How to convert my Arraylist into a readable format when writing to a file Java

Question

I am creating an array list full of students details that needs to be written to a file but when it writes to a file it is unreadable data. such as [javaapplication2.student@15db9742]

private void aList() throws IOException {

        ArrayList<student> enrolledStudents = new ArrayList<student>();

        student James = new student("James", "23 Old Drive", 220298, "Male");
        enrolledStudents.add(James);

        student Matt = new student("Matt", "13 Wee Park", 110502, "Male");
        enrolledStudents.add(Matt);

        student Gary = new student("Gary", "1 Green Close", 240897, "Male");
        enrolledStudents.add(Gary);

        student Charlotte = new student("Charlotte", "5 Park Link", 230402, "Female");
        enrolledStudents.add(Charlotte);

        student Naomi = new student("Naomi", "133 Caulside", 180801, "Female");
        enrolledStudents.add(Naomi);

        student Ryan = new student("Ryan", "88 Wood Burn", 100602, "Male");
        enrolledStudents.add(Ryan);

        student Rhys = new student("Rhys", "42 Newpark", 140306, "Male");
        enrolledStudents.add(Ryan);
        
        System.out.println(enrolledStudents.toString());

        FileWriter writer = new FileWriter("StudentsDetails.txt"); 
        for(student str: enrolledStudents) {
        writer.write(str + System.lineSeparator());
        }
        writer.close();
    }

I have tried adding toString() at the System out to see if it would convert but it doesn't but it still prints jibberish

EDIT:

I have moved it into the student class but now it won't write to a file

    class student {
        private String name;
        private String address;
        private int dob;
        private String gender;

        
        public student(String name, String address, int dob, String gender) throws IOException { // setting Student list order
            this.name = name;
            this.address = address;
            this.dob = dob;
            this.gender = gender;
                
            ArrayList<student> enrolledStudents = new ArrayList<student>();
            student James = new student("James", "23 Old Drive", 220298, "Male");
            enrolledStudents.add(James);
            student Matt = new student("Matt", "13 Wee Park", 110502, "Male");
            enrolledStudents.add(Matt);
            student Gary = new student("Gary", "1 Green Close", 240897, "Male");
            enrolledStudents.add(Gary);
            student Charlotte = new student("Charlotte", "5 Park Link", 230402, "Female");
            enrolledStudents.add(Charlotte);
            student Naomi = new student("Naomi", "133 Caulside", 180801, "Female");
            enrolledStudents.add(Naomi);
            student Ryan = new student("Ryan", "88 Wood Burn", 100602, "Male");
            enrolledStudents.add(Ryan);
            student Rhys = new student("Rhys", "42 Newpark", 140306, "Male");
            enrolledStudents.add(Ryan);

                

            FileWriter writer = new FileWriter("StudentsDetails.txt"); 
            for(student str: enrolledStudents) {
            writer.write(str.toString() + System.lineSeparator());
            }
            writer.close();


                
        }
    }

_Where_ did you add `toString`? What, exactly, did you write in `toString()`? Writing a correct, useful `toString()` method is the right solution, almost certainly. — Louis Wasserman, Apr 15 '21 at 17:35
FileWriter writer = new FileWriter("StudentsDetails.txt"); for(student str: enrolledStudents) { writer.write(str.toString() + System.lineSeparator()); } writer.close(); This is where I assumed it would work. — Matthew Finlay, Apr 15 '21 at 17:39
toString() is what is used by default, you have to implement toString in student (should be Student btw.) — Turo, Apr 15 '21 at 17:39
You need to have a custom `toString()` method inside your `student` (why not `Student` ?) class. — PM 77-1, Apr 15 '21 at 17:40
@MatthewFinlay You haven't written a `toString()` method, all you've done is *call* the *default* `toString()` method. And you havent even really done that, because it was already being called implicitly. You have to actually *write* the `toString()` method ***in the student class***. — Charlie Armstrong, Apr 15 '21 at 17:41
@MatthewFinlay: Nope, that's not what you need to do either. You need to write something like `public class Student { ... @Override public String toString() { /* create a string representing this student. If you use the word FileWriter in this function, you're doing it wrong. */ } }` — Louis Wasserman, Apr 15 '21 at 18:55
@LouisWasserman so the reason it doesn't work is because i'm setting the list order of the class student? — Matthew Finlay, Apr 15 '21 at 19:46
@MatthewFinlay: Nope. Nothing to do with lists. The problem is that `Student` needs to override the `toString()` method. — Louis Wasserman, Apr 15 '21 at 20:58

score 0 · Answer 1 · answered Apr 16 '21 at 03:12

within your student class, you have to override the toString method. Like this:

@Override
public String toString() {
    // here you return what you want to see. In this case I'll print its name
    return name;
}

Also:

it is important to rename your class student to Student. By convention classes names must be in CamelCase.
Don't put logic into the constructor. Your first piece of code is better than your edited code.

How to convert my Arraylist into a readable format when writing to a file Java

1 Answers1