第十二周java作业

package fff;
 
public class test {
   public static void main(String[] args) {
            String str = "Hello World";
            char[] c = str.toCharArray();
            StringBuffer buffer = new StringBuffer();
 
            for (int i = str.length() - 1; i >= 0; i--) {
                if ((c[i] >= 'A') && (c[i] <= 'Z')) {
                    buffer.append(String.valueOf(c[i]).toLowerCase());
                } else if ((c[i] >= 'a') && (c[i] <= 'z')) {
                    buffer.append(String.valueOf(c[i]).toUpperCase());
                }
            }
            System.out.println(buffer.toString());
        }
     
}

package fff;
import java.util.Random;
     
public class test {
        public static void main(String[] args) {
            Random rand = new Random();
            int[] num = new int[5];
     
            for (int i=0; i<num.length; i++) {
                num[i] = 20 + rand.nextInt(31);
                System.out.println(num[i]);
            }
        }
    }