[hardwired]

Code:

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.Random;
import javax.swing.*;

public class HiBars implements Runnable {
    HiBarPanel hiBarPanel = new HiBarPanel();
    Random seed = new Random();
    int DATA_MAX = 100;
    long delay = 20*1000;

    public HiBars() {
        Thread thread = new Thread(this);
        thread.setPriority(Thread.NORM_PRIORITY);
        thread.start();
    }

    public void run() {
        while(true) {
            hiBarPanel.setData(getData(), DATA_MAX);
            try {
                Thread.sleep(delay);
            } catch(InterruptedException e) {
                break;
            }
        }
    }

    private int[] getData() {
        int[] data = new int[4];
        for(int i = 0; i < data.length; i++) {
            data[i] = seed.nextInt(DATA_MAX+1);
        }
        return data;
    }

    private JPanel getContent() {
        return hiBarPanel;
    }

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new HiBars().getContent());
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}

class HiBarPanel extends JPanel {
    int[] data;
    int maxValue = 10;
    final int PAD = 20;

    public void setData(int[] data, int maxValue) {
        this.data = data;
        this.maxValue = maxValue;
        System.out.printf("data = %s%n", java.util.Arrays.toString(data));
        repaint();
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        // Draw ordinate.
        g2.draw(new Line2D.Double(PAD, PAD, PAD, h-PAD));
        // Draw abcissa.
        g2.draw(new Line2D.Double(PAD, h-PAD, w-PAD, h-PAD));
        double xInc = (double)(w - 2*PAD)/data.length;
        double scale = (double)(h - 2*PAD)/maxValue;
        Path2D.Double path = new Path2D.Double();
        // Draw data.
        double x = PAD;
        double y = h - PAD;
        path.moveTo(x, y);
        for(int i = 0; i < data.length; i++) {
            x = PAD + i*xInc;
            y = h - PAD - scale*data[i];
            path.lineTo(x, y);
            path.lineTo(x+xInc, y);
        }
        path.lineTo(x+xInc, h-PAD);
        g2.setPaint(new Color(220,220,210));
        g2.fill(path);
        g2.setPaint(Color.blue);
        g2.draw(path);
    }
}