Argthtjtr

cre is currently accumulated credits, multiply by 12 because current credit hours is 12.

req is my equation of minimum credits to hit target CGPA.

cre = data[0][0]*12;

req = (26*data[0][1])-cre;

For next semester, 4 subjects are taken, and the credits hour for each subject is 4,4,3,3.Total up = 14. So I come out with this, what am I trying to do is create a loop and increment x by 0.01 until the total credits of subs meet the req:

if(((56+cre)/26)>data[0][1]) {

        do {



             double x = i/100;



             sub1 = 4*x;

             sub2 = 4*x;

             sub3 = 3*x;

             sub4 = 3*x;



            total = sub1 + sub2 + sub3 + sub4;



                i++;







        } while (total<req);



        System.out.println(sub1/4.0);

        System.out.println(sub2/4.0);

        System.out.println(sub3/3.0);

        System.out.println(sub4/3.0);

        }

Lastly, I try to divide all subs by 4 and 3 to find minimum gpa required for each subjects to hit the target CGPA.

Without more information, we can only guess. Most likely this is the issue:

double x = i/100;

If i is an integer, then this will equal zero for every i less than 100. You probably want floating point division.

double x = i/100.0;

You could find a simpler solution with a little math. First, the equation for calculating GPA is

sum(grade_points_for_all_classes) / total_hours = GPA

The "grade point" for any class is

grade * credit_hours

Now, we want to calc the min grade (min_grade) for all the new classes to reach a new desired_gpa. The equation would be

(sum(grade_points_for_prev_classes) + (min_grade * sum(new_class_hours)) / total_hours = desired_gpa

Where total_hours is the total number of credit hours (new and old classes). Solving for min_grade we get:

min_grade = (desired_gpa * total_hours - sum(grade_points_for_prev_classes)) / sum(new_class_hours)

Example:

public static void main (String args) throws java.lang.Exception

{

    double goalGPA = 3.25;



    // Create an array of previous courses

    double  prevCourses = {

        {4, 4.0},

        {4, 3.0},

        {3, 2.0},

        {2, 1.0}

    };



    // Calc grade points for prev courses

    // and also total credit hours for prev courses

    double gradePointsPrevCourses = 0;

    int totalCreditHours = 0;

    for (double  c : prevCourses) {

        gradePointsPrevCourses += c[0] * c[1];

        totalCreditHours += c[0];

    }



    // Create an array of the new courses

    // Not concerned with grades yet so fill with zero

    double  newCourses = {

        {4, 0.0},

        {4, 0.0},

        {3, 0.0},

        {3, 0.0}

    };



    // Calc new credit hours

    // and add to prev credit hours

    int newCreditHours = 0;

    for (double  c : newCourses) {

        newCreditHours += c[0];

    }

    totalCreditHours += newCreditHours;



    // Solve

    double minGrade = (goalGPA * totalCreditHours - gradePointsPrevCourses) / newCreditHours;

    if (minGrade <= 4.0) {

        System.out.println(String.format("You will need a %.2f in all classes to get a %.2f GPA", minGrade, goalGPA));

    }

    else {

        System.out.println(String.format("Sorry, a %.2f is unobtainable.", goalGPA));

    }

}