Java reflection, get the name of a generic class parameter

Question

I would like to get the name of a generic parameter of a class. For instance :

public class A<B> {
...
}

and in this class i would like to the name of the class B. Like :

A<Solution> var = new A<Solution>();

I would like to have a way to have the String "Solution" somewhere in a method of A

If you have any idea i am here :)

Thank you !

Andy Turner · Accepted Answer · 2016-04-18 22:17:21Z

3

You would need to pass in the Class instance as a constructor parameter:

class A<B> {
  private final Class<B> clazz;

  A(Class<B> clazz) {
    this.clazz = clazz;
  }

  String getName() {
   return clazz.getSimpleName();
  }
}

A<Solution> var = new A<>(Solution.class);

answered Apr 18, 2016 at 22:17

Andy Turner

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5 Comments

shmosel Over a year ago

You can also get it by subclassing A. See Guava's TypeToken or Jackson's TypeReference for examples.

Andy Turner Over a year ago

@shmosel that would be an appropriate solution if B needs to be generic. Would you consider adding that as another answer?

shmosel Over a year ago

You need to have an explicit type either way, e.g., new A<Solution>() {}. It's just a bit cleaner, especially if you need to capture multiple type parameters.

Andy Turner Over a year ago

@shmosel Yes. But it's a different approach (it's the inheritance approach, whereas mine is the compositional approach), so you should add it as an alternative answer.

shmosel Over a year ago

I don't have the patience to write it up now. Feel free to do so.

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