List.java

import java.awt.Component;
import javax.swing.JPanel;

public class List extends JPanel {
    public List() {
        this.setLayout(new javax.swing.BoxLayout(this, javax.swing.BoxLayout.Y_AXIS));
        // Optional: set background color if you want
        // this.setBackground(java.awt.Color.WHITE);
    }

    public void updateNumbers() {
        Component[] listItems = this.getComponents();
        for (int i = 0; i < listItems.length; i++) {
            if (listItems[i] instanceof Task) {
                ((Task) listItems[i]).changeIndex(i + 1);
            }
        }
    }

    public void add(Task task) {
       super.add(task); // ✅ Call JPanel's add method, not your own
}
}