Java Stream Occurrences

Question

I have the list of following objects. Using Stream API, can I get a User with the number of frequency it appeared in the List?

public class User {
    string name;
    int age;
}

can see the list? and you want to match the user based on both params? and what do you mean by stream? — Danyal Sandeelo, Jan 01 '18 at 06:48
@DanyalSandeelo By steam I meant if I can get the solution using the java8 stream api. — pannu, Jan 01 '18 at 06:50

score 7 · Answer 1 · answered Jan 01 '18 at 06:50

7

You can use groupingBy combined with counting:

Map<String,Long> countByName =    
    users.stream()
         .collect(Collectors.groupingBy(User::getName,Collectors.counting()));

This gives you the the count for each User name.

answered Jan 01 '18 at 06:50

Eran

can we some how get the following results Map – pannu Jan 01 '18 at 07:11
@pannu What `User` would that be when there are multiple `User`s having the same name? You can produce a `Map>` of all the `User`s grouped by name. – Eran Jan 01 '18 at 07:13
Yeaah that would work thanks @Eran – pannu Jan 01 '18 at 07:18
@pannu Then just use `.collect(Collectors.groupingBy(User::getName));` – Eran Jan 01 '18 at 07:19

1 Answers1