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	/*
	* 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.
	*/

	/*
	* Written by Doug Lea with assistance from members of JCP JSR-166
	* Expert Group. Adapted and released, under explicit permission,
	* from JDK ArrayList.java which carries the following copyright:
	*
	* Copyright 1997 by Sun Microsystems, Inc.,
	* 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
	* All rights reserved.
	*/

	package java.util.concurrent;

	import java.lang.invoke.VarHandle;
	import java.lang.reflect.Field;
	import java.util.Arrays;
	import java.util.Collection;
	import java.util.Comparator;
	import java.util.ConcurrentModificationException;
	import java.util.Iterator;
	import java.util.List;
	import java.util.ListIterator;
	import java.util.NoSuchElementException;
	import java.util.Objects;
	import java.util.RandomAccess;
	import java.util.Spliterator;
	import java.util.Spliterators;
	import java.util.function.Consumer;
	import java.util.function.Predicate;
	import java.util.function.UnaryOperator;
	import jdk.internal.misc.SharedSecrets;

	/**
	* A thread-safe variant of {@link java.util.ArrayList} in which all mutative
	* operations ({@code add}, {@code set}, and so on) are implemented by
	* making a fresh copy of the underlying array.
	*
	* <p>This is ordinarily too costly, but may be <em>more</em> efficient
	* than alternatives when traversal operations vastly outnumber
	* mutations, and is useful when you cannot or don't want to
	* synchronize traversals, yet need to preclude interference among
	* concurrent threads. The "snapshot" style iterator method uses a
	* reference to the state of the array at the point that the iterator
	* was created. This array never changes during the lifetime of the
	* iterator, so interference is impossible and the iterator is
	* guaranteed not to throw {@code ConcurrentModificationException}.
	* The iterator will not reflect additions, removals, or changes to
	* the list since the iterator was created. Element-changing
	* operations on iterators themselves ({@code remove}, {@code set}, and
	* {@code add}) are not supported. These methods throw
	* {@code UnsupportedOperationException}.
	*
	* <p>All elements are permitted, including {@code null}.
	*
	* <p>Memory consistency effects: As with other concurrent
	* collections, actions in a thread prior to placing an object into a
	* {@code CopyOnWriteArrayList}
	* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
	* actions subsequent to the access or removal of that element from
	* the {@code CopyOnWriteArrayList} in another thread.
	*
	* <p>This class is a member of the
	* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
	* Java Collections Framework</a>.
	*
	* @since 1.5
	* @author Doug Lea
	* @param <E> the type of elements held in this list
	*/
	public class CopyOnWriteArrayList<E>
	implements List<E>, RandomAccess, Cloneable, java.io.Serializable {
	private static final long serialVersionUID = 8673264195747942595L;

	/**
	* The lock protecting all mutators. (We have a mild preference
	* for builtin monitors over ReentrantLock when either will do.)
	*/
	final transient Object lock = new Object();

	/** The array, accessed only via getArray/setArray. */
	private transient volatile Object[] array;

	/**
	* Gets the array. Non-private so as to also be accessible
	* from CopyOnWriteArraySet class.
	*/
	final Object[] getArray() {
	return array;
	}

	/**
	* Sets the array.
	*/
	final void setArray(Object[] a) {
	array = a;
	}

	/**
	* Creates an empty list.
	*/
	public CopyOnWriteArrayList() {
	setArray(new Object[0]);
	}

	/**
	* Creates a list containing the elements of the specified
	* collection, in the order they are returned by the collection's
	* iterator.
	*
	* @param c the collection of initially held elements
	* @throws NullPointerException if the specified collection is null
	*/
	public CopyOnWriteArrayList(Collection<? extends E> c) {
	Object[] es;
	if (c.getClass() == CopyOnWriteArrayList.class)
	es = ((CopyOnWriteArrayList<?>)c).getArray();
	else {
	es = c.toArray();
	// defend against c.toArray (incorrectly) not returning Object[]
	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
	if (es.getClass() != Object[].class)
	es = Arrays.copyOf(es, es.length, Object[].class);
	}
	setArray(es);
	}

	/**
	* Creates a list holding a copy of the given array.
	*
	* @param toCopyIn the array (a copy of this array is used as the
	* internal array)
	* @throws NullPointerException if the specified array is null
	*/
	public CopyOnWriteArrayList(E[] toCopyIn) {
	setArray(Arrays.copyOf(toCopyIn, toCopyIn.length, Object[].class));
	}

	/**
	* Returns the number of elements in this list.
	*
	* @return the number of elements in this list
	*/
	public int size() {
	return getArray().length;
	}

	/**
	* Returns {@code true} if this list contains no elements.
	*
	* @return {@code true} if this list contains no elements
	*/
	public boolean isEmpty() {
	return size() == 0;
	}

	/**
	* static version of indexOf, to allow repeated calls without
	* needing to re-acquire array each time.
	* @param o element to search for
	* @param es the array
	* @param from first index to search
	* @param to one past last index to search
	* @return index of element, or -1 if absent
	*/
	private static int indexOfRange(Object o, Object[] es, int from, int to) {
	if (o == null) {
	for (int i = from; i < to; i++)
	if (es[i] == null)
	return i;
	} else {
	for (int i = from; i < to; i++)
	if (o.equals(es[i]))
	return i;
	}
	return -1;
	}

	/**
	* static version of lastIndexOf.
	* @param o element to search for
	* @param es the array
	* @param from index of first element of range, last element to search
	* @param to one past last element of range, first element to search
	* @return index of element, or -1 if absent
	*/
	private static int lastIndexOfRange(Object o, Object[] es, int from, int to) {
	if (o == null) {
	for (int i = to - 1; i >= from; i--)
	if (es[i] == null)
	return i;
	} else {
	for (int i = to - 1; i >= from; i--)
	if (o.equals(es[i]))
	return i;
	}
	return -1;
	}

	/**
	* Returns {@code true} if this list contains the specified element.
	* More formally, returns {@code true} if and only if this list contains
	* at least one element {@code e} such that {@code Objects.equals(o, e)}.
	*
	* @param o element whose presence in this list is to be tested
	* @return {@code true} if this list contains the specified element
	*/
	public boolean contains(Object o) {
	return indexOf(o) >= 0;
	}

	/**
	* {@inheritDoc}
	*/
	public int indexOf(Object o) {
	Object[] es = getArray();
	return indexOfRange(o, es, 0, es.length);
	}

	/**
	* Returns the index of the first occurrence of the specified element in
	* this list, searching forwards from {@code index}, or returns -1 if
	* the element is not found.
	* More formally, returns the lowest index {@code i} such that
	* {@code i >= index && Objects.equals(get(i), e)},
	* or -1 if there is no such index.
	*
	* @param e element to search for
	* @param index index to start searching from
	* @return the index of the first occurrence of the element in
	* this list at position {@code index} or later in the list;
	* {@code -1} if the element is not found.
	* @throws IndexOutOfBoundsException if the specified index is negative
	*/
	public int indexOf(E e, int index) {
	Object[] es = getArray();
	return indexOfRange(e, es, index, es.length);
	}

	/**
	* {@inheritDoc}
	*/
	public int lastIndexOf(Object o) {
	Object[] es = getArray();
	return lastIndexOfRange(o, es, 0, es.length);
	}

	/**
	* Returns the index of the last occurrence of the specified element in
	* this list, searching backwards from {@code index}, or returns -1 if
	* the element is not found.
	* More formally, returns the highest index {@code i} such that
	* {@code i <= index && Objects.equals(get(i), e)},
	* or -1 if there is no such index.
	*
	* @param e element to search for
	* @param index index to start searching backwards from
	* @return the index of the last occurrence of the element at position
	* less than or equal to {@code index} in this list;
	* -1 if the element is not found.
	* @throws IndexOutOfBoundsException if the specified index is greater
	* than or equal to the current size of this list
	*/
	public int lastIndexOf(E e, int index) {
	Object[] es = getArray();
	return lastIndexOfRange(e, es, 0, index + 1);
	}

	/**
	* Returns a shallow copy of this list. (The elements themselves
	* are not copied.)
	*
	* @return a clone of this list
	*/
	public Object clone() {
	try {
	@SuppressWarnings("unchecked")
	CopyOnWriteArrayList<E> clone =
	(CopyOnWriteArrayList<E>) super.clone();
	clone.resetLock();
	// Unlike in readObject, here we cannot visibility-piggyback on the
	// volatile write in setArray().
	VarHandle.releaseFence();
	return clone;
	} catch (CloneNotSupportedException e) {
	// this shouldn't happen, since we are Cloneable
	throw new InternalError();
	}
	}

	/**
	* Returns an array containing all of the elements in this list
	* in proper sequence (from first to last element).
	*
	* <p>The returned array will be "safe" in that no references to it are
	* maintained by this list. (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 the elements in this list
	*/
	public Object[] toArray() {
	return getArray().clone();
	}

	/**
	* Returns an array containing all of the elements in this list in
	* proper sequence (from first to last element); the runtime type of
	* the returned array is that of the specified array. If the list 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 list.
	*
	* <p>If this list fits in the specified array with room to spare
	* (i.e., the array has more elements than this list), the element in
	* the array immediately following the end of the list is set to
	* {@code null}. (This is useful in determining the length of this
	* list <i>only</i> if the caller knows that this list does not contain
	* any null elements.)
	*
	* <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 list known to contain only strings.
	* The following code can be used to dump the list 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 list 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 the elements in this list
	* @throws ArrayStoreException if the runtime type of the specified array
	* is not a supertype of the runtime type of every element in
	* this list
	* @throws NullPointerException if the specified array is null
	*/
	@SuppressWarnings("unchecked")
	public <T> T[] toArray(T[] a) {
	Object[] es = getArray();
	int len = es.length;
	if (a.length < len)
	return (T[]) Arrays.copyOf(es, len, a.getClass());
	else {
	System.arraycopy(es, 0, a, 0, len);
	if (a.length > len)
	a[len] = null;
	return a;
	}
	}

	// Positional Access Operations

	@SuppressWarnings("unchecked")
	static <E> E elementAt(Object[] a, int index) {
	return (E) a[index];
	}

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

	/**
	* {@inheritDoc}
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public E get(int index) {
	return elementAt(getArray(), index);
	}

	/**
	* Replaces the element at the specified position in this list with the
	* specified element.
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public E set(int index, E element) {
	synchronized (lock) {
	Object[] es = getArray();
	E oldValue = elementAt(es, index);

	if (oldValue != element) {
	es = es.clone();
	es[index] = element;
	setArray(es);
	}
	return oldValue;
	}
	}

	/**
	* Appends the specified element to the end of this list.
	*
	* @param e element to be appended to this list
	* @return {@code true} (as specified by {@link Collection#add})
	*/
	public boolean add(E e) {
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;
	es = Arrays.copyOf(es, len + 1);
	es[len] = e;
	setArray(es);
	return true;
	}
	}

	/**
	* Inserts the specified element at the specified position in this
	* list. Shifts the element currently at that position (if any) and
	* any subsequent elements to the right (adds one to their indices).
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public void add(int index, E element) {
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;
	if (index > len \|\| index < 0)
	throw new IndexOutOfBoundsException(outOfBounds(index, len));
	Object[] newElements;
	int numMoved = len - index;
	if (numMoved == 0)
	newElements = Arrays.copyOf(es, len + 1);
	else {
	newElements = new Object[len + 1];
	System.arraycopy(es, 0, newElements, 0, index);
	System.arraycopy(es, index, newElements, index + 1,
	numMoved);
	}
	newElements[index] = element;
	setArray(newElements);
	}
	}

	/**
	* Removes the element at the specified position in this list.
	* Shifts any subsequent elements to the left (subtracts one from their
	* indices). Returns the element that was removed from the list.
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public E remove(int index) {
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;
	E oldValue = elementAt(es, index);
	int numMoved = len - index - 1;
	Object[] newElements;
	if (numMoved == 0)
	newElements = Arrays.copyOf(es, len - 1);
	else {
	newElements = new Object[len - 1];
	System.arraycopy(es, 0, newElements, 0, index);
	System.arraycopy(es, index + 1, newElements, index,
	numMoved);
	}
	setArray(newElements);
	return oldValue;
	}
	}

	/**
	* Removes the first occurrence of the specified element from this list,
	* if it is present. If this list does not contain the element, it is
	* unchanged. More formally, removes the element with the lowest index
	* {@code i} such that {@code Objects.equals(o, get(i))}
	* (if such an element exists). Returns {@code true} if this list
	* contained the specified element (or equivalently, if this list
	* changed as a result of the call).
	*
	* @param o element to be removed from this list, if present
	* @return {@code true} if this list contained the specified element
	*/
	public boolean remove(Object o) {
	Object[] snapshot = getArray();
	int index = indexOfRange(o, snapshot, 0, snapshot.length);
	return index >= 0 && remove(o, snapshot, index);
	}

	/**
	* A version of remove(Object) using the strong hint that given
	* recent snapshot contains o at the given index.
	*/
	private boolean remove(Object o, Object[] snapshot, int index) {
	synchronized (lock) {
	Object[] current = getArray();
	int len = current.length;
	if (snapshot != current) findIndex: {
	int prefix = Math.min(index, len);
	for (int i = 0; i < prefix; i++) {
	if (current[i] != snapshot[i]
	&& Objects.equals(o, current[i])) {
	index = i;
	break findIndex;
	}
	}
	if (index >= len)
	return false;
	if (current[index] == o)
	break findIndex;
	index = indexOfRange(o, current, index, len);
	if (index < 0)
	return false;
	}
	Object[] newElements = new Object[len - 1];
	System.arraycopy(current, 0, newElements, 0, index);
	System.arraycopy(current, index + 1,
	newElements, index,
	len - index - 1);
	setArray(newElements);
	return true;
	}
	}

	/**
	* 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.)
	*
	* @param fromIndex index of first element to be removed
	* @param toIndex index after last element to be removed
	* @throws IndexOutOfBoundsException if fromIndex or toIndex out of range
	* ({@code fromIndex < 0 \|\| toIndex > size() \|\| toIndex < fromIndex})
	*/
	void removeRange(int fromIndex, int toIndex) {
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;

	if (fromIndex < 0 \|\| toIndex > len \|\| toIndex < fromIndex)
	throw new IndexOutOfBoundsException();
	int newlen = len - (toIndex - fromIndex);
	int numMoved = len - toIndex;
	if (numMoved == 0)
	setArray(Arrays.copyOf(es, newlen));
	else {
	Object[] newElements = new Object[newlen];
	System.arraycopy(es, 0, newElements, 0, fromIndex);
	System.arraycopy(es, toIndex, newElements,
	fromIndex, numMoved);
	setArray(newElements);
	}
	}
	}

	/**
	* Appends the element, if not present.
	*
	* @param e element to be added to this list, if absent
	* @return {@code true} if the element was added
	*/
	public boolean addIfAbsent(E e) {
	Object[] snapshot = getArray();
	return indexOfRange(e, snapshot, 0, snapshot.length) < 0
	&& addIfAbsent(e, snapshot);
	}

	/**
	* A version of addIfAbsent using the strong hint that given
	* recent snapshot does not contain e.
	*/
	private boolean addIfAbsent(E e, Object[] snapshot) {
	synchronized (lock) {
	Object[] current = getArray();
	int len = current.length;
	if (snapshot != current) {
	// Optimize for lost race to another addXXX operation
	int common = Math.min(snapshot.length, len);
	for (int i = 0; i < common; i++)
	if (current[i] != snapshot[i]
	&& Objects.equals(e, current[i]))
	return false;
	if (indexOfRange(e, current, common, len) >= 0)
	return false;
	}
	Object[] newElements = Arrays.copyOf(current, len + 1);
	newElements[len] = e;
	setArray(newElements);
	return true;
	}
	}

	/**
	* Returns {@code true} if this list contains all of the elements of the
	* specified collection.
	*
	* @param c collection to be checked for containment in this list
	* @return {@code true} if this list contains all of the elements of the
	* specified collection
	* @throws NullPointerException if the specified collection is null
	* @see #contains(Object)
	*/
	public boolean containsAll(Collection<?> c) {
	Object[] es = getArray();
	int len = es.length;
	for (Object e : c) {
	if (indexOfRange(e, es, 0, len) < 0)
	return false;
	}
	return true;
	}

	/**
	* Removes from this list all of its elements that are contained in
	* the specified collection. This is a particularly expensive operation
	* in this class because of the need for an internal temporary array.
	*
	* @param c collection containing elements to be removed from this list
	* @return {@code true} if this list changed as a result of the call
	* @throws ClassCastException if the class of an element of this list
	* is incompatible with the specified collection
	* (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>)
	* @throws NullPointerException if this list contains a null element and the
	* specified collection does not permit null elements
	* (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>),
	* or if the specified collection is null
	* @see #remove(Object)
	*/
	public boolean removeAll(Collection<?> c) {
	Objects.requireNonNull(c);
	return bulkRemove(e -> c.contains(e));
	}

	/**
	* Retains only the elements in this list that are contained in the
	* specified collection. In other words, removes from this list all of
	* its elements that are not contained in the specified collection.
	*
	* @param c collection containing elements to be retained in this list
	* @return {@code true} if this list changed as a result of the call
	* @throws ClassCastException if the class of an element of this list
	* is incompatible with the specified collection
	* (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>)
	* @throws NullPointerException if this list contains a null element and the
	* specified collection does not permit null elements
	* (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>),
	* or if the specified collection is null
	* @see #remove(Object)
	*/
	public boolean retainAll(Collection<?> c) {
	Objects.requireNonNull(c);
	return bulkRemove(e -> !c.contains(e));
	}

	/**
	* Appends all of the elements in the specified collection that
	* are not already contained in this list, to the end of
	* this list, in the order that they are returned by the
	* specified collection's iterator.
	*
	* @param c collection containing elements to be added to this list
	* @return the number of elements added
	* @throws NullPointerException if the specified collection is null
	* @see #addIfAbsent(Object)
	*/
	public int addAllAbsent(Collection<? extends E> c) {
	Object[] cs = c.toArray();
	if (cs.length == 0)
	return 0;
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;
	int added = 0;
	// uniquify and compact elements in cs
	for (int i = 0; i < cs.length; ++i) {
	Object e = cs[i];
	if (indexOfRange(e, es, 0, len) < 0 &&
	indexOfRange(e, cs, 0, added) < 0)
	cs[added++] = e;
	}
	if (added > 0) {
	Object[] newElements = Arrays.copyOf(es, len + added);
	System.arraycopy(cs, 0, newElements, len, added);
	setArray(newElements);
	}
	return added;
	}
	}

	/**
	* Removes all of the elements from this list.
	* The list will be empty after this call returns.
	*/
	public void clear() {
	synchronized (lock) {
	setArray(new Object[0]);
	}
	}

	/**
	* Appends all of the elements in the specified collection to the end
	* of this list, in the order that they are returned by the specified
	* collection's iterator.
	*
	* @param c collection containing elements to be added to this list
	* @return {@code true} if this list changed as a result of the call
	* @throws NullPointerException if the specified collection is null
	* @see #add(Object)
	*/
	public boolean addAll(Collection<? extends E> c) {
	Object[] cs = (c.getClass() == CopyOnWriteArrayList.class) ?
	((CopyOnWriteArrayList<?>)c).getArray() : c.toArray();
	if (cs.length == 0)
	return false;
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;
	Object[] newElements;
	if (len == 0 && cs.getClass() == Object[].class)
	newElements = cs;
	else {
	newElements = Arrays.copyOf(es, len + cs.length);
	System.arraycopy(cs, 0, newElements, len, cs.length);
	}
	setArray(newElements);
	return true;
	}
	}

	/**
	* Inserts all of the elements in the specified collection into this
	* list, starting at the specified position. Shifts the element
	* currently at that position (if any) and any subsequent elements to
	* the right (increases their indices). The new elements will appear
	* in this list in the order that they are returned by the
	* specified collection's iterator.
	*
	* @param index index at which to insert the first element
	* from the specified collection
	* @param c collection containing elements to be added to this list
	* @return {@code true} if this list changed as a result of the call
	* @throws IndexOutOfBoundsException {@inheritDoc}
	* @throws NullPointerException if the specified collection is null
	* @see #add(int,Object)
	*/
	public boolean addAll(int index, Collection<? extends E> c) {
	Object[] cs = c.toArray();
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;
	if (index > len \|\| index < 0)
	throw new IndexOutOfBoundsException(outOfBounds(index, len));
	if (cs.length == 0)
	return false;
	int numMoved = len - index;
	Object[] newElements;
	if (numMoved == 0)
	newElements = Arrays.copyOf(es, len + cs.length);
	else {
	newElements = new Object[len + cs.length];
	System.arraycopy(es, 0, newElements, 0, index);
	System.arraycopy(es, index,
	newElements, index + cs.length,
	numMoved);
	}
	System.arraycopy(cs, 0, newElements, index, cs.length);
	setArray(newElements);
	return true;
	}
	}

	/**
	* @throws NullPointerException {@inheritDoc}
	*/
	public void forEach(Consumer<? super E> action) {
	Objects.requireNonNull(action);
	for (Object x : getArray()) {
	@SuppressWarnings("unchecked") E e = (E) x;
	action.accept(e);
	}
	}

	/**
	* @throws NullPointerException {@inheritDoc}
	*/
	public boolean removeIf(Predicate<? super E> filter) {
	Objects.requireNonNull(filter);
	return bulkRemove(filter);
	}

	// A tiny bit set implementation

	private static long[] nBits(int n) {
	return new long[((n - 1) >> 6) + 1];
	}
	private static void setBit(long[] bits, int i) {
	bits[i >> 6] \|= 1L << i;
	}
	private static boolean isClear(long[] bits, int i) {
	return (bits[i >> 6] & (1L << i)) == 0;
	}

	private boolean bulkRemove(Predicate<? super E> filter) {
	synchronized (lock) {
	return bulkRemove(filter, 0, getArray().length);
	}
	}

	boolean bulkRemove(Predicate<? super E> filter, int i, int end) {
	// assert Thread.holdsLock(lock);
	final Object[] es = getArray();
	// Optimize for initial run of survivors
	for (; i < end && !filter.test(elementAt(es, i)); i++)
	;
	if (i < end) {
	final int beg = i;
	final long[] deathRow = nBits(end - beg);
	int deleted = 1;
	deathRow[0] = 1L; // set bit 0
	for (i = beg + 1; i < end; i++)
	if (filter.test(elementAt(es, i))) {
	setBit(deathRow, i - beg);
	deleted++;
	}
	// Did filter reentrantly modify the list?
	if (es != getArray())
	throw new ConcurrentModificationException();
	final Object[] newElts = Arrays.copyOf(es, es.length - deleted);
	int w = beg;
	for (i = beg; i < end; i++)
	if (isClear(deathRow, i - beg))
	newElts[w++] = es[i];
	System.arraycopy(es, i, newElts, w, es.length - i);
	setArray(newElts);
	return true;
	} else {
	if (es != getArray())
	throw new ConcurrentModificationException();
	return false;
	}
	}

	public void replaceAll(UnaryOperator<E> operator) {
	synchronized (lock) {
	replaceAllRange(operator, 0, getArray().length);
	}
	}

	void replaceAllRange(UnaryOperator<E> operator, int i, int end) {
	// assert Thread.holdsLock(lock);
	Objects.requireNonNull(operator);
	final Object[] es = getArray().clone();
	for (; i < end; i++)
	es[i] = operator.apply(elementAt(es, i));
	setArray(es);
	}

	public void sort(Comparator<? super E> c) {
	synchronized (lock) {
	sortRange(c, 0, getArray().length);
	}
	}

	@SuppressWarnings("unchecked")
	void sortRange(Comparator<? super E> c, int i, int end) {
	// assert Thread.holdsLock(lock);
	final Object[] es = getArray().clone();
	Arrays.sort(es, i, end, (Comparator<Object>)c);
	setArray(es);
	}

	/**
	* Saves this list to a stream (that is, serializes it).
	*
	* @param s the stream
	* @throws java.io.IOException if an I/O error occurs
	* @serialData The length of the array backing the list is emitted
	* (int), followed by all of its elements (each an Object)
	* in the proper order.
	*/
	private void writeObject(java.io.ObjectOutputStream s)
	throws java.io.IOException {

	s.defaultWriteObject();

	Object[] es = getArray();
	// Write out array length
	s.writeInt(es.length);

	// Write out all elements in the proper order.
	for (Object element : es)
	s.writeObject(element);
	}

	/**
	* Reconstitutes this list from a stream (that is, deserializes it).
	* @param s the stream
	* @throws ClassNotFoundException if the class of a serialized object
	* could not be found
	* @throws java.io.IOException if an I/O error occurs
	*/
	private void readObject(java.io.ObjectInputStream s)
	throws java.io.IOException, ClassNotFoundException {

	s.defaultReadObject();

	// bind to new lock
	resetLock();

	// Read in array length and allocate array
	int len = s.readInt();
	SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, len);
	Object[] es = new Object[len];

	// Read in all elements in the proper order.
	for (int i = 0; i < len; i++)
	es[i] = s.readObject();
	setArray(es);
	}

	/**
	* Returns a string representation of this list. The string
	* representation consists of the string representations of the list's
	* elements in the order they are returned by its iterator, enclosed in
	* square brackets ({@code "[]"}). Adjacent elements are separated by
	* the characters {@code ", "} (comma and space). Elements are
	* converted to strings as by {@link String#valueOf(Object)}.
	*
	* @return a string representation of this list
	*/
	public String toString() {
	return Arrays.toString(getArray());
	}

	/**
	* Compares the specified object with this list for equality.
	* Returns {@code true} if the specified object is the same object
	* as this object, or if it is also a {@link List} and the sequence
	* of elements returned by an {@linkplain List#iterator() iterator}
	* over the specified list is the same as the sequence returned by
	* an iterator over this list. The two sequences are considered to
	* be the same if they have the same length and corresponding
	* elements at the same position in the sequence are <em>equal</em>.
	* Two elements {@code e1} and {@code e2} are considered
	* <em>equal</em> if {@code Objects.equals(e1, e2)}.
	*
	* @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;

	List<?> list = (List<?>)o;
	Iterator<?> it = list.iterator();
	for (Object element : getArray())
	if (!it.hasNext() \|\| !Objects.equals(element, it.next()))
	return false;
	return !it.hasNext();
	}

	private static int hashCodeOfRange(Object[] es, int from, int to) {
	int hashCode = 1;
	for (int i = from; i < to; i++) {
	Object x = es[i];
	hashCode = 31 * hashCode + (x == null ? 0 : x.hashCode());
	}
	return hashCode;
	}

	/**
	* Returns the hash code value for this list.
	*
	* <p>This implementation uses the definition in {@link List#hashCode}.
	*
	* @return the hash code value for this list
	*/
	public int hashCode() {
	Object[] es = getArray();
	return hashCodeOfRange(es, 0, es.length);
	}

	/**
	* Returns an iterator over the elements in this list in proper sequence.
	*
	* <p>The returned iterator provides a snapshot of the state of the list
	* when the iterator was constructed. No synchronization is needed while
	* traversing the iterator. The iterator does <em>NOT</em> support the
	* {@code remove} method.
	*
	* @return an iterator over the elements in this list in proper sequence
	*/
	public Iterator<E> iterator() {
	return new COWIterator<E>(getArray(), 0);
	}

	/**
	* {@inheritDoc}
	*
	* <p>The returned iterator provides a snapshot of the state of the list
	* when the iterator was constructed. No synchronization is needed while
	* traversing the iterator. The iterator does <em>NOT</em> support the
	* {@code remove}, {@code set} or {@code add} methods.
	*/
	public ListIterator<E> listIterator() {
	return new COWIterator<E>(getArray(), 0);
	}

	/**
	* {@inheritDoc}
	*
	* <p>The returned iterator provides a snapshot of the state of the list
	* when the iterator was constructed. No synchronization is needed while
	* traversing the iterator. The iterator does <em>NOT</em> support the
	* {@code remove}, {@code set} or {@code add} methods.
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public ListIterator<E> listIterator(int index) {
	Object[] es = getArray();
	int len = es.length;
	if (index < 0 \|\| index > len)
	throw new IndexOutOfBoundsException(outOfBounds(index, len));

	return new COWIterator<E>(es, index);
	}

	/**
	* Returns a {@link Spliterator} over the elements in this list.
	*
	* <p>The {@code Spliterator} reports {@link Spliterator#IMMUTABLE},
	* {@link Spliterator#ORDERED}, {@link Spliterator#SIZED}, and
	* {@link Spliterator#SUBSIZED}.
	*
	* <p>The spliterator provides a snapshot of the state of the list
	* when the spliterator was constructed. No synchronization is needed while
	* operating on the spliterator.
	*
	* @return a {@code Spliterator} over the elements in this list
	* @since 1.8
	*/
	public Spliterator<E> spliterator() {
	return Spliterators.spliterator
	(getArray(), Spliterator.IMMUTABLE \| Spliterator.ORDERED);
	}

	static final class COWIterator<E> implements ListIterator<E> {
	/** Snapshot of the array */
	private final Object[] snapshot;
	/** Index of element to be returned by subsequent call to next. */
	private int cursor;

	COWIterator(Object[] es, int initialCursor) {
	cursor = initialCursor;
	snapshot = es;
	}

	public boolean hasNext() {
	return cursor < snapshot.length;
	}

	public boolean hasPrevious() {
	return cursor > 0;
	}

	@SuppressWarnings("unchecked")
	public E next() {
	if (! hasNext())
	throw new NoSuchElementException();
	return (E) snapshot[cursor++];
	}

	@SuppressWarnings("unchecked")
	public E previous() {
	if (! hasPrevious())
	throw new NoSuchElementException();
	return (E) snapshot[--cursor];
	}

	public int nextIndex() {
	return cursor;
	}

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

	/**
	* Not supported. Always throws UnsupportedOperationException.
	* @throws UnsupportedOperationException always; {@code remove}
	* is not supported by this iterator.
	*/
	public void remove() {
	throw new UnsupportedOperationException();
	}

	/**
	* Not supported. Always throws UnsupportedOperationException.
	* @throws UnsupportedOperationException always; {@code set}
	* is not supported by this iterator.
	*/
	public void set(E e) {
	throw new UnsupportedOperationException();
	}

	/**
	* Not supported. Always throws UnsupportedOperationException.
	* @throws UnsupportedOperationException always; {@code add}
	* is not supported by this iterator.
	*/
	public void add(E e) {
	throw new UnsupportedOperationException();
	}

	@Override
	public void forEachRemaining(Consumer<? super E> action) {
	Objects.requireNonNull(action);
	final int size = snapshot.length;
	int i = cursor;
	cursor = size;
	for (; i < size; i++)
	action.accept(elementAt(snapshot, i));
	}
	}

	/**
	* Returns a view of the portion of this list between
	* {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
	* The returned list is backed by this list, so changes in the
	* returned list are reflected in this list.
	*
	* <p>The semantics of the list returned by this method become
	* undefined if the backing list (i.e., this list) is modified in
	* any way other than via the returned list.
	*
	* @param fromIndex low endpoint (inclusive) of the subList
	* @param toIndex high endpoint (exclusive) of the subList
	* @return a view of the specified range within this list
	* @throws IndexOutOfBoundsException {@inheritDoc}
	*/
	public List<E> subList(int fromIndex, int toIndex) {
	synchronized (lock) {
	Object[] es = getArray();
	int len = es.length;
	int size = toIndex - fromIndex;
	if (fromIndex < 0 \|\| toIndex > len \|\| size < 0)
	throw new IndexOutOfBoundsException();
	return new COWSubList(es, fromIndex, size);
	}
	}

	/**
	* Sublist for CopyOnWriteArrayList.
	*/
	private class COWSubList implements List<E>, RandomAccess {
	private final int offset;
	private int size;
	private Object[] expectedArray;

	COWSubList(Object[] es, int offset, int size) {
	// assert Thread.holdsLock(lock);
	expectedArray = es;
	this.offset = offset;
	this.size = size;
	}

	private void checkForComodification() {
	// assert Thread.holdsLock(lock);
	if (getArray() != expectedArray)
	throw new ConcurrentModificationException();
	}

	private Object[] getArrayChecked() {
	// assert Thread.holdsLock(lock);
	Object[] a = getArray();
	if (a != expectedArray)
	throw new ConcurrentModificationException();
	return a;
	}

	private void rangeCheck(int index) {
	// assert Thread.holdsLock(lock);
	if (index < 0 \|\| index >= size)
	throw new IndexOutOfBoundsException(outOfBounds(index, size));
	}

	private void rangeCheckForAdd(int index) {
	// assert Thread.holdsLock(lock);
	if (index < 0 \|\| index > size)
	throw new IndexOutOfBoundsException(outOfBounds(index, size));
	}

	public Object[] toArray() {
	final Object[] es;
	final int offset;
	final int size;
	synchronized (lock) {
	es = getArrayChecked();
	offset = this.offset;
	size = this.size;
	}
	return Arrays.copyOfRange(es, offset, offset + size);
	}

	@SuppressWarnings("unchecked")
	public <T> T[] toArray(T[] a) {
	final Object[] es;
	final int offset;
	final int size;
	synchronized (lock) {
	es = getArrayChecked();
	offset = this.offset;
	size = this.size;
	}
	if (a.length < size)
	return (T[]) Arrays.copyOfRange(
	es, offset, offset + size, a.getClass());
	else {
	System.arraycopy(es, offset, a, 0, size);
	if (a.length > size)
	a[size] = null;
	return a;
	}
	}

	public int indexOf(Object o) {
	final Object[] es;
	final int offset;
	final int size;
	synchronized (lock) {
	es = getArrayChecked();
	offset = this.offset;
	size = this.size;
	}
	int i = indexOfRange(o, es, offset, offset + size);
	return (i == -1) ? -1 : i - offset;
	}

	public int lastIndexOf(Object o) {
	final Object[] es;
	final int offset;
	final int size;
	synchronized (lock) {
	es = getArrayChecked();
	offset = this.offset;
	size = this.size;
	}
	int i = lastIndexOfRange(o, es, offset, offset + size);
	return (i == -1) ? -1 : i - offset;
	}

	public boolean contains(Object o) {
	return indexOf(o) >= 0;
	}

	public boolean containsAll(Collection<?> c) {
	final Object[] es;
	final int offset;
	final int size;
	synchronized (lock) {
	es = getArrayChecked();
	offset = this.offset;
	size = this.size;
	}
	for (Object o : c)
	if (indexOfRange(o, es, offset, offset + size) < 0)
	return false;
	return true;
	}

	public boolean isEmpty() {
	return size() == 0;
	}

	public String toString() {
	return Arrays.toString(toArray());
	}

	public int hashCode() {
	final Object[] es;
	final int offset;
	final int size;
	synchronized (lock) {
	es = getArrayChecked();
	offset = this.offset;
	size = this.size;
	}
	return hashCodeOfRange(es, offset, offset + size);
	}

	public boolean equals(Object o) {
	if (o == this)
	return true;
	if (!(o instanceof List))
	return false;
	Iterator<?> it = ((List<?>)o).iterator();

	final Object[] es;
	final int offset;
	final int size;
	synchronized (lock) {
	es = getArrayChecked();
	offset = this.offset;
	size = this.size;
	}

	for (int i = offset, end = offset + size; i < end; i++)
	if (!it.hasNext() \|\| !Objects.equals(es[i], it.next()))
	return false;
	return !it.hasNext();
	}

	public E set(int index, E element) {
	synchronized (lock) {
	rangeCheck(index);
	checkForComodification();
	E x = CopyOnWriteArrayList.this.set(offset + index, element);
	expectedArray = getArray();
	return x;
	}
	}

	public E get(int index) {
	synchronized (lock) {
	rangeCheck(index);
	checkForComodification();
	return CopyOnWriteArrayList.this.get(offset + index);
	}
	}

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

	public boolean add(E element) {
	synchronized (lock) {
	checkForComodification();
	CopyOnWriteArrayList.this.add(offset + size, element);
	expectedArray = getArray();
	size++;
	}
	return true;
	}

	public void add(int index, E element) {
	synchronized (lock) {
	checkForComodification();
	rangeCheckForAdd(index);
	CopyOnWriteArrayList.this.add(offset + index, element);
	expectedArray = getArray();
	size++;
	}
	}

	public boolean addAll(Collection<? extends E> c) {
	synchronized (lock) {
	final Object[] oldArray = getArrayChecked();
	boolean modified =
	CopyOnWriteArrayList.this.addAll(offset + size, c);
	size += (expectedArray = getArray()).length - oldArray.length;
	return modified;
	}
	}

	public boolean addAll(int index, Collection<? extends E> c) {
	synchronized (lock) {
	rangeCheckForAdd(index);
	final Object[] oldArray = getArrayChecked();
	boolean modified =
	CopyOnWriteArrayList.this.addAll(offset + index, c);
	size += (expectedArray = getArray()).length - oldArray.length;
	return modified;
	}
	}

	public void clear() {
	synchronized (lock) {
	checkForComodification();
	removeRange(offset, offset + size);
	expectedArray = getArray();
	size = 0;
	}
	}

	public E remove(int index) {
	synchronized (lock) {
	rangeCheck(index);
	checkForComodification();
	E result = CopyOnWriteArrayList.this.remove(offset + index);
	expectedArray = getArray();
	size--;
	return result;
	}
	}

	public boolean remove(Object o) {
	synchronized (lock) {
	checkForComodification();
	int index = indexOf(o);
	if (index == -1)
	return false;
	remove(index);
	return true;
	}
	}

	public Iterator<E> iterator() {
	return listIterator(0);
	}

	public ListIterator<E> listIterator() {
	return listIterator(0);
	}

	public ListIterator<E> listIterator(int index) {
	synchronized (lock) {
	checkForComodification();
	rangeCheckForAdd(index);
	return new COWSubListIterator<E>(
	CopyOnWriteArrayList.this, index, offset, size);
	}
	}

	public List<E> subList(int fromIndex, int toIndex) {
	synchronized (lock) {
	checkForComodification();
	if (fromIndex < 0 \|\| toIndex > size \|\| fromIndex > toIndex)
	throw new IndexOutOfBoundsException();
	return new COWSubList(expectedArray, fromIndex + offset, toIndex - fromIndex);
	}
	}

	public void forEach(Consumer<? super E> action) {
	Objects.requireNonNull(action);
	int i, end; final Object[] es;
	synchronized (lock) {
	es = getArrayChecked();
	i = offset;
	end = i + size;
	}
	for (; i < end; i++)
	action.accept(elementAt(es, i));
	}

	public void replaceAll(UnaryOperator<E> operator) {
	synchronized (lock) {
	checkForComodification();
	replaceAllRange(operator, offset, offset + size);
	expectedArray = getArray();
	}
	}

	public void sort(Comparator<? super E> c) {
	synchronized (lock) {
	checkForComodification();
	sortRange(c, offset, offset + size);
	expectedArray = getArray();
	}
	}

	public boolean removeAll(Collection<?> c) {
	Objects.requireNonNull(c);
	return bulkRemove(e -> c.contains(e));
	}

	public boolean retainAll(Collection<?> c) {
	Objects.requireNonNull(c);
	return bulkRemove(e -> !c.contains(e));
	}

	public boolean removeIf(Predicate<? super E> filter) {
	Objects.requireNonNull(filter);
	return bulkRemove(filter);
	}

	private boolean bulkRemove(Predicate<? super E> filter) {
	synchronized (lock) {
	final Object[] oldArray = getArrayChecked();
	boolean modified = CopyOnWriteArrayList.this.bulkRemove(
	filter, offset, offset + size);
	size += (expectedArray = getArray()).length - oldArray.length;
	return modified;
	}
	}

	public Spliterator<E> spliterator() {
	synchronized (lock) {
	return Spliterators.spliterator(
	getArrayChecked(), offset, offset + size,
	Spliterator.IMMUTABLE \| Spliterator.ORDERED);
	}
	}

	}

	private static class COWSubListIterator<E> implements ListIterator<E> {
	private final ListIterator<E> it;
	private final int offset;
	private final int size;

	COWSubListIterator(List<E> l, int index, int offset, int size) {
	this.offset = offset;
	this.size = size;
	it = l.listIterator(index + offset);
	}

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

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

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

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

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

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

	public void remove() {
	throw new UnsupportedOperationException();
	}

	public void set(E e) {
	throw new UnsupportedOperationException();
	}

	public void add(E e) {
	throw new UnsupportedOperationException();
	}

	@Override
	@SuppressWarnings("unchecked")
	public void forEachRemaining(Consumer<? super E> action) {
	Objects.requireNonNull(action);
	while (hasNext()) {
	action.accept(it.next());
	}
	}
	}

	/** Initializes the lock; for use when deserializing or cloning. */
	private void resetLock() {
	Field lockField = java.security.AccessController.doPrivileged(
	(java.security.PrivilegedAction<Field>) () -> {
	try {
	Field f = CopyOnWriteArrayList.class
	.getDeclaredField("lock");
	f.setAccessible(true);
	return f;
	} catch (ReflectiveOperationException e) {
	throw new Error(e);
	}});
	try {
	lockField.set(this, new Object());
	} catch (IllegalAccessException e) {
	throw new Error(e);
	}
	}
	}

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