org.apache.commons.collections4.set
Class ListOrderedSet<E>

java.lang.Object
  extended by org.apache.commons.collections4.collection.AbstractCollectionDecorator<E>
      extended by org.apache.commons.collections4.set.AbstractSetDecorator<E>
          extended by org.apache.commons.collections4.set.AbstractSerializableSetDecorator<E>
              extended by org.apache.commons.collections4.set.ListOrderedSet<E>
All Implemented Interfaces:
Serializable, Iterable<E>, Collection<E>, Set<E>

public class ListOrderedSet<E>
extends AbstractSerializableSetDecorator<E>
implements Set<E>

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 incompatible with a set.

This class is Serializable from Commons Collections 3.1.

Since:
3.0
Version:
$Id: ListOrderedSet.java 1494280 2013-06-18 20:07:04Z tn $
See Also:
Serialized Form

Constructor Summary
  ListOrderedSet()
          Constructs a new empty ListOrderedSet using a HashSet and an ArrayList internally.
protected ListOrderedSet(Set<E> set)
          Constructor that wraps (not copies).
protected ListOrderedSet(Set<E> set, List<E> list)
          Constructor that wraps (not copies) the Set and specifies the list to use.
 
Method Summary
 boolean add(E object)
           
 void add(int index, E object)
          Inserts the specified element at the specified position if it is not yet contained in this ordered set (optional operation).
 boolean addAll(Collection<? extends E> coll)
           
 boolean addAll(int index, Collection<? extends E> coll)
          Inserts all elements in the specified collection not yet contained in the ordered set at the specified position (optional operation).
 List<E> asList()
          Gets an unmodifiable view of the order of the Set.
 void clear()
           
 E get(int index)
          Returns the element at the specified position in this ordered set.
 int indexOf(Object object)
          Returns the index of the first occurrence of the specified element in ordered set.
 OrderedIterator<E> iterator()
           
static
<E> ListOrderedSet<E>
listOrderedSet(List<E> list)
          Factory method to create an ordered set using the supplied list to retain order.
static
<E> ListOrderedSet<E>
listOrderedSet(Set<E> set)
          Factory method to create an ordered set.
static
<E> ListOrderedSet<E>
listOrderedSet(Set<E> set, List<E> list)
          Factory method to create an ordered set specifying the list and set to use.
 Object remove(int index)
          Removes the element at the specified position from the ordered set.
 boolean remove(Object object)
           
 boolean removeAll(Collection<?> coll)
           
 boolean retainAll(Collection<?> coll)
           
 Object[] toArray()
           
<T> T[]
toArray(T[] a)
           
 String toString()
          Uses the underlying List's toString so that order is achieved.
 
Methods inherited from class org.apache.commons.collections4.set.AbstractSetDecorator
decorated
 
Methods inherited from class org.apache.commons.collections4.collection.AbstractCollectionDecorator
contains, containsAll, equals, hashCode, isEmpty, setCollection, size
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.Set
contains, containsAll, equals, hashCode, isEmpty, size
 

Constructor Detail

ListOrderedSet

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

Since:
3.1

ListOrderedSet

protected ListOrderedSet(Set<E> set)
Constructor that wraps (not copies).

Parameters:
set - the set to decorate, must not be null
Throws:
IllegalArgumentException - if set is null

ListOrderedSet

protected ListOrderedSet(Set<E> set,
                         List<E> list)
Constructor that wraps (not copies) the Set and specifies the list 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

listOrderedSet

public static <E> ListOrderedSet<E> listOrderedSet(Set<E> set,
                                                   List<E> list)
Factory method to create an ordered set specifying the list and set to use.

The list and set must both be empty.

Type Parameters:
E - the element type
Parameters:
set - the set to decorate, must be empty and not null
list - the list to decorate, must be empty and not null
Returns:
a new ordered set
Throws:
IllegalArgumentException - if set or list is null
IllegalArgumentException - if either the set or list is not empty
Since:
4.0

listOrderedSet

public static <E> ListOrderedSet<E> listOrderedSet(Set<E> set)
Factory method to create an ordered set.

An ArrayList is used to retain order.

Type Parameters:
E - the element type
Parameters:
set - the set to decorate, must not be null
Returns:
a new ordered set
Throws:
IllegalArgumentException - if set is null
Since:
4.0

listOrderedSet

public static <E> ListOrderedSet<E> listOrderedSet(List<E> 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.

Type Parameters:
E - the element type
Parameters:
list - the list to decorate, must not be null
Returns:
a new ordered set
Throws:
IllegalArgumentException - if list is null
Since:
4.0

asList

public List<E> 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 Collection<E>
Specified by:
clear in interface Set<E>
Overrides:
clear in class AbstractCollectionDecorator<E>

iterator

public OrderedIterator<E> iterator()
Specified by:
iterator in interface Iterable<E>
Specified by:
iterator in interface Collection<E>
Specified by:
iterator in interface Set<E>
Overrides:
iterator in class AbstractCollectionDecorator<E>

add

public boolean add(E object)
Specified by:
add in interface Collection<E>
Specified by:
add in interface Set<E>
Overrides:
add in class AbstractCollectionDecorator<E>

addAll

public boolean addAll(Collection<? extends E> coll)
Specified by:
addAll in interface Collection<E>
Specified by:
addAll in interface Set<E>
Overrides:
addAll in class AbstractCollectionDecorator<E>

remove

public boolean remove(Object object)
Specified by:
remove in interface Collection<E>
Specified by:
remove in interface Set<E>
Overrides:
remove in class AbstractCollectionDecorator<E>

removeAll

public boolean removeAll(Collection<?> coll)
Specified by:
removeAll in interface Collection<E>
Specified by:
removeAll in interface Set<E>
Overrides:
removeAll in class AbstractCollectionDecorator<E>

retainAll

public boolean retainAll(Collection<?> coll)
Specified by:
retainAll in interface Collection<E>
Specified by:
retainAll in interface Set<E>
Overrides:
retainAll in class AbstractCollectionDecorator<E>

toArray

public Object[] toArray()
Specified by:
toArray in interface Collection<E>
Specified by:
toArray in interface Set<E>
Overrides:
toArray in class AbstractCollectionDecorator<E>

toArray

public <T> T[] toArray(T[] a)
Specified by:
toArray in interface Collection<E>
Specified by:
toArray in interface Set<E>
Overrides:
toArray in class AbstractCollectionDecorator<E>

get

public E get(int index)
Returns the element at the specified position in this ordered set.

Parameters:
index - the position of the element in the ordered Set.
Returns:
the element at position index
See Also:
List.get(int)

indexOf

public int indexOf(Object object)
Returns the index of the first occurrence of the specified element in ordered set.

Parameters:
object - the element to search for
Returns:
the index of the first occurrence of the object, or -1 if this ordered set does not contain this object
See Also:
List.indexOf(Object)

add

public void add(int index,
                E object)
Inserts the specified element at the specified position if it is not yet contained in this ordered set (optional operation). Shifts the element currently at this position and any subsequent elements to the right.

Parameters:
index - the index at which the element is to be inserted
object - the element to be inserted
See Also:
List.add(int, Object)

addAll

public boolean addAll(int index,
                      Collection<? extends E> coll)
Inserts all elements in the specified collection not yet contained in the ordered set at the specified position (optional operation). Shifts the element currently at the position and all subsequent elements to the right.

Parameters:
index - the position to insert the elements
coll - the collection containing the elements to be inserted
Returns:
true if this ordered set changed as a result of the call
See Also:
List.addAll(int, Collection)

remove

public Object remove(int index)
Removes the element at the specified position from the ordered set. Shifts any subsequent elements to the left.

Parameters:
index - the index of the element to be removed
Returns:
the element that has been remove from the ordered set
See Also:
List.remove(int)

toString

public 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<E>
Returns:
a string representation of the ordered set


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