待解：通过把第6位设置为0使小写字母都变成大写字母

 1 class UpCase {
 2     public static void main(String[] args) {
 3         char ch;
 4         
 5         for (int i = 0; i < 10; i++) {
 6             ch = (char) (‘a‘ + i);
 7             System.out.print(ch);
 8             
 9             // This statement turns off the 6th bit.
10             ch = (char) ((int) ch & 65503); // ch is now uppercase
11             
12             System.out.print(ch + " ");
13         }
14     }
15 }