The Programming Discipline

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The Programming Discipline
Revisited with Java examples

• Professor Stephen K. Kwan

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• The Programming Project
• Problem statement create an online Mortgage
  Calculator
  
• Purpose provide a user-friendly service to
  potential users for accurately planning mortgage
  and other types of loans
  
• Scope Web-based, platform-independent, single
  user client-side application with validation and
  meaningful input/output.

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• The Problem Solution Approach
• Algorithm standard loan calculation with fixed
  number of payments
  
• Payment Principal (InterestRate / (1
  (InterestRate 1) 12 Periods)
  
• Inputs Principal, InterestRate, Periods
• Output Payment
• Where InterestRate is the rate for each payment
  period in decimals
  
• for example if the annual mortgage interest
  rate is 5.0, then
  
• the InterestRate used here is 5.0 / 100 / 12
  0.00416666
  
• assuming the payment period is in months.
• GUI with Event-Based Programming - Interactive

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• Diagrammatic Aids layout of screen

Inputs
Outputs
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• Diagrammatic Aids Class Diagram

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• The Operating Environment
• Web HTTP use a HTML file to transport the
  application to client
  
• Use a browser as the client-side application
  launcher assume support of JRE?
  
• Cross-Platform functionality
• Choosing the Programming Language Text/GUI,
  purpose
  
• Java general purpose, Text or GUI,
  cross-platform functionality with Java Runtime
  Environment within a browser assume knowledge
  and availability of JDK

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• The Primitives of the Language objects,
  variables, data types, declarations, numbers,
  strings, etc.

inherits
public class mortgage extends Applet
implements ActionListener int intMon, intYea
r double dblInterestPayment Font fntRegular
new Font (Serif,Font.Bold, 18)
Label lblYears new Label(Years)
TextField txtReturnRate new TextField(,5)
Button resetButton new Button(Reset)
String public void init ( )
Object
Interface
Declarations
Method
Component
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• The Input/Output (I/O) System
• Arithmetic Expressions and Assignment Statements
• dblMonthly dblPrincipal (dblInterest /
• (1-Math.pow(dblInterest1,-12.0intYear)
• Decision Making and Logical Expressions
• if ( strValue.length( ) 0 )
• else

GUI TxtFields and Labels, layout managers
Screen rendering by Browser
or Applet Viewer
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• Support of Structured Programming Techniques -
  Yes
  

Repetition while ( condition)
do
while ( condition )
Sequence Yes Selection if (condition) e
lse if (condition) switch ( choice
) case 1 . Break case 2
. Break default
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• Functions and Subroutines modules - methods
• public boolean Validate (TextField strParam, int
  intReturn)
  
• return true
• Event-based Programming for GUIs, Interface
  Design - components
  

public class mortgage extends Applet
implements ActionListener txtPrincipal.add
ActionListener(this) public void actionPerfor
med(ActionEvent evt)
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• Internal Storage - Arrays and Data Structures -
  NA
  
• External Storage - Files and Databases- NA
• Error Detection and Handling
• try
• code segment which might generate error
• catch (NumberFormatException err)
• code to handle the error condition

Example of error condition to be detected
Actual error
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17. Input Validation (general)
Existence Check
Domain Check
Field Value Exists ?
Start
T
Value is Valid Type ?
F
T
No Input Entered
Size of Value Is Valid ?
T
F
Invalid Input Type
Value within Valid Range ?
Process The Input Data
F
Invalid Input Size
F
Invalid Input Value


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• Output Formatting
• text package, format classes
• Projects and Programming Tasks
• Files, Packages, IDE
• Operational issues compile/link/execute
• JavaC, JavaR, importing classes
• Deployment, Version Control, etc.

End