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.