ca.uhn.fhir.util.MultimapCollector Maven / Gradle / Ivy
/*-
* #%L
* HAPI FHIR - Core Library
* %%
* Copyright (C) 2014 - 2024 Smile CDR, 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.
* #L%
*/
package ca.uhn.fhir.util;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ListMultimap;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;
/**
* Copied from https://stackoverflow.com/questions/23003542/cleanest-way-to-create-a-guava-multimap-from-a-java-8-stream
*/
public class MultimapCollector implements Collector, ListMultimap> {
private final Function keyGetter;
private final Function valueGetter;
public MultimapCollector(Function keyGetter, Function valueGetter) {
this.keyGetter = keyGetter;
this.valueGetter = valueGetter;
}
public static MultimapCollector toMultimap(
Function keyGetter, Function valueGetter) {
return new MultimapCollector<>(keyGetter, valueGetter);
}
public static MultimapCollector toMultimap(Function keyGetter) {
return new MultimapCollector<>(keyGetter, v -> v);
}
@Override
public Supplier> supplier() {
return ArrayListMultimap::create;
}
@Override
public BiConsumer, T> accumulator() {
return (map, element) -> map.put(keyGetter.apply(element), valueGetter.apply(element));
}
@Override
public BinaryOperator> combiner() {
return (map1, map2) -> {
map1.putAll(map2);
return map1;
};
}
@Override
public Function, ListMultimap> finisher() {
return map -> map;
}
@Override
public Set characteristics() {
return ImmutableSet.of(Characteristics.IDENTITY_FINISH);
}
}