org.apache.commons.collections.list
Class SetUniqueList

java.lang.Object
  org.apache.commons.collections.collection.AbstractCollectionDecorator
      org.apache.commons.collections.list.AbstractListDecorator
          org.apache.commons.collections.list.AbstractSerializableListDecorator
              org.apache.commons.collections.list.SetUniqueList

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable, java.util.Collection, java.util.List

public class SetUniqueList
extends AbstractSerializableListDecorator

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. Bear in mind that Sets require immutable objects to function correctly.

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

This class is Serializable from Commons Collections 3.1.

Since:

Commons Collections 3.0

Version:

$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Matthew Hawthorne, Stephen Colebourne, Tom Dunham

See Also:

Serialized Form

Field Summary

protected java.util.Set

set Internal Set to maintain uniqueness.

Fields inherited from class org.apache.commons.collections.collection.AbstractCollectionDecorator

collection

Constructor Summary

protected

SetUniqueList(java.util.List list, java.util.Set set) Constructor that wraps (not copies) the List and specifies the set to use.

Method Summary

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

Methods inherited from class org.apache.commons.collections.list.AbstractListDecorator

get, getList, indexOf, lastIndexOf

Methods inherited from class org.apache.commons.collections.collection.AbstractCollectionDecorator

equals, getCollection, hashCode, isEmpty, 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.List

equals, hashCode, isEmpty, size, toArray, toArray

Field Detail

set

protected final java.util.Set set

Internal Set to maintain uniqueness.

Constructor Detail

SetUniqueList

protected SetUniqueList(java.util.List list,
                        java.util.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:

set - the set to decorate, must not be null

list - the list to decorate, must not be null

Throws:

java.lang.IllegalArgumentException - if set or list is null

Method Detail

decorate

public static SetUniqueList decorate(java.util.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:

java.lang.IllegalArgumentException - if list is null

asSet

public java.util.Set asSet()

Gets an unmodifiable view as a Set.

Returns:

an unmodifiable set view

add

public boolean add(java.lang.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.

Specified by:

add in interface java.util.Collection

Specified by:

add in interface java.util.List

Overrides:

add in class AbstractCollectionDecorator

Parameters:

object - the object to add

Returns:

true if object was added

add

public void add(int index,
                java.lang.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.

Specified by:

add in interface java.util.List

Overrides:

add in class AbstractListDecorator

Parameters:

index - the index to insert at

object - the object to add

addAll

public boolean addAll(java.util.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.

Specified by:

addAll in interface java.util.Collection

Specified by:

addAll in interface java.util.List

Overrides:

addAll in class AbstractCollectionDecorator

Parameters:

coll - the collection to add

addAll

public boolean addAll(int index,
                      java.util.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.

Specified by:

addAll in interface java.util.List

Overrides:

addAll in class AbstractListDecorator

Parameters:

index - the index to insert at

coll - the collection to add in iterator order

Returns:

true if this collection changed

set

public java.lang.Object set(int index,
                            java.lang.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.

Specified by:

set in interface java.util.List

Overrides:

set in class AbstractListDecorator

Parameters:

index - the index to insert at

object - the object to set

Returns:

the previous object

remove

public boolean remove(java.lang.Object object)

Specified by:

remove in interface java.util.Collection

Specified by:

remove in interface java.util.List

Overrides:

remove in class AbstractCollectionDecorator

remove

public java.lang.Object remove(int index)

Specified by:

remove in interface java.util.List

Overrides:

remove in class AbstractListDecorator

removeAll

public boolean removeAll(java.util.Collection coll)

Specified by:

removeAll in interface java.util.Collection

Specified by:

removeAll in interface java.util.List

Overrides:

removeAll in class AbstractCollectionDecorator

retainAll

public boolean retainAll(java.util.Collection coll)

Specified by:

retainAll in interface java.util.Collection

Specified by:

retainAll in interface java.util.List

Overrides:

retainAll in class AbstractCollectionDecorator

clear

public void clear()

Specified by:

clear in interface java.util.Collection

Specified by:

clear in interface java.util.List

Overrides:

clear in class AbstractCollectionDecorator

contains

public boolean contains(java.lang.Object object)

Specified by:

contains in interface java.util.Collection

Specified by:

contains in interface java.util.List

Overrides:

contains in class AbstractCollectionDecorator

containsAll

public boolean containsAll(java.util.Collection coll)

Specified by:

containsAll in interface java.util.Collection

Specified by:

containsAll in interface java.util.List

Overrides:

containsAll in class AbstractCollectionDecorator

iterator

public java.util.Iterator iterator()

Specified by:

iterator in interface java.lang.Iterable

Specified by:

iterator in interface java.util.Collection

Specified by:

iterator in interface java.util.List

Overrides:

iterator in class AbstractCollectionDecorator

listIterator

public java.util.ListIterator listIterator()

Specified by:

listIterator in interface java.util.List

Overrides:

listIterator in class AbstractListDecorator

listIterator

public java.util.ListIterator listIterator(int index)

Specified by:

listIterator in interface java.util.List

Overrides:

listIterator in class AbstractListDecorator

subList

public java.util.List subList(int fromIndex,
                              int toIndex)

Specified by:

subList in interface java.util.List

Overrides:

subList in class AbstractListDecorator