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

public class Boxes extends JFrame implements ChangeListener {

    private JSlider slider;
    private JPanel panel;

    public static void main(String[] args) {
        Boxes demo = new Boxes();
        demo.setSize(250,150);
        demo.createGUI();
        demo.show();
    }

    private void createGUI() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        Container window = getContentPane();
        window.setLayout(new FlowLayout());

        slider = new JSlider(0, 10, 1);
        window.add(slider);
        slider.addChangeListener(this);

        panel = new JPanel();
        panel.setPreferredSize(new Dimension(180, 50));
        panel.setBackground(Color.white);
        window.add(panel);
    }


    public void stateChanged(ChangeEvent e) {
        Graphics paper = panel.getGraphics();
        int x, numberOfBoxes, counter;
        numberOfBoxes = slider.getValue();
        paper.setColor( Color.white);
        paper.fillRect(0, 0, 180, 50);
        x = 10;
        counter = 1;
        paper.setColor( Color.black);
        while (counter <= numberOfBoxes) {
            paper.drawRect(x, 10, 10, 10);
            x = x + 15;
            counter++;
        }
    }
}