An input byte like 0xf0 should be rejected via MALFORMED[1]
for ISO-2022 style decoders.
Instead, it is converted into the nonsense character \ufff0 by being cast to char.
Passthru for invalid characters is an interesting violation of the ISO-2022 standard,
but in this case it should be converted to \u00f0.

 $ for cs in ISO-2022-KR ISO-2022-CN ISO-2022-CN-GB ISO-2022-CN-CNS; do printf "%s %s\n" $cs `jver /net/cremina/export/sherman/ws/rc java Decode $cs f0`; done
ISO-2022-KR \ufff0
ISO-2022-CN \ufff0
ISO-2022-CN-GB \ufff0
ISO-2022-CN-CNS \ufff0