Java Stream API - Which is more effective for list transformation: map or forEach?

Other Questions API
1

I have a list named inputList from which I want to filter elements, apply a specific function to each one, and store the results in another list called outputList. Utilizing the Stream API introduced in Java 8, I’ve come across two methods to accomplish this. I am interested in determining which method is superior and the reasoning behind it.

Approach 1:

outputList = new ArrayList<>();
inputList.stream()
        .filter(item -> item != null)
        .forEach(item -> outputList.add(applyFunction(item)));

Approach 2:

outputList = inputList.stream()
        .filter(item -> item != null)
        .map(item -> applyFunction(item))
        .collect(Collectors.toList());

I’m also open to suggestions for a potential third method.

2

hey, the thing about stream map is it’s designed for transformations, so it preserves immutability and creates a new list without side-effects, which makes code clearer. foreach can mutate existing lists but it’s often discouraged for transformations due to less readability n possibly thread safety issues. so map is typically preferable here.