/*
* Copyright 2015, 2016 Tagir Valeev
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package one.util.streamex;
import java.util.BitSet;
import java.util.HashMap;
import java.util.IntSummaryStatistics;
import java.util.Map;
import java.util.Objects;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.function.BiConsumer;
import java.util.function.Function;
import java.util.function.IntBinaryOperator;
import java.util.function.IntFunction;
import java.util.function.IntPredicate;
import java.util.function.IntUnaryOperator;
import java.util.function.ObjIntConsumer;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import static one.util.streamex.StreamExInternals.*;
/**
* A {@link Collector} specialized to work with primitive {@code int}.
*
* @author Tagir Valeev
*
* @param <A> the mutable accumulation type of the reduction operation (often
* hidden as an implementation detail)
* @param <R> the result type of the reduction operation
* @see IntStreamEx#collect(IntCollector)
* @since 0.3.0
*/
public interface IntCollector<A, R> extends MergingCollector<Integer, A, R> {
/**
* A function that folds a value into a mutable result container.
*
* @return a function which folds a value into a mutable result container
*/
ObjIntConsumer<A> intAccumulator();
/**
* A function that folds a value into a mutable result container.
*
* The default implementation calls {@link #intAccumulator()} on unboxed
* value.
*
* @return a function which folds a value into a mutable result container
*/
@Override
default BiConsumer<A, Integer> accumulator() {
return intAccumulator()::accept;
}
/**
* Adapts this collector to perform an additional finishing transformation.
*
* @param <RR> result type of the resulting collector
* @param finisher a function to be applied to the final result of this
* collector
* @return a collector which performs the action of this collector, followed
* by an additional finishing step
* @since 0.3.7
*/
default <RR> IntCollector<A, RR> andThen(Function<R, RR> finisher) {
return of(supplier(), intAccumulator(), merger(), finisher().andThen(finisher));
}
/**
* Returns a new {@code IntCollector} described by the given
* {@code supplier}, {@code accumulator}, and {@code merger} functions. The
* resulting {@code IntCollector} has the
* {@code Collector.Characteristics.IDENTITY_FINISH} characteristic.
*
* @param supplier The supplier function for the new collector
* @param intAccumulator The intAccumulator function for the new collector
* @param merger The merger function for the new collector
* @param <R> The type of intermediate accumulation result, and final
* result, for the new collector
* @return the new {@code IntCollector}
*/
static <R> IntCollector<R, R> of(Supplier<R> supplier, ObjIntConsumer<R> intAccumulator, BiConsumer<R, R> merger) {
return new IntCollectorImpl<>(supplier, intAccumulator, merger, Function.identity(), ID_CHARACTERISTICS);
}
/**
* Adapts a {@code Collector} which accepts elements of type {@code Integer}
* to an {@code IntCollector}.
*
* @param <A> The intermediate accumulation type of the collector
* @param <R> The final result type of the collector
* @param collector a {@code Collector} to adapt
* @return an {@code IntCollector} which behaves in the same way as input
* collector.
*/
static <A, R> IntCollector<?, R> of(Collector<Integer, A, R> collector) {
if (collector instanceof IntCollector) {
return (IntCollector<A, R>) collector;
}
return mappingToObj(Integer::valueOf, collector);
}
/**
* Returns a new {@code IntCollector} described by the given
* {@code supplier}, {@code accumulator}, {@code merger}, and
* {@code finisher} functions.
*
* @param supplier The supplier function for the new collector
* @param intAccumulator The intAccumulator function for the new collector
* @param merger The merger function for the new collector
* @param finisher The finisher function for the new collector
* @param <A> The intermediate accumulation type of the new collector
* @param <R> The final result type of the new collector
* @return the new {@code IntCollector}
*/
static <A, R> IntCollector<A, R> of(Supplier<A> supplier, ObjIntConsumer<A> intAccumulator,
BiConsumer<A, A> merger, Function<A, R> finisher) {
return new IntCollectorImpl<>(supplier, intAccumulator, merger, finisher, NO_CHARACTERISTICS);
}
/**
* Returns an {@code IntCollector} that converts the input numbers to
* strings and concatenates them, separated by the specified delimiter, with
* the specified prefix and suffix, in encounter order.
*
* @param delimiter the delimiter to be used between each element
* @param prefix the sequence of characters to be used at the beginning of
* the joined result
* @param suffix the sequence of characters to be used at the end of the
* joined result
* @return An {@code IntCollector} which concatenates the input numbers,
* separated by the specified delimiter, in encounter order
*/
static IntCollector<?, String> joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix) {
return PartialCollector.joining(delimiter, prefix, suffix, true).asInt(
StreamExInternals.joinAccumulatorInt(delimiter));
}
/**
* Returns an {@code IntCollector} that converts the input numbers to
* strings and concatenates them, separated by the specified delimiter, in
* encounter order.
*
* @param delimiter the delimiter to be used between each element
* @return An {@code IntCollector} which concatenates the input numbers,
* separated by the specified delimiter, in encounter order
*/
static IntCollector<?, String> joining(CharSequence delimiter) {
return PartialCollector.joining(delimiter, null, null, false).asInt(
StreamExInternals.joinAccumulatorInt(delimiter));
}
/**
* Returns an {@code IntCollector} that counts the number of input elements
* and returns the result as {@code Long}. If no elements are present, the
* result is 0.
*
* @return an {@code IntCollector} that counts the input elements
*/
static IntCollector<?, Long> counting() {
return PartialCollector.longSum().asInt((box, i) -> box[0]++);
}
/**
* Returns an {@code IntCollector} that counts the number of input elements
* and returns the result as {@code Integer}. If no elements are present,
* the result is 0.
*
* @return an {@code IntCollector} that counts the input elements
*/
static IntCollector<?, Integer> countingInt() {
return PartialCollector.intSum().asInt((box, i) -> box[0]++);
}
/**
* Returns an {@code IntCollector} that produces the sum of the input
* elements. If no elements are present, the result is 0.
*
* @return an {@code IntCollector} that produces the sum of the input
* elements
*/
static IntCollector<?, Integer> summing() {
return PartialCollector.intSum().asInt((box, i) -> box[0] += i);
}
/**
* Returns an {@code IntCollector} that produces the arithmetic mean of the
* input elements or an empty optional if no elements are collected.
*
* <p>
* Note that unlike {@link IntStream#average()},
* {@link Collectors#averagingInt(java.util.function.ToIntFunction)} and
* {@link IntSummaryStatistics#getAverage()} this collector does not
* overflow if an intermediate sum exceeds {@code Long.MAX_VALUE}.
*
* @return an {@code IntCollector} that produces the arithmetic mean of the
* input elements
* @since 0.3.7
*/
static IntCollector<?, OptionalDouble> averaging() {
return of(AverageLong::new, AverageLong::accept, AverageLong::combine, AverageLong::result);
}
/**
* Returns an {@code IntCollector} that produces the minimal element,
* described as an {@link OptionalInt}. If no elements are present, the
* result is an empty {@code OptionalInt}.
*
* @return an {@code IntCollector} that produces the minimal element.
*/
static IntCollector<?, OptionalInt> min() {
return reducing(Integer::min);
}
/**
* Returns an {@code IntCollector} that produces the maximal element,
* described as an {@link OptionalInt}. If no elements are present, the
* result is an empty {@code OptionalInt}.
*
* @return an {@code IntCollector} that produces the maximal element.
*/
static IntCollector<?, OptionalInt> max() {
return reducing(Integer::max);
}
/**
* Adapts an {@code IntCollector} to another one by applying a mapping
* function to each input element before accumulation.
*
* @param <A> intermediate accumulation type of the downstream collector
* @param <R> result type of collector
* @param mapper a function to be applied to the input elements
* @param downstream a collector which will accept mapped values
* @return a collector which applies the mapping function to the input
* elements and provides the mapped results to the downstream
* collector
*/
static <A, R> IntCollector<?, R> mapping(IntUnaryOperator mapper, IntCollector<A, R> downstream) {
ObjIntConsumer<A> downstreamAccumulator = downstream.intAccumulator();
return new IntCollectorImpl<>(downstream.supplier(), (r, t) -> downstreamAccumulator.accept(r, mapper
.applyAsInt(t)), downstream.merger(), downstream.finisher(), downstream.characteristics());
}
/**
* Adapts a {@link Collector} accepting elements of type {@code U} to an
* {@code IntCollector} by applying a mapping function to each input element
* before accumulation.
*
* @param <U> type of elements accepted by downstream collector
* @param <A> intermediate accumulation type of the downstream collector
* @param <R> result type of collector
* @param mapper a function to be applied to the input elements
* @param downstream a collector which will accept mapped values
* @return a collector which applies the mapping function to the input
* elements and provides the mapped results to the downstream
* collector
*/
static <U, A, R> IntCollector<?, R> mappingToObj(IntFunction<U> mapper, Collector<U, A, R> downstream) {
BiConsumer<A, U> accumulator = downstream.accumulator();
if (downstream instanceof MergingCollector) {
return new IntCollectorImpl<>(downstream.supplier(), (acc, i) -> accumulator.accept(acc, mapper.apply(i)),
((MergingCollector<U, A, R>) downstream).merger(), downstream.finisher(), downstream
.characteristics());
}
return Box.partialCollector(downstream).asInt((box, i) -> accumulator.accept(box.a, mapper.apply(i)));
}
/**
* Returns an {@code IntCollector} which performs a reduction of its input
* numbers under a specified {@link IntBinaryOperator}. The result is
* described as an {@link OptionalInt}.
*
* @param op an {@code IntBinaryOperator} used to reduce the input numbers
* @return an {@code IntCollector} which implements the reduction operation.
*/
static IntCollector<?, OptionalInt> reducing(IntBinaryOperator op) {
return of(PrimitiveBox::new, (box, i) -> {
if (!box.b) {
box.b = true;
box.i = i;
} else {
box.i = op.applyAsInt(box.i, i);
}
}, (box1, box2) -> {
if (box2.b) {
if (!box1.b) {
box1.from(box2);
} else {
box1.i = op.applyAsInt(box1.i, box2.i);
}
}
}, PrimitiveBox::asInt);
}
/**
* Returns an {@code IntCollector} which performs a reduction of its input
* numbers under a specified {@code IntBinaryOperator} using the provided
* identity.
*
* @param identity the identity value for the reduction (also, the value
* that is returned when there are no input elements)
* @param op an {@code IntBinaryOperator} used to reduce the input numbers
* @return an {@code IntCollector} which implements the reduction operation
*/
static IntCollector<?, Integer> reducing(int identity, IntBinaryOperator op) {
return of(() -> new int[] { identity }, (box, i) -> box[0] = op.applyAsInt(box[0], i),
(box1, box2) -> box1[0] = op.applyAsInt(box1[0], box2[0]), UNBOX_INT);
}
/**
* Returns an {@code IntCollector} which returns summary statistics for the
* input elements.
*
* @return an {@code IntCollector} implementing the summary-statistics
* reduction
*/
static IntCollector<?, IntSummaryStatistics> summarizing() {
return of(IntSummaryStatistics::new, IntSummaryStatistics::accept, IntSummaryStatistics::combine);
}
/**
* Returns an {@code IntCollector} which partitions the input elements
* according to an {@code IntPredicate}, and organizes them into a
* {@code Map<Boolean, int[]>}.
*
* There are no guarantees on the type, mutability, serializability, or
* thread-safety of the {@code Map} returned.
*
* @param predicate a predicate used for classifying input elements
* @return an {@code IntCollector} implementing the partitioning operation
*/
static IntCollector<?, Map<Boolean, int[]>> partitioningBy(IntPredicate predicate) {
return partitioningBy(predicate, toArray());
}
/**
* Returns an {@code IntCollector} which partitions the input numbers
* according to an {@code IntPredicate}, reduces the values in each
* partition according to another {@code IntCollector}, and organizes them
* into a {@code Map<Boolean, D>} whose values are the result of the
* downstream reduction.
*
* <p>
* There are no guarantees on the type, mutability, serializability, or
* thread-safety of the {@code Map} returned.
*
* @param <A> the intermediate accumulation type of the downstream collector
* @param <D> the result type of the downstream reduction
* @param predicate a predicate used for classifying input elements
* @param downstream an {@code IntCollector} implementing the downstream
* reduction
* @return an {@code IntCollector} implementing the cascaded partitioning
* operation
*/
static <A, D> IntCollector<?, Map<Boolean, D>> partitioningBy(IntPredicate predicate, IntCollector<A, D> downstream) {
ObjIntConsumer<A> downstreamAccumulator = downstream.intAccumulator();
ObjIntConsumer<BooleanMap<A>> accumulator = (result, t) -> downstreamAccumulator.accept(
predicate.test(t) ? result.trueValue : result.falseValue, t);
return BooleanMap.partialCollector(downstream).asInt(accumulator);
}
/**
* Returns an {@code IntCollector} implementing a "group by" operation on
* input numbers, grouping them according to a classification function, and
* returning the results in a {@code Map}.
*
* <p>
* The classification function maps elements to some key type {@code K}. The
* collector produces a {@code Map<K, int[]>} 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.
*
* <p>
* There are no guarantees on the type, mutability, serializability, or
* thread-safety of the {@code Map} objects returned.
*
* @param <K> the type of the keys
* @param classifier the classifier function mapping input elements to keys
* @return an {@code IntCollector} implementing the group-by operation
*/
static <K> IntCollector<?, Map<K, int[]>> groupingBy(IntFunction<? extends K> classifier) {
return groupingBy(classifier, toArray());
}
/**
* Returns an {@code IntCollector} 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
* {@code IntCollector}.
*
* <p>
* The classification function maps elements to some key type {@code K}. The
* downstream collector produces a result of type {@code D}. The resulting
* collector produces a {@code Map<K, D>}.
*
* <p>
* There are no guarantees on the type, mutability, serializability, or
* thread-safety of the {@code Map} returned.
*
* @param <K> the type of the keys
* @param <A> the intermediate accumulation type of the downstream collector
* @param <D> the result type of the downstream reduction
* @param classifier a classifier function mapping input elements to keys
* @param downstream an {@code IntCollector} implementing the downstream
* reduction
* @return an {@code IntCollector} implementing the cascaded group-by
* operation
*/
static <K, D, A> IntCollector<?, Map<K, D>> groupingBy(IntFunction<? extends K> classifier,
IntCollector<A, D> downstream) {
return groupingBy(classifier, HashMap::new, downstream);
}
/**
* Returns an {@code IntCollector} 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
* {@code IntCollector}. The {@code Map} produced by the Collector is
* created with the supplied factory function.
*
* <p>
* The classification function maps elements to some key type {@code K}. The
* downstream collector produces a result of type {@code D}. The resulting
* collector produces a {@code Map<K, D>}.
*
* @param <K> the type of the keys
* @param <A> the intermediate accumulation type of the downstream collector
* @param <D> the result type of the downstream reduction
* @param <M> the type of the resulting {@code Map}
* @param classifier a classifier function mapping input elements to keys
* @param downstream an {@code IntCollector} implementing the downstream
* reduction
* @param mapFactory a function which, when called, produces a new empty
* {@code Map} of the desired type
* @return an {@code IntCollector} implementing the cascaded group-by
* operation
*/
static <K, D, A, M extends Map<K, D>> IntCollector<?, M> groupingBy(IntFunction<? extends K> classifier,
Supplier<M> mapFactory, IntCollector<A, D> downstream) {
Supplier<A> downstreamSupplier = downstream.supplier();
Function<K, A> supplier = k -> downstreamSupplier.get();
ObjIntConsumer<A> downstreamAccumulator = downstream.intAccumulator();
ObjIntConsumer<Map<K, A>> accumulator = (m, t) -> {
K key = Objects.requireNonNull(classifier.apply(t));
A container = m.computeIfAbsent(key, supplier);
downstreamAccumulator.accept(container, t);
};
return PartialCollector.grouping(mapFactory, downstream).asInt(accumulator);
}
/**
* Returns an {@code IntCollector} that produces the {@link BitSet} of the
* input elements.
*
* @return an {@code IntCollector} that produces the {@link BitSet} of the
* input elements
*/
static IntCollector<?, BitSet> toBitSet() {
return of(BitSet::new, BitSet::set, BitSet::or);
}
/**
* Returns an {@code IntCollector} that produces the array of the input
* elements. If no elements are present, the result is an empty array.
*
* @return an {@code IntCollector} that produces the array of the input
* elements
*/
static IntCollector<?, int[]> toArray() {
return of(IntBuffer::new, IntBuffer::add, IntBuffer::addAll, IntBuffer::toArray);
}
/**
* Returns an {@code IntCollector} that produces the {@code byte[]} array of
* the input elements converting them via {@code (byte)} casting. If no
* elements are present, the result is an empty array.
*
* @return an {@code IntCollector} that produces the {@code byte[]} array of
* the input elements
*/
static IntCollector<?, byte[]> toByteArray() {
return of(ByteBuffer::new, ByteBuffer::add, ByteBuffer::addAll, ByteBuffer::toArray);
}
/**
* Returns an {@code IntCollector} that produces the {@code char[]} array of
* the input elements converting them via {@code (char)} casting. If no
* elements are present, the result is an empty array.
*
* @return an {@code IntCollector} that produces the {@code char[]} array of
* the input elements
*/
static IntCollector<?, char[]> toCharArray() {
return of(CharBuffer::new, CharBuffer::add, CharBuffer::addAll, CharBuffer::toArray);
}
/**
* Returns an {@code IntCollector} that produces the {@code short[]} array
* of the input elements converting them via {@code (short)} casting. If no
* elements are present, the result is an empty array.
*
* @return an {@code IntCollector} that produces the {@code short[]} array
* of the input elements
*/
static IntCollector<?, short[]> toShortArray() {
return of(ShortBuffer::new, ShortBuffer::add, ShortBuffer::addAll, ShortBuffer::toArray);
}
/**
* Returns an {@code IntCollector} which produces a boolean array containing
* the results of applying the given predicate to the input elements, in
* encounter order.
*
* @param 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.
* @return an {@code IntCollector} which collects the results of the
* predicate function to the boolean array, in encounter order.
* @since 0.3.8
*/
static IntCollector<?, boolean[]> toBooleanArray(IntPredicate predicate) {
return PartialCollector.booleanArray().asInt((box, t) -> {
if (predicate.test(t))
box.a.set(box.b);
box.b = StrictMath.addExact(box.b, 1);
});
}
}