16. self encapsulate field
17. Introduce Price Inheritence
18. modify setPriceCode() method
19. extract getChargeForPrice to prepare move getCharge() to Price
20. move getChargeForPrice() to Price, then remove the movie para and rename to getCharge
21. pull getCharge down to subclass
22. remove unnecessary case for each subclass
23. simple code
24. do same thing for getFrequentRenterPoints() method
Merge branch 'master' of github.com:agiledon/moviestore