Question

if i have a method defined.

public static <T> T getSomeTea(Class<T> returnType) {
   //do stuff and return a T
}

public static <T> T getSomeSpecialTea(T someVal) {
   T someTea = (T) getSomeTea(someVal.getClass());
}

in getSomeSpecialTea, why do I need to cast the return from getSomeTea. it would seem to me the cast is unneccesary, but perhaps i’m missing something important.

Answer 1

Object.getClass() isn’t generic, so your code is effectively:

public static <T> T getSomeSpecialTea(T someVal) {
   Class<?> clazz = someVal.getClass();
   T someTea = (T) getSomeTea(clazz);
}

At that point is it clearer why you need the cast? (Not that the cast will really anything at execution time, of course…) You’re not calling <T>getSomeTea() which is what you really want to be doing, effectively.

It’s just another case of Java generics being a bit of a pain 🙁