class ParamTest {

    public static void testParams(Student s, int num) {
        num = 20; // doesn't change count: this is only a copy of it.
        s.setFirstName("Rudiger");  // works: follow (copied) reference 
                                    // & change contents
        s = new Student(300067890, "someguy"); // doesn't change s1, just
                                               // changes s from a copy of s1 to
                                               // a reference to a new Student.
    }

    public static void main(String[] args) {
        Student s1 = new Student(300012345, "userid");
        int count = 10;
        s1.setLastName("Simpson");
        
        testParams(s1, count);
        
        System.out.println(s1);    // 300012345: Simpson, Rudiger
        System.out.println(count); // 10
    }

}