Order maintained when creating map from list and then creating list using Java Streams

Question

Using Java streams, we have a list of items, and for each item we want to calculate some value and then return a list of these values, using the original order. Will the following code always preserve the ordering? After all, a map is not an ordered data structure.

List<Item> list;
list.stream()
  .map(item -> calculateValue(item))
  .toList();
...
private double calculateValue(Item item) {
...
}

Answer 1

The map() intermediate Stream operation does not produce a Map instance. It just applies the Function you pass to it on each element of the Stream. Therefore, the order of the elements of the original List will be preserved in the output List.