如何过滤列表< String，Object>用Java流收集吗? [英] How to Filter List<String,Object> Collection with java stream?

问题描述

我有

List<String, Person> generalList

作为列表.在人员"下有一个客户"对象，在客户"下还有1个名为ID的列表

as a list. there is Customer object Under Person, 1 more list under Customer named Id

我想在对象下过滤此嵌套的IdList，但它不起作用.

I want to filter this nested IdList under object but it is not working.

我尝试使用flatMap，但是此代码无法正常工作

I tried to use flatMap but this code is not working

String s = generalList.stream()
.flatMap(a -> a.getCustomer().getIdList().stream())
.filter(b -> b.getValue().equals("1"))
.findFirst()
.orElse(null);

我希望输出为字符串或客户对象

I expect the output as String or Customer object

我原来的容器是地图，我正在过滤地图到列表"

My original container is a map, I am filtering Map to List

说明.

Map<String, List<Person> container;

List<Person> list = container.get("A");

String s = list.stream()
.flatMap(a -> a.getCustomer().getIdList().stream())
.filter(b -> b.getValue().equals("1"))
.findFirst()
.orElse(null);

这里是人

public class Person
{
private Customer customer;

public Customer getCustomer ()
{
    return customer;
}
}

和客户

public class Customer {
private Id[] idList;
/*getter setter*/
}

和ID

public class Id {
private String value;
/*getter setter*/
}

推荐答案

您可能正在寻找 map 操作，如下所示:

You're possibly looking for a map operation as:

String s = list.stream()
        .flatMap(a -> a.getCustomer().getIdList().stream())
        .filter(b -> b.getValue().equals("1"))
        .findFirst()
        .map(Id::getValue) // map to the value of filtered Id
        .orElse(null);

等同于(为澄清起见)

String valueToMatch = "1";
String s = list.stream()
        .flatMap(a -> a.getCustomer().getIdList().stream())
        .anyMatch(b -> b.getValue().equals(valueToMatch))
        ? valueToMatch : null;

这篇关于如何过滤列表< String，Object>用Java流收集吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！