我的POJO定义如下:classEmployeeDetails{privateStringdeptName;privateDoublesalary;privateDoublebonus;...}目前，我有GroupBy'deptName'的lambda表达式:$set.stream().collect(Collectors.groupingBy(EmployeeDetails::getDeptName,Collectors.summingLong(EmployeeDetails::getSalary));问题是否可以对不止一列进行求和？我需要在一个表达式中而不是多次计算两个字段薪水和奖