public class LazyList<E> extends AbstractSerializableListDecorator<E>
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 or transformer. 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<Date> factory = new Factory<Date>() {
public Date create() {
return new Date();
}
}
List<Date> lazy = LazyList.decorate(new ArrayList<Date>(), factory);
Date date = lazy.get(3);
After the above code is executed, date 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 Form| Modifier | Constructor and Description |
|---|---|
protected |
LazyList(List<E> list,
Factory<? extends E> factory)
Constructor that wraps (not copies).
|
protected |
LazyList(List<E> list,
Transformer<Integer,? extends E> transformer)
Constructor that wraps (not copies).
|
| Modifier and Type | Method and Description |
|---|---|
E |
get(int index)
Decorate the get method to perform the lazy behaviour.
|
static <E> LazyList<E> |
lazyList(List<E> list,
Factory<? extends E> factory)
Factory method to create a lazily instantiating list.
|
static <E> LazyList<E> |
lazyList(List<E> list,
Transformer<Integer,? extends E> transformer)
Transformer method to create a lazily instantiating list.
|
List<E> |
subList(int fromIndex,
int toIndex) |
add, addAll, decorated, equals, hashCode, indexOf, lastIndexOf, listIterator, listIterator, remove, setadd, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, removeIf, retainAll, setCollection, size, toArray, toArray, toStringclone, finalize, getClass, notify, notifyAll, wait, wait, waitadd, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, replaceAll, retainAll, size, sort, spliterator, toArray, toArrayparallelStream, removeIf, streamprotected LazyList(List<E> list, Factory<? extends E> factory)
list - the list to decorate, must not be nullfactory - the factory to use for creation, must not be nullNullPointerException - if list or factory is nullprotected LazyList(List<E> list, Transformer<Integer,? extends E> transformer)
list - the list to decorate, must not be nulltransformer - the transformer to use for creation, must not be nullNullPointerException - if list or transformer is nullpublic static <E> LazyList<E> lazyList(List<E> list, Factory<? extends E> factory)
E - the type of the elements in the listlist - the list to decorate, must not be nullfactory - the factory to use for creation, must not be nullNullPointerException - if list or factory is nullpublic static <E> LazyList<E> lazyList(List<E> list, Transformer<Integer,? extends E> transformer)
E - the type of the elements in the listlist - the list to decorate, must not be nulltransformer - the transformer to use for creation, must not be nullNullPointerException - if list or transformer is nullpublic E 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 or transformer. Indexes in-between the old size and the requested size are left with a placeholder that is replaced with a factory or transformer object when requested.
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