Java8的lambda用於操作集合非常好用,這裏記錄一些常用API
- 從實體集合中提取某字段:字符串類型、double類型、BigDecimal類型
//BigDecimal,提取並聚合
BigDecimal amount = orders.stream().map(JDOrder::getOrderFee).reduce(BigDecimal.ZERO,BigDecimal::add);
//String
List<String> voucherIds = voucherAssigns.stream().map(v -> v.getVoucherId()).collect(Collectors.toList());
List<String> giftIds = itemGifts.stream().map( ItemGifts::getGiftId).collect(Collectors.toList());
//double,提取並聚合
Double totalAmount = soldSums.stream().filter(s -> !ObjectUtils.isEmpty(s.getSum())).mapToDouble(s -> s.getSum()).sum();
//Integer
List<Integer> couponIds = itemCoupons.stream().map(i -> i.getCouponId()).collect(Collectors.toList());
- 根據某個字段過濾:可以是=、 >=
items = items.stream().filter(i -> i.getPrice()>=couponPrice).collect(Collectors.toList());
後續更新……