code: public static String safeSubString(String text, int start, int end) {
          if (text == null || text.length() == 0) {
              return text;
          }
          if (start < 0 || end < 0 || end <= start) {
  //            throw new IllegalArgumentException(String.format("illegal argument: start: %1$s, end: %2$s", start, end));
              return text;
          }
          int len = end - start;
          if (text.length() <= len) {
              return text;
          }
          return text.substring(start, end);
      }
docs: 截取子串函数（不抛出异常）