//An instance of this class represents an FIU letter grade
//
public class FIUCourseGrade
{
   public static final double ONE_THIRD = 1.0/3.0;
   
   //Instance Variable
   private String grade;
   
   //Constructor
   // Legal Letter Grades: A, A-, B+, B, B-, C+, C, D, F
   public FIUCourseGrade(String grade)
   {
      if ( grade.length() < 1 || grade.length() > 2 )    //Length check: 1 or 2
         throw new RuntimeException("Invalid Length");
      
      if ( !hasValidLetter(grade) )                      //Letter Check: A, B, C, D, or F
          throw new RuntimeException("Invalid Letter");
          
      if ( grade.length() == 2 && !hasValidSuffix(grade))//Suffix Check: + or -
          throw new RuntimeException("Invalid Suffix");
            
      this.grade = grade;
   }
   
   //Accessor
   public String getGrade()
   {
      return this.grade;
   }
   
   //Query Method
   // @return grade-points corresponding to this grade
   public double gradePoints()
   {
      double points = 0.0;
      
      //Calculate the "letter" points: 4, 3, 2, 1, 0
      switch ( this.grade.charAt(0) )
      {
         case 'A' : points = 4.0;
                     break;
         case 'B' : points = 3.0;
                     break;
         case 'C' : points = 2.0;
                     break;
         case 'D' : points = 1.0;
                     break;
      }
      
      //Modify by +/- 1/3 if there is a suffix
      if (this.grade.length() == 2)
         switch (this.grade.charAt(1))
         {
            case '+' : points += ONE_THIRD; break;
            case '-' : points -= ONE_THIRD;
         }
            
      return points;
   }

   //Helper Method
   // @param grade: a String to be validated as a letter grade
   // @return  true IFF the 1st char is legitimate: A, B, C, D, F
   private static boolean hasValidLetter(String grade)
   {
      switch ( grade.charAt(0) )
      {
         case 'A' :
         case 'B' :
         case 'C' :
         case 'D' :
         case 'F' :  return true; 
         default  :  return false;
      }
   }
   
   //Helper Method
   // @param grade: a String to be validated as a letter grade
   // @return  true IFF the 2nd char, if any, is legitimate: + or -
   private static boolean hasValidSuffix(String grade)
   {
      if (grade.length() != 2)
         return false;
         
      char letter = grade.charAt(0);
      char suffix = grade.charAt(1);
      
      switch ( suffix )
      {
         case '+' : return (letter == 'B' || letter == 'C');
         case '-' : return (letter == 'A' || letter == 'B');
         default  : return false;
      }
   }
}