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javagenericsmappingtype-safety

Type-safe mapping from Class<T> to Thing<T>

I want to make a map-kind of container that has the following interface:

public <T> Thing<T> get(Class<T> clazz);
public <T> void put(Class<T> clazz, Thing<T> thing);

The interesting point is that the Ts in each Class<T> -> Thing<T> pair is the same T, but the container should be able to hold many different types of pairs. Initially I tried a (Hash)Map. But, for instance,

Map<Class<T>, Thing<T>>

is not right, because then T would be the same T for all pairs in that map. Of course,

Map<Class<?>, Thing<?>>

works, but then I don't have type-safety guarantees so that when I get(String.class), I can't be sure that I get a Thing<String> instance back.

Is there an obvious way to accomplish the kind of type safety that I'm looking for?

Solution

  • The map itself would not guarantee that, but if you are accessing it only through the above methods, you will have the desired safety.