core/org.gnit.lucenekmp.jdkport/Optional

Optional

A container object which may or may not contain a non-null value. If a value is present, isPresent() returns true. If no value is present, the object is considered empty and isPresent() returns false.

Additional methods that depend on the presence or absence of a contained value are provided, such as .orElse (returns a default value if no value is present) and .ifPresent (performs an action if a value is present).

This is a {@docRoot}/java.base/java/lang/doc-files/ValueBased.html class; programmers should treat instances that are .equals as interchangeable and should not use instances for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail.

Since

1.8

Parameters

the type of value

Types

Companion

object Companion

Properties

isEmpty

val isEmpty: Boolean

isPresent

val isPresent: Boolean

Functions

equals

open operator override fun equals(obj: Any?): Boolean

Indicates whether some other object is "equal to" this Optional. The other object is considered equal if:

filter

fun filter(predicate: (T?) -> Boolean): Optional<T?>

If a value is present, and the value matches the given predicate, returns an Optional describing the value, otherwise returns an empty Optional.

flatMap

fun <U> flatMap(mapper: (T?) -> Optional<U?>?): Optional<U?>

If a value is present, returns the result of applying the given Optional-bearing mapping function to the value, otherwise returns an empty Optional.

get

fun get(): T

If a value is present, returns the value, otherwise throws NoSuchElementException.

hashCode

open override fun hashCode(): Int

Returns the hash code of the value, if present, otherwise 0 (zero) if no value is present.

ifPresent

fun ifPresent(action: (T) -> Unit)

If a value is present, performs the given action with the value, otherwise does nothing.

ifPresentOrElse

fun ifPresentOrElse(action: (T) -> Unit, emptyAction: () -> Unit)

If a value is present, performs the given action with the value, otherwise performs the given empty-based action.

map

fun <U> map(mapper: (T?) -> U?): Optional<U?>

If a value is present, returns an Optional describing (as if by ofNullable) the result of applying the given mapping function to the value, otherwise returns an empty Optional.

fun or(supplier: () -> Optional<T?>): Optional<T?>

If a value is present, returns an Optional describing the value, otherwise returns an Optional produced by the supplying function.

orElse

fun orElse(other: T?): T?

If a value is present, returns the value, otherwise returns other.

orElseGet

fun orElseGet(supplier: () -> T?): T?

If a value is present, returns the value, otherwise returns the result produced by the supplying function.

orElseThrow

fun orElseThrow(): T

If a value is present, returns the value, otherwise throws NoSuchElementException.

fun <X : Throwable> orElseThrow(exceptionSupplier: () -> X): T

If a value is present, returns the value, otherwise throws an exception produced by the exception supplying function.

stream

fun stream(): Sequence<T?>

If a value is present, returns a sequential Sequence containing only that value, otherwise returns an empty Sequence.

toString

open override fun toString(): String

Returns a non-empty string representation of this Optional suitable for debugging. The exact presentation format is unspecified and may vary between implementations and versions.