Plotting Graphs using Java Graphics Library [Dice Throw Example] [Swing]

This program throws five dice and the sum of the numbers is plotted. The event of throwing the dice is triggered by a button pressed by the user.

Source:

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

class Die {

    Random rand = new Random();

    int getCount() {
        return rand.nextInt(6) + 1;
    }
}

public class DiceThrower extends JFrame {

    class MyPanel extends JPanel {

        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.BLUE);

            int height = (getHeight());
            Integer previous = null;

            if (points.size() >= 1) {
                previous = height - points.get(0)*(getHeight())/30;
            } else {
                return;
            }

            int[] x1 = new int[points.size()];
            int hstep = getWidth() / points.size();
            
            for (int i = 0; i < x1.length; ++i) {
                x1[i] = i * hstep;
            }

            int c = 0;
            int skip = 1;
            for (int p : points) {
                if(skip==1){ skip = 0; continue; }
                g.drawLine(x1[c], previous, x1[c] + hstep, height - p*(getHeight()/30));
                previous = height - p*(getHeight()/30);
                ++c;
            }
        }
    }

    Die[] dice = new Die[5];

    int sum = 0;
    ArrayList<Integer> points = new ArrayList<>();
    MyPanel graph = new MyPanel();

    JButton throwB = new JButton("Throw Dice!");

    {
        throwB.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                int prev = sum;
                updateSum();
                ((JButton) e.getSource()).setText("Previous : " + prev + " Current : " + sum + ". Throw Again!");
                graph.repaint();
            }

        });
    }

    void updateSum() {
        sum = 0;
        for (int i = 0; i < dice.length; ++i) {
            sum += dice[i].getCount();
        } 
        points.add(sum); 
        System.out.println(sum);
    }

    DiceThrower() {
        setTitle("5 Dice Throws Sum Plotter -__-");
        for (int i = 0; i < dice.length; ++i) {
            dice[i] = new Die();
        }
        add(graph);
        add(BorderLayout.SOUTH, throwB);
        setSize(500, 500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
    }

    public static void main(String[] args) {
        try {
            for (UIManager.LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (Exception e) {
            // If Nimbus is not available, you can set the GUI to another look and feel.
        }
        new DiceThrower();
    }
}