How to map from one container into another w/Java 8 streams?

Question

So, in Clojure, I can just say something like this...

(into [] (map some-function some-collection))

And I get a new vector of my transformed data.

Is there some simple equivalent of into for Java 8 streams? For example, I don't see a constructor on ArrayList that takes a stream, nor do I see some sort of helper function in java.util.Collections, nor the stream interface.

Never wrote Clojure, but it seems you just want `someCollection.stream().map(someFunction).collect(Collectors.toList())`? — Tunaki, Feb 18 '16 at 19:36
... which is hard to workout from the Javadoc alone, but there is a large number of examples and tutorials. — Peter Lawrey, Feb 18 '16 at 19:38

Andrea Bergia · Accepted Answer · 2016-02-18T19:42:40.870

You can do it using Collectors:

someCollection.stream()
              .map(someFunction)
              .collect(Collectors.toList());

You can do other cool stuff with Collectors, as explained in its javadoc:

 Map<Department, Integer> totalByDept =
     employees.stream()
              .collect(Collectors.groupingBy(Employee::getDepartment,
                                               Collectors.summingInt(Employee::getSalary)));

How to map from one container into another w/Java 8 streams?

1 Answers1