4 |
|
*/ |
5 |
|
|
6 |
|
package java.util; |
7 |
+ |
|
8 |
|
import java.io.Serializable; |
9 |
|
import java.util.function.Consumer; |
9 |
– |
import java.util.stream.Stream; |
10 |
– |
import java.util.stream.Streams; |
10 |
|
|
11 |
|
/** |
12 |
|
* Resizable-array implementation of the {@link Deque} interface. Array |
18 |
|
* when used as a queue. |
19 |
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* |
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 |
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* 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, Serializable |
109 |
|
initialCapacity |= (initialCapacity >>> 16); |
110 |
|
initialCapacity++; |
111 |
|
|
112 |
< |
if (initialCapacity < 0) // Too many elements, must back off |
113 |
< |
initialCapacity >>>= 1;// Good luck allocating 2 ^ 30 elements |
112 |
> |
if (initialCapacity < 0) // Too many elements, must back off |
113 |
> |
initialCapacity >>>= 1; // Good luck allocating 2^30 elements |
114 |
|
} |
115 |
|
elements = new Object[initialCapacity]; |
116 |
|
} |
136 |
|
} |
137 |
|
|
138 |
|
/** |
138 |
– |
* Copies the elements from our element array into the specified array, |
139 |
– |
* in order (from first to last element in the deque). It is assumed |
140 |
– |
* that the array is large enough to hold all elements in the deque. |
141 |
– |
* |
142 |
– |
* @return its argument |
143 |
– |
*/ |
144 |
– |
private <T> T[] copyElements(T[] a) { |
145 |
– |
if (head < tail) { |
146 |
– |
System.arraycopy(elements, head, a, 0, size()); |
147 |
– |
} else if (head > tail) { |
148 |
– |
int headPortionLen = elements.length - head; |
149 |
– |
System.arraycopy(elements, head, a, 0, headPortionLen); |
150 |
– |
System.arraycopy(elements, 0, a, headPortionLen, tail); |
151 |
– |
} |
152 |
– |
return a; |
153 |
– |
} |
154 |
– |
|
155 |
– |
/** |
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); |
343 |
< |
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 |
|
} |
345 |
– |
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); |
371 |
< |
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 |
|
} |
373 |
– |
i = (i - 1) & mask; |
355 |
|
} |
356 |
|
return false; |
357 |
|
} |
608 |
|
} |
609 |
|
lastRet = -1; |
610 |
|
} |
611 |
+ |
|
612 |
+ |
public void forEachRemaining(Consumer<? super E> action) { |
613 |
+ |
Objects.requireNonNull(action); |
614 |
+ |
Object[] a = elements; |
615 |
+ |
int m = a.length - 1, f = fence, i = cursor; |
616 |
+ |
cursor = f; |
617 |
+ |
while (i != f) { |
618 |
+ |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
619 |
+ |
i = (i + 1) & m; |
620 |
+ |
if (e == null) |
621 |
+ |
throw new ConcurrentModificationException(); |
622 |
+ |
action.accept(e); |
623 |
+ |
} |
624 |
+ |
} |
625 |
|
} |
626 |
|
|
627 |
+ |
/** |
628 |
+ |
* This class is nearly a mirror-image of DeqIterator, using tail |
629 |
+ |
* instead of head for initial cursor, and head instead of tail |
630 |
+ |
* for fence. |
631 |
+ |
*/ |
632 |
|
private class DescendingIterator implements Iterator<E> { |
633 |
– |
/* |
634 |
– |
* This class is nearly a mirror-image of DeqIterator, using |
635 |
– |
* tail instead of head for initial cursor, and head instead of |
636 |
– |
* tail for fence. |
637 |
– |
*/ |
633 |
|
private int cursor = tail; |
634 |
|
private int fence = head; |
635 |
|
private int lastRet = -1; |
670 |
|
* @return {@code true} if this deque contains the specified element |
671 |
|
*/ |
672 |
|
public boolean contains(Object o) { |
673 |
< |
if (o == null) |
674 |
< |
return false; |
675 |
< |
int mask = elements.length - 1; |
676 |
< |
int i = head; |
677 |
< |
Object x; |
678 |
< |
while ( (x = elements[i]) != null) { |
679 |
< |
if (o.equals(x)) |
685 |
< |
return true; |
686 |
< |
i = (i + 1) & mask; |
673 |
> |
if (o != null) { |
674 |
> |
int mask = elements.length - 1; |
675 |
> |
int i = head; |
676 |
> |
for (Object x; (x = elements[i]) != null; i = (i + 1) & mask) { |
677 |
> |
if (o.equals(x)) |
678 |
> |
return true; |
679 |
> |
} |
680 |
|
} |
681 |
|
return false; |
682 |
|
} |
730 |
|
* @return an array containing all of the elements in this deque |
731 |
|
*/ |
732 |
|
public Object[] toArray() { |
733 |
< |
return copyElements(new Object[size()]); |
733 |
> |
final int head = this.head; |
734 |
> |
final int tail = this.tail; |
735 |
> |
boolean wrap = (tail < head); |
736 |
> |
int end = wrap ? tail + elements.length : tail; |
737 |
> |
Object[] a = Arrays.copyOfRange(elements, head, end); |
738 |
> |
if (wrap) |
739 |
> |
System.arraycopy(elements, 0, a, elements.length - head, tail); |
740 |
> |
return a; |
741 |
|
} |
742 |
|
|
743 |
|
/** |
762 |
|
* The following code can be used to dump the deque into a newly |
763 |
|
* allocated array of {@code String}: |
764 |
|
* |
765 |
< |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
765 |
> |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
766 |
|
* |
767 |
|
* Note that {@code toArray(new Object[0])} is identical in function to |
768 |
|
* {@code toArray()}. |
778 |
|
*/ |
779 |
|
@SuppressWarnings("unchecked") |
780 |
|
public <T> T[] toArray(T[] a) { |
781 |
< |
int size = size(); |
782 |
< |
if (a.length < size) |
783 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
784 |
< |
a.getClass().getComponentType(), size); |
785 |
< |
copyElements(a); |
786 |
< |
if (a.length > size) |
787 |
< |
a[size] = null; |
781 |
> |
final int head = this.head; |
782 |
> |
final int tail = this.tail; |
783 |
> |
boolean wrap = (tail < head); |
784 |
> |
int size = (tail - head) + (wrap ? elements.length : 0); |
785 |
> |
int firstLeg = size - (wrap ? tail : 0); |
786 |
> |
int len = a.length; |
787 |
> |
if (size > len) { |
788 |
> |
a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
789 |
> |
a.getClass()); |
790 |
> |
} else { |
791 |
> |
System.arraycopy(elements, head, a, 0, firstLeg); |
792 |
> |
if (size < len) |
793 |
> |
a[size] = null; |
794 |
> |
} |
795 |
> |
if (wrap) |
796 |
> |
System.arraycopy(elements, 0, a, firstLeg, tail); |
797 |
|
return a; |
798 |
|
} |
799 |
|
|
820 |
|
/** |
821 |
|
* Saves this deque to a stream (that is, serializes it). |
822 |
|
* |
823 |
+ |
* @param s the stream |
824 |
+ |
* @throws java.io.IOException if an I/O error occurs |
825 |
|
* @serialData The current size ({@code int}) of the deque, |
826 |
|
* followed by all of its elements (each an object reference) in |
827 |
|
* first-to-last order. |
841 |
|
|
842 |
|
/** |
843 |
|
* Reconstitutes this deque from a stream (that is, deserializes it). |
844 |
+ |
* @param s the stream |
845 |
+ |
* @throws ClassNotFoundException if the class of a serialized object |
846 |
+ |
* could not be found |
847 |
+ |
* @throws java.io.IOException if an I/O error occurs |
848 |
|
*/ |
849 |
|
private void readObject(java.io.ObjectInputStream s) |
850 |
|
throws java.io.IOException, ClassNotFoundException { |
861 |
|
elements[i] = s.readObject(); |
862 |
|
} |
863 |
|
|
864 |
< |
Spliterator<E> spliterator() { |
865 |
< |
return new DeqSpliterator<E>(this, -1, -1); |
866 |
< |
} |
867 |
< |
|
868 |
< |
public Stream<E> stream() { |
869 |
< |
return Streams.stream(spliterator()); |
870 |
< |
} |
871 |
< |
|
872 |
< |
public Stream<E> parallelStream() { |
873 |
< |
return Streams.parallelStream(spliterator()); |
864 |
> |
/** |
865 |
> |
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
866 |
> |
* and <em>fail-fast</em> {@link Spliterator} over the elements in this |
867 |
> |
* deque. |
868 |
> |
* |
869 |
> |
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED}, |
870 |
> |
* {@link Spliterator#SUBSIZED}, {@link Spliterator#ORDERED}, and |
871 |
> |
* {@link Spliterator#NONNULL}. Overriding implementations should document |
872 |
> |
* the reporting of additional characteristic values. |
873 |
> |
* |
874 |
> |
* @return a {@code Spliterator} over the elements in this deque |
875 |
> |
* @since 1.8 |
876 |
> |
*/ |
877 |
> |
public Spliterator<E> spliterator() { |
878 |
> |
return new DeqSpliterator<>(this, -1, -1); |
879 |
|
} |
880 |
|
|
881 |
|
static final class DeqSpliterator<E> implements Spliterator<E> { |
882 |
|
private final ArrayDeque<E> deq; |
883 |
|
private int fence; // -1 until first use |
884 |
|
private int index; // current index, modified on traverse/split |
885 |
< |
|
886 |
< |
/** Create new spliterator covering the given array and range */ |
885 |
> |
|
886 |
> |
/** Creates new spliterator covering the given array and range */ |
887 |
|
DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) { |
888 |
|
this.deq = deq; |
889 |
|
this.index = origin; |
899 |
|
return t; |
900 |
|
} |
901 |
|
|
902 |
< |
public DeqSpliterator<E> trySplit() { |
902 |
> |
public Spliterator<E> trySplit() { |
903 |
|
int t = getFence(), h = index, n = deq.elements.length; |
904 |
|
if (h != t && ((h + 1) & (n - 1)) != t) { |
905 |
|
if (h > t) |
910 |
|
return null; |
911 |
|
} |
912 |
|
|
913 |
< |
public void forEach(Consumer<? super E> consumer) { |
913 |
> |
public void forEachRemaining(Consumer<? super E> consumer) { |
914 |
|
if (consumer == null) |
915 |
|
throw new NullPointerException(); |
916 |
|
Object[] a = deq.elements; |
930 |
|
throw new NullPointerException(); |
931 |
|
Object[] a = deq.elements; |
932 |
|
int m = a.length - 1, f = getFence(), i = index; |
933 |
< |
if (i != fence) { |
933 |
> |
if (i != f) { |
934 |
|
@SuppressWarnings("unchecked") E e = (E)a[i]; |
935 |
|
index = (i + 1) & m; |
936 |
|
if (e == null) |
950 |
|
|
951 |
|
@Override |
952 |
|
public int characteristics() { |
953 |
< |
return Spliterator.ORDERED | Spliterator.SIZED | |
953 |
> |
return Spliterator.ORDERED | Spliterator.SIZED | |
954 |
|
Spliterator.NONNULL | Spliterator.SUBSIZED; |
955 |
|
} |
956 |
|
} |