如何筛选清单 <String,Object> 用Java流收集吗？

Question

I have

List<String, Person> generalList

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

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

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);

I expect the output as String or Customer object

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

Explanation.

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);

Here is the Person

public class Person
{
private Customer customer;

public Customer getCustomer ()
{
    return customer;
}
}

And Customer

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

And Id

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

Answer 1

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);

which is equivalent of(just to clarify)

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

Answer 2

Update 2 This solution works directly on a list of Person objects:

String key = "1";
List<Person> list = container.get("A");
String filteredValue = list.stream()
    .flatMap(person -> Arrays.stream(person.getCustomer().getId())
    .filter(id -> id.getValue().equals(key)))
    .findFirst().get().getValue();

---

Old answer working with map Since you are only interested in the values of your map you should stream on them and in the flatMap I not only got a stream on the getId() list but also filtered on them directly. So if I understood your code structure correctly this should work

String key = "1";

 String filteredValue =  map.values().stream()
     .flatMap(list -> list.stream()
     .flatMap(person -> Arrays.stream(person.getCustomer().getId())
     .filter(id -> id.getValue().equals("1"))))
     .findFirst().get().getValue();

Updated to adjust for edited question