Adding an object that has two separate Strings to an ArrayList in Java

I have done some googling and read through my texts but I can only seem to find how to add a single string to an element of an arrayList i.e. arrayList.add("adding this new string");

as each element is an object, I need to store two strings in each element.
For example I have a txt file with the below already stored:

> Programming in Java: ITC206
> IT Helpdesk: ITC232
> Cyber Ethics: ITC311

When I read the file and add it to an ArrayList it tells me I have 3 elements in the list, one for each line, each line consisting of two strings.

When I try and add a new line in, I can't seem to add two separate strings, one for the course name and one for the course code.

I have tried this manually i.e. arrayList.add("IT", "ITC000"); but it assumes I am trying to specify the element and tells me I can't convert the string ("IT") to an int.

below is the code I have written. all works fine until I hit the subjectList.add to add the new line/element to the list.

 public static void main(String[] args) {
    // create array list        
    ArrayList<String> subjectList = new ArrayList<>();
    Scanner input = new Scanner(System.in); // inport scanner
    
    //read objects from List of Subjects txt file
    try (BufferedReader list = new BufferedReader (new FileReader("ListofSubjects.txt"))) {
        String listLine;
        while ((listLine = list.readLine()) != null) {
            subjectList.add(listLine);
        }
    } catch (IOException e) { // catch any exceptions 
    }
    
    //get new subject name and code 
    System.out.println("Enter the name of your new Subject: ");
    String name = input.nextLine();
    System.out.println("Enter the code for your new Subject: ");
    String code = input.nextLine();
    
    //Subject constructor with two string arg from Subject class
    Subject newSubject = new Subject(name, code);
    
    subjectList.add(newSubject); 
    // I want the element to hold both the name and code
    //like the other lines of the list but get error
    
       
    System.out.println("List Size? " + subjectList.size());
    System.out.println("the list now has: " + subjectList.toString());

}

Maybe I don't need to add these separately, however I need to be able to check the subject name, and the code separately, so figured this would be easier done if they are separate strings in the element.

You can add both attributes seperatly.

subjectList.add(newSubject.getName()); 
subjectList.add(newSubject.getCode());

Or if you need to do it in one call:

list.addAll(Arrays.asList(newSubject.getName(), newSubject.getCode()));

You could also try to create a List only for Subject objects, but when you need to change your approach to add your listLines.

List<Subject> subjectList = new ArrayList<>();
Scanner input = new Scanner(System.in); // inport scanner

//read objects from List of Subjects txt file
try (BufferedReader list = new BufferedReader (new FileReader("ListofSubjects.txt"))) {
    String listLine;
    while ((listLine = list.readLine()) != null) {
        Subject subject = new Subject();
        subject.setName(listLine); // or setCode()
        subjectList.add(subject);
    }
} catch (IOException e) { // catch any exceptions 
}

The issue is that you are trying to mix what your list contains.

For the stuff you read from the file you want the list to hold a single String with all data.

For the new subject you want to add an object of your custom Subject class.

You can't do that ^*. Your list is either a List<String> or a List<Subject>.

My suggestions is to have the more-explicit type (since you already have a Subject class) and use List<Subject>. First you must change the declaration of your subjectList:

ArrayList<Subject> subjectList = new ArrayList<>();

That means you'll need to modify the code that reads from the file to construct Subject objects as well:

try (BufferedReader list = new BufferedReader (new FileReader("ListofSubjects.txt"))) {
    String listLine;
    while ((listLine = list.readLine()) != null) {
        String[] lineParts = listLine.split(":", 2);
        Subject subject = new Subject(lineParts[0].trim(), lineParts[1].trim());
        subjectList.add(subject);
    }
}

This way later on in your code you can be sure that subjectList contains Subject objects only, no matter if you read them from the file or added them later.

^{* actually you can and before generics that was even somewhat common, but it's a terrible idea and among other things generics were introduced to get rid of inter-mixed collections.}