4 |
|
*/ |
5 |
|
|
6 |
|
package java.util; |
7 |
+ |
import java.io.Serializable; |
8 |
+ |
import java.util.function.Consumer; |
9 |
+ |
import java.util.stream.Stream; |
10 |
+ |
import java.util.stream.Streams; |
11 |
|
|
12 |
|
/** |
13 |
|
* Resizable-array implementation of the {@link Deque} interface. Array |
57 |
|
* @param <E> the type of elements held in this collection |
58 |
|
*/ |
59 |
|
public class ArrayDeque<E> extends AbstractCollection<E> |
60 |
< |
implements Deque<E>, Cloneable, java.io.Serializable |
60 |
> |
implements Deque<E>, Cloneable, Serializable |
61 |
|
{ |
62 |
|
/** |
63 |
|
* The array in which the elements of the deque are stored. |
69 |
|
* other. We also guarantee that all array cells not holding |
70 |
|
* deque elements are always null. |
71 |
|
*/ |
72 |
< |
private transient Object[] elements; |
72 |
> |
transient Object[] elements; // non-private to simplify nested class access |
73 |
|
|
74 |
|
/** |
75 |
|
* The index of the element at the head of the deque (which is the |
76 |
|
* element that would be removed by remove() or pop()); or an |
77 |
|
* arbitrary number equal to tail if the deque is empty. |
78 |
|
*/ |
79 |
< |
private transient int head; |
79 |
> |
transient int head; |
80 |
|
|
81 |
|
/** |
82 |
|
* The index at which the next element would be added to the tail |
83 |
|
* of the deque (via addLast(E), add(E), or push(E)). |
84 |
|
*/ |
85 |
< |
private transient int tail; |
85 |
> |
transient int tail; |
86 |
|
|
87 |
|
/** |
88 |
|
* The minimum capacity that we'll use for a newly created deque. |
137 |
|
} |
138 |
|
|
139 |
|
/** |
136 |
– |
* Copies the elements from our element array into the specified array, |
137 |
– |
* in order (from first to last element in the deque). It is assumed |
138 |
– |
* that the array is large enough to hold all elements in the deque. |
139 |
– |
* |
140 |
– |
* @return its argument |
141 |
– |
*/ |
142 |
– |
private <T> T[] copyElements(T[] a) { |
143 |
– |
if (head < tail) { |
144 |
– |
System.arraycopy(elements, head, a, 0, size()); |
145 |
– |
} else if (head > tail) { |
146 |
– |
int headPortionLen = elements.length - head; |
147 |
– |
System.arraycopy(elements, head, a, 0, headPortionLen); |
148 |
– |
System.arraycopy(elements, 0, a, headPortionLen, tail); |
149 |
– |
} |
150 |
– |
return a; |
151 |
– |
} |
152 |
– |
|
153 |
– |
/** |
140 |
|
* Constructs an empty array deque with an initial capacity |
141 |
|
* sufficient to hold 16 elements. |
142 |
|
*/ |
613 |
|
} |
614 |
|
} |
615 |
|
|
616 |
+ |
/** |
617 |
+ |
* This class is nearly a mirror-image of DeqIterator, using tail |
618 |
+ |
* instead of head for initial cursor, and head instead of tail |
619 |
+ |
* for fence. |
620 |
+ |
*/ |
621 |
|
private class DescendingIterator implements Iterator<E> { |
631 |
– |
/* |
632 |
– |
* This class is nearly a mirror-image of DeqIterator, using |
633 |
– |
* tail instead of head for initial cursor, and head instead of |
634 |
– |
* tail for fence. |
635 |
– |
*/ |
622 |
|
private int cursor = tail; |
623 |
|
private int fence = head; |
624 |
|
private int lastRet = -1; |
680 |
|
* Returns {@code true} if this deque contained the specified element |
681 |
|
* (or equivalently, if this deque changed as a result of the call). |
682 |
|
* |
683 |
< |
* <p>This method is equivalent to {@link #removeFirstOccurrence}. |
683 |
> |
* <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. |
684 |
|
* |
685 |
|
* @param o element to be removed from this deque, if present |
686 |
|
* @return {@code true} if this deque contained the specified element |
721 |
|
* @return an array containing all of the elements in this deque |
722 |
|
*/ |
723 |
|
public Object[] toArray() { |
724 |
< |
return copyElements(new Object[size()]); |
724 |
> |
final int head = this.head; |
725 |
> |
final int tail = this.tail; |
726 |
> |
boolean wrap = (tail < head); |
727 |
> |
int end = wrap ? tail + elements.length : tail; |
728 |
> |
Object[] a = Arrays.copyOfRange(elements, head, end); |
729 |
> |
if (wrap) |
730 |
> |
System.arraycopy(elements, 0, a, elements.length - head, tail); |
731 |
> |
return a; |
732 |
|
} |
733 |
|
|
734 |
|
/** |
769 |
|
*/ |
770 |
|
@SuppressWarnings("unchecked") |
771 |
|
public <T> T[] toArray(T[] a) { |
772 |
< |
int size = size(); |
773 |
< |
if (a.length < size) |
774 |
< |
a = (T[])java.lang.reflect.Array.newInstance( |
775 |
< |
a.getClass().getComponentType(), size); |
776 |
< |
copyElements(a); |
777 |
< |
if (a.length > size) |
778 |
< |
a[size] = null; |
772 |
> |
final int head = this.head; |
773 |
> |
final int tail = this.tail; |
774 |
> |
boolean wrap = (tail < head); |
775 |
> |
int size = (tail - head) + (wrap ? elements.length : 0); |
776 |
> |
int firstLeg = size - (wrap ? tail : 0); |
777 |
> |
int len = a.length; |
778 |
> |
if (size > len) { |
779 |
> |
a = (T[]) Arrays.copyOfRange(elements, head, head + size, |
780 |
> |
a.getClass()); |
781 |
> |
} else { |
782 |
> |
System.arraycopy(elements, head, a, 0, firstLeg); |
783 |
> |
if (size < len) |
784 |
> |
a[size] = null; |
785 |
> |
} |
786 |
> |
if (wrap) |
787 |
> |
System.arraycopy(elements, 0, a, firstLeg, tail); |
788 |
|
return a; |
789 |
|
} |
790 |
|
|
845 |
|
for (int i = 0; i < size; i++) |
846 |
|
elements[i] = s.readObject(); |
847 |
|
} |
848 |
+ |
|
849 |
+ |
public Spliterator<E> spliterator() { |
850 |
+ |
return new DeqSpliterator<E>(this, -1, -1); |
851 |
+ |
} |
852 |
+ |
|
853 |
+ |
static final class DeqSpliterator<E> implements Spliterator<E> { |
854 |
+ |
private final ArrayDeque<E> deq; |
855 |
+ |
private int fence; // -1 until first use |
856 |
+ |
private int index; // current index, modified on traverse/split |
857 |
+ |
|
858 |
+ |
/** Creates new spliterator covering the given array and range */ |
859 |
+ |
DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) { |
860 |
+ |
this.deq = deq; |
861 |
+ |
this.index = origin; |
862 |
+ |
this.fence = fence; |
863 |
+ |
} |
864 |
+ |
|
865 |
+ |
private int getFence() { // force initialization |
866 |
+ |
int t; |
867 |
+ |
if ((t = fence) < 0) { |
868 |
+ |
t = fence = deq.tail; |
869 |
+ |
index = deq.head; |
870 |
+ |
} |
871 |
+ |
return t; |
872 |
+ |
} |
873 |
+ |
|
874 |
+ |
public Spliterator<E> trySplit() { |
875 |
+ |
int t = getFence(), h = index, n = deq.elements.length; |
876 |
+ |
if (h != t && ((h + 1) & (n - 1)) != t) { |
877 |
+ |
if (h > t) |
878 |
+ |
t += n; |
879 |
+ |
int m = ((h + t) >>> 1) & (n - 1); |
880 |
+ |
return new DeqSpliterator<>(deq, h, index = m); |
881 |
+ |
} |
882 |
+ |
return null; |
883 |
+ |
} |
884 |
+ |
|
885 |
+ |
public void forEachRemaining(Consumer<? super E> consumer) { |
886 |
+ |
if (consumer == null) |
887 |
+ |
throw new NullPointerException(); |
888 |
+ |
Object[] a = deq.elements; |
889 |
+ |
int m = a.length - 1, f = getFence(), i = index; |
890 |
+ |
index = f; |
891 |
+ |
while (i != f) { |
892 |
+ |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
893 |
+ |
i = (i + 1) & m; |
894 |
+ |
if (e == null) |
895 |
+ |
throw new ConcurrentModificationException(); |
896 |
+ |
consumer.accept(e); |
897 |
+ |
} |
898 |
+ |
} |
899 |
+ |
|
900 |
+ |
public boolean tryAdvance(Consumer<? super E> consumer) { |
901 |
+ |
if (consumer == null) |
902 |
+ |
throw new NullPointerException(); |
903 |
+ |
Object[] a = deq.elements; |
904 |
+ |
int m = a.length - 1, f = getFence(), i = index; |
905 |
+ |
if (i != fence) { |
906 |
+ |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
907 |
+ |
index = (i + 1) & m; |
908 |
+ |
if (e == null) |
909 |
+ |
throw new ConcurrentModificationException(); |
910 |
+ |
consumer.accept(e); |
911 |
+ |
return true; |
912 |
+ |
} |
913 |
+ |
return false; |
914 |
+ |
} |
915 |
+ |
|
916 |
+ |
public long estimateSize() { |
917 |
+ |
int n = getFence() - index; |
918 |
+ |
if (n < 0) |
919 |
+ |
n += deq.elements.length; |
920 |
+ |
return (long) n; |
921 |
+ |
} |
922 |
+ |
|
923 |
+ |
@Override |
924 |
+ |
public int characteristics() { |
925 |
+ |
return Spliterator.ORDERED | Spliterator.SIZED | |
926 |
+ |
Spliterator.NONNULL | Spliterator.SUBSIZED; |
927 |
+ |
} |
928 |
+ |
} |
929 |
+ |
|
930 |
|
} |