15.5

 1 import java.awt.*;
 2 import javax.swing.*;
 3
 4 public class Test_15 extends JFrame {
 5   public Test_15() {
 6     add(new PiramidPanel());
 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_5");
13     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
14     frame.setLocationRelativeTo(null); // Center the frame
15     frame.setVisible(true);
16   }
17 }
18
19 class PiramidPanel extends JPanel {
20   protected void paintComponent(Graphics g) {
21     super.paintComponent(g);
22
23     int x = 10, y =20;
24     String s = "";
25     for(int i=1 ; i < getHeight() ; i++){
26         for(int j=0; j < i && j < getWidth(); j++){
27             s = s + " " + (j+1);
28         }
29
30         g.drawString(s, x, y);
31         y += 20;
32         s = "";
33     }
34
35   }
36 }

Test_15.java

由于在PiramidPanel类中对于行和列的宽度使用了getWidth()和getHeight()函数做限制，所以在拖动窗口时，会根据窗口大小动态调整显示的行和列数。

效果图：