Reports construction of sorted collections, for example new TreeSet<>(), that rely on natural ordering, but their element type doesn't implement the Comparable interface. It's unlikely that such a collection will work properly.

A false positive is possible if the collection element is a non-comparable super-type, but it's intended to hold only comparable sub-types. This is however error-prone. It's better to narrow the collection element type or declare the super-type as Comparable.

The inspection also reports cases when the collection element is a type parameter which is not declared as extends Comparable. You can suppress the warnings on type parameters using the provided option (for example, to keep the API compatibility).

New in 2018.3