org.apache.commons.collections.list

Class SetUniqueList

java.lang.Object
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+--org.apache.commons.collections.collection.AbstractCollectionDecorator
   |
   +--org.apache.commons.collections.list.AbstractListDecorator
      |
      +--org.apache.commons.collections.list.SetUniqueList

public class SetUniqueList
extends AbstractListDecorator

Decorates a List to ensure that no duplicates are present much like a Set.

The List interface makes certain assumptions/requirements. This implementation breaks these in certain ways, but this is merely the result of rejecting duplicates. Each violation is explained in the method, but it should not affect you.

The org.apache.commons.collections.set.ListOrderedSet ListOrderedSet class provides an alternative approach, by wrapping an existing Set and retaining insertion order in the iterator.

Since:

Commons Collections 3.0

Authors:

Matthew Hawthorne
Stephen Colebourne

Field Summary

Set	set Internal Set to maintain uniqueness.

Constructor Summary

SetUniqueList(List list, Set set)

Constructor that wraps (not copies) the List and specifies the set to use.

Method Summary

boolean	add(Object object) Adds an element to the list if it is not already present.
void	add(int index, Object object) Adds an element to a specific index in the list if it is not already present.
boolean	addAll(Collection coll) Adds an element to the end of the list if it is not already present.
boolean	addAll(int index, Collection coll) Adds a collection of objects to the end of the list avoiding duplicates.
Set	asSet() Gets an unmodifiable view as a Set.
void	clear()
boolean	contains(Object object)
boolean	containsAll(Collection coll)
static SetUniqueList	decorate(List list) Factory method to create a SetList using the supplied list to retain order.
Iterator	iterator()
ListIterator	listIterator()
ListIterator	listIterator(int index)
boolean	remove(Object object)
Object	remove(int index)
boolean	removeAll(Collection coll)
boolean	retainAll(Collection coll)
Object	set(int index, Object object) Sets the value at the specified index avoiding duplicates.
List	subList(int fromIndex, int toIndex)

Field Details

set

protected final Set set

Internal Set to maintain uniqueness.

Constructor Details

SetUniqueList

protected SetUniqueList(List list, Set set)

Constructor that wraps (not copies) the List and specifies the set to use.

The set and list must both be correctly initialised to the same elements.

Parameters:

list - the set to decorate, must not be null
set - the list to decorate, must not be null

Throws:

- if set or list is null

`Method Details`

add
public void add(int index, Object object)
 Adds an element to a specific index in the list if it is not already present.
 (Violation)
 The List interface makes the assumption that the element is
 always inserted. This may not happen with this implementation.
Parameters:
index - the index to insert at
object - the object to add
add
public boolean add(Object object)
 Adds an element to the list if it is not already present.
 (Violation)
 The List interface requires that this method returns
 true always. However this class may return false
 because of the Set behaviour.
Parameters:
object - the object to add
Returns:
true if object was added
addAll
public boolean addAll(Collection coll)
 Adds an element to the end of the list if it is not already present.
 (Violation)
 The List interface makes the assumption that the element is
 always inserted. This may not happen with this implementation.
Parameters:
coll - the collection to add
addAll
public boolean addAll(int index, Collection coll)
 Adds a collection of objects to the end of the list avoiding duplicates.
 
 Only elements that are not already in this list will be added, and
 duplicates from the specified collection will be ignored.
 
(Violation)
 The List interface makes the assumption that the elements
 are always inserted. This may not happen with this implementation.
Parameters:
index - the index to insert at
coll - the collection to add in iterator order
Returns:
true if this collection changed
asSet
public Set asSet()
 Gets an unmodifiable view as a Set.
Returns:
an unmodifiable set view
clear
public void clear()
contains
public boolean contains(Object object)
Parameters:
object
containsAll
public boolean containsAll(Collection coll)
Parameters:
coll
decorate
public static SetUniqueList decorate(List list)
 Factory method to create a SetList using the supplied list to retain order.
 
 If the list contains duplicates, these are removed (first indexed one kept).
 A HashSet is used for the set behaviour.
Parameters:
list - the list to decorate, must not be null
Throws:
 - if list is null
iterator
public Iterator iterator()
listIterator
public ListIterator listIterator()
listIterator
public ListIterator listIterator(int index)
Parameters:
index
remove
public Object remove(int index)
Parameters:
index
remove
public boolean remove(Object object)
Parameters:
object
removeAll
public boolean removeAll(Collection coll)
Parameters:
coll
retainAll
public boolean retainAll(Collection coll)
Parameters:
coll
set
public Object set(int index, Object object)
 Sets the value at the specified index avoiding duplicates.
 
 The object is set into the specified index.
 Afterwards, any previous duplicate is removed
 If the object is not already in the list then a normal set occurs.
 If it is present, then the old version is removed and re-added at this index
Parameters:
index - the index to insert at
object - the object to set
Returns:
the previous object
subList
public List subList(int fromIndex, int toIndex)
Parameters:
fromIndex
toIndex
Generated on
  February 15, 2004
  by GNU Classpath Tools (Gjdoc XmlDoclet 0.6.1).