Exercise Solutions: Classes and Objects, Part 2

The getGradeLevel Method

This method returns the student’s level based on the number of credits they have earned: Freshman (0-29 credits), Sophomore (30-59 credits), Junior (60-89 credits), or Senior (90+ credits).

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public static String getGradeLevel(int credits) {
   if (credits <= 29){
      return "freshman";
   } else if (credits <= 59){
      return "sophomore";
   } else if (credits <= 89) {
      return "junior";
   } else {
      return "senior";
   }
}

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The addGrade Method

This method accepts two parameters—a number of course credits and a numerical grade (0.0-4.0). With this data, you need to update the student’s GPA.

GPA Information

GPA is computed via the formula:

gpa = (total quality score) / (total number of credits)

  1. The quality score for a class is found by multiplying the letter grade score (0.0-4.0) by the number of credits.

  2. The total quality score is the sum of the quality scores for all classes.

For example, if a student received an “A” (worth 4 points) in a 3-credit course and a “B” (worth 3 points) in a 4-credit course, their total quality score would be: 4.0 * 3 + 3.0 * 4 = 24. Their GPA would then be 24 / 7 = 3.43.

Determine the New GPA

To update the student’s GPA:

  1. Calculate their current total quality score by using the formula gpa * numberOfCredits.

  2. Use the new course grade and course credits to update their total quality score.

  3. Update the student’s total numberOfCredits.

  4. Compute their new GPA.

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public void addGrade(int courseCredits, double grade) {
   double totalQualityScore = this.gpa * this.numberOfCredits;
   totalQualityScore += courseCredits * grade;
   this.numberOfCredits += courseCredits;
   this.gpa = totalQualityScore/this.numberOfCredits;
}

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toString and equals

  1. Add custom equals() and toString() methods to the Student class.

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    public String toString() {
   String studentReport = String.format("%s is a %s with %d credits and a GPA of %.2f", this.name, this.getGradeLevel(this.numberOfCredits), this.getNumberOfCredits(), this.getGpa());
   return studentReport;
}

public boolean equals(Object toBeCompared) {
   if (toBeCompared == this) {
      return true;
   }

   if (toBeCompared == null) {
      return false;
   }

   if (toBeCompared.getClass() != getClass()) {
      return false;
   }

   Student theStudent = (Student) toBeCompared;
   return theStudent.getStudentId() == getStudentId();
}

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