Check Foo.class.isInstance instead of Object.class.isInstance.
Check Foo.class.isInstance instead of Object.class.isInstance.

See
https://github.com/jspecify/jspecify/issues/164#issuecomment-775868055

I'm going to remove this sample entirely, but I'm first improving it in
this commit: If someone wants to keep a local copy, we might as well
make it as useful as we can.

jspecify/jspecify