How to read class types of generics parameters using Java reflection

Question

I have a class BaseClass<X, Y, Z>. And I implement the class as SuperCar implements BaseClass<Color, Engine, Foo>. So now i need to get those X,Y,Z values by using reflection on SuperCar class. Is this possible ?

I guess it is not possible, remember that Java generics use erasure, the type parameters are "forgotten" after compilation. E.g. `ArrayList` is compiled to `ArrayList — marek.jancuska, Mar 19 '15 at 14:46
There is a excellent answer on this post to explain how to do this. http://stackoverflow.com/questions/1901164/get-type-of-a-generic-parameter-in-java-with-reflection — APD, Mar 19 '15 at 14:52

score 1 · Accepted Answer · answered Mar 19 '15 at 14:48

You can inspect the type parameters for the superclass, having the Class of the SuperCar:

SuperCar car = new SuperCar();
ParameterizedType parameterizedType = (ParameterizedType) car.getClass().getGenericSuperclass();
Type[] superClassTypes = parameterizedType.getActualTypeArguments();
for (Type type : superClassTypes) {
    System.out.println(type.getTypeName());
}

This should give you:

Color
Engine
Foo

score 1 · Answer 2 · answered Mar 19 '15 at 14:53

i guess you want to have something like this:

ParameterizedType types = (ParameterizedType) SuperCar.class.getGenericInterfaces()[0];
for (Type type : types.getActualTypeArguments()) {
    Class<?> cl = (Class<?>) type;
    System.out.println(cl.getName());
}

instead of printing the name you can do whatever you like with it

How to read class types of generics parameters using Java reflection

2 Answers2