ball.java

一些JAVA的小程序

//
//	general purpose reusable bounding ball abstraction
//
//	From Chapter 5 of
//	Understanging Object-Oriented Programming with Java
//	Written by Tim Budd
//	Published by Addison-Wesley Longman
//
//	See ftp://ftp.cs.orst.edu/pub/budd/java/ReadMe.html 
//	for further information
//

import java.awt.*;

public class Ball {
	protected Rectangle location;
	protected double dx;
	protected double dy;
	protected Color color;
	
	public Ball (int x, int y, int r)
	{
		location = new Rectangle(x-r, y-r, 2*r, 2*r);
		dx = 0;
		dy = 0;
		color = Color.blue;
	}
	
		// functions that set attributes
	public void setColor (Color newColor)
				{ color = newColor;	}

	public void setMotion (double ndx, double ndy)
				{ dx = ndx; dy = ndy; }
	
		// functions that access attributes of ball
	public int radius ()
				{ return location.width / 2; }
	
	public int x ()
				{ return location.x + radius(); }
	
	public int y ()
				{ return location.y + radius(); }
	
	public double xMotion ()
				{ return dx; }

	public double yMotion ()
				{ return dy; }

	public Rectangle region () { return location; }

		// functions that change attributes of ball
	public void moveTo (int x, int y)
				{ location.setLocation(x, y); }

	public void move ()
				{ location.translate ((int) dx, (int) dy); }
	
	public void paint (Graphics g)
	{
		g.setColor (color);
		g.fillOval (location.x, location.y, location.width, location.height);
	}
}