希望有人能帮助我。我有一个具有以下结构的POJO:
public class Invoice{
private String docNum;
private String customer;
private ArrayList<InvoiceDetails> invoiceDetails;
/* Getters and setters*/
}
还有一个POJO具有以下内容:
public class InvoiceDetails{
private String vatGroup;
private Double vatAmount;
private Double amount;
/* Getters and setters*/
}
除此之外,我还有第三个,其内容如下。
public class VatType{
private String vatGroup;
private Double vatAmount;
private Double amount;
/* Getters and setters*/
}
我要做的是将一个
发票(Invoice)
的List
按照VAT组进行分组,输出一个VAT类型(VatType)
的List
。就像在SQL
中的DISTINCT
语句一样。
比如我有以下的List:InvoiceDetails idA1 = new InvoiceDetails("S1", 100.0, 40.0);
InvoiceDetails idA2 = new InvoiceDetails("S2", 140.0, 40.0);
InvoiceDetails idA3 = new InvoiceDetails("A1", 50.0, 10.0);
ArrayList<InvoiceDetails> listA = new ArrayList<>();
listA.add(idA1);
listA.add(idA2);
listA.add(idA3);
Invoice invoiceA = new Invoice();
invoiceA.setDetailList(listA);
InvoiceDetails idB1 = new InvoiceDetails("S1", 200.0, 50.0);
InvoiceDetails idB2 = new InvoiceDetails("S2", 240.0, 50.0);
InvoiceDetails idB2 = new InvoiceDetails("A1", 100.0, 20.0);
ArrayList<InvoiceDetails> listB = new ArrayList<>();
listB.add(idB1);
listB.add(idB2);
listB.add(idB3);
Invoice invoiceB = new Invoice();
invoiceB.setDetailList(listB);
List<Invoice> invoiceList = new ArrayList<>();
invoiceList.add(invoiceA);
invoiceList.add(invoiceB);
预期结果应该是一个
List
,其中包含以下项目:VatType
。("S1",300.0,90.0)
("S2",380.0,90.0)
("A1",150.0,30.0)
如何使用一个stream
一次性获取此列表。避免通过Lists
进行迭代?提前致谢。