buri.ddmsence.util

Class LazyList

Object

buri.ddmsence.util.LazyList

All Implemented Interfaces:

Serializable, Iterable, Collection, List

public class LazyList
extends Object
implements List, Serializable

Utility class for a list with dynamically added contents.

LazyList wraps around a standard ArrayList and ensures that any get() activity which returns a null value will return a freshly instantiated item instead.

This class should allow the Component Builder framework to function well within a form-based UI, where child components are added / removed at the web page level.

This class is similar in intent to the Apache commons-collections version, but my implementation differs in the following ways:

• Simplified layers of abstraction.
• Eliminated overhead of Factory boilerplate to instantiate new items. Classes can just be instantiated through the basic no-arg constructor.
• Interim positions are also instantiated when an index beyond the size of the list is requested.

Since:

1.9.0

Author:

Brian Uri!

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LazyList(Class instantiatingClass) Base constructor for a lazy list.
LazyList(List<?> list, Class instantiatingClass) Complete constructor for a lazy list.

Method Summary

Modifier and Type	Method and Description
void	add(int index, Object element)
boolean	add(Object o)
boolean	addAll(Collection c)
boolean	addAll(int index, Collection c)
void	clear()
boolean	contains(Object o)
boolean	containsAll(Collection c)
boolean	equals(Object object)
Object	get(int index) Intercepts the get() method to create new items if get() might return null.
Class	getInstantiatingClass() Accessor for the class that will be instantiated lazily
int	hashCode()
int	indexOf(Object o)
boolean	isEmpty()
Iterator<?>	iterator()
int	lastIndexOf(Object o)
ListIterator<?>	listIterator()
ListIterator<?>	listIterator(int index)
Object	remove(int index)
boolean	remove(Object o)
boolean	removeAll(Collection c)
boolean	retainAll(Collection c)
Object	set(int index, Object element)
int	size()
List<?>	subList(int fromIndex, int toIndex) Intercepts the subList method to maintain a LazyList on the returned sublist.
Object[]	toArray()
Object[]	toArray(Object[] a)
String	toString()

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface List

replaceAll, sort, spliterator

Methods inherited from interface Collection

parallelStream, removeIf, stream

Methods inherited from interface Iterable

forEach

Constructor Detail

LazyList

public LazyList(Class instantiatingClass)

Base constructor for a lazy list.

Parameters:

instantiatingClass - the class that will be instantiated when get() returns null

Throws:

IllegalArgumentException - if either the list or class are null

LazyList

public LazyList(List<?> list,
                Class instantiatingClass)

Complete constructor for a lazy list.

Parameters:

list - the underlying list that will be wrapped

instantiatingClass - the class that will be instantiated when get() returns null

Throws:

IllegalArgumentException - if either the list or class are null

Method Detail

equals

public boolean equals(Object object)

Specified by:

equals in interface Collection

Specified by:

equals in interface List

Overrides:

equals in class Object

See Also:

Object.equals(Object)

hashCode

public int hashCode()

Specified by:

hashCode in interface Collection

Specified by:

hashCode in interface List

Overrides:

hashCode in class Object

See Also:

Object.hashCode()

toString

public String toString()

Overrides:

toString in class Object

See Also:

Object.toString()

get

public Object get(int index)

Intercepts the get() method to create new items if get() might return null. The type of the item returned is determined by the instantiatingClass of the LazyList, and will be instantiated with the no-args constructor via newInstance().

If an index is requested beyond the bounds of the list size, the list will extend to that position and interim positions will also be instantiated.

Specified by:

get in interface List

Parameters:

index - the index to retrieve

subList

public List<?> subList(int fromIndex,
                       int toIndex)

Intercepts the subList method to maintain a LazyList on the returned sublist.

Specified by:

subList in interface List

See Also:

List.subList(int, int)

getInstantiatingClass

public Class getInstantiatingClass()

Accessor for the class that will be instantiated lazily

size

public int size()

Specified by:

size in interface Collection

Specified by:

size in interface List

See Also:

List.size()

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Collection

Specified by:

isEmpty in interface List

See Also:

List.isEmpty()

contains

public boolean contains(Object o)

Specified by:

contains in interface Collection

Specified by:

contains in interface List

See Also:

List.contains(java.lang.Object)

iterator

public Iterator<?> iterator()

Specified by:

iterator in interface Iterable

Specified by:

iterator in interface Collection

Specified by:

iterator in interface List

See Also:

List.iterator()

toArray

public Object[] toArray()

Specified by:

toArray in interface Collection

Specified by:

toArray in interface List

See Also:

List.toArray()

toArray

public Object[] toArray(Object[] a)

Specified by:

toArray in interface Collection

Specified by:

toArray in interface List

See Also:

List.toArray(Object[])

add

public boolean add(Object o)

Specified by:

add in interface Collection

Specified by:

add in interface List

See Also:

List.add(java.lang.Object)

remove

public boolean remove(Object o)

Specified by:

remove in interface Collection

Specified by:

remove in interface List

See Also:

List.remove(java.lang.Object)

containsAll

public boolean containsAll(Collection c)

Specified by:

containsAll in interface Collection

Specified by:

containsAll in interface List

See Also:

List.containsAll(java.util.Collection)

addAll

public boolean addAll(Collection c)

Specified by:

addAll in interface Collection

Specified by:

addAll in interface List

See Also:

List.addAll(java.util.Collection)

addAll

public boolean addAll(int index,
                      Collection c)

Specified by:

addAll in interface List

See Also:

List.addAll(int, java.util.Collection)

removeAll

public boolean removeAll(Collection c)

Specified by:

removeAll in interface Collection

Specified by:

removeAll in interface List

See Also:

List.removeAll(java.util.Collection)

retainAll

public boolean retainAll(Collection c)

Specified by:

retainAll in interface Collection

Specified by:

retainAll in interface List

See Also:

List.retainAll(java.util.Collection)

clear

public void clear()

Specified by:

clear in interface Collection

Specified by:

clear in interface List

See Also:

List.clear()

set

public Object set(int index,
                  Object element)

Specified by:

set in interface List

See Also:

List.set(int, java.lang.Object)

add

public void add(int index,
                Object element)

Specified by:

add in interface List

See Also:

List.add(int, java.lang.Object)

remove

public Object remove(int index)

Specified by:

remove in interface List

See Also:

List.remove(int)

indexOf

public int indexOf(Object o)

Specified by:

indexOf in interface List

See Also:

List.indexOf(java.lang.Object)

lastIndexOf

public int lastIndexOf(Object o)

Specified by:

lastIndexOf in interface List

See Also:

List.lastIndexOf(java.lang.Object)

listIterator

public ListIterator<?> listIterator()

Specified by:

listIterator in interface List

See Also:

List.listIterator()

listIterator

public ListIterator<?> listIterator(int index)

Specified by:

listIterator in interface List

See Also:

List.listIterator(int)