org.apache.commons.collections.list
Class LazyList<E>
java.lang.Object
org.apache.commons.collections.collection.AbstractCollectionDecorator<E>
org.apache.commons.collections.list.AbstractListDecorator<E>
org.apache.commons.collections.list.AbstractSerializableListDecorator<E>
org.apache.commons.collections.list.LazyList<E>
- All Implemented Interfaces:
- Serializable, Iterable<E>, Collection<E>, List<E>
public class LazyList<E>
- extends AbstractSerializableListDecorator<E>
Decorates another List
to create objects in the list on demand.
When the get(int)
method is called with an index greater than
the size of the list, the list will automatically grow in size and return
a new object from the specified factory. The gaps will be filled by null.
If a get method call encounters a null, it will be replaced with a new
object from the factory. Thus this list is unsuitable for storing null
objects.
For instance:
Factory factory = new Factory() {
public Object create() {
return new Date();
}
}
List lazy = LazyList.decorate(new ArrayList(), factory);
Object obj = lazy.get(3);
After the above code is executed, obj
will contain
a new Date
instance. Furthermore, that Date
instance is the fourth element in the list. The first, second,
and third element are all set to null
.
This class is Serializable from Commons Collections 3.1.
- Since:
- Commons Collections 3.0
- Version:
- $Revision: 1.1.1.1 $ $Date: 2005/05/23 04:35:22 $
- Author:
- Stephen Colebourne, Arron Bates, Paul Jack
- See Also:
- Serialized Form
Field Summary |
protected Factory<? extends E> |
factory
The factory to use to lazily instantiate the objects |
Constructor Summary |
protected |
LazyList(List<E> list,
Factory<? extends E> factory)
Constructor that wraps (not copies). |
Method Summary |
static
|
decorate(List<E> list,
Factory<? extends E> factory)
Factory method to create a lazily instantiating list. |
E |
get(int index)
Decorate the get method to perform the lazy behaviour. |
List<E> |
subList(int fromIndex,
int toIndex)
|
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 |
Methods inherited from interface java.util.List |
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray |
factory
protected final Factory<? extends E> factory
- The factory to use to lazily instantiate the objects
LazyList
protected LazyList(List<E> list,
Factory<? extends E> factory)
- Constructor that wraps (not copies).
- Parameters:
list
- the list to decorate, must not be nullfactory
- the factory to use for creation, must not be null
- Throws:
IllegalArgumentException
- if list or factory is null
decorate
public static <E> List<E> decorate(List<E> list,
Factory<? extends E> factory)
- Factory method to create a lazily instantiating list.
- Parameters:
list
- the list to decorate, must not be nullfactory
- the factory to use for creation, must not be null
- Throws:
IllegalArgumentException
- if list or factory is null
get
public E get(int index)
- Decorate the get method to perform the lazy behaviour.
If the requested index is greater than the current size, the list will
grow to the new size and a new object will be returned from the factory.
Indexes in-between the old size and the requested size are left with a
placeholder that is replaced with a factory object when requested.
- Specified by:
get
in interface List<E>
- Overrides:
get
in class AbstractListDecorator<E>
- Parameters:
index
- the index to retrieve
subList
public List<E> subList(int fromIndex,
int toIndex)
- Specified by:
subList
in interface List<E>
- Overrides:
subList
in class AbstractListDecorator<E>
Copyright © 2005-2005 Apache Software Foundation, Matt Hall, John Watkinson. All Rights Reserved.