Slightly deceiving error message on Collectors.toMap

[Michael Nascimento]

Hi folks,

For this very short test case:

Stream.of(1, 1).collect(toMap(identity(), Integer::reverse));

The following exception is produced:

java.lang.IllegalStateException: Duplicate key -2147483648
at java.util.stream.Collectors.lambda$throwingMerger$90(Collectors.java:133)

Obviously, the value being printed is not a key, but a value of the
map. Since capturing the actual key does not seem possible, I suggest
changing this message to something like:

Duplicate values for a key %s %s

And include both of them in the error message.

Should I file a bug for this?

Regards,
Michael