Class LazyList<E>
- All Implemented Interfaces:
Serializable
,Iterable<E>
,Collection<E>
,List<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. 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.
- Since:
- 3.0
- Version:
- $Id: LazyList.java 1686855 2015-06-22 13:00:27Z tn $
- See Also:
-
Constructor Summary
Constructors -
Method Summary
Methods inherited from class org.apache.commons.collections4.list.AbstractListDecorator
add, addAll, decorated, equals, hashCode, indexOf, lastIndexOf, listIterator, listIterator, remove, set
Methods inherited from class org.apache.commons.collections4.collection.AbstractCollectionDecorator
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, setCollection, size, toArray, toArray, toString
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArray
-
Constructor Details
-
LazyList
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:
NullPointerException
- if list or factory is null
-
-
Method Details
-
lazyList
Factory method to create a lazily instantiating list.- Type Parameters:
E
- the type of the elements in the list- Parameters:
list
- the list to decorate, must not be nullfactory
- the factory to use for creation, must not be null- Returns:
- a new lazy list
- Throws:
NullPointerException
- if list or factory is null- Since:
- 4.0
-
get
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.
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subList
-