Add the ability to draw continuously while dragging; Add the ability to change the size of new dots by scrolling the mouse wheel up/down; Add animation using a Timer so that the dots all move when drawn.

Add an array for the colors of each dot, make each color random (for fun, use four ints from 0-255 instead of three, to give dots transparency), make each dot move at a different random speed (in x and y directions), and have the dots "bounce" appropriately off all four sides of the screen.

Add the ability to "group" dots whenever the mouse is dragged (hint: when pressed, remember that dot's speed x/y, then whenever dragging, use that speed x/y for all the 'dragged' dots...).

Add a 10 point slider that will act as a speed multiplier. So when you adjust the slider the current stored speed for the dot will increase by a factor of the current position of the slider.

Have the left click do one thing (e.g. "bubbles") and the right mouse click do another ("group").

Dots.java

import javax.swing.JFrame;

public class Dots {

// -----------------------------------------------------------------

// Creates and displays the application frame.

// -----------------------------------------------------------------

public static void main(String[] args) {

JFrame frame = new JFrame("Dots");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.getContentPane().add(new DotsPanel());

frame.pack();

frame.setVisible(true);

}

}

DotsPanel.java

import java.awt.Color;

import java.awt.Dimension;

import java.awt.Graphics;

import java.awt.Point;

import java.awt.Rectangle;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.MouseEvent;

import java.awt.event.MouseListener;

import java.awt.event.MouseMotionListener;

import java.security.SecureRandom;

import java.util.ArrayList;

import java.util.Random;

import javax.swing.JPanel;

import javax.swing.Timer;

public class DotsPanel extends JPanel {

private final int SIZE = 6; // radius of each dot

private ArrayList pointList;

AnimationListener am;

// -----------------------------------------------------------------

// Constructor: Sets up this panel to listen for mouse events.

// -----------------------------------------------------------------

public DotsPanel() {

pointList = new ArrayList();

// addMouseListener(new DotsListener());

addMouseMotionListener(new DotsMouseMotionListener());

am = new AnimationListener();

am.timer.start();

setBackground(Color.black);

setPreferredSize(new Dimension(300, 200));

}

private void setColor(Color color) {

}

public void paint(Graphics page) {

super.paintComponent(page);

SecureRandom randomNum = new SecureRandom();

Color color = new Color(randomNum.nextInt(256), randomNum.nextInt(256),

randomNum.nextInt(256));

page.setColor(color);

for (Point spot : pointList)

page.fillRect(spot.x - SIZE, spot.y - SIZE, SIZE * 2, SIZE * 2);

page.drawString("Count: " + pointList.size(), 5, 15);

}

private class AnimationListener implements ActionListener {

int xRand[];

int yRand[];

Random rand;

public AnimationListener() {

rand = new Random();

xRand = new int[1000];

yRand = new int[1000];

for (int i = 0; i < 1000; i++) {

xRand[i] = rand.nextInt(20) - 10;

yRand[i] = rand.nextInt(20) - 10;

}

}

private Timer timer = new Timer(50, this);

public void actionPerformed(ActionEvent e) {

Rectangle window = getBounds();

for (int i = 0; i < pointList.size(); i++) {

Point spot = pointList.get(i);

spot.x += xRand[i];

spot.y += yRand[i];

if (spot.x <= 0) {

xRand[i] = Math.abs(xRand[i]);

} else if (spot.x >= window.width - (SIZE * 2)) {

xRand[i] = -Math.abs(xRand[i]);

}

if (spot.y <= 0) {

yRand[i] = Math.abs(yRand[i]);

} else if (spot.y >= window.height - (SIZE * 2)) {

yRand[i] = -Math.abs(yRand[i]);

}

}

repaint();

}

}

private class DotsListener implements MouseListener {

public void mousePressed(MouseEvent event) {

pointList.add(event.getPoint());

repaint();

}

public void mouseClicked(MouseEvent event) {

}

public void mouseReleased(MouseEvent event) {

}

public void mouseEntered(MouseEvent event) {

}

public void mouseExited(MouseEvent event) {

}

}

private class DotsMouseMotionListener implements MouseMotionListener {

public void mouseDragged(MouseEvent event) {

System.out.println(event.getPoint().toString());

pointList.add(event.getPoint());

repaint();

}

public void mouseMoved(MouseEvent e) {

}

}

}