/*
 
* Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
 
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 
*
 
* This code is free software; you can redistribute it and/or modify it
 
* under the terms of the GNU General Public License version 2 only, as
 
* published by the Free Software Foundation.
  
Oracle designates this
 
* particular file as subject to the "Classpath" exception as provided
 
* by Oracle in the LICENSE file that accompanied this code.
 
*
 
* This code is distributed in the hope that it will be useful, but WITHOUT
 
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 
* FITNESS FOR A PARTICULAR PURPOSE.
  
See the GNU General Public License
 
* version 2 for more details (a copy is included in the LICENSE file that
 
* accompanied this code).
 
*
 
* You should have received a copy of the GNU General Public License version
 
* 2 along with this work; if not, write to the Free Software Foundation,
 
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 
*
 
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 
* or visit www.oracle.com if you need additional information or have any
 
* questions.
 
*/

package java.util;

import java.util.function.Consumer;
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
  
initialCapacitythe 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) {
        
elementData = c.toArray();
        
if ((size = elementData.length) != 0) {
            
// c.toArray might (incorrectly) not return Object[] (see 6260652)
            
if (elementData.getClass() != Object[].class)
                
elementData = Arrays.copyOf(elementData, size, Object[].class);
        
} else {
            
// replace with empty array.
            
this.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
   
minCapacitythe 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.)
     
*
     
* @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;
                
}

                
@SuppressWarnings("unchecked")
                
public E previous() {
                    
checkForComodification();
                    
int i = cursor - 1;
                    
if (i < 0)
                        
throw new NoSuchElementException();
                    
Object[] elementData = ArrayList.this.elementData;
                    
if (offset + i >= elementData.length)
                        
throw new ConcurrentModificationException();
                    
cursor = i;
                    
return (E) elementData[offset + (lastRet = i)];
                
}

                
@SuppressWarnings("unchecked")
                
public void forEachRemaining(Consumer<? super E> consumer) {
                    
Objects.requireNonNull(consumer);
                    
final int size = SubList.this.size;
                    
int i = cursor;
                    
if (i >= size) {
                        
return;
                    
}
                    
final Object[] elementData = ArrayList.this.elementData;
                    
if (offset + i >= elementData.length) {
                        
throw new ConcurrentModificationException();
                    
}
                    
while (i != size && modCount == expectedModCount) {
                        
consumer.accept((E) elementData[offset + (i++)]);
                    
}
                    
// update once at end of iteration to reduce heap write traffic
                    
lastRet = cursor = i;
                    
checkForComodification();
                
}

                
public int nextIndex() {
                    
return cursor;
                
}

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

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

                    
try {
                        
SubList.this.remove(lastRet);
                        
cursor = lastRet;
                        
lastRet = -1;
                        
expectedModCount = ArrayList.this.modCount;
                    
} catch (IndexOutOfBoundsException ex) {
                        
throw new ConcurrentModificationException();
                    
}
                
}

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

                    
try {
                        
ArrayList.this.set(offset + lastRet, e);
                    
} catch (IndexOutOfBoundsException ex) {
                        
throw new ConcurrentModificationException();
                    
}
                
}

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

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

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

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

        
private void rangeCheck(int index) {
            
if (index < 0 || index >= this.size)
                
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
        
}

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

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

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

        
public Spliterator<E> spliterator() {
            
checkForComodification();
            
return new ArrayListSpliterator<E>(ArrayList.this, offset,
                                               
offset + this.size, this.modCount);
        
}
    
}

    
@Override
    
public void forEach(Consumer<? super E> action) {
        
Objects.requireNonNull(action);
        
final int expectedModCount = modCount;
        
@SuppressWarnings("unchecked")
        
final E[] elementData = (E[]) this.elementData;
        
final int size = this.size;
        
for (int i=0; modCount == expectedModCount && i < size; i++) {
            
action.accept(elementData[i]);
        
}
        
if (modCount != expectedModCount) {
            
throw new ConcurrentModificationException();
        
}
    
}

    
/**
     
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
     
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
     
* list.
     
*
     
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
     
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
     
* Overriding implementations should document the reporting of additional
     
* characteristic values.
     
*
     
* @return a {@code Spliterator} over the elements in this list
     
* @since 1.8
     
*/

    
@Override
    
public Spliterator<E> spliterator() {
        
return new ArrayListSpliterator<>(this, 0, -1, 0);
    
}

    
/** Index-based split-by-two, lazily initialized Spliterator */
    
static final class ArrayListSpliterator<E> implements Spliterator<E> {

        
/*
         
* If ArrayLists were immutable, or structurally immutable (no
         
* adds, removes, etc), we could implement their spliterators
         
* with Arrays.spliterator. Instead we detect as much
         
* interference during traversal as practical without
         
* sacrificing much performance. We rely primarily on
         
* modCounts. These are not guaranteed to detect concurrency
         
* violations, and are sometimes overly conservative about
         
* within-thread interference, but detect enough problems to
         
* be worthwhile in practice. To carry this out, we (1) lazily
         
* initialize fence and expectedModCount until the latest
         
* point that we need to commit to the state we are checking
         
* against; thus improving precision.
  
(This doesn't apply to
         
* SubLists, that create spliterators with current non-lazy
         
* values).
  
(2) We perform only a single
         
* ConcurrentModificationException check at the end of forEach
         
* (the most performance-sensitive method). When using forEach
         
* (as opposed to iterators), we can normally only detect
         
* interference after actions, not before. Further
         
* CME-triggering checks apply to all other possible
         
* violations of assumptions for example null or too-small
         
* elementData array given its size(), that could only have
         
* occurred due to interference.
  
This allows the inner loop
         
* of forEach to run without any further checks, and
         
* simplifies lambda-resolution. While this does entail a
         
* number of checks, note that in the common case of
         
* list.stream().forEach(a), no checks or other computation
         
* occur anywhere other than inside forEach itself.
  
The other
         
* less-often-used methods cannot take advantage of most of
         
* these streamlinings.
         
*/


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

        
/** Create new spliterator covering the given
  
range */

        
ArrayListSpliterator(ArrayList<E> list, int origin, int fence,
                             
int expectedModCount) {
            
this.list = list; // OK if null unless traversed
            
this.index = origin;
            
this.fence = fence;
            
this.expectedModCount = expectedModCount;
        
}

        
private int getFence() { // initialize fence to size on first use
            
int hi; // (a specialized variant appears in method forEach)
            
ArrayList<E> lst;
            
if ((hi = fence) < 0) {
                
if ((lst = list) == null)
                    
hi = fence = 0;
                
else {
                    
expectedModCount = lst.modCount;
                    
hi = fence = lst.size;
                
}
            
}
            
return hi;
        
}

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

        
public boolean tryAdvance(Consumer<? super E> action) {
            
if (action == null)
                
throw new NullPointerException();
            
int hi = getFence(), i = index;
            
if (i < hi) {
                
index = i + 1;
                
@SuppressWarnings("unchecked") E e = (E)list.elementData[i];
                
action.accept(e);
                
if (list.modCount != expectedModCount)
                    
throw new ConcurrentModificationException();
                
return true;
            
}
            
return false;
        
}

        
public void forEachRemaining(Consumer<? super E> action) {
            
int i, hi, mc; // hoist accesses and checks from loop
            
ArrayList<E> lst; Object[] a;
            
if (action == null)
                
throw new NullPointerException();
            
if ((lst = list) != null && (a = lst.elementData) != null) {
                
if ((hi = fence) < 0) {
                    
mc = lst.modCount;
                    
hi = lst.size;
                
}
                
else
                    
mc = expectedModCount;
                
if ((i = index) >= 0 && (index = hi) <= a.length) {
                    
for (; i < hi; ++i) {
                        
@SuppressWarnings("unchecked") E e = (E) a[i];
                        
action.accept(e);
                    
}
                    
if (lst.modCount == mc)
                        
return;
                
}
            
}
            
throw new ConcurrentModificationException();
        
}

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

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

    
@Override
    
public boolean removeIf(Predicate<? super E> filter) {
        
Objects.requireNonNull(filter);
        
// figure out which elements are to be removed
        
// any exception thrown from the filter predicate at this stage
        
// will leave the collection unmodified
        
int removeCount = 0;
        
final BitSet removeSet = new BitSet(size);
        
final int expectedModCount = modCount;
        
final int size = this.size;
        
for (int i=0; modCount == expectedModCount && i < size; i++) {
            
@SuppressWarnings("unchecked")
            
final E element = (E) elementData[i];
            
if (filter.test(element)) {
                
removeSet.set(i);
                
removeCount++;
            
}
        
}
        
if (modCount != expectedModCount) {
            
throw new ConcurrentModificationException();
        
}

        
// shift surviving elements left over the spaces left by removed elements
        
final boolean anyToRemove = removeCount > 0;
        
if (anyToRemove) {
            
final int newSize = size - removeCount;
            
for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {
                
i = removeSet.nextClearBit(i);
                
elementData[j] = elementData[i];
            
}
            
for (int k=newSize; k < size; k++) {
                
elementData[k] = null;
  
// Let gc do its work
            
}
            
this.size = newSize;
            
if (modCount != expectedModCount) {
                
throw new ConcurrentModificationException();
            
}
            
modCount++;
        
}

        
return anyToRemove;
    
}

    
@Override
    
@SuppressWarnings("unchecked")
    
public void replaceAll(UnaryOperator<E> operator) {
        
Objects.requireNonNull(operator);
        
final int expectedModCount = modCount;
        
final int size = this.size;
        
for (int i=0; modCount == expectedModCount && i < size; i++) {
            
elementData[i] = operator.apply((E) elementData[i]);
        
}
        
if (modCount != expectedModCount) {
            
throw new ConcurrentModificationException();
        
}
        
modCount++;
    
}

    
@Override
    
@SuppressWarnings("unchecked")
    
public void sort(Comparator<? super E> c) {
        
final int expectedModCount = modCount;
        
Arrays.sort((E[]) elementData, 0, size, c);
        
if (modCount != expectedModCount) {
            
throw new ConcurrentModificationException();
        
}
        
modCount++;
    
}
}