ArraySet

Kotlin |Java

class ArraySet<E : Any!> : MutableCollection<E>, MutableSet<E>

kotlin.Any
↳	androidx.collection.ArraySet

ArraySet is a generic set data structure that is designed to be more memory efficient than a traditional java.util.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.

This structure is NOT thread-safe.

Summary

Public constructors
`<init>()` Create a new empty ArraySet.
`<init>(capacity: Int)` Create a new ArraySet with a given initial capacity.
`<init>(@Nullable set: ArraySet<E>?)` Create a new ArraySet with the mappings from the given ArraySet.
`<init>(@Nullable set: MutableCollection<E>?)` Create a new ArraySet with the mappings from the given `Collection`.
`<init>(@Nullable array: Array<E>?)` Create a new ArraySet with items from the given array.

Public methods
Boolean	`add(@Nullable element: E?)` Adds the specified object to this set.
Unit	`addAll(@NonNull array: ArraySet<out E>)` Perform a `add(Object)` of all values in array
Boolean	`addAll(@NonNull elements: Collection<E>)` Perform an `add(Object)` of all values in collection
Unit	`clear()` Make the array map empty.
Boolean	`contains(@Nullable element: E?)` Check whether a value exists in the set.
Boolean	`containsAll(@NonNull elements: Collection<E>)` Determine if the array set contains all of the values in the given collection.
Unit	`ensureCapacity(minimumCapacity: Int)` Ensure the array map can hold at least minimumCapacity items.
Boolean	`equals(other: Any?)` This implementation returns false if the object is not a set, or if the sets have different sizes.
Int	`hashCode()`
Int	`indexOf(@Nullable key: Any?)` Returns the index of a value in the set.
Boolean	`isEmpty()` Return true if the array map contains no items.
MutableIterator<E>	`iterator()` Return an `java.util.Iterator` over all values in the set.
Boolean	`remove(@Nullable element: E?)` Removes the specified object from this set.
Boolean	`removeAll(@NonNull array: ArraySet<out E>)` Perform a `remove(Object)` of all values in array
Boolean	`removeAll(@NonNull elements: Collection<E>)` Remove all values in the array set that exist in the given collection.
E	`removeAt(index: Int)` Remove the key/value mapping at the given index.
Boolean	`retainAll(@NonNull elements: Collection<E>)` Remove all values in the array set that do not exist in the given collection.
Array<Any!>	`toArray()`
Array<T>	`toArray(@NonNull array: Array<T>)`
String	`toString()` This implementation composes a string by iterating over its values.
E	`valueAt(index: Int)` Return the value at the given index in the array.

Properties
Int	`size` Return the number of items in this array map.

Public constructors

<init>

ArraySet()

Create a new empty ArraySet. The default capacity of an array map is 0, and will grow once items are added to it.

<init>

ArraySet(capacity: Int)

Create a new ArraySet with a given initial capacity.

<init>

ArraySet(@Nullable set: ArraySet<E>?)