Modify objects while iterating 2 Lists using java stream

Question

List<Account> list1 = new ArrayList<>();
List<Order> list2 = new ArrayList<>();

list1.stream().forEach(l1 -> list2.stream()
        .forEach(l2 -> {
            if (l1.getOrderId() == l2.getOrderId())
                l1.setStatus(l2.getStatus());
        }));

I was doing like this. It worked fine but now I have another situation where if orderId is not present in list2 set the status as "invalid" for that particular l1. OrderId is unique in both the tables. Hope this gives better understanding.

modifying objects while using Streams, in general, is not a good idea. — Naman
– Naman, Commented Feb 23, 2020 at 8:39

Anonymous · Accepted Answer · 2020-02-23 11:21:23Z

2

Edit Thanks for the edit of your question, it makes a lot more sense now. I think that this should do what you’re after:

    list1.forEach(acc -> acc.setStatus(list2.stream()
            .filter(o -> o.getOrderId() == acc.getOrderId())
            .findAny()
            .map(Order::getStatus)
            .orElse("invalid")));

I am using Iterable.forEach() and then Collection.stream() and Optional.map() for a functional way of calculating the status to be set.

edited Feb 23, 2020 at 11:21

answered Feb 23, 2020 at 9:29

Anonymous

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