Only scroll to JList cell if required

Question

Hi all.
I have a JList in a JScrollPane. I would like the the selected cell to be visible but the method list.ensureIndexIsVisible(index); doesn't do quite what I want.
The behaviour I would like is that if the cell is already visible don't scroll at all. If the cell isn't visible, scroll so that it is the last cell selected.
The code below demonstrates the problem. With index set to 3, I get the behaviour I want, however, if I set the index to 10, I can't see the selected index.
If I enable the ensureIndexIsVisible method, the selected cell is always shown at the top of the list, or as far towards the top as possible.
thanks..
import javax.swing.*;
public class JListTest extends JFrame {
    public JListTest() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        JList list = new JList(new String[] {"BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla", "BlaBlaBla"});
        JScrollPane scrollPane = new JScrollPane(list);
        add(scrollPane);
        int index = 3;
        list.setSelectedIndex(index);
//        list.ensureIndexIsVisible(index);
        pack();
        setLocationRelativeTo(null);
        setVisible(true);
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new JListTest();
}

Answer 1

I actually thought this was the default behaviour.
If you change your code to:
        int index = 3;
        list.setSelectedIndex(index);
//        list.ensureIndexIsVisible(index);
        pack();
        setLocationRelativeTo(null);
        setVisible(true);
        list.ensureIndexIsVisible(index);then I believe it works the way you want. So I guess the problem is that the components haven't yet been realized when you invoke the method call which is causing the scrolling for some (unknown) reason.
It also works if you wrap the method call in a SwingUtilities.invokeLater().