jdk8之stream求和，保留兩位小數

統計介面，最下面加 總計 一行時

public List<GateBaseBResultStatis> gateBaseBResultStatisTotal(List<GateBaseBResultStatis> list){
        GateBaseBResultStatis model = new GateBaseBResultStatis();
        model.setAddvcd("總計");

        model.setTotalCount(list.stream().map(GateBaseBResultStatis :: getTotalCount).reduce(BigDecimal.ZERO, BigDecimal :: add).setScale(2, BigDecimal.ROUND_HALF_UP));
        model.setGateNumberCount(list.stream().map(GateBaseBResultStatis :: getGateNumberCount).reduce(BigDecimal.ZERO, BigDecimal :: add).setScale(2, BigDecimal.ROUND_HALF_UP));
        model.setGateNumberRate(model.getGateNumberCount().divide(model.getTotalCount(), 2, BigDecimal.ROUND_HALF_UP).multiply(new BigDecimal("100")) + "%");
        list.add(model);

        return list;
    }

需要注意，屬性也要用BigDecimal 修飾，否則 BigDecimal :: add 不能用

//總計
private BigDecimal totalCount;