55_GradeCalculator.java

// Write a program that will ask the user to enter his/her marks (out of 100). Define a method that will display grades according to the marks entered as below:

// Marks        Grade 
// 91-100         AA 
// 81-90          AB 
// 71-80          BB 
// 61-70          BC 
// 51-60          CD 
// 41-50          DD 
// <=40          Fail 


import java.util.Scanner;

public class GradeCalculator {
  
    // Method to determine grade based on marks
    // Time Complexity: O(1)
    // Space Complexity: O(1)
    public static String getGrade(double marks) {
        
        if (marks >= 91 && marks <= 100) {
            return "AA";
        } else if (marks >= 81 && marks <= 90) {
            return "AB";
        } else if (marks >= 71 && marks <= 80) {
            return "BB";
        } else if (marks >= 61 && marks <= 70) {
            return "BC";
        } else if (marks >= 51 && marks <= 60) {
            return "CD";
        } else if (marks >= 41 && marks <= 50) {
            return "DD";
        } else {
            return "Fail";
        }
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
    
        // Prompt user to enter marks
        System.out.print("Enter your marks (out of 100): ");
        double marks = sc.nextDouble();
        
        // Check if the input marks are within the valid range
        if (marks >= 0 && marks <= 100) {
            // Call the getGrade method to determine the grade
            String grade = getGrade(marks);
            
            // Display the grade
            System.out.println("Your grade is: " + grade);
        } 
        else {
            // Display an error message for invalid input
            System.out.println("Invalid input! Marks should be between 0 and 100.");
        }
            
        sc.close();
    }
}