Slightly deceiving error message on Collectors.toMap

Michael Nascimento misterm at
Wed Apr 16 20:18:53 UTC 2014

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

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?


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