A hashmap with duplicate key

public class DuplicateHashMap<K,V> extends HashMap<K, Array<V>> {
        public void put(K key, V value) {
            Array<V> current = get(key);
            if (current == null) {

                current = new Array<V>();
                super.put(key, current);
            }
            current.add(value);
        }
}