15.4

 1 import java.awt.*;
 2 import javax.swing.*;
 3 
 4 public class Test_15 extends JFrame {
 5   public Test_15() {
 6     add(new MultiplicationTablePanel());
 7   }
 8 
 9   public static void main(String[] args) {
10       Test_15 frame = new Test_15();
11     frame.setSize(300, 400);
12     frame.setTitle("Exercise15_4");
13     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
14     frame.setLocationRelativeTo(null); // Center the frame
15     frame.setVisible(true);
16   }
17 }
18 
19 class MultiplicationTablePanel extends JPanel {
20   protected void paintComponent(Graphics g) {
21     super.paintComponent(g);
22 
23     int x = 10;
24     int y = 40;
25     String s = "";
26     int i = 0;
27 
28     // Display the title
29     g.setColor(Color.red);
30     g.setFont(new Font("Times", Font.BOLD, 20));
31     g.drawString("Multiplication Table", x+50, y);
32 
33     g.setFont(new Font("Times",Font.BOLD,15));
34 
35     y += 30;
36     for (i = 1; i < 10; i++)
37       g.drawString(" " + i, x + 10, y + 10 + i * 20);
38 
39     x += 40;
40     for (i = 1; i < 10; i++) {
41       s = s + "   " + i;
42     }
43     g.drawString(s, x, y);
44 
45     y += 10;
46     g.drawRect(x, y, 200, 200);
47 
48     s = "";
49     y += 20;
50 
51     for (i = 1; i < 10; i++) {
52       for (int j = 1; j < 10; j++) {
53         if (i*j < 10)
54           s = s + "   " + i * j;
55         else
56           s = s + " " + i * j;
57       }
58 
59       g.drawString(s, x, y);
60       s = "";
61       y += 20;
62     }
63   }
64 }
Test_15.java
结果如下：