Selenide combines 2 ElementsCollections - selenium

Question

I have 2 ElementsCollections namely oddTableRowItems and evenTableRowItems:
private static ElementsCollection oddTableRowItems() {
return $$(By.className("odd"));
}
private static ElementsCollection evenTableRowItems() {
return $$(By.className("even"));
}
I want to combine the 2 in order to only do a for loop once. It is row items, and only there classnames differ for styling purposes and I can only identify them through classnames.
This is how I tried to combine it - but it does not work:
ElementsCollection rowElements = evenTableRowItems();
rowElements.addAll(oddTableRowItems());
I get an:
java.lang.UnsupportedOperationException
does anybody how can I combine the 2 ElementsCollections?

Answer 1

The API could probably be a little bit more friendly here. But this way you can combine two ElementsCollection instances. The key here is WebElementsCollectionWrapper class.
ElementsCollection evenElements = $$(By.className("even"));
ElementsCollection oddElements = $$(By.className("odd"));
List<SelenideElement> elementsCombined = new ArrayList<>(evenElement);
elementsCombined.addAll(oddElements);
WebElementsCollectionWrapper wrapper = new WebElementsCollectionWrapper(elementsCombined);
ElementsCollection selenideCollectionCombined = new ElementsCollection(wrapper);

Answer 2

All add* methods throw UnsupportedOperationException by design. It's because ElementsCollections represents a collection of existing web elements on a web page; and page elements cannot be modified by test. That's why you cannot add or remove elements on the page.
The easiest way is to select all matching elements at once:
$$(".odd,.even").shouldHave(size(10));
A little bit longer way is to compose a new list containing both collections:
List<String> newList = new ArrayList<String>();
newList.addAll($$(".odd"));
newList.addAll($$(".even"));
but your goal seems to be doubtful for me. You will get the list with invalid order. Why can it be useful? Why would one need to iterate all elements? I cannot imagine a use case for that.

Answer 3

According to the API:
Note that this implementation throws an UnsupportedOperationException unless add(int, E) is overridden.

Answer 4

You can try this code. This is work fine!
ArrayList<SelenideElement> newList = new ArrayList<SelenideElement>();
newList.addAll(Selenide.$$(By.className("odd"));
newList.addAll(Selenide.$$(By.className("even"));