This inspection helps to convert unmodifiable collections created before Java 9 to new collection factory methods like List.of or Set.of. Also since Java 10 the conversion to List.copyOf, etc. could be suggested.

Note that Java 9 collection factory methods do not accept null values. Also, set elements and map keys are required to be different. It's not always possible to statically check whether original elements are different and not null. Using the checkbox you may enforce the inspection to warn only if original elements are compile-time constants.

Also it should be noted that some query methods like Collection.contains() or Map.get don't tolerate nulls as well. E.g., Collection.contains() throws a NullPointerException instead of returning false. Thus, even if the collection is initialized with non-null values only, the semantics of the code may change after migration.

This inspection is available since Java 9 only.

New in 2017.2