GradeConverter.java

import java.util.*;

// Provides functionality to convert letter grades to GPA values
public class GradeConverter {
    // Mapping of letter grades to their numeric GPA equivalents
    private static final Map<String, Double> gradeMap = new HashMap<>();
    // Static initializer block to populate grade conversion table
    static {
        gradeMap.put("A1", 4.0);
        gradeMap.put("A2", 3.5);
        gradeMap.put("B1", 3.0);
        gradeMap.put("B2", 2.5);
        gradeMap.put("C1", 2.0);
        gradeMap.put("C2", 1.5);
        gradeMap.put("D1", 1.0);
        gradeMap.put("D2", 0.5);
        gradeMap.put("F3", 0.0);
    }

    // Converts a letter grade to its numeric GPA value
    public static double convert(String grade) {
        if (!gradeMap.containsKey(grade)) {
            throw new IllegalArgumentException("Invalid letter grade: " + grade);
        }
        return gradeMap.get(grade);
    }

    // Checks whether a given grade is a valid letter grade
    public static boolean isValidGrade(String grade) {
        return gradeMap.containsKey(grade);
    }
}