code: public static String toShortString(Throwable e, int stackLevel) {
          StackTraceElement[] traces = e.getStackTrace();
          StringBuilder sb = new StringBuilder(1024);
          sb.append(e.toString()).append("\t");
          if (traces != null) {
              for (int i = 0; i < traces.length; i++) {
                  if (i < stackLevel) {
                      sb.append("\tat ").append(traces[i]).append("\t");
                  } else {
                      break;
                  }
              }
          }
          return sb.toString();
      }
docs: 返回消息+简短堆栈信息（e.printStackTrace()的内容）
  
  @param e          Throwable
  @param stackLevel 堆栈层级
  @return 异常堆栈信息