CODEWITHSUNDEEP
javajava-8java-stream
JavaDev
JavaDev

Reputation: 29

How can this code be improved with java streams

I have a requirement to find if there are any Users over the age of 18 in the given list. If there is no user over age 18, the method should return -1. Otherwise, it should return the age of the youngest user.

While using the streams, I created the following method, however, the stream is used twice. Is there a better way to do this with streams

public int test(List<User> userList) {
    List<User> usersOver18 = userList.stream()
            .filter(emp -> emp.getAge() > 18)
            .collect(Collectors.toList());

    if (usersOver18.isEmpty()) {
        return -1;
    }
    return usersOver18.stream()
            .min(Comparator.comparing(User::getAge))
            .get().getAge();
}

Upvotes: 1

Views: 146

Answers (2)

erickson
erickson

Reputation: 269667

You can map to the age, filter out anything 18 or under, and then return the minimum or -1 if the stream is empty:

public int test(List<User> userList) {
    return userList.stream()
        .mapToInt(User::getAge)
        .filter(age -> age > 18)
        .min().orElse(-1);
}

Note that after mapToInt(), you are working with an IntStream and not Stream<Integer>, and min() returns OptionalInt, not Optional<Integer>.

By the way, are you sure the age filter is not >= 18?

Upvotes: 10

Jamie Bisotti
Jamie Bisotti

Reputation: 2685

I'm doing this from memory on my phone so it might not be perfect, but...

return userList
    .stream()
    .filter(u -> u.getAge() > 18)
    .min(Comparator.comparing(User::getAge))
    .map(User::getAge)
    .orElse(-1);

Upvotes: 3

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