Java 8: Stream a list and map to another list based on different filters

Question

I have the following code:

public boolean foo(List<JSONObject> source, String bar, String baz) {
    List<String> myList = newArrayList();

    source.forEach(json -> {
        if (!(json.get(bar) instanceof JSONObject)) {
            myList.add(json.get(bar).toString());
        } else {
            myList.add(json.getJSONObject(attribute).get("key").toString());
        }
    });

    /**
     * do something with myList and baz
     */
}

I'm just wondering if there's a way to do the if-else condition inline using a filter.

Something along the lines of:

List<String> myList = source.stream()
                .filter(json -> !(json.get(bar) instanceof JSONObject))
                .map(item -> item.get(attribute).toString())
                .collect(Collectors.toList());

If I go by the approach above, I will miss the supposed to be "else" condition. How can I achieve what I want using a more java-8 way?

Thanks in advance!

Answer 1

The only way I see is putting the condition in the map call. If you use filter you lose the "else" part.

List<String> myList = source.stream()
            .map(item -> {
                  if (!(item.get(bar) instanceof JSONObject)) {
                      return item.get(bar).toString();
                  } else {
                      return item.getJSONObject(attribute).get("key").toString();
                  }
            })
            .collect(Collectors.toList());

or, as Holger suggested in a comment, use the ternary conditional operator:

List<String> myList = source.stream()
            .map(i -> (i.get(bar) instanceof JSONObject ? i.getJSONObject(attribute).get("key") : i.get(bar)).toString())
            .collect(Collectors.toList());