16.15

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class Test_16_15 extends JFrame{
    
    public Test_16_15(){
        add(new JP());
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Test_16_15 frame = new Test_16_15();        
        frame.setSize(200, 200);
        frame.setTitle("Test_16_15");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null); // Center the frame
        frame.setVisible(true); 
    }
    
    class JP extends JPanel{        
        private int width ;
        private int height;
        private int x = 30 , y = 150;

        public JP(){
            Timer timer = new Timer(1000,new TimerListener());
            timer.start();
        }
        protected void paintComponent(Graphics g)
        {    
            width = getWidth();
            height = getHeight();
            
            super.paintComponent(g);
            
            if(x > width) x = 0;
            g.fillOval(x + 30, y, 10, 10);
            g.fillRect(x, y - 10, 50, 10);
            x += 20;
        }
        class TimerListener implements ActionListener{

            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub
                repaint();
            }
            
        }
    }
}

如图：