stream 示例 - 点滴记忆*记忆点滴
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stream 示例

//分组,返回mapping
Collectors.groupingBy(AccountPayRecord::getMode, HashMap::new,
                                Collectors.mapping(AccountPayRecord::getTotalFee, Collectors.reducing(new Money(), (d1, d2) -> d1.add(d2)))));


//排序,拼接
installmentIdList.stream().map(id -> installmentMap.get(id))
                .sorted(Comparator.comparing(OrderInstallment::getLogicNumber))
                .map(in -> in.getLogicNumber() + "段").collect(Collectors.joining("、"));

    留下足迹