create JList without using collections

Question

I have a problem with my exercise for university. I need to create a JList and put there a few elements (just a simple text) without using any collections nor arrays. It's quite silly because a JList is usually initialized with DefaultListModel (it's a collection too), but in this case I'm not allowed to use it. I tried to put a JLabel object in a parametrized constructor of JList but it doesn't work. Do anyone of you have an idea how to deal with it? Much thanks for help in advance.

My code so far:

JFrame jFrame = new JFrame("title");
JList<String> jList = new JList<>();
jList.add(new JLabel("label1"));
jFrame.add(jList);
jFrame.setSize(500, 500);
jFrame.setVisible(true);

Answer 1

When I correct understand your academic, you simply need to create a list model, which simply returns the constant value or can calculate row value using a formula.

Here is my suggestion for you.

import javax.swing.AbstractListModel;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;

public class SimpleListExample implements Runnable {


    public static void main(String[] args) {
        SwingUtilities.invokeLater(new SimpleListExample());
    }

    @Override
    public void run() {
        JList<String> list = new JList<>(new SimpleListModel());
        JFrame frame = new JFrame("List example");
        frame.add(new JScrollPane(list));
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setSize(350, 200);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    @SuppressWarnings("serial")
    private static class SimpleListModel extends AbstractListModel<String> {

        @Override
        public int getSize() {
            return 20;
        }

        @Override
        public String getElementAt(int index) {
            // Generate constant value with the row index ;)
            return "It's row number: " + (index + 1);
        }
    }
}