ball.java

一些JAVA的小程序

import java.awt.*;

public class Ball {

    public Ball (Point lc, int r) { loc = lc; rad = r; }

    protected Point loc; // position in window
    protected int rad; // radius 
    protected double changeInX = 0.0;
    protected double changeInY = 0.0;
    protected Color color = Color.blue; // color of ball

    public void setColor (Color newColor) { color = newColor; }

    public void setMotion (double dx, double dy) 
       { changeInX = dx; changeInY = dy; }

    public int radius () { return rad; }

    public Point location () { return loc; }

    public void reflectVert () { changeInX = - changeInX; }

    public void reflectHorz () { changeInY = - changeInY; }

    public int x () { return loc.x; }

    public int y () { return loc.y; }

    public void moveTo (int x, int y) { loc.move(x, y); }

    public void move () 
       { loc.translate((int) changeInX, (int) changeInY); }

    public void paint (Graphics g) {
        g.setColor (color);
        g.fillOval (loc.x-rad, loc.y-rad, 2*rad, 2*rad);
    }
}