Designing a Java ProgramPrinciples of Software Engineering

INFSY 535

Systems Small systems

Larger systems

1. Understand the program requirement-what

3. Write and test each part (unit testing) 4. Maintenance

2. Specify the solution-how

Model/design(UML comes into play)

AnalysisI/O is critical

implementation

Planning, design, and testing

deployment

The Waterfall Model

what

how

Write

The Spiral Model : deals with errors from previous phase (Boehm)

• Development process methodology by the inventors of UML

Rational Unified Process

• Focuses on best practices • Realistic planning Continuous integration• Small releases 40-hour week• Metaphor on-site customer• Simplicity coding standards• Testing • Refactoring • Pair programming • Collective ownership

Extreme Programming

Big Java by Cay Horstmann Copyright © 2008 by John Wiley

& Sons. All rights reserved.

• Interaction of a black box with outside world is well-defined

• Encapsulation

Levels of Abstraction: Black Box

Java Class Concept

Encapsulation◦ Blackbox concept

Data and method(s)Hidden details

Interface Effect(s)

methods called

class

Behavior of bank account (abstraction): • deposit money • withdraw money • get balance

A Class Example (from Chapter 3)

Methods of BankAccount class: • deposit • withdraw • getBalance

Support method calls such as the following: harrysChecking.deposit(2000); harrysChecking.withdraw(500); System.out.println(harrysChecking.getBalance());

Specifying the public Interface of a Class

access specifier (such as public) return type (such as String or void) method name (such as deposit) Parameters list (double amount, double deposit) method body { }

Public Interface of a Class or Method Definition

accessSpecifier returnType methodName(parameterType parameterName, . . .)

{ method body

}

Method Definition Format

Example:public void deposit(double amount) { . . . }

Method Definition Example

public BankAccount(){ // body--filled in later

Public Interface of a Class: Constructor Definition

Javadoc Method Summary

Model/design/represent the solution?

Show class relationships

UML Class Diagrams

Components of the UML

Class Diagram Object Diagram Use Case Diagram State Diagram Sequence Diagram Activity Diagram Collaboration Diagram Component Diagram Deployment Diagram

UML:Universal Modeling Language

Rectangles Three sections:

◦Class/object name ◦Class attributes (data)◦Operations (methods)

Arrows that indicates the relationship

Class Name

Attributes/ characteristics:variables

Methods/capabilities

Class Diagram with Variables and Methods

Visibility: private - public + (chapter 3)

Using VISIO 2007 to Produce UML Diagrams

Click on VISIO Select the Software Category

Visio Tutorial

Visio Lab

InheritanceAggregationDependency

Relationships Between Classes

Preparation:◦Verbally describe the situation (what)

◦(How) Find objects (methods) that will be part of model

Describe properties of the objects Establish relations between the objects

Place the objects in groups

UML Class Diagrams

Java facilitates working with Objects

Terminology: Objects are abstractions

Objects are manipulated by classes

• May be 1 or many class instances of any particular class/object.

• Each instance is instantiated.

Relationship Symbol Line Style

Arrow Tip

Inheritance-is-a

                                         

Solid Triangle

Interface Implementation

                                    

      Dotted Triangle

Aggregation-has-a

                                          

Solid Diamond

Dependency

                                         

Dotted Open

UML Relationship Symbols

Aggregation is a stronger form of dependency-see page 467

has-a relationship

Establishes has-a relationship/association between classes BankAccount One can navigate from one class to another instantiation in Java – (note NOT inheritance)

Aggregation arrows

Arrow with diamond head: one class uses the other by linking methods of the other class. The arrow indicates the direction of the aggregation

dependency

Multiplicity (Cardinality)

• Place multiplicity notations near the ends of an association.

                                                                                                                            

Lab and HomeWork

Program Exercises P3.1 and P3.2

Inheritance Inheritance : allows a

developer to derive a new class from an existing one

Parent class, or superclass, or base class.

Thechild class or subclass. Component hierarchy:

Inheritance-generalization

Establishes an is-a relationship between a more general class (superclass) and a more specialized class (subclass or base class)

Inheritance

Inheritance should create an is-a relationship, meaning the child is a more specific version of the parent

Deposit

BankForm parentIs-a component of

child