File with constants declared?

Question

How do I create a file with some constants declared? Do I have to make a class out of them? Then, how do I import the file into other classes?

Answer 1

Here's what I have:
interface ConvertTypes
     public static final int IDC = 1,MDS = 2, IDC_AND_MDS = 3;
class ctest implements ConvertTypes
     public static void main(String[] args)
          System.out.println(IDC);
Here's the error I get after I compile ConvertTypes and ctest:
Z:\ctest.java:1: cannot resolve symbol
symbol : class ConvertTypes
location: class ctest
class ctest implements ConvertTypes
^
Z:\\ctest.java:5: cannot resolve symbol
symbol : variable IDC
location: class ctest
          System.out.println(IDC);