/*

 * Copyright (c) 1997, 2010, 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;

/**

 * Resizable-array implementation of the <tt>List</tt> interface.  Implements

 * all optional list operations, and permits all elements, including

 * <tt>null</tt>.  In addition to implementing the <tt>List</tt> interface,

 * this class provides methods to manipulate the size of the array that is

 * used internally to store the list.  (This class is roughly equivalent to

 * <tt>Vector</tt>, except that it is unsynchronized.)

 *

 * <p>The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>,

 * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant

 * time.  The <tt>add</tt> operation runs in <i>amortized constant time</i>,

 * that is, adding n elements requires O(n) time.  All of the other operations

 * run in linear time (roughly speaking).  The constant factor is low compared

 * to that for the <tt>LinkedList</tt> implementation.

 *

 * <p>Each <tt>ArrayList</tt> instance has a <i>capacity</i>.  The capacity is

 * the size of the array used to store the elements in the list.  It is always

 * at least as large as the list size.  As elements are added to an ArrayList,

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

 * specified beyond the fact that adding an element has constant amortized

 * time cost.

 *

 * <p>An application can increase the capacity of an <tt>ArrayList</tt> instance

 * before adding a large number of elements using the <tt>ensureCapacity</tt>

 * operation.  This may reduce the amount of incremental reallocation.

 *

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

 * If multiple threads access an <tt>ArrayList</tt> instance concurrently,

 * and at least one of the threads modifies the list structurally, it

 * <i>must</i> be synchronized externally.  (A structural modification is

 * any operation that adds or deletes one or more elements, or explicitly

 * resizes the backing array; merely setting the value of an element is not

 * a structural modification.)  This is typically accomplished by

 * synchronizing on some object that naturally encapsulates the list.

 *

 * If no such object exists, the list should be "wrapped" using the

 * {@link Collections#synchronizedList Collections.synchronizedList}

 * method.  This is best done at creation time, to prevent accidental

 * unsynchronized access to the list:<pre>

 *   List list = Collections.synchronizedList(new ArrayList(...));</pre>

 *

 * <p><a name="fail-fast"/>

 * The iterators returned by this class's {@link #iterator() iterator} and

 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:

 * if the list is structurally modified at any time after the iterator is

 * created, in any way except through the iterator's own

 * {@link ListIterator#remove() remove} or

 * {@link ListIterator#add(Object) add} methods, the iterator will throw a

 * {@link ConcurrentModificationException}.  Thus, in the face of

 * concurrent modification, the iterator fails quickly and cleanly, rather

 * than risking arbitrary, non-deterministic behavior at an undetermined

 * time in the future.

 *

 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed

 * as it is, generally speaking, impossible to make any hard guarantees in the

 * presence of unsynchronized concurrent modification.  Fail-fast iterators

 * throw {@code ConcurrentModificationException} on a best-effort basis.

 * Therefore, it would be wrong to write a program that depended on this

 * exception for its correctness:  <i>the fail-fast behavior of iterators

 * should be used only to detect bugs.</i>

 *

 * <p>This class is a member of the

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

 * Java Collections Framework</a>.

 *

 * @author  Josh Bloch

 * @author  Neal Gafter

 * @see     Collection

 * @see     List

 * @see     LinkedList

 * @see     Vector

 * @since   1.2

 */

public class ArrayList<E> extends AbstractList<E>

        implements List<E>, RandomAccess, Cloneable, java.io.Serializable

{

    private static final long serialVersionUID = 8683452581122892189L;

    /**

     * The array buffer into which the elements of the ArrayList are stored.

     * The capacity of the ArrayList is the length of this array buffer.

     */

    private transient Object[] elementData;

    /**

     * The size of the ArrayList (the number of elements it contains).

     *

     * @serial

     */

    private int size;

    /**

     * Constructs an empty list with the specified initial capacity.

     *

     * @param  initialCapacity  the initial capacity of the list

     * @throws IllegalArgumentException if the specified initial capacity

     *         is negative

     */

    public ArrayList(int initialCapacity) {

        super();

        if (initialCapacity < 0)

            throw new IllegalArgumentException("Illegal Capacity: "+

                                               initialCapacity);

        this.elementData = new Object[initialCapacity];

    }

    /**

     * Constructs an empty list with an initial capacity of ten.

     */

    public ArrayList() {

        this(10);

    }

    /**

     * Constructs a list containing the elements of the specified

     * collection, in the order they are returned by the collection's

     * iterator.

     *

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

     * @throws NullPointerException if the specified collection is null

     */

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

        elementData = c.toArray();

        size = elementData.length;

        // c.toArray might (incorrectly) not return Object[] (see 6260652)

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

            elementData = Arrays.copyOf(elementData, size, Object[].class);

    }

    /**

     * Trims the capacity of this <tt>ArrayList</tt> instance to be the

     * list's current size.  An application can use this operation to minimize

     * the storage of an <tt>ArrayList</tt> instance.

     */

    public void trimToSize() {

        modCount++;

        int oldCapacity = elementData.length;

        if (size < oldCapacity) {

            elementData = Arrays.copyOf(elementData, size);

        }

    }

    /**

     * Increases the capacity of this <tt>ArrayList</tt> instance, if

     * necessary, to ensure that it can hold at least the number of elements

     * specified by the minimum capacity argument.

     *

     * @param   minCapacity   the desired minimum capacity

     */

    public void ensureCapacity(int minCapacity) {

        if (minCapacity > 0)

            ensureCapacityInternal(minCapacity);

    }

    private void ensureCapacityInternal(int minCapacity) {

        modCount++;

        // overflow-conscious code

        if (minCapacity - elementData.length > 0)

            grow(minCapacity);

    }

    /**

     * The maximum size of array to allocate.

     * Some VMs reserve some header words in an array.

     * Attempts to allocate larger arrays may result in

     * OutOfMemoryError: Requested array size exceeds VM limit

     */

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

    /**

     * Increases the capacity to ensure that it can hold at least the

     * number of elements specified by the minimum capacity argument.

     *

     * @param minCapacity the desired minimum capacity

     */

    private void grow(int minCapacity) {

        // overflow-conscious code

        int oldCapacity = elementData.length;

        int newCapacity = oldCapacity + (oldCapacity >> 1);

        if (newCapacity - minCapacity < 0)

            newCapacity = minCapacity;

        if (newCapacity - MAX_ARRAY_SIZE > 0)

            newCapacity = hugeCapacity(minCapacity);

        // minCapacity is usually close to size, so this is a win:

        elementData = Arrays.copyOf(elementData, newCapacity);

    }

    private static int hugeCapacity(int minCapacity) {

        if (minCapacity < 0) // overflow

            throw new OutOfMemoryError();

        return (minCapacity > MAX_ARRAY_SIZE) ?

            Integer.MAX_VALUE :

            MAX_ARRAY_SIZE;

    }

    /**

     * Returns the number of elements in this list.

     *

     * @return the number of elements in this list

     */

    public int size() {

        return size;

    }

    /**

     * Returns <tt>true</tt> if this list contains no elements.

     *

     * @return <tt>true</tt> if this list contains no elements

     */

    public boolean isEmpty() {

        return size == 0;

    }

    /**

     * Returns <tt>true</tt> if this list contains the specified element.

     * More formally, returns <tt>true</tt> if and only if this list contains

     * at least one element <tt>e</tt> such that

     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.

     *

     * @param o element whose presence in this list is to be tested

     * @return <tt>true</tt> if this list contains the specified element

     */

    public boolean contains(Object o) {

        return indexOf(o) >= 0;

    }

    /**

     * Returns the index of the first occurrence of the specified element

     * in this list, or -1 if this list does not contain the element.

     * More formally, returns the lowest index <tt>i</tt> such that

     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,

     * or -1 if there is no such index.

     */

    public int indexOf(Object o) {

        if (o == null) {

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

                if (elementData[i]==null)

                    return i;

        } else {

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

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

                    return i;

        }

        return -1;

    }

    /**

     * Returns the index of the last occurrence of the specified element

     * in this list, or -1 if this list does not contain the element.

     * More formally, returns the highest index <tt>i</tt> such that

     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,

     * or -1 if there is no such index.

     */

    public int lastIndexOf(Object o) {

        if (o == null) {

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

                if (elementData[i]==null)

                    return i;

        } else {

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

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

                    return i;

        }

        return -1;

    }

    /**

     * Returns a shallow copy of this <tt>ArrayList</tt> instance.  (The

     * elements themselves are not copied.)

     *

     * @return a clone of this <tt>ArrayList</tt> instance

     */

    public Object clone() {

        try {

            @SuppressWarnings("unchecked")

                ArrayList<E> v = (ArrayList<E>) super.clone();

            v.elementData = Arrays.copyOf(elementData, size);

            v.modCount = 0;

            return v;

        } 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 of the elements in this list in

     *         proper sequence

     */

    public Object[] toArray() {

        return Arrays.copyOf(elementData, size);

    }

    /**

     * 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 the list fits in the specified array with room to spare

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

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

     * <tt>null</tt>.  (This is useful in determining the length of the

     * list <i>only</i> if the caller knows that the list does not contain

     * any null elements.)

     *

     * @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 the elements of the 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) {

        if (a.length < size)

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

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

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

        if (a.length > size)

            a[size] = null;

        return a;

    }

    // Positional Access Operations

    @SuppressWarnings("unchecked")

    E elementData(int index) {

        return (E) elementData[index];

    }

    /**

     * Returns the element at the specified position in this list.

     *

     * @param  index index of the element to return

     * @return the element at the specified position in this list

     * @throws IndexOutOfBoundsException {@inheritDoc}

     */

    public E get(int index) {

        rangeCheck(index);

        return elementData(index);

    }

    /**

     * Replaces the element at the specified position in this list with

     * the specified element.

     *

     * @param index index of the element to replace

     * @param element element to be stored at the specified position

     * @return the element previously at the specified position

     * @throws IndexOutOfBoundsException {@inheritDoc}

     */

    public E set(int index, E element) {

        rangeCheck(index);

        E oldValue = elementData(index);

        elementData[index] = element;

        return oldValue;

    }

    /**

     * Appends the specified element to the end of this list.

     *

     * @param e element to be appended to this list

     * @return <tt>true</tt> (as specified by {@link Collection#add})

     */

    public boolean add(E e) {

        ensureCapacityInternal(size + 1);  // Increments modCount!!

        elementData[size++] = e;

        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).

     *

     * @param index index at which the specified element is to be inserted

     * @param element element to be inserted

     * @throws IndexOutOfBoundsException {@inheritDoc}

     */

    public void add(int index, E element) {

        rangeCheckForAdd(index);

        ensureCapacityInternal(size + 1);  // Increments modCount!!

        System.arraycopy(elementData, index, elementData, index + 1,

                         size - index);

        elementData[index] = element;

        size++;

    }

    /**

     * Removes the element at the specified position in this list.

     * Shifts any subsequent elements to the left (subtracts one from their

     * indices).

     *

     * @param index the index of the element to be removed

     * @return the element that was removed from the list

     * @throws IndexOutOfBoundsException {@inheritDoc}

     */

    public E remove(int index) {

        rangeCheck(index);

        modCount++;

        E oldValue = elementData(index);

        int numMoved = size - index - 1;

        if (numMoved > 0)

            System.arraycopy(elementData, index+1, elementData, index,

                             numMoved);

        elementData[--size] = null; // Let gc do its work

        return oldValue;

    }

    /**

     * Removes the first occurrence of the specified element from this list,

     * if it is present.  If the list does not contain the element, it is

     * unchanged.  More formally, removes the element with the lowest index

     * <tt>i</tt> such that

     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>

     * (if such an element exists).  Returns <tt>true</tt> 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 <tt>true</tt> if this list contained the specified element

     */

    public boolean remove(Object o) {

        if (o == null) {

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

                if (elementData[index] == null) {

                    fastRemove(index);

                    return true;

                }

        } else {

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

                if (o.equals(elementData[index])) {

                    fastRemove(index);

                    return true;

                }

        }

        return false;

    }

    /*

     * Private remove method that skips bounds checking and does not

     * return the value removed.

     */

    private void fastRemove(int index) {

        modCount++;

        int numMoved = size - index - 1;

        if (numMoved > 0)

            System.arraycopy(elementData, index+1, elementData, index,

                             numMoved);

        elementData[--size] = null; // Let gc do its work

    }

    /**

     * Removes all of the elements from this list.  The list will

     * be empty after this call returns.

     */

    public void clear() {

        modCount++;

        // Let gc do its work

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

            elementData[i] = null;

        size = 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.  The behavior of this operation is

     * undefined if the specified collection is modified while the operation

     * is in progress.  (This implies that the behavior of this call is

     * undefined if the specified collection is this list, and this

     * list is nonempty.)

     *

     * @param c collection containing elements to be added to this list

     * @return <tt>true</tt> if this list changed as a result of the call

     * @throws NullPointerException if the specified collection is null

     */

    public boolean addAll(Collection<? extends E> c) {

        Object[] a = c.toArray();

        int numNew = a.length;

        ensureCapacityInternal(size + numNew);  // Increments modCount

        System.arraycopy(a, 0, elementData, size, numNew);

        size += numNew;

        return numNew != 0;

    }

    /**

     * 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 the 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 <tt>true</tt> if this list changed as a result of the call

     * @throws IndexOutOfBoundsException {@inheritDoc}

     * @throws NullPointerException if the specified collection is null

     */

    public boolean addAll(int index, Collection<? extends E> c) {

        rangeCheckForAdd(index);

        Object[] a = c.toArray();

        int numNew = a.length;

        ensureCapacityInternal(size + numNew);  // Increments modCount

        int numMoved = size - index;

        if (numMoved > 0)

            System.arraycopy(elementData, index, elementData, index + numNew,

                             numMoved);

        System.arraycopy(a, 0, elementData, index, numNew);

        size += numNew;

        return numNew != 0;

    }

    /**

     * 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.)

     *

     * @throws IndexOutOfBoundsException if {@code fromIndex} or

     *         {@code toIndex} is out of range

     *         ({@code fromIndex < 0 ||

     *          fromIndex >= size() ||

     *          toIndex > size() ||

     *          toIndex < fromIndex})

     */

    protected void removeRange(int fromIndex, int toIndex) {

        modCount++;

        int numMoved = size - toIndex;

        System.arraycopy(elementData, toIndex, elementData, fromIndex,

                         numMoved);

        // Let gc do its work

        int newSize = size - (toIndex-fromIndex);

        while (size != newSize)

            elementData[--size] = null;

    }

    /**

     * Checks if the given index is in range.  If not, throws an appropriate

     * runtime exception.  This method does *not* check if the index is

     * negative: It is always used immediately prior to an array access,

     * which throws an ArrayIndexOutOfBoundsException if index is negative.

     */

    private void rangeCheck(int index) {

        if (index >= size)

            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));

    }

    /**

     * A version of rangeCheck used by add and addAll.

     */

    private void rangeCheckForAdd(int index) {

        if (index > size || index < 0)

            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));

    }

    /**

     * Constructs an IndexOutOfBoundsException detail message.

     * Of the many possible refactorings of the error handling code,

     * this "outlining" performs best with both server and client VMs.

     */

    private String outOfBoundsMsg(int index) {

        return "Index: "+index+", Size: "+size;

    }

    /**

     * Removes from this list all of its elements that are contained in the

     * specified collection.

     *

     * @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="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="Collection.html#optional-restrictions">optional</a>),

     *         or if the specified collection is null

     * @see Collection#contains(Object)

     */

    public boolean removeAll(Collection<?> c) {

        return batchRemove(c, false);

    }

    /**

     * 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="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="Collection.html#optional-restrictions">optional</a>),

     *         or if the specified collection is null

     * @see Collection#contains(Object)

     */

    public boolean retainAll(Collection<?> c) {

        return batchRemove(c, true);

    }

    private boolean batchRemove(Collection<?> c, boolean complement) {

        final Object[] elementData = this.elementData;

        int r = 0, w = 0;

        boolean modified = false;

        try {

            for (; r < size; r++)

                if (c.contains(elementData[r]) == complement)

                    elementData[w++] = elementData[r];

        } finally {

            // Preserve behavioral compatibility with AbstractCollection,

            // even if c.contains() throws.

            if (r != size) {

                System.arraycopy(elementData, r,

                                 elementData, w,

                                 size - r);

                w += size - r;

            }

            if (w != size) {

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

                    elementData[i] = null;

                modCount += size - w;

                size = w;

                modified = true;

            }

        }

        return modified;

    }

    /**

     * Returns a list iterator over the elements in this list (in proper

     * sequence), starting at the specified position in the list.

     * The specified index indicates the first element that would be

     * returned by an initial call to {@link ListIterator#next next}.

     * An initial call to {@link ListIterator#previous previous} would

     * return the element with the specified index minus one.

     *

     * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.

     *

     * @throws IndexOutOfBoundsException {@inheritDoc}

     */

    public ListIterator<E> listIterator(int index) {

        if (index < 0 || index > size)

            throw new IndexOutOfBoundsException("Index: "+index);

        return new ListItr(index);

    }

    /**

     * Returns a list iterator over the elements in this list (in proper

     * sequence).

     *

     * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.

     *

     * @see #listIterator(int)

     */

    public ListIterator<E> listIterator() {

        return new ListItr(0);

    }

    /**

     * Returns an iterator over the elements in this list in proper sequence.

     *

     * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.

     *

     * @return an iterator over the elements in this list in proper sequence

     */

    public Iterator<E> iterator() {

        return new Itr();

    }

    /**

     * An optimized version of AbstractList.Itr

     */

    private class Itr implements Iterator<E> {

        int cursor;       // index of next element to return

        int lastRet = -1; // index of last element returned; -1 if no such

        int expectedModCount = modCount;

        public boolean hasNext() {

            return cursor != size;

        }

        @SuppressWarnings("unchecked")

        public E next() {

            checkForComodification();

            int i = cursor;

            if (i >= size)

                throw new NoSuchElementException();

            Object[] elementData = ArrayList.this.elementData;

            if (i >= elementData.length)

                throw new ConcurrentModificationException();

            cursor = i + 1;

            return (E) elementData[lastRet = i];

        }

        public void remove() {

            if (lastRet < 0)

                throw new IllegalStateException();

            checkForComodification();

            try {

                ArrayList.this.remove(lastRet);

                cursor = lastRet;

                lastRet = -1;

                expectedModCount = modCount;

            } catch (IndexOutOfBoundsException ex) {

                throw new ConcurrentModificationException();

            }

        }

        final void checkForComodification() {

            if (modCount != expectedModCount)

                throw new ConcurrentModificationException();

        }

    }

    /**

     * An optimized version of AbstractList.ListItr

     */

    private class ListItr extends Itr implements ListIterator<E> {

        ListItr(int index) {

            super();

            cursor = index;

        }

        public boolean hasPrevious() {

            return cursor != 0;

        }

        public int nextIndex() {

            return cursor;

        }

        public int previousIndex() {

            return cursor - 1;

        }

        @SuppressWarnings("unchecked")

        public E previous() {

            checkForComodification();

            int i = cursor - 1;

            if (i < 0)

                throw new NoSuchElementException();

            Object[] elementData = ArrayList.this.elementData;

            if (i >= elementData.length)

                throw new ConcurrentModificationException();

            cursor = i;

            return (E) elementData[lastRet = i];

        }

        public void set(E e) {

            if (lastRet < 0)

                throw new IllegalStateException();

            checkForComodification();

            try {

                ArrayList.this.set(lastRet, e);

            } catch (IndexOutOfBoundsException ex) {

                throw new ConcurrentModificationException();

            }

        }

        public void add(E e) {

            checkForComodification();

            try {

                int i = cursor;

                ArrayList.this.add(i, e);

                cursor = i + 1;

                lastRet = -1;

                expectedModCount = modCount;

            } catch (IndexOutOfBoundsException ex) {

                throw new ConcurrentModificationException();

            }

        }

    }

    /**

     * Returns a view of the portion of this list between the specified

     * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.  (If

     * {@code fromIndex} and {@code toIndex} are equal, the returned list is

     * empty.)  The returned list is backed by this list, so non-structural

     * changes in the returned list are reflected in this list, and vice-versa.

     * The returned list supports all of the optional list operations.

     *

     * <p>This method eliminates the need for explicit range operations (of

     * the sort that commonly exist for arrays).  Any operation that expects

     * a list can be used as a range operation by passing a subList view

     * instead of a whole list.  For example, the following idiom

     * removes a range of elements from a list:

     * <pre>

     *      list.subList(from, to).clear();

     * </pre>

     * Similar idioms may be constructed for {@link #indexOf(Object)} and

     * {@link #lastIndexOf(Object)}, and all of the algorithms in the

     * {@link Collections} class can be applied to a subList.

     *

     * <p>The semantics of the list returned by this method become undefined if

     * the backing list (i.e., this list) is <i>structurally modified</i> in

     * any way other than via the returned list.  (Structural modifications are

     * those that change the size of this list, or otherwise perturb it in such

     * a fashion that iterations in progress may yield incorrect results.)

     *

     * @throws IndexOutOfBoundsException {@inheritDoc}

     * @throws IllegalArgumentException {@inheritDoc}

     */

    public List<E> subList(int fromIndex, int toIndex) {

        subListRangeCheck(fromIndex, toIndex, size);

        return new SubList(this, 0, 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 + ")");

    }

    private class SubList extends AbstractList<E> implements RandomAccess {

        private final AbstractList<E> parent;

        private final int parentOffset;

        private final int offset;

        int size;

        SubList(AbstractList<E> parent,

                int offset, int fromIndex, int toIndex) {

            this.parent = parent;

            this.parentOffset = fromIndex;

            this.offset = offset + fromIndex;

            this.size = toIndex - fromIndex;

            this.modCount = ArrayList.this.modCount;

        }

        public E set(int index, E e) {

            rangeCheck(index);

            checkForComodification();

            E oldValue = ArrayList.this.elementData(offset + index);

            ArrayList.this.elementData[offset + index] = e;

            return oldValue;

        }

        public E get(int index) {

            rangeCheck(index);

            checkForComodification();

            return ArrayList.this.elementData(offset + index);

        }

        public int size() {

            checkForComodification();

            return this.size;

        }

        public void add(int index, E e) {

            rangeCheckForAdd(index);

            checkForComodification();

            parent.add(parentOffset + index, e);

            this.modCount = parent.modCount;

            this.size++;

        }

        public E remove(int index) {

            rangeCheck(index);

            checkForComodification();

            E result = parent.remove(parentOffset + index);

            this.modCount = parent.modCount;

            this.size--;

            return result;

        }

        protected void removeRange(int fromIndex, int toIndex) {

            checkForComodification();

            parent.removeRange(parentOffset + fromIndex,

                               parentOffset + toIndex);

            this.modCount = parent.modCount;

            this.size -= toIndex - fromIndex;

        }

        public boolean addAll(Collection<? extends E> c) {

            return addAll(this.size, c);

        }

        public boolean addAll(int index, Collection<? extends E> c) {

            rangeCheckForAdd(index);

            int cSize = c.size();

            if (cSize==0)

                return false;

            checkForComodification();

            parent.addAll(parentOffset + index, c);

            this.modCount = parent.modCount;

            this.size += cSize;

            return true;

        }

        public Iterator<E> iterator() {

            return listIterator();

        }

        public ListIterator<E> listIterator(final int index) {

            checkForComodification();

            rangeCheckForAdd(index);

            final int offset = this.offset;

            return new ListIterator<E>() {

                int cursor = index;

                int lastRet = -1;

                int expectedModCount = ArrayList.this.modCount;

                public boolean hasNext() {

                    return cursor != SubList.this.size;

                }

                @SuppressWarnings("unchecked")

                public E next() {

                    checkForComodification();

                    int i = cursor;

                    if (i >= SubList.this.size)

                        throw new NoSuchElementException();

                    Object[] elementData = ArrayList.this.elementData;

                    if (offset + i >= elementData.length)

                        throw new ConcurrentModificationException();

                    cursor = i + 1;

                    return (E) elementData[offset + (lastRet = i)];

                }

                public boolean hasPrevious() {

                    return cursor != 0;

                }