Java Assignment Sample: Building Software with Objects, Graphics, Containers, and Animation

ANIMATE YOUR CODE: JAVA ASSIGNMENT
SAMPLES!
Programming in Java: Building
Software with Objects, Graphics, and
Animation

Introduction
 Objective: Learn how to create and animate
graphical objects in Java.
 Topics Covered:
 Object-Oriented Programming (OOP) in Java
 Java’s built-in graphics and containers
 Creating and animating shapes
 Key Features:
 Simple, secure, and robust
 Multithreading capabilities
 Rich API for building diverse applications

Understanding the Classes
 SimpleDraw:Manages the window and rendering
 Contains the main method
 BouncingBox:Represents a box that moves and
bounces within the window
 DrawGraphics:Manages drawing and animating
graphics on the screen

In the last assignment you learned how to create your own simple objects. One of the
advantages of building software using objects is that it makes it relatively easy to use
software components that other people have built. In this assignment, you will use
the Java's built-in graphics and containers, combined with a simple framework that
we provide. Add three different shapes to the initial window we provide.
Requirements:
Add three instances of the BouncingBox class to your window, moving in different
directions. Use an ArrayList to hold them.
Setup:
1.(Optional) Create a new project in Eclipse, with whatever name you want.
2.Create three classes: SimpleDraw, BouncingBox, and DrawGraphics. Copy and
paste the code for these classes from below.
3.Run the example program. If Eclipse gives you trouble, open SimpleDraw and run
that, as it contains the main method for the program. You should see a window that
looks like the following:

Part 1: Drawing Graphics
Open the DrawGraphics class. The draw method is what draws the contents of the
window. Currently, there is a line and a square with a border around it. Feel free to
remove these, if you want. Add at least three different shapes to the window. Read
the API documentation for the java.awt.Graphics class to find what methods are
provided. You can draw rectangles, arcs, lines, text, ovals, polygons, and, if you
want to do some extra work, images. Be creative!
Note: You should only modify the DrawGraphics class for this step. The other
classes contain a bunch of code required to create a window in Java that you do
not need to change or understand.

Part 2 : Containers & Animations
The DrawGraphics class supports animation. The draw method gets called 20
times a second, in order to draw each individual frame. The BouncingBox class
also includes animation support. To get the box to move, call setMovementVector
method from the DrawGraphics constructor, providing an x and y offset. For
example, the value (1, 0) moves the box to the right slowly, while (0, -2) will move
it up faster. You only need to call this method once to keep it moving in that
direction. In other words, don't call setMovementVector from the draw method,
call it from the constructor.
Add at least three boxes to your window, moving in different directions. To do
this, put three BouncingBox instances in an ArrayList, as part of the
DrawGraphics constructor. Then, call the draw method on each of the boxes from
DrawGraphics.draw, using a loop.
Optional: If you want to experiment, create your own animated object. Copy
BouncingBox as a starting point, then edit the code in its draw method. You
could create something with more complicated movement, and/or something
that looks better than what I created in five minutes.
Submission Instructions:
Submit your DrawGraphics.java file via Stellar.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** Displays a window and delegates drawing to DrawGraphics. */
public class SimpleDraw extends JPanel implements Runnable {
private static final long serialVersionUID =-7469734580960165754L;
private boolean animate = true;
private final int FRAME_DELAY = 50; // 50 ms = 20 FPS
public static final int WIDTH = 300; public static final int HEIGHT = 300; private
DrawGraphics draw;
public SimpleDraw(DrawGraphics drawer){
this.draw = drawer;

}
/** Paint callback from Swing. Draw graphics using g. */
public void paintComponent(Graphics g){
super.paintComponent(g);
// Enable anti-aliasing for better looking graphics
Graphics2D g2 =(Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
draw.draw(g2);
}
/** Enables periodic repaint calls. */
public synchronized void start() {
animate = true;
}

/** Pauses animation. */
public synchronized void stop() {
animate = false;
}
private synchronized boolean animationEnabled() {
return animate;
}
public void run() {
while (true){
if (animationEnabled()) {
repaint();
}
try {
Thread.sleep(FRAME_DELAY);
} catch (InterruptedException e){
throw new RuntimeException(e);
}}
}
public static void main(String args[]) { final SimpleDraw content = new
SimpleDraw(new DrawGraphics());
JFrame frame = new JFrame("Graphics!");

Color bgColor = Color.white;
frame.setBackground(bgColor);
content.setBackground(bgColor);
// content.setSize(WIDTH, HEIGHT); // content.setMinimumSize(new
Dimension(WIDTH, HEIGHT));
content.setPreferredSize(new Dimension(WIDTH, HEIGHT));
// frame.setSize(WIDTH, HEIGHT);
frame.setContentPane(content);
frame.setResizable(false);
frame.pack();
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e){ System.exit(0); } public void
windowDeiconified(WindowEvent e){ content.start(); } public void
windowIconified(WindowEvent e){ content.stop(); }
});
new Thread(content).start();
frame.setVisible(true);
}
}

import java.awt.BasicStroke;
public class BouncingBox {
int x;
int y;
Color color;
int xDirection = 0;
int yDirection = 0;
final int SIZE = 20;
/**
*
Initialize a new box with its center located at (startX, startY), filled
*
with startColor.
*/

public BouncingBox(int startX, int startY, Color startColor){
x = startX;
y = startY;
color = startColor;
}
/** Draws the box at its current position on to surface. */
public void draw(Graphics surface){
// Draw the object
surface.setColor(color);
surface.fillRect(x - SIZE/2, y - SIZE/2, SIZE, SIZE);
surface.setColor(Color.BLACK);
((Graphics2D) surface).setStroke(new BasicStroke(3.0f));
surface.drawRect(x - SIZE/2, y - SIZE/2, SIZE, SIZE);

// If we have hit the edge and are moving in the wrong direction, reverse direction
// We check the direction because if a box is placed near the wall, we would get
"stuck" // rather than moving in the right direction
if ((x - SIZE/2 <= 0 && xDirection < 0) ||
(x + SIZE/2 >= SimpleDraw.WIDTH && xDirection > 0)) {
xDirection =-xDirection;
}
if ((y - SIZE/2 <= 0 && yDirection < 0) ||
(y + SIZE/2 >= SimpleDraw.HEIGHT && yDirection > 0)) {
yDirection =-yDirection;
}
}
public void setMovementVector(int xIncrement, int yIncrement){ xDirection =
xIncrement; yDirection = yIncrement;
}
}
// Move the center of the object each time we draw it
x += xDirection;
y += yDirection;

DrawGraphics.java
public class DrawGraphics {
BouncingBox box;
/** Initializes this class for drawing. */
public DrawGraphics() {
box = new BouncingBox(200, 50, Color.RED);
}
/** Draw the contents of the window on surface. Called 20 times per second. */
public void draw(Graphics surface){
surface.drawLine(50, 50, 250, 250);
box.draw(surface);
}
}

import java.awt.Dimension;
import java.awt.RenderingHints;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** Displays a window and delegates drawing to DrawGraphics. */
public class SimpleDraw extends JPanel implements Runnable {
private static final long serialVersionUID = -7469734580960165754L;
private boolean animate = true;
private final int FRAME_DELAY = 50; // 50 ms = 20 FPS
public static final int WIDTH = 300;
public static final int HEIGHT = 300;
private DrawGraphics draw;

public SimpleDraw(DrawGraphics drawer) {
this.draw = drawer;
}
/** Paint callback from Swing. Draw graphics using g. */
public void paintComponent(Graphics g) {
super.paintComponent(g);
// Enable anti-aliasing for better looking graphics
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
draw.draw(g2);
}
/** Enables periodic repaint calls. */
public synchronized void start() {
animate = true;
}
/** Pauses animation. */

public synchronized void stop() {
animate = false;
}
private synchronized boolean animationEnabled() {
return animate;
}
public void run() {
while (true) {
if (animationEnabled()) {
repaint();
}
try {
Thread.sleep(FRAME_DELAY);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
}

public static void main(String args[]) {
final SimpleDraw content = new SimpleDraw(new DrawGraphics());
JFrame frame = new JFrame("Graphics!");
Color bgColor = Color.white;
frame.setBackground(bgColor);
content.setBackground(bgColor);
// content.setSize(WIDTH, HEIGHT);
// content.setMinimumSize(new Dimension(WIDTH, HEIGHT));
content.setPreferredSize(new Dimension(WIDTH, HEIGHT));
// frame.setSize(WIDTH, HEIGHT);
frame.setContentPane(content);
frame.setResizable(false);
frame.pack();
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) { System.exit(0); }
public void windowDeiconified(WindowEvent e) { content.start(); }
public void windowIconified(WindowEvent e) { content.stop(); }
});

new Thread(content).start();
frame.setVisible(true);
}
}
import java.awt.BasicStroke;
public class BouncingBox {
int x;
int y;
Color color;
int xDirection = 0;
int yDirection = 0;
final int SIZE = 20;

/**
Initialize a new box with its center located at (startX, startY), filled
* with startColor.
*/
public BouncingBox(int startX, int startY, Color startColor) {
x = startX;
y = startY;
color = startColor;
}
/** Draws the box at its current position on to surface. */
public void draw(Graphics surface) {
// Draw the object
surface.setColor(color);
surface.fillRect(x - SIZE/2, y - SIZE/2, SIZE, SIZE);
surface.setColor(Color.BLACK);
((Graphics2D) surface).setStroke(new BasicStroke(3.0f));
surface.drawRect(x - SIZE/2, y - SIZE/2, SIZE, SIZE);
// Move the center of the object each time we draw it
x += xDirection;
y += yDirection;

// If we have hit the edge and are moving in the wrong direction, reverse direction
// We check the direction because if a box is placed near the wall, we would get
"stuck"
// rather than moving in the right direction
if ((x - SIZE/2 <= 0 && xDirection < 0) ||
(x + SIZE/2 >= SimpleDraw.WIDTH && xDirection > 0)) {
xDirection = -xDirection;
}
if ((y - SIZE/2 <= 0 && yDirection < 0) ||
(y + SIZE/2 >= SimpleDraw.HEIGHT && yDirection > 0)) {
yDirection = -yDirection;
}
}
public void setMovementVector(int xIncrement, int yIncrement) {
xDirection = xIncrement;
yDirection = yIncrement;
}
}

public class DrawGraphics {
BouncingBox box;
/** Initializes this class for drawing. */
public DrawGraphics() {
box = new BouncingBox(200, 50, Color.RED);
}
/** Draw the contents of the window on surface. Called 20 times per second. */
public void draw(Graphics surface) {
surface.drawLine(50, 50, 250, 250);
box.draw(surface);
}
}

Summary:
Reviewed Java basics, OOP principles, graphics, containers, and animation
Provided sample code and project ideas
Next Steps:
Experiment with code examples
Start building your own Java applications
Explore advanced Java topics and libraries
Contact Information:
For more help and custom programming assignments, visit
programminghomeworkhelp.com

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