Method parametrized with one type accepts two types

Question

Probably I am missing something and maybe my assumptions were wrong, but I thought that when I declare parametrized method with type T then no matter how much variables there are with that type it is still the same type. But I see that this compiles and it oposses my view.

static <T> void f(T a, T b) { }

public static void main(String[] args) {
    f(Integer.MIN_VALUE, "...");
}

So if my method is parametrized with one type and I am using that one type in two paramteres why does it allow me to send two objects with two totally different types? I guess it comes down to treating T as Object?

Answer 1

Although Integer and String are two different types, they still share a common super-type. Serializable.

To verify this, lets return T,

static <T> T f(T a, T b) {
    return null;
}
Serializable s = f(Integer.MIN_VALUE, "..."); // compiles

The compiler will resolve (or infer, not sure about the technical term) to the most specific type. For example,

Number number = f(Integer.MAX_VALUE, BigDecimal.ONE); 

Now, the type resolved is Number because both types are subtypes of Number,as well as Serializable, as well as Object of course.