计算一个List对象中某个字段总和
求和字段属性为Integer时
Integer tTotal=list.stream().collect(Collectors.summingInt(TransportInfo::getContainerUse));
求和字段属性为BigDecimal时
BigDecimal totalCost = v.stream().map(AnalysisIncomeYearVo::getReturnYear).reduce(BigDecimal.ZERO, BigDecimal::add);
求和字段属性为Double时
double sumChildAmountResult = sumAmountResult.stream().mapToDouble(Double::doubleValue).sum();