Question

Modify your PredictGPA.java file from Lab 2 to create a method called GPA that takes a string argument (the grade) and returns the corresponding value (ie 4.0 for an A, 3.33 for a B+, etc). Use this method call to reduce the “redundant” code that you had in Lab 2. The program must otherwise still run correctly as to the directions in Lab 2 and compute the GPA after using the method calls to determine the appropriate grade values. Trying to change the below Code to use Methods.

import java.util.Scanner;  // ** for Scanner

public class GPAMethod {
        public static void main(String[] args) {

            Scanner userInput = new Scanner(System.in); // Allows to scan in user input

            System.out.print("How many classes did you have?: "); //Asks how many classes
            int classes = userInput.nextInt(); //initializes and stores user input into classes


            String grades; // establishes the string grades
            double hours; // hours needs to be a double in the case the a class is 1.5 hours
            double gpa =0; // GPA also needs to be a double
            int i; // declare i for the FOR loop
            double sumGPA = 0; // this is how I will add up the GPA every time through the FOR loop
            double sumHours = 0; // this is how I will add up Class Hours every time through the FOR loop
            // gpa = 10; // tried to debug using this because it is not catching gpa in the loop


            for (i = 0; i < classes; i++) { // we want to set i to zero, and we know we want a FOR loop
                // because we will know how many classes based on user input
                // we want i to increase by 1 every time

                System.out.print("Expected Grade for class " + i + "?:");
                // have the user input the expected grade for each class, represented by i
                // this is where I dont understand how to get i = 1 for the first class
                // because we are dealing with strings I have to set i to zero?
                // I feel like this is a small issue but for syntax it would be nice to know
                grades = userInput.nextLine(); // user puts grade
                userInput.next(); // needed this line of code to separate the strings, otherwise
                // they were appearing next to each other, not sure why I had
                // to do this
                System.out.print("How many hours is class " + i + "?: "); // asks for user hours
                // concatenates class number
                hours = userInput.nextDouble(); // user input
                sumHours = hours + sumHours; // each time we go through the loop this
                // line of code adds the hours
                sumGPA =  (hours * gpa) + sumGPA; // each time through this calculates GPA

                if (grades.equals("A")) { // because user input is a string
                    // I did grades.equals()
                    gpa = 4;
                    // sumGPA = hours + gpa;

                } else if (grades.equals("A-")) { // I go through each and assign a double
                    // to gpa, given the user string
                    gpa = 3.67;

                } else if (grades.equals("B+")) { // I use else if because they are exclusive
                    gpa = 3.37;

                } else if (grades.equals("B")) {
                    gpa = 3;

                } else if (grades.equals("B-")) {
                    gpa = 2.67;

                } else if (grades.equals("C+")) {
                    gpa = 2.37;

                } else if (grades.equals("C")) {
                    gpa = 2;

                } else if (grades.equals("C-")) {
                    gpa = 1.67;

                } else if (grades.equals("D+")) {
                    gpa = 1.37;

                } else if (grades.equals("D")) {
                    gpa = 1;

                } else if (grades.equals("D-")) {
                    gpa = .67;

                } else if (grades.equals("F")) {
                    gpa = 0;

                }


            }

            double GPA =  sumGPA/sumHours; // at the end I want the sumGPA to be divided by the sum of hours
            System.out.println("Your Semester GPA would be " + GPA); // print statement that lets user
          
        }
    }

Answer 1

Program:

import java.util.Scanner; // ** for Scanner

public class GPAMethod {
   public static void main(String[] args) {
       Scanner userInput = new Scanner(System.in); // Allows to scan in user input

       System.out.print("How many classes did you have?: "); //Asks how many classes
       int classes = userInput.nextInt(); //initializes and stores user input into classes

       String grades; // establishes the string grades
       double hours; // hours needs to be a double in the case the a class is 1.5 hours
       double gpa =0; // GPA also needs to be a double
       int i; // declare i for the FOR loop
       double sumGPA = 0; // this is how I will add up the GPA every time through the FOR loop
       double sumHours = 0; // this is how I will add up Class Hours every time through the FOR loop
       // gpa = 10; // tried to debug using this because it is not catching gpa in the loop

       for (i = 0; i < classes; i++) { // we want to set i to zero, and we know we want a FOR loop
           // because we will know how many classes based on user input
           // we want i to increase by 1 every time

           System.out.print("Expected Grade for class " + i + "?:");
           userInput.nextLine(); // needed this line of code to separate the strings, otherwise
           // they were appearing next to each other, not sure why I had
           // to do this
           // have the user input the expected grade for each class, represented by i
           // this is where I dont understand how to get i = 1 for the first class
           // because we are dealing with strings I have to set i to zero?
           // I feel like this is a small issue but for syntax it would be nice to know
           grades = userInput.nextLine(); // user puts grade

           System.out.print("How many hours is class " + i + "?: "); // asks for user hours
           // concatenates class number
           hours = userInput.nextDouble(); // user input
           sumHours = hours + sumHours; // each time we go through the loop this
           //get the gpa by calling the GPA function
           gpa = GPA(grades);
           // line of code adds the hours
           sumGPA = (hours * gpa) + sumGPA; // each time through this calculates GPA      
       }
       double GPA = sumGPA/sumHours; // at the end I want the sumGPA to be divided by the sum of hours
       System.out.printf("Your Semester GPA would be %.2f" , GPA); // print statement that lets user
   }

   //method that takes a string(grade) as parameter and returns the corresponding gpa
   public static double GPA(String grade)
   {
       double gpa = 0.0;
       //run a switch case based on the grade received
       switch(grade)
       {
       case "A+":
           //for grade A+ set gpa = 4.0
           gpa = 4.0;
           break;
       case "A":
           //for grade A set gpa = 4.0
           gpa = 4.0;
           break;
       case "A-":
           //for grade A- set gpa = 3.67
           gpa = 3.67;
           break;
       case "B+":
           //for grade B+ set gpa = 3.37
           gpa = 3.37;
           break;
       case "B":
           //for grade B set gpa = 3
           gpa = 3;
           break;
       case "B-":
           //for grade B- set gpa = 2.67
           gpa = 2.67;
           break;
       case "C+":
           //for grade C+ set gpa = 2.37
           gpa = 2.37;
           break;
       case "C":
           //for grade C set gpa = 2
           gpa = 2;
           break;
       case "C-":
           //for grade C- set gpa = 1.67
           gpa = 1.67;
           break;
       case "D+":
           //for grade D+ set gpa = 1.37
           gpa = 1.37;
           break;
       case "D":
           //for grade D set gpa = 1
           gpa = 1;
           break;
       case "D-":
           //for grade D- set gpa = 0.67
           gpa = .67;
           break;
       case "F":
           //for grade F set gpa = 0
           gpa = 0;
           break;
       }
       return gpa;
   }
}

Output:

Code screenshot: