Update MyZ.java

Fixes, in order:

* getFriends() returns a list of UUIDs, you were searching for a UUID casted to a string. Fixed

* Didn't go through SQL structure - maybe it should be comparing a name (String) of friends - but it definetly shouldn't compare a UUID to a String. Casted UUID to string.

* Same as first one

I'm short on time now, so I don't have time to look deeply into each of my pull requests - I'll do so later.