Student schedule

[Jerry Carpenter]

I need help with a program that will end up being a GUI student schedule. In this gui there will be two lists: one for students and another for courses. Clicking on a student will show the courses hes in; clicking on a course will show the students in the course. The students are read in from a text file, and the course are read in from a separate text file. Here is the code I got so far:

/*
 * 
 * 
 */
package schedule;
import java.io.*;
import java.util.Scanner;
import java.util.StringTokenizer; 
 
/**
 *
 * @author 
 */
 

    public class schedule 
    {
       Course[] course = new Course[100];
       int nbCourse = 0;
       Student[] student = new Student[100];
       int nbStudent = 0;
       int studentChoice;
       int courseChoice;
       
       schedule() throws IOException
       {
           Scanner courseFile = 
                   new Scanner(new File("C:\\CS1337Asg4Class.txt"));
           
           while (courseFile.hasNext())
           {
               course[nbCourse++] = new Course(courseFile.nextLine());
           }
           nbCourse--;
           
           
           Scanner studentFile = 
                   new Scanner(new File("C:\\CS1337Asg4Student.txt"));
           while (studentFile.hasNext())
           {
               student[nbStudent++] = new Student(studentFile.nextLine());
           }
           nbStudent--;
           
       }
       
         
      
    
    
    class Course
    {
       String courseCode;
       String title;
       String time;
       
       Course(String line)
       {
             
           StringTokenizer st = new StringTokenizer(line, ",");  
           courseCode = st.nextToken();  
           title = st.nextToken();  
           time = st.nextToken();  
           
       }
        
       
         
    }
    
      class Student
    {
       String id;
       String lastName;
       String firstName;
       String class1;
       String class2;
       String class3;
       String class4;
       String class5;
       
       Student(String line)
       {
             
           StringTokenizer st = new StringTokenizer(line, ",");  
           id = st.nextToken();  
           lastName = st.nextToken();  
           firstName = st.nextToken();
           class1 = st.nextToken();
           class2 = st.nextToken();
           class3 = st.nextToken();
           class4 = st.nextToken();
           class5 = st.nextToken();
           
       }
          
    }
    
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args)throws IOException
    {
        // TODO code application logic here
        new schedule();
    }
 
   }    

Im stumped on how to actually match the student with courses and vice versa.
Here is the info in the files just in case:
Students:
12411,Wegner,Tim,CS1337,ENGL1121,PHYS1211,MATH1304,CHEM1304
12412,Kowalski,Brian,CS1337,ENGL1121,PHYS1211,CHEM1304
12417,Ploski,Karen,CS1337,MATH2306,PHYS1211,ENGL1211,CHEM1304
12423,Selemon,Carol,CS1337,MATH2306,PHYS1211,CHEM1304
12427,Simpson,David,CS4340,MATH2306,PHYS1211,ENGL1211,CHEM1304
12429,Winter,Alyssa,CS1337,ENGL1121,MATH2306,CHEM104,PHYS1211
12432,Millen,Bob,CS2336,ENGL1121,MATH2306,CHEM104,PHYS1211
12436,Holley,Nancy,CS2336,ENGL1121,MATH2306,CHEM104,PHYS1211
12438,Barber,Chris,CS1337,ENGL1121,MATH1304,CHEM104,PHYS1211
12440,Ruiz,Victor,CS2336,ENGL1121,MATH2306,CHEM104,PHYS1211
12441,Jain,Ashok,CS2336,ENGL1121,MATH2306,CHEM104,PHYS1211
12447,Walker,Alan,CS2336,ENGL1121,MATH2306,CHEM104,PHYS1211
12451,Noble,Rich,CS2336,MATH1304,PHYS1211,ENGL1211,CHEM1304
12453,Rich,Joseph,CS1337,MATH2306,PHYS1211,ENGL1211,CHEM1304
12455,Chen,Alan,CS2336,MATH2306,PHYS1211,ENGL1211,CHEM1304

Courses:
CS1337,Computer Science I,MW12:30-1:45
ENGL1211,Rhetoric,MW9:00-10:15
PHYS1211,Basic Physics I,MW10:30-11:45
CHEM1304,Intro to Chemistry I,TTH9:30-10:45
MATH1304,Calculus I,TTH11:00-12:15
MATH2306,Differential Equations I,TTH11:00-12:15
CS4340,Computer Architecture,MW12:30-1:45
CS2336,Computer Science II,MW4:00-5:15

[Rob Spoor]

Some advice:

Use java.util.Lists instead of arrays; what if you get more than 100 students?

Use a List for your courses.

Now, instead of storing just the Course ID in your Student, you can store the Courses themselves (in a List). Since you have a List, you can add and remove Courses as needed.

You'd also like to have an auxiliary method for finding a Course from an array or List based on the ID. Then you first read all the Courses, store them in a List. Next you read all the Students, and for each Course you look up the matching Course object and store that in a List inside the Student.

[Jerry Carpenter]

what do you mean by java.util.Lists. arraylists?
How would I store each course in a list.

[Jerry Carpenter]

This is the way im thinking of how to do it. In the course class, I read the student file again; then I match the courseCode with the courseCode's in the student file. However, I dont understand how to make it reference what students each course was found for. Then I would attempt the same thing in the student class except the other way around.

[Campbell Ritchie]

List<Course> courses = new ArrayList<Course>();

Worth reading the bit in the Java� Tutorials; it tells you about Lists.

And welcome to JavaRanch

[Jerry Carpenter]

I understand whats being said but I cant put it into motion without some visual reference of how to do it.

[Jerry Carpenter]

Can I do this program the way I got it set up?

[Mike Stach]

It looks like a sparse matrix will fit the bill well for this requirement.

[Jerry Carpenter]

Is this going the right direction?

  class Course
    {
       String courseCode;
       String Match;
       ArrayList studentMatch = new ArrayList();
       
       Course(String line) throws IOException
       {
             
           StringTokenizer st = new StringTokenizer(line, ",");
           Scanner studentFile = 
                 new Scanner(new File("C:\\CS1337Asg4Student.txt"));
           while (studentFile.hasNext())
           {
               courseCode = st.nextToken();
               Match = studentFile.nextLine();
               if (Match.contains(courseCode))
                 studentMatch.add(Match);
                
                    
           }
             
          
       }   

[Rob Spoor]

That's one way to do it.

I wouldn't read the entire file over and over again though. Once you've read the students, you can iterate over the Student objects instead.

[Jerry Carpenter]

Hey Rob is there a better way to get the courseCode rather than using a token. Because before I can run the code through all students, the courseCode has already changed.

[Rob Spoor]

Here's how I would do it, in two parts.

1. Create the courses: basically how you initially did it, except you use a List (ArrayList) to store them instead of an array.

2. Create the students + link to course:

Scanner studentFile = new Scanner(new File("C:\\CS1337Asg4Student.txt"));
while (studentFile.hasNext())
{
    String line = studentFile.nextLine();
    StringTokenizer st = new StringTokenizer(line, ",");  
    String id = st.nextToken();  
    String lastName = st.nextToken();  
    String firstName = st.nextToken();
    Student student = new Student(id, lastName, firstName);
    students.add(student);
 
    while (st.hasMoreTokens())
    {
        String courseId = st.nextToken();
        Course course = findCourse(courseId);
        <link course to student>;
    }
}
 
class Student
{
    String id;
    String lastName;
    String firstName;
       
    Student(String id, String lastName, String firstName)
    {
        this.id = id;
        this.lastName = lastName;
        this.firstName = firstName;
    }
}
 
Course findCourse(String id)
{
    for (Iterator i = courses.iterator(); i.hasNext(); )
    {
        Course course = (Course)i.next();
        if (course.id.equals(id))
        {
            return course;
        }
    }
    return null;
}

All that you would need is to implement the linking between students and courses. Give either class a List with references to the other, whichever way you prefer.

With this approach you only go through the student file once.
[ November 04, 2008: Message edited by: Rob Prime ]

[Jerry Carpenter]

so no ArrayList for the student? just for the course? also I see no creation of a Course class do I need one?

[Jerry Carpenter]

wait i think i see what you mean.
ArrayList<Student> students = new ArrayList<Student>();
ArrayList<Course> courses = new ArrayList<Course>();
correct?

[Campbell Ritchie]

But probably better to be less specific in the declarations.

List<Student> studentList = new ArrayList<Student>();

[Rob Spoor]

Originally posted by Jerry Carpenter:
also I see no creation of a Course class do I need one?

You still need it, but it's the same as your original code. I was just lazy again and didn't feel like copying the code

[Jerry Carpenter]

Im sorry I keep bothering you on this.
But where are you telling me to put this code

 Scanner studentFile = new Scanner(new File("C:\\CS1337Asg4Student.txt"));
while (studentFile.hasNext())
{
    String line = studentFile.nextLine();
    StringTokenizer st = new StringTokenizer(line, ",");  
    String id = st.nextToken();  
    String lastName = st.nextToken();  
    String firstName = st.nextToken();
    Student student = new Student(id, lastName, firstName);
    students.add(student);
 
    while (st.hasMoreTokens())
    {
        String courseId = st.nextToken();
        Course course = findCourse(courseId);
        <link course to student>;
    }
}   

and then this code:

 Course findCourse(String id)
{
    for (Iterator i = courses.iterator(); i.hasNext(); )
    {
        Course course = (Course)i.next();
        if (course.id.equals(id))
        {
            return course;
        }
    }
    return null;
}   

Also I see you have references of students and courses. Should those be ArrayList as well to student and course

[Jerry Carpenter]

Here is my new code put together; I dont know if its right or not.

    /*
 * 
 * 
 */
package schedule;
import java.io.*;
import java.util.Scanner;
import java.util.StringTokenizer; 
import java.util.ArrayList;
import java.util.Iterator;
 
/**
 *
 * @author 
 */
 

    public class schedule 
    {
       ArrayList<Course> courses = new ArrayList<Course>();
       ArrayList<Student> students = new ArrayList<Student>();
       
    
       schedule() throws IOException
       {
           Scanner courseFile = 
                   new Scanner(new File("C:\\CS1337Asg4Class.txt"));
           
           while (courseFile.hasNext())
           { 
             String line = courseFile.nextLine();
             StringTokenizer st = new StringTokenizer(line, ",");
             String courseCode = st.nextToken();
             String courseName = st.nextToken();
             String courseTime = st.nextToken();
             Course course = new Course(courseCode,courseName,courseTime);
             courses.add(course);
           }
           
           Scanner studentFile = 
                   new Scanner(new File("C:\\CS1337Asg4Student.txt"));
           
           while (studentFile.hasNext())
           {
               String line = studentFile.nextLine();
               StringTokenizer st = new StringTokenizer(line, ",");  
               String id = st.nextToken();  
               String lastName = st.nextToken();  
               String firstName = st.nextToken();
               Student student = new Student(id, lastName, firstName);
               students.add(student);
 
             while (st.hasMoreTokens())
             {
               String courseId = st.nextToken();
               Course course = findCourse(courseId);
               
             }
           }
            
       }
       
         
    class Student
    {
        String id;
        String lastName;
        String firstName;
       
        Student(String id, String lastName, String firstName)
        {
            this.id = id;
            this.lastName = lastName;
            this.firstName = firstName;
        }
        
    } 
    
       Course findCourse(String id)
       {
           for (Iterator i = courses.iterator(); i.hasNext() :wink: 
           {
               Course course = (Course)i.next();
               if (course.courseCode.equals(id))
               {
                   return course;
               }
           }
                return null;
       }
    
    
    class Course
    {
       String courseCode;
       String courseName;
       String courseTime;
       
       Course(String courseCode, String courseName, String courseTime) 
       {
           this.courseCode = courseCode;
           this.courseName = courseName;
           this.courseTime = courseTime;
           
       }   
       
    }
    
  
    
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args)throws IOException
    {
        // TODO code application logic here
        new schedule();
    }
 
   }

Now the linking process needs to be for both as in, I click on student and it shows their courses; clicking on the course will show the students in the course. So, my question is do I still only have to do the link only once in the student section?

[Rob Spoor]

You only need the link in either. However, storing the information in both will be a lot easier. Course gets a List of Students that follow it and Student gets a List of Courses he/she follows.

Of course you will need to ensure that both Lists are in synch - if a Student drops a Course, that Student also needs to be removed from the Course.

[Jerry Carpenter]

Well all I need it to do is when I click on a student it show his courses. And when clicking on a course it show the students in that specific course. So, I dont need it to add or drop courses. Can this be done with the way its set up. Obviously, Im going to have two separate JList's.

[Rob Spoor]

Sure, no problem. The pseudo code "<link course to student>;" will then add the Student to the List of the Course, and vice versa.

Then when a Student is selected in a List you can simply retrieve its Courses and vice versa.

[Jerry Carpenter]

Ok cool now this part gave me an error (course.id.equals(id)) so I changed it to (course.courseCode.equals(id)) should i have left that alone. Also, can I store the ArrayList students in a JList and the ArrayList courses in a JList as well.

[Rob Spoor]

You have corrected that mistake quite well. Sometimes when I type parts of code I make some mistakes, especially when I can't compile the whole of it.

[Jerry Carpenter]

Im not sure how to create the link, and how it would work. This will work in a gui interface right?

[Jerry Carpenter]

Im still not sure what is meant by placing the student in the list of the course. How would I do that.
Here is what I got for that code

while (st.hasMoreTokens())
             {
               String courseId = st.nextToken();
               Course course = findCourse(courseId);
               if(course.equals(course.courseCode))
               {
                   
               }
                   
             }
           }    

then if it does indeed match I would place that student with the course. I just dont understand how to make it happen. I dont even know if this code is how you get it done. Also, how is this going to work in the gui.

[Jerry Carpenter]

I did a little more and I created another arraylist named sc

if(course.equals(course.courseCode))
               {
                   sc.add(student);
               }    

is this the general idea or not?

[Campbell Ritchie]

How are you going to get "course" equal to "course.courseCode?"

You need to choose a different pair to check equality on.

[Jerry Carpenter]

so would I say course.equal(courseId)

[Campbell Ritchie]

Originally posted by Jerry Carpenter:
so would I say course.equal(courseId)

No.

And the method is called equals not equal. Read about it in the Object class; it takes Object as its parameter, but the two objects would have to be the same type (or very similar types).

[Jerry Carpenter]

Well I still dont understand what is meant by adding the student to the course "<link course to student>;". And how I would be able to represent that in a gui interface. Im sure you fella's are getting tired of my questions by now LOL

[Campbell Ritchie]

Can't remember; it wasn't me who said that!

And what does the equals() method in the Course class do?

[Jerry Carpenter]

Well it reads the courseId from the student and sends it to the findCourse method which iterates through the courses and if it finds a match it returns the course. Now evidently I am supposed to make a link between the two and thats where I am just flat out lost.

[Campbell Ritchie]

And does it find the course? What format is the id in? Is it a primitive? Does course have a method which returns it? When you iterate through your List of courses, can you test for equality between the course id sought and the course id found?

That is the one bit I have noticed. But if you get a bit to work you can put the whole thing together. You can build a large application from small parts, even copying parts over to make up the larger application.

[Jerry Carpenter]

well my code above shows the layout of the program. and it does return a value
and it is an object.

[Jerry Carpenter]

How exactly would I go about giving a class references to the other.
code:

 /*
 * 
 * 
 */
package schedule;
import java.io.*;
import java.util.*;
import javax.swing.*;
 
 
/**
 *
 * @author 
 */
 
 
    public class schedule extends JFrame
    {
       ArrayList<Course> courses = new ArrayList<Course>();
       ArrayList<Student> students = new ArrayList<Student>();
    
       schedule() throws IOException
       {   
 
           
           Scanner courseFile = 
                   new Scanner(new File("C:\\CS1337Asg4Class.txt"));
           
           while (courseFile.hasNext())
           { 
             String line = courseFile.nextLine();
             StringTokenizer st = new StringTokenizer(line, ",");
             String courseCode = st.nextToken();
             String courseName = st.nextToken();
             String courseTime = st.nextToken();
             Course course = new Course(courseCode,courseName,courseTime);
             courses.add(course);
           }
           
           Scanner studentFile = 
                  new Scanner(new File("C:\\CS1337Asg4Student.txt"));
           
           while (studentFile.hasNext())
           {
               
               String line = studentFile.nextLine();
               StringTokenizer st = new StringTokenizer(line, ",");  
               String id = st.nextToken();  
               String lastName = st.nextToken();  
               String firstName = st.nextToken();
               Student student = new Student(id, lastName, firstName);
               students.add(student);
               
             while (st.hasMoreTokens())
             {
               String courseId = st.nextToken();
               Course course = findCourse(courseId);
               course.students.add(student);
               student.courses.add(course);  
               
             }
             
           }
          
       }
       
 
       
       Course findCourse(String id)
       {
           for (Iterator i = courses.iterator(); i.hasNext(); ) 
           {
               Course course = (Course)i.next();
               if (course.courseCode.equals(id))
               {
                   return course;
               }
           }
                return null;
       }
       
          
    class Student
    {
        String id;
        String lastName;
        String firstName;
        ArrayList courses = new ArrayList();
        
        Student(String id, String lastName, String firstName)
        {
            this.id = id;
            this.lastName = lastName;
            this.firstName = firstName;
        }
        
 
    } 
    
 
    class Course
    {
       String courseCode;
       String courseName;
       String courseTime;
       ArrayList students = new ArrayList();
       
       Course(String courseCode, String courseName, String courseTime) 
       {
           this.courseCode = courseCode;
           this.courseName = courseName;
           this.courseTime = courseTime;  
       }   
       
       
    }
    
            
    
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args)throws IOException
    {
        // TODO code application logic here
        new schedule();
    }
 
   }   

[edit]Disable smilies. CR[/edit]
[ November 11, 2008: Message edited by: Campbell Ritchie ]

[Campbell Ritchie]

One way is to implement Student#enrolOnCourse(Course c) and Student#dropCourse(Course c) methods.

You have some very old-fashioned code there; you are better off using a Scanner than StringTokenizer (read this) and you ought to parameterise your Lists.

Instead of

ArrayList courses = new ArrayList();

write

List<Course> courses = new ArrayList<Course>();

Then you can forget all about the class casts.

[Jerry Carpenter]

Great after much headaches for me and probably you guys. I have finally got it all working. I appreciate all the advice, it really helped. This program relied heavily on objects which I was not that familiar with. But after over looking how this thing really works; I am really beginning to understand it.
thanks fellas.

[Campbell Ritchie]

Well done It is good to see somebody learning the concepts.