Uses of Class java.util.Optional

Uses of Class
java.util.Optional

Packages that use Optional

Package	Description
java.util	Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array).
java.util.stream	Classes to support functional-style operations on streams of elements, such as map-reduce transformations on collections.

Uses of Optional in java.util

Methods in that return

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 java.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 java.util.stream

Methods in that return

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 java.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`.