Help with this program do not understand why it doesnt work

[baden]

Hi, I don't know why the final output does not work right. It does not display anything and I don't know why.


import javax.swing.*;
public class lab5 {


public static void main(String [] args){
String finalGrade;
String grade="";
String display = "";
String course="";
int GPA=0;
double finalCalc;
int confirm;
double avg=0;

do{
courses();

enterGrade(grade);

display += " "+course+ " " + grade;
confirm=JOptionPane.showConfirmDialog(null,"Do you have another course?", "More?", JOptionPane.YES_NO_OPTION);
}
while(confirm==JOptionPane.YES_OPTION);
gradeList(display, grade, GPA, course, avg);

}



public static String courses ()
{
String course;

course=JOptionPane.showInputDialog("Enter course taken(IT101, IT103, IT108, IT212, IT214, IT224, IT341)");

return course;
}


public static String enterGrade(String course)
{
String grade;

grade=JOptionPane.showInputDialog("Enter grade for: " + course + " (ex. A+, A, A-)");

return grade;
}


public static int finalGPA(String grade)
{
int GPA;
if (( grade=="A+") || (grade=="A") || (grade=="A-"))
{
GPA=4;
}
else if (( grade=="B+") || (grade=="B") || (grade=="B-"))
{
GPA=3;
}
else if (( grade=="C+") || (grade=="C") || (grade=="C-"))
{
GPA=2;
}
else if (( grade=="D+") || (grade=="D") || (grade=="D-"))
{
GPA=1;
}
else
GPA=0;
return GPA;
}


public static double calc(int GPA, int i)
{
double avg=GPA/i;
return avg;
}


public static void gradeList(String output, String grade, int GPA, String course, double avg)
{

output += "Course Grade\n" + course + grade + "\n\n ---------------------\n" + avg;
JOptionPane.showMessageDialog(null, output);
}
}

[Ganon11]

One mistake I notice:

Your method, courses(), is returning a String object. Inside the method, you are creating and returning this just fine; but where you call it (in main(), the first line of your do...while loop) you don't have a String object receiving it. Should you be setting course equal to the result:

course = courses();

[baden]

One mistake I notice:

Your method, courses(), is returning a String object. Inside the method, you are creating and returning this just fine; but where you call it (in main(), the first line of your do...while loop) you don't have a String object receiving it. Should you be setting course equal to the result:

course = courses();

Okay i fixed that everything works like i want but it is not calcuating the final gpa. Basically the last line in the output should calculate the avarage of the grades after they have been converted from string to an integer

[Ganon11]

A few more mistakes I found:

1) Your enterGrade() method was also String returning, but you were not doing anything with the result, just like the courses() method.

2) In your finalGPA function, you are using == with Strings - you should be using the .equals() method, like:

grade.equals("A+"); // not grade == "A+"

3) You have defined the functions finalGPA and calc, but I don't see you use them anywhere in your code...is this a problem?