code: public static String upperFirst(CharSequence s) {
          if (null == s)
              return null;
          int len = s.length();
          if (len == 0)
              return "";
          char c = s.charAt(0);
          if (Character.isUpperCase(c))
              return s.toString();
          return new StringBuilder(len).append(Character.toUpperCase(c))
                                       .append(s.subSequence(1, len))
                                       .toString();
      }
docs: 将字符串首字母大写
  
  @param s
  字符串
  @return 首字母大写后的新字符串