Help with generics - extending hashmap

Question

I'm trying to extend the HashMap class to accept multiple values per key. I'd like .put(key,value) to put a single key/value pair. I'd like .get(key) to return a Vector<V> of all the values associated with key, and .get(key, index) to return a single value of type V for that key. I am using Eclipse 3.2 and Java 1.5.
The problem I am having is my .put(K key,V value) method won't compile, I get the error:
Name clash: The method put(K,V) of type OneToManyHashMap<K,V> has the same erasure as put(K,V> of type HashMap<K,V> but does not override it
My code (roughly):
public class OneToManyHashMap<K,V> extends HashMap<K, Vector<V>> {
    public V get(Object key, int index) { return get(key).get(index); }
    public V put(K key, V value) { ... }
    public V remove(Object key, int index) { return get(key)
}Yes, I know there is an extra > in the code. It's wasn't there when I typed the message and it's not there when I try and edit the message to remove it :(
Message was edited by:
jiggersplat

Answer 1

This is what was meant by a "has-a" relation:
public class OneToManyHashMap&#60;K, V extends List&#60;V>> {
    public Map&#60;K, List&#60;V>> map;
    public OneToManyHashMap() { map = new HashMap&#60;K, List&#60;V>>(); }
    public V get(K key, int index) { return map.get(key).get(index); }
    public void put(K key, V value) { map.get(key).add(value); }
    public void remove(K key, int index) { map.get(key).remove(index); }
}Needless to say, you will have to perform some checks to handle eventual NPE's.