/*
 
* Copyright (c) 1997, 2012, 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;

/**
 
* This class provides a skeletal implementation of the {@link List}
 
* interface to minimize the effort required to implement this interface
 
* backed by a "random access" data store (such as an array).
  
For sequential
 
* access data (such as a linked list), {@link AbstractSequentialList} should
 
* be used in preference to this class.
 
*
 
* <p>To implement an unmodifiable list, the programmer needs only to extend
 
* this class and provide implementations for the {@link #get(int)} and
 
* {@link List#size() size()} methods.
 
*
 
* <p>To implement a modifiable list, the programmer must additionally
 
* override the {@link #set(int, Object) set(int, E)} method (which otherwise
 
* throws an {@code UnsupportedOperationException}).
  
If the list is
 
* variable-size the programmer must additionally override the
 
* {@link #add(int, Object) add(int, E)} and {@link #remove(int)} methods.
 
*
 
* <p>The programmer should generally provide a void (no argument) and collection
 
* constructor, as per the recommendation in the {@link Collection} interface
 
* specification.
 
*
 
* <p>Unlike the other abstract collection implementations, the programmer does
 
* <i>not</i> have to provide an iterator implementation; the iterator and
 
* list iterator are implemented by this class, on top of the "random access"
 
* methods:
 
* {@link #get(int)},
 
* {@link #set(int, Object) set(int, E)},
 
* {@link #add(int, Object) add(int, E)} and
 
* {@link #remove(int)}.
 
*
 
* <p>The documentation for each non-abstract method in this class describes its
 
* implementation in detail.
  
Each of these methods may be overridden if the
 
* collection being implemented admits a more efficient implementation.
 
*
 
* <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
 
* @since 1.2
 
*/


public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E> {
    
/**
     
* Sole constructor.
  
(For invocation by subclass constructors, typically
     
* implicit.)
     
*/

    
protected AbstractList() {
    
}

    
/**
     
* Appends the specified element to the end of this list (optional
     
* operation).
     
*
     
* <p>Lists that support this operation may place limitations on what
     
* elements may be added to this list.
  
In particular, some
     
* lists will refuse to add null elements, and others will impose
     
* restrictions on the type of elements that may be added.
  
List
     
* classes should clearly specify in their documentation any restrictions
     
* on what elements may be added.
     
*
     
* <p>This implementation calls {@code add(size(), e)}.
     
*
     
* <p>Note that this implementation throws an
     
* {@code UnsupportedOperationException} unless
     
* {@link #add(int, Object) add(int, E)} is overridden.
     
*
     
* @param e element to be appended to this list
     
* @return {@code true} (as specified by {@link Collection#add})
     
* @throws UnsupportedOperationException if the {@code add} operation
     
*
         
is not supported by this list
     
* @throws ClassCastException if the class of the specified element
     
*
         
prevents it from being added to this list
     
* @throws NullPointerException if the specified element is null and this
     
*
         
list does not permit null elements
     
* @throws IllegalArgumentException if some property of this element
     
*
         
prevents it from being added to this list
     
*/

    
public boolean add(E e) {
        
add(size(), e);
        
return true;
    
}

    
/**
     
* {@inheritDoc}
     
*
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
*/
    
abstract public E get(int index);

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation always throws an
     
* {@code UnsupportedOperationException}.
     
*
     
* @throws UnsupportedOperationException {@inheritDoc}
     
* @throws ClassCastException
            
{@inheritDoc}
     
* @throws NullPointerException
          
{@inheritDoc}
     
* @throws IllegalArgumentException
      
{@inheritDoc}
     
* @throws IndexOutOfBoundsException{@inheritDoc}
     
*/

    
public E set(int index, E element) {
        
throw new UnsupportedOperationException();
    
}

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation always throws an
     
* {@code UnsupportedOperationException}.
     
*
     
* @throws UnsupportedOperationException {@inheritDoc}
     
* @throws ClassCastException
            
{@inheritDoc}
     
* @throws NullPointerException
          
{@inheritDoc}
     
* @throws IllegalArgumentException
      
{@inheritDoc}
     
* @throws IndexOutOfBoundsException{@inheritDoc}
     
*/

    
public void add(int index, E element) {
        
throw new UnsupportedOperationException();
    
}

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation always throws an
     
* {@code UnsupportedOperationException}.
     
*
     
* @throws UnsupportedOperationException {@inheritDoc}
     
* @throws IndexOutOfBoundsException{@inheritDoc}
     
*/

    
public E remove(int index) {
        
throw new UnsupportedOperationException();
    
}


    
// Search Operations

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation first gets a list iterator (with
     
* {@code listIterator()}).
  
Then, it iterates over the list until the
     
* specified element is found or the end of the list is reached.
     
*
     
* @throws ClassCastException
   
{@inheritDoc}
     
* @throws NullPointerException {@inheritDoc}
     
*/

    
public int indexOf(Object o) {
        
ListIterator<E> it = listIterator();
        
if (o==null) {
            
while (it.hasNext())
                
if (it.next()==null)
                    
return it.previousIndex();
        
} else {
            
while (it.hasNext())
                
if (o.equals(it.next()))
                    
return it.previousIndex();
        
}
        
return -1;
    
}

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation first gets a list iterator that points to the end
     
* of the list (with {@code listIterator(size())}).
  
Then, it iterates
     
* backwards over the list until the specified element is found, or the
     
* beginning of the list is reached.
     
*
     
* @throws ClassCastException
   
{@inheritDoc}
     
* @throws NullPointerException {@inheritDoc}
     
*/

    
public int lastIndexOf(Object o) {
        
ListIterator<E> it = listIterator(size());
        
if (o==null) {
            
while (it.hasPrevious())
                
if (it.previous()==null)
                    
return it.nextIndex();
        
} else {
            
while (it.hasPrevious())
                
if (o.equals(it.previous()))
                    
return it.nextIndex();
        
}
        
return -1;
    
}


    
// Bulk Operations

    
/**
     
* Removes all of the elements from this list (optional operation).
     
* The list will be empty after this call returns.
     
*
     
* <p>This implementation calls {@code removeRange(0, size())}.
     
*
     
* <p>Note that this implementation throws an
     
* {@code UnsupportedOperationException} unless {@code remove(int
     
* index)} or {@code removeRange(int fromIndex, int toIndex)} is
     
* overridden.
     
*
     
* @throws UnsupportedOperationException if the {@code clear} operation
     
*
         
is not supported by this list
     
*/

    
public void clear() {
        
removeRange(0, size());
    
}

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation gets an iterator over the specified collection
     
* and iterates over it, inserting the elements obtained from the
     
* iterator into this list at the appropriate position, one at a time,
     
* using {@code add(int, E)}.
     
* Many implementations will override this method for efficiency.
     
*
     
* <p>Note that this implementation throws an
     
* {@code UnsupportedOperationException} unless
     
* {@link #add(int, Object) add(int, E)} is overridden.
     
*
     
* @throws UnsupportedOperationException {@inheritDoc}
     
* @throws ClassCastException
            
{@inheritDoc}
     
* @throws NullPointerException
          
{@inheritDoc}
     
* @throws IllegalArgumentException
      
{@inheritDoc}
     
* @throws IndexOutOfBoundsException{@inheritDoc}
     
*/

    
public boolean addAll(int index, Collection<? extends E> c) {
        
rangeCheckForAdd(index);
        
boolean modified = false;
        
for (E e : c) {
            
add(index++, e);
            
modified = true;
        
}
        
return modified;
    
}


    
// Iterators

    
/**
     
* Returns an iterator over the elements in this list in proper sequence.
     
*
     
* <p>This implementation returns a straightforward implementation of the
     
* iterator interface, relying on the backing list's {@code size()},
     
* {@code get(int)}, and {@code remove(int)} methods.
     
*
     
* <p>Note that the iterator returned by this method will throw an
     
* {@link UnsupportedOperationException} in response to its
     
* {@code remove} method unless the list's {@code remove(int)} method is
     
* overridden.
     
*
     
* <p>This implementation can be made to throw runtime exceptions in the
     
* face of concurrent modification, as described in the specification
     
* for the (protected)
 
 
field.
     
*
     
* @return an iterator over the elements in this list in proper sequence
     
*/

    
public Iterator<E> iterator() {
        
return new Itr();
    
}

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation returns {@code listIterator(0)}.
     
*
     
* @see #listIterator(int)
     
*/

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

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation returns a straightforward implementation of the
     
* {@code ListIterator} interface that extends the implementation of the
     
* {@code Iterator} interface returned by the {@code iterator()} method.
     
* The {@code ListIterator} implementation relies on the backing list's
     
* {@code get(int)}, {@code set(int, E)}, {@code add(int, E)}
     
* and {@code remove(int)} methods.
     
*
     
* <p>Note that the list iterator returned by this implementation will
     
* throw an {@link UnsupportedOperationException} in response to its
     
* {@code remove}, {@code set} and {@code add} methods unless the
     
* list's {@code remove(int)}, {@code set(int, E)}, and
     
* {@code add(int, E)} methods are overridden.
     
*
     
* <p>This implementation can be made to throw runtime exceptions in the
     
* face of concurrent modification, as described in the specification for
     
* the (protected)
 
 
field.
     
*
     
* @throws IndexOutOfBoundsException {@inheritDoc}
     
*/

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

        
return new ListItr(index);
    
}

    
private class Itr implements Iterator<E> {
        
/**
         
* Index of element to be returned by subsequent call to next.
         
*/

        
int cursor = 0;

        
/**
         
* Index of element returned by most recent call to next or
         
* previous.
  
Reset to -1 if this element is deleted by a call
         
* to remove.
         
*/

        
int lastRet = -1;

        
/**
         
* The modCount value that the iterator believes that the backing
         
* List should have.
  
If this expectation is violated, the iterator
         
* has detected concurrent modification.
         
*/

        
int expectedModCount = modCount;

        
public boolean hasNext() {
            
return cursor != size();
        
}

        
public E next() {
            
checkForComodification();
            
try {
                
int i = cursor;
                
E next = get(i);
                
lastRet = i;
                
cursor = i + 1;
                
return next;
            
} catch (IndexOutOfBoundsException e) {
                
checkForComodification();
                
throw new NoSuchElementException();
            
}
        
}

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

            
try {
                
AbstractList.this.remove(lastRet);
                
if (lastRet < cursor)
                    
cursor--;
                
lastRet = -1;
                
expectedModCount = modCount;
            
} catch (IndexOutOfBoundsException e) {
                
throw new ConcurrentModificationException();
            
}
        
}

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

    
private class ListItr extends Itr implements ListIterator<E> {
        
ListItr(int index) {
            
cursor = index;
        
}

        
public boolean hasPrevious() {
            
return cursor != 0;
        
}

        
public E previous() {
            
checkForComodification();
            
try {
                
int i = cursor - 1;
                
E previous = get(i);
                
lastRet = cursor = i;
                
return previous;
            
} catch (IndexOutOfBoundsException e) {
                
checkForComodification();
                
throw new NoSuchElementException();
            
}
        
}

        
public int nextIndex() {
            
return cursor;
        
}

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

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

            
try {
                
AbstractList.this.set(lastRet, e);
                
expectedModCount = modCount;
            
} catch (IndexOutOfBoundsException ex) {
                
throw new ConcurrentModificationException();
            
}
        
}

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

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

    
/**
     
* {@inheritDoc}
     
*
     
* <p>This implementation returns a list that subclasses
     
* {@code AbstractList}.
  
The subclass stores, in private fields, the
     
* offset of the subList within the backing list, the size of the subList
     
* (which can change over its lifetime), and the expected
     
* {@code modCount} value of the backing list.
  
There are two variants
     
* of the subclass, one of which implements {@code RandomAccess}.
     
* If this list implements {@code RandomAccess} the returned list will
     
* be an instance of the subclass that implements {@code RandomAccess}.
     
*
     
* <p>The subclass's {@code set(int, E)}, {@code get(int)},
     
* {@code add(int, E)}, {@code remove(int)}, {@code addAll(int,
     
* Collection)} and {@code removeRange(int, int)} methods all
     
* delegate to the corresponding methods on the backing abstract list,
     
* after bounds-checking the index and adjusting for the offset.
  
The
     
* {@code addAll(Collection c)} method merely returns {@code addAll(size,
     
* c)}.
     
*
     
* <p>The {@code listIterator(int)} method returns a "wrapper object"
     
* over a list iterator on the backing list, which is created with the
     
* corresponding method on the backing list.
  
The {@code iterator} method
     
* merely returns {@code listIterator()}, and the {@code size} method
     
* merely returns the subclass's {@code size} field.
     
*
     
* <p>All methods first check to see if the actual {@code modCount} of
     
* the backing list is equal to its expected value, and throw a
     
* {@code ConcurrentModificationException} if it is not.
     
*
     
* @throws IndexOutOfBoundsException if an endpoint index value is out of range
     
*
         
{@code (fromIndex < 0 || toIndex > size)}
     
* @throws IllegalArgumentException if the endpoint indices are out of order
     
*
         
{@code (fromIndex > toIndex)}
     
*/

    
public List<E> subList(int fromIndex, int toIndex) {
        
return (this instanceof RandomAccess ?
                
new RandomAccessSubList<>(this, fromIndex, toIndex) :
                
new SubList<>(this, fromIndex, toIndex));
    
}

    
// Comparison and hashing

    
/**
     
* Compares the specified object with this list for equality.
  
Returns
     
* {@code true} if and only if the specified object is also a list, both
     
* lists have the same size, and all corresponding pairs of elements in
     
* the two lists are <i>equal</i>.
  
(Two elements {@code e1} and
     
* {@code e2} are <i>equal</i> if {@code (e1==null ? e2==null :
     
* e1.equals(e2))}.)
  
In other words, two lists are defined to be
     
* equal if they contain the same elements in the same order.<p>
     
*
     
* This implementation first checks if the specified object is this
     
* list. If so, it returns {@code true}; if not, it checks if the
     
* specified object is a list. If not, it returns {@code false}; if so,
     
* it iterates over both lists, comparing corresponding pairs of elements.
     
* If any comparison returns {@code false}, this method returns
     
* {@code false}.
  
If either iterator runs out of elements before the
     
* other it returns {@code false} (as the lists are of unequal length);
     
* otherwise it returns {@code true} when the iterations complete.
     
*
     
* @param o the object to be compared for equality with this list
     
* @return {@code true} if the specified object is equal to this list
     
*/

    
public boolean equals(Object o) {
        
if (o == this)
            
return true;
        
if (!(o instanceof List))
            
return false;

        
ListIterator<E> e1 = listIterator();
        
ListIterator<?> e2 = ((List<?>) o).listIterator();
        
while (e1.hasNext() && e2.hasNext()) {
            
E o1 = e1.next();
            
Object o2 = e2.next();
            
if (!(o1==null ? o2==null : o1.equals(o2)))
                
return false;
        
}
        
return !(e1.hasNext() || e2.hasNext());
    
}

    
/**
     
* Returns the hash code value for this list.
     
*
     
* <p>This implementation uses exactly the code that is used to define the
     
* list hash function in the documentation for the {@link List#hashCode}
     
* method.
     
*
     
* @return the hash code value for this list
     
*/

    
public int hashCode() {
        
int hashCode = 1;
        
for (E e : this)
            
hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
        
return hashCode;
    
}

    
/**
     
* 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.)
     
*
     
* <p>This method is called by the {@code clear} operation on this list
     
* and its subLists.
  
Overriding this method to take advantage of
     
* the internals of the list implementation can <i>substantially</i>
     
* improve the performance of the {@code clear} operation on this list
     
* and its subLists.
     
*
     
* <p>This implementation gets a list iterator positioned before
     
* {@code fromIndex}, and repeatedly calls {@code ListIterator.next}
     
* followed by {@code ListIterator.remove} until the entire range has
     
* been removed.
  
<b>Note: if {@code ListIterator.remove} requires linear
     
* time, this implementation requires quadratic time.</b>
     
*
     
* @param fromIndex index of first element to be removed
     
* @param toIndex index after last element to be removed
     
*/

    
protected void removeRange(int fromIndex, int toIndex) {
        
ListIterator<E> it = listIterator(fromIndex);
        
for (int i=0, n=toIndex-fromIndex; i<n; i++) {
            
it.next();
            
it.remove();
        
}
    
}

    
/**
     
* The number of times this list has been <i>structurally modified</i>.
     
* Structural modifications are those that change the size of the
     
* list, or otherwise perturb it in such a fashion that iterations in
     
* progress may yield incorrect results.
     
*
     
* <p>This field is used by the iterator and list iterator implementation
     
* returned by the {@code iterator} and {@code listIterator} methods.
     
* If the value of this field changes unexpectedly, the iterator (or list
     
* iterator) will throw a {@code ConcurrentModificationException} in
     
* response to the {@code next}, {@code remove}, {@code previous},
     
* {@code set} or {@code add} operations.
  
This provides
     
* <i>fail-fast</i> behavior, rather than non-deterministic behavior in
     
* the face of concurrent modification during iteration.
     
*
     
* <p><b>Use of this field by subclasses is optional.</b> If a subclass
     
* wishes to provide fail-fast iterators (and list iterators), then it
     
* merely has to increment this field in its {@code add(int, E)} and
     
* {@code remove(int)} methods (and any other methods that it overrides
     
* that result in structural modifications to the list).
  
A single call to
     
* {@code add(int, E)} or {@code remove(int)} must add no more than
     
* one to this field, or the iterators (and list iterators) will throw
     
* bogus {@code ConcurrentModificationExceptions}.
  
If an implementation
     
* does not wish to provide fail-fast iterators, this field may be
     
* ignored.
     
*/

    
protected transient int modCount = 0;

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

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

class SubList<E> extends AbstractList<E> {
    
private final AbstractList<E> l;
    
private final int offset;
    
private int size;

    
SubList(AbstractList<E> list, int fromIndex, int toIndex) {
        
if (fromIndex < 0)
            
throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
        
if (toIndex > list.size())
            
throw new IndexOutOfBoundsException("toIndex = " + toIndex);
        
if (fromIndex > toIndex)
            
throw new IllegalArgumentException("fromIndex(" + fromIndex +
                                               
") > toIndex(" + toIndex + ")");
        
l = list;
        
offset = fromIndex;
        
size = toIndex - fromIndex;
        
this.modCount = l.modCount;
    
}

    
public E set(int index, E element) {
        
rangeCheck(index);
        
checkForComodification();
        
return l.set(index+offset, element);
    
}

    
public E get(int index) {
        
rangeCheck(index);
        
checkForComodification();
        
return l.get(index+offset);
    
}

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

    
public void add(int index, E element) {
        
rangeCheckForAdd(index);
        
checkForComodification();
        
l.add(index+offset, element);
        
this.modCount = l.modCount;
        
size++;
    
}

    
public E remove(int index) {
        
rangeCheck(index);
        
checkForComodification();
        
E result = l.remove(index+offset);
        
this.modCount = l.modCount;
        
size--;
        
return result;
    
}

    
protected void removeRange(int fromIndex, int toIndex) {
        
checkForComodification();
        
l.removeRange(fromIndex+offset, toIndex+offset);
        
this.modCount = l.modCount;
        
size -= (toIndex-fromIndex);
    
}

    
public boolean addAll(Collection<? extends E> c) {
        
return addAll(size, c);
    
}

    
public boolean addAll(int index, Collection<? extends E> c) {
        
rangeCheckForAdd(index);
        
int cSize = c.size();
        
if (cSize==0)
            
return false;

        
checkForComodification();
        
l.addAll(offset+index, c);
        
this.modCount = l.modCount;
        
size += cSize;
        
return true;
    
}

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

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

        
return new ListIterator<E>() {
            
private final ListIterator<E> i = l.listIterator(index+offset);

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

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

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

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

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

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

            
public void remove() {
                
i.remove();
                
SubList.this.modCount = l.modCount;
                
size--;
            
}

            
public void set(E e) {
                
i.set(e);
            
}

            
public void add(E e) {
                
i.add(e);
                
SubList.this.modCount = l.modCount;
                
size++;
            
}
        
};
    
}

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

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

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

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

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

class RandomAccessSubList<E> extends SubList<E> implements RandomAccess {
    
RandomAccessSubList(AbstractList<E> list, int fromIndex, int toIndex) {
        
super(list, fromIndex, toIndex);
    
}

    
public List<E> subList(int fromIndex, int toIndex) {
        
return new RandomAccessSubList<>(this, fromIndex, toIndex);
    
}
}