练习：菱形

 1                        //上半部分
 2                 for (int m = 1; m <= 10; m++)
 3                 {
 4                     //输出空格
 5                     for (int n = 9; n >= m ;n--)
 6                     {
 7                         System.out.print(" ");
 8                     }
 9                     //输出* 左上
10                     for (int n = 1; n <= m; n++)
11                     {
12                         System.out.print("*");
13                     }    
14                     
15                     //右上
16                     for (int n = 1; n < m; n++)
17                     {
18                         System.out.print("*");
19                     }
20 
21                     System.out.println();
22                 }
23                 
24                 //下半部分
25                 for (int m = 1; m <= 9; m++)
26                 {
27                     //输出空格
28                     for (int n = 1; n <= m ;n++)
29                     {
30                         System.out.print(" ");
31                     }
32                     //输出* 左下
33                     for (int n = 9; n >= m; n--)
34                     {
35                         System.out.print("*");
36                     }    
37                     
38                     //右下
39                     for (int n = 9; n > m; n--)
40                     {
41                         System.out.print("*");
42                     }
43 
44                     System.out.println();
45                 }