ArraySet
public
final
class
ArraySet
extends Object
implements
Collection<E>,
Set<E>
| java.lang.Object | |
| ↳ | android.support.v4.util.ArraySet<E> |
ArraySet is a generic set data structure that is designed to be more memory efficient than a
traditional HashSet. The design is very similar to
ArrayMap, with all of the caveats described there. This implementation is
separate from ArrayMap, however, so the Object array contains only one item for each
entry in the set (instead of a pair for a mapping).
Note that this implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashSet, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.
Because this container is intended to better balance memory use, unlike most other standard Java containers it will shrink its array as items are removed from it. Currently you have no control over this shrinking -- if you set a capacity and then remove an item, it may reduce the capacity to better match the current size. In the future an explicit call to set the capacity should turn off this aggressive shrinking behavior.
Summary
Public constructors | |
|---|---|
ArraySet()
Create a new empty ArraySet. |
|
ArraySet(int capacity)
Create a new ArraySet with a given initial capacity. |
|
ArraySet(ArraySet<E> set)
Create a new ArraySet with the mappings from the given ArraySet. |
|
ArraySet(Collection<E> set)
Create a new ArraySet with the mappings from the given |
|
Public methods | |
|---|---|
boolean
|
add(E value)
Adds the specified object to this set. |
boolean
|
addAll(Collection<? extends E> collection)
Perform an |
void
|
addAll(ArraySet<? extends E> array)
Perform a |
void
|
clear()
Make the array map empty. |
boolean
|
contains(Object key)
Check whether a value exists in the set. |
boolean
|
containsAll(Collection<?> collection)
Determine if the array set contains all of the values in the given collection. |
void
|
ensureCapacity(int minimumCapacity)
Ensure the array map can hold at least minimumCapacity items. |
boolean
|
equals(Object object)
This implementation returns false if the object is not a set, or if the sets have different sizes. |
int
|
hashCode()
|
int
|
indexOf(Object key)
Returns the index of a value in the set. |
boolean
|
isEmpty()
Return true if the array map contains no items. |
Iterator<E>
|
iterator()
Return an |
boolean
|
remove(Object object)
Removes the specified object from this set. |
boolean
|
removeAll(Collection<?> collection)
Remove all values in the array set that exist in the given collection. |
boolean
|
removeAll(ArraySet<? extends E> array)
Perform a |
E
|
removeAt(int index)
Remove the key/value mapping at the given index. |
boolean
|
retainAll(Collection<?> collection)
Remove all values in the array set that do not exist in the given collection. |
int
|
size()
Return the number of items in this array map. |
<T>
T[]
|
toArray(T[] array)
|
Object[]
|
toArray()
|
String
|
toString()
This implementation composes a string by iterating over its values. |
E
|
valueAt(int index)
Return the value at the given index in the array. |
Inherited methods | |
|---|---|
From
class
java.lang.Object
| |
From
interface
java.util.Collection
| |
From
interface
java.util.Set
| |
From
interface
java.lang.Iterable
| |
Public constructors
ArraySet
ArraySet ()
Create a new empty ArraySet. The default capacity of an array map is 0, and will grow once items are added to it.
ArraySet
ArraySet (int capacity)
Create a new ArraySet with a given initial capacity.
| Parameters | |
|---|---|
capacity |
int |
ArraySet
ArraySet (ArraySet<E> set)
Create a new ArraySet with the mappings from the given ArraySet.
| Parameters | |
|---|---|
set |
ArraySet |
ArraySet
ArraySet (Collection<E> set)
Create a new ArraySet with the mappings from the given Collection.
| Parameters | |
|---|---|
set |
Collection |
Public methods
add
boolean add (E value)
Adds the specified object to this set. The set is not modified if it already contains the object.
| Parameters | |
|---|---|
value |
E: the object to add. |
| Returns | |
|---|---|
boolean |
true if this set is modified, false otherwise. |
| Throws | |
|---|---|
ClassCastException |
when the class of the object is inappropriate for this set. |
addAll
boolean addAll (Collection<? extends E> collection)
Perform an add(Object) of all values in collection
| Parameters | |
|---|---|
collection |
Collection: The collection whose contents are to be retrieved.
|
| Returns | |
|---|---|
boolean |
|
addAll
void addAll (ArraySet<? extends E> array)
Perform a add(Object) of all values in array
| Parameters | |
|---|---|
array |
ArraySet: The array whose contents are to be retrieved.
|
contains
boolean contains (Object key)
Check whether a value exists in the set.
| Parameters | |
|---|---|
key |
Object: The value to search for. |
| Returns | |
|---|---|
boolean |
Returns true if the value exists, else false. |
containsAll
boolean containsAll (Collection<?> collection)
Determine if the array set contains all of the values in the given collection.
| Parameters | |
|---|---|
collection |
Collection: The collection whose contents are to be checked against. |
| Returns | |
|---|---|
boolean |
Returns true if this array set contains a value for every entry in collection, else returns false. |
ensureCapacity
void ensureCapacity (int minimumCapacity)
Ensure the array map can hold at least minimumCapacity items.
| Parameters | |
|---|---|
minimumCapacity |
int |
equals
boolean equals (Object object)
This implementation returns false if the object is not a set, or if the sets have different sizes. Otherwise, for each value in this set, it checks to make sure the value also exists in the other set. If any value doesn't exist, the method returns false; otherwise, it returns true.
| Parameters | |
|---|---|
object |
Object |
| Returns | |
|---|---|
boolean |
|
hashCode
int hashCode ()
| Returns | |
|---|---|
int |
|
indexOf
int indexOf (Object key)
Returns the index of a value in the set.
| Parameters | |
|---|---|
key |
Object: The value to search for. |
| Returns | |
|---|---|
int |
Returns the index of the value if it exists, else a negative integer. |
isEmpty
boolean isEmpty ()
Return true if the array map contains no items.
| Returns | |
|---|---|
boolean |
|
iterator
Iterator<E> iterator ()
Return an Iterator over all values in the set.
Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects and allocates additional state information associated with the container that will remain for the life of the container.
| Returns | |
|---|---|
Iterator<E> |
|
remove
boolean remove (Object object)
Removes the specified object from this set.
| Parameters | |
|---|---|
object |
Object: the object to remove. |
| Returns | |
|---|---|
boolean |
true if this set was modified, false otherwise.
|
removeAll
boolean removeAll (Collection<?> collection)
Remove all values in the array set that exist in the given collection.
| Parameters | |
|---|---|
collection |
Collection: The collection whose contents are to be used to remove values. |
| Returns | |
|---|---|
boolean |
Returns true if any values were removed from the array set, else false. |
removeAll
boolean removeAll (ArraySet<? extends E> array)
Perform a remove(Object) of all values in array
| Parameters | |
|---|---|
array |
ArraySet: The array whose contents are to be removed.
|
| Returns | |
|---|---|
boolean |
|
removeAt
E removeAt (int index)
Remove the key/value mapping at the given index.
| Parameters | |
|---|---|
index |
int: The desired index, must be between 0 and size()-1. |
| Returns | |
|---|---|
E |
Returns the value that was stored at this index. |
retainAll
boolean retainAll (Collection<?> collection)
Remove all values in the array set that do not exist in the given collection.
| Parameters | |
|---|---|
collection |
Collection: The collection whose contents are to be used to determine which
values to keep. |
| Returns | |
|---|---|
boolean |
Returns true if any values were removed from the array set, else false. |
toString
String toString ()
This implementation composes a string by iterating over its values. If this set contains itself as a value, the string "(this Set)" will appear in its place.
| Returns | |
|---|---|
String |
|
valueAt
E valueAt (int index)
Return the value at the given index in the array.
| Parameters | |
|---|---|
index |
int: The desired index, must be between 0 and size()-1. |
| Returns | |
|---|---|
E |
Returns the value stored at the given index. |