Processing Language: Bouncing balls. Create a program starts one ball bouncing a

Question

Processing Language: Bouncing balls. Create a program starts one ball bouncing around the window. The ball should have a horizontal and vertical velocity.

A left mouse click will add another bouncing ball to the screen, up to a maximum of four balls.

Each right mouse click will change the color of one of the balls. Count the number of right mouse clicks. When the count % number of balls is 0, generate a rgb random color for ball 0. When the count % number of balls is 1, generate a rgb random color for ball 1, etc. You will need a random value for the red channel, green channel, and blue channel. Only change color when there is a right mouse click event.

Use arrays to store information about the balls. Example: create arrays for each of the color channels. Ball 0

Explanation / Answer

import java.awt.*; import java.util.Formatter; import javax.swing.*; /** * One ball bouncing inside a rectangular box. * All codes in one file. Poor design! */ // Extends JPanel, so as to override the paintComponent() for custom rendering codes. public class BouncingBallSimple extends JPanel { // Container box's width and height private static final int BOX_WIDTH = 640; private static final int BOX_HEIGHT = 480; // Ball's properties private float ballRadius = 200; // Ball's radius private float ballX = ballRadius + 50; // Ball's center (x, y) private float ballY = ballRadius + 20; private float ballSpeedX = 3; // Ball's speed for x and y private float ballSpeedY = 2; private static final int UPDATE_RATE = 30; // Number of refresh per second /** Constructor to create the UI components and init game objects. */ public BouncingBallSimple() { this.setPreferredSize(new Dimension(BOX_WIDTH, BOX_HEIGHT)); // Start the ball bouncing (in its own thread) Thread gameThread = new Thread() { public void run() { while (true) { // Execute one update step // Calculate the ball's new position ballX += ballSpeedX; ballY += ballSpeedY; // Check if the ball moves over the bounds // If so, adjust the position and speed. if (ballX - ballRadius < 0) { ballSpeedX = -ballSpeedX; // Reflect along normal ballX = ballRadius; // Re-position the ball at the edge } else if (ballX + ballRadius > BOX_WIDTH) { ballSpeedX = -ballSpeedX; ballX = BOX_WIDTH - ballRadius; } // May cross both x and y bounds if (ballY - ballRadius < 0) { ballSpeedY = -ballSpeedY; ballY = ballRadius; } else if (ballY + ballRadius > BOX_HEIGHT) { ballSpeedY = -ballSpeedY; ballY = BOX_HEIGHT - ballRadius; } // Refresh the display repaint(); // Callback paintComponent() // Delay for timing control and give other threads a chance try { Thread.sleep(1000 / UPDATE_RATE); // milliseconds } catch (InterruptedException ex) { } } } }; gameThread.start(); // Callback run() } /** Custom rendering codes for drawing the JPanel */ @Override public void paintComponent(Graphics g) { super.paintComponent(g); // Paint background // Draw the box g.setColor(Color.BLACK); g.fillRect(0, 0, BOX_WIDTH, BOX_HEIGHT); // Draw the ball g.setColor(Color.BLUE); g.fillOval((int) (ballX - ballRadius), (int) (ballY - ballRadius), (int)(2 * ballRadius), (int)(2 * ballRadius)); // Display the ball's information g.setColor(Color.WHITE); g.setFont(new Font("Courier New", Font.PLAIN, 12)); StringBuilder sb = new StringBuilder(); Formatter formatter = new Formatter(sb); formatter.format("Ball @(%3.0f,%3.0f) Speed=(%2.0f,%2.0f)", ballX, ballY, ballSpeedX, ballSpeedY); g.drawString(sb.toString(), 20, 30); } /** main program (entry point) */ public static void main(String[] args) { // Run GUI in the Event Dispatcher Thread (EDT) instead of main thread. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { // Set up main window (using Swing's Jframe) JFrame frame = new JFrame("A Bouncing Ball"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setContentPane(new BouncingBallSimple()); frame.pack(); frame.setVisible(true); } }); } }

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