Object-Oriented Programming in Java (OOP Concepts)

Given:

class CardBoard {
   Short story = 200;

   CardBoard go(CardBoard cb) {
       cb = null;
       return cb;
   }

   public static void main(String[] args) {
       CardBoard c1 = new CardBoard();
       CardBoard c2 = new CardBoard();
       CardBoard c3 = c1.go(c2);
       c1 = null;
       // do Stuff
   } 
}

When // doStuff is reached, how many objects are eligible for GC?