Software Engineering

1
Software Engineering

• Software Development Process
• Incremental Development
• Monogram program

2
Program Development Process

• Design the program
• Use a text editor (vim) to write a java file
• vim MyClass.java
• Compile the java code to create a class file
• javac MyClass.java
• Run the program
• javac MyClass
• Create the documentation
• javadoc MyClass.java

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Software Engineering

• Much like building a skyscraper, we need a
  disciplined approach in developing complex
  software applications.
• Software engineering is the application of a
  systematic and disciplined approach to the
  development, testing, and maintenance of a
  program.

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Software Life Cycle

• The sequence of stages from conception to
  operation of a program is called software life
  cycle.
• Analysis
• Define the problem
• Design
• Work out a solution
• Here's where you use UML diagrams
• Coding
• Testing
• Operation and Maintenance

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Analysis

• What should the program do?
• Who will use the program?
• Is the problem solvable?

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Design

• This is where you decide how to implement a
  program
• What classes do you need?
• Which classes do you need to write?
• What should the data and methods for each class
  be?
• Define algorithms for various operations
• Work out a plan for the order of implementation

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UML Diagrams

• UML is a graphical language
• It can be used to model various aspects of a
  program
• Use class diagrams to model the structure of the
  application
• Use object diagrams to provide a snapshot of what
  is happening when a program runs
• Other types of diagrams model requirements,
  program state, testing,

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Class Diagram

• Used to
• Show the details of one or more classes
• data, methods
• Show how different classes are related within a
  program
• inheritance (is-a), aggregation (has-a), using
• Illustrate an inheritance hierarchy
• Class diagrams are static
• Class diagrams illustrate the structure of an
  application

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• Generic class diagram
• name of class
• list names of class and instance data values
• list methods with parameters and return types

• Example class diagram
• Contact class represents a person with
  information needed in an address book

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The Structure of an Application

• Use a box for each class
• Use lines to show relationships
• Arrow for inheritance
• Line with diamond for aggregation (has-a)
• Dotted line for uses

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Inheritance Hierarchy

• An example of inheritance hierarchy among
  different types of students.

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Object Diagrams

• Used to illustrate the state of a program at
  different times while it is running
• We will use a kind of object diagrams called
  state-of-memory diagrams to illustrate how Java
  uses memory for storing information

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Object Diagrams

• One box for each object
• Each object may have data inside it

• Example of a Loan object

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Problem Statement

• Problem statement
• Write a program that asks for the users first,
  middle, and last names and replies with their
  initials.

Example input Andrew Lloyd Weber output
ALW
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Overall Plan

• Identify the major tasks the program has to
  perform.
• We need to know what to develop before we
  develop!
• Tasks
• Get the users first, middle, and last names
• Extract the initials and create the monogram
• Output the monogram

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Development Steps

• We will develop this program in two steps
• Start with the program template and add code to
  get input
• Add code to compute and display the monogram

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Step 1 Design

• The program specification states get the users
  name but doesnt say how.
• We will consider how in the Step 1 design
• We will use JOptionPane for input
• Input Style Choice 1
• Input first, middle, and last names separately
• Input Style Choice 2
• Input the full name at once
• We choose Style 2 because it is easier and
  quicker for the user to enter the information

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Step 1 Code
/ Chapter 2 Sample Program Displays the
Monogram File Step1/Ch2Monogram.java / import
javax.swing. class Ch2Monogram public
static void main (String args) String
name name JOptionPane.showInputDialog(null,
"Enter your full name (first,
middle, last)) JOptionPane.showMessageDialog
(null, name)
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Step 1 Test

• In the testing phase, we run the program and
  verify that
• we can enter the name
• the name we enter is displayed correctly

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Step 2 Design

• Our programming skills are limited, so we will
  make the following assumptions
• input string contains first, middle, and last
  names
• first, middle, and last names are separated by
  single blank spaces
• Example
• John Quincy Adams (okay)
• John Kennedy (not okay)
• Harrison, William Henry (not okay)

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Step 2 Design (contd)

• Given the valid input, we can compute the
  monogram by
• breaking the input name into first, middle, and
  last
• extracting the first character from them
• concatenating three first characters

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Step 2 Code
/ Chapter 2 Sample Program Displays the
Monogram File Step 2/Ch2MonogramStep2.java / i
mport javax.swing. class Ch2Monogram
public static void main (String args)
String name, first, middle, last,
space, monogram space "
//Input the full name name
JOptionPane.showInputDialog(null,
"Enter your full name (first, middle, last) )
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Step 2 Code (contd)
//Extract first, middle, and last names first
name.substring(0, name.indexOf(space)) name
name.substring(name.indexOf(space)1,
name.length()) middle
name.substring(0, name.indexOf(space)) last
name.substring(name.indexOf(space)1,
name.length()) //Compute the
monogram monogram first.substring(0, 1)
middle.substring(0, 1) last.substri
ng(0,1) //Output the result JOptionPane.show
MessageDialog(null, "Your monogram is "
monogram)
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Step 2 Test

• In the testing phase, we run the program and
  verify that, for all valid input values, correct
  monograms are displayed.
• We run the program numerous times. Seeing one
  correct answer is not enough. We have to try out
  many different types of (valid) input values.

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Program Review

• The work of a programmer is not done yet.
• Once the working program is developed, we perform
  a critical review and see if there are any
  missing features or possible improvements
• One suggestion
• Improve the initial prompt so the user knows the
  valid input format requires single spaces between
  the first, middle, and last names