org.apache.commons.collections.list

Class GrowthList

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.

Since: Commons Collections 3.2

Version: $Revision: 155406 $ $Date: 2006-05-12 23:57:03 +0100 (Fri, 12 May 2006) $

Author: Stephen Colebourne Paul Legato

See Also: LazyList

Constructor Summary
GrowthList()
Constructor that uses an ArrayList internally.
GrowthList(int initialSize)
Constructor that uses an ArrayList internally.
protected GrowthList(List list)
Constructor that wraps (not copies).
Method Summary
voidadd(int index, Object element)
Decorate the add method to perform the growth behaviour.
booleanaddAll(int index, Collection coll)
Decorate the addAll method to perform the growth behaviour.
static Listdecorate(List list)
Factory method to create a growth list.
Objectset(int index, Object element)
Decorate the set method to perform the growth behaviour.

Constructor Detail

GrowthList

public GrowthList()
Constructor that uses an ArrayList internally.

GrowthList

public GrowthList(int initialSize)
Constructor that uses an ArrayList internally.

Parameters: initialSize the initial size of the ArrayList

Throws: IllegalArgumentException if initial size is invalid

GrowthList

protected GrowthList(List list)
Constructor that wraps (not copies).

Parameters: list the list to decorate, must not be null

Throws: IllegalArgumentException if list is null

Method Detail

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.

Parameters: index the index to add at element the object to add at the specified index

Throws: UnsupportedOperationException if the underlying list doesn't implement set ClassCastException if the underlying list rejects the element IllegalArgumentException if the underlying list rejects the element

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.

Parameters: index the index to add at coll the collection to add at the specified index

Returns: true if the list changed

Throws: UnsupportedOperationException if the underlying list doesn't implement set ClassCastException if the underlying list rejects the element IllegalArgumentException if the underlying list rejects the element

decorate

public static List decorate(List list)
Factory method to create a growth list.

Parameters: list the list to decorate, must not be null

Throws: IllegalArgumentException if list is 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.

Parameters: index the index to set element the object to set at the specified index

Returns: the object previously at that index

Throws: UnsupportedOperationException if the underlying list doesn't implement set ClassCastException if the underlying list rejects the element IllegalArgumentException if the underlying list rejects the element

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