Can't cast to ParameterizedType

Question

I am trying to get a Class<?> instance for the generic type. There is a lot of answers how to do that, but I am getting the error:

java.lang.ClassCastException: class java.lang.Class cannot be cast to class java.lang.reflect.ParameterizedType (java.lang.Class and java.lang.reflect.ParameterizedType are in module java.base of loader 'bootstrap')

I use Java 17. The code to reproduce the error:

class GenericTypeTest {
    @Test
    void showsTheError() {
        Generic<String> g = new Generic<>();
        assertEquals(String.class, g.getType());
    }

    static class Generic<T> {
        Class<?> getType() {
            Type type = getClass().getGenericSuperclass();
            ParameterizedType paramType = (ParameterizedType) type;
            return (Class<?>) paramType.getActualTypeArguments()[0];
        }
    }
}

Answer 1

The superclass of Generic<T> is Object, which isn't generic.

You need to subclass Generic for this to work:

Generic<String> g = new Generic<>() {};

Consider making Generic abstract in order to force it to be subclassed in order to instantiate it.