/*

* Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.

* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

*

*

*

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*

*

*

*

*

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*

*/

package java.util;

import java.util.function.Consumer;

import sun.misc.SharedSecrets;

/**

* An unbounded priority {@linkplain Queue queue} based on a priority heap.

* The elements of the priority queue are ordered according to their

* {@linkplain Comparable natural ordering}, or by a {@link Comparator}

* provided at queue construction time, depending on which constructor is

* used. A priority queue does not permit {@code null} elements.

* A priority queue relying on natural ordering also does not permit

* insertion of non-comparable objects (doing so may result in

* {@code ClassCastException}).

*

* <p>The <em>head</em> of this queue is the <em>least</em> element

* with respect to the specified ordering. If multiple elements are

* tied for least value, the head is one of those elements -- ties are

* broken arbitrarily. The queue retrieval operations {@code poll},

* {@code remove}, {@code peek}, and {@code element} access the

* element at the head of the queue.

*

* <p>A priority queue is unbounded, but has an internal

* <i>capacity</i> governing the size of an array used to store the

* elements on the queue. It is always at least as large as the queue

* size. As elements are added to a priority queue, its capacity

* grows automatically. The details of the growth policy are not

* specified.

*

* <p>This class and its iterator implement all of the

* <em>optional</em> methods of the {@link Collection} and {@link

* Iterator} interfaces. The Iterator provided in method {@link

* #iterator()} is <em>not</em> guaranteed to traverse the elements of

* the priority queue in any particular order. If you need ordered

* traversal, consider using {@code Arrays.sort(pq.toArray())}.

*

* <p><strong>Note that this implementation is not synchronized.</strong>

* Multiple threads should not access a {@code PriorityQueue}

* instance concurrently if any of the threads modifies the queue.

* Instead, use the thread-safe {@link

* java.util.concurrent.PriorityBlockingQueue} class.

*

* <p>Implementation note: this implementation provides

* O(log(n)) time for the enqueuing and dequeuing methods

* ({@code offer}, {@code poll}, {@code remove()} and {@code add});

* linear time for the {@code remove(Object)} and {@code contains(Object)}

* methods; and constant time for the retrieval methods

* ({@code peek}, {@code element}, and {@code size}).

*

* <p>This class is a member of the

* <a href="{@docRoot}/../technotes/guides/collections/index.html">

* Java Collections Framework</a>.

*

* @since 1.5

* @author Josh Bloch, Doug Lea

* @param <E> the type of elements held in this collection

*/

public class PriorityQueue<E> extends AbstractQueue<E>

implements java.io.Serializable {

private static final long serialVersionUID = -7720805057305804111L;

private static final int DEFAULT_INITIAL_CAPACITY = 11;

/**

* Priority queue represented as a balanced binary heap: the two

* children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The

* priority queue is ordered by comparator, or by the elements'

* natural ordering, if comparator is null: For each node n in the

* heap and each descendant d of n, n <= d. The element with the

* lowest value is in queue[0], assuming the queue is nonempty.

*/

transient Object[] queue; // non-private to simplify nested class access

/**

* The number of elements in the priority queue.

*/

private int size = 0;

/**

* The comparator, or null if priority queue uses elements'

* natural ordering.

*/

private final Comparator<? super E> comparator;

/**

* The number of times this priority queue has been

* <i>structurally modified</i>. See AbstractList for gory details.

*/

transient int modCount = 0; // non-private to simplify nested class access

/**

* Creates a {@code PriorityQueue} with the default initial

* capacity (11) that orders its elements according to their

* {@linkplain Comparable natural ordering}.

*/

public PriorityQueue() {

this(DEFAULT_INITIAL_CAPACITY, null);

}

/**

* Creates a {@code PriorityQueue} with the specified initial

* capacity that orders its elements according to their

* {@linkplain Comparable natural ordering}.

*

* @param initialCapacity the initial capacity for this priority queue

* @throws IllegalArgumentException if {@code initialCapacity} is less

* than 1

*/

public PriorityQueue(int initialCapacity) {

this(initialCapacity, null);

}

/**

* Creates a {@code PriorityQueue} with the default initial capacity and

* whose elements are ordered according to the specified comparator.

*

* @param comparator the comparator that will be used to order this

* priority queue. If {@code null}, the {@linkplain Comparable

* natural ordering} of the elements will be used.

* @since 1.8

*/

public PriorityQueue(Comparator<? super E> comparator) {

this(DEFAULT_INITIAL_CAPACITY, comparator);

}

/**

* Creates a {@code PriorityQueue} with the specified initial capacity

* that orders its elements according to the specified comparator.

*

* @param initialCapacity the initial capacity for this priority queue

* @param comparator the comparator that will be used to order this

* priority queue. If {@code null}, the {@linkplain Comparable

* natural ordering} of the elements will be used.

* @throws IllegalArgumentException if {@code initialCapacity} is

* less than 1

*/

public PriorityQueue(int initialCapacity,

Comparator<? super E> comparator) {

// Note: This restriction of at least one is not actually needed,

// but continues for 1.5 compatibility

if (initialCapacity < 1)

throw new IllegalArgumentException();

this.queue = new Object[initialCapacity];

this.comparator = comparator;

}

/**

* Creates a {@code PriorityQueue} containing the elements in the

* specified collection. If the specified collection is an instance of

* a {@link SortedSet} or is another {@code PriorityQueue}, this

* priority queue will be ordered according to the same ordering.

* Otherwise, this priority queue will be ordered according to the

* {@linkplain Comparable natural ordering} of its elements.

*

* @param c the collection whose elements are to be placed

* into this priority queue

* @throws ClassCastException if elements of the specified collection

* cannot be compared to one another according to the priority

* queue's ordering

* @throws NullPointerException if the specified collection or any

* of its elements are null

*/

@SuppressWarnings("unchecked")

public PriorityQueue(Collection<? extends E> c) {

if (c instanceof SortedSet<?>) {

SortedSet<? extends E> ss = (SortedSet<? extends E>) c;

this.comparator = (Comparator<? super E>) ss.comparator();

initElementsFromCollection(ss);

}

else if (c instanceof PriorityQueue<?>) {

PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;

this.comparator = (Comparator<? super E>) pq.comparator();

initFromPriorityQueue(pq);

}

else {

this.comparator = null;

initFromCollection(c);

}

}

/**

* Creates a {@code PriorityQueue} containing the elements in the

* specified priority queue. This priority queue will be

* ordered according to the same ordering as the given priority

* queue.

*

* @param c the priority queue whose elements are to be placed

* into this priority queue

* @throws ClassCastException if elements of {@code c} cannot be

* compared to one another according to {@code c}'s

* ordering

* @throws NullPointerException if the specified priority queue or any

* of its elements are null

*/

@SuppressWarnings("unchecked")

public PriorityQueue(PriorityQueue<? extends E> c) {

this.comparator = (Comparator<? super E>) c.comparator();

initFromPriorityQueue(c);

}

/**

* Creates a {@code PriorityQueue} containing the elements in the

* specified sorted set. This priority queue will be ordered

* according to the same ordering as the given sorted set.

*

* @param c the sorted set whose elements are to be placed

* into this priority queue

* @throws ClassCastException if elements of the specified sorted

* set cannot be compared to one another according to the

* sorted set's ordering

* @throws NullPointerException if the specified sorted set or any

* of its elements are null

*/

@SuppressWarnings("unchecked")

public PriorityQueue(SortedSet<? extends E> c) {

this.comparator = (Comparator<? super E>) c.comparator();

initElementsFromCollection(c);

}

private void initFromPriorityQueue(PriorityQueue<? extends E> c) {

if (c.getClass() == PriorityQueue.class) {

this.queue = c.toArray();

this.size = c.size();

} else {

initFromCollection(c);

}

}

private void initElementsFromCollection(Collection<? extends E> c) {

Object[] a = c.toArray();

// If c.toArray incorrectly doesn't return Object[], copy it.

if (a.getClass() != Object[].class)

a = Arrays.copyOf(a, a.length, Object[].class);

int len = a.length;

if (len == 1 || this.comparator != null)

for (int i = 0; i < len; i++)

if (a[i] == null)

throw new NullPointerException();

this.queue = a;

this.size = a.length;

}

/**

* Initializes queue array with elements from the given Collection.

*

* @param c the collection

*/

private void initFromCollection(Collection<? extends E> c) {

initElementsFromCollection(c);

heapify();

}

/**

* The maximum size of array to allocate.

* Some VMs reserve some header words in an array.

* Attempts to allocate larger arrays may result in

* OutOfMemoryError: Requested array size exceeds VM limit

*/

private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

/**

* Increases the capacity of the array.

*

* @param minCapacity the desired minimum capacity

*/

private void grow(int minCapacity) {

int oldCapacity = queue.length;

// Double size if small; else grow by 50%

int newCapacity = oldCapacity + ((oldCapacity < 64) ?

(oldCapacity + 2) :

(oldCapacity >> 1));

// overflow-conscious code

if (newCapacity - MAX_ARRAY_SIZE > 0)

newCapacity = hugeCapacity(minCapacity);

queue = Arrays.copyOf(queue, newCapacity);

}

private static int hugeCapacity(int minCapacity) {

if (minCapacity < 0) // overflow

throw new OutOfMemoryError();

return (minCapacity > MAX_ARRAY_SIZE) ?

Integer.MAX_VALUE :

MAX_ARRAY_SIZE;

}

/**

* Inserts the specified element into this priority queue.

*

* @return {@code true} (as specified by {@link Collection#add})

* @throws ClassCastException if the specified element cannot be

* compared with elements currently in this priority queue

* according to the priority queue's ordering

* @throws NullPointerException if the specified element is null

*/

public boolean add(E e) {

return offer(e);

}

/**

* Inserts the specified element into this priority queue.

*

* @return {@code true} (as specified by {@link Queue#offer})

* @throws ClassCastException if the specified element cannot be

* compared with elements currently in this priority queue

* according to the priority queue's ordering

* @throws NullPointerException if the specified element is null

*/

public boolean offer(E e) {

if (e == null)

throw new NullPointerException();

modCount++;

int i = size;

if (i >= queue.length)

grow(i + 1);

size = i + 1;

if (i == 0)

queue[0] = e;

else

siftUp(i, e);

return true;

}

@SuppressWarnings("unchecked")

public E peek() {

return (size == 0) ? null : (E) queue[0];

}

private int indexOf(Object o) {

if (o != null) {

for (int i = 0; i < size; i++)

if (o.equals(queue[i]))

return i;

}

return -1;

}

/**

* Removes a single instance of the specified element from this queue,

* if it is present. More formally, removes an element {@code e} such

* that {@code o.equals(e)}, if this queue contains one or more such

* elements. Returns {@code true} if and only if this queue contained

* the specified element (or equivalently, if this queue changed as a

* result of the call).

*

* @param o element to be removed from this queue, if present

* @return {@code true} if this queue changed as a result of the call

*/

public boolean remove(Object o) {

int i = indexOf(o);

if (i == -1)

return false;

else {

removeAt(i);

return true;

}

}

/**

* Version of remove using reference equality, not equals.

* Needed by iterator.remove.

*

* @param o element to be removed from this queue, if present

* @return {@code true} if removed

*/

boolean removeEq(Object o) {

for (int i = 0; i < size; i++) {

if (o == queue[i]) {

removeAt(i);

return true;

}

}

return false;

}

/**

* Returns {@code true} if this queue contains the specified element.

* More formally, returns {@code true} if and only if this queue contains

* at least one element {@code e} such that {@code o.equals(e)}.

*

* @param o object to be checked for containment in this queue

* @return {@code true} if this queue contains the specified element

*/

public boolean contains(Object o) {

return indexOf(o) != -1;

}

/**

* Returns an array containing all of the elements in this queue.

* The elements are in no particular order.

*

* <p>The returned array will be "safe" in that no references to it are

* maintained by this queue. (In other words, this method must allocate

* a new array). The caller is thus free to modify the returned array.

*

* <p>This method acts as bridge between array-based and collection-based

* APIs.

*

* @return an array containing all of the elements in this queue

*/

public Object[] toArray() {

return Arrays.copyOf(queue, size);

}

/**

* Returns an array containing all of the elements in this queue; the

* runtime type of the returned array is that of the specified array.

* The returned array elements are in no particular order.

* If the queue fits in the specified array, it is returned therein.

* Otherwise, a new array is allocated with the runtime type of the

* specified array and the size of this queue.

*

* <p>If the queue fits in the specified array with room to spare

* (i.e., the array has more elements than the queue), the element in

* the array immediately following the end of the collection is set to

* {@code null}.

*

* <p>Like the {@link #toArray()} method, this method acts as bridge between

* array-based and collection-based APIs. Further, this method allows

* precise control over the runtime type of the output array, and may,

* under certain circumstances, be used to save allocation costs.

*

* <p>Suppose {@code x} is a queue known to contain only strings.

* The following code can be used to dump the queue into a newly

* allocated array of {@code String}:

*

* <pre> {@code String[] y = x.toArray(new String[0]);}</pre>

*

* Note that {@code toArray(new Object[0])} is identical in function to

* {@code toArray()}.

*

* @param a the array into which the elements of the queue are to

* be stored, if it is big enough; otherwise, a new array of the

* same runtime type is allocated for this purpose.

* @return an array containing all of the elements in this queue

* @throws ArrayStoreException if the runtime type of the specified array

* is not a supertype of the runtime type of every element in

* this queue

* @throws NullPointerException if the specified array is null

*/

@SuppressWarnings("unchecked")

public <T> T[] toArray(T[] a) {

final int size = this.size;

if (a.length < size)

// Make a new array of a's runtime type, but my contents:

return (T[]) Arrays.copyOf(queue, size, a.getClass());

System.arraycopy(queue, 0, a, 0, size);

if (a.length > size)

a[size] = null;

return a;

}

/**

* Returns an iterator over the elements in this queue. The iterator

* does not return the elements in any particular order.

*

* @return an iterator over the elements in this queue

*/

public Iterator<E> iterator() {

return new Itr();

}

private final class Itr implements Iterator<E> {

/**

* Index (into queue array) of element to be returned by

* subsequent call to next.

*/

private int cursor = 0;

/**

* Index of element returned by most recent call to next,

* unless that element came from the forgetMeNot list.

* Set to -1 if element is deleted by a call to remove.

*/

private int lastRet = -1;

/**

* A queue of elements that were moved from the unvisited portion of

* the heap into the visited portion as a result of "unlucky" element

* removals during the iteration. (Unlucky element removals are those

* that require a siftup instead of a siftdown.) We must visit all of

* the elements in this list to complete the iteration. We do this

* after we've completed the "normal" iteration.

*

* We expect that most iterations, even those involving removals,

* will not need to store elements in this field.

*/

private ArrayDeque<E> forgetMeNot = null;

/**

* Element returned by the most recent call to next iff that

* element was drawn from the forgetMeNot list.

*/

private E lastRetElt = null;

/**

* The modCount value that the iterator believes that the backing

* Queue should have. If this expectation is violated, the iterator

* has detected concurrent modification.

*/

private int expectedModCount = modCount;

public boolean hasNext() {

return cursor < size ||

(forgetMeNot != null && !forgetMeNot.isEmpty());

}

@SuppressWarnings("unchecked")

public E next() {

if (expectedModCount != modCount)

throw new ConcurrentModificationException();

if (cursor < size)

return (E) queue[lastRet = cursor++];

if (forgetMeNot != null) {

lastRet = -1;

lastRetElt = forgetMeNot.poll();

if (lastRetElt != null)

return lastRetElt;

}

throw new NoSuchElementException();

}

public void remove() {

if (expectedModCount != modCount)

throw new ConcurrentModificationException();

if (lastRet != -1) {

E moved = PriorityQueue.this.removeAt(lastRet);

lastRet = -1;

if (moved == null)

cursor--;

else {

if (forgetMeNot == null)

forgetMeNot = new ArrayDeque<>();

forgetMeNot.add(moved);

}

} else if (lastRetElt != null) {

PriorityQueue.this.removeEq(lastRetElt);

lastRetElt = null;

} else {

throw new IllegalStateException();

}

expectedModCount = modCount;

}

}

public int size() {

return size;

}

/**

* Removes all of the elements from this priority queue.

* The queue will be empty after this call returns.

*/

public void clear() {

modCount++;

for (int i = 0; i < size; i++)

queue[i] = null;

size = 0;

}

@SuppressWarnings("unchecked")

public E poll() {

if (size == 0)

return null;

int s = --size;

modCount++;

E result = (E) queue[0];

E x = (E) queue[s];

queue[s] = null;

if (s != 0)

siftDown(0, x);

return result;

}

/**

* Removes the ith element from queue.

*

* Normally this method leaves the elements at up to i-1,

* inclusive, untouched. Under these circumstances, it returns

* null. Occasionally, in order to maintain the heap invariant,

* it must swap a later element of the list with one earlier than

* i. Under these circumstances, this method returns the element

* that was previously at the end of the list and is now at some

* position before i. This fact is used by iterator.remove so as to

* avoid missing traversing elements.

*/

@SuppressWarnings("unchecked")

private E removeAt(int i) {

// assert i >= 0 && i < size;

modCount++;

int s = --size;

if (s == i) // removed last element

queue[i] = null;

else {

E moved = (E) queue[s];

queue[s] = null;

siftDown(i, moved);

if (queue[i] == moved) {

siftUp(i, moved);

if (queue[i] != moved)

return moved;

}

}

return null;

}

/**

* Inserts item x at position k, maintaining heap invariant by

* promoting x up the tree until it is greater than or equal to

* its parent, or is the root.

*

* To simplify and speed up coercions and comparisons. the

* Comparable and Comparator versions are separated into different

* methods that are otherwise identical. (Similarly for siftDown.)

*

* @param k the position to fill

* @param x the item to insert

*/

private void siftUp(int k, E x) {

if (comparator != null)

siftUpUsingComparator(k, x);

else

siftUpComparable(k, x);

}

@SuppressWarnings("unchecked")

private void siftUpComparable(int k, E x) {

Comparable<? super E> key = (Comparable<? super E>) x;

while (k > 0) {

int parent = (k - 1) >>> 1;

Object e = queue[parent];

if (key.compareTo((E) e) >= 0)

break;

queue[k] = e;

k = parent;

}

queue[k] = key;

}

@SuppressWarnings("unchecked")

private void siftUpUsingComparator(int k, E x) {

while (k > 0) {

int parent = (k - 1) >>> 1;

Object e = queue[parent];

if (comparator.compare(x, (E) e) >= 0)

break;

queue[k] = e;

k = parent;

}

queue[k] = x;

}

/**

* Inserts item x at position k, maintaining heap invariant by

* demoting x down the tree repeatedly until it is less than or

* equal to its children or is a leaf.

*

* @param k the position to fill

* @param x the item to insert

*/

private void siftDown(int k, E x) {

if (comparator != null)

siftDownUsingComparator(k, x);

else

siftDownComparable(k, x);

}

@SuppressWarnings("unchecked")

private void siftDownComparable(int k, E x) {

Comparable<? super E> key = (Comparable<? super E>)x;

int half = size >>> 1; // loop while a non-leaf

while (k < half) {

int child = (k << 1) + 1; // assume left child is least

Object c = queue[child];

int right = child + 1;

if (right < size &&

((Comparable<? super E>) c).compareTo((E) queue[right]) > 0)

c = queue[child = right];

if (key.compareTo((E) c) <= 0)

break;

queue[k] = c;

k = child;

}

queue[k] = key;

}

@SuppressWarnings("unchecked")

private void siftDownUsingComparator(int k, E x) {

int half = size >>> 1;

while (k < half) {

int child = (k << 1) + 1;

Object c = queue[child];

int right = child + 1;

if (right < size &&

comparator.compare((E) c, (E) queue[right]) > 0)

c = queue[child = right];

if (comparator.compare(x, (E) c) <= 0)

break;

queue[k] = c;

k = child;

}

queue[k] = x;

}

/**

* Establishes the heap invariant (described above) in the entire tree,

* assuming nothing about the order of the elements prior to the call.

*/

@SuppressWarnings("unchecked")

private void heapify() {

for (int i = (size >>> 1) - 1; i >= 0; i--)

siftDown(i, (E) queue[i]);

}

/**

* Returns the comparator used to order the elements in this

* queue, or {@code null} if this queue is sorted according to

* the {@linkplain Comparable natural ordering} of its elements.

*

* @return the comparator used to order this queue, or

* {@code null} if this queue is sorted according to the

* natural ordering of its elements

*/

public Comparator<? super E> comparator() {

return comparator;

}

/**

* Saves this queue to a stream (that is, serializes it).

*

* @serialData The length of the array backing the instance is

* emitted (int), followed by all of its elements

* (each an {@code Object}) in the proper order.

* @param s the stream

*/

private void writeObject(java.io.ObjectOutputStream s)

throws java.io.IOException {

// Write out element count, and any hidden stuff

s.defaultWriteObject();

// Write out array length, for compatibility with 1.5 version

s.writeInt(Math.max(2, size + 1));

// Write out all elements in the "proper order".

for (int i = 0; i < size; i++)

s.writeObject(queue[i]);

}

/**

* Reconstitutes the {@code PriorityQueue} instance from a stream

* (that is, deserializes it).

*

* @param s the stream

*/

private void readObject(java.io.ObjectInputStream s)

throws java.io.IOException, ClassNotFoundException {

// Read in size, and any hidden stuff

s.defaultReadObject();

// Read in (and discard) array length

s.readInt();

SharedSecrets.getJavaOISAccess().checkArray(s, Object[].class, size);

queue = new Object[size];

// Read in all elements.

for (int i = 0; i < size; i++)

queue[i] = s.readObject();

// Elements are guaranteed to be in "proper order", but the

// spec has never explained what that might be.

heapify();

}

/**

* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>

* and <em>fail-fast</em> {@link Spliterator} over the elements in this

* queue.

*

* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},

* {@link Spliterator#SUBSIZED}, and {@link Spliterator#NONNULL}.

* Overriding implementations should document the reporting of additional

* characteristic values.

*

* @return a {@code Spliterator} over the elements in this queue

* @since 1.8

*/

public final Spliterator<E> spliterator() {

return new PriorityQueueSpliterator<E>(this, 0, -1, 0);

}

static final class PriorityQueueSpliterator<E> implements Spliterator<E> {

/*

* This is very similar to ArrayList Spliterator, except for

* extra null checks.

*/

private final PriorityQueue<E> pq;

private int index; // current index, modified on advance/split

private int fence; // -1 until first use

private int expectedModCount; // initialized when fence set

/** Creates new spliterator covering the given range */

PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,

int expectedModCount) {

this.pq = pq;

this.index = origin;

this.fence = fence;

this.expectedModCount = expectedModCount;

}

private int getFence() { // initialize fence to size on first use

int hi;

if ((hi = fence) < 0) {

expectedModCount = pq.modCount;

hi = fence = pq.size;

}

return hi;

}

public PriorityQueueSpliterator<E> trySplit() {

int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;

return (lo >= mid) ? null :

new PriorityQueueSpliterator<E>(pq, lo, index = mid,

expectedModCount);

}

@SuppressWarnings("unchecked")

public void forEachRemaining(Consumer<? super E> action) {

int i, hi, mc; // hoist accesses and checks from loop

PriorityQueue<E> q; Object[] a;

if (action == null)

throw new NullPointerException();

if ((q = pq) != null && (a = q.queue) != null) {

if ((hi = fence) < 0) {

mc = q.modCount;

hi = q.size;

}

else

mc = expectedModCount;

if ((i = index) >= 0 && (index = hi) <= a.length) {

for (E e;; ++i) {

if (i < hi) {

if ((e = (E) a[i]) == null) // must be CME

break;

action.accept(e);

}

else if (q.modCount != mc)

break;

else

return;

}

}

}

throw new ConcurrentModificationException();

}

public boolean tryAdvance(Consumer<? super E> action) {

if (action == null)

throw new NullPointerException();

int hi = getFence(), lo = index;

if (lo >= 0 && lo < hi) {

index = lo + 1;

@SuppressWarnings("unchecked") E e = (E)pq.queue[lo];

if (e == null)

throw new ConcurrentModificationException();

action.accept(e);

if (pq.modCount != expectedModCount)

throw new ConcurrentModificationException();

return true;

}

return false;

}

public long estimateSize() {

return (long) (getFence() - index);

}

public int characteristics() {

return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;

}

}

}