Combine lists of 2 different objects into list of single object using Java 8 Stream API

Question

I have two lists as below:

List ids = Arrays.asList(1,2,3); List reps = Arrays.asList("abc","pqr","xyz");

Now I want to create list of Prediction objects with values mapped from above two lists in sequence like below:

List results = [ Prediction(1,"abc") , Prediction(2,"pqr"), Prediction(3,"xyz") ]

class Prediction {
    int id;
    String rep;
}

How this can be done using Java8 Stream API.

Can you share your code-attempt, and also describe the issue that you've faced. — Alexander Ivanchenko, Jun 16 '22 at 19:01
Does this answer your question? [How to zip two Java Lists](https://stackoverflow.com/questions/31963297/how-to-zip-two-java-lists) — Jacob van Lingen, Jun 17 '22 at 08:02
How about writing `List results = Arrays.asList(new Prediction(1,"abc") , new Prediction(2,"pqr"), new Prediction(3,"xyz"));` in the first place? — Holger, Jun 17 '22 at 08:27

Jacob van Lingen · Accepted Answer · 2022-06-17T08:01:43.017

1

The operation you described is called zipping.

If you are sure the lists are evenly of length, you could do something like:

IntStream.range(0, ids.size())
    .mapToObj(i -> new Prediction(ids.get(i), reps.get(i)))
    .toList()

Assuming the Prediction class has a constructor like that...

edited Jun 17 '22 at 08:01

answered Jun 17 '22 at 07:11

Jacob van Lingen

1 Answers1