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	/*
	* Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.util;

	import java.util.function.Consumer;

	/**
	* This class provides a skeletal implementation of the {@link List}
	* interface to minimize the effort required to implement this interface
	* backed by a "random access" data store (such as an array). For sequential
	* access data (such as a linked list), {@link AbstractSequentialList} should
	* be used in preference to this class.
	*
	* <p>To implement an unmodifiable list, the programmer needs only to extend
	* this class and provide implementations for the {@link #get(int)} and
	* {@link List#size() size()} methods.
	*
	* <p>To implement a modifiable list, the programmer must additionally
	* override the {@link #set(int, Object) set(int, E)} method (which otherwise
	* throws an {@code UnsupportedOperationException}). If the list is
	* variable-size the programmer must additionally override the
	* {@link #add(int, Object) add(int, E)} and {@link #remove(int)} methods.
	*
	* <p>The programmer should generally provide a void (no argument) and collection
	* constructor, as per the recommendation in the {@link Collection} interface
	* specification.
	*
	* <p>Unlike the other abstract collection implementations, the programmer does
	* <i>not</i> have to provide an iterator implementation; the iterator and
	* list iterator are implemented by this class, on top of the "random access"
	* methods:
	* {@link #get(int)},
	* {@link #set(int, Object) set(int, E)},
	* {@link #add(int, Object) add(int, E)} and
	* {@link #remove(int)}.
	*
	* <p>The documentation for each non-abstract method in this class describes its
	* implementation in detail. Each of these methods may be overridden if the
	* collection being implemented admits a more efficient implementation.
	*
	* <p>This class is a member of the
	* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
	* Java Collections Framework</a>.
	*
	* @author Josh Bloch
	* @author Neal Gafter
	* @since 1.2
	*/

	public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E> {
	/**
	* Sole constructor. (For invocation by subclass constructors, typically
	* implicit.)
	*/
	protected AbstractList() {
	}

	/**
	* Appends the specified element to the end of this list (optional
	* operation).
	*
	* <p>Lists that support this operation may place limitations on what
	* elements may be added to this list. In particular, some
	* lists will refuse to add null elements, and others will impose
	* restrictions on the type of elements that may be added. List
	* classes should clearly specify in their documentation any restrictions
	* on what elements may be added.
	*
	* @implSpec
	* This implementation calls {@code add(size(), e)}.
	*
	* <p>Note that this implementation throws an
	* {@code UnsupportedOperationException} unless
	* {@link #add(int, Object) add(int, E)} is overridden.
	*
	* @param e element to be appended to this list
	* @return {@code true} (as specified by {@link Collection#add})
	* @throws UnsupportedOperationException if the {@code add} operation
	* is not supported by this list
	* @throws ClassCastException if the class of the specified element
	* prevents it from being added to this list
	* @throws NullPointerException if the specified element is null and this
	* list does not permit null elements
	* @throws IllegalArgumentException if some property of this element
	* prevents it from being added to this list
	*/
	public boolean add(E e) {
	add(size(), e);
	return true;
	}

	/**
	* {@inheritDoc}
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public abstract E get(int index);

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation always throws an
	* {@code UnsupportedOperationException}.
	*
	* @throws UnsupportedOperationException {@inheritDoc}
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	* @throws IllegalArgumentException {@inheritDoc}
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public E set(int index, E element) {
	throw new UnsupportedOperationException();
	}

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation always throws an
	* {@code UnsupportedOperationException}.
	*
	* @throws UnsupportedOperationException {@inheritDoc}
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	* @throws IllegalArgumentException {@inheritDoc}
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public void add(int index, E element) {
	throw new UnsupportedOperationException();
	}

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation always throws an
	* {@code UnsupportedOperationException}.
	*
	* @throws UnsupportedOperationException {@inheritDoc}
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public E remove(int index) {
	throw new UnsupportedOperationException();
	}


	// Search Operations

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation first gets a list iterator (with
	* {@code listIterator()}). Then, it iterates over the list until the
	* specified element is found or the end of the list is reached.
	*
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	*/
	public int indexOf(Object o) {
	ListIterator<E> it = listIterator();
	if (o==null) {
	while (it.hasNext())
	if (it.next()==null)
	return it.previousIndex();
	} else {
	while (it.hasNext())
	if (o.equals(it.next()))
	return it.previousIndex();
	}
	return -1;
	}

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation first gets a list iterator that points to the end
	* of the list (with {@code listIterator(size())}). Then, it iterates
	* backwards over the list until the specified element is found, or the
	* beginning of the list is reached.
	*
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	*/
	public int lastIndexOf(Object o) {
	ListIterator<E> it = listIterator(size());
	if (o==null) {
	while (it.hasPrevious())
	if (it.previous()==null)
	return it.nextIndex();
	} else {
	while (it.hasPrevious())
	if (o.equals(it.previous()))
	return it.nextIndex();
	}
	return -1;
	}


	// Bulk Operations

	/**
	* Removes all of the elements from this list (optional operation).
	* The list will be empty after this call returns.
	*
	* @implSpec
	* This implementation calls {@code removeRange(0, size())}.
	*
	* <p>Note that this implementation throws an
	* {@code UnsupportedOperationException} unless {@code remove(int
	* index)} or {@code removeRange(int fromIndex, int toIndex)} is
	* overridden.
	*
	* @throws UnsupportedOperationException if the {@code clear} operation
	* is not supported by this list
	*/
	public void clear() {
	removeRange(0, size());
	}

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation gets an iterator over the specified collection
	* and iterates over it, inserting the elements obtained from the
	* iterator into this list at the appropriate position, one at a time,
	* using {@code add(int, E)}.
	* Many implementations will override this method for efficiency.
	*
	* <p>Note that this implementation throws an
	* {@code UnsupportedOperationException} unless
	* {@link #add(int, Object) add(int, E)} is overridden.
	*
	* @throws UnsupportedOperationException {@inheritDoc}
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	* @throws IllegalArgumentException {@inheritDoc}
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public boolean addAll(int index, Collection<? extends E> c) {
	rangeCheckForAdd(index);
	boolean modified = false;
	for (E e : c) {
	add(index++, e);
	modified = true;
	}
	return modified;
	}


	// Iterators

	/**
	* Returns an iterator over the elements in this list in proper sequence.
	*
	* @implSpec
	* This implementation returns a straightforward implementation of the
	* iterator interface, relying on the backing list's {@code size()},
	* {@code get(int)}, and {@code remove(int)} methods.
	*
	* <p>Note that the iterator returned by this method will throw an
	* {@link UnsupportedOperationException} in response to its
	* {@code remove} method unless the list's {@code remove(int)} method is
	* overridden.
	*
	* <p>This implementation can be made to throw runtime exceptions in the
	* face of concurrent modification, as described in the specification
	* for the (protected) {@link #modCount} field.
	*
	* @return an iterator over the elements in this list in proper sequence
	*/
	public Iterator<E> iterator() {
	return new Itr();
	}

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation returns {@code listIterator(0)}.
	*
	* @see #listIterator(int)
	*/
	public ListIterator<E> listIterator() {
	return listIterator(0);
	}

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation returns a straightforward implementation of the
	* {@code ListIterator} interface that extends the implementation of the
	* {@code Iterator} interface returned by the {@code iterator()} method.
	* The {@code ListIterator} implementation relies on the backing list's
	* {@code get(int)}, {@code set(int, E)}, {@code add(int, E)}
	* and {@code remove(int)} methods.
	*
	* <p>Note that the list iterator returned by this implementation will
	* throw an {@link UnsupportedOperationException} in response to its
	* {@code remove}, {@code set} and {@code add} methods unless the
	* list's {@code remove(int)}, {@code set(int, E)}, and
	* {@code add(int, E)} methods are overridden.
	*
	* <p>This implementation can be made to throw runtime exceptions in the
	* face of concurrent modification, as described in the specification for
	* the (protected) {@link #modCount} field.
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public ListIterator<E> listIterator(final int index) {
	rangeCheckForAdd(index);

	return new ListItr(index);
	}

	private class Itr implements Iterator<E> {
	/**
	* Index of element to be returned by subsequent call to next.
	*/
	int cursor = 0;

	/**
	* Index of element returned by most recent call to next or
	* previous. Reset to -1 if this element is deleted by a call
	* to remove.
	*/
	int lastRet = -1;

	/**
	* The modCount value that the iterator believes that the backing
	* List should have. If this expectation is violated, the iterator
	* has detected concurrent modification.
	*/
	int expectedModCount = modCount;

	public boolean hasNext() {
	return cursor != size();
	}

	public E next() {
	checkForComodification();
	try {
	int i = cursor;
	E next = get(i);
	lastRet = i;
	cursor = i + 1;
	return next;
	} catch (IndexOutOfBoundsException e) {
	checkForComodification();
	throw new NoSuchElementException();
	}
	}

	public void remove() {
	if (lastRet < 0)
	throw new IllegalStateException();
	checkForComodification();

	try {
	AbstractList.this.remove(lastRet);
	if (lastRet < cursor)
	cursor--;
	lastRet = -1;
	expectedModCount = modCount;
	} catch (IndexOutOfBoundsException e) {
	throw new ConcurrentModificationException();
	}
	}

	final void checkForComodification() {
	if (modCount != expectedModCount)
	throw new ConcurrentModificationException();
	}
	}

	private class ListItr extends Itr implements ListIterator<E> {
	ListItr(int index) {
	cursor = index;
	}

	public boolean hasPrevious() {
	return cursor != 0;
	}

	public E previous() {
	checkForComodification();
	try {
	int i = cursor - 1;
	E previous = get(i);
	lastRet = cursor = i;
	return previous;
	} catch (IndexOutOfBoundsException e) {
	checkForComodification();
	throw new NoSuchElementException();
	}
	}

	public int nextIndex() {
	return cursor;
	}

	public int previousIndex() {
	return cursor-1;
	}

	public void set(E e) {
	if (lastRet < 0)
	throw new IllegalStateException();
	checkForComodification();

	try {
	AbstractList.this.set(lastRet, e);
	expectedModCount = modCount;
	} catch (IndexOutOfBoundsException ex) {
	throw new ConcurrentModificationException();
	}
	}

	public void add(E e) {
	checkForComodification();

	try {
	int i = cursor;
	AbstractList.this.add(i, e);
	lastRet = -1;
	cursor = i + 1;
	expectedModCount = modCount;
	} catch (IndexOutOfBoundsException ex) {
	throw new ConcurrentModificationException();
	}
	}
	}

	/**
	* {@inheritDoc}
	*
	* @implSpec
	* This implementation returns a list that subclasses
	* {@code AbstractList}. The subclass stores, in private fields, the
	* size of the subList (which can change over its lifetime), and the
	* expected {@code modCount} value of the backing list. There are two
	* variants of the subclass, one of which implements {@code RandomAccess}.
	* If this list implements {@code RandomAccess} the returned list will
	* be an instance of the subclass that implements {@code RandomAccess}.
	*
	* <p>The subclass's {@code set(int, E)}, {@code get(int)},
	* {@code add(int, E)}, {@code remove(int)}, {@code addAll(int,
	* Collection)} and {@code removeRange(int, int)} methods all
	* delegate to the corresponding methods on the backing abstract list,
	* after bounds-checking the index and adjusting for the offset. The
	* {@code addAll(Collection c)} method merely returns {@code addAll(size,
	* c)}.
	*
	* <p>The {@code listIterator(int)} method returns a "wrapper object"
	* over a list iterator on the backing list, which is created with the
	* corresponding method on the backing list. The {@code iterator} method
	* merely returns {@code listIterator()}, and the {@code size} method
	* merely returns the subclass's {@code size} field.
	*
	* <p>All methods first check to see if the actual {@code modCount} of
	* the backing list is equal to its expected value, and throw a
	* {@code ConcurrentModificationException} if it is not.
	*
	* @throws IndexOutOfBoundsException if an endpoint index value is out of range
	* {@code (fromIndex < 0 \|\| toIndex > size)}
	* @throws IllegalArgumentException if the endpoint indices are out of order
	* {@code (fromIndex > toIndex)}
	*/
	public List<E> subList(int fromIndex, int toIndex) {
	subListRangeCheck(fromIndex, toIndex, size());
	return (this instanceof RandomAccess ?
	new RandomAccessSubList<>(this, fromIndex, toIndex) :
	new SubList<>(this, fromIndex, toIndex));
	}

	static void subListRangeCheck(int fromIndex, int toIndex, int size) {
	if (fromIndex < 0)
	throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
	if (toIndex > size)
	throw new IndexOutOfBoundsException("toIndex = " + toIndex);
	if (fromIndex > toIndex)
	throw new IllegalArgumentException("fromIndex(" + fromIndex +
	") > toIndex(" + toIndex + ")");
	}

	// Comparison and hashing

	/**
	* Compares the specified object with this list for equality. Returns
	* {@code true} if and only if the specified object is also a list, both
	* lists have the same size, and all corresponding pairs of elements in
	* the two lists are <i>equal</i>. (Two elements {@code e1} and
	* {@code e2} are <i>equal</i> if {@code (e1==null ? e2==null :
	* e1.equals(e2))}.) In other words, two lists are defined to be
	* equal if they contain the same elements in the same order.
	*
	* @implSpec
	* This implementation first checks if the specified object is this
	* list. If so, it returns {@code true}; if not, it checks if the
	* specified object is a list. If not, it returns {@code false}; if so,
	* it iterates over both lists, comparing corresponding pairs of elements.
	* If any comparison returns {@code false}, this method returns
	* {@code false}. If either iterator runs out of elements before the
	* other it returns {@code false} (as the lists are of unequal length);
	* otherwise it returns {@code true} when the iterations complete.
	*
	* @param o the object to be compared for equality with this list
	* @return {@code true} if the specified object is equal to this list
	*/
	public boolean equals(Object o) {
	if (o == this)
	return true;
	if (!(o instanceof List))
	return false;

	ListIterator<E> e1 = listIterator();
	ListIterator<?> e2 = ((List<?>) o).listIterator();
	while (e1.hasNext() && e2.hasNext()) {
	E o1 = e1.next();
	Object o2 = e2.next();
	if (!(o1==null ? o2==null : o1.equals(o2)))
	return false;
	}
	return !(e1.hasNext() \|\| e2.hasNext());
	}

	/**
	* Returns the hash code value for this list.
	*
	* @implSpec
	* This implementation uses exactly the code that is used to define the
	* list hash function in the documentation for the {@link List#hashCode}
	* method.
	*
	* @return the hash code value for this list
	*/
	public int hashCode() {
	int hashCode = 1;
	for (E e : this)
	hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
	return hashCode;
	}

	/**
	* Removes from this list all of the elements whose index is between
	* {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
	* Shifts any succeeding elements to the left (reduces their index).
	* This call shortens the list by {@code (toIndex - fromIndex)} elements.
	* (If {@code toIndex==fromIndex}, this operation has no effect.)
	*
	* <p>This method is called by the {@code clear} operation on this list
	* and its subLists. Overriding this method to take advantage of
	* the internals of the list implementation can <i>substantially</i>
	* improve the performance of the {@code clear} operation on this list
	* and its subLists.
	*
	* @implSpec
	* This implementation gets a list iterator positioned before
	* {@code fromIndex}, and repeatedly calls {@code ListIterator.next}
	* followed by {@code ListIterator.remove} until the entire range has
	* been removed. <b>Note: if {@code ListIterator.remove} requires linear
	* time, this implementation requires quadratic time.</b>
	*
	* @param fromIndex index of first element to be removed
	* @param toIndex index after last element to be removed
	*/
	protected void removeRange(int fromIndex, int toIndex) {
	ListIterator<E> it = listIterator(fromIndex);
	for (int i=0, n=toIndex-fromIndex; i<n; i++) {
	it.next();
	it.remove();
	}
	}

	/**
	* The number of times this list has been <i>structurally modified</i>.
	* Structural modifications are those that change the size of the
	* list, or otherwise perturb it in such a fashion that iterations in
	* progress may yield incorrect results.
	*
	* <p>This field is used by the iterator and list iterator implementation
	* returned by the {@code iterator} and {@code listIterator} methods.
	* If the value of this field changes unexpectedly, the iterator (or list
	* iterator) will throw a {@code ConcurrentModificationException} in
	* response to the {@code next}, {@code remove}, {@code previous},
	* {@code set} or {@code add} operations. This provides
	* <i>fail-fast</i> behavior, rather than non-deterministic behavior in
	* the face of concurrent modification during iteration.
	*
	* <p><b>Use of this field by subclasses is optional.</b> If a subclass
	* wishes to provide fail-fast iterators (and list iterators), then it
	* merely has to increment this field in its {@code add(int, E)} and
	* {@code remove(int)} methods (and any other methods that it overrides
	* that result in structural modifications to the list). A single call to
	* {@code add(int, E)} or {@code remove(int)} must add no more than
	* one to this field, or the iterators (and list iterators) will throw
	* bogus {@code ConcurrentModificationExceptions}. If an implementation
	* does not wish to provide fail-fast iterators, this field may be
	* ignored.
	*/
	protected transient int modCount = 0;

	private void rangeCheckForAdd(int index) {
	if (index < 0 \|\| index > size())
	throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
	}

	private String outOfBoundsMsg(int index) {
	return "Index: "+index+", Size: "+size();
	}

	/**
	* An index-based split-by-two, lazily initialized Spliterator covering
	* a List that access elements via {@link List#get}.
	*
	* If access results in an IndexOutOfBoundsException then a
	* ConcurrentModificationException is thrown instead (since the list has
	* been structurally modified while traversing).
	*
	* If the List is an instance of AbstractList then concurrent modification
	* checking is performed using the AbstractList's modCount field.
	*/
	static final class RandomAccessSpliterator<E> implements Spliterator<E> {

	private final List<E> list;
	private int index; // current index, modified on advance/split
	private int fence; // -1 until used; then one past last index

	// The following fields are valid if covering an AbstractList
	private final AbstractList<E> alist;
	private int expectedModCount; // initialized when fence set

	RandomAccessSpliterator(List<E> list) {
	assert list instanceof RandomAccess;

	this.list = list;
	this.index = 0;
	this.fence = -1;

	this.alist = list instanceof AbstractList ? (AbstractList<E>) list : null;
	this.expectedModCount = alist != null ? alist.modCount : 0;
	}

	/** Create new spliterator covering the given range */
	private RandomAccessSpliterator(RandomAccessSpliterator<E> parent,
	int origin, int fence) {
	this.list = parent.list;
	this.index = origin;
	this.fence = fence;

	this.alist = parent.alist;
	this.expectedModCount = parent.expectedModCount;
	}

	private int getFence() { // initialize fence to size on first use
	int hi;
	List<E> lst = list;
	if ((hi = fence) < 0) {
	if (alist != null) {
	expectedModCount = alist.modCount;
	}
	hi = fence = lst.size();
	}
	return hi;
	}

	public Spliterator<E> trySplit() {
	int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
	return (lo >= mid) ? null : // divide range in half unless too small
	new RandomAccessSpliterator<>(this, lo, index = mid);
	}

	public boolean tryAdvance(Consumer<? super E> action) {
	if (action == null)
	throw new NullPointerException();
	int hi = getFence(), i = index;
	if (i < hi) {
	index = i + 1;
	action.accept(get(list, i));
	checkAbstractListModCount(alist, expectedModCount);
	return true;
	}
	return false;
	}

	public void forEachRemaining(Consumer<? super E> action) {
	Objects.requireNonNull(action);
	List<E> lst = list;
	int hi = getFence();
	int i = index;
	index = hi;
	for (; i < hi; i++) {
	action.accept(get(lst, i));
	}
	checkAbstractListModCount(alist, expectedModCount);
	}

	public long estimateSize() {
	return (long) (getFence() - index);
	}

	public int characteristics() {
	return Spliterator.ORDERED \| Spliterator.SIZED \| Spliterator.SUBSIZED;
	}

	private static <E> E get(List<E> list, int i) {
	try {
	return list.get(i);
	} catch (IndexOutOfBoundsException ex) {
	throw new ConcurrentModificationException();
	}
	}

	static void checkAbstractListModCount(AbstractList<?> alist, int expectedModCount) {
	if (alist != null && alist.modCount != expectedModCount) {
	throw new ConcurrentModificationException();
	}
	}
	}

	private static class SubList<E> extends AbstractList<E> {
	private final AbstractList<E> root;
	private final SubList<E> parent;
	private final int offset;
	protected int size;

	/**
	* Constructs a sublist of an arbitrary AbstractList, which is
	* not a SubList itself.
	*/
	public SubList(AbstractList<E> root, int fromIndex, int toIndex) {
	this.root = root;
	this.parent = null;
	this.offset = fromIndex;
	this.size = toIndex - fromIndex;
	this.modCount = root.modCount;
	}

	/**
	* Constructs a sublist of another SubList.
	*/
	protected SubList(SubList<E> parent, int fromIndex, int toIndex) {
	this.root = parent.root;
	this.parent = parent;
	this.offset = parent.offset + fromIndex;
	this.size = toIndex - fromIndex;
	this.modCount = root.modCount;
	}

	public E set(int index, E element) {
	Objects.checkIndex(index, size);
	checkForComodification();
	return root.set(offset + index, element);
	}

	public E get(int index) {
	Objects.checkIndex(index, size);
	checkForComodification();
	return root.get(offset + index);
	}

	public int size() {
	checkForComodification();
	return size;
	}

	public void add(int index, E element) {
	rangeCheckForAdd(index);
	checkForComodification();
	root.add(offset + index, element);
	updateSizeAndModCount(1);
	}

	public E remove(int index) {
	Objects.checkIndex(index, size);
	checkForComodification();
	E result = root.remove(offset + index);
	updateSizeAndModCount(-1);
	return result;
	}

	protected void removeRange(int fromIndex, int toIndex) {
	checkForComodification();
	root.removeRange(offset + fromIndex, offset + toIndex);
	updateSizeAndModCount(fromIndex - toIndex);
	}

	public boolean addAll(Collection<? extends E> c) {
	return addAll(size, c);
	}

	public boolean addAll(int index, Collection<? extends E> c) {
	rangeCheckForAdd(index);
	int cSize = c.size();
	if (cSize==0)
	return false;
	checkForComodification();
	root.addAll(offset + index, c);
	updateSizeAndModCount(cSize);
	return true;
	}

	public Iterator<E> iterator() {
	return listIterator();
	}

	public ListIterator<E> listIterator(int index) {
	checkForComodification();
	rangeCheckForAdd(index);

	return new ListIterator<E>() {
	private final ListIterator<E> i =
	root.listIterator(offset + index);

	public boolean hasNext() {
	return nextIndex() < size;
	}

	public E next() {
	if (hasNext())
	return i.next();
	else
	throw new NoSuchElementException();
	}

	public boolean hasPrevious() {
	return previousIndex() >= 0;
	}

	public E previous() {
	if (hasPrevious())
	return i.previous();
	else
	throw new NoSuchElementException();
	}

	public int nextIndex() {
	return i.nextIndex() - offset;
	}

	public int previousIndex() {
	return i.previousIndex() - offset;
	}

	public void remove() {
	i.remove();
	updateSizeAndModCount(-1);
	}

	public void set(E e) {
	i.set(e);
	}

	public void add(E e) {
	i.add(e);
	updateSizeAndModCount(1);
	}
	};
	}

	public List<E> subList(int fromIndex, int toIndex) {
	subListRangeCheck(fromIndex, toIndex, size);
	return new SubList<>(this, fromIndex, toIndex);
	}

	private void rangeCheckForAdd(int index) {
	if (index < 0 \|\| index > size)
	throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
	}

	private String outOfBoundsMsg(int index) {
	return "Index: "+index+", Size: "+size;
	}

	private void checkForComodification() {
	if (root.modCount != this.modCount)
	throw new ConcurrentModificationException();
	}

	private void updateSizeAndModCount(int sizeChange) {
	SubList<E> slist = this;
	do {
	slist.size += sizeChange;
	slist.modCount = root.modCount;
	slist = slist.parent;
	} while (slist != null);
	}
	}

	private static class RandomAccessSubList<E>
	extends SubList<E> implements RandomAccess {

	/**
	* Constructs a sublist of an arbitrary AbstractList, which is
	* not a RandomAccessSubList itself.
	*/
	RandomAccessSubList(AbstractList<E> root,
	int fromIndex, int toIndex) {
	super(root, fromIndex, toIndex);
	}

	/**
	* Constructs a sublist of another RandomAccessSubList.
	*/
	RandomAccessSubList(RandomAccessSubList<E> parent,
	int fromIndex, int toIndex) {
	super(parent, fromIndex, toIndex);
	}

	public List<E> subList(int fromIndex, int toIndex) {
	subListRangeCheck(fromIndex, toIndex, size);
	return new RandomAccessSubList<>(this, fromIndex, toIndex);
	}
	}
	}

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