DoubleCollector (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 DoubleCollector<A,R>
```
A Collector specialized to work with primitive double.

Since:

0.3.0

Author:

Tagir Valeev

See Also:

DoubleStreamEx.collect(DoubleCollector)

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,Double>`	`accumulator()` A function that folds a value into a mutable result container.
`default <RR> DoubleCollector<A,RR>`	`andThen(Function<R,RR> finisher)` Adapts this collector to perform an additional finishing transformation.
`static DoubleCollector<?,OptionalDouble>`	`averaging()` Returns a `DoubleCollector` 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 DoubleCollector<?,Long>`	`counting()` Returns a `DoubleCollector` that counts the number of input elements and returns the result as `Long`.
`static DoubleCollector<?,Integer>`	`countingInt()` Returns an `DoubleCollector` that counts the number of input elements and returns the result as `Integer`.
`ObjDoubleConsumer<A>`	`doubleAccumulator()` A function that folds a value into a mutable result container.
`static <K> DoubleCollector<?,Map<K,double[]>>`	`groupingBy(DoubleFunction<? extends K> classifier)` Returns a `DoubleCollector` 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> DoubleCollector<?,Map<K,D>>`	`groupingBy(DoubleFunction<? extends K> classifier, DoubleCollector<A,D> downstream)` Returns a `DoubleCollector` 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>> DoubleCollector<?,M>`	`groupingBy(DoubleFunction<? extends K> classifier, Supplier<M> mapFactory, DoubleCollector<A,D> downstream)` Returns a `DoubleCollector` 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 DoubleCollector<?,String>`	`joining(CharSequence delimiter)` Returns a `DoubleCollector` that converts the input numbers to strings and concatenates them, separated by the specified delimiter, in encounter order.
`static DoubleCollector<?,String>`	`joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix)` Returns a `DoubleCollector` that converts the input numbers to strings and concatenates them, separated by the specified delimiter, with the specified prefix and suffix, in encounter order.
`static <A,R> DoubleCollector<?,R>`	`mapping(DoubleUnaryOperator mapper, DoubleCollector<A,R> downstream)` Adapts a `DoubleCollector` to another one by applying a mapping function to each input element before accumulation.
`static <U,A,R> DoubleCollector<?,R>`	`mappingToObj(DoubleFunction<U> mapper, Collector<U,A,R> downstream)` Adapts a `Collector` accepting elements of type `U` to a `DoubleCollector` by applying a mapping function to each input element before accumulation.
`static DoubleCollector<?,OptionalDouble>`	`max()` Returns a `DoubleCollector` that produces the maximal element, described as an `OptionalDouble`.
`BiConsumer<A,A>`	`merger()` A function that merges the second partial result into the first partial result.
`static DoubleCollector<?,OptionalDouble>`	`min()` Returns a `DoubleCollector` that produces the minimal element, described as an `OptionalDouble`.
`static <A,R> DoubleCollector<?,R>`	`of(Collector<Double,A,R> collector)` Adapts a `Collector` which accepts elements of type `Double` to a `DoubleCollector`.
`static <A,R> DoubleCollector<A,R>`	`of(Supplier<A> supplier, ObjDoubleConsumer<A> doubleAccumulator, BiConsumer<A,A> merger, Function<A,R> finisher)` Returns a new `DoubleCollector` described by the given `supplier`, `accumulator`, `merger`, and `finisher` functions.
`static <R> DoubleCollector<R,R>`	`of(Supplier<R> supplier, ObjDoubleConsumer<R> doubleAccumulator, BiConsumer<R,R> merger)` Returns a new `DoubleCollector` described by the given `supplier`, `accumulator`, and `merger` functions.
`static DoubleCollector<?,Map<Boolean,double[]>>`	`partitioningBy(DoublePredicate predicate)` Returns a `DoubleCollector` which partitions the input elements according to a `DoublePredicate`, and organizes them into a `Map<Boolean, double[]>`.
`static <A,D> DoubleCollector<?,Map<Boolean,D>>`	`partitioningBy(DoublePredicate predicate, DoubleCollector<A,D> downstream)` Returns a `DoubleCollector` which partitions the input numbers according to a `DoublePredicate`, 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 DoubleCollector<?,OptionalDouble>`	`reducing(DoubleBinaryOperator op)` Returns a `DoubleCollector` which performs a reduction of its input numbers under a specified `DoubleBinaryOperator`.
`static DoubleCollector<?,Double>`	`reducing(double identity, DoubleBinaryOperator op)` Returns a `DoubleCollector` which performs a reduction of its input numbers under a specified `IntBinaryOperator` using the provided identity.
`static DoubleCollector<?,DoubleSummaryStatistics>`	`summarizing()` Returns a `DoubleCollector` which returns summary statistics for the input elements.
`static DoubleCollector<?,Double>`	`summing()` Returns a `DoubleCollector` that produces the sum of the input elements.
`static DoubleCollector<?,double[]>`	`toArray()` Returns a `DoubleCollector` that produces the array of the input elements.
`static DoubleCollector<?,boolean[]>`	`toBooleanArray(DoublePredicate predicate)` Returns a `DoubleCollector` which produces a boolean array containing the results of applying the given predicate to the input elements, in encounter order.
`static DoubleCollector<?,float[]>`	`toFloatArray()` Returns a `DoubleCollector` that produces the `float[]` array of the input elements converting them via `(float)` casting.

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

- Method Detail
  - doubleAccumulator
```
ObjDoubleConsumer<A> doubleAccumulator()
```
    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,Double> accumulator()
```
    A function that folds a value into a mutable result container. The default implementation calls doubleAccumulator() on unboxed value.
    
    Returns:
    
    a function which folds a value into a mutable result container
  - andThen
```
default <RR> DoubleCollector<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> DoubleCollector<R,R> of(Supplier<R> supplier,
                                   ObjDoubleConsumer<R> doubleAccumulator,
                                   BiConsumer<R,R> merger)
```
    Returns a new DoubleCollector described by the given supplier, accumulator, and merger functions. The resulting DoubleCollector 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
    
    doubleAccumulator - The doubleAccumulator function for the new collector
    
    merger - The merger function for the new collector
    
    Returns:
    
    the new DoubleCollector
  - of
```
static <A,R> DoubleCollector<?,R> of(Collector<Double,A,R> collector)
```
    Adapts a Collector which accepts elements of type Double to a DoubleCollector.
    
    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 DoubleCollector which behaves in the same way as input collector.
  - of
```
static <A,R> DoubleCollector<A,R> of(Supplier<A> supplier,
                                     ObjDoubleConsumer<A> doubleAccumulator,
                                     BiConsumer<A,A> merger,
                                     Function<A,R> finisher)
```
    Returns a new DoubleCollector 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
    
    doubleAccumulator - The doubleAccumulator function for the new collector
    
    merger - The merger function for the new collector
    
    finisher - The finisher function for the new collector
    
    Returns:
    
    the new DoubleCollector
  - joining
```
static DoubleCollector<?,String> joining(CharSequence delimiter,
                                         CharSequence prefix,
                                         CharSequence suffix)
```
    Returns a DoubleCollector 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 DoubleCollector which concatenates the input numbers, separated by the specified delimiter, in encounter order
  - joining
```
static DoubleCollector<?,String> joining(CharSequence delimiter)
```
    Returns a DoubleCollector 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 DoubleCollector which concatenates the input numbers, separated by the specified delimiter, in encounter order
  - counting
```
static DoubleCollector<?,Long> counting()
```
    Returns a DoubleCollector that counts the number of input elements and returns the result as Long. If no elements are present, the result is 0.
    
    Returns:
    
    a DoubleCollector that counts the input elements
  - countingInt
```
static DoubleCollector<?,Integer> countingInt()
```
    Returns an DoubleCollector that counts the number of input elements and returns the result as Integer. If no elements are present, the result is 0.
    
    Returns:
    
    an DoubleCollector that counts the input elements
  - summing
```
static DoubleCollector<?,Double> summing()
```
    Returns a DoubleCollector that produces the sum of the input elements. If no elements are present, the result is 0.0.
    
    Returns:
    
    a DoubleCollector that produces the sum of the input elements
  - averaging
```
static DoubleCollector<?,OptionalDouble> averaging()
```
    Returns a DoubleCollector that produces the arithmetic mean of the input elements or an empty optional if no elements are collected.
    
    Returns:
    
    a DoubleCollector that produces the arithmetic mean of the input elements
    
    Since:
    
    0.3.7
  - min
```
static DoubleCollector<?,OptionalDouble> min()
```
    Returns a DoubleCollector that produces the minimal element, described as an OptionalDouble. If no elements are present, the result is an empty OptionalDouble.
    
    Returns:
    
    a DoubleCollector that produces the minimal element.
  - max
```
static DoubleCollector<?,OptionalDouble> max()
```
    Returns a DoubleCollector that produces the maximal element, described as an OptionalDouble. If no elements are present, the result is an empty OptionalDouble.
    
    Returns:
    
    a DoubleCollector that produces the maximal element.
  - mapping
```
static <A,R> DoubleCollector<?,R> mapping(DoubleUnaryOperator mapper,
                                          DoubleCollector<A,R> downstream)
```
    Adapts a DoubleCollector 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> DoubleCollector<?,R> mappingToObj(DoubleFunction<U> mapper,
                                                 Collector<U,A,R> downstream)
```
    Adapts a Collector accepting elements of type U to a DoubleCollector 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 DoubleCollector<?,OptionalDouble> reducing(DoubleBinaryOperator op)
```
    Returns a DoubleCollector which performs a reduction of its input numbers under a specified DoubleBinaryOperator. The result is described as an OptionalDouble.
    
    Parameters:
    
    op - a DoubleBinaryOperator used to reduce the input numbers
    
    Returns:
    
    a DoubleCollector which implements the reduction operation.
  - reducing
```
static DoubleCollector<?,Double> reducing(double identity,
                                          DoubleBinaryOperator op)
```
    Returns a DoubleCollector 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 DoubleBinaryOperator used to reduce the input numbers
    
    Returns:
    
    a DoubleCollector which implements the reduction operation
  - summarizing
```
static DoubleCollector<?,DoubleSummaryStatistics> summarizing()
```
    Returns a DoubleCollector which returns summary statistics for the input elements.
    
    Returns:
    
    a DoubleCollector implementing the summary-statistics reduction
  - partitioningBy
```
static DoubleCollector<?,Map<Boolean,double[]>> partitioningBy(DoublePredicate predicate)
```
    Returns a DoubleCollector which partitions the input elements according to a DoublePredicate, and organizes them into a Map<Boolean, double[]>. 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 DoubleCollector implementing the partitioning operation
  - partitioningBy
```
static <A,D> DoubleCollector<?,Map<Boolean,D>> partitioningBy(DoublePredicate predicate,
                                                              DoubleCollector<A,D> downstream)
```
    Returns a DoubleCollector which partitions the input numbers according to a DoublePredicate, 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 DoubleCollector implementing the downstream reduction
    
    Returns:
    
    a DoubleCollector implementing the cascaded partitioning operation
  - groupingBy
```
static <K> DoubleCollector<?,Map<K,double[]>> groupingBy(DoubleFunction<? extends K> classifier)
```
    Returns a DoubleCollector 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, double[]> 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 DoubleCollector implementing the group-by operation
  - groupingBy
```
static <K,D,A> DoubleCollector<?,Map<K,D>> groupingBy(DoubleFunction<? extends K> classifier,
                                                      DoubleCollector<A,D> downstream)
```
    Returns a DoubleCollector 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 DoubleCollector implementing the downstream reduction
    
    Returns:
    
    a DoubleCollector implementing the cascaded group-by operation
  - groupingBy
```
static <K,D,A,M extends Map<K,D>> DoubleCollector<?,M> groupingBy(DoubleFunction<? extends K> classifier,
                                                                  Supplier<M> mapFactory,
                                                                  DoubleCollector<A,D> downstream)
```
    Returns a DoubleCollector 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 DoubleCollector implementing the downstream reduction
    
    mapFactory - a function which, when called, produces a new empty Map of the desired type
    
    Returns:
    
    a DoubleCollector implementing the cascaded group-by operation
  - toArray
```
static DoubleCollector<?,double[]> toArray()
```
    Returns a DoubleCollector that produces the array of the input elements. If no elements are present, the result is an empty array.
    
    Returns:
    
    a DoubleCollector that produces the array of the input elements
  - toFloatArray
```
static DoubleCollector<?,float[]> toFloatArray()
```
    Returns a DoubleCollector that produces the float[] array of the input elements converting them via (float) casting. If no elements are present, the result is an empty array.
    
    Returns:
    
    a DoubleCollector that produces the float[] array of the input elements
  - toBooleanArray
```
static DoubleCollector<?,boolean[]> toBooleanArray(DoublePredicate predicate)
```
    Returns a DoubleCollector 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 DoubleCollector 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 DoubleCollector<A,R>

Nested Class Summary

Nested classes/interfaces inherited from interface Collector

Method Summary

Methods inherited from interface Collector

Method Detail

doubleAccumulator

accumulator

andThen

of

of

of

joining

joining

counting

countingInt

summing

averaging

min

max

mapping

mappingToObj

reducing

reducing

summarizing

partitioningBy

partitioningBy

groupingBy

groupingBy

groupingBy

toArray

toFloatArray

toBooleanArray

merger

combiner