Question

I seem to have a bit of misunderstanding with Java Generics and I hope you can help me. I tried to create a map like so:

Map<Debater, int>

(Debater is an Interface I declared) but java complained about the int, so I did:

Map<Debater, Integer>

I suppose it’s because int is not a class while Integer is, is this correct?

Also, Now I get a Debater and I need to add 1 to its value in the map. How do I do that?

Answer 1

Yes, you are correct.

As for incrementing:

map.put(debater, map.get(debater) + 1);

Autoboxing will take care of “switching” between the object and the primitive.

Note that this (as noted in the comments) will throw a NullPointerException if you don’t have a value for this debater in the map already. So if you want to do 2-in-1, it can be reworked as follows:

map.put(debater, map.containsKey(debater) ? map.get(debater) + 1 : 1);