public class LazyList extends AbstractSerializableListDecorator
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 differs from GrowthList
because here growth occurs on
get, where GrowthList
grows on set and add. However, they
could easily be used together by decorating twice.
This class is Serializable from Commons Collections 3.1.
GrowthList
,
Serialized FormModifier and Type | Method and Description |
---|---|
static java.util.List |
decorate(java.util.List list,
Factory factory)
Factory method to create a lazily instantiating list.
|
java.lang.Object |
get(int index)
Decorate the get method to perform the lazy behaviour.
|
java.util.List |
subList(int fromIndex,
int toIndex) |
add, addAll, indexOf, lastIndexOf, listIterator, listIterator, remove, set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString
public static java.util.List decorate(java.util.List list, Factory factory)
list
- the list to decorate, must not be nullfactory
- the factory to use for creation, must not be nulljava.lang.IllegalArgumentException
- if list or factory is nullpublic java.lang.Object get(int index)
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.
get
in interface java.util.List
get
in class AbstractListDecorator
index
- the index to retrievepublic java.util.List subList(int fromIndex, int toIndex)
subList
in interface java.util.List
subList
in class AbstractListDecorator
Copyright © 2010 - 2020 Adobe. All Rights Reserved