| 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 |
| 18 |
|
* {@link Stack} when used as a stack, and faster than {@link LinkedList} |
| 19 |
|
* when used as a queue. |
| 20 |
|
* |
| 21 |
< |
* <p>Most <tt>ArrayDeque</tt> operations run in amortized constant time. |
| 22 |
< |
* Exceptions include {@link #remove(Object) remove}, {@link |
| 23 |
< |
* #removeFirstOccurrence removeFirstOccurrence}, {@link #removeLastOccurrence |
| 24 |
< |
* removeLastOccurrence}, {@link #contains contains}, {@link #iterator |
| 25 |
< |
* iterator.remove()}, and the bulk operations, all of which run in linear |
| 26 |
< |
* time. |
| 21 |
> |
* <p>Most {@code ArrayDeque} operations run in amortized constant time. |
| 22 |
> |
* Exceptions include |
| 23 |
> |
* {@link #remove(Object) remove}, |
| 24 |
> |
* {@link #removeFirstOccurrence removeFirstOccurrence}, |
| 25 |
> |
* {@link #removeLastOccurrence removeLastOccurrence}, |
| 26 |
> |
* {@link #contains contains}, |
| 27 |
> |
* {@link #iterator iterator.remove()}, |
| 28 |
> |
* and the bulk operations, all of which run in linear time. |
| 29 |
|
* |
| 30 |
< |
* <p>The iterators returned by this class's <tt>iterator</tt> method are |
| 31 |
< |
* <i>fail-fast</i>: If the deque is modified at any time after the iterator |
| 32 |
< |
* is created, in any way except through the iterator's own <tt>remove</tt> |
| 33 |
< |
* method, the iterator will generally throw a {@link |
| 30 |
> |
* <p>The iterators returned by this class's {@link #iterator() iterator} |
| 31 |
> |
* method are <em>fail-fast</em>: If the deque is modified at any time after |
| 32 |
> |
* the iterator is created, in any way except through the iterator's own |
| 33 |
> |
* {@code remove} method, the iterator will generally throw a {@link |
| 34 |
|
* ConcurrentModificationException}. Thus, in the face of concurrent |
| 35 |
|
* modification, the iterator fails quickly and cleanly, rather than risking |
| 36 |
|
* arbitrary, non-deterministic behavior at an undetermined time in the |
| 39 |
|
* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
| 40 |
|
* as it is, generally speaking, impossible to make any hard guarantees in the |
| 41 |
|
* presence of unsynchronized concurrent modification. Fail-fast iterators |
| 42 |
< |
* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
| 42 |
> |
* throw {@code ConcurrentModificationException} on a best-effort basis. |
| 43 |
|
* Therefore, it would be wrong to write a program that depended on this |
| 44 |
|
* exception for its correctness: <i>the fail-fast behavior of iterators |
| 45 |
|
* should be used only to detect bugs.</i> |
| 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 |
|
/** |
| 134 |
– |
* Copies the elements from our element array into the specified array, |
| 135 |
– |
* in order (from first to last element in the deque). It is assumed |
| 136 |
– |
* that the array is large enough to hold all elements in the deque. |
| 137 |
– |
* |
| 138 |
– |
* @return its argument |
| 139 |
– |
*/ |
| 140 |
– |
private <T> T[] copyElements(T[] a) { |
| 141 |
– |
if (head < tail) { |
| 142 |
– |
System.arraycopy(elements, head, a, 0, size()); |
| 143 |
– |
} else if (head > tail) { |
| 144 |
– |
int headPortionLen = elements.length - head; |
| 145 |
– |
System.arraycopy(elements, head, a, 0, headPortionLen); |
| 146 |
– |
System.arraycopy(elements, 0, a, headPortionLen, tail); |
| 147 |
– |
} |
| 148 |
– |
return a; |
| 149 |
– |
} |
| 150 |
– |
|
| 151 |
– |
/** |
| 140 |
|
* Constructs an empty array deque with an initial capacity |
| 141 |
|
* sufficient to hold 16 elements. |
| 142 |
|
*/ |
| 207 |
|
* Inserts the specified element at the front of this deque. |
| 208 |
|
* |
| 209 |
|
* @param e the element to add |
| 210 |
< |
* @return <tt>true</tt> (as specified by {@link Deque#offerFirst}) |
| 210 |
> |
* @return {@code true} (as specified by {@link Deque#offerFirst}) |
| 211 |
|
* @throws NullPointerException if the specified element is null |
| 212 |
|
*/ |
| 213 |
|
public boolean offerFirst(E e) { |
| 219 |
|
* Inserts the specified element at the end of this deque. |
| 220 |
|
* |
| 221 |
|
* @param e the element to add |
| 222 |
< |
* @return <tt>true</tt> (as specified by {@link Deque#offerLast}) |
| 222 |
> |
* @return {@code true} (as specified by {@link Deque#offerLast}) |
| 223 |
|
* @throws NullPointerException if the specified element is null |
| 224 |
|
*/ |
| 225 |
|
public boolean offerLast(E e) { |
| 307 |
|
* Removes the first occurrence of the specified element in this |
| 308 |
|
* deque (when traversing the deque from head to tail). |
| 309 |
|
* If the deque does not contain the element, it is unchanged. |
| 310 |
< |
* More formally, removes the first element <tt>e</tt> such that |
| 311 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
| 312 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
| 310 |
> |
* More formally, removes the first element {@code e} such that |
| 311 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 312 |
> |
* Returns {@code true} if this deque contained the specified element |
| 313 |
|
* (or equivalently, if this deque changed as a result of the call). |
| 314 |
|
* |
| 315 |
|
* @param o element to be removed from this deque, if present |
| 316 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
| 316 |
> |
* @return {@code true} if the deque contained the specified element |
| 317 |
|
*/ |
| 318 |
|
public boolean removeFirstOccurrence(Object o) { |
| 319 |
|
if (o == null) |
| 335 |
|
* Removes the last occurrence of the specified element in this |
| 336 |
|
* deque (when traversing the deque from head to tail). |
| 337 |
|
* If the deque does not contain the element, it is unchanged. |
| 338 |
< |
* More formally, removes the last element <tt>e</tt> such that |
| 339 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
| 340 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
| 338 |
> |
* More formally, removes the last element {@code e} such that |
| 339 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 340 |
> |
* Returns {@code true} if this deque contained the specified element |
| 341 |
|
* (or equivalently, if this deque changed as a result of the call). |
| 342 |
|
* |
| 343 |
|
* @param o element to be removed from this deque, if present |
| 344 |
< |
* @return <tt>true</tt> if the deque contained the specified element |
| 344 |
> |
* @return {@code true} if the deque contained the specified element |
| 345 |
|
*/ |
| 346 |
|
public boolean removeLastOccurrence(Object o) { |
| 347 |
|
if (o == null) |
| 367 |
|
* <p>This method is equivalent to {@link #addLast}. |
| 368 |
|
* |
| 369 |
|
* @param e the element to add |
| 370 |
< |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
| 370 |
> |
* @return {@code true} (as specified by {@link Collection#add}) |
| 371 |
|
* @throws NullPointerException if the specified element is null |
| 372 |
|
*/ |
| 373 |
|
public boolean add(E e) { |
| 381 |
|
* <p>This method is equivalent to {@link #offerLast}. |
| 382 |
|
* |
| 383 |
|
* @param e the element to add |
| 384 |
< |
* @return <tt>true</tt> (as specified by {@link Queue#offer}) |
| 384 |
> |
* @return {@code true} (as specified by {@link Queue#offer}) |
| 385 |
|
* @throws NullPointerException if the specified element is null |
| 386 |
|
*/ |
| 387 |
|
public boolean offer(E e) { |
| 406 |
|
/** |
| 407 |
|
* Retrieves and removes the head of the queue represented by this deque |
| 408 |
|
* (in other words, the first element of this deque), or returns |
| 409 |
< |
* <tt>null</tt> if this deque is empty. |
| 409 |
> |
* {@code null} if this deque is empty. |
| 410 |
|
* |
| 411 |
|
* <p>This method is equivalent to {@link #pollFirst}. |
| 412 |
|
* |
| 413 |
|
* @return the head of the queue represented by this deque, or |
| 414 |
< |
* <tt>null</tt> if this deque is empty |
| 414 |
> |
* {@code null} if this deque is empty |
| 415 |
|
*/ |
| 416 |
|
public E poll() { |
| 417 |
|
return pollFirst(); |
| 433 |
|
|
| 434 |
|
/** |
| 435 |
|
* Retrieves, but does not remove, the head of the queue represented by |
| 436 |
< |
* this deque, or returns <tt>null</tt> if this deque is empty. |
| 436 |
> |
* this deque, or returns {@code null} if this deque is empty. |
| 437 |
|
* |
| 438 |
|
* <p>This method is equivalent to {@link #peekFirst}. |
| 439 |
|
* |
| 440 |
|
* @return the head of the queue represented by this deque, or |
| 441 |
< |
* <tt>null</tt> if this deque is empty |
| 441 |
> |
* {@code null} if this deque is empty |
| 442 |
|
*/ |
| 443 |
|
public E peek() { |
| 444 |
|
return peekFirst(); |
| 542 |
|
} |
| 543 |
|
|
| 544 |
|
/** |
| 545 |
< |
* Returns <tt>true</tt> if this deque contains no elements. |
| 545 |
> |
* Returns {@code true} if this deque contains no elements. |
| 546 |
|
* |
| 547 |
< |
* @return <tt>true</tt> if this deque contains no elements |
| 547 |
> |
* @return {@code true} if this deque contains no elements |
| 548 |
|
*/ |
| 549 |
|
public boolean isEmpty() { |
| 550 |
|
return head == tail; |
| 651 |
|
} |
| 652 |
|
|
| 653 |
|
/** |
| 654 |
< |
* Returns <tt>true</tt> if this deque contains the specified element. |
| 655 |
< |
* More formally, returns <tt>true</tt> if and only if this deque contains |
| 656 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
| 654 |
> |
* Returns {@code true} if this deque contains the specified element. |
| 655 |
> |
* More formally, returns {@code true} if and only if this deque contains |
| 656 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
| 657 |
|
* |
| 658 |
|
* @param o object to be checked for containment in this deque |
| 659 |
< |
* @return <tt>true</tt> if this deque contains the specified element |
| 659 |
> |
* @return {@code true} if this deque contains the specified element |
| 660 |
|
*/ |
| 661 |
|
public boolean contains(Object o) { |
| 662 |
|
if (o == null) |
| 675 |
|
/** |
| 676 |
|
* Removes a single instance of the specified element from this deque. |
| 677 |
|
* If the deque does not contain the element, it is unchanged. |
| 678 |
< |
* More formally, removes the first element <tt>e</tt> such that |
| 679 |
< |
* <tt>o.equals(e)</tt> (if such an element exists). |
| 680 |
< |
* Returns <tt>true</tt> if this deque contained the specified element |
| 678 |
> |
* More formally, removes the first element {@code e} such that |
| 679 |
> |
* {@code o.equals(e)} (if such an element exists). |
| 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 <tt>true</tt> if this deque contained the specified element |
| 686 |
> |
* @return {@code true} if this deque contained the specified element |
| 687 |
|
*/ |
| 688 |
|
public boolean remove(Object o) { |
| 689 |
|
return removeFirstOccurrence(o); |
| 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 |
|
/** |
| 742 |
|
* <p>If this deque fits in the specified array with room to spare |
| 743 |
|
* (i.e., the array has more elements than this deque), the element in |
| 744 |
|
* the array immediately following the end of the deque is set to |
| 745 |
< |
* <tt>null</tt>. |
| 745 |
> |
* {@code null}. |
| 746 |
|
* |
| 747 |
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
| 748 |
|
* array-based and collection-based APIs. Further, this method allows |
| 749 |
|
* precise control over the runtime type of the output array, and may, |
| 750 |
|
* under certain circumstances, be used to save allocation costs. |
| 751 |
|
* |
| 752 |
< |
* <p>Suppose <tt>x</tt> is a deque known to contain only strings. |
| 752 |
> |
* <p>Suppose {@code x} is a deque known to contain only strings. |
| 753 |
|
* The following code can be used to dump the deque into a newly |
| 754 |
< |
* allocated array of <tt>String</tt>: |
| 754 |
> |
* allocated array of {@code String}: |
| 755 |
|
* |
| 756 |
|
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
| 757 |
|
* |
| 758 |
< |
* Note that <tt>toArray(new Object[0])</tt> is identical in function to |
| 759 |
< |
* <tt>toArray()</tt>. |
| 758 |
> |
* Note that {@code toArray(new Object[0])} is identical in function to |
| 759 |
> |
* {@code toArray()}. |
| 760 |
|
* |
| 761 |
|
* @param a the array into which the elements of the deque are to |
| 762 |
|
* be stored, if it is big enough; otherwise, a new array of the |
| 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 |
|
|
| 811 |
|
/** |
| 812 |
|
* Saves this deque to a stream (that is, serializes it). |
| 813 |
|
* |
| 814 |
< |
* @serialData The current size (<tt>int</tt>) of the deque, |
| 814 |
> |
* @serialData The current size ({@code int}) of the deque, |
| 815 |
|
* followed by all of its elements (each an object reference) in |
| 816 |
|
* first-to-last order. |
| 817 |
|
*/ |
| 845 |
|
for (int i = 0; i < size; i++) |
| 846 |
|
elements[i] = s.readObject(); |
| 847 |
|
} |
| 848 |
+ |
|
| 849 |
+ |
Spliterator<E> spliterator() { |
| 850 |
+ |
return new DeqSpliterator<E>(this, -1, -1); |
| 851 |
+ |
} |
| 852 |
+ |
|
| 853 |
+ |
public Stream<E> stream() { |
| 854 |
+ |
return Streams.stream(spliterator()); |
| 855 |
+ |
} |
| 856 |
+ |
|
| 857 |
+ |
public Stream<E> parallelStream() { |
| 858 |
+ |
return Streams.parallelStream(spliterator()); |
| 859 |
+ |
} |
| 860 |
+ |
|
| 861 |
+ |
static final class DeqSpliterator<E> implements Spliterator<E> { |
| 862 |
+ |
private final ArrayDeque<E> deq; |
| 863 |
+ |
private int fence; // -1 until first use |
| 864 |
+ |
private int index; // current index, modified on traverse/split |
| 865 |
+ |
|
| 866 |
+ |
/** Creates new spliterator covering the given array and range */ |
| 867 |
+ |
DeqSpliterator(ArrayDeque<E> deq, int origin, int fence) { |
| 868 |
+ |
this.deq = deq; |
| 869 |
+ |
this.index = origin; |
| 870 |
+ |
this.fence = fence; |
| 871 |
+ |
} |
| 872 |
+ |
|
| 873 |
+ |
private int getFence() { // force initialization |
| 874 |
+ |
int t; |
| 875 |
+ |
if ((t = fence) < 0) { |
| 876 |
+ |
t = fence = deq.tail; |
| 877 |
+ |
index = deq.head; |
| 878 |
+ |
} |
| 879 |
+ |
return t; |
| 880 |
+ |
} |
| 881 |
+ |
|
| 882 |
+ |
public DeqSpliterator<E> trySplit() { |
| 883 |
+ |
int t = getFence(), h = index, n = deq.elements.length; |
| 884 |
+ |
if (h != t && ((h + 1) & (n - 1)) != t) { |
| 885 |
+ |
if (h > t) |
| 886 |
+ |
t += n; |
| 887 |
+ |
int m = ((h + t) >>> 1) & (n - 1); |
| 888 |
+ |
return new DeqSpliterator<>(deq, h, index = m); |
| 889 |
+ |
} |
| 890 |
+ |
return null; |
| 891 |
+ |
} |
| 892 |
+ |
|
| 893 |
+ |
public void forEach(Consumer<? super E> consumer) { |
| 894 |
+ |
if (consumer == null) |
| 895 |
+ |
throw new NullPointerException(); |
| 896 |
+ |
Object[] a = deq.elements; |
| 897 |
+ |
int m = a.length - 1, f = getFence(), i = index; |
| 898 |
+ |
index = f; |
| 899 |
+ |
while (i != f) { |
| 900 |
+ |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
| 901 |
+ |
i = (i + 1) & m; |
| 902 |
+ |
if (e == null) |
| 903 |
+ |
throw new ConcurrentModificationException(); |
| 904 |
+ |
consumer.accept(e); |
| 905 |
+ |
} |
| 906 |
+ |
} |
| 907 |
+ |
|
| 908 |
+ |
public boolean tryAdvance(Consumer<? super E> consumer) { |
| 909 |
+ |
if (consumer == null) |
| 910 |
+ |
throw new NullPointerException(); |
| 911 |
+ |
Object[] a = deq.elements; |
| 912 |
+ |
int m = a.length - 1, f = getFence(), i = index; |
| 913 |
+ |
if (i != fence) { |
| 914 |
+ |
@SuppressWarnings("unchecked") E e = (E)a[i]; |
| 915 |
+ |
index = (i + 1) & m; |
| 916 |
+ |
if (e == null) |
| 917 |
+ |
throw new ConcurrentModificationException(); |
| 918 |
+ |
consumer.accept(e); |
| 919 |
+ |
return true; |
| 920 |
+ |
} |
| 921 |
+ |
return false; |
| 922 |
+ |
} |
| 923 |
+ |
|
| 924 |
+ |
public long estimateSize() { |
| 925 |
+ |
int n = getFence() - index; |
| 926 |
+ |
if (n < 0) |
| 927 |
+ |
n += deq.elements.length; |
| 928 |
+ |
return (long) n; |
| 929 |
+ |
} |
| 930 |
+ |
|
| 931 |
+ |
@Override |
| 932 |
+ |
public int characteristics() { |
| 933 |
+ |
return Spliterator.ORDERED | Spliterator.SIZED | |
| 934 |
+ |
Spliterator.NONNULL | Spliterator.SUBSIZED; |
| 935 |
+ |
} |
| 936 |
+ |
} |
| 937 |
+ |
|
| 938 |
|
} |
