ArraySet
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 | |
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<init>() Create a new empty ArraySet. |
|
Create a new ArraySet with a given initial capacity. |
|
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 |
|
Create a new ArraySet with items from the given array. |
Public methods | |
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Boolean |
add(@Nullable element: E?) Adds the specified object to this set. |
Unit |
Perform a |
Boolean |
addAll(@NonNull elements: Collection<E>) Perform an |
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 |
This implementation returns false if the object is not a set, or if the sets have different sizes. |
Int |
hashCode() |
Int |
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 |
Boolean |
remove(@Nullable element: E?) Removes the specified object from this set. |
Boolean |
Perform a |
Boolean |
removeAll(@NonNull elements: Collection<E>) Remove all values in the array set that exist in the given collection. |
E |
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> | |
String |
toString() This implementation composes a string by iterating over its values. |
E |
Return the value at the given index in the array. |
Properties | |
---|---|
Int |
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(@Nullable set: ArraySet<E>?)
Create a new ArraySet with the mappings from the given ArraySet.
<init>
ArraySet(@Nullable set: MutableCollection<E>?)
Create a new ArraySet with the mappings from the given Collection
.
Public methods
add
fun add(@Nullable element: E?): Boolean
Adds the specified object to this set. The set is not modified if it already contains the object.
Parameters | |
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value |
the object to add. |
Return | |
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Boolean |
true if this set is modified, false otherwise. |
addAll
fun addAll(@NonNull array: ArraySet<out E>): Unit
Perform a add(Object)
of all values in array
Parameters | |
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array |
ArraySet<out E>: The array whose contents are to be retrieved. |
addAll
fun addAll(@NonNull elements: Collection<E>): Boolean
Perform an add(Object)
of all values in collection
Parameters | |
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collection |
The collection whose contents are to be retrieved. |
contains
fun contains(@Nullable element: E?): Boolean
Check whether a value exists in the set.
Parameters | |
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key |
The value to search for. |
Return | |
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Boolean |
Returns true if the value exists, else false. |
containsAll
fun containsAll(@NonNull elements: Collection<E>): Boolean
Determine if the array set contains all of the values in the given collection.
Parameters | |
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collection |
The collection whose contents are to be checked against. |
Return | |
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Boolean |
Returns true if this array set contains a value for every entry in collection, else returns false. |
ensureCapacity
fun ensureCapacity(minimumCapacity: Int): Unit
Ensure the array map can hold at least minimumCapacity items.
equals
fun equals(other: Any?): Boolean
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.
hashCode
fun hashCode(): Int
indexOf
fun indexOf(@Nullable key: Any?): Int
Returns the index of a value in the set.
Parameters | |
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key |
Any?: The value to search for. |
Return | |
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Int |
Returns the index of the value if it exists, else a negative integer. |
iterator
@NonNull fun iterator(): MutableIterator<E>
Return an java.util.Iterator
over all values in the set.
Note: this is aless efficient way to access the array contents compared to looping from 0 until size()
and calling valueAt(int)
.
remove
fun remove(@Nullable element: E?): Boolean
Removes the specified object from this set.
Parameters | |
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object |
the object to remove. |
Return | |
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Boolean |
true if this set was modified, false otherwise. |
removeAll
fun removeAll(@NonNull array: ArraySet<out E>): Boolean
Perform a remove(Object)
of all values in array
Parameters | |
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array |
ArraySet<out E>: The array whose contents are to be removed. |
removeAll
fun