code: public void copy(String fromBucket, String fromFileKey, String toBucket, String toFileKey)
              throws QiniuException {
          Response res = copy(fromBucket, fromFileKey, toBucket, toFileKey, false);
          if (!res.isOK()) {
              throw new QiniuException(res);
          }
          res.close();
      }
docs: 复制文件，要求空间在同一账号下
  
  @param fromBucket  源空间名称
  @param fromFileKey 源文件名称
  @param toBucket    目的空间名称
  @param toFileKey   目的文件名称
  @throws QiniuException