Filtering nested lists using lambda

Question

I am having a List<User> users. I would like to filter the list basing on two conditions.

Matching the UserID

Matching the FilterName

public class User implements Entity {

    public User() {
    }

    private String userName;
    private String userId;
    private List<Filter> filters;

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public List<Filter> getFilters() {
        return filters;
    }

    public void setFilters(List<Filter> filters) {
        this.filters = filters;
    }

}

Here is the method signature

List<User> users = getUsersList();
public List<User> query(String userID,String filterName){
    users.stream().filter(element -> element.getUserID().equals(userID) && element.getFilters().stream().filter(f -> f.getFilterName().equals(filterName))).collect(Collectors.toList());

}

The above method does not work as i am filtering basing on a element and a stream. Can anybody help me with the right way of filtering lists and nested lists.

I also tried this way

users.stream().filter(e -> e.getUserId().equals(predicate.getUserID())).collect(Collectors.toList()).stream().filter(f -> f.getFilters().stream().filter(fe -> fe.getName().equals(predicate.getFilterName()))).collect(Collectors.toList());

either ways i am getting the below error

Type mismatch: cannot convert from Stream to boolean

Tried Adiel Loingers suggestion. It worked

java.util.function.Predicate<Filter> con = e -> e.getName().equals(predicate.getFilterName());
            result = users.stream().filter(p -> p.getUserId().equals(predicate.getUserID()) && p.getFilters().stream().anyMatch(con)).collect(Collectors.toList());

If you want to check filterName present in the Filter List or not. You can simply change element.getFilters().stream().filter(f -> f.getFilterName().equals(filterName)) to element.getFilters().stream().filter(f -> f.filterName.equals(FilterName)).findAny().isPresent() — Sandeep Kokate
– Sandeep Kokate, Commented Nov 7, 2017 at 6:02

Naman · Accepted Answer · 2017-11-07 06:02:09Z

3

You shall change

element.getFilters().stream().filter(f -> f.getFilterName().equals(filterName))

to

element.getFilters().stream().anyMatch(f -> f.getFilterName().equals(filterName))

which would return boolean true for any match of the predicate specified which is same as specified in filter in your case.

answered Nov 7, 2017 at 6:02

Naman

32.7k32 gold badges240 silver badges385 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sandeep Kokate · Accepted Answer · 2017-11-07 06:04:16Z

1

I think it may help you, second conditions gets stream of all filters and find your filter name present in that filter is list, if so returns true otherwise false.

users.stream()
        .filter(element -> element.getUserId().equals(userId)
            && element.getFilters().stream().filter(f -> f.filterName.equals(FilterName)).findAny().isPresent())
        .collect(Collectors.toList());

answered Nov 7, 2017 at 6:04

Sandeep Kokate

8454 silver badges17 bronze badges

Collectives™ on Stack Overflow

Filtering nested lists using lambda

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related