[cbrown08]

I do not quite understand vectors regardless of how many pages I read on them, I have been assigned this program in my java class, I have written the following code so far, some of it was given to me, such as the v.add(cr) in the student class, however I have no clue as to what exactly is in my vector, where it is, and how to pull the variables that I need from it, which is what I ultimately need to do. If someone could please shed some light and point me in the right direction I would appreciate it. I have three classes, gradebook(supplies a gui with 3 buttons, one of which adds a student who has characteristics and up to 5 courses, one button which is supposed to print everything about the students(which is nowhere near done yet, don't worry about that), and one just to exit. Here's my code.

Code:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
 
public class Gradebook extends JFrame 
{
private Button add;
private Button print;
private Button exit;
float[] gpa_array=new float[5];
private int num_students=0;
Student[] stu=new Student[5];
 
public Gradebook()
{
super("Student/Course GUI");
for(int a=0;a<5;a++)
stu[a]=new Student();
ButtonHandler handler = new ButtonHandler();
Container cat = getContentPane();
cat.setLayout(new FlowLayout());
add = new Button("Add Student");
add.addActionListener(handler);
cat.add(add);
print = new Button("Print");
print.addActionListener(handler);
cat.add(print);
exit = new Button("Exit");
exit.addActionListener(handler);
cat.add(exit);
setSize(800,600);
setVisible(true);
}
public class ButtonHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
if(e.getSource()== add)
{
num_students++;
stu[num_students].getData();
}
else
if(e.getSource() == print)
System.out.println("Printing all courses and students");
else
if(e.getSource() == exit)
System.exit(0);
}
}
 
public static void main(String[] args)
{
Gradebook app = new Gradebook();
}
}



import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.Vector;
public class Student
{
private String name;
private String stringage;
private int age;
private float gpa;
private int num_courses;
private String stringnum_courses;
private int totalqp;
private Vector v = new Vector();
    public Student()
    {      
    }
 
public void getData()
{
name = JOptionPane.showInputDialog(null,"Enter Student's Name","Enter Student's Name", JOptionPane.QUESTION_MESSAGE);
stringage = JOptionPane.showInputDialog(null,"Enter Student's Age","Enter Student's Age", JOptionPane.QUESTION_MESSAGE);
age = Integer.parseInt(stringage);
stringnum_courses = JOptionPane.showInputDialog(null,"Enter Number of Courses","Enter Number of Courses", JOptionPane.QUESTION_MESSAGE);
num_courses = Integer.parseInt(stringnum_courses);    
for(int a=0;a<num_courses;a++)
{
Course cr = new Course();
v.add(cr);
}
}
}


import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class Course
{
    // instance variables - replace the example below with your own
    private int id;
    private String dept;
    private int credits;
    private String letter_grade;
    private String stringid;
    private String stringcredits;
    private int QP;
    public Course()
    {
     getDept();
     getId();
     getCredits();
     getLettergrade();
     getQP();
    }
 
    public void getDept()
    {
       dept = JOptionPane.showInputDialog(null,"Enter Department","Enter Department", JOptionPane.QUESTION_MESSAGE); 
}
public void getId()
{
stringid = JOptionPane.showInputDialog(null,"Enter Course ID","Enter Course ID", JOptionPane.QUESTION_MESSAGE); 
id = Integer.parseInt(stringid);
}
public void getCredits()
{
stringcredits = JOptionPane.showInputDialog(null,"Enter Credits","Enter Credits", JOptionPane.QUESTION_MESSAGE); 
credits = Integer.parseInt(stringcredits);
}
public void getLettergrade()
{
letter_grade = JOptionPane.showInputDialog(null,"Enter Letter Grade","Enter Letter Grade", JOptionPane.QUESTION_MESSAGE); 
}
public void getQP()
{
if(letter_grade=="A")
QP=4*credits;
if(letter_grade=="B")
QP=3*credits;
if(letter_grade=="C")
QP=2*credits;
if(letter_grade=="D")
QP=credits;
if(letter_grade=="F")
QP=0;
}
}

Here is the exact assignment just for any clarification purposes:
3 classes
Course
Student
Gradebook(main)

The Main class will have 3 Buttons to control the following Events:

1...Add student to system (initial data--name, gender, and course load (1 to
5 courses))
A Vector in the student class will be initially set to 5 courses for
each of 5 possible students
An array in the Gradebook class will hold references to each of the 5
student objects

2...Print all student data (along with gpa) High to low based upon gpa.

3...Exit