Question

the program I’m doing requires me to use FileInputStream to calculate the grade point of a course.

The class I created, Course, has a method:

public double getGradePoint ()
{
    if (letterGrade == "A+" || letterGrade == "A")
        gradePoint = 4.0;
    if (letterGrade == "A-")
        gradePoint = 3.7;
    if (letterGrade == "B+")
        gradePoint = 3.3;
    if (letterGrade == "B")
        gradePoint = 3.0;
    if (letterGrade == "B-")
        gradePoint = 2.7;
    if (letterGrade == "C+")
        gradePoint = 2.3;
    if (letterGrade == "C")
        gradePoint = 2.0;
    if (letterGrade == "C-")
        gradePoint = 1.7;
    if (letterGrade == "D+")
        gradePoint = 1.5;
    if (letterGrade == "D")
        gradePoint = 1.0;
    if (letterGrade == "F")
        gradePoint = 0.0;

    return gradePoint;
}

And in the test client I have:

String subject;
String number;
String letGrade;

Course course1 = new Course ("ENGL", "1111", "D+");
FileInputStream file1 = new FileInputStream ("test transcript 1.txt");
Scanner readFile = new Scanner (file1);

while (readFile.hasNext ())
{
    course1.setSubject (readFile.next ());
    subject = course1.getSubject ();
    course1.setNumber (readFile.next ());
    number = course1.getNumber ();
    course1.setLetterGrade (readFile.next ());
    letGrade = course1.getLetterGrade ();
    course1.getGradePoint ();
    System.out.println (course1.toString ());
}

test transcript 1.txt contains:

COMP 1631   A-
ENGL 1101   B
MATH 1200   C+

But for some reason, when i use course1.getGradePoint (), it always returns as 0.0

After running the program:

COMP 1631   A-  (worth = 0.0)
ENGL 1101   B   (worth = 0.0)
MATH 1200   C+  (worth = 0.0)

I’ve tried using course1.getGradePoint () above the while command, like this:

String subject;
String number;
String letGrade;

Course course1 = new Course ("ENGL", "1111", "D+");
course1.getGradePoint ();

FileInputStream file1 = new FileInputStream ("test transcript 1.txt");
Scanner readFile = new Scanner (file1);

while (readFile.hasNext ())
{
    course1.setSubject (readFile.next ());
    subject = course1.getSubject ();
    course1.setNumber (readFile.next ());
    number = course1.getNumber ();
    course1.setLetterGrade (readFile.next ());
    letGrade = course1.getLetterGrade ();
    course1.getGradePoint ();
    System.out.println (course1.toString ());
}

Returns as:

COMP 1631   A-  (worth = 1.5)
ENGL 1101   B   (worth = 1.5)
MATH 1200   C+  (worth = 1.5)

It just won’t work with readFile.next () for some reason. If anyone could help me out, that would be appreciated.

Answer 1

– Objects in Java are compared using equals(), and String is an Object in Java, so it follows the same rule.

– == will be used to compare primitive or to check if two or more Object Reference Variables are pointing to the same Object on the heap or not.

– So you should use equals() or equalsIgnoreCase() (if case doesn’t matters) to compare the String Objects.

Eg:

if (str1.equals(str2)){}