Convert String to Double?

Question

This is a two part code with a tester class. For some reason I can't figure out how to convert this string variable to code correctly involved in the equation gradeNum = grad - .3 and gradeNum = grade + 0.3. Any ideas?

/** This is my class Grade */
    public class Grade
{

    private String grade;
    private double gradeNum;


// Constructor
public Grade(String showGrade)
{
    grade = showGrade;
    gradeNum = 0;
}


// getNumericGrade method to return grade number
public double getNumericGrade()
{
    if (grade.equalsIgnoreCase("A") || grade.equalsIgnoreCase("A+"))
{
    gradeNum = 4.0;
}
    else if (grade.equalsIgnoreCase("A-"))
{
    gradeNum = 3.7;
}


    if (grade.equalsIgnoreCase("B"))
{
    gradeNum = 3.0;
}
    else if (grade.equalsIgnoreCase("B+"))
{
    gradeNum = 3.3;
}
    else if (grade.equalsIgnoreCase("B-"))
{
    gradeNum = 2.7;
}


    if (grade.equalsIgnoreCase("C"))
{
    gradeNum = 2.0;
}
    else if (grade.equalsIgnoreCase("C+"))
{
    gradeNum = 2.3;
}
    else if (grade.equalsIgnoreCase("C-"))
{
    gradeNum = 1.7;
}


    if (grade.equalsIgnoreCase("D"))
{
    gradeNum = 1.0;
}
    else if (grade.equalsIgnoreCase("D+"))
{
    gradeNum = 1.3;
}
    else if (grade.equalsIgnoreCase("D-"))
{
    gradeNum = .7;
}

    if (grade.equalsIgnoreCase("F"))
{
    gradeNum = 0.0;
}

    return gradeNum;


    System.out.println("Invalid letter grade");
    return -1.0;


}
}


/** This is my class tester
 */

import java. util .Scanner;

/**
This program tests the numeric grade with a given letter grade.
*/
public class GradeTester 
{
public static void main(String[] args)
{
    Scanner in = new Scanner(System.in);

    System.out.println("Enter a letter grade: ");
    String showGrade = in.nextLine();

    Grade gg = new Grade(showGrade);

    System.out.print("Numeric Value: ");
    System.out.println(gg.getNumericGrade());

    in.close();

}
}

Answer 1

David's & Ken's answers are correct. You need to implement them both and then additionally remove some return statements, then the code will work as expected. Here's an example:

    if (Character.toUpperCase(grade.charAt(0)) == 'B')
        gradeNum = 3.0;
    if (grade.length() > 1 && Character.toUpperCase(grade.charAt(1)) == '-')
        gradeNum = gradeNum - 0.3;
    return gradeNum;

Earlier, since you're checking with grade.equalsIgnoreCase("B") , it would've never matched for an input as "B-". So, gradeNum would never have the value as 3.0 . It would still be 0.0 and then perform gradeNum = gradeNum - 0.3; which results in -0.3 .

Also, you could use a switch case instead of so many if statements. It'll be more elegant/readable & efficient.

Answer 2

Instead of if (grade.equalsIgnoreCase("B")) etc, use:

if (Character.toUpperCase(grade.charAt(0)) == 'B')

And instead of grade.equalsIgnoreCase("A-") etc, use:

if (grade.length() > 1 && grade.charAt(1) == '-')

This should be enough to enable you to fix your problem.

NOTE : There are other changes that need to be made, but I don't want to just spoon-feed you the correct code.