ObjectList

Artifact: androidx.collection:collection

View Source

Added in 1.4.0

Kotlin |Java

Cmn
```
sealed class ObjectList<E : Any?>
```

Known direct subclasses

MutableObjectList

MutableObjectList

MutableObjectList is a MutableList-like collection for reference types.

ObjectList is a List-like collection for reference types. It is optimized for fast access, avoiding virtual and interface method access. Methods avoid allocation whenever possible. For example forEach does not need allocate an Iterator.

This implementation is not thread-safe: if multiple threads access this container concurrently, and one or more threads modify the structure of the list (insertion or removal for instance), the calling code must provide the appropriate synchronization. It is also not safe to mutate during reentrancy -- in the middle of a forEach, for example. However, concurrent reads are safe.

Note List access is available through asList when developers need access to the common API.

It is best to use this for all internal implementations where a list of reference types is needed. Use List in public API to take advantage of the commonly-used interface. It is common to use ObjectList internally and use asList to get a List interface for interacting with public APIs.

LongList

See also
`MutableObjectList`
`FloatList`
`IntList`

Summary

Protected constructors
`<E : Any?> ObjectList(initialCapacity: Int)`	Cmn

Public functions
`Boolean`	`any()` Returns `true` if there's at least one element in the collection.	Cmn
`inline Boolean`	`any(predicate: (element) -> Boolean)` Returns `true` if any of the elements give a `true` return value for `predicate`.	Cmn
`abstract List<E>`	`asList()` Returns a `List` view into the `ObjectList`.	Cmn
`operator Boolean`	`contains(element: E)` Returns `true` if the `ObjectList` contains `element` or `false` otherwise.	Cmn
`Boolean`	`containsAll(elements: Array<E>)` Returns `true` if the `ObjectList` contains all elements in `elements` or `false` if one or more are missing.	Cmn
`Boolean`	`containsAll(elements: Iterable<E>)` Returns `true` if the `ObjectList` contains all elements in `elements` or `false` if one or more are missing.	Cmn
`Boolean`	`containsAll(elements: List<E>)` Returns `true` if the `ObjectList` contains all elements in `elements` or `false` if one or more are missing.	Cmn
`Boolean`	`containsAll(elements: ObjectList<E>)` Returns `true` if the `ObjectList` contains all elements in `elements` or `false` if one or more are missing.	Cmn
`Int`	`count()` Returns the number of elements in this list.	Cmn
`inline Int`	`count(predicate: (element) -> Boolean)` Counts the number of elements matching `predicate`.	Cmn
`E`	`elementAt(index: @IntRange(from = 0) Int)` Returns the element at the given `index` or throws `IndexOutOfBoundsException` if the `index` is out of bounds of this collection.	Cmn
`inline E`	`elementAtOrElse(index: @IntRange(from = 0) Int, defaultValue: (index: Int) -> E)` Returns the element at the given `index` or `defaultValue` if `index` is out of bounds of the collection.	Cmn
`open operator Boolean`	`equals(other: Any?)` Returns `true` if `other` is a `ObjectList` and the contents of this and `other` are the same.	Cmn
`E`	`first()` Returns the first element in the `ObjectList` or throws a `NoSuchElementException` if it `isEmpty`.	Cmn
`inline E`	`first(predicate: (element) -> Boolean)` Returns the first element in the `ObjectList` for which `predicate` returns `true` or throws `NoSuchElementException` if nothing matches.	Cmn
`inline E?`	`firstOrNull()` Returns the first element in the `ObjectList` or `null` if it `isEmpty`.	Cmn
`inline E?`	`firstOrNull(predicate: (element) -> Boolean)` Returns the first element in the `ObjectList` for which `predicate` returns `true` or `null` if nothing matches.	Cmn
`inline R`	`<R : Any?> fold(initial: R, operation: (acc, element) -> R)` Accumulates values, starting with `initial`, and applying `operation` to each element in the `ObjectList` in order.	Cmn
`inline R`	`<R : Any?> foldIndexed(initial: R, operation: (index: Int, acc, element) -> R)` Accumulates values, starting with `initial`, and applying `operation` to each element in the `ObjectList` in order.	Cmn
`inline R`	`<R : Any?> foldRight(initial: R, operation: (element, acc) -> R)` Accumulates values, starting with `initial`, and applying `operation` to each element in the `ObjectList` in reverse order.	Cmn
`inline R`	`<R : Any?> foldRightIndexed(initial: R, operation: (index: Int, element, acc) -> R)` Accumulates values, starting with `initial`, and applying `operation` to each element in the `ObjectList` in reverse order.	Cmn
`inline Unit`	`forEach(block: (element) -> Unit)` Calls `block` for each element in the `ObjectList`, in order.	Cmn
`inline Unit`	`forEachIndexed(block: (index: Int, element) -> Unit)` Calls `block` for each element in the `ObjectList` along with its index, in order.	Cmn
`inline Unit`	`forEachReversed(block: (element) -> Unit)` Calls `block` for each element in the `ObjectList` in reverse order.	Cmn
`inline Unit`	`forEachReversedIndexed(block: (index: Int, element) -> Unit)` Calls `block` for each element in the `ObjectList` along with its index, in reverse order.	Cmn
`operator E`	`get(index: @IntRange(from = 0) Int)` Returns the element at the given `index` or throws `IndexOutOfBoundsException` if the `index` is out of bounds of this collection.	Cmn
`open Int`	`hashCode()` Returns a hash code based on the contents of the `ObjectList`.	Cmn
`Int`	`indexOf(element: E)` Returns the index of `element` in the `ObjectList` or `-1` if `element` is not there.	Cmn
`inline Int`	`indexOfFirst(predicate: (element) -> Boolean)` Returns the index if the first element in the `ObjectList` for which `predicate` returns `true` or -1 if there was no element for which predicate returned `true`.	Cmn
`inline Int`	`indexOfLast(predicate: (element) -> Boolean)` Returns the index if the last element in the `ObjectList` for which `predicate` returns `true` or -1 if there was no element for which predicate returned `true`.	Cmn
`Boolean`	`isEmpty()` Returns `true` if the `ObjectList` has no elements in it or `false` otherwise.	Cmn
`Boolean`	`isNotEmpty()` Returns `true` if there are elements in the `ObjectList` or `false` if it is empty.	Cmn
`String`	`joinToString( separator: CharSequence, prefix: CharSequence, postfix: CharSequence, limit: Int, truncated: CharSequence, transform: ((E) -> CharSequence)? )` Creates a String from the elements separated by `separator` and using `prefix` before and `postfix` after, if supplied.	Cmn
`E`	`last()` Returns the last element in the `ObjectList` or throws a `NoSuchElementException` if it `isEmpty`.	Cmn
`inline E`	`last(predicate: (element) -> Boolean)` Returns the last element in the `ObjectList` for which `predicate` returns `true` or throws `NoSuchElementException` if nothing matches.	Cmn
`Int`	`lastIndexOf(element: E)` Returns the index of the last element in the `ObjectList` that is the same as `element` or `-1` if no elements match.	Cmn
`inline E?`	`lastOrNull()` Returns the last element in the `ObjectList` or `null` if it `isEmpty`.	Cmn
`inline E?`	`lastOrNull(predicate: (element) -> Boolean)` Returns the last element in the `ObjectList` for which `predicate` returns `true` or `null` if nothing matches.	Cmn
`Boolean`	`none()` Returns `true` if the collection has no elements in it.	Cmn
`inline Boolean`	`reversedAny(predicate: (element) -> Boolean)` Returns `true` if any of the elements give a `true` return value for `predicate` while iterating in the reverse order.	Cmn
`open String`	`toString()` Returns a String representation of the list, surrounded by "[]" and each element separated by ", ".	Cmn

Public properties
`IntRange`	`indices` Returns an `IntRange` of the valid indices for this `ObjectList`.	Cmn
`Int`	`lastIndex` Returns the last valid index in the `ObjectList`.	Cmn
`Int`	`size` The number of elements in the `ObjectList`.	Cmn

Protected constructors

ObjectList

Cmn

protected <E : Any?> ObjectList(initialCapacity: Int)

Public functions

any

Cmn

Added in 1.4.0

fun any(): Boolean

Returns true if there's at least one element in the collection.

any

Cmn

Added in 1.4.0

inline fun any(predicate: (element) -> Boolean): Boolean

Returns true if any of the elements give a true return value for predicate.

asList

Cmn

Added in 1.4.0

abstract fun asList(): List<E>

Returns a List view into the ObjectList. All access to the collection will be less efficient and abides by the allocation requirements of the List. For example, List.forEach will allocate an iterator. All access will go through the more expensive interface calls. Critical performance areas should use the ObjectList API rather than List API, when possible.

contains

Cmn

Added in 1.4.0

operator fun contains(element: E): Boolean

Returns true if the ObjectList contains element or false otherwise.

containsAll

Cmn

Added in 1.4.0

fun containsAll(elements: Array<E>): Boolean

Returns true if the ObjectList contains all elements in elements or false if one or more are missing.

containsAll

Cmn

fun containsAll(elements: Iterable<E>): Boolean

Returns true if the ObjectList contains all elements in elements or false if one or more are missing.

containsAll

Cmn

fun containsAll(elements: List<E>): Boolean

Returns true if the ObjectList contains all elements in elements or false if one or more are missing.

containsAll

Cmn

Added in 1.4.0

fun containsAll(elements: ObjectList<E>): Boolean

Returns true if the ObjectList contains all elements in elements or false if one or more are missing.

count

Cmn

Added in 1.4.0

fun count(): Int

Returns the number of elements in this list.

count

Cmn

Added in 1.4.0

inline fun count(predicate: (element) -> Boolean): Int

Counts the number of elements matching predicate.

Returns
`Int`	The number of elements in this list for which `predicate` returns true.

elementAt

Cmn

Added in 1.4.0

fun elementAt(index: @IntRange(from = 0) Int): E

Returns the element at the given index or throws IndexOutOfBoundsException if the index is out of bounds of this collection.

elementAtOrElse

Cmn

Added in 1.4.0

inline fun elementAtOrElse(index: @IntRange(from = 0) Int, defaultValue: (index: Int) -> E): E

Returns the element at the given index or defaultValue if index is out of bounds of the collection.

Parameters
`index: Int`	The index of the element whose value should be returned
`defaultValue: (index: Int) -> E`	A lambda to call with `index` as a parameter to return a value at an index not in the list.

equals

Cmn

open operator fun equals(other: Any?): Boolean

Returns true if other is a ObjectList and the contents of this and other are the same.

first

Cmn

Added in 1.4.0

fun first(): E

Returns the first element in the ObjectList or throws a NoSuchElementException if it isEmpty.

first

Cmn

Added in 1.4.0

inline fun first(predicate: (element) -> Boolean): E

Returns the first element in the ObjectList for which predicate returns true or throws NoSuchElementException if nothing matches.

See also
`indexOfFirst`
`firstOrNull`

firstOrNull

Cmn

Added in 1.4.0

inline fun firstOrNull(): E?

Returns the first element in the ObjectList or null if it isEmpty.

firstOrNull

Cmn

Added in 1.4.0

inline fun firstOrNull(predicate: (element) -> Boolean): E?

Returns the first element in the ObjectList for which predicate returns true or null if nothing matches.

See also
`indexOfFirst`

fold

Cmn

Added in 1.4.0

inline fun <R : Any?> fold(initial: R, operation: (acc, element) -> R): R

Accumulates values, starting with initial, and applying operation to each element in the ObjectList in order.

Parameters
`initial: R`	The value of `acc` for the first call to `operation` or return value if there are no elements in this list.
`operation: (acc, element) -> R`	function that takes current accumulator value and an element, and calculates the next accumulator value.

foldIndexed

Cmn

Added in 1.4.0

inline fun <R : Any?> foldIndexed(initial: R, operation: (index: Int, acc, element) -> R): R

Accumulates values, starting with initial, and applying operation to each element in the ObjectList in order.

foldRight

Cmn

Added in 1.4.0

inline fun <R : Any?> foldRight(initial: R, operation: (element, acc) -> R): R

Accumulates values, starting with initial, and applying operation to each element in the ObjectList in reverse order.

Parameters
`initial: R`	The value of `acc` for the first call to `operation` or return value if there are no elements in this list.
`operation: (element, acc) -> R`	function that takes an element and the current accumulator value, and calculates the next accumulator value.

foldRightIndexed

Cmn

Added in 1.4.0

inline fun <R : Any?> foldRightIndexed(initial: R, operation: (index: Int, element, acc) -> R): R

Accumulates values, starting with initial, and applying operation to each element in the ObjectList in reverse order.

forEach

Cmn

Added in 1.4.0

inline fun forEach(block: (element) -> Unit): Unit

Calls block for each element in the ObjectList, in order.

Parameters
`block: (element) -> Unit`	will be executed for every element in the list, accepting an element from the list

forEachIndexed

Cmn

Added in 1.4.0

inline fun forEachIndexed(block: (index: Int, element) -> Unit): Unit

Calls block for each element in the ObjectList along with its index, in order.

Parameters
`block: (index: Int, element) -> Unit`	will be executed for every element in the list, accepting the index and the element at that index.

forEachReversed

Cmn

Added in 1.4.0

inline fun forEachReversed(block: (element) -> Unit): Unit

Calls block for each element in the ObjectList in reverse order.

Parameters
`block: (element) -> Unit`	will be executed for every element in the list, accepting an element from the list

forEachReversedIndexed

Cmn

Added in 1.4.0

inline fun forEachReversedIndexed(block: (index: Int, element) -> Unit): Unit

Calls block for each element in the ObjectList along with its index, in reverse order.

Parameters
`block: (index: Int, element) -> Unit`	will be executed for every element in the list, accepting the index and the element at that index.

get

Cmn

Added in 1.4.0

operator fun get(index: @IntRange(from = 0) Int): E

Returns the element at the given index or throws IndexOutOfBoundsException if the index is out of bounds of this collection.

hashCode

Cmn

open fun hashCode(): Int

Returns a hash code based on the contents of the ObjectList.

indexOf

Cmn

Added in 1.4.0

fun indexOf(element: E): Int

Returns the index of element in the ObjectList or -1 if element is not there.

indexOfFirst

Cmn

Added in 1.4.0

inline fun indexOfFirst(predicate: (element) -> Boolean): Int

Returns the index if the first element in the ObjectList for which predicate returns true or -1 if there was no element for which predicate returned true.

indexOfLast

Cmn

Added in 1.4.0

inline fun indexOfLast(predicate: (element) -> Boolean): Int

Returns the index if the last element in the ObjectList for which predicate returns true or -1 if there was no element for which predicate returned true.

isEmpty

Cmn

Added in 1.4.0

fun isEmpty(): Boolean

Returns true if the ObjectList has no elements in it or false otherwise.

isNotEmpty

Cmn

Added in 1.4.0

fun isNotEmpty(): Boolean

Returns true if there are elements in the ObjectList or false if it is empty.

joinToString

Cmn

fun joinToString(
    separator: CharSequence = ", ",
    prefix: CharSequence = "",
    postfix: CharSequence = "",
    limit: Int = -1,
    truncated: CharSequence = "...",
    transform: ((E) -> CharSequence)? = null
): String

Creates a String from the elements separated by separator and using prefix before and postfix after, if supplied.

When a non-negative value of limit is provided, a maximum of limit items are used to generate the string. If the collection holds more than limit items, the string is terminated with truncated.

transform may be supplied to convert each element to a custom String.

last

Cmn

Added in 1.4.0

fun last(): E

Returns the last element in the ObjectList or throws a NoSuchElementException if it isEmpty.

last

Cmn

Added in 1.4.0

inline fun last(predicate: (element) -> Boolean): E

Returns the last element in the ObjectList for which predicate returns true or throws NoSuchElementException if nothing matches.

See also
`indexOfLast`
`lastOrNull`

lastIndexOf

Cmn

Added in 1.4.0

fun lastIndexOf(element: E): Int

Returns the index of the last element in the ObjectList that is the same as element or -1 if no elements match.

lastOrNull

Cmn

Added in 1.4.0

inline fun lastOrNull(): E?

Returns the last element in the ObjectList or null if it isEmpty.

lastOrNull

Cmn

Added in 1.4.0

inline fun lastOrNull(predicate: (element) -> Boolean): E?

Returns the last element in the ObjectList for which predicate returns true or null if nothing matches.

See also
`indexOfLast`

none

Cmn

Added in 1.4.0

fun none(): Boolean

Returns true if the collection has no elements in it.

reversedAny

Cmn

Added in 1.4.0

inline fun reversedAny(predicate: (element) -> Boolean): Boolean

Returns true if any of the elements give a true return value for predicate while iterating in the reverse order.

toString

Cmn

open fun toString(): String

Returns a String representation of the list, surrounded by "[]" and each element separated by ", ".

Public properties

indices

Cmn

Added in 1.4.0

val indices: IntRange

Returns an IntRange of the valid indices for this ObjectList.

lastIndex

Cmn

Added in 1.4.0

val lastIndex: Int

Returns the last valid index in the ObjectList. This can be -1 when the list is empty.

size

Cmn

Added in 1.4.0

val size: Int

The number of elements in the ObjectList.