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/*
* esodata - data structures of varying utility
* Copyright 2022, Ben Culkin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bjc.data;
import java.util.*;
import java.util.function.Function;
/**
* Various utilities for dealing w/ collections
* @author bjcul
*
*/
public class CollectionUtils {
/**
* Create a function that converts a collection into a map.
*
* @param <Val> The type of the values in the map
* @param <Idx> The type of the keys in the map
* @param <Ent> The type of the values in the collection
*
* @param keyFunc The function that determines keys
* @param valFunc The function that determines values
*
* @return A function which uses the provided function to create a map from a
* collection.
*/
public static <Val, Idx, Ent> Function<Collection<Ent>, Map<Idx, Val>> indexBy(Function<Ent, Idx> keyFunc,
Function<Ent, Val> valFunc) {
return (coll) -> {
Map<Idx, Val> mep = new HashMap<>();
for (Ent ent : coll) {
mep.put(keyFunc.apply(ent), valFunc.apply(ent));
}
return mep;
};
}
}
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