java的lamda表达式求和问题遇到字符串类型如何解决

Question

@Data
public class MonthlyBudgetReportResponse {

    @ApiModelProperty(value = "数据类型(0-经营分类数据;1-总合计)")
    private String resultType;

    @ApiModelProperty(value = "品类名")
    private String catalogName;

    @ApiModelProperty(value = "收入预算本年")
    private String incomeBudgetBn;

    @ApiModelProperty(value = "收入预算本期")
    private String incomeBudgetBq;

    @ApiModelProperty(value = "收入本期完成数")
    private String incomeBudgetBqComplete;

    @ApiModelProperty(value = "毛利预算本年")
    private String profitBudgetBn;

    @ApiModelProperty(value = "毛利预算本期")
    private String profitBudgetBq;

    @ApiModelProperty(value = "毛利本期完成数")
    private String profitBudgetBqComplete;


}

这个是从数据库查询返回的实体类，现在我要实现对这个List的集合的收入以及毛利的汇总求和。数据库的实现想过，但是要多一条sql，而且原本sql已经很复杂了，不想再为一个单独求和再复制一遍。用java代码如何实现？有lamda表达式的最好。

//假设这和个是已经从数据库查出来的单条数据。有多条
List<MonthlyBudgetReportResponse> resultList

Answer 1

@Data
public class MonthlyBudgetReportResponse {

    @ApiModelProperty(value = "数据类型(0-经营分类数据;1-总合计)")
    private String resultType;

    @ApiModelProperty(value = "品类名")
    private String catalogName;

    @ApiModelProperty(value = "收入预算本年")
    private String incomeBudgetBn;

    @ApiModelProperty(value = "收入预算本期")
    private String incomeBudgetBq;

    @ApiModelProperty(value = "收入本期完成数")
    private String incomeBudgetBqComplete;

    @ApiModelProperty(value = "毛利预算本年")
    private String profitBudgetBn;

    @ApiModelProperty(value = "毛利预算本期")
    private String profitBudgetBq;

    @ApiModelProperty(value = "毛利本期完成数")
    private String profitBudgetBqComplete;

    public MonthlyBudgetReportResponse(String incomeBudgetBn, String profitBudgetBq) {
        this.incomeBudgetBq = incomeBudgetBn;
        this.profitBudgetBq = profitBudgetBq;
    }

    public static void main(String[] args) {
        List<MonthlyBudgetReportResponse> reportResponseList = new ArrayList<>();

        reportResponseList.add(new MonthlyBudgetReportResponse("11.1","15.1"));
        reportResponseList.add(new MonthlyBudgetReportResponse("12.3","13.2"));

        BigDecimal reduce = reportResponseList.stream().map( i -> new BigDecimal(i.getIncomeBudgetBq())).reduce(BigDecimal.ZERO, BigDecimal::add);
        System.out.println(reduce);
    }