code: public static String generateRandomString(int length) {
  
          char[] chars = "abcdefghijklmnopqrstuvwxyz1234567890".toCharArray();
          StringBuilder sb = new StringBuilder();
          Random random = new Random();
          for (int i = 0; i < 20; i++) {
              char c = chars[random.nextInt(chars.length)];
              sb.append(c);
          }
  
          return sb.toString();
      }
docs: Generates a random alphanumeric String of the length specified
  
  @param length The required length of the String
  
  @return A random alphanumeric String