Finding the right Collection

Question

Hello,
I am preparing a small, local database (Collection + Serialization)
I want to choose the right Collection.
I have patients which are recognized by ID which is the key,
but I would like to sort the Database's elements by one of the field which is in the VALUE (by name)
I am accessing Collection values by ID of course.
(during search, deleting, updating elements)
I am looking for some kind of structure
that has two keys. (key1, key2, value)
or maybe (keys[2], value) ?
Is it possible?
Any suggestions? ;))

Answer 1

If however you need to traverse the keys in a
sorted order then TreeMap is better alternative.
This senetence convinced me to choose TreeMap in both
cases.
So you mean, that I have to make one Object:
Person p = new Person();and add it twice?Exactly. You will have only on Object.
Map by_name = new TreeMap(Name, p);
Map by_ID = new TreeMap(ID, p);and then use the Map that I need?
Still questions to come:
What about the matter of those two fields: Name,
ID?
I mean I need them too, so for instance if I use the
Name key
I will not have the access to the ID key,
so shall I add it to the Person class anyway?I would have imagined that the ID would already be a member of the Person class, given that you need it for more than lookups. Another option would be to make the second map relate names to IDs. This would mean doing an extra lookup when you search by name, of course.
Both of them?Both of what, now?
and how to make a map allow multiple value's per key?
(need them for Name key)
//add
List persons = (List) namesToPersons.get(name);
if (persons == null)
    persons = new ArrayList();
    namesToPersons.put(name, persons);
persons.add(newPerson);Got the idea?