/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.collections4.list;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.lang.reflect.Array;
  import java.util.AbstractList;
  import java.util.Collection;
  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 org.apache.commons.collections4.CollectionUtils;
  import org.apache.commons.collections4.OrderedIterator;
  
  /**
   * An abstract implementation of a linked list which provides numerous points for
   * subclasses to override.
   * <p>
   * Overridable methods are provided to change the storage node and to change how
   * nodes are added to and removed. Hopefully, all you need for unusual subclasses
   * is here.
   * </p>
   *
   * @param <E> the type of elements in this list
   * @since 3.0
   * @deprecated use {@link AbstractLinkedListForJava21} instead
   */
  @Deprecated
  public abstract class AbstractLinkedList<E> implements List<E> {
  
      /*
       * Implementation notes:
       * - a standard circular doubly-linked list
       * - a marker node is stored to mark the start and the end of the list
       * - node creation and removal always occurs through createNode() and
       *   removeNode().
       * - a modification count is kept, with the same semantics as
       * {@link java.util.LinkedList}.
       * - respects {@link AbstractList#modCount}
       */
  
      /**
       * A list iterator over the linked list.
       *
       * @param <E> the type of elements in this iterator.
       */
      protected static class LinkedListIterator<E> implements ListIterator<E>, OrderedIterator<E> {
  
          /** The parent list */
          protected final AbstractLinkedList<E> parent;
  
          /**
           * The node that will be returned by {@link #next()}. If this is equal
           * to {@link AbstractLinkedList#header} then there are no more values to return.
           */
          protected Node<E> next;
  
          /**
           * The index of {@link #next}.
           */
          protected int nextIndex;
  
          /**
           * The last node that was returned by {@link #next()} or {@link
           * #previous()}. Set to {@code null} if {@link #next()} or {@link
           * #previous()} haven't been called, or if the node has been removed
           * with {@link #remove()} or a new node added with {@link #add(Object)}.
           * Should be accessed through {@link #getLastNodeReturned()} to enforce
           * this behavior.
           */
          protected Node<E> current;
  
          /**
           * The modification count that the list is expected to have. If the list
           * doesn't have this count, then a
           * {@link java.util.ConcurrentModificationException} may be thrown by
           * the operations.
           */
          protected int expectedModCount;
 
         /**
          * Create a ListIterator for a list.
          *
          * @param parent  the parent list
          * @param fromIndex  the index to start at
          * @throws IndexOutOfBoundsException if fromIndex is less than 0 or greater than the size of the list
          */
         protected LinkedListIterator(final AbstractLinkedList<E> parent, final int fromIndex)
                 throws IndexOutOfBoundsException {
             this.parent = parent;
             this.expectedModCount = parent.modCount;
             this.next = parent.getNode(fromIndex, true);
             this.nextIndex = fromIndex;
         }
 
         @Override
         public void add(final E obj) {
             checkModCount();
             parent.addNodeBefore(next, obj);
             current = null;
             nextIndex++;
             expectedModCount++;
         }
 
         /**
          * Checks the modification count of the list is the value that this
          * object expects.
          *
          * @throws ConcurrentModificationException If the list's modification
          * count isn't the value that was expected.
          */
         protected void checkModCount() {
             if (parent.modCount != expectedModCount) {
                 throw new ConcurrentModificationException();
             }
         }
 
         /**
          * Gets the last node returned.
          *
          * @return the last node returned
          * @throws IllegalStateException If {@link #next()} or {@link #previous()} haven't been called,
          * or if the node has been removed with {@link #remove()} or a new node added with {@link #add(Object)}.
          */
         protected Node<E> getLastNodeReturned() throws IllegalStateException {
             if (current == null) {
                 throw new IllegalStateException();
             }
             return current;
         }
 
         @Override
         public boolean hasNext() {
             return next != parent.header;
         }
 
         @Override
         public boolean hasPrevious() {
             return next.previous != parent.header;
         }
 
         @Override
         public E next() {
             checkModCount();
             if (!hasNext()) {
                 throw new NoSuchElementException("No element at index " + nextIndex + ".");
             }
             final E value = next.getValue();
             current = next;
             next = next.next;
             nextIndex++;
             return value;
         }
 
         @Override
         public int nextIndex() {
             return nextIndex;
         }
 
         @Override
         public E previous() {
             checkModCount();
             if (!hasPrevious()) {
                 throw new NoSuchElementException("Already at start of list.");
             }
             next = next.previous;
             final E value = next.getValue();
             current = next;
             nextIndex--;
             return value;
         }
 
         @Override
         public int previousIndex() {
             // not normally overridden, as relative to nextIndex()
             return nextIndex() - 1;
         }
 
         @Override
         public void remove() {
             checkModCount();
             if (current == next) {
                 // remove() following previous()
                 next = next.next;
                 parent.removeNode(getLastNodeReturned());
             } else {
                 // remove() following next()
                 parent.removeNode(getLastNodeReturned());
                 nextIndex--;
             }
             current = null;
             expectedModCount++;
         }
 
         @Override
         public void set(final E obj) {
             checkModCount();
             getLastNodeReturned().setValue(obj);
         }
 
     }
 
     /**
      * The sublist implementation for AbstractLinkedList.
      *
      * @param <E> the type of elements in this list.
      */
     protected static class LinkedSubList<E> extends AbstractList<E> {
         /** The main list */
         AbstractLinkedList<E> parent;
         /** Offset from the main list */
         int offset;
         /** Sublist size */
         int size;
         /** Sublist modCount */
         int expectedModCount;
 
         protected LinkedSubList(final AbstractLinkedList<E> parent, final int fromIndex, final int toIndex) {
             if (fromIndex < 0) {
                 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
             }
             if (toIndex > parent.size()) {
                 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
             }
             if (fromIndex > toIndex) {
                 throw new IllegalArgumentException("fromIndex(" + fromIndex + ") > toIndex(" + toIndex + ")");
             }
             this.parent = parent;
             this.offset = fromIndex;
             this.size = toIndex - fromIndex;
             this.expectedModCount = parent.modCount;
         }
 
         @Override
         public void add(final int index, final E obj) {
             rangeCheck(index, size + 1);
             checkModCount();
             parent.add(index + offset, obj);
             expectedModCount = parent.modCount;
             size++;
             modCount++;
         }
 
         @Override
         public boolean addAll(final Collection<? extends E> coll) {
             return addAll(size, coll);
         }
 
         @Override
         public boolean addAll(final int index, final Collection<? extends E> coll) {
             rangeCheck(index, size + 1);
             final int cSize = coll.size();
             if (cSize == 0) {
                 return false;
             }
 
             checkModCount();
             parent.addAll(offset + index, coll);
             expectedModCount = parent.modCount;
             size += cSize;
             modCount++;
             return true;
         }
 
         protected void checkModCount() {
             if (parent.modCount != expectedModCount) {
                 throw new ConcurrentModificationException();
             }
         }
 
         @Override
         public void clear() {
             checkModCount();
             final Iterator<E> it = iterator();
             while (it.hasNext()) {
                 it.next();
                 it.remove();
             }
         }
 
         @Override
         public E get(final int index) {
             rangeCheck(index, size);
             checkModCount();
             return parent.get(index + offset);
         }
 
         @Override
         public Iterator<E> iterator() {
             checkModCount();
             return parent.createSubListIterator(this);
         }
 
         @Override
         public ListIterator<E> listIterator(final int index) {
             rangeCheck(index, size + 1);
             checkModCount();
             return parent.createSubListListIterator(this, index);
         }
 
         protected void rangeCheck(final int index, final int beyond) {
             if (index < 0 || index >= beyond) {
                 throw new IndexOutOfBoundsException("Index '" + index + "' out of bounds for size '" + size + "'");
             }
         }
 
         @Override
         public E remove(final int index) {
             rangeCheck(index, size);
             checkModCount();
             final E result = parent.remove(index + offset);
             expectedModCount = parent.modCount;
             size--;
             modCount++;
             return result;
         }
 
         @Override
         public E set(final int index, final E obj) {
             rangeCheck(index, size);
             checkModCount();
             return parent.set(index + offset, obj);
         }
 
         @Override
         public int size() {
             checkModCount();
             return size;
         }
 
         @Override
         public List<E> subList(final int fromIndexInclusive, final int toIndexExclusive) {
             return new LinkedSubList<>(parent, fromIndexInclusive + offset, toIndexExclusive + offset);
         }
     }
 
     /**
      * A list iterator over the linked sub list.
      *
      * @param <E> the type of elements in this iterator.
      */
     protected static class LinkedSubListIterator<E> extends LinkedListIterator<E> {
 
         /** The sub list */
         protected final LinkedSubList<E> sub;
 
         protected LinkedSubListIterator(final LinkedSubList<E> sub, final int startIndex) {
             super(sub.parent, startIndex + sub.offset);
             this.sub = sub;
         }
 
         @Override
         public void add(final E obj) {
             super.add(obj);
             sub.expectedModCount = parent.modCount;
             sub.size++;
         }
 
         @Override
         public boolean hasNext() {
             return nextIndex() < sub.size;
         }
 
         @Override
         public boolean hasPrevious() {
             return previousIndex() >= 0;
         }
 
         @Override
         public int nextIndex() {
             return super.nextIndex() - sub.offset;
         }
 
         @Override
         public void remove() {
             super.remove();
             sub.expectedModCount = parent.modCount;
             sub.size--;
         }
     }
 
     /**
      * A node within the linked list.
      * <p>
      * From Commons Collections 3.1, all access to the {@code value} property
      * is via the methods on this class.
      */
     protected static class Node<E> {
 
         /** A pointer to the node before this node */
         protected Node<E> previous;
         /** A pointer to the node after this node */
         protected Node<E> next;
         /** The object contained within this node */
         protected E value;
 
         /**
          * Constructs a new header node.
          */
         protected Node() {
             previous = this;
             next = this;
         }
 
         /**
          * Constructs a new node.
          *
          * @param value  the value to store
          */
         protected Node(final E value) {
             this.value = value;
         }
 
         /**
          * Constructs a new node.
          *
          * @param previous  the previous node in the list
          * @param next  the next node in the list
          * @param value  the value to store
          */
         protected Node(final Node<E> previous, final Node<E> next, final E value) {
             this.previous = previous;
             this.next = next;
             this.value = value;
         }
 
         /**
          * Gets the next node.
          *
          * @return the next node
          * @since 3.1
          */
         protected Node<E> getNextNode() {
             return next;
         }
 
         /**
          * Gets the previous node.
          *
          * @return the previous node
          * @since 3.1
          */
         protected Node<E> getPreviousNode() {
             return previous;
         }
 
         /**
          * Gets the value of the node.
          *
          * @return the value
          * @since 3.1
          */
         protected E getValue() {
             return value;
         }
 
         /**
          * Sets the next node.
          *
          * @param next  the next node
          * @since 3.1
          */
         protected void setNextNode(final Node<E> next) {
             this.next = next;
         }
 
         /**
          * Sets the previous node.
          *
          * @param previous  the previous node
          * @since 3.1
          */
         protected void setPreviousNode(final Node<E> previous) {
             this.previous = previous;
         }
 
         /**
          * Sets the value of the node.
          *
          * @param value  the value
          * @since 3.1
          */
         protected void setValue(final E value) {
             this.value = value;
         }
     }
 
     /**
      * A {@link Node} which indicates the start and end of the list and does not
      * hold a value. The value of {@code next} is the first item in the
      * list. The value of {@code previous} is the last item in the list.
      */
     transient Node<E> header;
 
     /** The size of the list */
     transient int size;
 
     /** Modification count for iterators */
     transient int modCount;
 
     /**
      * Constructor that does nothing (intended for deserialization).
      * <p>
      * If this constructor is used by a serializable subclass then the init()
      * method must be called.
      */
     protected AbstractLinkedList() {
     }
 
     /**
      * Constructs a list copying data from the specified collection.
      *
      * @param coll  the collection to copy
      */
     protected AbstractLinkedList(final Collection<? extends E> coll) {
         init();
         addAll(coll);
     }
 
     @Override
     public boolean add(final E value) {
         addLast(value);
         return true;
     }
 
     @Override
     public void add(final int index, final E value) {
         final Node<E> node = getNode(index, true);
         addNodeBefore(node, value);
     }
 
     @Override
     public boolean addAll(final Collection<? extends E> coll) {
         return addAll(size, coll);
     }
 
     @Override
     public boolean addAll(final int index, final Collection<? extends E> coll) {
         final Node<E> node = getNode(index, true);
         for (final E e : coll) {
             addNodeBefore(node, e);
         }
         return true;
     }
 
     public boolean addFirst(final E o) {
         addNodeAfter(header, o);
         return true;
     }
 
     public boolean addLast(final E o) {
         addNodeBefore(header, o);
         return true;
     }
 
     /**
      * Inserts a new node into the list.
      *
      * @param nodeToInsert  new node to insert
      * @param insertBeforeNode  node to insert before
      * @throws NullPointerException if either node is null
      */
     protected void addNode(final Node<E> nodeToInsert, final Node<E> insertBeforeNode) {
         Objects.requireNonNull(nodeToInsert, "nodeToInsert");
         Objects.requireNonNull(insertBeforeNode, "insertBeforeNode");
         nodeToInsert.next = insertBeforeNode;
         nodeToInsert.previous = insertBeforeNode.previous;
         insertBeforeNode.previous.next = nodeToInsert;
         insertBeforeNode.previous = nodeToInsert;
         size++;
         modCount++;
     }
 
     /**
      * Creates a new node with the specified object as its
      * {@code value} and inserts it after {@code node}.
      * <p>
      * This implementation uses {@link #createNode(Object)} and
      * {@link #addNode(AbstractLinkedList.Node,AbstractLinkedList.Node)}.
      *
      * @param node  node to insert after
      * @param value  value of the newly added node
      * @throws NullPointerException if {@code node} is null
      */
     protected void addNodeAfter(final Node<E> node, final E value) {
         final Node<E> newNode = createNode(value);
         addNode(newNode, node.next);
     }
 
     /**
      * Creates a new node with the specified object as its
      * {@code value} and inserts it before {@code node}.
      * <p>
      * This implementation uses {@link #createNode(Object)} and
      * {@link #addNode(AbstractLinkedList.Node,AbstractLinkedList.Node)}.
      *
      * @param node  node to insert before
      * @param value  value of the newly added node
      * @throws NullPointerException if {@code node} is null
      */
     protected void addNodeBefore(final Node<E> node, final E value) {
         final Node<E> newNode = createNode(value);
         addNode(newNode, node);
     }
 
     @Override
     public void clear() {
         removeAllNodes();
     }
 
     @Override
     public boolean contains(final Object value) {
         return indexOf(value) != -1;
     }
 
     @Override
     public boolean containsAll(final Collection<?> coll) {
         for (final Object o : coll) {
             if (!contains(o)) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Creates a new node with previous, next and element all set to null.
      * This implementation creates a new empty Node.
      * Subclasses can override this to create a different class.
      *
      * @return  newly created node
      */
     protected Node<E> createHeaderNode() {
         return new Node<>();
     }
 
     /**
      * Creates a new node with the specified properties.
      * This implementation creates a new Node with data.
      * Subclasses can override this to create a different class.
      *
      * @param value  value of the new node
      * @return a new node containing the value
      */
     protected Node<E> createNode(final E value) {
         return new Node<>(value);
     }
 
     /**
      * Creates an iterator for the sublist.
      *
      * @param subList  the sublist to get an iterator for
      * @return a new iterator on the given sublist
      */
     protected Iterator<E> createSubListIterator(final LinkedSubList<E> subList) {
         return createSubListListIterator(subList, 0);
     }
 
     /**
      * Creates a list iterator for the sublist.
      *
      * @param subList  the sublist to get an iterator for
      * @param fromIndex  the index to start from, relative to the sublist
      * @return a new list iterator on the given sublist
      */
     protected ListIterator<E> createSubListListIterator(final LinkedSubList<E> subList, final int fromIndex) {
         return new LinkedSubListIterator<>(subList, fromIndex);
     }
 
     /**
      * Deserializes the data held in this object to the stream specified.
      * <p>
      * The first serializable subclass must call this method from
      * {@code readObject}.
      *
      * @param inputStream  the stream to read the object from
      * @throws IOException  if any error occurs while reading from the stream
      * @throws ClassNotFoundException  if a class read from the stream can not be loaded
      */
     @SuppressWarnings("unchecked")
     protected void doReadObject(final ObjectInputStream inputStream) throws IOException, ClassNotFoundException {
         init();
         final int size = inputStream.readInt();
         for (int i = 0; i < size; i++) {
             add((E) inputStream.readObject());
         }
     }
 
     /**
      * Serializes the data held in this object to the stream specified.
      * <p>
      * The first serializable subclass must call this method from
      * {@code writeObject}.
      *
      * @param outputStream  the stream to write the object to
      * @throws IOException  if anything goes wrong
      */
     protected void doWriteObject(final ObjectOutputStream outputStream) throws IOException {
         // Write the size so we know how many nodes to read back
         outputStream.writeInt(size());
         for (final E e : this) {
             outputStream.writeObject(e);
         }
     }
 
     @Override
     public boolean equals(final Object obj) {
         if (obj == this) {
             return true;
         }
         if (!(obj instanceof List)) {
             return false;
         }
         final List<?> other = (List<?>) obj;
         if (other.size() != size()) {
             return false;
         }
         final ListIterator<?> it1 = listIterator();
         final ListIterator<?> it2 = other.listIterator();
         while (it1.hasNext() && it2.hasNext()) {
             if (!Objects.equals(it1.next(), it2.next())) {
                 return false;
             }
         }
         return !(it1.hasNext() || it2.hasNext());
     }
 
     @Override
     public E get(final int index) {
         final Node<E> node = getNode(index, false);
         return node.getValue();
     }
 
     public E getFirst() {
         final Node<E> node = header.next;
         if (node == header) {
             throw new NoSuchElementException();
         }
         return node.getValue();
     }
 
     public E getLast() {
         final Node<E> node = header.previous;
         if (node == header) {
             throw new NoSuchElementException();
         }
         return node.getValue();
     }
 
     /**
      * Gets the node at a particular index.
      *
      * @param index  the index, starting from 0
      * @param endMarkerAllowed  whether or not the end marker can be returned if
      * startIndex is set to the list's size
      * @return the node at the given index
      * @throws IndexOutOfBoundsException if the index is less than 0; equal to
      * the size of the list and endMakerAllowed is false; or greater than the
      * size of the list
      */
     protected Node<E> getNode(final int index, final boolean endMarkerAllowed) throws IndexOutOfBoundsException {
         // Check the index is within the bounds
         if (index < 0) {
             throw new IndexOutOfBoundsException("Couldn't get the node: " +
                     "index (" + index + ") less than zero.");
         }
         if (!endMarkerAllowed && index == size) {
             throw new IndexOutOfBoundsException("Couldn't get the node: " +
                     "index (" + index + ") is the size of the list.");
         }
         if (index > size) {
             throw new IndexOutOfBoundsException("Couldn't get the node: " +
                     "index (" + index + ") greater than the size of the " +
                     "list (" + size + ").");
         }
         // Search the list and get the node
         Node<E> node;
         if (index < size / 2) {
             // Search forwards
             node = header.next;
             for (int currentIndex = 0; currentIndex < index; currentIndex++) {
                 node = node.next;
             }
         } else {
             // Search backwards
             node = header;
             for (int currentIndex = size; currentIndex > index; currentIndex--) {
                 node = node.previous;
             }
         }
         return node;
     }
 
     @Override
     public int hashCode() {
         int hashCode = 1;
         for (final E e : this) {
             hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode());
         }
         return hashCode;
     }
 
     @Override
     public int indexOf(final Object value) {
         int i = 0;
         for (Node<E> node = header.next; node != header; node = node.next) {
             if (isEqualValue(node.getValue(), value)) {
                 return i;
             }
             i++;
         }
         return CollectionUtils.INDEX_NOT_FOUND;
     }
 
     /**
      * The equivalent of a default constructor, broken out so it can be called
      * by any constructor and by {@code readObject}.
      * Subclasses which override this method should make sure they call super,
      * so the list is initialized properly.
      */
     protected void init() {
         header = createHeaderNode();
     }
 
     @Override
     public boolean isEmpty() {
         return size() == 0;
     }
 
     /**
      * Compares two values for equals.
      * This implementation uses the equals method.
      * Subclasses can override this to match differently.
      *
      * @param value1  the first value to compare, may be null
      * @param value2  the second value to compare, may be null
      * @return true if equal
      */
     protected boolean isEqualValue(final Object value1, final Object value2) {
         return Objects.equals(value1, value2);
     }
 
     @Override
     public Iterator<E> iterator() {
         return listIterator();
     }
 
     @Override
     public int lastIndexOf(final Object value) {
         int i = size - 1;
         for (Node<E> node = header.previous; node != header; node = node.previous) {
             if (isEqualValue(node.getValue(), value)) {
                 return i;
             }
             i--;
         }
         return CollectionUtils.INDEX_NOT_FOUND;
     }
 
     @Override
     public ListIterator<E> listIterator() {
         return new LinkedListIterator<>(this, 0);
     }
 
     @Override
     public ListIterator<E> listIterator(final int fromIndex) {
         return new LinkedListIterator<>(this, fromIndex);
     }
 
     @Override
     public E remove(final int index) {
         final Node<E> node = getNode(index, false);
         final E oldValue = node.getValue();
         removeNode(node);
         return oldValue;
     }
 
     @Override
     public boolean remove(final Object value) {
         for (Node<E> node = header.next; node != header; node = node.next) {
             if (isEqualValue(node.getValue(), value)) {
                 removeNode(node);
                 return true;
             }
         }
         return false;
     }
 
     /**
      * {@inheritDoc}
      * <p>
      * This implementation iterates over the elements of this list, checking each element in
      * turn to see if it's contained in {@code coll}. If it's contained, it's removed
      * from this list. As a consequence, it is advised to use a collection type for
      * {@code coll} that provides a fast (e.g. O(1)) implementation of
      * {@link Collection#contains(Object)}.
      */
     @Override
     public boolean removeAll(final Collection<?> coll) {
         boolean modified = false;
         final Iterator<E> it = iterator();
         while (it.hasNext()) {
             if (coll.contains(it.next())) {
                 it.remove();
                 modified = true;
             }
         }
         return modified;
     }
 
     /**
      * Removes all nodes by resetting the circular list marker.
      */
     protected void removeAllNodes() {
         header.next = header;
         header.previous = header;
         size = 0;
         modCount++;
     }
 
     public E removeFirst() {
         final Node<E> node = header.next;
         if (node == header) {
             throw new NoSuchElementException();
         }
         final E oldValue = node.getValue();
         removeNode(node);
         return oldValue;
     }
 
     public E removeLast() {
         final Node<E> node = header.previous;
         if (node == header) {
             throw new NoSuchElementException();
         }
         final E oldValue = node.getValue();
         removeNode(node);
         return oldValue;
     }
 
     /**
      * Removes the specified node from the list.
      *
      * @param node  the node to remove
      * @throws NullPointerException if {@code node} is null
      */
     protected void removeNode(final Node<E> node) {
         Objects.requireNonNull(node, "node");
         node.previous.next = node.next;
         node.next.previous = node.previous;
         size--;
         modCount++;
     }
 
     /**
      * {@inheritDoc}
      * <p>
      * This implementation iterates over the elements of this list, checking each element in
      * turn to see if it's contained in {@code coll}. If it's not contained, it's removed
      * from this list. As a consequence, it is advised to use a collection type for
      * {@code coll} that provides a fast (e.g. O(1)) implementation of
      * {@link Collection#contains(Object)}.
      */
     @Override
     public boolean retainAll(final Collection<?> coll) {
         boolean modified = false;
         final Iterator<E> it = iterator();
         while (it.hasNext()) {
             if (!coll.contains(it.next())) {
                 it.remove();
                 modified = true;
             }
         }
         return modified;
     }
 
     @Override
     public E set(final int index, final E value) {
         final Node<E> node = getNode(index, false);
         final E oldValue = node.getValue();
         updateNode(node, value);
         return oldValue;
     }
 
     @Override
     public int size() {
         return size;
     }
 
     /**
      * Gets a sublist of the main list.
      *
      * @param fromIndexInclusive  the index to start from
      * @param toIndexExclusive  the index to end at
      * @return the new sublist
      */
     @Override
     public List<E> subList(final int fromIndexInclusive, final int toIndexExclusive) {
         return new LinkedSubList<>(this, fromIndexInclusive, toIndexExclusive);
     }
 
     @Override
     public Object[] toArray() {
         return toArray(new Object[size]);
     }
 
     @Override
     @SuppressWarnings("unchecked")
     public <T> T[] toArray(T[] array) {
         // Extend the array if needed
         if (array.length < size) {
             final Class<?> componentType = array.getClass().getComponentType();
             array = (T[]) Array.newInstance(componentType, size);
         }
         // Copy the values into the array
         int i = 0;
         for (Node<E> node = header.next; node != header; node = node.next, i++) {
             array[i] = (T) node.getValue();
         }
         // Set the value after the last value to null
         if (array.length > size) {
             array[size] = null;
         }
         return array;
     }
 
     @Override
     public String toString() {
         if (isEmpty()) {
             return "[]";
         }
         final StringBuilder buf = new StringBuilder(16 * size());
         buf.append(CollectionUtils.DEFAULT_TOSTRING_PREFIX);
 
         final Iterator<E> it = iterator();
         boolean hasNext = it.hasNext();
         while (hasNext) {
             final Object value = it.next();
             buf.append(value == this ? "(this Collection)" : value);
             hasNext = it.hasNext();
             if (hasNext) {
                 buf.append(", ");
             }
         }
         buf.append(CollectionUtils.DEFAULT_TOSTRING_SUFFIX);
         return buf.toString();
     }
 
     /**
      * Updates the node with a new value.
      * This implementation sets the value on the node.
      * Subclasses can override this to record the change.
      *
      * @param node  node to update
      * @param value  new value of the node
      */
     protected void updateNode(final Node<E> node, final E value) {
         node.setValue(value);
     }
 
 }