java小球自由落体

小球的自由落体运动！ import java.awt.*; import javax.swing.*; public class TextBall extends JFrame{ public TextBall(){ super("the ball moving"); setSize(130,500); setVisible(true); } public void paint(Graphics g) { super.paint(g); g.setColor(Color.white); g.fillRect(20,40,50,430); g.setColor(