I would give your Car a constructor taking all the fields, and I would get rid of the
setXXX() methods. Why would you want
setXXX() methods in the first place, since those data should never change? You might like to extend the process I have started and make the Car object completely immutable.
As an alternative to Pair, you can create a class called
MakeModel or something like that. In order to work as a “K” in a Map, that class needs correctly‑overridden
hashCode() and
equals() methods.
[edit]Additional: I presume this is the
Pair class that Piet mentioned. It already appears to have overridden
hashCode() and
equals() methods.