Uses of Class
java8.util.Optional

Packages that use Optional

Package	Description
java8.util	Provides some of the new java.util classes and implementations of static and default interface methods added in Java 8.
java8.util.stream	Classes to support functional-style operations on streams of elements, such as map-reduce transformations on collections.

Uses of Optional in java8.util

Methods in java8.util that return Optional

Modifier and Type	Method and Description
static <T> Optional<T>	Optional.empty() Returns an empty Optional instance.
Optional<T>	Optional.filter(Predicate<? super T> predicate) If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.
<U> Optional<U>	Optional.flatMap(Function<? super T,Optional<U>> mapper) If a value is present, apply the provided Optional-bearing mapping function to it, return that result, otherwise return an empty Optional.
<U> Optional<U>	Optional.map(Function<? super T,? extends U> mapper) If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result.
static <T> Optional<T>	Optional.of(T value) Returns an Optional with the specified present non-null value.
static <T> Optional<T>	Optional.ofNullable(T value) Returns an Optional describing the specified value, if non-null, otherwise returns an empty Optional.

Method parameters in java8.util with type arguments of type Optional

Modifier and Type	Method and Description
<U> Optional<U>	Optional.flatMap(Function<? super T,Optional<U>> mapper) If a value is present, apply the provided Optional-bearing mapping function to it, return that result, otherwise return an empty Optional.

Uses of Optional in java8.util.stream

Methods in java8.util.stream that return Optional

Modifier and Type	Method and Description
Optional<T>	Stream.findAny() Returns an Optional describing some element of the stream, or an empty Optional if the stream is empty.
Optional<T>	Stream.findFirst() Returns an Optional describing the first element of this stream, or an empty Optional if the stream is empty.
Optional<T>	Stream.max(Comparator<? super T> comparator) Returns the maximum element of this stream according to the provided Comparator.
Optional<T>	Stream.min(Comparator<? super T> comparator) Returns the minimum element of this stream according to the provided Comparator.
Optional<T>	Stream.reduce(BinaryOperator<T> accumulator) Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an Optional describing the reduced value, if any.

Methods in java8.util.stream that return types with arguments of type Optional

Modifier and Type	Method and Description
static <T> Collector<T,?,Optional<T>>	Collectors.maxBy(Comparator<? super T> comparator) Returns a Collector that produces the maximal element according to a given Comparator, described as an Optional<T>.
static <T> Collector<T,?,Optional<T>>	Collectors.minBy(Comparator<? super T> comparator) Returns a Collector that produces the minimal element according to a given Comparator, described as an Optional<T>.
static <T> Collector<T,?,Optional<T>>	Collectors.reducing(BinaryOperator<T> op) Returns a Collector which performs a reduction of its input elements under a specified BinaryOperator.