Tyler's Java Website

Milky Way

This application had several requirements:

• Learn to use Loops / Repetitions
• Work with random numbers
• Write a program that draws 100 circles at random positions in the window and with random diameters up to 100 pixels.
• Circles should be painted in random colors.

The Code

The main thing that was standing in my way was understanding how my loop was working. Initially, I was drawing random spheres, 100 at a time, per a few hundred milliseconds. I couldn't understand why my code wouldn't stop after 100 spheres were drawn. Eventually, I came to understand that it the loop was working as intended, because I would continually reset 'i' to '0' every loop, resulting in 100 spheres every loop. I fixed the issue by limiting how many times the loop could run, which was only once per button press. In the future I would like to add some physics to the applet, and make the stars behave as they would with mass in space. I think it would be pretty awesome.
Here is the code for my application. Please do not steal it. You will get caught.

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferStrategy;
import java.util.Random;

import javax.swing.*;

/**
 * Class MilkyWay - write a description of the class here
 * 
 * @author Tyler Persohn
 * @version 1.0
 */

public class MilkyWay extends JApplet implements ActionListener, Runnable {

	private JLabel title;
	private JButton BEGIN, OFF;
	private Canvas canvas;

	private enum UniverseState {
		BEGIN, OFF;
	}

	private UniverseState state = UniverseState.OFF;
	private Random random = new Random();

	public void init() {

		// this is a workaround for a security conflict with some browsers
		JRootPane rootPane = this.getRootPane();
		rootPane.putClientProperty("defeatSystemEventQueueCheck", Boolean.TRUE);

		Container contentPane = getContentPane(); // Size of the entire applet.
		contentPane.setBackground(Color.BLACK); // Background color.

		contentPane.setLayout(new BorderLayout());
		contentPane.add(createTitlePanel(), BorderLayout.NORTH); // Title placement.
		contentPane.add(createButtonPanel(), BorderLayout.SOUTH);// Button placement.

		// Because repaint sucks.
		canvas = new Canvas();
		getContentPane().add(canvas, BorderLayout.CENTER);
		canvas.createBufferStrategy(2); // Image buffer
		run();
	}

	private Component createButtonPanel() {
		// Button Controls
		JPanel controls = new JPanel();
		controls.setLayout(new FlowLayout());
		controls.add(BEGIN = new JButton("ADD STARS")); //Button title.
		BEGIN.addActionListener(this);
		controls.add(OFF = new JButton("RESET"));
		OFF.addActionListener(this);
		return controls;
	}

	private Component createTitlePanel() {
		// Title Attributes
		JPanel titlePanel = new JPanel();
		titlePanel.setLayout(new FlowLayout());
		titlePanel.add(title = new JLabel("Milky Way", JLabel.CENTER)); //App title.
		title.setForeground(Color.WHITE);
		titlePanel.setBackground(Color.BLACK);
		return titlePanel;
	}

	public void render(Graphics g) {

		switch (state) {

		case BEGIN:
			int maxCircles = 100;
			int diameter;
			int x,
			y;
			for (int i = 0; i < maxCircles; ++i) {     // Draw from 0 until 100.
				diameter = random.nextInt(100);         // Random diameter.
				x = random.nextInt(canvas.getWidth()); // Random x position on canvas.
				y = random.nextInt(canvas.getHeight());// Random y position on canvas.
				g.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256))); //Set color to random.
				g.fillOval(x, y, diameter, diameter);  // Draw the circle.
			}
			break;

		case OFF: //When resetting canvas
			g.setColor(Color.BLACK);
			g.fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
			break;
		}
	}

	@Override
	public void run() {

		BufferStrategy bs = canvas.getBufferStrategy();
		Graphics2D g = (Graphics2D) bs.getDrawGraphics(); // Get graphics
		render(g);    // Call render
		g.dispose(); // Cleanup
		bs.show();  // Pull new frame
	}

	@Override
	public void actionPerformed(ActionEvent event) {
		//Set state according to user input.
		if (event.getSource() == BEGIN) {
			state = UniverseState.BEGIN;
			run();
		}
		if (event.getSource() == OFF) {
			state = UniverseState.OFF;
			run();
		}

	}
}

Milky Way Applet