Before Java 6, files created by Derby would have the default
permissions of the operating system context. Under Unix, this would
depend on the effective umask of the process that started the Java VM.
In Java 6 and 7, there are methods available that allows tightening up this
(File.setReadable, setWritable), making it less likely that somebody
would accidentally run Derby with a too lenient default.
I suggest we take advantage of this, and let Derby by default (in Java
6 and higher) limit the visibility to the OS user that starts the VM,
e.g. on Unix this would be equivalent to running with umask 0077. More
secure by default is good, I think.
We could have a flag, e.g. "derby.storage.useDefaultFilePermissions"
that when set to true, would give the old behavior.