 :     */
514 :     private int expectedModCount = modCount;
515 : dl 1.35
516 : dl 1.7 public boolean hasNext() {
517 : jsr166 1.56 return cursor < size ||
518 : dl 1.55 (forgetMeNot != null && !forgetMeNot.isEmpty());
519 : dl 1.7 }
520 :    
521 : dl 1.81 @SuppressWarnings("unchecked")
522 : dl 1.7 public E next() {
523 : dl 1.55 if (expectedModCount != modCount)
524 :     throw new ConcurrentModificationException();
525 : jsr166 1.56 if (cursor < size)
526 : dl 1.55 return (E) queue[lastRet = cursor++];
527 :     if (forgetMeNot != null) {
528 :     lastRet = -1;
529 :     lastRetElt = forgetMeNot.poll();
530 : jsr166 1.56 if (lastRetElt != null)
531 : dl 1.55 return lastRetElt;
532 : dl 1.36 }
533 : dl 1.55 throw new NoSuchElementException();
534 : dl 1.7 }
535 : tim 1.2
536 : dl 1.7 public void remove() {
537 : dl 1.55 if (expectedModCount != modCount)
538 :     throw new ConcurrentModificationException();
539 :     if (lastRet != -1) {
540 : dl 1.36 E moved = PriorityQueue.this.removeAt(lastRet);
541 : dl 1.55 lastRet = -1;
542 : jsr166 1.56 if (moved == null)
543 : dl 1.36 cursor--;
544 : dl 1.55 else {
545 : dl 1.36 if (forgetMeNot == null)
546 : dl 1.55 forgetMeNot = new ArrayDeque<E>();
547 : dl 1.36 forgetMeNot.add(moved);
548 : jsr166 1.56 }
549 : jsr166 1.63 } else if (lastRetElt != null) {
550 : dl 1.55 PriorityQueue.this.removeEq(lastRetElt);
551 : dl 1.36 lastRetElt = null;
552 : jsr166 1.63 } else {
553 :     throw new IllegalStateException();
554 : jsr166 1.68 }
555 : tim 1.2 expectedModCount = modCount;
556 : dl 1.7 }
557 : tim 1.2 }
558 :    
559 : tim 1.1 public int size() {
560 : tim 1.2 return size;
561 : tim 1.1 }
562 : tim 1.2
563 :     /**
564 : dl 1.52 * Removes all of the elements from this priority queue.
565 : dl 1.49 * The queue will be empty after this call returns.
566 : tim 1.2 */
567 :     public void clear() {
568 :     modCount++;
569 : dl 1.55 for (int i = 0; i < size; i++)
570 : tim 1.2 queue[i] = null;
571 :     size = 0;
572 :     }
573 :    
574 : dl 1.81 @SuppressWarnings("unchecked")
575 : dl 1.40 public E poll() {
576 : dl 1.36 if (size == 0)
577 : dl 1.40 return null;
578 : dl 1.55 int s = --size;
579 : dl 1.36 modCount++;
580 : jsr166 1.63 E result = (E) queue[0];
581 :     E x = (E) queue[s];
582 : dl 1.55 queue[s] = null;
583 :     if (s != 0)
584 :     siftDown(0, x);
585 : dl 1.36 return result;
586 :     }
587 :    
588 :     /**
589 : dl 1.55 * Removes the ith element from queue.
590 : tim 1.2 *
591 : dl 1.55 * Normally this method leaves the elements at up to i-1,
592 :     * inclusive, untouched. Under these circumstances, it returns
593 :     * null. Occasionally, in order to maintain the heap invariant,
594 :     * it must swap a later element of the list with one earlier than
595 :     * i. Under these circumstances, this method returns the element
596 :     * that was previously at the end of the list and is now at some
597 :     * position before i. This fact is used by iterator.remove so as to
598 : jsr166 1.63 * avoid missing traversing elements.
599 : tim 1.2 */
600 : dl 1.81 @SuppressWarnings("unchecked")
601 : dl 1.52 private E removeAt(int i) {
602 : jsr166 1.74 // assert i >= 0 && i < size;
603 : tim 1.2 modCount++;
604 : dl 1.55 int s = --size;
605 :     if (s == i) // removed last element
606 :     queue[i] = null;
607 :     else {
608 :     E moved = (E) queue[s];
609 : jsr166 1.56 queue[s] = null;
610 : dl 1.55 siftDown(i, moved);
611 : dl 1.36 if (queue[i] == moved) {
612 : dl 1.55 siftUp(i, moved);
613 : dl 1.36 if (queue[i] != moved)
614 :     return moved;
615 :     }
616 : dl 1.35 }
617 : dl 1.36 return null;
618 : tim 1.1 }
619 :    
620 : tim 1.2 /**
621 : dl 1.55 * Inserts item x at position k, maintaining heap invariant by
622 :     * promoting x up the tree until it is greater than or equal to
623 :     * its parent, or is the root.
624 :     *
625 :     * To simplify and speed up coercions and comparisons. the
626 :     * Comparable and Comparator versions are separated into different
627 :     * methods that are otherwise identical. (Similarly for siftDown.)
628 : jsr166 1.56 *
629 : dl 1.55 * @param k the position to fill
630 :     * @param x the item to insert
631 :     */
632 :     private void siftUp(int k, E x) {
633 : jsr166 1.56 if (comparator != null)
634 : dl 1.55 siftUpUsingComparator(k, x);
635 :     else
636 :     siftUpComparable(k, x);
637 :     }
638 :    
639 : dl 1.81 @SuppressWarnings("unchecked")
640 : dl 1.55 private void siftUpComparable(int k, E x) {
641 :     Comparable<? super E> key = (Comparable<? super E>) x;
642 :     while (k > 0) {
643 :     int parent = (k - 1) >>> 1;
644 :     Object e = queue[parent];
645 : jsr166 1.63 if (key.compareTo((E) e) >= 0)
646 : dl 1.55 break;
647 :     queue[k] = e;
648 :     k = parent;
649 :     }
650 :     queue[k] = key;
651 :     }
652 :    
653 : dl 1.81 @SuppressWarnings("unchecked")
654 : dl 1.55 private void siftUpUsingComparator(int k, E x) {
655 :     while (k > 0) {
656 :     int parent = (k - 1) >>> 1;
657 :     Object e = queue[parent];
658 : jsr166 1.63 if (comparator.compare(x, (E) e) >= 0)
659 : dl 1.55 break;
660 :     queue[k] = e;
661 :     k = parent;
662 :     }
663 :     queue[k] = x;
664 :     }
665 :    
666 :     /**
667 :     * Inserts item x at position k, maintaining heap invariant by
668 :     * demoting x down the tree repeatedly until it is less than or
669 :     * equal to its children or is a leaf.
670 :     *
671 :     * @param k the position to fill
672 :     * @param x the item to insert
673 :     */
674 :     private void siftDown(int k, E x) {
675 : jsr166 1.56 if (comparator != null)
676 : dl 1.55 siftDownUsingComparator(k, x);
677 :     else
678 :     siftDownComparable(k, x);
679 :     }
680 :    
681 : dl 1.81 @SuppressWarnings("unchecked")
682 : dl 1.55 private void siftDownComparable(int k, E x) {
683 :     Comparable<? super E> key = (Comparable<? super E>)x;
684 :     int half = size >>> 1; // loop while a non-leaf
685 :     while (k < half) {
686 :     int child = (k << 1) + 1; // assume left child is least
687 :     Object c = queue[child];
688 :     int right = child + 1;
689 :     if (right < size &&
690 : jsr166 1.63 ((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)
691 : dl 1.55 c = queue[child = right];
692 : jsr166 1.63 if (key.compareTo((E) c) <= 0)
693 : dl 1.55 break;
694 :     queue[k] = c;
695 :     k = child;
696 :     }
697 :     queue[k] = key;
698 :     }
699 :    
700 : dl 1.81 @SuppressWarnings("unchecked")
701 : dl 1.55 private void siftDownUsingComparator(int k, E x) {
702 :     int half = size >>> 1;
703 :     while (k < half) {
704 :     int child = (k << 1) + 1;
705 :     Object c = queue[child];
706 :     int right = child + 1;
707 :     if (right < size &&
708 : jsr166 1.63 comparator.compare((E) c, (E) queue[right]) > 0)
709 : jsr166 1.56 c = queue[child = right];
710 : jsr166 1.63 if (comparator.compare(x, (E) c) <= 0)
711 : dl 1.55 break;
712 :     queue[k] = c;
713 :     k = child;
714 : tim 1.2 }
715 : dl 1.55 queue[k] = x;
716 : dl 1.36 }
717 : dl 1.35
718 : dl 1.36 /**
719 :     * Establishes the heap invariant (described above) in the entire tree,
720 :     * assuming nothing about the order of the elements prior to the call.
721 :     */
722 : dl 1.81 @SuppressWarnings("unchecked")
723 : dl 1.36 private void heapify() {
724 : jsr166 1.56 for (int i = (size >>> 1) - 1; i >= 0; i--)
725 : jsr166 1.63 siftDown(i, (E) queue[i]);
726 : tim 1.2 }
727 :    
728 : dholmes 1.23 /**
729 : dl 1.52 * Returns the comparator used to order the elements in this
730 : jsr166 1.63 * queue, or {@code null} if this queue is sorted according to
731 : dl 1.52 * the {@linkplain Comparable natural ordering} of its elements.
732 :     *
733 :     * @return the comparator used to order this queue, or
734 : jsr166 1.63 * {@code null} if this queue is sorted according to the
735 :     * natural ordering of its elements
736 : dholmes 1.23 */
737 : tim 1.16 public Comparator<? super E> comparator() {
738 : tim 1.2 return comparator;
739 :     }
740 : dl 1.5
741 :     /**
742 : jsr166 1.77 * Saves this queue to a stream (that is, serializes it).
743 : dl 1.5 *
744 :     * @serialData The length of the array backing the instance is
745 : jsr166 1.63 * emitted (int), followed by all of its elements
746 :     * (each an {@code Object}) in the proper order.
747 : dl 1.81 * @param s the stream
748 : dl 1.5 */
749 : dl 1.22 private void writeObject(java.io.ObjectOutputStream s)
750 : jsr166 1.75 throws java.io.IOException {
751 : dl 1.7 // Write out element count, and any hidden stuff
752 :     s.defaultWriteObject();
753 : dl 1.5
754 : jsr166 1.63 // Write out array length, for compatibility with 1.5 version
755 :     s.writeInt(Math.max(2, size + 1));
756 : dl 1.5
757 : jsr166 1.64 // Write out all elements in the "proper order".
758 : jsr166 1.63 for (int i = 0; i < size; i++)
759 : dl 1.5 s.writeObject(queue[i]);
760 :     }
761 :    
762 :     /**
763 : dl 1.81 * Reconstitutes the {@code PriorityQueue} instance from a stream
764 :     * (that is, deserializes it).
765 :     *
766 :     * @param s the stream
767 : dl 1.5 */
768 : dl 1.22 private void readObject(java.io.ObjectInputStream s)
769 : dl 1.5 throws java.io.IOException, ClassNotFoundException {
770 : dl 1.7 // Read in size, and any hidden stuff
771 :     s.defaultReadObject();
772 : dl 1.5
773 : jsr166 1.63 // Read in (and discard) array length
774 :     s.readInt();
775 :    
776 : jsr166 1.68 queue = new Object[size];
777 : dl 1.5
778 : jsr166 1.64 // Read in all elements.
779 : jsr166 1.63 for (int i = 0; i < size; i++)
780 :     queue[i] = s.readObject();
781 : jsr166 1.64
782 : jsr166 1.68 // Elements are guaranteed to be in "proper order", but the
783 :     // spec has never explained what that might be.
784 :     heapify();
785 : dl 1.5 }
786 : dl 1.81
787 :     // wrapping constructor in method avoids transient javac problems
788 : jsr166 1.82 final PriorityQueueSpliterator<E> spliterator(int origin, int fence,
789 : dl 1.81 int expectedModCount) {
790 : jsr166 1.83 return new PriorityQueueSpliterator<E>(this, origin, fence,
791 :     expectedModCount);
792 : dl 1.81 }
793 :    
794 :     public Stream<E> stream() {
795 :     int flags = Streams.STREAM_IS_SIZED;
796 :     return Streams.stream
797 :     (() -> spliterator(0, size, modCount), flags);
798 :     }
799 :     public Stream<E> parallelStream() {
800 :     int flags = Streams.STREAM_IS_SIZED;
801 :     return Streams.parallelStream
802 :     (() -> spliterator(0, size, modCount), flags);
803 :     }
804 :    
805 :     /** Index-based split-by-two Spliterator */
806 :     static final class PriorityQueueSpliterator<E>
807 :     implements Spliterator<E>, Iterator<E> {
808 :     private final PriorityQueue<E> pq;
809 :     private int index; // current index, modified on advance/split
810 :     private final int fence; // one past last index
811 :     private final int expectedModCount; // for comodification checks
812 :    
813 :     /** Create new spliterator covering the given range */
814 :     PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
815 :     int expectedModCount) {
816 :     this.pq = pq; this.index = origin; this.fence = fence;
817 :     this.expectedModCount = expectedModCount;
818 :     }
819 :    
820 :     public PriorityQueueSpliterator<E> trySplit() {
821 :     int lo = index, mid = (lo + fence) >>> 1;
822 :     return (lo >= mid) ? null :
823 :     new PriorityQueueSpliterator<E>(pq, lo, index = mid,
824 :     expectedModCount);
825 :     }
826 :    
827 :     public void forEach(Block<? super E> block) {
828 :     Object[] a; int i, hi; // hoist accesses and checks from loop
829 :     if (block == null)
830 :     throw new NullPointerException();
831 :     if ((a = pq.queue).length >= (hi = fence) &&
832 :     (i = index) >= 0 && i < hi) {
833 :     index = hi;
834 :     do {
835 :     @SuppressWarnings("unchecked") E e = (E) a[i];
836 :     block.accept(e);
837 :     } while (++i < hi);
838 :     if (pq.modCount != expectedModCount)
839 :     throw new ConcurrentModificationException();
840 :     }
841 :     }
842 :    
843 :     public boolean tryAdvance(Block<? super E> block) {
844 :     if (index >= 0 && index < fence) {
845 :     if (pq.modCount != expectedModCount)
846 :     throw new ConcurrentModificationException();
847 :     @SuppressWarnings("unchecked") E e =
848 :     (E)pq.queue[index++];
849 :     block.accept(e);
850 :     return true;
851 :     }
852 :     return false;
853 :     }
854 :    
855 :     public long estimateSize() { return (long)(fence - index); }
856 :     public boolean hasExactSize() { return true; }
857 :     public boolean hasExactSplits() { return true; }
858 :    
859 :     // Iterator support
860 :     public Iterator<E> iterator() { return this; }
861 :     public void remove() { throw new UnsupportedOperationException(); }
862 :     public boolean hasNext() { return index >= 0 && index < fence; }
863 :    
864 :     public E next() {
865 :     if (index < 0 || index >= fence)
866 :     throw new NoSuchElementException();
867 :     if (pq.modCount != expectedModCount)
868 :     throw new ConcurrentModificationException();
869 :     @SuppressWarnings("unchecked") E e =
870 :     (E) pq.queue[index++];
871 :     return e;
872 :     }
873 :     }
874 : tim 1.1 }

Doug Lea
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