Multiple Inhertiance Using Interfaces

class Person
{
   public Person () {}
   public Person (String n) { name = n; }
   public String toString() { return name; }
   public String idString() { return null; }

   String  name;
}

class Student extends Person
{
   public Student (String n, String i) { super(n); id = i; }
   public String toString()
   {
      return super.toString() + " Today";
   }
   public String idString() {  return id;  }

   String id;
}

class Employee extends Person
{
   public Employee (String n, String i) {  super(n); id = i;  }
   public String idString() {  return id;  }

   String id;
}

interface EmployeeInterface
{
}

class StudentEmployee extends Student implements EmployeeInterface
{
   public StudentEmployee (String n, String i) { super(n,i); }
   // String idString() { return super.idString(); } // no longer needed
}

public class Students
{
   public static void main(String arg[])
   {
      Student joan = new Student("Joan","100");
      System.out.println(joan.toString());
      StudentEmployee john = new StudentEmployee("John","123");
      System.out.println(john.toString());
      System.out.println(john.idString());
   }
}