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1 : dl 1.1 /*
2 : dl 1.47 * Written by Josh Bloch of Google Inc. and released to the public domain,
3 :     * as explained at http://creativecommons.org/publicdomain/zero/1.0/.
4 : dl 1.1 */
5 :    
6 :     package java.util;
7 : jsr166 1.61
8 : dl 1.47 import java.io.Serializable;
9 :     import java.util.function.Consumer;
10 : jsr166 1.75 import java.util.function.Predicate;
11 :     import java.util.function.UnaryOperator;
12 : dl 1.1
13 :     /**
14 :     * Resizable-array implementation of the {@link Deque} interface. Array
15 :     * deques have no capacity restrictions; they grow as necessary to support
16 :     * usage. They are not thread-safe; in the absence of external
17 :     * synchronization, they do not support concurrent access by multiple threads.
18 :     * Null elements are prohibited. This class is likely to be faster than
19 : dl 1.2 * {@link Stack} when used as a stack, and faster than {@link LinkedList}
20 : dl 1.1 * when used as a queue.
21 :     *
22 : jsr166 1.43 * <p>Most {@code ArrayDeque} operations run in amortized constant time.
23 : jsr166 1.51 * Exceptions include
24 :     * {@link #remove(Object) remove},
25 :     * {@link #removeFirstOccurrence removeFirstOccurrence},
26 :     * {@link #removeLastOccurrence removeLastOccurrence},
27 :     * {@link #contains contains},
28 :     * {@link #iterator iterator.remove()},
29 :     * and the bulk operations, all of which run in linear time.
30 : dl 1.41 *
31 : jsr166 1.51 * <p>The iterators returned by this class's {@link #iterator() iterator}
32 :     * method are <em>fail-fast</em>: If the deque is modified at any time after
33 :     * the iterator is created, in any way except through the iterator's own
34 :     * {@code remove} method, the iterator will generally throw a {@link
35 : jsr166 1.7 * ConcurrentModificationException}. Thus, in the face of concurrent
36 :     * modification, the iterator fails quickly and cleanly, rather than risking
37 :     * arbitrary, non-deterministic behavior at an undetermined time in the
38 :     * future.
39 : dl 1.1 *
40 :     * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
41 :     * as it is, generally speaking, impossible to make any hard guarantees in the
42 :     * presence of unsynchronized concurrent modification. Fail-fast iterators
43 : jsr166 1.43 * throw {@code ConcurrentModificationException} on a best-effort basis.
44 : dl 1.1 * Therefore, it would be wrong to write a program that depended on this
45 :     * exception for its correctness: <i>the fail-fast behavior of iterators
46 :     * should be used only to detect bugs.</i>
47 :     *
48 :     * <p>This class and its iterator implement all of the
49 : jsr166 1.9 * <em>optional</em> methods of the {@link Collection} and {@link
50 :     * Iterator} interfaces.
51 :     *
52 :     * <p>This class is a member of the
53 : jsr166 1.128 * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
54 : jsr166 1.9 * Java Collections Framework</a>.
55 : dl 1.1 *
56 :     * @author Josh Bloch and Doug Lea
57 : jsr166 1.74 * @param <E> the type of elements held in this deque
58 : dl 1.1 * @since 1.6
59 :     */
60 :     public class ArrayDeque<E> extends AbstractCollection<E>
61 : dl 1.47 implements Deque<E>, Cloneable, Serializable
62 : dl 1.1 {
63 : jsr166 1.106 /*
64 :     * VMs excel at optimizing simple array loops where indices are
65 :     * incrementing or decrementing over a valid slice, e.g.
66 :     *
67 :     * for (int i = start; i < end; i++) ... elements[i]
68 :     *
69 :     * Because in a circular array, elements are in general stored in
70 :     * two disjoint such slices, we help the VM by writing unusual
71 : jsr166 1.114 * nested loops for all traversals over the elements. Having only
72 :     * one hot inner loop body instead of two or three eases human
73 :     * maintenance and encourages VM loop inlining into the caller.
74 : jsr166 1.106 */
75 :    
76 : dl 1.1 /**
77 : dl 1.4 * The array in which the elements of the deque are stored.
78 : jsr166 1.114 * All array cells not holding deque elements are always null.
79 :     * The array always has at least one null slot (at tail).
80 : dl 1.1 */
81 : jsr166 1.75 transient Object[] elements;
82 : dl 1.1
83 :     /**
84 :     * The index of the element at the head of the deque (which is the
85 :     * element that would be removed by remove() or pop()); or an
86 : jsr166 1.106 * arbitrary number 0 <= head < elements.length equal to tail if
87 :     * the deque is empty.
88 : dl 1.1 */
89 : dl 1.41 transient int head;
90 : dl 1.1
91 : jsr166 1.106 /**
92 :     * The index at which the next element would be added to the tail
93 : jsr166 1.114 * of the deque (via addLast(E), add(E), or push(E));
94 :     * elements[tail] is always null.
95 : jsr166 1.106 */
96 :     transient int tail;
97 : jsr166 1.75
98 : dl 1.1 /**
99 : jsr166 1.75 * The maximum size of array to allocate.
100 :     * Some VMs reserve some header words in an array.
101 :     * Attempts to allocate larger arrays may result in
102 :     * OutOfMemoryError: Requested array size exceeds VM limit
103 : dl 1.1 */
104 : jsr166 1.75 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
105 : dl 1.1
106 :     /**
107 : jsr166 1.75 * Increases the capacity of this deque by at least the given amount.
108 :     *
109 :     * @param needed the required minimum extra capacity; must be positive
110 : dl 1.1 */
111 : jsr166 1.106 private void grow(int needed) {
112 : jsr166 1.75 // overflow-conscious code
113 : jsr166 1.91 final int oldCapacity = elements.length;
114 : jsr166 1.75 int newCapacity;
115 : jsr166 1.106 // Double capacity if small; else grow by 50%
116 : jsr166 1.75 int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
117 :     if (jump < needed
118 :     || (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
119 :     newCapacity = newCapacity(needed, jump);
120 : jsr166 1.125 final Object[] es = elements = Arrays.copyOf(elements, newCapacity);
121 : jsr166 1.106 // Exceptionally, here tail == head needs to be disambiguated
122 : jsr166 1.125 if (tail < head || (tail == head && es[head] != null)) {
123 : jsr166 1.75 // wrap around; slide first leg forward to end of array
124 :     int newSpace = newCapacity - oldCapacity;
125 : jsr166 1.125 System.arraycopy(es, head,
126 :     es, head + newSpace,
127 : jsr166 1.75 oldCapacity - head);
128 : jsr166 1.125 for (int i = head, to = (head += newSpace); i < to; i++)
129 :     es[i] = null;
130 : jsr166 1.75 }
131 :     // checkInvariants();
132 :     }
133 : dl 1.1
134 : jsr166 1.75 /** Capacity calculation for edge conditions, especially overflow. */
135 :     private int newCapacity(int needed, int jump) {
136 : jsr166 1.91 final int oldCapacity = elements.length, minCapacity;
137 : jsr166 1.75 if ((minCapacity = oldCapacity + needed) - MAX_ARRAY_SIZE > 0) {
138 :     if (minCapacity < 0)
139 :     throw new IllegalStateException("Sorry, deque too big");
140 :     return Integer.MAX_VALUE;
141 :     }
142 :     if (needed > jump)
143 :     return minCapacity;
144 :     return (oldCapacity + jump - MAX_ARRAY_SIZE < 0)
145 :     ? oldCapacity + jump
146 :     : MAX_ARRAY_SIZE;
147 :     }
148 : dl 1.1
149 :     /**
150 : jsr166 1.75 * Increases the internal storage of this collection, if necessary,
151 :     * to ensure that it can hold at least the given number of elements.
152 : dl 1.1 *
153 : jsr166 1.75 * @param minCapacity the desired minimum capacity
154 : jsr166 1.80 * @since TBD
155 : dl 1.1 */
156 : jsr166 1.80 /* public */ void ensureCapacity(int minCapacity) {
157 : jsr166 1.106 int needed;
158 :     if ((needed = (minCapacity + 1 - elements.length)) > 0)
159 :     grow(needed);
160 : jsr166 1.75 // checkInvariants();
161 : dl 1.1 }
162 :    
163 :     /**
164 : jsr166 1.75 * Minimizes the internal storage of this collection.
165 : jsr166 1.80 *
166 :     * @since TBD
167 : dl 1.1 */
168 : jsr166 1.80 /* public */ void trimToSize() {
169 : jsr166 1.106 int size;
170 :     if ((size = size()) + 1 < elements.length) {
171 :     elements = toArray(new Object[size + 1]);
172 : jsr166 1.75 head = 0;
173 : jsr166 1.106 tail = size;
174 : jsr166 1.75 }
175 :     // checkInvariants();
176 : dl 1.1 }
177 :    
178 :     /**
179 : dl 1.4 * Constructs an empty array deque with an initial capacity
180 : dl 1.1 * sufficient to hold 16 elements.
181 :     */
182 :     public ArrayDeque() {
183 : jsr166 1.34 elements = new Object[16];
184 : dl 1.1 }
185 :    
186 :     /**
187 :     * Constructs an empty array deque with an initial capacity
188 :     * sufficient to hold the specified number of elements.
189 :     *
190 : jsr166 1.75 * @param numElements lower bound on initial capacity of the deque
191 : dl 1.1 */
192 :     public ArrayDeque(int numElements) {
193 : jsr166 1.114 elements =
194 :     new Object[(numElements < 1) ? 1 :
195 :     (numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE :
196 :     numElements + 1];
197 : dl 1.1 }
198 :    
199 :     /**
200 :     * Constructs a deque containing the elements of the specified
201 :     * collection, in the order they are returned by the collection's
202 :     * iterator. (The first element returned by the collection's
203 :     * iterator becomes the first element, or <i>front</i> of the
204 :     * deque.)
205 :     *
206 :     * @param c the collection whose elements are to be placed into the deque
207 :     * @throws NullPointerException if the specified collection is null
208 :     */
209 :     public ArrayDeque(Collection<? extends E> c) {
210 : jsr166 1.114 this(c.size());
211 : jsr166 1.106 addAll(c);
212 : jsr166 1.75 }
213 :    
214 :     /**
215 : jsr166 1.131 * Circularly increments i, mod modulus.
216 : jsr166 1.79 * Precondition and postcondition: 0 <= i < modulus.
217 : jsr166 1.75 */
218 : jsr166 1.79 static final int inc(int i, int modulus) {
219 : jsr166 1.89 if (++i >= modulus) i = 0;
220 : jsr166 1.79 return i;
221 : jsr166 1.75 }
222 :    
223 :     /**
224 : jsr166 1.131 * Circularly decrements i, mod modulus.
225 : jsr166 1.79 * Precondition and postcondition: 0 <= i < modulus.
226 : jsr166 1.75 */
227 : jsr166 1.79 static final int dec(int i, int modulus) {
228 : jsr166 1.89 if (--i < 0) i = modulus - 1;
229 : jsr166 1.75 return i;
230 :     }
231 :    
232 :     /**
233 : jsr166 1.114 * Circularly adds the given distance to index i, mod modulus.
234 :     * Precondition: 0 <= i < modulus, 0 <= distance <= modulus.
235 :     * @return index 0 <= i < modulus
236 : jsr166 1.75 */
237 : jsr166 1.131 static final int inc(int i, int distance, int modulus) {
238 : jsr166 1.124 if ((i += distance) - modulus >= 0) i -= modulus;
239 : jsr166 1.75 return i;
240 :     }
241 :    
242 :     /**
243 : jsr166 1.106 * Subtracts j from i, mod modulus.
244 : jsr166 1.114 * Index i must be logically ahead of index j.
245 :     * Precondition: 0 <= i < modulus, 0 <= j < modulus.
246 :     * @return the "circular distance" from j to i; corner case i == j
247 : jsr166 1.130 * is disambiguated to "empty", returning 0.
248 : jsr166 1.106 */
249 :     static final int sub(int i, int j, int modulus) {
250 :     if ((i -= j) < 0) i += modulus;
251 :     return i;
252 :     }
253 :    
254 :     /**
255 : jsr166 1.75 * Returns element at array index i.
256 : jsr166 1.106 * This is a slight abuse of generics, accepted by javac.
257 : jsr166 1.75 */
258 :     @SuppressWarnings("unchecked")
259 : jsr166 1.106 static final <E> E elementAt(Object[] es, int i) {
260 :     return (E) es[i];
261 : jsr166 1.75 }
262 :    
263 :     /**
264 :     * A version of elementAt that checks for null elements.
265 :     * This check doesn't catch all possible comodifications,
266 : jsr166 1.106 * but does catch ones that corrupt traversal.
267 : jsr166 1.75 */
268 : jsr166 1.96 static final <E> E nonNullElementAt(Object[] es, int i) {
269 :     @SuppressWarnings("unchecked") E e = (E) es[i];
270 : jsr166 1.75 if (e == null)
271 :     throw new ConcurrentModificationException();
272 :     return e;
273 : dl 1.1 }
274 :    
275 :     // The main insertion and extraction methods are addFirst,
276 :     // addLast, pollFirst, pollLast. The other methods are defined in
277 :     // terms of these.
278 :    
279 :     /**
280 : dl 1.5 * Inserts the specified element at the front of this deque.
281 : dl 1.1 *
282 : jsr166 1.9 * @param e the element to add
283 :     * @throws NullPointerException if the specified element is null
284 : dl 1.1 */
285 :     public void addFirst(E e) {
286 : jsr166 1.106 if (e == null)
287 :     throw new NullPointerException();
288 :     final Object[] es = elements;
289 :     es[head = dec(head, es.length)] = e;
290 :     if (head == tail)
291 :     grow(1);
292 : jsr166 1.83 // checkInvariants();
293 : dl 1.1 }
294 :    
295 :     /**
296 : dl 1.6 * Inserts the specified element at the end of this deque.
297 : jsr166 1.14 *
298 :     * <p>This method is equivalent to {@link #add}.
299 : dl 1.1 *
300 : jsr166 1.9 * @param e the element to add
301 :     * @throws NullPointerException if the specified element is null
302 : dl 1.1 */
303 :     public void addLast(E e) {
304 : jsr166 1.106 if (e == null)
305 :     throw new NullPointerException();
306 :     final Object[] es = elements;
307 :     es[tail] = e;
308 :     if (head == (tail = inc(tail, es.length)))
309 :     grow(1);
310 : jsr166 1.83 // checkInvariants();
311 : jsr166 1.75 }
312 :    
313 :     /**
314 :     * Adds all of the elements in the specified collection at the end
315 :     * of this deque, as if by calling {@link #addLast} on each one,
316 : jsr166 1.129 * in the order that they are returned by the collection's iterator.
317 : jsr166 1.75 *
318 :     * @param c the elements to be inserted into this deque
319 :     * @return {@code true} if this deque changed as a result of the call
320 :     * @throws NullPointerException if the specified collection or any
321 :     * of its elements are null
322 :     */
323 :     public boolean addAll(Collection<? extends E> c) {
324 : jsr166 1.117 final int s, needed;
325 :     if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0)
326 : jsr166 1.87 grow(needed);
327 : jsr166 1.116 c.forEach(this::addLast);
328 : jsr166 1.75 // checkInvariants();
329 : jsr166 1.106 return size() > s;
330 : dl 1.1 }
331 :    
332 :     /**
333 : dl 1.5 * Inserts the specified element at the front of this deque.
334 : dl 1.1 *
335 : jsr166 1.9 * @param e the element to add
336 : jsr166 1.40 * @return {@code true} (as specified by {@link Deque#offerFirst})
337 : jsr166 1.9 * @throws NullPointerException if the specified element is null
338 : dl 1.1 */
339 :     public boolean offerFirst(E e) {
340 :     addFirst(e);
341 :     return true;
342 :     }
343 :    
344 :     /**
345 : dl 1.6 * Inserts the specified element at the end of this deque.
346 : dl 1.1 *
347 : jsr166 1.9 * @param e the element to add
348 : jsr166 1.40 * @return {@code true} (as specified by {@link Deque#offerLast})
349 : jsr166 1.9 * @throws NullPointerException if the specified element is null
350 : dl 1.1 */
351 :     public boolean offerLast(E e) {
352 :     addLast(e);
353 :     return true;
354 :     }
355 :    
356 :     /**
357 : jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
358 : dl 1.1 */
359 :     public E removeFirst() {
360 : jsr166 1.84 E e = pollFirst();
361 :     if (e == null)
362 : dl 1.1 throw new NoSuchElementException();
363 : jsr166 1.106 // checkInvariants();
364 : jsr166 1.84 return e;
365 : dl 1.1 }
366 :    
367 :     /**
368 : jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
369 : dl 1.1 */
370 :     public E removeLast() {
371 : jsr166 1.84 E e = pollLast();
372 :     if (e == null)
373 : dl 1.1 throw new NoSuchElementException();
374 : jsr166 1.106 // checkInvariants();
375 : jsr166 1.84 return e;
376 : dl 1.1 }
377 :    
378 : jsr166 1.9 public E pollFirst() {
379 : jsr166 1.106 final Object[] es;
380 :     final int h;
381 :     E e = elementAt(es = elements, h = head);
382 :     if (e != null) {
383 :     es[h] = null;
384 :     head = inc(h, es.length);
385 :     }
386 : jsr166 1.75 // checkInvariants();
387 :     return e;
388 : dl 1.1 }
389 :    
390 : jsr166 1.9 public E pollLast() {
391 : jsr166 1.106 final Object[] es;
392 :     final int t;
393 :     E e = elementAt(es = elements, t = dec(tail, es.length));
394 :     if (e != null)
395 :     es[tail = t] = null;
396 : jsr166 1.75 // checkInvariants();
397 :     return e;
398 : dl 1.1 }
399 :    
400 :     /**
401 : jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
402 : dl 1.1 */
403 :     public E getFirst() {
404 : jsr166 1.106 E e = elementAt(elements, head);
405 :     if (e == null)
406 :     throw new NoSuchElementException();
407 : jsr166 1.75 // checkInvariants();
408 : jsr166 1.106 return e;
409 : dl 1.1 }
410 :    
411 :     /**
412 : jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
413 : dl 1.1 */
414 :     public E getLast() {
415 : jsr166 1.106 final Object[] es = elements;
416 :     E e = elementAt(es, dec(tail, es.length));
417 :     if (e == null)
418 :     throw new NoSuchElementException();
419 : jsr166 1.75 // checkInvariants();
420 : jsr166 1.106 return e;
421 : dl 1.1 }
422 :    
423 : jsr166 1.9 public E peekFirst() {
424 : jsr166 1.75 // checkInvariants();
425 : jsr166 1.106 return elementAt(elements, head);
426 : jsr166 1.9 }
427 :    
428 :     public E peekLast() {
429 : jsr166 1.75 // checkInvariants();
430 : jsr166 1.106 final Object[] es;
431 :     return elementAt(es = elements, dec(tail, es.length));
432 : jsr166 1.9 }
433 :    
434 : dl 1.1 /**
435 :     * Removes the first occurrence of the specified element in this
436 : jsr166 1.9 * deque (when traversing the deque from head to tail).
437 :     * If the deque does not contain the element, it is unchanged.
438 : jsr166 1.40 * More formally, removes the first element {@code e} such that
439 :     * {@code o.equals(e)} (if such an element exists).
440 :     * Returns {@code true} if this deque contained the specified element
441 : jsr166 1.12 * (or equivalently, if this deque changed as a result of the call).
442 : dl 1.1 *
443 : dl 1.5 * @param o element to be removed from this deque, if present
444 : jsr166 1.40 * @return {@code true} if the deque contained the specified element
445 : dl 1.1 */
446 : dl 1.5 public boolean removeFirstOccurrence(Object o) {
447 : jsr166 1.58 if (o != null) {
448 : jsr166 1.99 final Object[] es = elements;
449 : jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
450 :     ; i = 0, to = end) {
451 : jsr166 1.92 for (; i < to; i++)
452 : jsr166 1.99 if (o.equals(es[i])) {
453 : jsr166 1.89 delete(i);
454 :     return true;
455 :     }
456 : jsr166 1.106 if (to == end) break;
457 : dl 1.1 }
458 :     }
459 :     return false;
460 :     }
461 :    
462 :     /**
463 :     * Removes the last occurrence of the specified element in this
464 : jsr166 1.9 * deque (when traversing the deque from head to tail).
465 :     * If the deque does not contain the element, it is unchanged.
466 : jsr166 1.40 * More formally, removes the last element {@code e} such that
467 :     * {@code o.equals(e)} (if such an element exists).
468 :     * Returns {@code true} if this deque contained the specified element
469 : jsr166 1.12 * (or equivalently, if this deque changed as a result of the call).
470 : dl 1.1 *
471 : dl 1.5 * @param o element to be removed from this deque, if present
472 : jsr166 1.40 * @return {@code true} if the deque contained the specified element
473 : dl 1.1 */
474 : dl 1.5 public boolean removeLastOccurrence(Object o) {
475 : jsr166 1.59 if (o != null) {
476 : jsr166 1.99 final Object[] es = elements;
477 : jsr166 1.107 for (int i = tail, end = head, to = (i >= end) ? end : 0;
478 :     ; i = es.length, to = end) {
479 : jsr166 1.110 for (i--; i > to - 1; i--)
480 : jsr166 1.99 if (o.equals(es[i])) {
481 : jsr166 1.89 delete(i);
482 :     return true;
483 :     }
484 : jsr166 1.106 if (to == end) break;
485 : dl 1.1 }
486 :     }
487 :     return false;
488 :     }
489 :    
490 :     // *** Queue methods ***
491 :    
492 :     /**
493 : dl 1.6 * Inserts the specified element at the end of this deque.
494 : dl 1.1 *
495 :     * <p>This method is equivalent to {@link #addLast}.
496 :     *
497 : jsr166 1.9 * @param e the element to add
498 : jsr166 1.40 * @return {@code true} (as specified by {@link Collection#add})
499 : jsr166 1.9 * @throws NullPointerException if the specified element is null
500 : dl 1.1 */
501 :     public boolean add(E e) {
502 :     addLast(e);
503 :     return true;
504 :     }
505 :    
506 :     /**
507 : jsr166 1.9 * Inserts the specified element at the end of this deque.
508 : dl 1.1 *
509 : jsr166 1.9 * <p>This method is equivalent to {@link #offerLast}.
510 : dl 1.1 *
511 : jsr166 1.9 * @param e the element to add
512 : jsr166 1.40 * @return {@code true} (as specified by {@link Queue#offer})
513 : jsr166 1.9 * @throws NullPointerException if the specified element is null
514 : dl 1.1 */
515 : jsr166 1.9 public boolean offer(E e) {
516 :     return offerLast(e);
517 : dl 1.1 }
518 :    
519 :     /**
520 :     * Retrieves and removes the head of the queue represented by this deque.
521 : jsr166 1.15 *
522 : jsr166 1.127 * This method differs from {@link #poll() poll()} only in that it
523 :     * throws an exception if this deque is empty.
524 : dl 1.1 *
525 :     * <p>This method is equivalent to {@link #removeFirst}.
526 :     *
527 :     * @return the head of the queue represented by this deque
528 : jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
529 : dl 1.1 */
530 :     public E remove() {
531 :     return removeFirst();
532 :     }
533 :    
534 :     /**
535 : jsr166 1.9 * Retrieves and removes the head of the queue represented by this deque
536 :     * (in other words, the first element of this deque), or returns
537 : jsr166 1.40 * {@code null} if this deque is empty.
538 : dl 1.1 *
539 : jsr166 1.9 * <p>This method is equivalent to {@link #pollFirst}.
540 : dl 1.1 *
541 :     * @return the head of the queue represented by this deque, or
542 : jsr166 1.40 * {@code null} if this deque is empty
543 : dl 1.1 */
544 : jsr166 1.9 public E poll() {
545 :     return pollFirst();
546 : dl 1.1 }
547 :    
548 :     /**
549 :     * Retrieves, but does not remove, the head of the queue represented by
550 : jsr166 1.15 * this deque. This method differs from {@link #peek peek} only in
551 :     * that it throws an exception if this deque is empty.
552 : dl 1.1 *
553 : jsr166 1.8 * <p>This method is equivalent to {@link #getFirst}.
554 : dl 1.1 *
555 :     * @return the head of the queue represented by this deque
556 : jsr166 1.9 * @throws NoSuchElementException {@inheritDoc}
557 : dl 1.1 */
558 :     public E element() {
559 :     return getFirst();
560 :     }
561 :    
562 : jsr166 1.9 /**
563 :     * Retrieves, but does not remove, the head of the queue represented by
564 : jsr166 1.40 * this deque, or returns {@code null} if this deque is empty.
565 : jsr166 1.9 *
566 :     * <p>This method is equivalent to {@link #peekFirst}.
567 :     *
568 :     * @return the head of the queue represented by this deque, or
569 : jsr166 1.40 * {@code null} if this deque is empty
570 : jsr166 1.9 */
571 :     public E peek() {
572 :     return peekFirst();
573 :     }
574 :    
575 : dl 1.1 // *** Stack methods ***
576 :    
577 :     /**
578 :     * Pushes an element onto the stack represented by this deque. In other
579 : dl 1.5 * words, inserts the element at the front of this deque.
580 : dl 1.1 *
581 :     * <p>This method is equivalent to {@link #addFirst}.
582 :     *
583 :     * @param e the element to push
584 : jsr166 1.9 * @throws NullPointerException if the specified element is null
585 : dl 1.1 */
586 :     public void push(E e) {
587 :     addFirst(e);
588 :     }
589 :    
590 :     /**
591 :     * Pops an element from the stack represented by this deque. In other
592 : dl 1.2 * words, removes and returns the first element of this deque.
593 : dl 1.1 *
594 :     * <p>This method is equivalent to {@link #removeFirst()}.
595 :     *
596 :     * @return the element at the front of this deque (which is the top
597 : jsr166 1.9 * of the stack represented by this deque)
598 :     * @throws NoSuchElementException {@inheritDoc}
599 : dl 1.1 */
600 :     public E pop() {
601 :     return removeFirst();
602 :     }
603 :    
604 :     /**
605 : jsr166 1.75 * Removes the element at the specified position in the elements array.
606 :     * This can result in forward or backwards motion of array elements.
607 :     * We optimize for least element motion.
608 : dl 1.1 *
609 : dl 1.5 * <p>This method is called delete rather than remove to emphasize
610 : jsr166 1.9 * that its semantics differ from those of {@link List#remove(int)}.
611 : dl 1.5 *
612 : jsr166 1.106 * @return true if elements near tail moved backwards
613 : dl 1.1 */
614 : jsr166 1.71 boolean delete(int i) {
615 : jsr166 1.75 // checkInvariants();
616 : jsr166 1.99 final Object[] es = elements;
617 :     final int capacity = es.length;
618 : jsr166 1.118 final int h, t;
619 : jsr166 1.106 // number of elements before to-be-deleted elt
620 : jsr166 1.118 final int front = sub(i, h = head, capacity);
621 :     // number of elements after to-be-deleted elt
622 :     final int back = sub(t = tail, i, capacity) - 1;
623 : jsr166 1.30 if (front < back) {
624 : jsr166 1.75 // move front elements forwards
625 : jsr166 1.30 if (h <= i) {
626 : jsr166 1.99 System.arraycopy(es, h, es, h + 1, front);
627 : jsr166 1.30 } else { // Wrap around
628 : jsr166 1.99 System.arraycopy(es, 0, es, 1, i);
629 :     es[0] = es[capacity - 1];
630 :     System.arraycopy(es, h, es, h + 1, front - (i + 1));
631 : jsr166 1.30 }
632 : jsr166 1.99 es[h] = null;
633 : jsr166 1.106 head = inc(h, capacity);
634 : jsr166 1.75 // checkInvariants();
635 : jsr166 1.30 return false;
636 :     } else {
637 : jsr166 1.75 // move back elements backwards
638 : jsr166 1.118 tail = dec(t, capacity);
639 : jsr166 1.75 if (i <= tail) {
640 : jsr166 1.99 System.arraycopy(es, i + 1, es, i, back);
641 : jsr166 1.30 } else { // Wrap around
642 : jsr166 1.118 System.arraycopy(es, i + 1, es, i, capacity - (i + 1));
643 : jsr166 1.99 es[capacity - 1] = es[0];
644 : jsr166 1.118 System.arraycopy(es, 1, es, 0, t - 1);
645 : jsr166 1.30 }
646 : jsr166 1.99 es[tail] = null;
647 : jsr166 1.75 // checkInvariants();
648 : jsr166 1.30 return true;
649 :     }
650 : dl 1.23 }
651 :    
652 : dl 1.1 // *** Collection Methods ***
653 :    
654 :     /**
655 :     * Returns the number of elements in this deque.
656 :     *
657 :     * @return the number of elements in this deque
658 :     */
659 :     public int size() {
660 : jsr166 1.106 return sub(tail, head, elements.length);
661 : dl 1.1 }
662 :    
663 :     /**
664 : jsr166 1.40 * Returns {@code true} if this deque contains no elements.
665 : dl 1.1 *
666 : jsr166 1.40 * @return {@code true} if this deque contains no elements
667 : dl 1.1 */
668 :     public boolean isEmpty() {
669 : jsr166 1.106 return head == tail;
670 : dl 1.1 }
671 :    
672 :     /**
673 :     * Returns an iterator over the elements in this deque. The elements
674 :     * will be ordered from first (head) to last (tail). This is the same
675 :     * order that elements would be dequeued (via successive calls to
676 :     * {@link #remove} or popped (via successive calls to {@link #pop}).
677 : dl 1.5 *
678 : jsr166 1.18 * @return an iterator over the elements in this deque
679 : dl 1.1 */
680 :     public Iterator<E> iterator() {
681 :     return new DeqIterator();
682 :     }
683 :    
684 : dl 1.16 public Iterator<E> descendingIterator() {
685 :     return new DescendingIterator();
686 :     }
687 :    
688 : dl 1.1 private class DeqIterator implements Iterator<E> {
689 : jsr166 1.75 /** Index of element to be returned by subsequent call to next. */
690 :     int cursor;
691 : dl 1.1
692 : jsr166 1.75 /** Number of elements yet to be returned. */
693 : jsr166 1.106 int remaining = size();
694 : dl 1.1
695 :     /**
696 :     * Index of element returned by most recent call to next.
697 :     * Reset to -1 if element is deleted by a call to remove.
698 :     */
699 : jsr166 1.75 int lastRet = -1;
700 : dl 1.1
701 : jsr166 1.75 DeqIterator() { cursor = head; }
702 :    
703 :     public final boolean hasNext() {
704 :     return remaining > 0;
705 :     }
706 :    
707 : jsr166 1.81 public E next() {
708 : jsr166 1.91 if (remaining <= 0)
709 : dl 1.1 throw new NoSuchElementException();
710 : jsr166 1.99 final Object[] es = elements;
711 :     E e = nonNullElementAt(es, cursor);
712 : jsr166 1.122 cursor = inc(lastRet = cursor, es.length);
713 : jsr166 1.75 remaining--;
714 :     return e;
715 : dl 1.1 }
716 :    
717 : jsr166 1.81 void postDelete(boolean leftShifted) {
718 :     if (leftShifted)
719 : jsr166 1.106 cursor = dec(cursor, elements.length);
720 : jsr166 1.81 }
721 :    
722 : jsr166 1.75 public final void remove() {
723 : dl 1.1 if (lastRet < 0)
724 :     throw new IllegalStateException();
725 : jsr166 1.81 postDelete(delete(lastRet));
726 : dl 1.1 lastRet = -1;
727 :     }
728 : jsr166 1.68
729 : jsr166 1.81 public void forEachRemaining(Consumer<? super E> action) {
730 : jsr166 1.98 Objects.requireNonNull(action);
731 : jsr166 1.106 int r;
732 :     if ((r = remaining) <= 0)
733 :     return;
734 :     remaining = 0;
735 :     final Object[] es = elements;
736 :     if (es[cursor] == null || sub(tail, cursor, es.length) != r)
737 :     throw new ConcurrentModificationException();
738 :     for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
739 :     ; i = 0, to = end) {
740 :     for (; i < to; i++)
741 :     action.accept(elementAt(es, i));
742 :     if (to == end) {
743 :     if (end != tail)
744 :     throw new ConcurrentModificationException();
745 :     lastRet = dec(end, es.length);
746 :     break;
747 :     }
748 : jsr166 1.89 }
749 : jsr166 1.68 }
750 : dl 1.1 }
751 :    
752 : jsr166 1.75 private class DescendingIterator extends DeqIterator {
753 : jsr166 1.109 DescendingIterator() { cursor = dec(tail, elements.length); }
754 : jsr166 1.75
755 : jsr166 1.81 public final E next() {
756 : jsr166 1.91 if (remaining <= 0)
757 : jsr166 1.81 throw new NoSuchElementException();
758 : jsr166 1.99 final Object[] es = elements;
759 :     E e = nonNullElementAt(es, cursor);
760 : jsr166 1.123 cursor = dec(lastRet = cursor, es.length);
761 : jsr166 1.81 remaining--;
762 :     return e;
763 : jsr166 1.75 }
764 :    
765 : jsr166 1.81 void postDelete(boolean leftShifted) {
766 :     if (!leftShifted)
767 : jsr166 1.106 cursor = inc(cursor, elements.length);
768 : jsr166 1.81 }
769 :    
770 :     public final void forEachRemaining(Consumer<? super E> action) {
771 : jsr166 1.98 Objects.requireNonNull(action);
772 : jsr166 1.106 int r;
773 :     if ((r = remaining) <= 0)
774 :     return;
775 :     remaining = 0;
776 :     final Object[] es = elements;
777 :     if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
778 :     throw new ConcurrentModificationException();
779 : jsr166 1.108 for (int i = cursor, end = head, to = (i >= end) ? end : 0;
780 : jsr166 1.106 ; i = es.length - 1, to = end) {
781 : jsr166 1.110 // hotspot generates faster code than for: i >= to !
782 :     for (; i > to - 1; i--)
783 : jsr166 1.106 action.accept(elementAt(es, i));
784 :     if (to == end) {
785 : jsr166 1.108 if (end != head)
786 : jsr166 1.106 throw new ConcurrentModificationException();
787 : jsr166 1.112 lastRet = end;
788 : jsr166 1.106 break;
789 : jsr166 1.98 }
790 : jsr166 1.89 }
791 : jsr166 1.75 }
792 :     }
793 :    
794 : jsr166 1.52 /**
795 : jsr166 1.75 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
796 :     * and <em>fail-fast</em> {@link Spliterator} over the elements in this
797 :     * deque.
798 :     *
799 :     * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
800 :     * {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and
801 :     * {@link Spliterator#NONNULL}. Overriding implementations should document
802 :     * the reporting of additional characteristic values.
803 :     *
804 :     * @return a {@code Spliterator} over the elements in this deque
805 :     * @since 1.8
806 : jsr166 1.52 */
807 : jsr166 1.75 public Spliterator<E> spliterator() {
808 : jsr166 1.106 return new DeqSpliterator();
809 : jsr166 1.75 }
810 :    
811 : jsr166 1.106 final class DeqSpliterator implements Spliterator<E> {
812 :     private int fence; // -1 until first use
813 :     private int cursor; // current index, modified on traverse/split
814 : jsr166 1.75
815 : jsr166 1.76 /** Constructs late-binding spliterator over all elements. */
816 : jsr166 1.106 DeqSpliterator() {
817 :     this.fence = -1;
818 : jsr166 1.76 }
819 :    
820 : jsr166 1.106 /** Constructs spliterator over the given range. */
821 :     DeqSpliterator(int origin, int fence) {
822 : jsr166 1.124 // assert 0 <= origin && origin < elements.length;
823 :     // assert 0 <= fence && fence < elements.length;
824 : jsr166 1.106 this.cursor = origin;
825 :     this.fence = fence;
826 : jsr166 1.75 }
827 :    
828 : jsr166 1.106 /** Ensures late-binding initialization; then returns fence. */
829 :     private int getFence() { // force initialization
830 :     int t;
831 :     if ((t = fence) < 0) {
832 :     t = fence = tail;
833 : jsr166 1.76 cursor = head;
834 :     }
835 : jsr166 1.106 return t;
836 : jsr166 1.76 }
837 :    
838 : jsr166 1.106 public DeqSpliterator trySplit() {
839 :     final Object[] es = elements;
840 :     final int i, n;
841 :     return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
842 :     ? null
843 : jsr166 1.131 : new DeqSpliterator(i, cursor = inc(i, n, es.length));
844 : jsr166 1.75 }
845 : dl 1.16
846 : jsr166 1.75 public void forEachRemaining(Consumer<? super E> action) {
847 : jsr166 1.106 if (action == null)
848 :     throw new NullPointerException();
849 :     final int end = getFence(), cursor = this.cursor;
850 :     final Object[] es = elements;
851 :     if (cursor != end) {
852 :     this.cursor = end;
853 :     // null check at both ends of range is sufficient
854 :     if (es[cursor] == null || es[dec(end, es.length)] == null)
855 :     throw new ConcurrentModificationException();
856 :     for (int i = cursor, to = (i <= end) ? end : es.length;
857 :     ; i = 0, to = end) {
858 :     for (; i < to; i++)
859 :     action.accept(elementAt(es, i));
860 :     if (to == end) break;
861 :     }
862 :     }
863 : dl 1.16 }
864 :    
865 : jsr166 1.75 public boolean tryAdvance(Consumer<? super E> action) {
866 : jsr166 1.121 Objects.requireNonNull(action);
867 :     final Object[] es = elements;
868 :     if (fence < 0) { fence = tail; cursor = head; } // late-binding
869 :     final int i;
870 :     if ((i = cursor) == fence)
871 : jsr166 1.75 return false;
872 : jsr166 1.121 E e = nonNullElementAt(es, i);
873 : jsr166 1.106 cursor = inc(i, es.length);
874 : jsr166 1.121 action.accept(e);
875 : jsr166 1.75 return true;
876 :     }
877 :    
878 :     public long estimateSize() {
879 : jsr166 1.106 return sub(getFence(), cursor, elements.length);
880 : jsr166 1.75 }
881 :    
882 :     public int characteristics() {
883 :     return Spliterator.NONNULL
884 :     | Spliterator.ORDERED
885 :     | Spliterator.SIZED
886 :     | Spliterator.SUBSIZED;
887 : dl 1.16 }
888 : jsr166 1.75 }
889 : dl 1.16
890 : jsr166 1.126 /**
891 :     * @throws NullPointerException {@inheritDoc}
892 :     */
893 : jsr166 1.75 public void forEach(Consumer<? super E> action) {
894 :     Objects.requireNonNull(action);
895 : jsr166 1.99 final Object[] es = elements;
896 : jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
897 :     ; i = 0, to = end) {
898 : jsr166 1.92 for (; i < to; i++)
899 : jsr166 1.106 action.accept(elementAt(es, i));
900 :     if (to == end) {
901 :     if (end != tail) throw new ConcurrentModificationException();
902 :     break;
903 :     }
904 : jsr166 1.89 }
905 : jsr166 1.75 // checkInvariants();
906 :     }
907 :    
908 :     /**
909 :     * Replaces each element of this deque with the result of applying the
910 :     * operator to that element, as specified by {@link List#replaceAll}.
911 :     *
912 :     * @param operator the operator to apply to each element
913 : jsr166 1.80 * @since TBD
914 : jsr166 1.75 */
915 : jsr166 1.80 /* public */ void replaceAll(UnaryOperator<E> operator) {
916 : jsr166 1.75 Objects.requireNonNull(operator);
917 : jsr166 1.99 final Object[] es = elements;
918 : jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
919 :     ; i = 0, to = end) {
920 : jsr166 1.92 for (; i < to; i++)
921 : jsr166 1.106 es[i] = operator.apply(elementAt(es, i));
922 :     if (to == end) {
923 :     if (end != tail) throw new ConcurrentModificationException();
924 :     break;
925 :     }
926 : jsr166 1.89 }
927 : jsr166 1.75 // checkInvariants();
928 :     }
929 :    
930 :     /**
931 :     * @throws NullPointerException {@inheritDoc}
932 :     */
933 :     public boolean removeIf(Predicate<? super E> filter) {
934 :     Objects.requireNonNull(filter);
935 :     return bulkRemove(filter);
936 :     }
937 :    
938 :     /**
939 :     * @throws NullPointerException {@inheritDoc}
940 :     */
941 :     public boolean removeAll(Collection<?> c) {
942 :     Objects.requireNonNull(c);
943 :     return bulkRemove(e -> c.contains(e));
944 :     }
945 :    
946 :     /**
947 :     * @throws NullPointerException {@inheritDoc}
948 :     */
949 :     public boolean retainAll(Collection<?> c) {
950 :     Objects.requireNonNull(c);
951 :     return bulkRemove(e -> !c.contains(e));
952 :     }
953 :    
954 :     /** Implementation of bulk remove methods. */
955 :     private boolean bulkRemove(Predicate<? super E> filter) {
956 :     // checkInvariants();
957 : jsr166 1.99 final Object[] es = elements;
958 : jsr166 1.106 // Optimize for initial run of survivors
959 :     for (int i = head, end = tail, to = (i <= end) ? end : es.length;
960 :     ; i = 0, to = end) {
961 : jsr166 1.104 for (; i < to; i++)
962 : jsr166 1.106 if (filter.test(elementAt(es, i)))
963 : jsr166 1.113 return bulkRemoveModified(filter, i);
964 : jsr166 1.106 if (to == end) {
965 :     if (end != tail) throw new ConcurrentModificationException();
966 :     break;
967 :     }
968 : jsr166 1.104 }
969 : jsr166 1.106 return false;
970 : jsr166 1.104 }
971 :    
972 : jsr166 1.113 // A tiny bit set implementation
973 :    
974 :     private static long[] nBits(int n) {
975 :     return new long[((n - 1) >> 6) + 1];
976 :     }
977 :     private static void setBit(long[] bits, int i) {
978 :     bits[i >> 6] |= 1L << i;
979 :     }
980 :     private static boolean isClear(long[] bits, int i) {
981 :     return (bits[i >> 6] & (1L << i)) == 0;
982 :     }
983 :    
984 : jsr166 1.104 /**
985 :     * Helper for bulkRemove, in case of at least one deletion.
986 : jsr166 1.113 * Tolerate predicates that reentrantly access the collection for
987 :     * read (but writers still get CME), so traverse once to find
988 :     * elements to delete, a second pass to physically expunge.
989 :     *
990 :     * @param beg valid index of first element to be deleted
991 : jsr166 1.104 */
992 : jsr166 1.106 private boolean bulkRemoveModified(
993 : jsr166 1.113 Predicate<? super E> filter, final int beg) {
994 : jsr166 1.104 final Object[] es = elements;
995 : jsr166 1.99 final int capacity = es.length;
996 : jsr166 1.106 final int end = tail;
997 : jsr166 1.113 final long[] deathRow = nBits(sub(end, beg, capacity));
998 :     deathRow[0] = 1L; // set bit 0
999 :     for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1000 :     ; i = 0, to = end, k -= capacity) {
1001 :     for (; i < to; i++)
1002 :     if (filter.test(elementAt(es, i)))
1003 :     setBit(deathRow, i - k);
1004 :     if (to == end) break;
1005 :     }
1006 :     // a two-finger traversal, with hare i reading, tortoise w writing
1007 :     int w = beg;
1008 :     for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1009 :     ; w = 0) { // w rejoins i on second leg
1010 :     // In this loop, i and w are on the same leg, with i > w
1011 :     for (; i < to; i++)
1012 :     if (isClear(deathRow, i - k))
1013 :     es[w++] = es[i];
1014 :     if (to == end) break;
1015 :     // In this loop, w is on the first leg, i on the second
1016 :     for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1017 :     if (isClear(deathRow, i - k))
1018 :     es[w++] = es[i];
1019 :     if (i >= to) {
1020 :     if (w == capacity) w = 0; // "corner" case
1021 :     break;
1022 : jsr166 1.104 }
1023 : dl 1.16 }
1024 : jsr166 1.113 if (end != tail) throw new ConcurrentModificationException();
1025 :     circularClear(es, tail = w, end);
1026 :     // checkInvariants();
1027 :     return true;
1028 : dl 1.16 }
1029 :    
1030 : dl 1.1 /**
1031 : jsr166 1.40 * Returns {@code true} if this deque contains the specified element.
1032 :     * More formally, returns {@code true} if and only if this deque contains
1033 :     * at least one element {@code e} such that {@code o.equals(e)}.
1034 : dl 1.1 *
1035 :     * @param o object to be checked for containment in this deque
1036 : jsr166 1.40 * @return {@code true} if this deque contains the specified element
1037 : dl 1.1 */
1038 :     public boolean contains(Object o) {
1039 : jsr166 1.58 if (o != null) {
1040 : jsr166 1.99 final Object[] es = elements;
1041 : jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1042 :     ; i = 0, to = end) {
1043 : jsr166 1.92 for (; i < to; i++)
1044 : jsr166 1.99 if (o.equals(es[i]))
1045 : jsr166 1.89 return true;
1046 : jsr166 1.106 if (to == end) break;
1047 : jsr166 1.89 }
1048 : dl 1.1 }
1049 :     return false;
1050 :     }
1051 :    
1052 :     /**
1053 :     * Removes a single instance of the specified element from this deque.
1054 : jsr166 1.9 * If the deque does not contain the element, it is unchanged.
1055 : jsr166 1.40 * More formally, removes the first element {@code e} such that
1056 :     * {@code o.equals(e)} (if such an element exists).
1057 :     * Returns {@code true} if this deque contained the specified element
1058 : jsr166 1.12 * (or equivalently, if this deque changed as a result of the call).
1059 : jsr166 1.9 *
1060 : jsr166 1.46 * <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
1061 : dl 1.1 *
1062 : jsr166 1.9 * @param o element to be removed from this deque, if present
1063 : jsr166 1.40 * @return {@code true} if this deque contained the specified element
1064 : dl 1.1 */
1065 : jsr166 1.9 public boolean remove(Object o) {
1066 :     return removeFirstOccurrence(o);
1067 : dl 1.1 }
1068 :    
1069 :     /**
1070 :     * Removes all of the elements from this deque.
1071 : jsr166 1.7 * The deque will be empty after this call returns.
1072 : dl 1.1 */
1073 :     public void clear() {
1074 : jsr166 1.106 circularClear(elements, head, tail);
1075 :     head = tail = 0;
1076 : jsr166 1.75 // checkInvariants();
1077 : dl 1.1 }
1078 :    
1079 :     /**
1080 : jsr166 1.106 * Nulls out slots starting at array index i, upto index end.
1081 : jsr166 1.125 * Condition i == end means "empty" - nothing to do.
1082 : jsr166 1.89 */
1083 : jsr166 1.106 private static void circularClear(Object[] es, int i, int end) {
1084 : jsr166 1.125 // assert 0 <= i && i < es.length;
1085 :     // assert 0 <= end && end < es.length;
1086 : jsr166 1.106 for (int to = (i <= end) ? end : es.length;
1087 :     ; i = 0, to = end) {
1088 : jsr166 1.125 for (; i < to; i++) es[i] = null;
1089 : jsr166 1.106 if (to == end) break;
1090 : jsr166 1.99 }
1091 : jsr166 1.89 }
1092 :    
1093 :     /**
1094 : dl 1.5 * Returns an array containing all of the elements in this deque
1095 : jsr166 1.10 * in proper sequence (from first to last element).
1096 : dl 1.1 *
1097 : jsr166 1.10 * <p>The returned array will be "safe" in that no references to it are
1098 :     * maintained by this deque. (In other words, this method must allocate
1099 :     * a new array). The caller is thus free to modify the returned array.
1100 : jsr166 1.13 *
1101 : jsr166 1.11 * <p>This method acts as bridge between array-based and collection-based
1102 :     * APIs.
1103 :     *
1104 : dl 1.5 * @return an array containing all of the elements in this deque
1105 : dl 1.1 */
1106 :     public Object[] toArray() {
1107 : jsr166 1.86 return toArray(Object[].class);
1108 :     }
1109 :    
1110 :     private <T> T[] toArray(Class<T[]> klazz) {
1111 : jsr166 1.99 final Object[] es = elements;
1112 : jsr166 1.86 final T[] a;
1113 : jsr166 1.119 final int head = this.head, tail = this.tail, end;
1114 :     if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) {
1115 : jsr166 1.120 // Uses null extension feature of copyOfRange
1116 : jsr166 1.99 a = Arrays.copyOfRange(es, head, end, klazz);
1117 : jsr166 1.86 } else {
1118 :     // integer overflow!
1119 : jsr166 1.119 a = Arrays.copyOfRange(es, 0, end - head, klazz);
1120 :     System.arraycopy(es, head, a, 0, es.length - head);
1121 : jsr166 1.86 }
1122 : jsr166 1.119 if (end != tail)
1123 :     System.arraycopy(es, 0, a, es.length - head, tail);
1124 : jsr166 1.50 return a;
1125 : dl 1.1 }
1126 :    
1127 :     /**
1128 : jsr166 1.10 * Returns an array containing all of the elements in this deque in
1129 :     * proper sequence (from first to last element); the runtime type of the
1130 :     * returned array is that of the specified array. If the deque fits in
1131 :     * the specified array, it is returned therein. Otherwise, a new array
1132 :     * is allocated with the runtime type of the specified array and the
1133 :     * size of this deque.
1134 :     *
1135 :     * <p>If this deque fits in the specified array with room to spare
1136 :     * (i.e., the array has more elements than this deque), the element in
1137 :     * the array immediately following the end of the deque is set to
1138 : jsr166 1.40 * {@code null}.
1139 : jsr166 1.10 *
1140 :     * <p>Like the {@link #toArray()} method, this method acts as bridge between
1141 :     * array-based and collection-based APIs. Further, this method allows
1142 :     * precise control over the runtime type of the output array, and may,
1143 :     * under certain circumstances, be used to save allocation costs.
1144 :     *
1145 : jsr166 1.40 * <p>Suppose {@code x} is a deque known to contain only strings.
1146 : jsr166 1.10 * The following code can be used to dump the deque into a newly
1147 : jsr166 1.40 * allocated array of {@code String}:
1148 : jsr166 1.10 *
1149 : jsr166 1.63 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
1150 : jsr166 1.10 *
1151 : jsr166 1.40 * Note that {@code toArray(new Object[0])} is identical in function to
1152 :     * {@code toArray()}.
1153 : dl 1.1 *
1154 :     * @param a the array into which the elements of the deque are to
1155 : jsr166 1.9 * be stored, if it is big enough; otherwise, a new array of the
1156 :     * same runtime type is allocated for this purpose
1157 : jsr166 1.10 * @return an array containing all of the elements in this deque
1158 :     * @throws ArrayStoreException if the runtime type of the specified array
1159 :     * is not a supertype of the runtime type of every element in
1160 :     * this deque
1161 :     * @throws NullPointerException if the specified array is null
1162 : dl 1.1 */
1163 : jsr166 1.34 @SuppressWarnings("unchecked")
1164 : dl 1.1 public <T> T[] toArray(T[] a) {
1165 : jsr166 1.99 final int size;
1166 : jsr166 1.106 if ((size = size()) > a.length)
1167 : jsr166 1.86 return toArray((Class<T[]>) a.getClass());
1168 : jsr166 1.99 final Object[] es = elements;
1169 : jsr166 1.106 for (int i = head, j = 0, len = Math.min(size, es.length - i);
1170 :     ; i = 0, len = tail) {
1171 : jsr166 1.101 System.arraycopy(es, i, a, j, len);
1172 : jsr166 1.106 if ((j += len) == size) break;
1173 : jsr166 1.101 }
1174 : jsr166 1.86 if (size < a.length)
1175 :     a[size] = null;
1176 : dl 1.1 return a;
1177 :     }
1178 :    
1179 :     // *** Object methods ***
1180 :    
1181 :     /**
1182 :     * Returns a copy of this deque.
1183 :     *
1184 :     * @return a copy of this deque
1185 :     */
1186 :     public ArrayDeque<E> clone() {
1187 : dl 1.5 try {
1188 : jsr166 1.34 @SuppressWarnings("unchecked")
1189 : dl 1.1 ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
1190 : jsr166 1.28 result.elements = Arrays.copyOf(elements, elements.length);
1191 : dl 1.1 return result;
1192 : dl 1.5 } catch (CloneNotSupportedException e) {
1193 : dl 1.1 throw new AssertionError();
1194 :     }
1195 :     }
1196 :    
1197 :     private static final long serialVersionUID = 2340985798034038923L;
1198 :    
1199 :     /**
1200 : jsr166 1.38 * Saves this deque to a stream (that is, serializes it).
1201 : dl 1.1 *
1202 : jsr166 1.56 * @param s the stream
1203 : jsr166 1.57 * @throws java.io.IOException if an I/O error occurs
1204 : jsr166 1.40 * @serialData The current size ({@code int}) of the deque,
1205 : dl 1.1 * followed by all of its elements (each an object reference) in
1206 :     * first-to-last order.
1207 :     */
1208 : jsr166 1.32 private void writeObject(java.io.ObjectOutputStream s)
1209 :     throws java.io.IOException {
1210 : dl 1.1 s.defaultWriteObject();
1211 :    
1212 :     // Write out size
1213 : jsr166 1.106 s.writeInt(size());
1214 : dl 1.1
1215 :     // Write out elements in order.
1216 : jsr166 1.99 final Object[] es = elements;
1217 : jsr166 1.106 for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1218 :     ; i = 0, to = end) {
1219 : jsr166 1.92 for (; i < to; i++)
1220 : jsr166 1.99 s.writeObject(es[i]);
1221 : jsr166 1.106 if (to == end) break;
1222 : jsr166 1.89 }
1223 : dl 1.1 }
1224 :    
1225 :     /**
1226 : jsr166 1.38 * Reconstitutes this deque from a stream (that is, deserializes it).
1227 : jsr166 1.56 * @param s the stream
1228 : jsr166 1.57 * @throws ClassNotFoundException if the class of a serialized object
1229 :     * could not be found
1230 :     * @throws java.io.IOException if an I/O error occurs
1231 : dl 1.1 */
1232 : jsr166 1.32 private void readObject(java.io.ObjectInputStream s)
1233 :     throws java.io.IOException, ClassNotFoundException {
1234 : dl 1.1 s.defaultReadObject();
1235 :    
1236 :     // Read in size and allocate array
1237 : jsr166 1.106 int size = s.readInt();
1238 :     elements = new Object[size + 1];
1239 :     this.tail = size;
1240 : dl 1.1
1241 :     // Read in all elements in the proper order.
1242 :     for (int i = 0; i < size; i++)
1243 : jsr166 1.34 elements[i] = s.readObject();
1244 : dl 1.1 }
1245 : dl 1.41
1246 : jsr166 1.75 /** debugging */
1247 : jsr166 1.89 void checkInvariants() {
1248 : jsr166 1.114 // Use head and tail fields with empty slot at tail strategy.
1249 :     // head == tail disambiguates to "empty".
1250 : jsr166 1.75 try {
1251 :     int capacity = elements.length;
1252 : jsr166 1.124 // assert 0 <= head && head < capacity;
1253 :     // assert 0 <= tail && tail < capacity;
1254 : jsr166 1.106 // assert capacity > 0;
1255 :     // assert size() < capacity;
1256 :     // assert head == tail || elements[head] != null;
1257 :     // assert elements[tail] == null;
1258 :     // assert head == tail || elements[dec(tail, capacity)] != null;
1259 : jsr166 1.75 } catch (Throwable t) {
1260 : jsr166 1.106 System.err.printf("head=%d tail=%d capacity=%d%n",
1261 :     head, tail, elements.length);
1262 : jsr166 1.75 System.err.printf("elements=%s%n",
1263 :     Arrays.toString(elements));
1264 :     throw t;
1265 : dl 1.41 }
1266 :     }
1267 :    
1268 : dl 1.1 }

Doug Lea
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