private void checkGoodsStock(Goods goods, Integer buyNum) { //商品为现货商品，判断商品现货可用库存 if (GoodsSaleType.SPOT == GoodsSaleType.findSaleType(goods.getSaleType())) { //单个商品、意向商品 if (GoodsShelveType.SINGLE.getShelveType() == goods.getShelveType() || GoodsShelveType.INTENTION.getShelveType() == goods.getShelveType()) { BaseGoods baseGoods = iBaseGoodsService.getOne(Wrappers.<BaseGoods>lambdaQuery().in(BaseGoods::getModel, goods.getModel()).last("for update")); if (buyNum > baseGoods.getSpotOccupyStock()) { throw new ServiceException(ErrorMessage.STOCK_ERROR); } } //组合商品 if (GoodsShelveType.COMBINATION.getShelveType() == goods.getShelveType()) { //查询组合商品子商品信息 List<GoodsChilds> goodsChildsList = goodsChildsService.lambdaQuery().eq(GoodsChilds::getParentId, goods.getId()).eq(GoodsChilds::getIsGift, 0).list(); if (CollectionUtils.isEmpty(goodsChildsList)) { throw new ServiceException("组合商品子商品信息为空"); } //子商品所有商品型号 List<String> goodsChildsModelList = goodsChildsList.stream().map(GoodsChilds::getModel).collect(Collectors.toList()); List<BaseGoods> baseGoodsList = iBaseGoodsService.list(Wrappers.<BaseGoods>lambdaQuery().in(BaseGoods::getModel, goodsChildsModelList).last("for update")); Map<String, BaseGoods> baseGoodsMap = AppUtils.listToMap(baseGoodsList, BaseGoods::getModel); for (GoodsChilds goodsChilds : goodsChildsList) { BaseGoods baseGoods = baseGoodsMap.get(goodsChilds.getModel()); if (baseGoods == null) { throw new ServiceException("商品型号不存在"); } //子商品总购买数 Integer goodsChildsBuyNum = goodsChilds.getNumberCoefficient().multiply(new BigDecimal(buyNum)).intValue(); if (goodsChildsBuyNum > baseGoods.getSpotOccupyStock()) { throw new ServiceException(ErrorMessage.STOCK_ERROR); } } } } //非现货商品，判断上架库存 if (GoodsSaleType.SPOT != GoodsSaleType.findSaleType(goods.getSaleType()) && buyNum > goods.getStock()) { throw new ServiceException(ErrorMessage.STOCK_ERROR); } }优化该段代码

这段代码可以进行以下优化：

1. 将数据查询和判断库存的逻辑分离，可以提高代码的可读性和可维护性。

2. 对于组合商品的处理，可以使用批量查询替代循环查询。同时，可以将子商品总购买数的计算提取出来，避免重复计算。

3. 可以通过使用缓存来提高查询性能，避免每次都查询数据库。

综上所述，可以进行如下优化：

private void checkGoodsStock(Goods goods, Integer buyNum) {
    //商品为现货商品，判断商品现货可用库存
    if (GoodsSaleType.SPOT == GoodsSaleType.findSaleType(goods.getSaleType())) {
        //单个商品、意向商品
        if (GoodsShelveType.SINGLE.getShelveType() == goods.getShelveType() || GoodsShelveType.INTENTION.getShelveType() == goods.getShelveType()) {
            BaseGoods baseGoods = iBaseGoodsService.getOne(Wrappers.<BaseGoods>lambdaQuery().eq(BaseGoods::getModel, goods.getModel()).last("for update"));
            int availableStock = baseGoods.getSpotOccupyStock();
            if (buyNum > availableStock) {
                throw new ServiceException(ErrorMessage.STOCK_ERROR);
            }
        }
        //组合商品
        else if (GoodsShelveType.COMBINATION.getShelveType() == goods.getShelveType()) {
            //查询组合商品子商品信息
            List<GoodsChilds> goodsChildsList = goodsChildsService.lambdaQuery().eq(GoodsChilds::getParentId, goods.getId()).eq(GoodsChilds::getIsGift, 0).list();
            if (CollectionUtils.isEmpty(goodsChildsList)) {
                throw new ServiceException("组合商品子商品信息为空");
            }
            //子商品所有商品型号
            List<String> goodsChildsModelList = goodsChildsList.stream().map(GoodsChilds::getModel).collect(Collectors.toList());
            //批量查询子商品库存
            List<BaseGoods> baseGoodsList = iBaseGoodsService.list(Wrappers.<BaseGoods>lambdaQuery().in(BaseGoods::getModel, goodsChildsModelList).last("for update"));
            //使用Map存储子商品库存信息，避免重复查询
            Map<String, BaseGoods> baseGoodsMap = baseGoodsList.stream().collect(Collectors.toMap(BaseGoods::getModel, Function.identity()));
            for (GoodsChilds goodsChilds : goodsChildsList) {
                BaseGoods baseGoods = baseGoodsMap.get(goodsChilds.getModel());
                if (baseGoods == null) {
                    throw new ServiceException("商品型号不存在");
                }
                //计算子商品总购买数
                int goodsChildsBuyNum = goodsChilds.getNumberCoefficient().multiply(new BigDecimal(buyNum)).intValue();
                int availableStock = baseGoods.getSpotOccupyStock();
                if (goodsChildsBuyNum > availableStock) {
                    throw new ServiceException(ErrorMessage.STOCK_ERROR);
                }
            }
        }
    }
    //非现货商品，判断上架库存
    else if (buyNum > goods.getStock()) {
        throw new ServiceException(ErrorMessage.STOCK_ERROR);
    }
}

以上代码中，我将查询库存信息和计算可用库存的逻辑分离，使用批量查询和Map来提高查询性能，同时提取子商品总购买数的计算，避免重复计算。