why isnt this scroll panel scrolling?

heres my class file. All I am trying to do is get the scroll panel to
have a scroll bar and the ability to scroll.

Why does changing the size of the JScrollPane have no affect on it when
I run the program? What do I have to do to gain scrolling
capabilities?

Thanks

package orthopedicnotegenerator;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.font.*;
import java.text.Collator;
import javax.swing.event.*;
import java.util.Date;
import java.text.DateFormat;

class ExamKnee2 extends JDialog{

    final int WIDTH = 830;

    AccessConnection dataConnection = new AccessConnection();

    JPanel pane;
    JScrollPane scroller;

    public ExamKnee2() {

        setModal(true);
        Container pane = this.getContentPane();
        this.setAlwaysOnTop(true);
        pane.setLayout(new BorderLayout());
        //pane.setLayout(null);

        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        setBounds(300,0,WIDTH,400);

        addWidgets();

        setVisible(true);
        validate();

    }

    public void addWidgets(){

        pane = new JPanel();
        pane.setLayout(new BorderLayout());

        JButton button = new JButton("Button 1 (PAGE_START)");
        pane.add(button, BorderLayout.PAGE_START);

        button = new JButton("Button 2 (CENTER)");
        button.setPreferredSize(new Dimension(200, 100));
        pane.add(button, BorderLayout.CENTER);

        button = new JButton("Button 3 (LINE_START)");
        pane.add(button, BorderLayout.LINE_START);

        button = new JButton("Long-Named Button 4 (PAGE_END)");
        pane.add(button, BorderLayout.PAGE_END);

        button = new JButton("5 (LINE_END)");
        pane.add(button, BorderLayout.LINE_END);

        scroller = new JScrollPane(pane);
        scroller.setSize(200,200);
        add(scroller, BorderLayout.CENTER);

    }

    public static void main(String args[]){
        ExamKnee2 examKnee = new ExamKnee2("Right", "123-45-6789", "2
weeks");
    }
}