org.apache.commons.collections.list

Class SetUniqueList

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: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $

Author: Matthew Hawthorne Stephen Colebourne Tom Dunham

Field Summary
protected Setset
Internal Set to maintain uniqueness.
Constructor Summary
protected SetUniqueList(List list, Set set)
Constructor that wraps (not copies) the List and specifies the set to use.
Method Summary
booleanadd(Object object)
Adds an element to the list if it is not already present.
voidadd(int index, Object object)
Adds an element to a specific index in the list if it is not already present.
booleanaddAll(Collection coll)
Adds an element to the end of the list if it is not already present.
booleanaddAll(int index, Collection coll)
Adds a collection of objects to the end of the list avoiding duplicates.
SetasSet()
Gets an unmodifiable view as a Set.
voidclear()
booleancontains(Object object)
booleancontainsAll(Collection coll)
static SetUniqueListdecorate(List list)
Factory method to create a SetList using the supplied list to retain order.
Iteratoriterator()
ListIteratorlistIterator()
ListIteratorlistIterator(int index)
booleanremove(Object object)
Objectremove(int index)
booleanremoveAll(Collection coll)
booleanretainAll(Collection coll)
Objectset(int index, Object object)
Sets the value at the specified index avoiding duplicates.
ListsubList(int fromIndex, int toIndex)

Field Detail

set

protected final Set set
Internal Set to maintain uniqueness.

Constructor Detail

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

Throws: IllegalArgumentException if set or list is null

Method Detail

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

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

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)

containsAll

public boolean containsAll(Collection 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: IllegalArgumentException if list is null

iterator

public Iterator iterator()

listIterator

public ListIterator listIterator()

listIterator

public ListIterator listIterator(int index)

remove

public boolean remove(Object object)

remove

public Object remove(int index)

removeAll

public boolean removeAll(Collection coll)

retainAll

public boolean retainAll(Collection 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.

Parameters: index the index to insert at object the object to set

Returns: the previous object

subList

public List subList(int fromIndex, int toIndex)
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