CSC 171
Homework 8

Assigned Apr 26, due May 8

This assignment will involve the material of HtDCH chapters 16-19 (abstract classes and refactoring, designing hierarchies of classes, access specifiers, overloading, local variables, assignment and mutation, sequence, void methods), as well as some material given out in class on arrays and loops.

CodeLab

Do as many problems as you can from the "Beginning Language", "Intermediate Language", and "Advanced Language" sections.

Essay

Re-read the Web page on Adages of Software Engineering. Choose one (or several closely-related) adages, or one longer article, that mean more to you than they did in January. Write an essay of one or more well-structured paragraphs: what does the adage really mean in practice? Do you agree or disagree? Support your claims with specific examples from your own programming experience.

Programming

For all the programming assignments, be sure to follow the design recipe; here are some practical suggestions on how to do that in Java.

As in Scheme, be sure to choose meaningful names for functions and parameters, and watch for opportunities to re-use functions you, I, or the textbook have already written.

Write and test each method before going on to the next one; in some cases, the next one depends on the previous one.

Also turn in a log of how many errors of different kinds you encountered in the assignment, with brief comments describing each one ("mismatched parentheses" is self-explanatory, but more complex errors might need more description). You may do this using the PSP forms, or simply by keeping track in a text file or on paper and turning it in.

1. Modify your HotelRoom and ConsRoomList classes from homework 7 by making all the fields private and adding "getter" methods for them. This may require changing some test cases to use the getters rather than the field names. I recommend also changing your same method to use getters rather than field names, even though it's in the same class and it could use the field names.

2. Add a method raisePriceMutating to the HotelRoom class which takes in an int (how many cents to raise the price), and increases the price of the HotelRoom by that much. It should return nothing at all.

3. Define a class RoomArray which stores a bunch of HotelRooms in a single field of type HotelRoom[]. Write several examples of RoomArrays.

4. Write a method countRooms for the RoomArray class which tells how many hotel rooms are in the RoomArray.

5. Add a method anyOK for the RoomArray class which takes in a number of people and a boolean indicating whether they want smoking or non-smoking, and tells whether there is an ok room anywhere in the list. Use an auxiliary method that does recursion on natural numbers.

6. Add a method countOK for the RoomArray class which takes in a number of people and a boolean indicating whether they want smoking or non-smoking, and tells how many room in the list are OK. Again, use an N-recursive auxiliary method.

7. Add a method named same which takes in another RoomArray and tells whether it is the same as this one. Use an N-recursive auxiliary method.

8. Add a method raisePricesMutating for the RoomArray class which takes in a number of cents, mutates the rooms in the array to raise their prices, and returns nothing. Use an N-recursive auxiliary method which returns nothing.

9. Add a method cheapest for the RoomArray class which returns the lowest-priced room in a given list. Note that this doesn't make sense for an empty list of rooms; in that case, have it return the special value null (a predefined constant, to which you can refer the same way you refer to true or false).

   Hint: write an auxiliary method cheapestWithBackup which takes in a HotelRoom and works on any RoomArray: it pretends the given room were part of the list, and returns the cheapest room in this larger list. It may also help to write another auxiliary method chooseCheaper which chooses the cheaper between two HotelRooms. You may need yet another helper function doing recursion on natural numbers, or you can add a natural-number parameter to cheapestWithBackup and have it do the recursion itself.

10. Define another class LoopRoomArray which also stores a bunch of HotelRooms in an array, but implements all the same methods (anyOK, countOK, same, raisePricesMutating, cheapest) with while-loops or for-loops rather than recursion.

    Hint: It has a lot in common with RoomArray; see how much you can refactor.

Grading standards

Error log:       /25
(I'm not grading on how many or how few errors you encountered, only on whether you recorded them adequately.)

General skills:

Total:         /500