Your problem is that you are not using the correct form of calculateDogYears(). You define the method as calculateDogYears(int,int) but only called it with one arg.
Error:
Chicken-of-the-PowerBook:~/devel/java jowings$ javac DogsHumanAge.java
DogsHumanAge.java:42: calculateDogyears(int,int) in DogsHumanAge cannot be applied to (int)
double Dogyears = calculateDogyears(Humanyears);
^
1 error
I would guess that you meant to do something like this:
private double calculateDogyears(int Humanyears)
{
return 13 + (int)(16.0 / 3.0 * (Humanyears - 1));
}
//SIDEBAR: please use the CODE tags when posting code. It makes things so very much easier to read.