LongCollector (StreamEx 0.6.5 API)

Type Parameters:

A - the mutable accumulation type of the reduction operation (often hidden as an implementation detail)

R - the result type of the reduction operation
```
public interface LongCollector<A,R>
```
A Collector specialized to work with primitive long.

Since:

0.3.0

Author:

Tagir Valeev

See Also:

LongStreamEx.collect(LongCollector)

Nested Class Summary
- Nested classes/interfaces inherited from interface Collector
  Collector.Characteristics

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`default BiConsumer<A,Long>`	`accumulator()` A function that folds a value into a mutable result container.
`default <RR> LongCollector<A,RR>`	`andThen(Function<R,RR> finisher)` Adapts this collector to perform an additional finishing transformation.
`static LongCollector<?,OptionalDouble>`	`averaging()` Returns a `LongCollector` that produces the arithmetic mean of the input elements or an empty optional if no elements are collected.
`default BinaryOperator<A>`	`combiner()` A function that accepts two partial results and combines them returning either existing partial result or new one.
`static LongCollector<?,Long>`	`counting()` Returns a `LongCollector` that counts the number of input elements and returns the result as `Long`.
`static LongCollector<?,Integer>`	`countingInt()` Returns an `LongCollector` that counts the number of input elements and returns the result as `Integer`.
`static <K> LongCollector<?,Map<K,long[]>>`	`groupingBy(LongFunction<? extends K> classifier)` Returns a `LongCollector` implementing a "group by" operation on input numbers, grouping them according to a classification function, and returning the results in a `Map`.
`static <K,D,A> LongCollector<?,Map<K,D>>`	`groupingBy(LongFunction<? extends K> classifier, LongCollector<A,D> downstream)` Returns a `LongCollector` implementing a cascaded "group by" operation on input numbers, grouping them according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `IntCollector`.
`static <K,D,A,M extends Map<K,D>> LongCollector<?,M>`	`groupingBy(LongFunction<? extends K> classifier, Supplier<M> mapFactory, LongCollector<A,D> downstream)` Returns a `LongCollector` implementing a cascaded "group by" operation on input numbers, grouping them according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream `IntCollector`.
`static LongCollector<?,String>`	`joining(CharSequence delimiter)` Returns a `LongCollector` that converts the input numbers to strings and concatenates them, separated by the specified delimiter, in encounter order.
`static LongCollector<?,String>`	`joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix)` Returns a `LongCollector` that converts the input numbers to strings and concatenates them, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.
`ObjLongConsumer<A>`	`longAccumulator()` A function that folds a value into a mutable result container.
`static <A,R> LongCollector<?,R>`	`mapping(LongUnaryOperator mapper, LongCollector<A,R> downstream)` Adapts a `LongCollector` to another one by applying a mapping function to each input element before accumulation.
`static <U,A,R> LongCollector<?,R>`	`mappingToObj(LongFunction<U> mapper, Collector<U,A,R> downstream)` Adapts a `Collector` accepting elements of type `U` to a `LongCollector` by applying a mapping function to each input element before accumulation.
`static LongCollector<?,OptionalLong>`	`max()` Returns a `LongCollector` that produces the maximal element, described as an `OptionalLong`.
`BiConsumer<A,A>`	`merger()` A function that merges the second partial result into the first partial result.
`static LongCollector<?,OptionalLong>`	`min()` Returns a `LongCollector` that produces the minimal element, described as an `OptionalLong`.
`static <A,R> LongCollector<?,R>`	`of(Collector<Long,A,R> collector)` Adapts a `Collector` which accepts elements of type `Long` to a `LongCollector`.
`static <A,R> LongCollector<A,R>`	`of(Supplier<A> supplier, ObjLongConsumer<A> longAccumulator, BiConsumer<A,A> merger, Function<A,R> finisher)` Returns a new `LongCollector` described by the given `supplier`, `accumulator`, `merger`, and `finisher` functions.
`static <R> LongCollector<R,R>`	`of(Supplier<R> supplier, ObjLongConsumer<R> longAccumulator, BiConsumer<R,R> merger)` Returns a new `LongCollector` described by the given `supplier`, `accumulator`, and `merger` functions.
`static LongCollector<?,Map<Boolean,long[]>>`	`partitioningBy(LongPredicate predicate)` Returns a `LongCollector` which partitions the input elements according to a `LongPredicate`, and organizes them into a `Map<Boolean, long[]>`.
`static <A,D> LongCollector<?,Map<Boolean,D>>`	`partitioningBy(LongPredicate predicate, LongCollector<A,D> downstream)` Returns a `LongCollector` which partitions the input numbers according to a `LongPredicate`, reduces the values in each partition according to another `IntCollector`, and organizes them into a `Map<Boolean, D>` whose values are the result of the downstream reduction.
`static LongCollector<?,OptionalLong>`	`reducing(LongBinaryOperator op)` Returns a `LongCollector` which performs a reduction of its input numbers under a specified `LongBinaryOperator`.
`static LongCollector<?,Long>`	`reducing(long identity, LongBinaryOperator op)` Returns a `LongCollector` which performs a reduction of its input numbers under a specified `IntBinaryOperator` using the provided identity.
`static LongCollector<?,LongSummaryStatistics>`	`summarizing()` Returns a `LongCollector` which returns summary statistics for the input elements.
`static LongCollector<?,Long>`	`summing()` Returns a `LongCollector` that produces the sum of the input elements.
`static LongCollector<?,long[]>`	`toArray()` Returns a `LongCollector` that produces the array of the input elements.
`static LongCollector<?,boolean[]>`	`toBooleanArray(LongPredicate predicate)` Returns a `LongCollector` which produces a boolean array containing the results of applying the given predicate to the input elements, in encounter order.

Methods inherited from interface Collector
characteristics, finisher, of, of, supplier

- Method Detail
  - longAccumulator
```
ObjLongConsumer<A> longAccumulator()
```
    A function that folds a value into a mutable result container.
    
    Returns:
    
    a function which folds a value into a mutable result container
  - accumulator
```
default BiConsumer<A,Long> accumulator()
```
    A function that folds a value into a mutable result container. The default implementation calls longAccumulator() on unboxed value.
    
    Returns:
    
    a function which folds a value into a mutable result container
  - andThen
```
default <RR> LongCollector<A,RR> andThen(Function<R,RR> finisher)
```
    Adapts this collector to perform an additional finishing transformation.
    
    Type Parameters:
    
    RR - result type of the resulting collector
    
    Parameters:
    
    finisher - a function to be applied to the final result of this collector
    
    Returns:
    
    a collector which performs the action of this collector, followed by an additional finishing step
    
    Since:
    
    0.3.7
  - of
```
static <R> LongCollector<R,R> of(Supplier<R> supplier,
                                 ObjLongConsumer<R> longAccumulator,
                                 BiConsumer<R,R> merger)
```
    Returns a new LongCollector described by the given supplier, accumulator, and merger functions. The resulting LongCollector has the Collector.Characteristics.IDENTITY_FINISH characteristic.
    
    Type Parameters:
    
    R - The type of intermediate accumulation result, and final result, for the new collector
    
    Parameters:
    
    supplier - The supplier function for the new collector
    
    longAccumulator - The longAccumulator function for the new collector
    
    merger - The merger function for the new collector
    
    Returns:
    
    the new LongCollector
  - of
```
static <A,R> LongCollector<?,R> of(Collector<Long,A,R> collector)
```
    Adapts a Collector which accepts elements of type Long to a LongCollector.
    
    Type Parameters:
    
    A - The intermediate accumulation type of the collector
    
    R - The final result type of the collector
    
    Parameters:
    
    collector - a Collector to adapt
    
    Returns:
    
    a LongCollector which behaves in the same way as input collector.
  - of
```
static <A,R> LongCollector<A,R> of(Supplier<A> supplier,
                                   ObjLongConsumer<A> longAccumulator,
                                   BiConsumer<A,A> merger,
                                   Function<A,R> finisher)
```
    Returns a new LongCollector described by the given supplier, accumulator, merger, and finisher functions.
    
    Type Parameters:
    
    A - The intermediate accumulation type of the new collector
    
    R - The final result type of the new collector
    
    Parameters:
    
    supplier - The supplier function for the new collector
    
    longAccumulator - The longAccumulator function for the new collector
    
    merger - The merger function for the new collector
    
    finisher - The finisher function for the new collector
    
    Returns:
    
    the new LongCollector
  - joining
```
static LongCollector<?,String> joining(CharSequence delimiter,
                                       CharSequence prefix,
                                       CharSequence suffix)
```
    Returns a LongCollector that converts the input numbers to strings and concatenates them, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.
    
    Parameters:
    
    delimiter - the delimiter to be used between each element
    
    prefix - the sequence of characters to be used at the beginning of the joined result
    
    suffix - the sequence of characters to be used at the end of the joined result
    
    Returns:
    
    A LongCollector which concatenates the input numbers, separated by the specified delimiter, in encounter order
  - joining
```
static LongCollector<?,String> joining(CharSequence delimiter)
```
    Returns a LongCollector that converts the input numbers to strings and concatenates them, separated by the specified delimiter, in encounter order.
    
    Parameters:
    
    delimiter - the delimiter to be used between each element
    
    Returns:
    
    A LongCollector which concatenates the input numbers, separated by the specified delimiter, in encounter order
  - counting
```
static LongCollector<?,Long> counting()
```
    Returns a LongCollector that counts the number of input elements and returns the result as Long. If no elements are present, the result is 0.
    
    Returns:
    
    a LongCollector that counts the input elements
  - countingInt
```
static LongCollector<?,Integer> countingInt()
```
    Returns an LongCollector that counts the number of input elements and returns the result as Integer. If no elements are present, the result is 0.
    
    Returns:
    
    an LongCollector that counts the input elements
  - summing
```
static LongCollector<?,Long> summing()
```
    Returns a LongCollector that produces the sum of the input elements. If no elements are present, the result is 0.
    
    Returns:
    
    a LongCollector that produces the sum of the input elements
  - averaging
```
static LongCollector<?,OptionalDouble> averaging()
```
    Returns a LongCollector that produces the arithmetic mean of the input elements or an empty optional if no elements are collected.
    Note that unlike LongStream.average(), Collectors.averagingLong(java.util.function.ToLongFunction) and LongSummaryStatistics.getAverage() this collector does not overflow if an intermediate sum exceeds Long.MAX_VALUE.
    
    Returns:
    
    a LongCollector that produces the arithmetic mean of the input elements
    
    Since:
    
    0.3.7
  - min
```
static LongCollector<?,OptionalLong> min()
```
    Returns a LongCollector that produces the minimal element, described as an OptionalLong. If no elements are present, the result is an empty OptionalLong.
    
    Returns:
    
    a LongCollector that produces the minimal element.
  - max
```
static LongCollector<?,OptionalLong> max()
```
    Returns a LongCollector that produces the maximal element, described as an OptionalLong. If no elements are present, the result is an empty OptionalLong.
    
    Returns:
    
    a LongCollector that produces the maximal element.
  - mapping
```
static <A,R> LongCollector<?,R> mapping(LongUnaryOperator mapper,
                                        LongCollector<A,R> downstream)
```
    Adapts a LongCollector to another one by applying a mapping function to each input element before accumulation.
    
    Type Parameters:
    
    A - intermediate accumulation type of the downstream collector
    
    R - result type of collector
    
    Parameters:
    
    mapper - a function to be applied to the input elements
    
    downstream - a collector which will accept mapped values
    
    Returns:
    
    a collector which applies the mapping function to the input elements and provides the mapped results to the downstream collector
  - mappingToObj
```
static <U,A,R> LongCollector<?,R> mappingToObj(LongFunction<U> mapper,
                                               Collector<U,A,R> downstream)
```
    Adapts a Collector accepting elements of type U to a LongCollector by applying a mapping function to each input element before accumulation.
    
    Type Parameters:
    
    U - type of elements accepted by downstream collector
    
    A - intermediate accumulation type of the downstream collector
    
    R - result type of collector
    
    Parameters:
    
    mapper - a function to be applied to the input elements
    
    downstream - a collector which will accept mapped values
    
    Returns:
    
    a collector which applies the mapping function to the input elements and provides the mapped results to the downstream collector
  - reducing
```
static LongCollector<?,OptionalLong> reducing(LongBinaryOperator op)
```
    Returns a LongCollector which performs a reduction of its input numbers under a specified LongBinaryOperator. The result is described as an OptionalLong.
    
    Parameters:
    
    op - a LongBinaryOperator used to reduce the input numbers
    
    Returns:
    
    a LongCollector which implements the reduction operation.
  - reducing
```
static LongCollector<?,Long> reducing(long identity,
                                      LongBinaryOperator op)
```
    Returns a LongCollector which performs a reduction of its input numbers under a specified IntBinaryOperator using the provided identity.
    
    Parameters:
    
    identity - the identity value for the reduction (also, the value that is returned when there are no input elements)
    
    op - a LongBinaryOperator used to reduce the input numbers
    
    Returns:
    
    a LongCollector which implements the reduction operation
  - summarizing
```
static LongCollector<?,LongSummaryStatistics> summarizing()
```
    Returns a LongCollector which returns summary statistics for the input elements.
    
    Returns:
    
    a LongCollector implementing the summary-statistics reduction
  - partitioningBy
```
static LongCollector<?,Map<Boolean,long[]>> partitioningBy(LongPredicate predicate)
```
    Returns a LongCollector which partitions the input elements according to a LongPredicate, and organizes them into a Map<Boolean, long[]>. There are no guarantees on the type, mutability, serializability, or thread-safety of the Map returned.
    
    Parameters:
    
    predicate - a predicate used for classifying input elements
    
    Returns:
    
    a LongCollector implementing the partitioning operation
  - partitioningBy
```
static <A,D> LongCollector<?,Map<Boolean,D>> partitioningBy(LongPredicate predicate,
                                                            LongCollector<A,D> downstream)
```
    Returns a LongCollector which partitions the input numbers according to a LongPredicate, reduces the values in each partition according to another IntCollector, and organizes them into a Map<Boolean, D> whose values are the result of the downstream reduction.
    There are no guarantees on the type, mutability, serializability, or thread-safety of the Map returned.
    
    Type Parameters:
    
    A - the intermediate accumulation type of the downstream collector
    
    D - the result type of the downstream reduction
    
    Parameters:
    
    predicate - a predicate used for classifying input elements
    
    downstream - a LongCollector implementing the downstream reduction
    
    Returns:
    
    a LongCollector implementing the cascaded partitioning operation
  - groupingBy
```
static <K> LongCollector<?,Map<K,long[]>> groupingBy(LongFunction<? extends K> classifier)
```
    Returns a LongCollector implementing a "group by" operation on input numbers, grouping them according to a classification function, and returning the results in a Map.
    The classification function maps elements to some key type K. The collector produces a Map<K, long[]> whose keys are the values resulting from applying the classification function to the input numbers, and whose corresponding values are arrays containing the input numbers which map to the associated key under the classification function.
    There are no guarantees on the type, mutability, serializability, or thread-safety of the Map objects returned.
    
    Type Parameters:
    
    K - the type of the keys
    
    Parameters:
    
    classifier - the classifier function mapping input elements to keys
    
    Returns:
    
    a LongCollector implementing the group-by operation
  - groupingBy
```
static <K,D,A> LongCollector<?,Map<K,D>> groupingBy(LongFunction<? extends K> classifier,
                                                    LongCollector<A,D> downstream)
```
    Returns a LongCollector implementing a cascaded "group by" operation on input numbers, grouping them according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream IntCollector.
    The classification function maps elements to some key type K. The downstream collector produces a result of type D. The resulting collector produces a Map<K, D>.
    There are no guarantees on the type, mutability, serializability, or thread-safety of the Map returned.
    
    Type Parameters:
    
    K - the type of the keys
    
    A - the intermediate accumulation type of the downstream collector
    
    D - the result type of the downstream reduction
    
    Parameters:
    
    classifier - a classifier function mapping input elements to keys
    
    downstream - a LongCollector implementing the downstream reduction
    
    Returns:
    
    a LongCollector implementing the cascaded group-by operation
  - groupingBy
```
static <K,D,A,M extends Map<K,D>> LongCollector<?,M> groupingBy(LongFunction<? extends K> classifier,
                                                                Supplier<M> mapFactory,
                                                                LongCollector<A,D> downstream)
```
    Returns a LongCollector implementing a cascaded "group by" operation on input numbers, grouping them according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream IntCollector. The Map produced by the Collector is created with the supplied factory function.
    The classification function maps elements to some key type K. The downstream collector produces a result of type D. The resulting collector produces a Map<K, D>.
    
    Type Parameters:
    
    K - the type of the keys
    
    A - the intermediate accumulation type of the downstream collector
    
    D - the result type of the downstream reduction
    
    M - the type of the resulting Map
    
    Parameters:
    
    classifier - a classifier function mapping input elements to keys
    
    downstream - a LongCollector implementing the downstream reduction
    
    mapFactory - a function which, when called, produces a new empty Map of the desired type
    
    Returns:
    
    a LongCollector implementing the cascaded group-by operation
  - toArray
```
static LongCollector<?,long[]> toArray()
```
    Returns a LongCollector that produces the array of the input elements. If no elements are present, the result is an empty array.
    
    Returns:
    
    a LongCollector that produces the array of the input elements
  - toBooleanArray
```
static LongCollector<?,boolean[]> toBooleanArray(LongPredicate predicate)
```
    Returns a LongCollector which produces a boolean array containing the results of applying the given predicate to the input elements, in encounter order.
    
    Parameters:
    
    predicate - a non-interfering, stateless predicate to apply to each input element. The result values of this predicate are collected to the resulting boolean array.
    
    Returns:
    
    a LongCollector which collects the results of the predicate function to the boolean array, in encounter order.
    
    Since:
    
    0.3.8
  - merger
```
BiConsumer<A,A> merger()
```
    A function that merges the second partial result into the first partial result.
    
    Returns:
    
    a function that merges the second partial result into the first partial result.
  - combiner
```
default BinaryOperator<A> combiner()
```
    A function that accepts two partial results and combines them returning either existing partial result or new one. The default implementation calls the merger() and returns the first partial result.
    
    Specified by:
    
    combiner in interface Collector<T,A,R>
    
    Returns:
    
    a function which combines two partial results into a combined result

Interface LongCollector<A,R>

Nested Class Summary

Nested classes/interfaces inherited from interface Collector

Method Summary

Methods inherited from interface Collector

Method Detail

longAccumulator

accumulator

andThen

of

of

of

joining

joining

counting

countingInt

summing

averaging

min

max

mapping

mappingToObj

reducing

reducing

summarizing

partitioningBy

partitioningBy

groupingBy

groupingBy

groupingBy

toArray

toBooleanArray

merger

combiner