Separate data and store in ArrayList?

Question

I am trying to separate a set of data. I need to store each data into a variable then create an object and put them in an ArrayList.

The dataset is in this format

lastName, firstName
ID num_courses
course1_name 
grade units
course2_name
grade units
....

I have done this so far but I'm having trouble creating multiple objects, storing the data, and adding it to an ArrayList[]. Thanks for your time and help (:

public static void main (String[] args) throws FileNotFoundException {
Scanner scnr = new Scanner(System.in);
System.out.println("Enter file name: ");
String fileName = scnr.nextLine();
Scanner inFile = new Scanner(new FileInputStream(fileName)); //importing filename

ArrayList<String> list = new ArrayList<String>(); //for list of courses
String name = "";
String id = "";
int coursesTaken = 0;
String courseName = "";
char grade;
int courseUnit = 0;

while(inFile.hasNextLine()){
    name = inFile.nextLine(); //first line is name
    StringTokenizer st = new StringTokenizer(inFile.nextLine()); //separting whitespace
    id = st.nextToken(); //storing ID
    coursesTaken = Integer.parseInt(st.nextToken()); //storing num_courses_taken

    Student s1 = new Student(name, id); //FIXME (need more than 1 student object)

    for(int i = 0; i < coursesTaken*2; ++i){
        courseName = inFile.nextLine();
        s1.addCourses(courseName); //adding to arrayList

        StringTokenizer st2 = new StringTokenizer(inFile.nextLine());
        grade = st2.nextToken().charAt(0);
        courseUnit = Integer.parseInt(st2.nextToken());

        Course ci = new Course(courseName, grade, courseUnit); //FIXME (need more than 1 course)


        }

    }
}

Course.java

public class Course {
    private String name;
    private char grade;
    private int units;


    //constructors
    public Course(){
        name = "";
        grade = 0;
        units = 0;
    }

    public Course(String name, char grade, int units){
        this.name = name;
        this.grade = grade;
        this.units = units;
    }

    //getters 
    public String getName(){
        return name;
    }

    public char getGrade(){
        return grade;
    }

    public int getUnits(){
        return units;
    }

    //setters
    public void setName(String name){
        this.name = name;
    }

    public void setGrade(char grade){
        this.grade = grade;
    }

    public void setUnits(int units){
        this.units = units;
    }  
}

Student.java

public class Student {

    private String name;
    private String id;
    private ArrayList<String> listCourses = new ArrayList<String>();

    //constructor
    //default
    public Student(){
        name = "none";
        id = "none";
        //courses = "none";
    }

    public Student(String name, String id){
        this.name = name;
        this.id = id;
        //this.courses = courses;
    }


    //getters
    public String getName(){
        return name;
    }

    public String getId(){
        return id;
    }

    public ArrayList<String> getCourses(){
        return listCourses;
    }


    //setters
    public void setName(String name){
        this.name = name;
    }

    public void setId (String id){
        this.id = id;
    }

    public void addCourses(String courses){
        listCourses.add(courses);
    }
}

Don't make an `ArrayList[]`. Use the count to determine how many lines to read, not to size your data structure. — Elliott Frisch, Jan 30 '18 at 03:33
Looks like you're missing a `List`... You already have a list of strings, so what's the issue? — OneCricketeer, Jan 30 '18 at 03:34

score 0 · Answer 1 · answered Jan 30 '18 at 03:36

0

//for list of courses

That's a list of strings.

This is for a list of courses

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

Then, just list.add(ci) in the loop

Sidenote: Student.addCourses should be singular, and probably accept a Course object

answered Jan 30 '18 at 03:36

OneCricketeer

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Kirill Simonov · Accepted Answer · 2018-01-30T19:03:37.017

First, you need a List to store your students:

ArrayList<Student> students = new ArrayList<>();

You should add each created student to this list when all fields are parsed:

students.add(s1);

Second, I think, it's better to change the listCourses field from ArrayList<String> to ArrayList<Course> - to store information about all students courses inside the Student object.

Third, you don't need to multiply coursesTaken by 2 because you call inFile.nextLine() twice for each course taken.

for (int i = 0; i < coursesTaken; i++)

Finally your main method would look like this:

private ArrayList<Course> listCourses = new ArrayList<>();

ArrayList<Student> students = new ArrayList<>();

while(inFile.hasNextLine()){
    name = inFile.nextLine(); //first line is name
    StringTokenizer st = new StringTokenizer(inFile.nextLine()); //separting whitespace
    id = st.nextToken(); //storing ID
    coursesTaken = Integer.parseInt(st.nextToken()); //storing num_courses_taken

    Student s1 = new Student(name, id);
    ArrayList<Course> courses = new ArrayList<>();

    for(int i = 0; i < coursesTaken; i++){
        courseName = inFile.nextLine();

        StringTokenizer st2 = new StringTokenizer(inFile.nextLine());
        grade = st2.nextToken().charAt(0);
        courseUnit = Integer.parseInt(st2.nextToken());

        courses.add(new Course(courseName, grade, courseUnit)); //FIXED

    }
    s1.setListCourses(courses);
    students.add(s1); //FIXED

}

UPDATE: Changes in Student class:

public class Student {
    private String name;
    private String id;
    private ArrayList<Course> listCourses = new ArrayList<>();
    ...

    // this is just a setter for listCourses field
    public void setListCourses(ArrayList<Course> listCourses) {
        this.listCourses = listCourses;
    }
}

Hey appreciate your time to help me on my project. Could you please explain what setListCourses() method does? — jCheon, Jan 30 '18 at 18:57
@jCheon `setListCourses()` is a setter for the `listCourses` field in the `Student` class. Check the update in my answer — Kirill Simonov, Jan 30 '18 at 19:04
Got it fixed! all my data seems to be stored and working! Thanks for you help again — jCheon, Jan 30 '18 at 21:02

Separate data and store in ArrayList?

2 Answers2