Can the generic type of a generic Java method be used to enforce the type of arguments?

Question

I would like to use a generic type to ensure, that the arguments of a method are of the same type, like this:

public static <T> void x(T a, T b) 

I would assume that the two arguments (a and b), that are passed to this method, would always have to be of the same type. But to my surprise I was able to pass arguments of any type (even primitives) to method x, as if T is erased to Object, no matter what arguments are passed.

The only work-around I found so far, was to use 'extends' like this:

public static <T, U extends T> void x(T a, U b) 

But although I can live with it, it is not what I wanted.

Is there a way to use a generic type to force the type of all arguments of a method?

Answer 1

If I understand correctly, one way to do it is to explicitly specify the type of T instead of letting the compiler infer its type to be of the most direct superclass in the case of two objects of different types being passed in as arguments. Take something like this, for example:

public class Test {     public static void main(String[] args) {         Test.x(5.0, 5);          // This works since type is inferred to be Number         Test.<Integer>x(5, 5);   // This works since type is stated to be Integer         Test.<Integer>x(5.0, 5); // This doesn't; type is stated to be Integer and Double is passed in     }      public static <T> void x(T a, T b) {     } }