org.apache.commons.collections.set

Class ListOrderedSet

java.lang.Object

org.apache.commons.collections.collection.AbstractCollectionDecorator

org.apache.commons.collections.set.AbstractSetDecorator

org.apache.commons.collections.set.AbstractSerializableSetDecorator

org.apache.commons.collections.set.ListOrderedSet

All Implemented Interfaces:

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

public class ListOrderedSet
extends AbstractSerializableSetDecorator
implements java.util.Set

Decorates another Set to ensure that the order of addition is retained and used by the iterator.

If an object is added to the set for a second time, it will remain in the original position in the iteration. The order can be observed from the set via the iterator or toArray methods.

The ListOrderedSet also has various useful direct methods. These include many from List, such as get(int), remove(int) and indexOf(int). An unmodifiable List view of the set can be obtained via asList().

This class cannot implement the List interface directly as various interface methods (notably equals/hashCode) are incompatable with a set.

This class is Serializable from Commons Collections 3.1.

Since:

Commons Collections 3.0

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ListOrderedSet() Constructs a new empty ListOrderedSet using a HashSet and an ArrayList internally.

Method Summary

Modifier and Type	Method and Description
void	add(int index, java.lang.Object object)
boolean	add(java.lang.Object object)
boolean	addAll(java.util.Collection coll)
boolean	addAll(int index, java.util.Collection coll)
java.util.List	asList() Gets an unmodifiable view of the order of the Set.
void	clear()
static ListOrderedSet	decorate(java.util.List list) Factory method to create an ordered set using the supplied list to retain order.
static ListOrderedSet	decorate(java.util.Set set) Factory method to create an ordered set.
static ListOrderedSet	decorate(java.util.Set set, java.util.List list) Factory method to create an ordered set specifying the list and set to use.
java.lang.Object	get(int index)
int	indexOf(java.lang.Object object)
java.util.Iterator	iterator()
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[]	toArray()
java.lang.Object[]	toArray(java.lang.Object[] a)
java.lang.String	toString() Uses the underlying List's toString so that order is achieved.

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

contains, containsAll, equals, hashCode, isEmpty, size

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Set

contains, containsAll, equals, hashCode, isEmpty, size, spliterator

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

ListOrderedSet

public ListOrderedSet()

Constructs a new empty ListOrderedSet using a HashSet and an ArrayList internally.

Since:

Commons Collections 3.1

Method Detail

decorate

public static ListOrderedSet decorate(java.util.Set set,
                                      java.util.List list)

Factory method to create an ordered set specifying the list and set to use.

The list and set must both be empty.

Parameters:

set - the set to decorate, must be empty and not null

list - the list to decorate, must be empty and not null

Throws:

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

java.lang.IllegalArgumentException - if either the set or list is not empty

Since:

Commons Collections 3.1

decorate

public static ListOrderedSet decorate(java.util.Set set)

Factory method to create an ordered set.

An ArrayList is used to retain order.

Parameters:

set - the set to decorate, must not be null

Throws:

java.lang.IllegalArgumentException - if set is null

decorate

public static ListOrderedSet decorate(java.util.List list)

Factory method to create an ordered set using the supplied list to retain order.

A HashSet is used for the set behaviour.

NOTE: If the list contains duplicates, the duplicates are removed, altering the specified list.

Parameters:

list - the list to decorate, must not be null

Throws:

java.lang.IllegalArgumentException - if list is null

asList

public java.util.List asList()

Gets an unmodifiable view of the order of the Set.

Returns:

an unmodifiable list view

clear

public void clear()

Specified by:

clear in interface java.util.Collection

Specified by:

clear in interface java.util.Set

Overrides:

clear 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.Set

Overrides:

iterator in class AbstractCollectionDecorator

add

public boolean add(java.lang.Object object)

Specified by:

add in interface java.util.Collection

Specified by:

add in interface java.util.Set

Overrides:

add in class AbstractCollectionDecorator

addAll

public boolean addAll(java.util.Collection coll)

Specified by:

addAll in interface java.util.Collection

Specified by:

addAll in interface java.util.Set

Overrides:

addAll in class AbstractCollectionDecorator

remove

public boolean remove(java.lang.Object object)

Specified by:

remove in interface java.util.Collection

Specified by:

remove in interface java.util.Set

Overrides:

remove in class AbstractCollectionDecorator

removeAll

public boolean removeAll(java.util.Collection coll)

Specified by:

removeAll in interface java.util.Collection

Specified by:

removeAll in interface java.util.Set

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.Set

Overrides:

retainAll in class AbstractCollectionDecorator

toArray

public java.lang.Object[] toArray()

Specified by:

toArray in interface java.util.Collection

Specified by:

toArray in interface java.util.Set

Overrides:

toArray in class AbstractCollectionDecorator

toArray

public java.lang.Object[] toArray(java.lang.Object[] a)

Specified by:

toArray in interface java.util.Collection

Specified by:

toArray in interface java.util.Set

Overrides:

toArray in class AbstractCollectionDecorator

get

public java.lang.Object get(int index)

indexOf

public int indexOf(java.lang.Object object)

add

public void add(int index,
                java.lang.Object object)

addAll

public boolean addAll(int index,
                      java.util.Collection coll)

remove

public java.lang.Object remove(int index)

toString

public java.lang.String toString()

Uses the underlying List's toString so that order is achieved. This means that the decorated Set's toString is not used, so any custom toStrings will be ignored.

Overrides:

toString in class AbstractCollectionDecorator