org.apache.commons.collections.list

Class GrowthList

Implemented Interfaces:
Collection, List, Serializable

public class GrowthList
extends AbstractSerializableListDecorator

Decorates another List to make it seamlessly grow when indices larger than the list size are used on add and set, avoiding most IndexOutOfBoundsExceptions.

This class avoids errors by growing when a set or add method would normally throw an IndexOutOfBoundsException. Note that IndexOutOfBoundsException IS returned for invalid negative indices.

Trying to set or add to an index larger than the size will cause the list to grow (using null elements). Clearly, care must be taken not to use excessively large indices, as the internal list will grow to match.

Trying to use any method other than add or set with an invalid index will call the underlying list and probably result in an IndexOutOfBoundsException.

Take care when using this list with null values, as null is the value added when growing the list.

All sub-lists will access the underlying list directly, and will throw IndexOutOfBoundsExceptions.

This class differs from LazyList because here growth occurs on set and add, where LazyList grows on get. However, they can be used together by decorating twice.

Version:
$Revision: 155406 $ $Date: 2006-05-12 23:57:03 +0100 (Fri, 12 May 2006) $
Authors:
Stephen Colebourne
Paul Legato
Since:
Commons Collections 3.2
See Also:
LazyList

Field Summary

Fields inherited from class org.apache.commons.collections.collection.AbstractCollectionDecorator

collection

Constructor Summary

GrowthList()
Constructor that uses an ArrayList internally.
GrowthList(List list)
Constructor that wraps (not copies).
GrowthList(int initialSize)
Constructor that uses an ArrayList internally.

Method Summary

void
add(int index, Object element)
Decorate the add method to perform the growth behaviour.
boolean
addAll(int index, Collection coll)
Decorate the addAll method to perform the growth behaviour.
static List
decorate(List list)
Factory method to create a growth list.
Object
set(int index, Object element)
Decorate the set method to perform the growth behaviour.

Methods inherited from class org.apache.commons.collections.list.AbstractListDecorator

add, addAll, get, getList, indexOf, lastIndexOf, listIterator, listIterator, remove, set, subList

Methods inherited from class org.apache.commons.collections.collection.AbstractCollectionDecorator

add, addAll, clear, contains, containsAll, equals, getCollection, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString

Constructor Details

GrowthList

public GrowthList()
Constructor that uses an ArrayList internally.

GrowthList

protected GrowthList(List list)
Constructor that wraps (not copies).
Parameters:
list - the list to decorate, must not be null

GrowthList

public GrowthList(int initialSize)
Constructor that uses an ArrayList internally.
Parameters:
initialSize - the initial size of the ArrayList

Method Details

add

public void add(int index,
                Object element)
Decorate the add method to perform the growth behaviour.

If the requested index is greater than the current size, the list will grow to the new size. Indices between the old size and the requested size will be filled with null.

If the index is less than the current size, the value will be added to the underlying list directly. If the index is less than zero, the underlying list is called, which will probably throw an IndexOutOfBoundsException.

Overrides:
add in interface AbstractListDecorator
Parameters:
index - the index to add at
element - the object to add at the specified index

addAll

public boolean addAll(int index,
                      Collection coll)
Decorate the addAll method to perform the growth behaviour.

If the requested index is greater than the current size, the list will grow to the new size. Indices between the old size and the requested size will be filled with null.

If the index is less than the current size, the values will be added to the underlying list directly. If the index is less than zero, the underlying list is called, which will probably throw an IndexOutOfBoundsException.

Overrides:
addAll in interface AbstractListDecorator
Parameters:
index - the index to add at
coll - the collection to add at the specified index
Returns:
true if the list changed

decorate

public static List decorate(List list)
Factory method to create a growth list.
Parameters:
list - the list to decorate, must not be null

set

public Object set(int index,
                  Object element)
Decorate the set method to perform the growth behaviour.

If the requested index is greater than the current size, the list will grow to the new size. Indices between the old size and the requested size will be filled with null.

If the index is less than the current size, the value will be set onto the underlying list directly. If the index is less than zero, the underlying list is called, which will probably throw an IndexOutOfBoundsException.

Overrides:
set in interface AbstractListDecorator
Parameters:
index - the index to set
element - the object to set at the specified index
Returns:
the object previously at that index

Copyright © 2001-2006 Apache Software Foundation. All Rights Reserved.