Explain the working of java gpa calculator
This is a program I typed up for a project pertaining to GPA calculation. However, I want to find an alternative to if statements that are NOT conditionals, loops, or arrays. Is there an alternative solution to changing this format?
import java.util.Scanner; public class Part1 { public static void main(String args[]) { String grade = ""; String[] letters = {"A+", "A", "A-", "B+", "B", "B-", "C+", "C", "C-", "D", "F"}; // Creates strings above and the GPA values below double[] grades = {4.33, 4.00, 3.67, 3.33, 3.00, 2.67, 2.33, 2.00, 1.67, 1.00, 0.00}; double credit1; double credit2; double credit3; double credit4; double gradeValue = 0; // Creates 4 credits double totPtsClass1 = 0; double totPtsClass2 = 0; double totPtsClass3 = 0; double totPtsClass4 = 0; double totPts = 0; double totalCredits = 0; double gpa; // Points in classes, GPA System.out.println("Welcome to the UNG GPA Calculator!"); String message; Scanner scan = new Scanner(System.in); System.out.println("Enter your first name: "); message = scan.nextLine(); System.out.println("Enter your last name: "); message = scan.nextLine(); System.out.println("Enter your major: "); message = scan.nextLine(); System.out.println("Enter the number of your first class: "); message = scan.nextLine(); Scanner console = new Scanner(System.in); System.out.println("Please enter the number of credits of the class 1 (A number)"); credit1 = console.nextDouble(); System.out.println("Please enter your grades for the class 1(Capital letters such as A,B+, C-)"); grade = console.next(); if (grade.equals("A")) gradeValue = 4.00; else if (grade.equals("A-")) gradeValue = 3.67; else if (grade.equals("B+")) gradeValue = 3.33; else if (grade.equals("B")) gradeValue = 3.00; else if (grade.equals("B-")) gradeValue = 2.67; else if (grade.equals("C+")) gradeValue = 2.33; else if (grade.equals("C")) gradeValue = 2.00; else if (grade.equals("D+")) gradeValue = 1.33; else if (grade.equals("D")) gradeValue = 1.00; else if (grade.equals("F")) gradeValue = 0; else if (grade.equals("FX")) gradeValue = 0; else System.out.println("Invalid Grade"); totPtsClass1 = gradeValue * credit1; System.out.println("Please enter the number of credits of the class 2 (A number)"); credit2 = console.nextDouble(); System.out.println("Please enter your grades for the class 2 (Capital letters such as A,B+, C-)"); grade = console.next(); if (grade.equals("A")) gradeValue = 4.00; else if (grade.equals("A-")) gradeValue = 3.67; else if (grade.equals("B+")) gradeValue = 3.33; else if (grade.equals("B")) gradeValue = 3.00; else if (grade.equals("B-")) gradeValue = 2.67; else if (grade.equals("C+")) gradeValue = 2.33; else if (grade.equals("C")) gradeValue = 2.00; else if (grade.equals("D+")) gradeValue = 1.33; else if (grade.equals("D")) gradeValue = 1.00; else if (grade.equals("F")) gradeValue = 0; else if (grade.equals("FX")) gradeValue = 0; else System.out.println("Invalid Grade"); totPtsClass2 = gradeValue * credit2; System.out.println("Please enter the number of credits of the class 3 (A number)"); credit3 = console.nextDouble(); System.out.println("Please enter your grades for the class 3 (Capital letters such as A,B+, C-)"); grade = console.next(); if (grade.equals("A")) gradeValue = 4.00; else if (grade.equals("A-")) gradeValue = 3.67; else if (grade.equals("B+")) gradeValue = 3.33; else if (grade.equals("B")) gradeValue = 3.00; else if (grade.equals("B-")) gradeValue = 2.67; else if (grade.equals("C+")) gradeValue = 2.33; else if (grade.equals("C")) gradeValue = 2.00; else if (grade.equals("D+")) gradeValue = 1.33; else if (grade.equals("D")) gradeValue = 1.00; else if (grade.equals("F")) gradeValue = 0; else if (grade.equals("FX")) gradeValue = 0; else System.out.println("Invalid Grade"); totPtsClass3 = gradeValue * credit3; System.out.println("Please enter the number of credits of the class 4 (A number)"); credit4 = console.nextDouble(); System.out.println("Please enter your grades for the class 4 (Capital letters such as A,B+, C-)"); grade = console.next(); if (grade.equals("A")) gradeValue = 4.00; else if (grade.equals("A-")) gradeValue = 3.67; else if (grade.equals("B+")) gradeValue = 3.33; else if (grade.equals("B")) gradeValue = 3.00; else if (grade.equals("B-")) gradeValue = 2.67; else if (grade.equals("C+")) gradeValue = 2.33; else if (grade.equals("C")) gradeValue = 2.00; else if (grade.equals("D+")) gradeValue = 1.33; else if (grade.equals("D")) gradeValue = 1.00; else if (grade.equals("F")) gradeValue = 0; else if (grade.equals("FX")) gradeValue = 0; else System.out.println("Invalid Grade"); totPtsClass4 = gradeValue * credit4; totPts = totPtsClass1 + totPtsClass2 + totPtsClass3 + totPtsClass4; totalCredits = credit1 + credit2 + credit3 + credit4; gpa = totPts / totalCredits; System.out.printf("Your GPA is: %.2fn", +gpa); } }I would like a solution other than the three above, but I'm unfamiliar with anything to substitute for all those if then statements.
Regarding the JAVA GPA calculator, put the Grade-Score mapping in a HashMap and read it from there.
Do this once:
Map gradeToScore = new HashMap<>(); gradeToScore.put("A", 4.00); gradeToScore.put("A-", 3.67); gradeToScore.put("B+", 3.33); gradeToScore.put("B", 3.00); gradeToScore.put("B-", 2.67); gradeToScore.put("C+", 2.33); gradeToScore.put("C", 2.00); gradeToScore.put("D+", 1.33); gradeToScore.put("D", 1.00); gradeToScore.put("F", 0.0); gradeToScore.put("FX", 0.0);
Then you can use it as many times as needed:
if(gradeToScore.containsKey(grade)) { gradeValue = gradeToScore.get(grade); }else{ System.out.println("Invalid Grade"); }
If you want to go several steps further in optimizing things for readability, you can get to something like this:
public class GradeCalculator { //MAIN public static void main(String args[]) { GradeCalculator calc = new GradeCalculator(); calc.startInteraction(); } //DATA CLASS private static class Student{ public String firstName; public String lastName; public String major; public String numFirstClass; public final List credits = new ArrayList<>(); public final List points = new ArrayList<>(); } //PROPERTIES & CONSTRUCTOR private final Map gradeToScore = new HashMap<>(); public GradeCalculator() { gradeToScore.put("A+", 4.33); gradeToScore.put("A", 4.00); gradeToScore.put("A-", 3.67); gradeToScore.put("B+", 3.33); gradeToScore.put("B", 3.00); gradeToScore.put("B-", 2.67); gradeToScore.put("C+", 2.33); gradeToScore.put("C", 2.00); gradeToScore.put("C-", 1.67); gradeToScore.put("D+", 1.33); gradeToScore.put("D", 1.00); gradeToScore.put("F", 0.0); gradeToScore.put("FX", 0.0); } //PUBLIC public void startInteraction() { System.out.println("Welcome to the UNG GPA Calculator!"); try(Scanner scan = new Scanner(System.in);){ Student student = new Student(); loadStudentInfo(student, scan); loadCreditsAndPoints(student, scan, 1); loadCreditsAndPoints(student, scan, 2); loadCreditsAndPoints(student, scan, 3); loadCreditsAndPoints(student, scan, 4); double gpa = calculateGpa(student); System.out.printf("Your GPA is: %.2f
", +gpa); } } //PRIVATE private void loadStudentInfo(Student student, Scanner scan) { System.out.println("Enter your first name: "); student.firstName = scan.nextLine(); System.out.println("Enter your last name: "); student.lastName = scan.nextLine(); System.out.println("Enter your major: "); student.major = scan.nextLine(); System.out.println("Enter the number of your first class: "); student.numFirstClass = scan.nextLine(); } private void loadCreditsAndPoints(Student student, Scanner scan, int classNumber) { System.out.println("Please enter the number of credits of the class " + classNumber + " (A number)"); double credit = scan.nextDouble(); student.credits.add( credit ); System.out.println("Please enter your grades for the class " + classNumber + " (Capital letters such as A,B+, C-)"); String grade = scan.nextLine(); double gradeValue = 0; if(gradeToScore.containsKey(grade)) { gradeValue = gradeToScore.get(grade); }else{ System.out.println("Invalid Grade"); } double classTotPts = gradeValue * credit; student.points.add(classTotPts); } private double calculateGpa(Student student) { double totalCredits = getTotal(student.credits); double totPts = getTotal(student.points); double gpa = totPts / totalCredits; return gpa; } private double getTotal(List doubles) { double total = 0; for(Double d:doubles) { total += d; } return total; } }And, I would prefer to stay away from streams and lambdas till you completely nail down core Java.