http://www.howtogeek.com/210907/minecraft-doesnt-need-java-installed-anymore-its-time-to-remove-it/
One of the big complaints Minecraft players have is that Minecraft runs on Java — it’s a pain to deal with because it’s insecure and needs frequent updating to avoid exploits, and they’d rather not deal with it at all. Thanks to a new launcher, Minecraft no longer requires you to install Java, so you can finally remove it.
The short version is that Minecraft is now bundling a standalone version of Java into their installation and it doesn’t have the security problems and annoyances that regular Java does.