MultiMap.java

/**
 * Copyright (C) 2015 drrb
 *
 * 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 <http://www.gnu.org/licenses/>.
 */
package com.github.drrb.rust.netbeans.parsing.index;

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

/**
 *
 */
public class MultiMap<K, V> {

    @SuppressWarnings("CollectionWithoutInitialCapacity")
    private final Map<K, List<V>> map = new HashMap<>();

    public List<V> get(K key) {
        List<V> values = map.get(key);
        if (values == null) {
            return Collections.emptyList();
        } else {
            return Collections.unmodifiableList(values);
        }
    }

    public void add(K key, V value) {
        List<V> values = map.get(key);
        if (values == null) {
            values = new LinkedList<>();
            map.put(key, values);
        }
        values.add(value);
    }
}