underscore in java package name

[jam01]

According to https://docs.oracle.com/javase/tutorial/java/package/namingpkgs.html underscores can be expected in package names. The JAVAPKG style first line pattern does not include underscore and so the license is not applied properly.

Suggesting changing
"^package [a-z]+(\\.[a-z][a-z0-9]*)*;$" to "^package [a-z_]+(\\.[a-z_][a-z0-9_]*)*;$"
I can propose a PR, just wanted to make sure the general idea was agreed upon :)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.