You did not initialize a container to perform the accumulation within. The reduce function basically does nothing, you should instead compute the total frequencies using an Object / Map.

Hi Xenophis, thanks for spending your time on this kata. I hope it will be a learnfull experience.

If you have your shape classes implemented (all with the correct area calculations) the aim is to implement a customized 'sort' on your classes by overriding the standard 'sort'. Example of 'sort' in C#: myShapeCollection.Sort(). In Java: Collections.sort(myShapeCollection).

Your customized 'sort' should be on area size. You can find on the internet how to override the default sort method on a collection in the language of preferrence.

I don't know JS, but don't forget to mark your comment next time as "spoiler" and put your code in a code block (between ```s) to make it more readable.

You can't compare strings in Java with == and !=. Use string1.equals(string2).