如何组合一个字段并将其他两个字段相加

Question

如何分组一个字段并将其他两个字段相加？ 工资类如下：

public class Salary {
  private Integer id;   
  private Double simSalary;
  private Double nonsimSalary;
}

数据如下：

id = 01, simSalary = 100, nonsimSalary = 0;
id = 01, simSalary = 0, nonsimSalary = 20;
id = 02, simSalary =50, nonsimSalary = 30;

我希望groupby为id并将simSalary和nonsimSalary相加，结果应该是这样的：

id = 01, simSalary = 100, nonsimSalary = 20;
id = 02, simSalary = 50, nonsimSalary = 30;

但是使用下面的代码，我只能求和一个字段，如何一次对这两个字段求和？

List<Salary> salaryList = getSalary();
salaryList.stream().collect(Collectors.groupingBy(Salary::getId,
            Collectors.summingDouble(Salary::getSimSalary))));