Adding file messes up Inheritance classes

[Cody Biggs]

So I'm finishing up another program, but again I have run into a problem. I'm trying to load in a file of students with the format firstname,lastname,major. A few of my classes are inheritance classes, so when I add the file it forces me to add a string to those class constructors which I don't want to do. How do I get around this?

The class where I'm loading the students.

import java.io.File;
import java.util.ArrayList;
import java.util.Scanner;


public class College
{
	private static College instance;
	
	 ArrayList<Student> students = new ArrayList<Student>();
	 ArrayList<Instructor> instructors = new ArrayList<Instructor>();
	
	
	private College(){
		
	}
	
	public static College getInstance()
	{
		if(instance == null)
			instance = new College();
		{
		System.out.println("College class object created!");
		}
		return instance;
	}
	
	public static void main(String[] args)
	  {
	
		College x = College.getInstance();
		College y = College.getInstance();
		
		if (x == y)

			System.out.println("Same object");

			else

			System.out.println("Different object");

		}// end main
	
		public ArrayList<Student> getStudentList()
		{
			return students;
		}

		public ArrayList<Instructor> getInstructorList()
		{
			return instructors;
		}
	
		public  Student addStudent(String firstName, String lastName)
		{
			Student student;
			student = new Student(firstName, lastName);
			students.add(student);
			
			return student;
		}
	
		public  Instructor addInstructor(String firstName, String lastName)
		{
			Instructor instructor;
			instructor = new Instructor(firstName, lastName);
			instructors.add(instructor);
			
			return instructor;
			
		}
	
		public void getStudentById()
		{
			
		}
		
		public Student getStudentByName(String firstName, String lastName)
		{
			for(int i =0; i < students.size(); i++)
			{
				Student s;
				s = students.get(i);
				
				if(s.().equals(firstName, lastName))
					return s;
				
			}
			
		}
		
		public void getInstructor(String firstName, String lastName)
		{
			
		}
		
		
		
		public void LoadStudents(String studentFile)
		{
			Scanner input = new Scanner( new File (studentFile));
			while(input.hasNextLine())
			{
				String line = input.nextLine();
				String[] studentNames = line.split(",");
				
				Student student = new Student(studentNames[0], studentNames[1], studentNames[2]);
				students.add(student);
			}
			input.close();
	}// end LoadStudents
		}
		
		
		
		
}// end College Class

PersonClass I'm completing after I load students

public class Person 
{

	private String firstName;
	private String lastName;
	private String majorStudent;
	
	public Person(String fName, String lName //LoadStudents makes me put an extra string here)
	{
		firstName = fName;
		lastName = lName;
	}
	
	
	public String getFirstName()
	{
		return firstName;
	}
	
	
	public String getLastName()
	{
		return lastName;
	}

Student Class. Same thing makes me add another String to constructor because of the inheritance

public class Student extends Person
{
	static private int nextID = 2454;
	final int studentId;
	private Major major;
	public Student(String fName, String lName)
	{
		super(fName,lName);
		studentId = nextID;
		nextID++;
	}
	
	public int getStudentId()
	{
		return studentId;
	}
	
	public void setMajor(String majorName)
	{
		Catalog cat = Catalog.getCatalog();
		major = cat.getMajorByName(majorName);
	}
	
	
	
	
	
	
}

Catalog Class

import java.util.ArrayList;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Scanner;

public class Catalog
{
	private static Catalog instance;
	
	static ArrayList<Course> courses = new ArrayList<Course>();
	ArrayList<Major> majors = new ArrayList<Major>();
	final String coursebyId = " ";
	
	private Catalog()
	{
		
	}
	
	public static Catalog getInstance()
	{
		if(instance == null)
			instance= new Catalog();
		{
		System.out.println("Catalog class object created!");
		}
		return instance;
	}
	
	public static void main(String[] args)
	  {
	
		Catalog x = Catalog.getInstance();
		Catalog y = Catalog.getInstance();
		
		if (x == y)

			System.out.println("Same object");

			else

			System.out.println("Different object");

		}// end main
	
	
	
	public ArrayList<Course> getCourseList()
	{
		for(int i =0; i < courses.size(); i++)
		{
			System.out.print(courses.get(i));
		}
		return courses;
	}
	
	
	public ArrayList<Major> getMajorList()
	{
		for(int i =0; i < majors.size(); i++)
		{
			System.out.print(majors.get(i));
		}
		
		return majors;
	}
	
	public String getCourseById()
	{
		return coursebyId;
	}
	
	public void LoadMajors(String majorsFile) throws FileNotFoundException
	{
		
		Scanner input = new Scanner(new File (majorsFile));
		while(input.hasNextLine())
		{
			String line = input.nextLine();
			String[] classMajors = line.split(",");
			boolean isDegreeSeeking = false;
			
			Major major = new Major(classMajors[0], isDegreeSeeking = Boolean.parseBoolean(classMajors[1]));
		}
		input.close();
	}// end load majors

	public void LoadCourses(String courseFile) throws FileNotFoundException
	{
		
		Scanner input = new Scanner(new File(courseFile));
		while(input.hasNextLine())
		{
			String line = input.nextLine();
			String[] classCourses = line.split(",");
			
			Course course = new Course(classCourses[0],classCourses[1], Integer.parseInt(classCourses[2]));
			courses.add(course);
		}
		input.close();
	}


	public static Catalog getCatalog() {
		
		
		return null;
	}


	public Major getMajorByName(String majorName) {
		
		for(int i =0; i < majors.size(); i++)
		{
			Major m;
			m = majors.get(i);
			
			if (m.getName().equals(majorName))
				return m;
			
		}

		
		return null;
	}
		
	
}// end class

and major class

import java.util.ArrayList;
public class Major 
{
	final String name;
	final boolean isDegree;
	ArrayList<String> requiredCourses = new ArrayList<String>();
	
	public Major(String majorName, boolean degree)
	{
		name = majorName;
		isDegree = degree;
	}
	
	public String getName()
	{
		return name;
	}
	
	public boolean getIsDegree()
	{
		return isDegree;
	}
	
	
	public void addRequiredCourse()
	{
		
	}
	
	
	public ArrayList <String> getRequiredCourse()
	{
		return requiredCourses;
	}
	
	
	
	
	
}

[Fred Kleinschmidt]

Class Student should have a constructor that takes 3 Strings, and it should invoke its superclass 2-string constructor and save the major. It might also have a 2-string ctor:

public class Student extends Person {

     private String major;

     public Student( String fName, String lName, String major ) {
         super( fName, lName );
          this.major = major;
          ...
     }

     public Student( String fName, String lName ) {
         this( fName, lName,"Undeclared");
     }
}    

[Liutauras Vilda]

Welcome to the Ranch, Cody

Try not to post such an amount of code especially when you're trying to solve an issue which appears in a known for you area of code.
Fred already pointed out what causes a problem. However, since you posted all that code, I thought I'll give some comments on it, so you could consider improving it.

1. As an example refering to this your code snippet:

public Major getMajorByName(String majorName) {
         
        for(int i =0; i < majors.size(); i++)
        {
            Major m;
            m = majors.get(i);
             
            if (m.getName().equals(majorName))
                return m;
             
        }
 
         
        return null;
    }

Do you know about the enhanced-for loop? It is very handy for iterating over collection of items. Example:

public Major getMajorByName(String majorName) {
    for (Major m : majors) {
        if (m.getName().equals...) {
            return
        }
    }
}

2.

public void setMajor(String majorName)
{
    Catalog cat = Catalog.getCatalog();
    major = cat.getMajorByName(majorName);
}

This code snippet lets to set major to null, think how to not let that. How that happens? In case to this method majorName is passed a non existing name, method getMajorByName() would return null. Consider before you setting major if returned value is null - in case it is, let user know (throw an exception), that such major doesn't exist in majors list and can't be set as such.

3. Line 98 in Catalog class has the line:

Course course = new Course(classCourses[0],classCourses[1], Integer.parseInt(classCourses[2]))

this line can cause you problems too. Before you parse, check if the next token can be parsed to an integer, in case not, let user know about it, that the courseFile has been passed contains invalid data, so cannot be read and is needed other. Read about the Scanner class method hasNextInt()

4. Some instance variables aren't private - make them as such. Refering to Major class.

5. While being an explicit is a sign of good code readability, in the code part like this I think it is a bit too much (others might think differently):

public  Student addStudent(String firstName, String lastName)
{
    Student student;
    student = new Student(firstName, lastName);
    students.add(student);
             
    return student;
}

Think if you want to change it to:

public  void addStudent(String firstName, String lastName)
{
    students.add(new Student(firstName, lastName));
}

Did you notice what I did? It is related with the second issue of that method. This method name suggests that it should add a Student, but it appears in your case it creates/adds and returns. That is not good most likely. If the method says addSomething it should add and nothing else - ok, it might could return true or false in success or failure, but definitely not return a Student. So I'd keep such method as void (with no return type). In case you need to get student, create another method. One method needs to do one thing (similar issues in similar cases in other classes).

6. Something not quite correct with the line 85 [College class]:

if(s.().equals(firstName, lastName))

7. Some of the methods starts with an Upper case while they shouldn't: methodName; variableName; ClassName; CONSTANT_NAME.

That is it for now.