Read this chapter thoroughly. Maybe read it twice. You have already read chapters 4 and 5. Chapter 6 is going to introduce you to inheritance. More primary interview material.
Inheritance is spiffy and easy.
If you have trouble, be sure to ask on the Java College forum. You will want to understand it well now. You might want to try and do the exercises on page 169. You have already read chapter 7 up through page 182. Pick up again at page 183.