Java Generics: Useing multiple generic types in one collection type

Question

I would like to use two generic types as a key for a hash map. Effectively:

Map<CollectionType<Integer, Integer>, Character> map = new HashMap<>();

I am trying to find if this is possible, and if so which collection type I could use. The right type needs to be able to accept duplicate values. i.e. <1, 0>, <1, 1>, <2, 0> could all be used as a key in the map

for additional background the key in the map will be coordinates on a hex grid, and the value is what is currently stored at that location.

*The right type needs to be able to accept duplicate values.* What do you mean? Maps don't allow duplicate keys. — shmosel, Nov 20 '18 at 03:43
maybe use a pair: https://stackoverflow.com/questions/156275/what-is-the-equivalent-of-the-c-pairl-r-in-java ? — Ray Tayek, Nov 20 '18 at 03:44
@secretsuperstar no the combination of integers will always be unique. — jwmorse, Nov 20 '18 at 03:59

score 3 · Accepted Answer · answered Nov 20 '18 at 03:46

Use a Pair<Integer, Integer>, provided by many libraries like in org.apache.commons.lang3.tuple.Pair or in jdk as javafx.util.Pair.

equals() and hashcode() are overridden, so it can work as a key in the Map.

Map<Pair<Integer, Integer>, Character> map = new HashMap<>();

Java Generics: Useing multiple generic types in one collection type

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