Class J RF Power Amplifier
No, class J has a single transistor, just as class B amplifier + crazy RF magic to increase efficiency. This paper is pretty clear about it:


  A class-J amplifier is biased as a conventional “deep” class-AB PA
  that will be considered hereafter in the analytical development as
  class-B. Thus, a class-J PA demonstrates very similar drain current
  waveform to its class-B counterpart.


Integrated Design of a Class-J Power Amplifier by S Rezaei

This paper also contains schematics, if you are curious.