oop chapter 1 by jlncrnl

8/11/2019 OOP chapter 1 by JLNCRNL

1/62

Chapter 1Introduction


2/62

1-2

Outline

Brief History of Java

The Java Programming Language

Program Development

Object-Oriented Programming


3/62

Brief History of java

In 1990, Sun Microsystems began an internal project known as

the Green Projectto work on a new technology.

In 1992, the Green Project was spun off and its interest directedtoward building highly interactive devices for the cable TV

industry. This failed to materialize.

In 1994, the focus of the original team was re-targeted, this tim

to the use of Internet technology. A small web browser calledHotJavawas written. Oak was renamed toJavaafter learning

that Oak had already been trademarked.

In 1995, Java was first publicly released.

In 1996, Java Development Kit (JDK) 1.0 was released.

In 2002, JDK 1.4 (codenameMerlin) was released, the most

widely used version.

In 2004, JDK 5.0 (codename Tiger) was released, the latest

version.

1-3


4/62

James Gosling

James Goslingis generally

credited as the inventor of the Java

programming language

He was the first designer of Java

and implemented its original

compiler and virtual machine He is also known as the Father of

Java

He is currently the Chief Technical

Officer of Sun Microsystems


5/62

1-5

Java

A programm ing languagespecifies the words andsymbols 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 prog ram statements

The Java programming language was created by

Sun Microsystems, Inc.

It was introduced in 1995 and it's popularity hasgrown quickly since


6/62

Java Platform Editions

A Java Platform is the set of APIs, class libraries, and other programs

used in developing Java programs for specific applications

There are 3 Java Platform Editions

1. Java SE (Standard Edition)- formerly J2SE

Core Java Platform targeting applications running on workstations

2. Java EE (Enterprise Edition) formerly J2EE

Component-based approach to developing distributed, multi-tier

enterprise applications

3. Java ME (Mobile Edition), formerly J2ME

Targeted at small, stand-alone or connectable consumer and

embedded devices

1-6


7/62

Java Development Kit (JDK)

Java Development Kit (JDK)

Is a set of Java tools for developing Java programs

Consists of Java API, Java Compiler, and JVM

Java Application Programming Interface (API)

Is prewritten code, organized into packages of similar topics

Java Virtual MachineJava API

MyProgram.java

Hardware - Based Platform

JDK

JRE

Java VirtualMachine (JVM)

Is an

execution engine that

runs compiled Java

byte code

1-7


8/62

1-8

Java Program Structure

In the Java programming language: A programis made up of one or more classes

A classcontains one or more methods

A methodcontains program statements

A Java application always contains a methodcalledmain


9/62

1-9


public classMyProgram

{

}

// comments about the class

class header

class body

Comments can be placed almost anywhere


10/62

1-10


public class MyProgram

{

}

// comments about the class

public static voidmain(String[] args)

{

}

// comments about the method

method header

method body


11/62

9/17/2014

11

The First Java Program

classWelcome{

/* The Welcome Program-------------------

Illustrates a simple program displaying

a message.

*/

public static void main (String [ ] args) {

System.out.println("Welcome to Java!");

}

}

Type all carefully and save it to a

file named Welcome.java


12/62

9/17/2014

12


classWelcome {



a message.

*/



}

}

Java program source files (.java)

contain definition of classes


13/62


14/62

9/17/2014

14


class Welcome {



a message.

*/

public static voidmain(String [ ] args) {


}

}

Curly braces pair enclose a block

of code, method main()here

Dont miss me!


15/62

9/17/2014

15


class Welcome {



a message.

*/



}

}

This is a block of comments, for

human, not for computer

It explains to you what happens


16/62

9/17/2014

16


class Welcome {



a message.

*/



}

}

This is a method of the class

Welcome, named main()


17/62

9/17/2014

17


class Welcome {



a message.

*/

public static void main (String [ ] args){


}

}

There MUSTbe a pair of

parentheses following ALL

method names


18/62

9/17/2014

18


class Welcome {



a message.

*/



}

}

A method maytake some input

from the caller, formally known as

argumentsorparameters


19/62

9/17/2014

19


class Welcome {



a message.

*/

public static voidmain (String [ ] args) {


}

}

A method maygive some output to the

caller too, known as return value

void means no return value


20/62

9/17/2014

20


class Welcome {



a message.

*/

public staticvoid main (String [ ] args) {


}

}

The statickeyword before a

method definition indicates this is

a class method


21/62

9/17/2014

21


class Welcome {



a message.

*/

publicstatic void main (String [ ] args) {


}

}

This method is apublicone, others

can callme.


22/62

9/17/2014

22


class Welcome {



a message.

*/

public static void main(String [ ] args) {


}

}

Standard properties of the main() method


23/62

9/17/2014

23


class Welcome {



a message.

*/



}

}

A statement(instruction) to display

a message


24/62

9/17/2014

24


Change to the directory containing the fileWelcome.java

Typejavac Welcome.java

It generates a new fileWelcome.class

Type (without .class)

java Welcome

Whats the result?


25/62

1-25

Comments

Comments in a program are called in l ine

documentat ion

They should be included to explain the purposeof 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 terminatingsymbol, even across line breaks */

/** this is a javadoccomment */


26/62

1-26

Identifiers

Identi f iersare the words a programmer uses in aprogram

An identifier can be made up of letters, digits, theunderscore character ( _ ), and the dollar sign

Identifiers cannot begin with a digit Java is case sens it ive-Total, total, andTOTAL are different identifiers

By convention, programmers use different case

styles for different types of identifiers, such as t i t le casefor class names - Lincoln

upper casefor constants -MAXIMUM


27/62

1-27

Identifiers

Sometimes we choose identifiers ourselves whenwriting a program (such as Lincoln)

Sometimes we are using another programmer's

code, so we use the identifiers that he or she

chose (such asprintln)

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


28/62

1-28

Reserved Words

The Java reserved words:

abstract

assert

boolean

break

bytecase

catch

char

class

const

continuedefault

do

double

else

enum

extends

false

finalfinally

float

for

goto

if

implementsimport

instanceof

int

interface

long

native

new

nullpackage

private

protected

public

return

shortstatic

strictfp

super

switch

synchronized

this

throw

throwstransient

true

try

void

volatile

while


29/62

1-29

White Space

Spaces, blank lines, and tabs are called white

space

White spaceis 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


30/62

1-30

Outline


Program Development



31/62

1-31

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 canexecute

investigating and fixing various types of errors that can

occur

Software tools can be used to help with all parts ofthis process


32/62

1-32

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


33/62

1-33

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 compi leris a software tool which translates

source codeinto a specific target language

Often, that target language is the machine

language for a particular CPU type

The Java approach is somewhat different


34/62

1-34

Java Translation

The Java compiler translates Java source code

into a special representation called bytecode

Java bytecode is not the machine languagefor any

traditional CPU

Another software tool, called an interpreter,

translates bytecode into machine language and

executes it

Therefore the Java compiler is not tied to anyparticular machine

Java is considered to be architecture-neutral


35/62

1-35

Java Translation

Java sourcecode

Machinecode

Java

bytecode

Bytecode

interpreter

Bytecode

compiler

Java

compiler


36/62

COREJAVA

Java source.java

javac

Java bytecode .class

JVM

Programming API

Platform interface

of Web Browse

JVM

Programming API

Platform interface

of Windows

JVM

Programming API

Platform interface

of Unix

java

1-36


37/62

1-37

Development Environments

There are many programs that support the

development of Java software, including:

Sun Java Development Kit (JDK)

Sun NetBeans

IBM Eclipse

Borland JBuilder

MetroWerks CodeWarrior

BlueJ

jGRASP

Though the details of these environments differ,

the basic compilation and execution process is

essentially the same


38/62

1-38

Syntax and Semantics

The syntaxru lesof a language define how we can

put together symbols, reserved words, and

identifiers to make a valid program

The semant icsof a program statement define what

that statement means (its purpose or role in aprogram)

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


39/62

1-39

Errors

A program can have three types of errors

The compiler will find syntax errors and other

basic problems (compi le-t ime 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-t ime errors)

A program may run, but produce incorrect results,

perhaps using an incorrect formula (log icalerrors)


40/62

1-40

Basic Program Development

errors

errors

Edit and

save program

Compile program

Execute program and

evaluate results


41/62

1-41

Outline

Brief History of Java


Program Development



42/62

1-42

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 linearthey

overlap and interact


43/62

1-43

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 ob ject-or iented app roachlends itself to this

kind of solution decomposition

We will dissect our solutions into pieces calledobjects and classes


44/62

1-44


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


45/62

1-45

Objects

An object has:

state - descriptive characteristics (attributes)

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


46/62

1-46

Classes

An object is defined by a class

A class is the blueprintof 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


47/62

1-47

Objects and Classes

Bank

Account

A class

the concept)

Johns Bank Account

Balance: $5,257

An object

the realization)

Bills Bank AccountBalance: $1,245,069

Marys Bank AccountBalance: $16,833

Multiple objects

from the same class


48/62

Lesson: Working with Classes

How to Create a New Class

How to Add Instance Data Members

How to Add Methods

How to Create an Instance of a Class

How to Use Constructors

1-48


49/62

How to Create a New Class

Create a new class by using the Add Class

command on the Project menu

Example of new class named BankAccount:

public class BankAccount {

}

1-49


50/62

How to Add Instance Data Members

Adding a data member named balance


privatedoublebalance;

}

Keyword Definition

Public Accessible everywhere

Private Accessible only within the type itself

ProtectedAccessible only by classes which inheritfrom the class

H Add M h d


51/62

How to Add Methods

Adding a method named Deposit


privateDouble balance;

publicdouble Deposit (doubleamount) {balance += amount;

}

}

Overloaded methods: two or more methods withthe same name but different signatures

Example:MessageBox.Show

How to Create an Instance of a


52/62

How to Create an Instance of a

Class Using the New keyword to create an instance of

the BankAccount class:

public class Bank {

public static void main (string args[]) {BankAccount account = newBankAccount( )

account.Deposit(500.00)

}

}

1-52

P ti C ti Cl


53/62

Practice: Creating a Class

In this practice, you will create aBankAccount class with methods

1-53


54/62

How to Use Constructors

Executes code when object is instantiated

public class New {

public int New (inti) {value = i

}

}

Can overload, but does not use Overloads keyword

public class New {

public int New () {

value = 1 }

}

1-54


55/62

What Is Inheritance?

Inheritance specifies an is-a-kind-of relationship

Multiple classes share the same attributes andoperations, allowing efficient code reuse

Examples:

A customer is a kind of person

An employee is a kind of person

Customer Employee

Person

Base Class

Derived Classes

1-55


56/62

1-56

Inheritance

One class can be used to derive another via

inheri tance

Classes can be organized into hierarchies

BankAccount

Account

ChargeAccount

SavingsAccount

CheckingAccount


57/62

How to Inherit from a Class

A derived class inherits from a base class

Properties, methods, data members, events, and

event handlers can be inherited (dependent on

scope)

Keywords

Inheritsinherits from a base class

NotInheritablecannot be inherited from

MustInheritinstances of the class cannot be created;

must be inherited from as a base class

1-57


58/62

What Is Polymorphism?

The method name resides in the base class

The method implementations reside in the derived

classes

BaseTaxCalculateTax( )

CountyTax

CalculateTax( )

CityTax

CalculateTax( )

1-58

C C S


59/62

Comparing Classes to Structures

Classes Structures

Can define data members,

properties, and methods

Can define data members,properties, and methods

Support constructors and

member initialization

No default constructor or

member initialization

Support Finalizemethod Do not support Finalizemethod

Extensible by inheritance Do not support inheritance

Reference type Value type

1-59


60/62

Key Points

A Java source file can include package, import

and class declarations in that order Themain()method is the start of execution of a

Java application

Each Java statement is terminated by a

semicolon ; Identifiers are case-sensitive

Java keywords cannot be used as identifiers

Each variable must be declared with a data type

There are 8 primitive data types:boolean, char,byte, short, int, long, floatand double

There are 3 reference data types: class, array and

interface1-60

K P i t


61/62

Key Points

if()and switch()are used for branching

statements

while(), do-while()and for()are used for

iterating statements

break, continueand labelare used to branch

inside loops

1-61

S


62/62

Summary

Chapter 1 focused on:

programming and programming languages

an introduction to Java

an overview of object-oriented concepts

oop chapter 1 by jlncrnl

Documents