Nested lists with streams in Java8

Question

I have a list of objects A. Each object A in this list contains list of object B and the object B contains list of Object C. The object C contains an attribute name that i w

Answer 1

You can do it with flatMap.

I made an example with Company which contains a list of Person :

public static void main(String[] args) {
    List companies = Arrays.asList(
            new Company(Arrays.asList(new Person("Jon Skeet"), new Person("Linus Torvalds"))),
            new Company(Arrays.asList(new Person("Dennis Ritchie"), new Person("Bjarne Stroustrup"))),
            new Company(Arrays.asList(new Person("James Gosling"), new Person("Patrick Naughton")))
    );

    List persons = companies.stream()
            .flatMap(company -> company.getPersons().stream())
            .map(Person::getName)
            .collect(Collectors.toList());

    System.out.println(persons);
}

Output :

[Jon Skeet, Linus Torvalds, Dennis Ritchie, Bjarne Stroustrup, James Gosling, Patrick Naughton]