1 |
|
/* |
2 |
< |
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
< |
* Expert Group and released to the public domain, as explained at |
4 |
< |
* http://creativecommons.org/publicdomain/zero/1.0/ |
2 |
> |
* 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 |
|
*/ |
5 |
|
|
6 |
|
package java.util; |
7 |
< |
import java.util.Spliterator; |
8 |
< |
import java.util.stream.Stream; |
10 |
< |
import java.util.stream.Streams; |
7 |
> |
|
8 |
> |
import java.io.Serializable; |
9 |
|
import java.util.function.Consumer; |
10 |
|
|
11 |
|
/** |
18 |
|
* when used as a queue. |
19 |
|
* |
20 |
|
* <p>Most {@code ArrayDeque} operations run in amortized constant time. |
21 |
< |
* Exceptions include {@link #remove(Object) remove}, {@link |
22 |
< |
* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence |
23 |
< |
* removeLastOccurrence}, {@link #contains contains}, {@link #iterator |
24 |
< |
* iterator.remove()}, and the bulk operations, all of which run in linear |
25 |
< |
* time. |
21 |
> |
* Exceptions include |
22 |
> |
* {@link #remove(Object) remove}, |
23 |
> |
* {@link #removeFirstOccurrence removeFirstOccurrence}, |
24 |
> |
* {@link #removeLastOccurrence removeLastOccurrence}, |
25 |
> |
* {@link #contains contains}, |
26 |
> |
* {@link #iterator iterator.remove()}, |
27 |
> |
* and the bulk operations, all of which run in linear time. |
28 |
|
* |
29 |
< |
* <p>The iterators returned by this class's {@code iterator} method are |
30 |
< |
* <i>fail-fast</i>: If the deque is modified at any time after the iterator |
31 |
< |
* is created, in any way except through the iterator's own {@code remove} |
32 |
< |
* method, the iterator will generally throw a {@link |
29 |
> |
* <p>The iterators returned by this class's {@link #iterator() iterator} |
30 |
> |
* method are <em>fail-fast</em>: If the deque is modified at any time after |
31 |
> |
* the iterator is created, in any way except through the iterator's own |
32 |
> |
* {@code remove} method, the iterator will generally throw a {@link |
33 |
|
* ConcurrentModificationException}. Thus, in the face of concurrent |
34 |
|
* modification, the iterator fails quickly and cleanly, rather than risking |
35 |
|
* arbitrary, non-deterministic behavior at an undetermined time in the |
53 |
|
* |
54 |
|
* @author Josh Bloch and Doug Lea |
55 |
|
* @since 1.6 |
56 |
< |
* @param <E> the type of elements held in this collection |
56 |
> |
* @param <E> the type of elements held in this deque |
57 |
|
*/ |
58 |
|
public class ArrayDeque<E> extends AbstractCollection<E> |
59 |
< |
implements Deque<E>, Cloneable, java.io.Serializable |
59 |
> |
implements Deque<E>, Cloneable, Serializable |
60 |
|
{ |
61 |
|
/** |
62 |
|
* The array in which the elements of the deque are stored. |
136 |
|
} |
137 |
|
|
138 |
|
/** |
139 |
– |
* Copies the elements from our element array into the specified array, |
140 |
– |
* in order (from first to last element in the deque). It is assumed |
141 |
– |
* that the array is large enough to hold all elements in the deque. |
142 |
– |
* |
143 |
– |
* @return its argument |
144 |
– |
*/ |
145 |
– |
private <T> T[] copyElements(T[] a) { |
146 |
– |
if (head < tail) { |
147 |
– |
System.arraycopy(elements, head, a, 0, size()); |
148 |
– |
} else if (head > tail) { |
149 |
– |
int headPortionLen = elements.length - head; |
150 |
– |
System.arraycopy(elements, head, a, 0, headPortionLen); |
151 |
– |
System.arraycopy(elements, 0, a, headPortionLen, tail); |
152 |
– |
} |
153 |
– |
return a; |
154 |
– |
} |
155 |
– |
|
156 |
– |
/** |
139 |
|
* Constructs an empty array deque with an initial capacity |
140 |
|
* sufficient to hold 16 elements. |
141 |
|
*/ |
247 |
|
} |
248 |
|
|
249 |
|
public E pollFirst() { |
250 |
< |
int h = head; |
250 |
> |
final Object[] elements = this.elements; |
251 |
> |
final int h = head; |
252 |
|
@SuppressWarnings("unchecked") |
253 |
|
E result = (E) elements[h]; |
254 |
|
// Element is null if deque empty |
255 |
< |
if (result == null) |
256 |
< |
return null; |
257 |
< |
elements[h] = null; // Must null out slot |
258 |
< |
head = (h + 1) & (elements.length - 1); |
255 |
> |
if (result != null) { |
256 |
> |
elements[h] = null; // Must null out slot |
257 |
> |
head = (h + 1) & (elements.length - 1); |
258 |
> |
} |
259 |
|
return result; |
260 |
|
} |
261 |
|
|
262 |
|
public E pollLast() { |
263 |
< |
int t = (tail - 1) & (elements.length - 1); |
263 |
> |
final Object[] elements = this.elements; |
264 |
> |
final int t = (tail - 1) & (elements.length - 1); |
265 |
|
@SuppressWarnings("unchecked") |
266 |
|
E result = (E) elements[t]; |
267 |
< |
if (result == null) |
268 |
< |
return null; |
269 |
< |
elements[t] = null; |
270 |
< |
tail = t; |
267 |
> |
if (result != null) { |
268 |
> |
elements[t] = null; |
269 |
> |
tail = t; |
270 |
> |
} |
271 |
|
return result; |
272 |
|
} |
273 |
|
|
317 |
|
* @return {@code true} if the deque contained the specified element |
318 |
|
*/ |
319 |
|
public boolean removeFirstOccurrence(Object o) { |
320 |
< |
if (o == null) |
321 |
< |
return false; |
322 |
< |
int mask = elements.length - 1; |
323 |
< |
int i = head; |
324 |
< |
Object x; |
325 |
< |
while ( (x = elements[i]) != null) { |
326 |
< |
if (o.equals(x)) { |
327 |
< |
delete(i); |
344 |
< |
return true; |
320 |
> |
if (o != null) { |
321 |
> |
int mask = elements.length - 1; |
322 |
> |
int i = head; |
323 |
> |
for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) { |
324 |
> |
if (o.equals(x)) { |
325 |
> |
delete(i); |
326 |
> |
return true; |
327 |
> |
} |
328 |
|
} |
346 |
– |
i = (i + 1) & mask; |
329 |
|
} |
330 |
|
return false; |
331 |
|
} |
343 |
|
* @return {@code true} if the deque contained the specified element |
344 |
|
*/ |
345 |
|
public boolean removeLastOccurrence(Object o) { |
346 |
< |
if (o == null) |
347 |
< |
return false; |
348 |
< |
int mask = elements.length - 1; |
349 |
< |
int i = (tail - 1) & mask; |
350 |
< |
Object x; |
351 |
< |
while ( (x = elements[i]) != null) { |
352 |
< |
if (o.equals(x)) { |
353 |
< |
delete(i); |
372 |
< |
return true; |
346 |
> |
if (o != null) { |
347 |
> |
int mask = elements.length - 1; |
348 |
> |
int i = (tail - 1) & mask; |
349 |
> |
for (Object x; (x = elements[i]) != null; i = (i - 1) & mask) { |
350 |
> |
if (o.equals(x)) { |
351 |
> |
delete(i); |
352 |
> |
return true; |
353 |
> |
} |
354 |
|
} |
374 |
– |
i = (i - 1) & mask; |
355 |
|
} |
356 |
|
return false; |
357 |
|
} |
610 |
|
} |
611 |
|
} |
612 |
|
|
613 |
+ |
/** |
614 |
+ |
* This class is nearly a mirror-image of DeqIterator, using tail |
615 |
+ |
* instead of head for initial cursor, and head instead of tail |
616 |
+ |
* for fence. |
617 |
+ |
*/ |
618 |
|
private class DescendingIterator implements Iterator<E> { |
634 |
– |
/* |
635 |
– |
* This class is nearly a mirror-image of DeqIterator, using |
636 |
– |
* tail instead of head for initial cursor, and head instead of |
637 |
– |
* tail for fence. |
638 |
– |
*/ |
619 |
|
private int cursor = tail; |
620 |
|
private int fence = head; |
621 |
|
private int lastRet = -1; |
656 |
|
* @return {@code true} if this deque contains the specified element |
657 |
|
*/ |
658 |
|
public boolean contains(Object o) { |
659 |
< |
if (o == null) |
660 |
< |
return false; |
661 |
< |
int mask = elements.length - 1; |
662 |
< |
int i = head; |
663 |
< |
Object x; |
664 |
< |
while ( (x = elements[i]) != null) { |
665 |
< |
if (o.equals(x)) |
686 |
< |
return true; |
687 |
< |
i = (i + 1) & mask; |
659 |
> |
if (o != null) { |
660 |
> |
int mask = elements.length - 1; |
661 |
> |
int i = head; |
662 |
> |
for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) { |
663 |
> |
if (o.equals(x)) |
664 |
> |
return true; |
665 |
> |
} |
666 |
|
} |
667 |
|
return false; |
668 |
|
} |
675 |
|
* Returns {@code true} if this deque contained the specified element |
676 |
|
* (or equivalently, if this deque changed as a result of the call). |
677 |
|
* |
678 |
< |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
678 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
679 |
|
* |
680 |
|
* @param o element to be removed from this deque, if present |
681 |
|
* @return {@code true} if this deque contained the specified element |
716 |
|
* @return an array containing all of the elements in this deque |
717 |
|
*/ |
718 |
|
public Object[] toArray() { |
719 |
< |
return copyElements(new Object[size()]); |
719 |
> |
final int head = this.head; |
720 |
> |
final int tail = this.tail; |
721 |
> |
boolean wrap = (tail < head); |
722 |
> |
int end = wrap ? tail + elements.length : tail; |
723 |
> |
Object[] a = Arrays.copyOfRange(elements, head, end); |
724 |
> |
if (wrap) |
725 |
> |
System.arraycopy(elements, 0, a, elements.length - head, tail); |
726 |
> |
return a; |
727 |
|
} |
728 |
|
|
729 |
|
/** |
748 |
|
* The following code can be used to dump the deque into a newly |
749 |
|
* allocated array of {@code String}: |
750 |
|
* |
751 |
< |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
751 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
752 |
|
* |
753 |
|
* Note that {@code toArray(new Object[0])} is identical in function to |
754 |
|
* {@code toArray()}. |
764 |
|
*/ |
765 |
|
@SuppressWarnings("unchecked") |
766 |
|
public <T> T[] toArray(T[] a) { |
767 |
< |
int size = size(); |
768 |
< |
if (a.length < size) |
769 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
770 |
< |
a.getClass().getComponentType(), size); |
771 |
< |
copyElements(a); |
772 |
< |
if (a.length > size) |
773 |
< |
a[size] = null; |
767 |
> |
final int head = this.head; |
768 |
> |
final int tail = this.tail; |
769 |
> |
boolean wrap = (tail < head); |
770 |
> |
int size = (tail - head) + (wrap ? elements.length : 0); |
771 |
> |
int firstLeg = size - (wrap ? tail : 0); |
772 |
> |
int len = a.length; |
773 |
> |
if (size > len) { |
774 |
> |
a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
775 |
> |
a.getClass()); |
776 |
> |
} else { |
777 |
> |
System.arraycopy(elements, head, a, 0, firstLeg); |
778 |
> |
if (size < len) |
779 |
> |
a[size] = null; |
780 |
> |
} |
781 |
> |
if (wrap) |
782 |
> |
System.arraycopy(elements, 0, a, firstLeg, tail); |
783 |
|
return a; |
784 |
|
} |
785 |
|
|
806 |
|
/** |
807 |
|
* Saves this deque to a stream (that is, serializes it). |
808 |
|
* |
809 |
+ |
* @param s the stream |
810 |
+ |
* @throws java.io.IOException if an I/O error occurs |
811 |
|
* @serialData The current size ({@code int}) of the deque, |
812 |
|
* followed by all of its elements (each an object reference) in |
813 |
|
* first-to-last order. |
827 |
|
|
828 |
|
/** |
829 |
|
* Reconstitutes this deque from a stream (that is, deserializes it). |
830 |
+ |
* @param s the stream |
831 |
+ |
* @throws ClassNotFoundException if the class of a serialized object |
832 |
+ |
* could not be found |
833 |
+ |
* @throws java.io.IOException if an I/O error occurs |
834 |
|
*/ |
835 |
|
private void readObject(java.io.ObjectInputStream s) |
836 |
|
throws java.io.IOException, ClassNotFoundException { |
847 |
|
elements[i] = s.readObject(); |
848 |
|
} |
849 |
|
|
850 |
< |
public Stream<E> stream() { |
851 |
< |
int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED; |
852 |
< |
return Streams.stream |
853 |
< |
(() -> new DeqSpliterator<E>(this, head, tail), flags); |
854 |
< |
} |
855 |
< |
public Stream<E> parallelStream() { |
856 |
< |
int flags = Streams.STREAM_IS_ORDERED | Streams.STREAM_IS_SIZED; |
857 |
< |
return Streams.parallelStream |
858 |
< |
(() -> new DeqSpliterator<E>(this, head, tail), flags); |
850 |
> |
public Spliterator<E> spliterator() { |
851 |
> |
return new DeqSpliterator<E>(this, -1, -1); |
852 |
|
} |
853 |
|
|
861 |
– |
|
854 |
|
static final class DeqSpliterator<E> implements Spliterator<E> { |
855 |
|
private final ArrayDeque<E> deq; |
856 |
< |
private final int fence; // initially tail |
857 |
< |
private int index; // current index, modified on traverse/split |
856 |
> |
private int fence; // -1 until first use |
857 |
> |
private int index; // current index, modified on traverse/split |
858 |
|
|
859 |
< |
/** Create new spliterator covering the given array and range */ |
859 |
> |
/** Creates new spliterator covering the given array and range */ |
860 |
|
DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) { |
861 |
< |
this.deq = deq; this.index = origin; this.fence = fence; |
861 |
> |
this.deq = deq; |
862 |
> |
this.index = origin; |
863 |
> |
this.fence = fence; |
864 |
|
} |
865 |
|
|
866 |
< |
public DeqSpliterator<E> trySplit() { |
867 |
< |
int n = deq.elements.length; |
868 |
< |
int h = index, t = fence; |
866 |
> |
private int getFence() { // force initialization |
867 |
> |
int t; |
868 |
> |
if ((t = fence) < 0) { |
869 |
> |
t = fence = deq.tail; |
870 |
> |
index = deq.head; |
871 |
> |
} |
872 |
> |
return t; |
873 |
> |
} |
874 |
> |
|
875 |
> |
public Spliterator<E> trySplit() { |
876 |
> |
int t = getFence(), h = index, n = deq.elements.length; |
877 |
|
if (h != t && ((h + 1) & (n - 1)) != t) { |
878 |
|
if (h > t) |
879 |
|
t += n; |
880 |
|
int m = ((h + t) >>> 1) & (n - 1); |
881 |
< |
return new DeqSpliterator<E>(deq, h, index = m); |
881 |
> |
return new DeqSpliterator<>(deq, h, index = m); |
882 |
|
} |
883 |
|
return null; |
884 |
|
} |
885 |
|
|
886 |
< |
public void forEach(Consumer<? super E> block) { |
887 |
< |
if (block == null) |
886 |
> |
public void forEachRemaining(Consumer<? super E> consumer) { |
887 |
> |
if (consumer == null) |
888 |
|
throw new NullPointerException(); |
889 |
|
Object[] a = deq.elements; |
890 |
< |
int m = a.length - 1, f = fence, i = index; |
890 |
> |
int m = a.length - 1, f = getFence(), i = index; |
891 |
|
index = f; |
892 |
|
while (i != f) { |
893 |
|
@SuppressWarnings("unchecked") E e = (E)a[i]; |
894 |
|
i = (i + 1) & m; |
895 |
|
if (e == null) |
896 |
|
throw new ConcurrentModificationException(); |
897 |
< |
block.accept(e); |
897 |
> |
consumer.accept(e); |
898 |
|
} |
899 |
|
} |
900 |
|
|
901 |
< |
public boolean tryAdvance(Consumer<? super E> block) { |
902 |
< |
if (block == null) |
901 |
> |
public boolean tryAdvance(Consumer<? super E> consumer) { |
902 |
> |
if (consumer == null) |
903 |
|
throw new NullPointerException(); |
904 |
|
Object[] a = deq.elements; |
905 |
< |
int m = a.length - 1, i = index; |
906 |
< |
if (i != fence) { |
905 |
> |
int m = a.length - 1, f = getFence(), i = index; |
906 |
> |
if (i != f) { |
907 |
|
@SuppressWarnings("unchecked") E e = (E)a[i]; |
908 |
|
index = (i + 1) & m; |
909 |
|
if (e == null) |
910 |
|
throw new ConcurrentModificationException(); |
911 |
< |
block.accept(e); |
911 |
> |
consumer.accept(e); |
912 |
|
return true; |
913 |
|
} |
914 |
|
return false; |
915 |
|
} |
916 |
|
|
915 |
– |
// Other spliterator methods |
917 |
|
public long estimateSize() { |
918 |
< |
int n = fence - index; |
918 |
> |
int n = getFence() - index; |
919 |
|
if (n < 0) |
920 |
|
n += deq.elements.length; |
921 |
< |
return (long)n; |
921 |
> |
return (long) n; |
922 |
> |
} |
923 |
> |
|
924 |
> |
@Override |
925 |
> |
public int characteristics() { |
926 |
> |
return Spliterator.ORDERED | Spliterator.SIZED | |
927 |
> |
Spliterator.NONNULL | Spliterator.SUBSIZED; |
928 |
|
} |
922 |
– |
public boolean hasExactSize() { return true; } |
923 |
– |
public boolean hasExactSplits() { return true; } |
929 |
|
} |
930 |
|
|
931 |
|
} |