Strings can, of course be values in a hastable, but what does that have to do with the rest of the question?
What do you mean by "method generated Strings" and "plug them into another method"?
Also, whatever it is, HashMap would probably be a better choice than Hashtable, unless you have some specific reason for synchronizing access to it.
Basically I have a method (tokenizer, but thinking about looking at regex) which splits an input string into smaller strings are r and k and i want to be able to used those substrings to calculate the mass of them (from values stored in a hashmap). So probably thinking about it I'll need to make an array of substrings?