CIS 234: Project 1 Issues

1
CIS 234 Project 1 Issues

• Dr. Ralph D. Westfall
• April, 2010

2
What Is Feedback?

• comments and suggestions designed to help you
  improve your skills
• much of the information in this presentation
  should be relevant to Project 2
• What is feed-forward?

3
Specifications Are King

• always do projects based on what requirements say
• if disagree with requirements, discuss with
  client
• client may agree to change if she understands
  that what you want to do is better

4
General Requirements

• put statement that code is own work, AND that you
  have protected security of code at top, followed
  by S-signature
• only one zip file, only one Word file
• don't put zip files inside zip files
• .java files shouldnt be submitted as .txt
• Word and zip files must be named with last name
  before 1st name

5
Missing Parts

• many students didn't do the Excel file
• will be in Project 2 and will cost 5 points if
  missing
• UML diagram also missing in many projects
• not in Project 2, but may be in Project 3
• output missing in a few projects

6
Documentation in Code

• comment anything unusual or "tricky"
• don't need to comment very obvious things
• I look for comments on complicated things
• don't repeat comments for same thing
• avoid "wordy" comments
• incomplete sentences, bad grammar ok
• comments should relate to code
• get rid of "instructional" comments

7
Documentation in Code - 2

• use multiple line comment feature for long
  comments, and at start of program
• /
• /
• use line breaks to improve readability
• to separate self-contained blocks (similar to
  paragraphs in an essay)

8
Identifier Naming Convention

• variables, methods, classes and objects
• Class name starts with a capital letter
• all others have a lower case 1st letter, upper
  case for other words ("camel case"), as in
  iPhone, iPod, iMac, eBay (others?)
• capitalize initial letter of each added word in
  all identifiers e.g.,
• SpeechFormatter, joeThePlumber
• kangasPerYear, calcPrintResults()

9
Other Naming Issues

• use all capitals for constants
• use underscores (_) in constants, not in other
  identifiers
• use meaningful variable and object names
• shoesQuantity is better than shoes
• subtotal1 is NOT meaningful
• Class name needs to be same as its java filename
  (won't run if it isn't)

10
More Naming Issues

• capitalization is important ownerwages !
  ownerWages

11
Output Format

• include formatting required in specifications
  (can add if not specified but makes sense)
• title, line labels
• ---------- (underlining?)
• column alignment (s right justified)
• sub- and grand totals aligned appropriately
• spelling correct

12
Declarations

• declare all variables at the start of their
  methods
• don't bury declarations below among action
  statements
• use appropriate data types
• don't use integers for dollar amounts
• don't use double or float for quantities (e.g.,
  of items) or counts

13
Declarations - 2

• declare (and initialize) first, calculate later
• int shoesPerYear
• // other declarations
• // imperative ("action") code
• shoesPerYear yearDaysshoesPerDay

14
Declarations - 3

• whenever possible, declare objects first, then
  instantiate them later in imperative code
• Employee daBoss
• // other declarations
• // imperative ("action") code
• daBoss new Employee(Inputs.getBossWages)

15
Getters and Setters

• represent the implementation of the concept of
  encapsulation ("data hiding")
• purpose of a set (and often a constructor) is to
  allow another class to store a value in an object
• purpose of a get is to allow another class to
  read the value of a variable in an object

16
Get and Set

• a get should always return a value
• a set should always store a value
• usually don't have a return statement in a set
  method, except possibly when a boolean is
  returned to show it worked OK
• declare variables at top of class, not in their
  own set or get methods

17
All Data in Inputs.java File

• almost every data item used in StoreApplication.ja
  va needs to be declared in Inputs.java
• also need getter methods there to return each
  value to StoreApplication.java
• except could put
• private final int YEAR_MONTHS 12
  in StoreApplication.java

18
Calculations in StoreApplication.java

• Inputs.java file is designed to just be used for
  supplying data
• put calculations in StoreApplication.java file
  instead

19
Practice

• what is wrong with the following code?
• public void setNumber(int num)
• int number num
• what is the scope of number? (where is its value
  available?)

20
Access to Variables

• variables used by another class need to be
  (explicitly) private
• never read or change their values directly from
  outside, use get and set instead
• always access them directly inside class
• don't use class's own get or set methods inside
  the class

21
Access to Variables - 2

• private int number
• public void setNumber(int num)
• number num
• note that this set method directly writes values
  to this variable in its class
• other methods in this class can directly write
  values to this variable in its class also
• other classes must use its set method

22
Coding Issues

• don't "hard code" values in code that came from
  outside of your code or were calculated outside
  of your code
• use variables instead
• example multiply by a price variable instead of
  by the literal price
• shoesPerYear yearDaysshoesPerDay //OK
• shoesPerYear362shoesPerDay //not OK

23
Coding Issues - 2

• avoid "dead code"
• dead code is a method that is never called by
  another method in the project
• or code that is "commented out"
• ok if set or get are not called, because they may
  be used in future

24
Coding Issues - 3

• avoid unnecessary gets
• example a method may use a set method to store a
  value in an object
• don't have to then use a get method if already
  have this value in the class that called the set
  method

25
Coding Issues - 4

• mortgage payment calculations
• monthly payment must be annualized
• interest rate must be decimal, not percent (0.065
  rather than 6.50)

26
Coding Issues - 5

• recycle previously calculated values rather than
  repeating calculations
• kangaPerYear Inputs.getKangas()
  Inputs.getDaysPerYear
• kangaIncome kangaPerYear Inputs.getKangaPrice(
  )
• kangaCost kangaPerYear rather than
  repeating calculation

27
Coding Issues - 6

• dont do calculations in a println statement
• makes code hard to debug or update
• System.out.println("total " (totalIncome -
  totalExpenses))

28
Appendix

• following slides don't really apply to the
  Project 1 we used in this class

29
Constructor

• don't forget to include a constructor in a class
  that will be used to create objects
• use a constructor method to set individual values
  that the objects will have
• instead of initializing these values in
  declarations

30
Constructor - 2

• private int numHanboks 2
• // OK in a class just used for its variables,
  where other classes will use same values
• private double wages
• Employee(double wage)
• this.wages wages
• // use a constructor if will create objects

31
Access to Variables - 3

• storing calculated values in an object
• if a value changes, anything derived from it
  almost always should recalculate it
• example if a total is stored as a variable, it
  should change any time any variable that is part
  of the total changes
• a value's set method could call a calculate
  method to update values derived from the value

32
Coding Issues

• don't use too many methods
• if doing same thing often, make one generic
  method that can be used again
• e.g., calculating withholding for different
  salary levels
• should always make method private except if
  methods in other classes will use it

33
Coding Issues - 4

• if a data adjustment is only necessary in some
  situations, make adjustments in the code where
  the problem occurs (interface), not in a general
  class
• store good data in variables rather than fixing
  bad data in a get

34
Software Development Analyses

• an analysis is different from a plan
• need most detail on critical issues
• for calculations, need to indicate formulas
• for output, need to provide information on layout
• identify anything unusual
• less detail on minor issues
• long write-ups are not good in business