Uses of Interface java.util.stream.Collector (Java SE 14 & JDK 14)

Packages that use Collector
Package	Description
java.util.stream	Classes to support functional-style operations on streams of elements, such as map-reduce transformations on collections.

Uses of Collector in java.util.stream

Methods in java.util.stream that return Collector
Modifier and Type	Method	Description
`static <T> Collector<T,?,Double>`	Collectors.`averagingDouble(ToDoubleFunction<? super T> mapper)`	Returns a `Collector` that produces the arithmetic mean of a double-valued function applied to the input elements.
`static <T> Collector<T,?,Double>`	Collectors.`averagingInt(ToIntFunction<? super T> mapper)`	Returns a `Collector` that produces the arithmetic mean of an integer-valued function applied to the input elements.
`static <T> Collector<T,?,Double>`	Collectors.`averagingLong(ToLongFunction<? super T> mapper)`	Returns a `Collector` that produces the arithmetic mean of a long-valued function applied to the input elements.
`static <T, A, R, RR> Collector<T,A,RR>`	Collectors.`collectingAndThen(Collector<T,A,R> downstream, Function<R,RR> finisher)`	Adapts a `Collector` to perform an additional finishing transformation.
`static <T> Collector<T,?,Long>`	Collectors.`counting()`	Returns a `Collector` accepting elements of type `T` that counts the number of input elements.
`static <T, A, R> Collector<T,?,R>`	Collectors.`filtering(Predicate<? super T> predicate, Collector<? super T,A,R> downstream)`	Adapts a `Collector` to one accepting elements of the same type `T` by applying the predicate to each input element and only accumulating if the predicate returns `true`.
`static <T, U, A, R> Collector<T,?,R>`	Collectors.`flatMapping(Function<? super T,? extends Stream<? extends U>> mapper, Collector<? super U,A,R> downstream)`	Adapts a `Collector` accepting elements of type `U` to one accepting elements of type `T` by applying a flat mapping function to each input element before accumulation.
`static <T, K> Collector<T,?,Map<K,List<T>>>`	Collectors.`groupingBy(Function<? super T,? extends K> classifier)`	Returns a `Collector` implementing a "group by" operation on input elements of type `T`, grouping elements according to a classification function, and returning the results in a `Map`.
`static <T, K, D, A, M extends Map<K, D>> Collector<T,?,M>`	Collectors.`groupingBy(Function<? super T,? extends K> classifier, Supplier<M> mapFactory, Collector<? super T,A,D> downstream)`	Returns a `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static <T, K, A, D> Collector<T,?,Map<K,D>>`	Collectors.`groupingBy(Function<? super T,? extends K> classifier, Collector<? super T,A,D> downstream)`	Returns a `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static <T, K> Collector<T,?,ConcurrentMap<K,List<T>>>`	Collectors.`groupingByConcurrent(Function<? super T,? extends K> classifier)`	Returns a concurrent `Collector` implementing a "group by" operation on input elements of type `T`, grouping elements according to a classification function.
`static <T, K, A, D, M extends ConcurrentMap<K, D>> Collector<T,?,M>`	Collectors.`groupingByConcurrent(Function<? super T,? extends K> classifier, Supplier<M> mapFactory, Collector<? super T,A,D> downstream)`	Returns a concurrent `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static <T, K, A, D> Collector<T,?,ConcurrentMap<K,D>>`	Collectors.`groupingByConcurrent(Function<? super T,? extends K> classifier, Collector<? super T,A,D> downstream)`	Returns a concurrent `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static Collector<CharSequence,?,String>`	Collectors.`joining()`	Returns a `Collector` that concatenates the input elements into a `String`, in encounter order.
`static Collector<CharSequence,?,String>`	Collectors.`joining(CharSequence delimiter)`	Returns a `Collector` that concatenates the input elements, separated by the specified delimiter, in encounter order.
`static Collector<CharSequence,?,String>`	Collectors.`joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix)`	Returns a `Collector` that concatenates the input elements, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.
`static <T, U, A, R> Collector<T,?,R>`	Collectors.`mapping(Function<? super T,? extends U> mapper, Collector<? super U,A,R> downstream)`	Adapts a `Collector` accepting elements of type `U` to one accepting elements of type `T` by applying a mapping function to each input element before accumulation.
`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, A, R> Collector<T,A,R>`	Collector.`of(Supplier<A> supplier, BiConsumer<A,T> accumulator, BinaryOperator<A> combiner, Function<A,R> finisher, Collector.Characteristics... characteristics)`	Returns a new `Collector` described by the given `supplier`, `accumulator`, `combiner`, and `finisher` functions.
`static <T, R> Collector<T,R,R>`	Collector.`of(Supplier<R> supplier, BiConsumer<R,T> accumulator, BinaryOperator<R> combiner, Collector.Characteristics... characteristics)`	Returns a new `Collector` described by the given `supplier`, `accumulator`, and `combiner` functions.
`static <T> Collector<T,?,Map<Boolean,List<T>>>`	Collectors.`partitioningBy(Predicate<? super T> predicate)`	Returns a `Collector` which partitions the input elements according to a `Predicate`, and organizes them into a `Map<Boolean, List<T>>`.
`static <T, D, A> Collector<T,?,Map<Boolean,D>>`	Collectors.`partitioningBy(Predicate<? super T> predicate, Collector<? super T,A,D> downstream)`	Returns a `Collector` which partitions the input elements according to a `Predicate`, reduces the values in each partition according to another `Collector`, and organizes them into a `Map<Boolean, D>` whose values are the result of the downstream reduction.
`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`.
`static <T> Collector<T,?,T>`	Collectors.`reducing(T identity, BinaryOperator<T> op)`	Returns a `Collector` which performs a reduction of its input elements under a specified `BinaryOperator` using the provided identity.
`static <T, U> Collector<T,?,U>`	Collectors.`reducing(U identity, Function<? super T,? extends U> mapper, BinaryOperator<U> op)`	Returns a `Collector` which performs a reduction of its input elements under a specified mapping function and `BinaryOperator`.
`static <T> Collector<T,?,DoubleSummaryStatistics>`	Collectors.`summarizingDouble(ToDoubleFunction<? super T> mapper)`	Returns a `Collector` which applies an `double`-producing mapping function to each input element, and returns summary statistics for the resulting values.
`static <T> Collector<T,?,IntSummaryStatistics>`	Collectors.`summarizingInt(ToIntFunction<? super T> mapper)`	Returns a `Collector` which applies an `int`-producing mapping function to each input element, and returns summary statistics for the resulting values.
`static <T> Collector<T,?,LongSummaryStatistics>`	Collectors.`summarizingLong(ToLongFunction<? super T> mapper)`	Returns a `Collector` which applies an `long`-producing mapping function to each input element, and returns summary statistics for the resulting values.
`static <T> Collector<T,?,Double>`	Collectors.`summingDouble(ToDoubleFunction<? super T> mapper)`	Returns a `Collector` that produces the sum of a double-valued function applied to the input elements.
`static <T> Collector<T,?,Integer>`	Collectors.`summingInt(ToIntFunction<? super T> mapper)`	Returns a `Collector` that produces the sum of a integer-valued function applied to the input elements.
`static <T> Collector<T,?,Long>`	Collectors.`summingLong(ToLongFunction<? super T> mapper)`	Returns a `Collector` that produces the sum of a long-valued function applied to the input elements.
`static <T, R1, R2, R> Collector<T,?,R>`	Collectors.`teeing(Collector<? super T,?,R1> downstream1, Collector<? super T,?,R2> downstream2, BiFunction<? super R1,? super R2,R> merger)`	Returns a `Collector` that is a composite of two downstream collectors.
`static <T, C extends Collection<T>> Collector<T,?,C>`	Collectors.`toCollection(Supplier<C> collectionFactory)`	Returns a `Collector` that accumulates the input elements into a new `Collection`, in encounter order.
`static <T, K, U> Collector<T,?,ConcurrentMap<K,U>>`	Collectors.`toConcurrentMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper)`	Returns a concurrent `Collector` that accumulates elements into a `ConcurrentMap` whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T, K, U> Collector<T,?,ConcurrentMap<K,U>>`	Collectors.`toConcurrentMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, BinaryOperator<U> mergeFunction)`	Returns a concurrent `Collector` that accumulates elements into a `ConcurrentMap` whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T, K, U, M extends ConcurrentMap<K, U>> Collector<T,?,M>`	Collectors.`toConcurrentMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, BinaryOperator<U> mergeFunction, Supplier<M> mapFactory)`	Returns a concurrent `Collector` that accumulates elements into a `ConcurrentMap` whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T> Collector<T,?,List<T>>`	Collectors.`toList()`	Returns a `Collector` that accumulates the input elements into a new `List`.
`static <T, K, U> Collector<T,?,Map<K,U>>`	Collectors.`toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper)`	Returns a `Collector` that accumulates elements into a `Map` whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T, K, U> Collector<T,?,Map<K,U>>`	Collectors.`toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, BinaryOperator<U> mergeFunction)`	Returns a `Collector` that accumulates elements into a `Map` whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T, K, U, M extends Map<K, U>> Collector<T,?,M>`	Collectors.`toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, BinaryOperator<U> mergeFunction, Supplier<M> mapFactory)`	Returns a `Collector` that accumulates elements into a `Map` whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T> Collector<T,?,Set<T>>`	Collectors.`toSet()`	Returns a `Collector` that accumulates the input elements into a new `Set`.
`static <T> Collector<T,?,List<T>>`	Collectors.`toUnmodifiableList()`	Returns a `Collector` that accumulates the input elements into an unmodifiable List in encounter order.
`static <T, K, U> Collector<T,?,Map<K,U>>`	Collectors.`toUnmodifiableMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper)`	Returns a `Collector` that accumulates the input elements into an unmodifiable Map, whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T, K, U> Collector<T,?,Map<K,U>>`	Collectors.`toUnmodifiableMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, BinaryOperator<U> mergeFunction)`	Returns a `Collector` that accumulates the input elements into an unmodifiable Map, whose keys and values are the result of applying the provided mapping functions to the input elements.
`static <T> Collector<T,?,Set<T>>`	Collectors.`toUnmodifiableSet()`	Returns a `Collector` that accumulates the input elements into an unmodifiable Set.

Methods in java.util.stream with parameters of type Collector
Modifier and Type	Method	Description
`<R, A> R`	Stream.`collect(Collector<? super T,A,R> collector)`	Performs a mutable reduction operation on the elements of this stream using a `Collector`.
`static <T, A, R, RR> Collector<T,A,RR>`	Collectors.`collectingAndThen(Collector<T,A,R> downstream, Function<R,RR> finisher)`	Adapts a `Collector` to perform an additional finishing transformation.
`static <T, A, R> Collector<T,?,R>`	Collectors.`filtering(Predicate<? super T> predicate, Collector<? super T,A,R> downstream)`	Adapts a `Collector` to one accepting elements of the same type `T` by applying the predicate to each input element and only accumulating if the predicate returns `true`.
`static <T, U, A, R> Collector<T,?,R>`	Collectors.`flatMapping(Function<? super T,? extends Stream<? extends U>> mapper, Collector<? super U,A,R> downstream)`	Adapts a `Collector` accepting elements of type `U` to one accepting elements of type `T` by applying a flat mapping function to each input element before accumulation.
`static <T, K, D, A, M extends Map<K, D>> Collector<T,?,M>`	Collectors.`groupingBy(Function<? super T,? extends K> classifier, Supplier<M> mapFactory, Collector<? super T,A,D> downstream)`	Returns a `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static <T, K, A, D> Collector<T,?,Map<K,D>>`	Collectors.`groupingBy(Function<? super T,? extends K> classifier, Collector<? super T,A,D> downstream)`	Returns a `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static <T, K, A, D, M extends ConcurrentMap<K, D>> Collector<T,?,M>`	Collectors.`groupingByConcurrent(Function<? super T,? extends K> classifier, Supplier<M> mapFactory, Collector<? super T,A,D> downstream)`	Returns a concurrent `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static <T, K, A, D> Collector<T,?,ConcurrentMap<K,D>>`	Collectors.`groupingByConcurrent(Function<? super T,? extends K> classifier, Collector<? super T,A,D> downstream)`	Returns a concurrent `Collector` implementing a cascaded "group by" operation on input elements of type `T`, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `Collector`.
`static <T, U, A, R> Collector<T,?,R>`	Collectors.`mapping(Function<? super T,? extends U> mapper, Collector<? super U,A,R> downstream)`	Adapts a `Collector` accepting elements of type `U` to one accepting elements of type `T` by applying a mapping function to each input element before accumulation.
`static <T, D, A> Collector<T,?,Map<Boolean,D>>`	Collectors.`partitioningBy(Predicate<? super T> predicate, Collector<? super T,A,D> downstream)`	Returns a `Collector` which partitions the input elements according to a `Predicate`, reduces the values in each partition according to another `Collector`, and organizes them into a `Map<Boolean, D>` whose values are the result of the downstream reduction.
`static <T, R1, R2, R> Collector<T,?,R>`	Collectors.`teeing(Collector<? super T,?,R1> downstream1, Collector<? super T,?,R2> downstream2, BiFunction<? super R1,? super R2,R> merger)`	Returns a `Collector` that is a composite of two downstream collectors.

Uses of Interfacejava.util.stream.Collector

Uses of Collector in java.util.stream

Uses of Interface
java.util.stream.Collector