code: public List<Request> removeTimeout() {
          synchronized (this) {
              List<Request> timeoutList = new ArrayList<>();
              Iterator<Request> iterator = reqQueue.iterator();
              while (iterator.hasNext()) {
                  Request request = iterator.next();
                  if (System.currentTimeMillis() - request.getReqReceivedTimeInMillis() > TIMEOUT_IN_MILLIS) {
                      timeoutList.add(request);
                      iterator.remove();
                  }
              }
              return timeoutList;
          }
      }
docs: 删除并返回超时未处理的request列表