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.
|
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 . |
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 . |
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. |
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 . |
Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2024, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
Scripting on this page tracks web page traffic, but does not change the content in any way.