# ArraySet added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) Summary:[Ctors](https://developer.android.com/reference/android/support/v4/util/ArraySet#pubctors)\|[Methods](https://developer.android.com/reference/android/support/v4/util/ArraySet#pubmethods)\|[Inherited Methods](https://developer.android.com/reference/android/support/v4/util/ArraySet#inhmethods)\|[\[Expand All\]](https://developer.android.com/reference/android/support/v4/util/ArraySet#) # ArraySet | This package is part of the Android[support library](https://developer.android.com/topic/libraries/support-library)which is no longer maintained. The support library has been superseded by[AndroidX](https://developer.android.com/jetpack/androidx)which is part of[Jetpack](https://developer.android.com/jetpack). We recommend using the AndroidX libraries in all new projects. You should also consider[migrating](https://developer.android.com/jetpack/androidx/migrate)existing projects to AndroidX. To find the AndroidX class that maps to this deprecated class, see the AndroidX support library[class mappings](https://developer.android.com/jetpack/androidx/migrate/class-mappings). ` public final class ArraySet ` ` extends Object `` implements Collection, Set ` |---|---------------------------------------| | java.lang.Object || | ↳ | android.support.v4.util.ArraySet\ |
*** ** * ** *** ArraySet is a generic set data structure that is designed to be more memory efficient than a traditional[HashSet](https://developer.android.com/reference/java/util/HashSet). The design is very similar to[ArrayMap](https://developer.android.com/reference/android/support/v4/util/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](https://developer.android.com/reference/android/support/v4/util/ArraySet#ArraySet())`() ` Create a new empty ArraySet. | | ` `[ArraySet](https://developer.android.com/reference/android/support/v4/util/ArraySet#ArraySet(int))`(int capacity) ` Create a new ArraySet with a given initial capacity. | | ` `[ArraySet](https://developer.android.com/reference/android/support/v4/util/ArraySet#ArraySet(android.support.v4.util.ArraySet))`(`[ArraySet](https://developer.android.com/reference/android/support/v4/util/ArraySet)` set) ` Create a new ArraySet with the mappings from the given ArraySet. | | ` `[ArraySet](https://developer.android.com/reference/android/support/v4/util/ArraySet#ArraySet(java.util.Collection))`(Collection set) ` Create a new ArraySet with the mappings from the given[Collection](https://developer.android.com/reference/java/util/Collection). | | ### Public methods || |----------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` boolean` | ` `[add](https://developer.android.com/reference/android/support/v4/util/ArraySet#add(E))`(E value) ` Adds the specified object to this set. | | ` boolean` | ` `[addAll](https://developer.android.com/reference/android/support/v4/util/ArraySet#addAll(java.util.Collection))`(Collection collection) ` Perform an[add(Object)](https://developer.android.com/reference/android/support/v4/util/ArraySet#add(E))of all values incollection | | ` void` | ` `[addAll](https://developer.android.com/reference/android/support/v4/util/ArraySet#addAll(android.support.v4.util.ArraySet))`(`[ArraySet](https://developer.android.com/reference/android/support/v4/util/ArraySet)` array) ` Perform a[add(Object)](https://developer.android.com/reference/android/support/v4/util/ArraySet#add(E))of all values inarray | | ` void` | ` `[clear](https://developer.android.com/reference/android/support/v4/util/ArraySet#clear())`() ` Make the array map empty. | | ` boolean` | ` `[contains](https://developer.android.com/reference/android/support/v4/util/ArraySet#contains(java.lang.Object))`(Object key) ` Check whether a value exists in the set. | | ` boolean` | ` `[containsAll](https://developer.android.com/reference/android/support/v4/util/ArraySet#containsAll(java.util.Collection))`(Collection collection) ` Determine if the array set contains all of the values in the given collection. | | ` void` | ` `[ensureCapacity](https://developer.android.com/reference/android/support/v4/util/ArraySet#ensureCapacity(int))`(int minimumCapacity) ` Ensure the array map can hold at leastminimumCapacityitems. | | ` boolean` | ` `[equals](https://developer.android.com/reference/android/support/v4/util/ArraySet#equals(java.lang.Object))`(Object object) `
This implementation returns false if the object is not a set, or if the sets have different sizes. | | ` int` | ` `[hashCode](https://developer.android.com/reference/android/support/v4/util/ArraySet#hashCode())`() `
| | ` int` | ` `[indexOf](https://developer.android.com/reference/android/support/v4/util/ArraySet#indexOf(java.lang.Object))`(Object key) ` Returns the index of a value in the set. | | ` boolean` | ` `[isEmpty](https://developer.android.com/reference/android/support/v4/util/ArraySet#isEmpty())`() ` Return true if the array map contains no items. | | ` Iterator` | ` `[iterator](https://developer.android.com/reference/android/support/v4/util/ArraySet#iterator())`() ` Return an[Iterator](https://developer.android.com/reference/java/util/Iterator)over all values in the set. | | ` boolean` | ` `[remove](https://developer.android.com/reference/android/support/v4/util/ArraySet#remove(java.lang.Object))`(Object object) ` Removes the specified object from this set. | | ` boolean` | ` `[removeAll](https://developer.android.com/reference/android/support/v4/util/ArraySet#removeAll(java.util.Collection))`(Collection collection) ` Remove all values in the array set that exist in the given collection. | | ` boolean` | ` `[removeAll](https://developer.android.com/reference/android/support/v4/util/ArraySet#removeAll(android.support.v4.util.ArraySet))`(`[ArraySet](https://developer.android.com/reference/android/support/v4/util/ArraySet)` array) ` Perform a[remove(Object)](https://developer.android.com/reference/android/support/v4/util/ArraySet#remove(java.lang.Object))of all values inarray | | ` E` | ` `[removeAt](https://developer.android.com/reference/android/support/v4/util/ArraySet#removeAt(int))`(int index) ` Remove the key/value mapping at the given index. | | ` boolean` | ` `[retainAll](https://developer.android.com/reference/android/support/v4/util/ArraySet#retainAll(java.util.Collection))`(Collection collection) ` Remove all values in the array set that do**not**exist in the given collection. | | ` int` | ` `[size](https://developer.android.com/reference/android/support/v4/util/ArraySet#size())`() ` Return the number of items in this array map. | | ` T[]` | ` `[toArray](https://developer.android.com/reference/android/support/v4/util/ArraySet#toArray(T[]))`(T[] array) ` | | ` Object[]` | ` `[toArray](https://developer.android.com/reference/android/support/v4/util/ArraySet#toArray())`() ` | | ` String` | ` `[toString](https://developer.android.com/reference/android/support/v4/util/ArraySet#toString())`() `
This implementation composes a string by iterating over its values. | | ` E` | ` `[valueAt](https://developer.android.com/reference/android/support/v4/util/ArraySet#valueAt(int))`(int index) ` Return the value at the given index in the array. | | ### Inherited methods | |-----------------------|---| | [![](https://developer.android.com/static/assets/images/styles/disclosure_down.png)](https://developer.android.com/reference/android/support/v4/util/ArraySet#)From class` java.lang.Object ` |-------------------|-------------------------------| | ` Object` | ` clone() ` | | ` boolean` | ` equals(Object arg0) ` | | ` void` | ` finalize() ` | | ` final Class` | ` getClass() ` | | ` int` | ` hashCode() ` | | ` final void` | ` notify() ` | | ` final void` | ` notifyAll() ` | | ` String` | ` toString() ` | | ` final void` | ` wait(long arg0, int arg1) ` | | ` final void` | ` wait(long arg0) ` | | ` final void` | ` wait() ` | || | [![](https://developer.android.com/static/assets/images/styles/disclosure_down.png)](https://developer.android.com/reference/android/support/v4/util/ArraySet#)From interface` java.util.Collection ` |---------------------------|------------------------------------------| | ` abstract boolean` | ` add(E arg0) ` | | ` abstract boolean` | ` addAll(Collection arg0) ` | | ` abstract void` | ` clear() ` | | ` abstract boolean` | ` contains(Object arg0) ` | | ` abstract boolean` | ` containsAll(Collection arg0) ` | | ` abstract boolean` | ` equals(Object arg0) ` | | ` abstract int` | ` hashCode() ` | | ` abstract boolean` | ` isEmpty() ` | | ` abstract Iterator` | ` iterator() ` | | ` default Stream` | ` parallelStream() ` | | ` abstract boolean` | ` remove(Object arg0) ` | | ` abstract boolean` | ` removeAll(Collection arg0) ` | | ` default boolean` | ` removeIf(Predicate arg0) ` | | ` abstract boolean` | ` retainAll(Collection arg0) ` | | ` abstract int` | ` size() ` | | ` default Spliterator` | ` spliterator() ` | | ` default Stream` | ` stream() ` | | ` abstract T[]` | ` toArray(T[] arg0) ` | | ` abstract Object[]` | ` toArray() ` | || | [![](https://developer.android.com/static/assets/images/styles/disclosure_down.png)](https://developer.android.com/reference/android/support/v4/util/ArraySet#)From interface` java.util.Set ` |---------------------------|------------------------------------------| | ` abstract boolean` | ` add(E arg0) ` | | ` abstract boolean` | ` addAll(Collection arg0) ` | | ` abstract void` | ` clear() ` | | ` abstract boolean` | ` contains(Object arg0) ` | | ` abstract boolean` | ` containsAll(Collection arg0) ` | | ` abstract boolean` | ` equals(Object arg0) ` | | ` abstract int` | ` hashCode() ` | | ` abstract boolean` | ` isEmpty() ` | | ` abstract Iterator` | ` iterator() ` | | ` abstract boolean` | ` remove(Object arg0) ` | | ` abstract boolean` | ` removeAll(Collection arg0) ` | | ` abstract boolean` | ` retainAll(Collection arg0) ` | | ` abstract int` | ` size() ` | | ` default Spliterator` | ` spliterator() ` | | ` abstract T[]` | ` toArray(T[] arg0) ` | | ` abstract Object[]` | ` toArray() ` | || | [![](https://developer.android.com/static/assets/images/styles/disclosure_down.png)](https://developer.android.com/reference/android/support/v4/util/ArraySet#)From interface` java.lang.Iterable ` |---------------------------|---------------------------------------| | ` default void` | ` forEach(Consumer arg0) ` | | ` abstract Iterator` | ` iterator() ` | | ` default Spliterator` | ` spliterator() ` | || ## Public constructors ### ArraySet added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` ArraySet (int capacity) ``` Create a new ArraySet with a given initial capacity.
| Parameters || |------------|--------------| | `capacity` | `int`
| ### ArraySet added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` ArraySet (ArraySet set) ``` Create a new ArraySet with the mappings from the given ArraySet.
| Parameters || |-------|-------------------| | `set` | `ArraySet`
| ### ArraySet added in[version 27.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` ArraySet (Collection set) ``` Create a new ArraySet with the mappings from the given[Collection](https://developer.android.com/reference/java/util/Collection).
| Parameters || |-------|---------------------| | `set` | `Collection`
| ## Public methods ### add added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` boolean addAll (Collection collection) ``` Perform an[add(Object)](https://developer.android.com/reference/android/support/v4/util/ArraySet#add(E))of all values incollection
| Parameters || |--------------|-------------------------------------------------------------------------| | `collection` | `Collection`: The collection whose contents are to be retrieved.
| | Returns || |-----------|--------| | `boolean` |
| ### addAll added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` void addAll (ArraySet array) ``` Perform a[add(Object)](https://developer.android.com/reference/android/support/v4/util/ArraySet#add(E))of all values inarray
| Parameters || |---------|------------------------------------------------------------------| | `array` | `ArraySet`: The array whose contents are to be retrieved.
| ### clear added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` void clear () ``` Make the array map empty. All storage is released.
### contains added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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 incollection, else returns false.
| ### ensureCapacity added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` void ensureCapacity (int minimumCapacity) ``` Ensure the array map can hold at leastminimumCapacityitems.
| 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` boolean isEmpty () ``` Return true if the array map contains no items.
| Returns || |-----------|--------| | `boolean` |
| ### iterator added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` Iterator iterator () ``` Return an[Iterator](https://developer.android.com/reference/java/util/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` |
| ### remove added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` boolean removeAll (ArraySet array) ``` Perform a[remove(Object)](https://developer.android.com/reference/android/support/v4/util/ArraySet#remove(java.lang.Object))of all values inarray
| Parameters || |---------|----------------------------------------------------------------| | `array` | `ArraySet`: The array whose contents are to be removed.
| | Returns || |-----------|--------| | `boolean` |
| ### removeAt added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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()](https://developer.android.com/reference/android/support/v4/util/ArraySet#size())-1.
| | Returns || |-----|---------------------------------------------------------| | `E` | Returns the value that was stored at this index.
| ### retainAll added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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.
| ### size added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` int size () ``` Return the number of items in this array map.
| Returns || |-------|--------| | `int` |
| ### toArray added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` T[] toArray (T[] array) ```

| Parameters || |---------|------------| | `array` | `T`
| | Returns || |-------|--------| | `T[]` |
| ### toArray added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` Object[] toArray () ```

| Returns || |------------|--------| | `Object[]` |
| ### 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 added in[version 25.1.0](https://developer.android.com/topic/libraries/support-library/revisions) ``` 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()](https://developer.android.com/reference/android/support/v4/util/ArraySet#size())-1.
| | Returns || |-----|-----------------------------------------------------| | `E` | Returns the value stored at the given index.
| - ## Interfaces - [Pools.Pool](https://developer.android.com/reference/android/support/v4/util/Pools.Pool) - ## Classes - [ArrayMap](https://developer.android.com/reference/android/support/v4/util/ArrayMap) - [ArraySet](https://developer.android.com/reference/android/support/v4/util/ArraySet) - [AtomicFile](https://developer.android.com/reference/android/support/v4/util/AtomicFile) - [CircularArray](https://developer.android.com/reference/android/support/v4/util/CircularArray) - [CircularIntArray](https://developer.android.com/reference/android/support/v4/util/CircularIntArray) - [LongSparseArray](https://developer.android.com/reference/android/support/v4/util/LongSparseArray) - [LruCache](https://developer.android.com/reference/android/support/v4/util/LruCache) - [ObjectsCompat](https://developer.android.com/reference/android/support/v4/util/ObjectsCompat) - [Pair](https://developer.android.com/reference/android/support/v4/util/Pair) - [PatternsCompat](https://developer.android.com/reference/android/support/v4/util/PatternsCompat) - [Pools](https://developer.android.com/reference/android/support/v4/util/Pools) - [Pools.SimplePool](https://developer.android.com/reference/android/support/v4/util/Pools.SimplePool) - [Pools.SynchronizedPool](https://developer.android.com/reference/android/support/v4/util/Pools.SynchronizedPool) - [SimpleArrayMap](https://developer.android.com/reference/android/support/v4/util/SimpleArrayMap) - [SparseArrayCompat](https://developer.android.com/reference/android/support/v4/util/SparseArrayCompat)