一、背景
二、实现
double componentTotalWeight = componentMapper.selectList(componentQuery).stream().map(i -> Double.parseDouble(i.getTotalWeightCustomer())).reduce(Double::sum).get();
double componentTotalWeight = componentMapper.selectList(componentQuery).stream().map(i -> Double.parseDouble(i.getTotalWeightCustomer())).reduce(Double::sum).get();