code: public void setSuccess(V result) {
          if (this.isCancelled()) {
              this.releaseIfNeed(result);
          }
          if (setSuccess0(result)) {
              notifyListeners();
              return;
          }
          throw new IllegalStateException("complete already: " + this);
      }
docs: 设置正常返回结果
  
  @param result 正常返回值