import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class ComboBoxes {
// ------------------------------ FIELDS ------------------------------

    private ActionListener automobilListener = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            Automobil automobil = (Automobil) ((JComboBox) e.getSource()).getSelectedItem();
            if (automobil != null)
                comboBox2.setModel(new DefaultComboBoxModel<>(db.getModelos(automobil.id)));
        }
    };
    private ListCellRenderer automobilRenderer = new DefaultListCellRenderer() {
        @Override
        public Component getListCellRendererComponent(JList<?> list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
            super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
            setText(((Automobil) value).nombre);
            return this;
        }
    };

    private JComboBox<Automobil> comboBox1;
    private JComboBox<String> comboBox2;
    private JPanel contentPane;
    private Db db;

    private JPanel init() {
        db = new Db();

        comboBox1.setModel(new DefaultComboBoxModel<>(db.getAutomobiles()));
        comboBox1.addActionListener(automobilListener);
        comboBox1.setRenderer(automobilRenderer);

        comboBox2.setModel(new DefaultComboBoxModel<>(db.getModelos(1)));

        return contentPane;
    }

    class Automobil {
        int id;
        String nombre;

        Automobil(int id, String nombre) {
            this.id = id;
            this.nombre = nombre;
        }
    }

    class Db {
        Automobil[] CARS = {
                new Automobil(1, "FORD"),
                new Automobil(2, "HONDA"),
                new Automobil(3, "TOYOTA")
        };

        Automobil[] getAutomobiles() {
            return CARS;
        }

        String[] getModelos(int autoId) {
            if (autoId == 1) {
                return new String[]{"TAURUS"};
            } else if (autoId == 2) {
                return new String[]{"ACCORD"};
            } else if (autoId == 3) {
                return new String[]{"PRIUS"};
            } else {
                return new String[0];
            }
        }
    }

// --------------------------- main() method ---------------------------

    public static void main(String[] args) {
        JFrame frame = new JFrame("<class name>");
        frame.setContentPane(new ComboBoxes().init());
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setMinimumSize(new Dimension(400, 200));
        frame.pack();
        frame.setVisible(true);
    }
}