Objects and Classes
Introducing Classes and Objects
The bubbles you produce here don't just grow, they breathe! To achieve this, we need more than one object of our BreathingBubbles class, to make every one of them really independent from the others. To achieve this, we create an array of 100 bubble objects. With each mouseclick, a new one is created and initialized with the mouse coordinates. The object is responsible for it's own color, minimum diameter and maximum diameter.
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//Sourcecode
import java.awt.*;
import java.applet.*;
class BreathingBubble
{
//instance variables
int x, y, diameter, startDiameter, endDiameter;
boolean growing=true;
Color randomColor;
Graphics g;
//constructor
public BreathingBubble()
{
int red=(int)(Math.random()*255);
int green=(int)(Math.random()*255);
int blue=(int)(Math.random()*255);
//each bubble object has one random color
randomColor=new Color(red, green, blue);
//start diameter between 10 and 30
startDiameter=(int)(Math.random()*20)+10;
//end diameter between 50 and 150
endDiameter=(int)(Math.random()*100)+50;
diameter=startDiameter;
}
public void setPosition(int x, int y)
{
this.x=x;
this.y=y;
}
public void drawBubble()
{
g.setColor(randomColor);
g.fillOval(x-diameter/2,y-diameter/2,diameter,diameter);
}
public void breathe()
{
//grow till end diameter is reached
if(growing)
{
if(diameter<endDiameter)
diameter++;
else
growing=false;
}
//shrink till start diameter is reached
else
{
if(diameter>startDiameter)
diameter--;
else
growing=true;
}
}
public void paint(Graphics gr)
{
g=gr;
drawBubble();
}
}
public class Project25 extends Applet implements Runnable
{
Image Buffer;
Graphics gBuffer;
BreathingBubble myBubble[];
Thread runner;
boolean clicked;
int index;
int MAX=100;
public void init()
{
Buffer=createImage(size().width,size().height);
gBuffer=Buffer.getGraphics();
myBubble = new BreathingBubble[MAX];
}
public void start()
{
if (runner == null)
{
runner = new Thread (this);
runner.start();
}
}
public void stop()
{
if (runner != null)
{
runner.stop();
runner = null;
}
}
public void run()
{
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
while(true)
{
try {runner.sleep(15);}
catch (Exception e) { }
//bubble methods may only be accessed, if we have
//created the object in the mouseDown method!
if(clicked)
{
for(int i=0;i<index;i++)
{
myBubble[i].breathe();
myBubble[i].paint(gBuffer);
}
}
repaint();
}
}
public boolean mouseDown(Event evt,int x,int y)
{
if(index<MAX)
{
myBubble[index] = new BreathingBubble();
myBubble[index].setPosition(x,y);
index++;
}
clicked=true;
return true;
}
public void update(Graphics g)
{
paint(g);
}
public void paint(Graphics g)
{
gBuffer.setColor(Color.black);
gBuffer.drawString("Click the applet to paint breathing bubbles!", 20,20);
g.drawImage (Buffer,0,0, this);
//paint the background white (must be done last!)
gBuffer.setColor(Color.white);
gBuffer.fillRect(0,0,size().width,size().height);
}
}
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