Uses of Class
java.util.Optional
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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. -
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Uses of Optional in java.util
Methods in java.util that return Optional Modifier and Type Method and Description static <T> Optional<T>Optional. empty()Returns an emptyOptionalinstance.Optional<T>Optional. filter(Predicate<? super T> predicate)If a value is present, and the value matches the given predicate, return anOptionaldescribing the value, otherwise return an emptyOptional.<U> Optional<U>Optional. flatMap(Function<? super T,Optional<U>> mapper)If a value is present, apply the providedOptional-bearing mapping function to it, return that result, otherwise return an emptyOptional.<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 anOptionaldescribing the result.static <T> Optional<T>Optional. of(T value)Returns anOptionalwith the specified present non-null value.static <T> Optional<T>Optional. ofNullable(T value)Returns anOptionaldescribing the specified value, if non-null, otherwise returns an emptyOptional.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 providedOptional-bearing mapping function to it, return that result, otherwise return an emptyOptional. -
Uses of Optional in java.util.stream
Methods in java.util.stream that return Optional Modifier and Type Method and Description Optional<T>Stream. findAny()Returns anOptionaldescribing some element of the stream, or an emptyOptionalif the stream is empty.Optional<T>Stream. findFirst()Returns anOptionaldescribing the first element of this stream, or an emptyOptionalif the stream is empty.Optional<T>Stream. max(Comparator<? super T> comparator)Returns the maximum element of this stream according to the providedComparator.Optional<T>Stream. min(Comparator<? super T> comparator)Returns the minimum element of this stream according to the providedComparator.Optional<T>Stream. reduce(BinaryOperator<T> accumulator)Performs a reduction on the elements of this stream, using an associative accumulation function, and returns anOptionaldescribing 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 aCollectorthat produces the maximal element according to a givenComparator, described as anOptional<T>.static <T> Collector<T,?,Optional<T>>Collectors. minBy(Comparator<? super T> comparator)Returns aCollectorthat produces the minimal element according to a givenComparator, described as anOptional<T>.static <T> Collector<T,?,Optional<T>>Collectors. reducing(BinaryOperator<T> op)Returns aCollectorwhich performs a reduction of its input elements under a specifiedBinaryOperator.
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