Short way to create sub-list in java

Question

Is there a shorter way to create sublist from other list? For example: I have a Contact obiect, this obiect contain String field of adres

public List<String> getAdreses(long personID) {
        List<String> adreses=null;
        for(Contact mail : getContacts(personID)){
            adreses.add(mail.getMail());
        }
        return adreses;
    }

Possible duplicate of How to transform List<X> to another List<Y> — Oleg Estekhin
– Oleg Estekhin, Commented Apr 3, 2018 at 10:20
@smoke, your code will not run as it is... You have initialized adreses list like... List<String>adreses = null; and later you are adding element to it like: adreses.add(mail.getMail()); But as you have not initialized adreses like: List<String> adreses=new ArrayList<>(); It will throw NullPointerException... — Harsh Mehta
– Harsh Mehta, Commented Apr 3, 2018 at 10:20

chengpohi · Accepted Answer · 2018-04-03 10:18:43Z

4

Try Java Stream:

List<String> adreses = getContacts(personID).stream().map(Contact::getMail).collect(Collectors.toList())

answered Apr 3, 2018 at 10:18

chengpohi

14.2k1 gold badge28 silver badges43 bronze badges

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

2 Comments

smok Over a year ago

ok, but how can i set value? in this: .map(Contact::getMail)

chengpohi Over a year ago

@smok, .map(Contact::getMail) is equal to .map(contact -> contact.getMail()) and it will collect the mails to List, you don't need to set value.

Collectives™ on Stack Overflow

Short way to create sub-list in java

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related