public class Student implements Person {
  String id;
  String name;
  int age;
  public Student (String i, String n, int a) { // simple constructor
    id = i;
    name = n;
    age = a;
  }
  protected int studyHours() { return age/2; } // just a guess
  public String getID () { return id; } // ID of the student
  public String getName() { return name; } // from Person interface
  public int getAge() { return age; } // from Person interface
  public boolean equalTo (Person other) { // from Person interface
    Student otherStudent = (Student) other;	// cast Person to Student
    return (id.equals (otherStudent.getID()));	// compare IDs
  }
}