Getting object from stream JAVA

Question

I am trying to find Friend by firstName and lastName using stream. Is it possible to return object from this stream? Like friend with that name and lastname? Because now return is mismatched.

@Override
public Friend findFriend(String firstName, String lastName) throws FriendNotFoundException { 
    if (firstName == null || lastName ==null) {
         throw new IllegalArgumentException("There is no parameters");
    }

           List<Friend> result = friends.stream()
            .filter(x -> (firstName.equals(x.getFirstName())) && 
            (lastName.equals(x.getLastName()))))
            .collect(Collectors.toList());

            return result;

Call findAny() or findFirst() instead of collect().

shmosel
– shmosel

2017-11-20 23:44:30 +00:00
Commented Nov 20, 2017 at 23:44 — shmosel
– shmosel, Commented Nov 20, 2017 at 23:44

Ousmane D. · Accepted Answer · 2017-11-20 23:55:30Z

2

utilize findFirst like so:

return friends.stream()
              .filter(x -> firstName.equals(x.getFirstName()) && 
                            lastName.equals(x.getLastName())
                     )
              .findFirst().orElse(null);

or return an Optional<Friend> i.e:

@Override
public Optional<Friend> findFriend(String firstName, String lastName) throws FriendNotFoundException { 
       if (firstName == null || lastName == null) {
          throw new IllegalArgumentException("There is no parameters");
       }

       return friends.stream()
              .filter(x -> firstName.equals(x.getFirstName()) && 
                            lastName.equals(x.getLastName())
                     )
              .findFirst();
}

which then means the method you're overriding must also be declared to return an Optional<Friend> and so forth up the inheritance hierarchy if needed.

edited Nov 20, 2017 at 23:55

answered Nov 20, 2017 at 23:47

Ousmane D.

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2 Comments

Malte Hartwig Over a year ago

Nice hint with the Optional. You might want to use findAny(), though. It might be more efficient for large streams.

Ousmane D. Over a year ago

@MalteHartwig true, I would recommend findAny when performing bulk operations with parallelStream as it's less constraining to use findAny in such case rather than to use findFirst.

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