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IAS1223 DATA STRUCTURES AND ALGORITHMS

Chapter 1

Software Engineering

Principles and Java Classes

1

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Chapter Objectives

Data Structures Using Java

2

Learn about software engineering principles

Discover what an algorithm is and explore problem-

solving techniques

Become aware of structured design and object-

oriented design programming methodologies

Learn about user-defined classes

Learn about private, protected, and public membersof a class

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Chapter Objectives


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Explore how classes are implemented

Become aware of Unified Modeling Language (UML)

notation

Examine constructors and destructors

Learn about the abstract data type (ADT)

Explore how classes are used to implement ADT

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Software Life Cycle


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Life cycle: the many phases a program goes through

from the time it is conceived until the time it is

retired

Three fundamental stages of a program

Development

Use

Maintenance

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Software Development Phase


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Design

Algorithm

Structured design

Divide problem into subproblems and analyze eachsubproblem

Object-oriented design Identify components (objects) which form the basis of solution

Determine how these objects interact with one another

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Three basic principles of object-oriented design

(OOD)

Encapsulation: ability to combine data and operations

in a single unit

Inheritance: ability to create new data types from

existing data types

Polymorphism: ability to use the same expression to

denote different operations

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Implementation

Write and compile programming code to implement

classes and functions discovered in design phase

Precondition: a statement specifying that condition(s)

that must be true before the method is called.

Postcondition: a statement specifying what is true after

the method call is completed.

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Testing and Debugging

Test the correctness of the program to make sure it doeswhat it is supposed to do

Find and fix errors Run program through series of specific tests, test cases

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Black-box testing: test based on inputs and outputs not

the internal working of the algorithm or function

White-box testing: relies on the internal structure and

implementation of a function or algorithm; ensures that

every part of the function or algorithm executes at least

once

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Classes


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class: reserved word; collection of a fixed numberof components

Components: member of a class

Members accessed by name Class categories/modifiers

Private

Protected

public

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Classes


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private: members of class not accessible outside

class

public: members of class accessible outside class

Class members: can be methods or variables

Variable members declared like any other

variables

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Syntax


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General syntax for defining a class:modifier(s) class ClassIdentifier modifier(s)

{

classMembers}

General syntax for using the operator new:new className()

ornew className(argument1, argument2, ..., argumentN)

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Classes


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Syntax to access data member of class object or

method:

referenceVariableName.memberName

Shallow copying: two or more reference variables of

the same type point to the same object

Deep copying: each reference variable refers to its

own object. Use method makeCopy()

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Constructors


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Guarantee that data members are initialized when

object is declared

Automatically execute when class object created

Name of constructor is name of class

More than one constructor can be present in one class

Default constructor: constructor without parameters

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The Copy Constructor


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Executes when an object is instantiated

Initialized using an existing object

S

yntaxpublic ClassName(ClassName otherObject)

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UML Diagram


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UML Diagram


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Top box: Name of class

Middle box: data members and their data types

Bottom box: member methods names, parameter

list, return type of method + means public method

- means private method

# means protected method

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Example: class Clock


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myClock = new Clock();

yourClock = new Clock(9,35,15);

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Example: class Clock


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The Modifier Static


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In method heading, specifies that method can beinvoked by using name of class

If used to declare data member, data member

invoked by using class name Static data members of class exist even when no

object of class type instantiated

Static variables are initialized to their default

values

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static Data Members of a Class


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Illustrate illusObject1 = new Illustrate(3);

Illustrate illusObject2 = new Illustrate(5);

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Finalizers


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Automatically execute when class object goes out of

scope

Have no parameters

Only one finalizer per class

Name of finalizer: finalize

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Creating Packages


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Can create packages using reserved word package

Define the class to be public (If class not public it can

only be used within package)

Choose name for package. Organize package (createsubdirectories)

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The Reference this


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Refers to instance variables and methods of a class

Used to implement cascaded method calls

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Inner Classes


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Defined within other classes

Can be either a complete class definition or

anonymous inner class definition

Used to handle events

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Object-Oriented Design


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Simplified methodology

1. Write down detailed description of problem

2. Identify all (relevant) nouns and verbs

3. From list of nouns, select objects

4. Identify data components of each object

5. From list of verbs, select operations

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Chapter Summary


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Software Life Cycle

Development, Use, Maintenance

Algorithm Analysis: The Big-O Notation

Classes

UML Diagram

Constructors, Destructors

Abstract Data Types

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Chapter Summary


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Analysis

Design

Structured design

Object-oriented design

Encapsulation, Inheritance, Polymorphism

Implementation


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