public class ComparableDemo2
{
   public static void main(String[] args)
   {
      Comparable student1 = new HighSchoolStudent(3.0, "Angie", 56);
      Comparable student2 = new HighSchoolStudent(2.9, "Bill", 72);
      
      Comparable student3 = new ElementarySchoolStudent(100, "Colleen");
      Comparable student4 = new ElementarySchoolStudent(12, "David");
      
      // System.out.println(student1.getName());   // compile error since student1 is "cloaked" in this program as a Comparable reference and getName isn't a method listed in the Comparable interface
      System.out.println(((HighSchoolStudent) student1).getName());  // valid since student1 is temporarily casted to the HighSchoolStudent that it really is "deep down"

      if (student1.compareTo(student2) > 0)
      {
         System.out.println(student1.toString() + " IS GREATER THAN " + student2.toString());  // toString is optional
      }                                                              
      else if (student1.compareTo(student2) < 0)
      {
         System.out.println(student1 + " IS LESS THAN " + student2);
      }
      else
      {
         System.out.println(student1 + " IS EQUAL TO " + student2);
      }
      
      System.out.println("BEST HIGH SCHOOL STUDENT IS: " + compareStudents(student1, student2));  // use of toString is allowed since it is inherited from Object class
      System.out.println("BEST ELEMENTARY STUDENT IS: " + compareStudents(student3, student4));   // What if student4 were replaced by student2?
      
   }// end of main method
   
   public static Comparable compareStudents(Comparable studentA, Comparable studentB)  // this method is flexible, it can be passed HS or ElementarySchoolStudent objects!
   {                                                                                   // in fact, it could be passed objects from any of the hundreds of classes that realize the Comparable interface like String, Integer, etc.
      if (studentA.compareTo(studentB) > 0)
      {
         return studentA;
      }
      else if (studentA.compareTo(studentB) < 0)
      {
         return studentB;
      }
      
      return studentA;     // a reference to a whole HS or ElementarySchoolStudent object is being returned (valid since those classes implement Comparable)
   }
   
}// end of ComparableDemo2 class

////////////////////////////////////////////////////////

class HighSchoolStudent implements Comparable
{
   public HighSchoolStudent(double gpa, String name, int height)
   {
      myGPA = gpa;
      myName = name;
      myHeight = height;
   }
   
   public String getName()
   {
      return myName;
   }

   public int compareTo(Object other)
   {
      if (this.myGPA > ((HighSchoolStudent) other).myGPA)   // How would you modify this method to use height as a tiebreaker if GPA's are the same
      {
         return 1;
      }
      else if (this.myGPA < ((HighSchoolStudent) other).myGPA)  // this is optional, could be:  else if (myGPA < ((HighSchoolStudent)...
      {
         return -1;
      }

      return 0;                    // could place this in an else clause

      // return this.myHeight - ((HighSchoolStudent) other).myHeight;      // This single line return statement wouldn't work for myGPA since myGPA is a double and returning the double 1.0 isn't the same as returning an int 1 for example
      // return this.myName.compareTo(((HighSchoolStudent) other).myName); // making use of the String compareTo method within the HSStudent compareTo method!
   }
 
   public String toString()
   {
      return "name = " + myName + " GPA = " + myGPA + " height = " + myHeight;
   }

   private double myGPA;
   private String myName;
   private int myHeight;      // in inches
}

////////////////////////////////////////////////////////

class ElementarySchoolStudent implements Comparable
{
   public ElementarySchoolStudent(int workEthic, String name)
   {
      myWorkEthic = workEthic;
      myName = name;
   }

   public String getName()
   {
      return myName;
   }
   
   public int compareTo(Object other)
   {
      return this.myWorkEthic - ((ElementarySchoolStudent) other).myWorkEthic; 
   }
 
   public String toString()
   {
      return "name = " + myName + " work ethic = " + myWorkEthic;
   }

   private int myWorkEthic;
   private String myName;
}