When working with a Stream<String>,
which of these types can be returned from the collect() terminal operator by passing arguments to Collectors.groupingBy()?
C.
The groupingBy() collector always returns a Map, so III can't be right.
The other two are definitely possible.
To get I, you can group using a Function that returns an Integer such as s.collect(Collectors.groupingBy(String::length)).
To get II, you need to group using a Function that returns a Boolean and specify the type,
such as s.collect(Collectors.groupingBy(String::isEmpty,Collectors.toSet())).
The autoboxing is used for both.
Option C is correct.