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Thread: i dont understand whats wrong with my code, please fix it.

  1. #1
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    Default i dont understand whats wrong with my code, please fix it.

    im fairly new to java and this is my first programming assignment, our objective is to implement 3 students grades in two different classes (Student, grades) and find the average.


    Specifications: In the new implementation, the two classes, Student and Grades, we are to implement the following methods:

    Student class:
    public class Student - Defines a student with a full name and a complete set of grades:

    public void setup() - Sets all attributes of the student (name and grades).
    private void setName() - Sets the name of the student.
    private void setGrades() - Sets all the grades for the student.
    public void display() - Displays the complete information on the student.
    public double overallGrade() - Returns the overall grade of the student.

    Grades class:
    public class Grades - Defines a complete set of grades received by a student.

    public void setup() - Sets the complete set of grades
    public void display() - Displays the complete set of grades
    public double average() - Returns the average of the complete set of grades (i.e., it returns a number between 0.0 and 100.0).


    Here is my program:


    public class Program01 {

    public static void main(String[] args)
    {
    Student bob, john, matt;
    Grades grades;

    grades = new Grades();

    double bobgrade, johngrade, mattgrade;

    bob = new Student();
    john = new Student();
    matt = new Student();

    bob.setup();
    john.setup();
    matt.setup();

    bob.display();
    john.display();
    matt.display();

    bobgrade = bob.overallGrade();
    johngrade = john.overallGrade();
    mattgrade = matt.overallGrade();

    grades.average(bobgrade, johngrade, mattgrade);

    System.out.println("The overall grade for the class is: " + grades.theSectionAverage);
    }
    }



    public class Student {
    Grades grades;
    String fullName, firstName, lastName, name;
    int studentProgramGrade, studentExamGrade;

    public void setup(){
    setName();
    setGrades();
    }

    public void setName()
    {

    System.out.print("Please, enter the student's name in the form of Doe, John or Smith, Jane:");
    fullName = Keyboard.readString();

    firstName = fullName.substring(fullName.indexOf(" ") + 1, fullName.length());
    lastName = fullName.substring(0, fullName.indexOf(","));


    name = firstName + " " + lastName;
    }

    public void setGrades()
    {
    studentExamGrade = grades.setupExam(name);
    studentProgramGrade = grades.setupProgram(name);
    }

    public void display()
    {
    System.out.println(name + " " + grades.display());
    }

    public double overallGrade()
    {
    final double PROGRAM_WEIGHT = 0.40;
    final double EXAM_WEIGHT = 1 - PROGRAM_WEIGHT;

    double theOverallGrade;

    theOverallGrade = studentProgramGrade * PROGRAM_WEIGHT + studentExamGrade * EXAM_WEIGHT;

    return theOverallGrade;
    }

    }



    public class Grades {
    int programGrade, examGrade;
    double theSectionAverage;

    public int setupExam(String studentname)
    {
    System.out.print("Please, enter the exam grade for " + studentname + ":");
    examGrade = Keyboard.readInt();

    return examGrade;
    }

    public int setupProgram(String studentname)
    {
    Scanner keyboard = new Scanner(System.in);

    System.out.print("Please, enter the program grade for " + studentname + ":");
    programGrade = Keyboard.readInt();

    return programGrade;
    }

    public String display()
    {
    return programGrade + " " + examGrade;
    }

    public double average(double bobgrade, double johngrade, double mattgrade)
    {
    theSectionAverage = bobgrade + johngrade + mattgrade / 3;

    return theSectionAverage;
    }
    }


    when i run my program=, it gives me the following error:

    Exception in thread "main" java.lang.Error: Unresolved compilation problem:
    Keyboard cannot be resolved

    at Student.setName(Student.java:16)
    at Student.setup(Student.java:8)
    at Program01.main(Program01.java:17)



    any help would be greatly appreciated, like i said, im new to java.


  2. #2
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    Default Re: i dont understand whats wrong with my code, please fix it.

    The compiler is telling you that it doesn't know what the object 'Keyboard' is in the Student.setName() method. Since Keyboard was declared and initialized in the setupProgram() method, that is the limit (or scope) of its visibility to the rest of your classes. Since each class is in its own file (and that's fine) each class that requires a Scanner object may have to create its own.

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