1. public int preferential(String username) {
   
2.     //选中的订单清单
   
3.     List<OrderItem> orderItemList = findCartList(username).stream().
   
4.             filter(cart -> (boolean) cart.get("checked") == true).
   
5.             map(cart -> (OrderItem) cart.get("item")).collect(Collectors.toList());
   
6. 
   
7.     //聚合统计每种category的总价格,封装为map<categoryId,totalMoney>
   
8.     Map<Integer, IntSummaryStatistics> cartMap = orderItemList.stream().
   
9.             collect(Collectors.groupingBy(OrderItem::getCategoryId3,
   
10.                     Collectors.summarizingInt(OrderItem::getMoney)));
    
11. 
    
12.     //遍历每种category的优惠金额并累加
    
13.     int totalPreMoney = 0;
    
14.     for (Integer categoryId : cartMap.keySet()) {
    
15.         int preMoney = preferentialService.findPreMoneyByCategoryId(categoryId.longValue(),
    
16.                 (int) cartMap.get(categoryId).getSum());
    
17.         System.out.println("分类:"+categoryId+"...  "+"优惠:"+preMoney);
    
18.         totalPreMoney+=preMoney;
    
19.     }
    
20.     return totalPreMoney;
    
21. }

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1. public int preferential(String username) {
   
2.     //选中的订单清单
   
3.     List<OrderItem> orderItemList = findCartList(username).stream().
   
4.             filter(cart -> (boolean) cart.get("checked") == true).
   
5.             map(cart -> (OrderItem) cart.get("item")).collect(Collectors.toList());
   
6. 
   
7.     //聚合统计每种category的总价格,封装为map<categoryId,totalMoney>
   
8.     Map<Integer, IntSummaryStatistics> cartMap = orderItemList.stream().
   
9.             collect(Collectors.groupingBy(OrderItem::getCategoryId3,
   
10.                     Collectors.summarizingInt(OrderItem::getMoney)));
    
11. 
    
12.     //遍历每种category的优惠金额并累加
    
13.     int totalPreMoney = 0;
    
14.     for (Integer categoryId : cartMap.keySet()) {
    
15.         int preMoney = preferentialService.findPreMoneyByCategoryId(categoryId.longValue(),
    
16.                 (int) cartMap.get(categoryId).getSum());
    
17.         System.out.println("分类:"+categoryId+"...  "+"优惠:"+preMoney);
    
18.         totalPreMoney+=preMoney;
    
19.     }
    
20.     return totalPreMoney;
    
21. }

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