/*

* Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.

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

*

*

*

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*

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*

*

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*

*/

package java.util;

import java.util.function.Consumer;

import java.util.function.Predicate;

import java.util.function.UnaryOperator;

import sun.misc.SharedSecrets;

/**

* 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>:</a>

* 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;

/**

* Default initial capacity.

*/

private static final int DEFAULT_CAPACITY = 10;

/**

* Shared empty array instance used for empty instances.

*/

private static final Object[] EMPTY_ELEMENTDATA = {};

/**

* Shared empty array instance used for default sized empty instances. We

* distinguish this from EMPTY_ELEMENTDATA to know how much to inflate when

* first element is added.

*/

private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};

/**

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

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

* empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA

* will be expanded to DEFAULT_CAPACITY when the first element is added.

*/

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

/**

* 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) {

if (initialCapacity > 0) {

this.elementData = new Object[initialCapacity];

} else if (initialCapacity == 0) {

this.elementData = EMPTY_ELEMENTDATA;

} else {

throw new IllegalArgumentException("Illegal Capacity: "+

initialCapacity);

}

}

/**

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

*/

public ArrayList() {

this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;

}

/**

* 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) {

Object[] a = c.toArray();

if ((size = a.length) != 0) {

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

elementData = a;

} else {

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

}

} else {

// replace with empty array.

elementData = EMPTY_ELEMENTDATA;

}

}

/**

* 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++;

if (size < elementData.length) {

elementData = (size == 0)

? EMPTY_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) {

int minExpand = (elementData != DEFAULTCAPACITY_EMPTY_ELEMENTDATA)

// any size if not default element table

? 0

// larger than default for default empty table. It's already

// supposed to be at default size.

: DEFAULT_CAPACITY;

if (minCapacity > minExpand) {

ensureExplicitCapacity(minCapacity);

}

}

private static int calculateCapacity(Object[] elementData, int minCapacity) {

if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) {

return Math.max(DEFAULT_CAPACITY, minCapacity);

}

return minCapacity;

}

private void ensureCapacityInternal(int minCapacity) {

ensureExplicitCapacity(calculateCapacity(elementData, minCapacity));

}

private void ensureExplicitCapacity(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 {

ArrayList<?> v = (ArrayList<?>) 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(e);

}

}

/**

* 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; // clear to 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; // clear to 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++;

// clear to 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);

// clear to let GC do its work

int newSize = size - (toIndex-fromIndex);

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

elementData[i] = null;

}

size = newSize;

}

/**

* 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) {

Objects.requireNonNull(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) {

Objects.requireNonNull(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) {

// clear to let GC do its work

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

elementData[i] = null;

modCount += size - w;

size = w;

modified = true;

}

}

return modified;

}

/**

* Save the state of the <tt>ArrayList</tt> instance to a stream (that

* is, serialize it).

*

* @serialData The length of the array backing the <tt>ArrayList</tt>

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

* (each an <tt>Object</tt>) in the proper order.

*/

private void writeObject(java.io.ObjectOutputStream s)

throws java.io.IOException{

// Write out element count, and any hidden stuff

int expectedModCount = modCount;

s.defaultWriteObject();

// Write out size as capacity for behavioural compatibility with clone()

s.writeInt(size);

// Write out all elements in the proper order.

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

s.writeObject(elementData[i]);

}

if (modCount != expectedModCount) {

throw new ConcurrentModificationException();

}

}

/**

* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,

* deserialize it).

*/

private void readObject(java.io.ObjectInputStream s)

throws java.io.IOException, ClassNotFoundException {

elementData = EMPTY_ELEMENTDATA;

// Read in size, and any hidden stuff

s.defaultReadObject();

// Read in capacity

s.readInt(); // ignored

if (size > 0) {

// be like clone(), allocate array based upon size not capacity

int capacity = calculateCapacity(elementData, size);

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

ensureCapacityInternal(size);

Object[] a = elementData;

// Read in all elements in the proper order.

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

a[i] = s.readObject();

}

}

}

/**

* 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;

Itr() {}

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();

}

}

@Override

@SuppressWarnings("unchecked")

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

Objects.requireNonNull(consumer);

final int size = ArrayList.this.size;

int i = cursor;

if (i >= size) {

return;

}

final Object[] elementData = ArrayList.this.elementData;

if (i >= elementData.length) {

throw new ConcurrentModificationException();

}

while (i != size && modCount == expectedModCount) {

consumer.accept((E) elementData[i++]);

}

// update once at end of iteration to reduce heap write traffic

cursor = i;

lastRet = i - 1;

checkForComodification();

}

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.)