code: public Boolean closeOrder(String outTradeNo){
          checkNotNullAndEmpty(outTradeNo, "outTradeNo");
          Map<String, String> closeParams = new TreeMap<>();
          put(closeParams, WepayField.OUT_TRADE_NO, outTradeNo);
          buildCloseParams(closeParams);
          return doPost(ORDER_CLOSE, closeParams) != null;
      }
docs: 关闭订单
  @param outTradeNo 商户订单号
  @return 关闭成功返回true，或抛WepayException