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Chapter 1�Introduction

Java Software Solutions

Foundations of Program Design

9^th Edition

John Lewis

William Loftus

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Focus of the Course

Object-Oriented Software Development

problem solving
program design, implementation, and testing
object-oriented concepts

classes
objects
encapsulation
inheritance
polymorphism

graphical user interfaces
the Java programming language

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Introduction

We start with the fundamentals of computer processing
Chapter 1 focuses on:

components of a computer
how computers store and manipulate information
computer networks
the Internet and the World Wide Web
programming and programming languages
an introduction to Java
an overview of object-oriented concepts

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Outline

Computer Processing

Hardware Components

Networks

The Java Programming Language

Program Development

Object-Oriented Programming

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Hardware and Software

Hardware

the physical, tangible parts of a computer
keyboard, monitor, disks, wires, chips, etc.

Software

programs and data
a program is a series of instructions

A computer requires both hardware and software
Each is essentially useless without the other

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CPU and Main Memory

Central

Processing

Unit

Main

Memory

Chip that executes program commands

Primary storage area for programs and data that are in active use

Synonymous with RAM

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Input / Output Devices

Central

Processing

Unit

Main

Memory

Monitor screen

Keyboard

Mouse

Touch screen

I/O devices facilitate

user interaction

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Secondary Memory Devices

Central

Processing

Unit

Main

Memory

Information is moved

between main and

secondary memory

as needed

Hard Disk

USB Flash Drive

Secondary memory

devices provide

long-term storage

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Software Categories

Operating System

controls all machine activities
provides the user interface to the computer
manages resources such as the CPU and memory
Windows, Mac OS, Unix, Linux,

Application program

generic term for any other kind of software
word processors, missile control systems, games

Most operating systems and application programs have a graphical user interface (GUI)

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Analog vs. Digital

There are two basic ways to store and manage data:
Analog

continuous, in direct proportion to the data represented
music on a record album - a needle rides on ridges in the grooves that are directly proportional to the voltages sent to the speaker

Digital

the information is broken down into pieces, and each piece is represented separately
sampling – record discrete values of the analog representation
music on a compact disc - the disc stores numbers representing specific voltage levels sampled at specific times

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Analog Information

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Sampling

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Digital Information

Computers store all information digitally:

numbers
text
graphics and images
audio
video
program instructions

In some way, all information is digitized - broken down into pieces and represented as numbers

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Representing Text Digitally

For example, every character is stored as a number, including spaces, digits, and punctuation
Corresponding upper and lower case letters are separate characters

H i , H e a t h e r .

72 105 44 32 72 101 97 116 104 101 114 46

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Binary Numbers

Once information has been digitized, it is represented and stored in memory using the binary number system
A single binary digit (0 or 1) is called a bit
Devices that store and move information are cheaper and more reliable if they have to represent only two states
A single bit can represent two possible states, like a light bulb that is either on (1) or off (0)
Permutations of bits are used to store values

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Bit Permutations

1 bit

0

1

2 bits

00

01

10

11

3 bits

000

001

010

011

100

101

110

111

4 bits

0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

Each additional bit doubles the number of possible permutations

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Bit Permutations

Each permutation can represent a particular item
There are 2^N permutations of N bits
Therefore, N bits are needed to represent 2^N unique items

2¹ = 2 items

2² = 4 items

2³ = 8 items

2⁴ = 16 items

2⁵ = 32 items

1 bit ?

2 bits ?

3 bits ?

4 bits ?

5 bits ?

How many

items can be

represented by

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Quick Check

How many bits would you need to represent each of the 50 United States using a unique permutation of bits?

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Quick Check

How many bits would you need to represent each of the 50 United States using a unique permutation of bits?

Five bits wouldn't be enough, because 2⁵ is 32.

Six bits would give us 64 permutations, and some wouldn't be used.

000000 Alabama

000001 Alaska

000010 Arizona

000011 Arkansas

000100 California

000101 Colorado

etc.

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Outline

Computer Processing

Hardware Components

Networks

The Java Programming Language

Program Development

Object-Oriented Programming

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A Computer Specification

Consider the following specification for a personal computer:

Intel Dual-Core i7 processor
4 GB RAM
750 GB Hard Disk
15” High Definition Display with 1366 x 768 resolution
802.11 wireless card

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Computer Architecture

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Memory

Main memory is divided into many memory locations (or cells)

9278

9279

9280

9281

9282

9283

9284

9285

9286

Each memory cell has a numeric address, which uniquely identifies it

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Storing Information

9278

9279

9280

9281

9282

9283

9284

9285

9286

Large values are

stored in consecutive

memory locations

10011010

Each memory cell stores a set number of bits (usually 8 bits, or one byte)

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Storage Capacity

Every memory device has a storage capacity, indicating the number of bytes it can hold
Capacities are expressed in various units:

Unit	Symbol	Number of Bytes
kilobyte	KB	2¹⁰ = 1024
megabyte	MB	2²⁰ (over one million)
gigabyte	GB	2³⁰ (over one billion)
terabyte	TB	2⁴⁰ (over one trillion)
petabyte	PB	2⁵⁰ (a whole bunch)

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Memory

Main memory is volatile - stored information is lost if the electric power is removed
Secondary memory devices are nonvolatile
Main memory and disks are direct access devices - information can be reached directly
The terms direct access and random access often are used interchangeably
A magnetic tape is a sequential access device since its data is arranged in a linear order - you must get by the intervening data in order to access other information

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Hard Disk Drive

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RAM vs. ROM

RAM - Random Access Memory (direct access)
ROM - Read-Only Memory
The terms RAM and main memory are basically interchangeable
ROM could be a set of memory chips, or a separate device, such as a CD ROM
Both RAM and ROM are random (direct) access devices!
RAM probably should be called Read-Write Memory

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Compact Discs

A CD-ROM is portable read-only memory
A microscopic pit on a CD represents a binary 1 and a smooth area represents a binary 0
A low-intensity laser reflects strongly from a smooth area and weakly from a pit
A CD-Recordable (CD-R) drive can be used to write information to a CD once
The speed of a CD drive indicates how fast (max) it can read and write information to a CD

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DVDs

A DVD is the same physical size as a CD, but can store much more information
The format of a DVD stores more bits per square inch
A CD can store 650 MB, while a standard DVD can store 4.7 GB

A double sided DVD can store 9.4 GB
Other advanced techniques can bring the capacity up to 17.0 GB

Like CDs, there are DVD-R discs

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The Central Processing Unit

A CPU is on a chip called a microprocessor
It continuously follows the fetch-decode-execute cycle:

fetch

Retrieve an instruction from main memory

decode

Determine what the

instruction is

execute

Carry out the

instruction

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The Central Processing Unit

Arithmetic / Logic Unit

Registers

Control Unit

Small storage areas

Performs calculations and makes decisions

Coordinates processing steps

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The Central Processing Unit

The speed of a CPU is controlled by the system clock
The system clock generates an electronic pulse at regular intervals
The pulses coordinate the activities of the CPU
The speed is usually measured in gigahertz (GHz)

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Monitor

The size of a monitor (15.6") is measured diagonally, like a television screen
A monitor has a certain maximum resolution , indicating the number of picture elements, called pixels, that it can display (such as 1366 by 768)
High resolution (more pixels) produces sharper pictures

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Outline

Computer Processing

Hardware Components

Networks

The Java Programming Language

Program Development

Object-Oriented Programming

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Networks

A network is two or more computers that are connected so that data and resources can be shared
Most computers are connected to some kind of network
Each computer has its own network address, which uniquely identifies it among the others
A file server is a network computer dedicated to storing programs and data that are shared among network users

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Network Connections

Each computer in a network could be directly connected to every other computer in the network
These are called point-to-point connections

This technique is not practical for

more than a few close machines

Adding a computer requires

a new communication line

for each computer already

in the network

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Network Connections

Most networks share a single communication line
Adding a new computer to the network is relatively easy

Network traffic must take

turns using the line, which

introduces delays

Often information is broken

down in parts, called packets,

which are sent to the receiving

machine and then reassembled

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A Computer Network

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Local-Area Networks

LAN

A Local-Area Network

(LAN) covers a small

distance and a small

number of computers

A LAN often connects the machines

in a single room or building

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Wide-Area Networks

LAN

A Wide-Area Network (WAN)

connects two or more LANs,

often over long distances

LAN

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The Internet

The Internet is a WAN which spans the planet
The word Internet comes from the term internetworking
It started as a United States government project, sponsored by the Advanced Research Projects Agency (ARPA)

originally it was called the ARPANET

The Internet grew quickly throughout the 1980s and 90s

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TCP/IP

A protocol is a set of rules that determine how things communicate with each other
The software that manages Internet communication follows a suite of protocols called TCP/IP
The Internet Protocol (IP) determines the format of the information as it is transferred
The Transmission Control Protocol (TCP) dictates how messages are reassembled and handles lost information

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IP and Internet Addresses

Each computer on the Internet has a unique IP address, such as:

204.192.116.2

Most computers also have a unique Internet name, which also is referred to as an Internet address:

hector.vt.edu

The first part indicates a particular computer (hector)
The rest is the domain name, indicating the organization (vt.edu)

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Domain Names

The last part of a domain name, called a top-level domain (TLD), supposedly indicates the type of organization:

edu educational institution

com commercial entity

org non-profit organization

net network-based organization

Sometimes the suffix

indicates the country:

uk United Kingdom

au Australia

ca Canada

se Sweden

Additional TLDs have

been added, including:

biz, info, tv, name

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Domain Names

A domain name can have several parts
Unique domain names mean that multiple sites can have individual computers with the same local name
When used, an Internet address is translated to an IP address by software called the Domain Name System (DNS)
There is no one-to-one correspondence between the sections of an IP address and the sections of an Internet address

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The World Wide Web

The World Wide Web allows many different types of information to be accessed using a common interface
A browser is a program which accesses network resources and presents them

Popular browsers: Internet Explorer, Safari, Firefox

Resources presented include:

text, graphics, video, sound, audio, executable programs

A Web document usually contains links to other Web documents, creating a hypermedia environment
The term Web comes from the fact that information is not organized in a linear fashion

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The World Wide Web

Web documents are often defined using the HyperText Markup Language (HTML)
Information on the Web is found using a Uniform Resource Locator (URL):

http://www.google.com

http://www.whitehouse.gov/issues/education

A URL specifies a protocol (http), a domain, and possibly specific documents
You can also use a browser with other protocols, such as ftp

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Outline

Computer Processing

Hardware Components

Networks

The Java Programming Language

Program Development

Object-Oriented Programming

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Java

The Java programming language was created by Sun Microsystems, Inc.
It was introduced in 1995 and it's popularity has grown quickly since
A programming language specifies the words and symbols that we can use to write a program
A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements

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Java Program Structure

In the Java programming language:

A program is made up of one or more classes
A class contains one or more methods
A method contains program statements

These terms will be explored in detail throughout the course
A Java application always contains a method called main
See Lincoln.java

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//********************************************************************

// Lincoln.java Author: Lewis/Loftus

//

// Demonstrates the basic structure of a Java application.

//********************************************************************

public class Lincoln

{

//-----------------------------------------------------------------

// Prints a presidential quote.

//-----------------------------------------------------------------

public static void main(String[] args)

{

System.out.println("A quote by Abraham Lincoln:");

System.out.println("Whatever you are, be a good one.");

}

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//********************************************************************

// Lincoln.java Author: Lewis/Loftus

//

// Demonstrates the basic structure of a Java application.

//********************************************************************

public class Lincoln

{

//-----------------------------------------------------------------

// Prints a presidential quote.

//-----------------------------------------------------------------

public static void main(String[] args)

{

System.out.println("A quote by Abraham Lincoln:");

System.out.println("Whatever you are, be a good one.");

}

Output

A quote by Abraham Lincoln:

Whatever you are, be a good one.

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Java Program Structure

public class MyProgram

{

}

// comments about the class

class header

class body

Comments can be placed almost anywhere

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Java Program Structure

public class MyProgram

{

}

// comments about the class

public static void main (String[] args)

{

}

// comments about the method

method header

method body

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Comments

Comments should be included to explain the purpose of the program and describe processing steps
They do not affect how a program works
Java comments can take three forms:

// this comment runs to the end of the line

/* this comment runs to the terminating

symbol, even across line breaks */

/** this is a javadoc comment */

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Identifiers

Identifiers are the "words" in a program
A Java identifier can be made up of letters, digits, the underscore character ( _ ), and the dollar sign
Identifiers cannot begin with a digit
Java is case sensitive: Total, total, and TOTAL are different identifiers
By convention, programmers use different case styles for different types of identifiers, such as

title case for class names - Lincoln
upper case for constants - MAXIMUM

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Identifiers

Sometimes the programmer chooses the identifer(such as Lincoln)
Sometimes we are using another programmer's code, so we use the identifiers that he or she chose (such as println)
Often we use special identifiers called reserved words that already have a predefined meaning in the language
A reserved word cannot be used in any other way

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Reserved Words

The Java reserved words:

abstract

assert

boolean

break

byte

case

catch

char

class

const

continue

default

do

double

else

enum

extends

false

final

finally

float

for

goto

if

implements

import

instanceof

int

interface

long

native

new

null

package

private

protected

public

return

short

static

strictfp

super

switch

synchronized

this

throw

throws

transient

true

try

void

volatile

while

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Quick Check

Which of the following are valid Java identifiers?

grade

quizGrade

NetworkConnection

frame2

3rdTestScore

MAXIMUM

MIN_CAPACITY

student#

Shelves1&2

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Quick Check

Which of the following are valid Java identifiers?

grade

quizGrade

NetworkConnection

frame2

3rdTestScore

MAXIMUM

MIN_CAPACITY

student#

Shelves1&2

Valid

Invalid – cannot begin with a digit

Valid

Invalid – cannot contain the '#' character

Invalid – cannot contain the '&' character

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White Space

Spaces, blank lines, and tabs are called white space
White space is used to separate words and symbols in a program
Extra white space is ignored
A valid Java program can be formatted many ways
Programs should be formatted to enhance readability, using consistent indentation
See Lincoln2.java and Lincoln3.java

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Outline

Computer Processing

Hardware Components

Networks

The Java Programming Language

Program Development

Object-Oriented Programming

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Program Development

The mechanics of developing a program include several activities:

writing the program in a specific programming language (such as Java)
translating the program into a form that the computer can execute
investigating and fixing various types of errors that can occur

Software tools can be used to help with all parts of this process

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Language Levels

There are four programming language levels:

machine language
assembly language
high-level language
fourth-generation language

Each type of CPU has its own specific machine language
The other levels were created to make it easier for a human being to read and write programs

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Programming Languages

Each type of CPU executes only a particular machine language
A program must be translated into machine language before it can be executed
A compiler is a software tool which translates source code into a specific target language
Sometimes, that target language is the machine language for a particular CPU type
The Java approach is somewhat different

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Java Translation

The Java compiler translates Java source code into a special representation called bytecode
Java bytecode is not the machine language for any traditional CPU
Bytecode is executed by the Java Virtual Machine (JVM)
Therefore Java bytecode is not tied to any particular machine
Java is considered to be architecture-neutral

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Java Translation

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Development Environments

There are many programs that support the development of Java software, including:

Java Development Kit (JDK)
Eclipse
NetBeans
BlueJ
jGRASP

Though the details of these environments differ, the basic compilation and execution process is essentially the same

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Syntax and Semantics

The syntax rules of a language define how we can put together symbols, reserved words, and identifiers to make a valid program
The semantics of a program statement define what that statement means (its purpose or role in a program)
A program that is syntactically correct is not necessarily logically (semantically) correct
A program will always do what we tell it to do, not what we meant to tell it to do

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Errors

A program can have three types of errors
The compiler will find syntax errors and other basic problems (compile-time errors)

If compile-time errors exist, an executable version of the program is not created

A problem can occur during program execution, such as trying to divide by zero, which causes a program to terminate abnormally (run-time errors)
A program may run, but produce incorrect results, perhaps using an incorrect formula (logical errors)

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Basic Program Development

errors?

Edit and

save program

Compile program

Execute program and

evaluate results

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Outline

Computer Processing

Hardware Components

Networks

The Java Programming Language

Program Development

Object-Oriented Programming

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Problem Solving

The purpose of writing a program is to solve a problem
Solving a problem consists of multiple activities:

Understand the problem
Design a solution
Consider alternatives and refine the solution
Implement the solution
Test the solution

These activities are not purely linear – they overlap and interact

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Problem Solving

The key to designing a solution is breaking it down into manageable pieces
When writing software, we design separate pieces that are responsible for certain parts of the solution
An object-oriented approach lends itself to this kind of solution decomposition
We will dissect our solutions into pieces called objects and classes

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Object-Oriented Programming

Java is an object-oriented programming language
As the term implies, an object is a fundamental entity in a Java program
Objects can be used effectively to represent real-world entities
For instance, an object might represent a particular employee in a company
Each employee object handles the processing and data management related to that employee

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Objects

An object has:

state - descriptive characteristics
behaviors - what it can do (or what can be done to it)

The state of a bank account includes its account number and its current balance
The behaviors associated with a bank account include the ability to make deposits and withdrawals
Note that the behavior of an object might change its state

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Classes

An object is defined by a class
A class is the blueprint of an object
The class uses methods to define the behaviors of the object
The class that contains the main method of a Java program represents the entire program
A class represents a concept, and an object represents the embodiment of that concept
Multiple objects can be created from the same class

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Class = Blueprint

One blueprint to create several similar, but different, houses:

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Objects and Classes

Bank Account

A class

(the concept)

John’s Bank Account

Balance: $5,257

An object

(the realization)

Bill’s Bank Account

Balance: $1,245,069

Mary’s Bank Account

Balance: $16,833

Multiple objects

from the same class

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Inheritance

One class can be used to derive another via inheritance
Classes can be organized into hierarchies

Bank Account

Account

Charge Account

Savings Account

Checking Account

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Summary

Chapter 1 focused on:

components of a computer
how those components interact
how computers store and manipulate information
computer networks
the Internet and the World Wide Web
programming and programming languages
an introduction to Java
an overview of object-oriented concepts