第十二周作业。

 1 package Pro1;
 2 
 3 public class Test {
 4     public static void main(String[] args) {
 5         String str = "Hello World";
 6         char[] c = str.toCharArray();
 7         StringBuffer buffer = new StringBuffer();
 8 
 9         for (int i = str.length() - 1; i >= 0; i--) {
10             if ((c[i] >= 'A') && (c[i] <= 'Z')) {
11                 buffer.append(String.valueOf(c[i]).toLowerCase());
12             } else if ((c[i] >= 'a') && (c[i] <= 'z')) {
13                 buffer.append(String.valueOf(c[i]).toUpperCase());
14             }
15         }
16         System.out.println(buffer.toString());
17     }
18 }

 1 package pro2;
 2 import java.util.Random;
 3 public class Test2 {
 4     public static void main(String[] args) {
 5         Random rand = new Random();
 6         int[] num = new int[5];
 7         for (int i = 0; i < num.length; i++) {
 8             num[i] = 20 + rand.nextInt(31);
 9             System.out.println(num[i]);
10         }
11     }
12 }