I think I found 2 errors in the Master Exams of the K&B SCJP 6.0 book - 1. the explanation says that legal identifiers could only start with letters, "_" and the dollar sign. This is not true - it may be any kind of money sign - the book imho is correct here. In other words, you may also use the euro, pound, yen ... signs as the first letter of a legal java identifier.
2. "Is a Relationships always require 2 class types". What about an interface? An interface is not a class, I would say, yet e.g. "A String is an Object" I would say.