Java tutorial
/* This program is a part of the companion code for Core Java 8th ed. (http://horstmann.com/corejava) This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ import java.awt.BorderLayout; import java.awt.Container; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.geom.Ellipse2D; import java.awt.geom.Rectangle2D; import java.util.ArrayList; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; /** * Shows an animated bouncing ball. * * @version 1.33 2007-05-17 * @author Cay Horstmann */ public class Bounce { public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { JFrame frame = new BounceFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } }); } } /** * The frame with ball component and buttons. */ class BounceFrame extends JFrame { /** * Constructs the frame with the component for showing the bouncing ball and * Start and Close buttons */ public BounceFrame() { setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT); setTitle("Bounce"); comp = new BallComponent(); add(comp, BorderLayout.CENTER); JPanel buttonPanel = new JPanel(); addButton(buttonPanel, "Start", new ActionListener() { public void actionPerformed(ActionEvent event) { addBall(); } }); addButton(buttonPanel, "Close", new ActionListener() { public void actionPerformed(ActionEvent event) { System.exit(0); } }); add(buttonPanel, BorderLayout.SOUTH); } /** * Adds a button to a container. * * @param c * the container * @param title * the button title * @param listener * the action listener for the button */ public void addButton(Container c, String title, ActionListener listener) { JButton button = new JButton(title); c.add(button); button.addActionListener(listener); } /** * Adds a bouncing ball to the panel and makes it bounce 1,000 times. */ public void addBall() { try { Ball ball = new Ball(); comp.add(ball); for (int i = 1; i <= STEPS; i++) { ball.move(comp.getBounds()); comp.paint(comp.getGraphics()); Thread.sleep(DELAY); } } catch (InterruptedException e) { } } private BallComponent comp; public static final int DEFAULT_WIDTH = 450; public static final int DEFAULT_HEIGHT = 350; public static final int STEPS = 1000; public static final int DELAY = 3; } /* * This program is a part of the companion code for Core Java 8th ed. * (http://horstmann.com/corejava) * * This program is free software: you can redistribute it and/or modify it under * the terms of the GNU General Public License as published by the Free Software * Foundation, either version 3 of the License, or (at your option) any later * version. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more * details. * * You should have received a copy of the GNU General Public License along with * this program. If not, see <http://www.gnu.org/licenses/>. */ /** * The component that draws the balls. * * @version 1.33 2007-05-17 * @author Cay Horstmann */ class BallComponent extends JPanel { /** * Add a ball to the component. * * @param b * the ball to add */ public void add(Ball b) { balls.add(b); } public void paintComponent(Graphics g) { super.paintComponent(g); // erase background Graphics2D g2 = (Graphics2D) g; for (Ball b : balls) { g2.fill(b.getShape()); } } private ArrayList<Ball> balls = new ArrayList<Ball>(); } /* * This program is a part of the companion code for Core Java 8th ed. * (http://horstmann.com/corejava) * * This program is free software: you can redistribute it and/or modify it under * the terms of the GNU General Public License as published by the Free Software * Foundation, either version 3 of the License, or (at your option) any later * version. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more * details. * * You should have received a copy of the GNU General Public License along with * this program. If not, see <http://www.gnu.org/licenses/>. */ /** * A ball that moves and bounces off the edges of a rectangle * * @version 1.33 2007-05-17 * @author Cay Horstmann */ class Ball { /** * Moves the ball to the next position, reversing direction if it hits one of * the edges */ public void move(Rectangle2D bounds) { x += dx; y += dy; if (x < bounds.getMinX()) { x = bounds.getMinX(); dx = -dx; } if (x + XSIZE >= bounds.getMaxX()) { x = bounds.getMaxX() - XSIZE; dx = -dx; } if (y < bounds.getMinY()) { y = bounds.getMinY(); dy = -dy; } if (y + YSIZE >= bounds.getMaxY()) { y = bounds.getMaxY() - YSIZE; dy = -dy; } } /** * Gets the shape of the ball at its current position. */ public Ellipse2D getShape() { return new Ellipse2D.Double(x, y, XSIZE, YSIZE); } private static final int XSIZE = 15; private static final int YSIZE = 15; private double x = 0; private double y = 0; private double dx = 1; private double dy = 1; }