org.aksw.commons.collections.multimaps.MultimapUtils Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of aksw-commons-collections Show documentation
There is a newer version: 0.9.9
Show newest version
package org.aksw.commons.collections.multimaps;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;

import org.aksw.commons.collections.MultiMaps;

import com.google.common.collect.ListMultimap;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;
import com.google.common.collect.SetMultimap;
import com.google.common.collect.Sets;

/**
 * Created by IntelliJ IDEA.
 * User: raven
 * Date: 4/25/11
 * Time: 9:26 PM
 * To change this template use File | Settings | File Templates.
 */
public class MultimapUtils {

    public static  Multimap groupBy(Iterable items, Function itemToGroupKey, Multimap result) {
        for(T item : items) {
            G groupKey = itemToGroupKey.apply(item);
            result.put(groupKey, item);
        }

        return result;
    }

    public static  SetMultimap newSetMultimap(boolean identityKeys, boolean identityValues) {
        Map> keys = identityKeys ? Maps.newIdentityHashMap() : new HashMap<>();
        com.google.common.base.Supplier> values = identityValues ? Sets::newIdentityHashSet : HashSet::new;

        return Multimaps.newSetMultimap(keys, values);
    }

    public static  SetMultimap newIdentitySetMultimap() {
        return Multimaps.newSetMultimap(Maps.newIdentityHashMap(), Sets::newIdentityHashSet);
    }

    public static  ListMultimap newIdentityListMultimap() {
        return Multimaps.newListMultimap(Maps.newIdentityHashMap(), ArrayList::new);
    }

    public static  Set getAll(Multimap multiMap, Collection keys) {
        Set result = keys.stream()
                .flatMap(k -> multiMap.get(k).stream())
                .collect(Collectors.toSet());
        return result;
    }


    /**
     * A transitive get in both directions
     *
     * @param map
     */
    public static  Set transitiveGetBoth(IBiSetMultimap map, Object key)
    {
        Set result = MultiMaps.transitiveGet(map.asMap(), key);
        result.addAll(MultiMaps.transitiveGet(map.getInverse().asMap(), key));

        return result;
    }

    /**
     * Helper function to convert a multimap into a map.
     * Each key may only have at most one corresponding value,
     * otherwise an exception will be thrown.
     *
     * @param mm
     * @return
     */
    public static  Map toMap(Map> mm) {
        // Convert the multimap to an ordinate map
        Map result = new HashMap();
        for(Entry> entry : mm.entrySet()) {
            K k = entry.getKey();
            Collection vs = entry.getValue();

            if(!vs.isEmpty()) {
                if(vs.size() > 1) {
                    throw new RuntimeException("Ambigous mapping for " + k + ": " + vs);
                }

                V v = vs.iterator().next();
                result.put(k, v);
            }
        }

        return result;
    }
}