java.lang.NullPointerException: element cannot be mapped to a null key 報錯

 

 

這行代碼 getSupplierLoginId 可為空時會報這種錯誤

Map<String, List<PurchaseOrderEntity>> collect = purchaseOrderEntities.stream().collect(Collectors.groupingBy(PurchaseOrderEntity::getSupplierLoginId));

代碼修改后對空值進行過濾：

Map<String, List<PurchaseOrderEntity>> collect = purchaseOrderEntities.stream().filter(item-> StringUtil.isNotBlank(item.getSupplierLoginId())).collect(Collectors.groupingBy(PurchaseOrderEntity::getSupplierLoginId));