Block or allow websites with "/etc/hosts" is really deprecated? What to use instead?

I'm creating a Java project for my university and one of the features of my project is to block / allow websites that was set by the teacher (it's an open-source laboratory monitoring software). Actually I need something easier: block ALL sites but allow only a few (allow about 2 or 3 sites, all the others must be blocked).

I've found this excellent tutorial that uses /etc/hosts.allow and /etc/hosts.deny to do exactly what I need. However I discovered that these files and this method of blocking / allowing websites is deprecated.

I don't think IPTables is a good way to achieve my aim, because to allow the access to a single website I need allow an IP address - but remember that a single hostname can have several IP addresses (like any Google service, Facebook and even Moodle of my university).

So, what would be the best way to block all websites and allow only a few?