A Hashmap stores values as [key - value] pairs, where distinct keys act as 'references' for the values stored.
You should decide how you want to store the values. Usually for storing an object in a Map we store it as the value along with the ID for this element as the key.
i.e. hashmap.add(id, object);
Why is the requirement that the elements have to be stored in a Map? As they appear to be a heterogeneous collection I would think of a different collection (unless they are connected in some different way).
Cheers,
Rajkamal.