Class ListOrderedSet<E>
- Type Parameters:
E
- the type of the elements in this set
- All Implemented Interfaces:
Serializable
,Iterable<E>
,Collection<E>
,Set<E>
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
- See Also:
-
Constructor Summary
ModifierConstructorDescriptionConstructs a new emptyListOrderedSet
using aHashSet
and anArrayList
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
Modifier and TypeMethodDescriptionvoid
Inserts the specified element at the specified position if it is not yet contained in this ordered set (optional operation).boolean
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).boolean
addAll
(Collection<? extends E> coll) asList()
Gets an unmodifiable view of the order of the Set.void
clear()
get
(int index) Returns the element at the specified position in this ordered set.int
Returns the index of the first occurrence of the specified element in ordered set.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.remove
(int index) Removes the element at the specified position from the ordered set.boolean
boolean
removeAll
(Collection<?> coll) boolean
boolean
retainAll
(Collection<?> coll) Object[]
toArray()
<T> T[]
toArray
(T[] a) toString()
Uses the underlying List's toString so that order is achieved.Methods inherited from class org.apache.commons.collections4.set.AbstractSetDecorator
decorated, equals, hashCode
Methods inherited from class org.apache.commons.collections4.collection.AbstractCollectionDecorator
contains, containsAll, isEmpty, setCollection, size
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.Collection
parallelStream, stream
Methods inherited from interface java.util.Set
contains, containsAll, isEmpty, size, spliterator
-
Constructor Details
-
ListOrderedSet
public ListOrderedSet()Constructs a new emptyListOrderedSet
using aHashSet
and anArrayList
internally.- Since:
- 3.1
-
ListOrderedSet
Constructor that wraps (not copies).- Parameters:
set
- the set to decorate, must not be null- Throws:
NullPointerException
- if set is null
-
ListOrderedSet
Constructor that wraps (not copies) the Set and specifies the list to use.The set and list must both be correctly initialized to the same elements.
- Parameters:
set
- the set to decorate, must not be nulllist
- the list to decorate, must not be null- Throws:
NullPointerException
- if set or list is null
-
-
Method Details
-
listOrderedSet
Factory method to create an ordered set using the supplied list to retain order.A
HashSet
is used for the set behavior.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:
NullPointerException
- if list is null- Since:
- 4.0
-
listOrderedSet
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:
NullPointerException
- if set is null- Since:
- 4.0
-
listOrderedSet
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 nulllist
- the list to decorate, must be empty and not null- Returns:
- a new ordered set
- Throws:
NullPointerException
- if set or list is nullIllegalArgumentException
- if either the set or list is not empty- Since:
- 4.0
-
add
- Specified by:
add
in interfaceCollection<E>
- Specified by:
add
in interfaceSet<E>
- Overrides:
add
in classAbstractCollectionDecorator<E>
-
add
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 insertedobject
- the element to be inserted- See Also:
-
addAll
- Specified by:
addAll
in interfaceCollection<E>
- Specified by:
addAll
in interfaceSet<E>
- Overrides:
addAll
in classAbstractCollectionDecorator<E>
-
addAll
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 elementscoll
- the collection containing the elements to be inserted- Returns:
true
if this ordered set changed as a result of the call- See Also:
-
asList
Gets an unmodifiable view of the order of the Set.- Returns:
- an unmodifiable list view
-
clear
- Specified by:
clear
in interfaceCollection<E>
- Specified by:
clear
in interfaceSet<E>
- Overrides:
clear
in classAbstractCollectionDecorator<E>
-
get
Returns the element at the specified position in this ordered set.- Parameters:
index
- the position of the element in the orderedSet
.- Returns:
- the element at position
index
- See Also:
-
indexOf
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:
-
iterator
-
remove
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:
-
remove
- Specified by:
remove
in interfaceCollection<E>
- Specified by:
remove
in interfaceSet<E>
- Overrides:
remove
in classAbstractCollectionDecorator<E>
-
removeAll
- Specified by:
removeAll
in interfaceCollection<E>
- Specified by:
removeAll
in interfaceSet<E>
- Overrides:
removeAll
in classAbstractCollectionDecorator<E>
-
removeIf
- Specified by:
removeIf
in interfaceCollection<E>
- Overrides:
removeIf
in classAbstractCollectionDecorator<E>
- Since:
- 4.4
-
retainAll
This implementation iterates over the elements of this set, checking each element in turn to see if it's contained in
coll
. If it's not contained, it's removed from this set. As a consequence, it is advised to use a collection type forcoll
that provides a fast (e.g. O(1)) implementation ofCollection.contains(Object)
.- Specified by:
retainAll
in interfaceCollection<E>
- Specified by:
retainAll
in interfaceSet<E>
- Overrides:
retainAll
in classAbstractCollectionDecorator<E>
-
toArray
- Specified by:
toArray
in interfaceCollection<E>
- Specified by:
toArray
in interfaceSet<E>
- Overrides:
toArray
in classAbstractCollectionDecorator<E>
-
toArray
- Specified by:
toArray
in interfaceCollection<E>
- Specified by:
toArray
in interfaceSet<E>
- Overrides:
toArray
in classAbstractCollectionDecorator<E>
-
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 classAbstractCollectionDecorator<E>
- Returns:
- a string representation of the ordered set
-