Object Oriented Programming (OOP) is of
paramount importance in the exam. How could it not be!? It's like asking what importance does the Pope place in the Catholic religion!!
Java is an OOP language from the ground up. I'll advance to you, that if you ever get an interview for a Java programmer position and you have no detailed knowledge about OOP, you won't last a second.
A lot of the questions in the exam deal with OOP
as they should.