If I type "Coll", invoke completion and pick, say Collection, completion does automatically generate an import for me.
But if I do similar a line later, with an intent to make my collection immutable, I would usually do following:
1. Type "Co"<Ctrl+K> to get "Collection". Maybe try completion but this time only in-scope types would get displayed (as
Collection is already imported and matches).
2.Type the last letter and dot manually, so I have "Collections.|" and wait/invoke completion (all types are considered
this time as nothing in-scope matches).
3. pick unmodifiableCollection

I would expect that the completion would generate "import java.util.Collections" for me as it had to traverse that
(unknown) type for the match, but only the picked method gets expanded and I have to fix the code later using hints.