| /* |
| * Copyright 2016 Google Inc. |
| * |
| * 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 java.util.stream; |
| |
| import static javaemul.internal.InternalPreconditions.checkNotNull; |
| |
| import java.util.Collections; |
| import java.util.EnumSet; |
| import java.util.Set; |
| import java.util.function.BiConsumer; |
| import java.util.function.BinaryOperator; |
| import java.util.function.Function; |
| import java.util.function.Supplier; |
| |
| /** |
| * See <a |
| * href="https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collector.html">the |
| * official Java API doc</a> for details. |
| * @param <T> the type of data to be collected |
| * @param <A> the type of accumulator used to track results |
| * @param <R> the final output data type |
| */ |
| public interface Collector<T,A,R> { |
| |
| /** |
| * See <a |
| * href="https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collector.Characteristics.html"> |
| * the official Java API doc</a> for details. |
| */ |
| enum Characteristics { CONCURRENT, IDENTITY_FINISH, UNORDERED } |
| |
| static <T, A, R> Collector<T, A, R> of( |
| Supplier<A> supplier, |
| BiConsumer<A, T> accumulator, |
| BinaryOperator<A> combiner, |
| Function<A, R> finisher, |
| Characteristics... characteristics) { |
| checkNotNull(supplier); |
| checkNotNull(accumulator); |
| checkNotNull(combiner); |
| checkNotNull(finisher); |
| checkNotNull(characteristics); |
| return new CollectorImpl<>( |
| supplier, |
| accumulator, |
| combiner, |
| finisher, |
| characteristics |
| ); |
| } |
| |
| static <T, R> Collector<T, R, R> of( |
| Supplier<R> supplier, |
| BiConsumer<R, T> accumulator, |
| BinaryOperator<R> combiner, |
| Characteristics... characteristics) { |
| checkNotNull(supplier); |
| checkNotNull(accumulator); |
| checkNotNull(combiner); |
| checkNotNull(characteristics); |
| return new CollectorImpl<T, R, R>( |
| supplier, |
| accumulator, |
| combiner, |
| Function.identity(), |
| Collections.unmodifiableSet(EnumSet.of(Characteristics.IDENTITY_FINISH, characteristics)) |
| ); |
| } |
| |
| Supplier<A> supplier(); |
| |
| BiConsumer<A,T> accumulator(); |
| |
| Set<Characteristics> characteristics(); |
| |
| BinaryOperator<A> combiner(); |
| |
| Function<A,R> finisher(); |
| |
| /** |
| * Simple internal implementation of a collector, holding each of the functions in a field. |
| */ |
| final class CollectorImpl<T, A, R> implements Collector<T, A, R> { |
| private final Supplier<A> supplier; |
| private final BiConsumer<A, T> accumulator; |
| private final Set<Characteristics> characteristics; |
| private final BinaryOperator<A> combiner; |
| private final Function<A, R> finisher; |
| |
| public CollectorImpl( |
| Supplier<A> supplier, |
| BiConsumer<A, T> accumulator, |
| BinaryOperator<A> combiner, |
| Function<A, R> finisher, |
| Characteristics... characteristics) { |
| this.supplier = supplier; |
| this.accumulator = accumulator; |
| if (characteristics.length == 0) { |
| this.characteristics = Collections.emptySet(); |
| } else if (characteristics.length == 1) { |
| this.characteristics = Collections.singleton(characteristics[0]); |
| } else { |
| this.characteristics = |
| Collections.unmodifiableSet(EnumSet.of(characteristics[0], characteristics)); |
| } |
| this.combiner = combiner; |
| this.finisher = finisher; |
| } |
| |
| public CollectorImpl( |
| Supplier<A> supplier, |
| BiConsumer<A, T> accumulator, |
| BinaryOperator<A> combiner, |
| Function<A, R> finisher, |
| Set<Characteristics> characteristics) { |
| this.supplier = supplier; |
| this.accumulator = accumulator; |
| this.combiner = combiner; |
| this.finisher = finisher; |
| this.characteristics = characteristics; |
| } |
| |
| @Override |
| public Supplier<A> supplier() { |
| return supplier; |
| } |
| |
| @Override |
| public BiConsumer<A, T> accumulator() { |
| return accumulator; |
| } |
| |
| @Override |
| public BinaryOperator<A> combiner() { |
| return combiner; |
| } |
| |
| @Override |
| public Function<A, R> finisher() { |
| return finisher; |
| } |
| |
| @Override |
| public Set<Characteristics> characteristics() { |
| return characteristics; |
| } |
| } |
| } |