JDK-8304264 isn't quite right

It would be better to also have the debug check in the debug() method(s)
just in case call sites are missed. Because the boolean class member is
a `static final` the JIT should optimize the superfluous branch away.

Also, while we're at it, printing debug messages to `stdout` is a
terrible thing to do. The only reason I'm even writing this is that
those messages go to `stdout`. The chance of accidental writing to
`stdout` (which can cause problems for apps) should be zero.

This bug is reported at https://mail.openjdk.org/pipermail/security-dev/2023-April/035026.html.