Unit-I JAVA

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SREE VENKATESWARA COLLEGEOF ENGINEERING

N.RAJUPALEM

NELLORE

JAVA PROGRAMMINGReference Material

Unit-I

COMPILE !"#- . ARUNPRASA

ASST. PROFESSOR$ CSE EPARTMENT$

SVCN$KOAVALURU.



Unit - I

INTRODUCTION

Java is an object oriented programming language developed by James Gosling & his crew.

Previously it was called OAK but it’s renamed to java during !!".

#any versions evolved over the years now the current version is java J$K %.

KEY ATTRIBUTES OF OOP

n computer science' computer languages adopt particular programming methodology to write

programs.

(or e)ample' * language uses structured programming' Assembly language uses non structured

whereas java uses object oriented programming.

All java programs are written using object oriented programming concepts.

+he oop concepts or ,ey attributes o- oop are encapsulation, inheritance, an pol!"orphis"#

Encapsulation$

ncapsulation is the mechanism o- hiding the internal details and allowing a simple inter-ace

which ensures that the object can be used without having to ,now its internal details.

E%a"ple/ A swipe machine encapsulates0hides internal circuitry -rom all users and provides

simple inter-ace -or access by every user.

n java' encapsulation is achieved by binding data and methods in a single entity called class

and hiding data behind methods and allowing the inter-ace with the public methods o- class.

+he -ollowing program demonstrates the concept o- encapsulation.

n the above program data and methods are encapsulated in a class called *ustomer and data

is hidden -rom user by declaring them to private and inter-ace is allowed to setter and getter

methods.

Inheritance$

nheritance is a mechanism by which we can de-ine generali1ed characteristics and behavior

and also create speciali1ed ones. +he speciali1ed ones automatically inherit all the propertieso- generali1ed ones.



nheritance can be achieved in java with the e)tends ,eyword.

(or e)ample in the above diagram' 2ehicle is a generali1ed class with its own characteristics

and behavior' and two3wheeler' -our3wheeler classes are speciali1ed ones which inherit all the

properties o- generali1ed ones li,e $' 4ame' 5icense4umber.

Pol!"orphis"$

+he ability o- an object0operation to behave di--erently in di--erent situations is called

polymorphism.

n the above program the same move67 operation is

behaving di--erently in di--erent situations.

SI&P'E PRO(RA&



+he process o- getting the output -or above program re8uires 9steps.

nter the source code in either editor li,e notepad or $ li,e netbeans or eclipse and save the

program name as De"o#)a*a

*ompile the program using )a*ac co""an -ollowed by $emo.java in command prompt

which generates .class -ile.

)ecute the program using )a*a command -ollowed by $emo which will generates the output.

Description a+out each part o a pro-ra"$

+he -irst line import the classes re8uired -or the program. +he classes re8uired will be in the

subdirectory lang o- main directory java. :ince the above program re8uires print67 method o-

system class the pac,age has to be imported into the program.

+he statements written between 0; ;0 are called multiline comments which will be ignored by

compiler. t e)plains the operation o- program to anyone reading the program.

:ince java is oop language' every java program is written within a class. :o we use class

,eyword -ollowed by class name $emo.

A class code starts with a < and ends with =. n between < = we can write variables and

methods.

main67 is the method which is the starting point -or J2# to start e)ecution.

:ince J2# calls the main67 method there won’t be nothing -or the main67 to return to J2#.

:o it is declared as *oi type.

:ince main67 method should be available to J2# which is an outside program it should be

declared with an access speci-ier pu+lic. Otherwise it is not accessible to J2#.

+he ,eyword static allows main67 to be e)ecuted without creating an object -or class $emo.

+his is necessary because main67 is e)ecuted by J2# be-ore any objects are made.

+o print something to the console output we use :ystem.out.print67 method. :ystem is a class

and out is a variable in it. Print67 method belongs to Print:tream class.

>hen we call out variable Print:tream class object will be created internally. :o we write:ystem.out.print67.

+o print a string to the output we use ? @and passed as a parameter to print67 method.

Ele"ents o a .a*a Pro-ra"



/hitespaces$ n Java' whitespace is a space' tab' or newline.>e use one whitespace

character between each to,en in java.

IDENTIFIERS$ denti-iers are the names given to a variable' class and method. +his helps

to re-er to that item -rom any place in the program. >e can’t start an identi-ier with a digit.

)/ int ) here ) is an identi-ier -or a variable.

'iterals$ A constant value in Java is created by using a literal representation o- it. (or

e)ample' here are some literals/

BB !%.C DE’ ?+his is a test@ Co""ents$ +here are three types o- comments de-ined by Java. :ingle3line' multiline'

documentation comment. $ocumentation comment is used to produce an F+#5 -ile that

documents the program. +he documentation comment begins with a 011 and ends with a 10.

Separators$ n Java' there are a -ew characters that are used as separators. +he separators are

shown in the -ollowing table/

S!"+o

l

Na"e Description

6 7 Parenthesis *ontains parameters in method call &

de-inition. *ontains e)pressions in controlstatements. :urrounds cast type.

< = races $e-ine bloc, o- code -or class' method and

local scopes. Hsed to initiali1e arrays.

I rac,ets Hsed to declare arrays.

:emicolon Hsed to terminate statements.

' *omma :eparates identi-iers in variable declaration.

*hains statements together in -or statement.

. Period :eparates pac,age names -rom sub pac,ages.

:eparate variable or method -rom re-.

variable.

KEY/ORDS$ +here are "B reserved ,eywords currently de-ined in the Java language. +hese

,eywords' combined with the synta) o- the operators and separators' -orm the de-inition o- the

Java language. +hese ,eywords cannot be used as names -or a variable' class' or method.

n addition to the ,eywords' java reserves true, alse and null. *onst and goto ,eywords are

reserved and meant -or -uture use.



OPERATORS

An operator is a symbol which tells the compiler to per-orm a particular operation on

operands. )/ a b. a and b are operands D’ is an operator meant -or addition operation. Cate-ories o operators$

Arithmetic operators

Assignment operator

Hnary operators

Lelational operators

5ogical operators or short circuit operators

oolean operators

itwise operators

+ernary or conditional operator

#ember operator

nstanceo- operator

4ew operator

*ast operator.

Arith"etic operators$

Operator Operation e%a"ple

2 Addition' string

concatenation

MB

:tring sMN@one@'s9N@two@

:tring sNsMs9

3 :ubtraction nt )N'yN9'1 1Ny3)

1 #ultiplication nt )N'yN9'1 1Ny;)

0 $ivision nt )N'yN9'1 1Ny0)

4 #odulus operator

6gives remainder7

nt )N'yN9'1 1Ny)

Assi-n"ent operator$

+his is used to store a value or variable or an e)pression into a variable.

)/ int )N9' yN"' 1

1N ) 1N)09y

Unar! operators$

Operator Operation E%a"ple

3 Hnary minus6negates givenvalue7.

nt )N":ystem.out.print63)77

ncrements a variable value

by .

nt )N"

:ystem.out.print6)7

33 decrements a variable value

by .

nt )N"

:ystem.out.print6)337

Preincrement operator allows incrementation -irst and then other operations are per-ormed.

)/ int )NB

:ystem.out.print6)700 gives result because incrementation -irst happens & then

print operation happens.

Postincrement operator allows other operations to be per-ormed -irst and then incrementationhappens.

)/ int )NB

:ystem.out.print6)700 gives result B because print operation happens



-irst incrementation then happens.

Predecrement operator allows decrementation -irst and then other operations are

per-ormed.

)/ int )NB

:ystem.out.print633)700 gives result ! because decrementation -irst happens & then

print operation happens.

Postdecrement operator allows other operations to be per-ormed -irst and then decrementationhappens.

)/ int )NB

:ystem.out.print6)33700 gives result B because print operation happens

-irst decrementation then happens.

Relational Operators$

+hese are used to per-orm comparison between elements.

Operator Operation e%a"ple

Q6greater than7 valuates to true i-

element greater than

other. Otherwise -alse

:ystem.out.print6MQ97

QN6greater than or e8ual to7 valuates to true i-

element greater than or

e8ual to other. Otherwise

-alse

:ystem.out.print6MQN97

R6lesser than7 valuates to true i-

element lesser than other

element. Otherwise -alse.

:ystem.out.print6MR97

RN6lesser than or e8ual to7 valuates to true i-

element lesser than or

e8ual to other element.otherwise -alse.

:ystem.out.print6MRN97

NN6e8ual to7 valuates to true i- both

elements are e8ual.

otherwise -alse.

:ystem.out.print6MNN97

SN 6not e8ual to7 valuates to true i- both

elements are e8ual.

otherwise -alse.

:ystem.out.print6MSN97

'o-ical Operators$

+his is used to construct compound conditions.

Operator Operation E%a"ple

&&6and operator7 valuates to true i- each simple

condition evaluates to true

otherwise -alse return.

:ystem.out.print6aQb&&

bRc7

TT6or operator7 valuates to true i- any one o-

simple conditions evaluates to

true otherwise -alse return.

:ystem.out.print6aQbTTbRc7

S6not operator7 valuates to true i- condition

evaluates to -alse otherwise true

returns.

:ystem.out.print6S6aQb77

Boolean operators$



+hese operators act on oolean variables and produce oolean type result.

Operators Operation )ample6aNtrue bN-alse7

&6oolean and operator7 Leturns true i- both variables

true. Otherwise -alse returns.

:ystem.out.print6a&b700returns

-alse

T6oolean or operator7 Leturns true i- any variable

is true. Otherwise -alse

returns.

:ystem.out.print6aTb700returns

true

S6oolean not operator7 *onverts true to -alse and

vice3versa.

:ystem.out.print6S6aTb7700returns

-alse

Bit5ise operators$

+hese operators act on individual bits o- a number and produce the appropriate result.

Operators Operation )ample )NB' yN

U6itwise *omplement Operator7 Gives complement o-

a given number

6U)7N3

& 6itwise and Operator 7 Gives i- both bits

are . Otherwise -alse

returns

:ystem.out.print6)&y700returns

BBBBBB

T6itwise or Operator7 Gives i- any o- the

bits are . Otherwise

-alse returns.

:ystem.out.print6)Ty700returns

BBBBBB

V6itwise )or Operator7 Gives i- odd

number o- s present

in input. Otherwise

-alse returns.

:ystem.out.print6)Vy700returns

BBBBBBB

RR6itwise le-t shi-t operator7 :hi-ts bits to the le-twith the speci-ied

number o- times.

:ystem.out.print6)RRM700returnsBBBBBB

QQ6itwise right shi-t operator7 :hi-ts bits to the right

with the speci-ied

number o- times.

:ystem.out.print6)QQM700returns

BBBBBBB

QQQ6itwise 1ero -ill right shi-t

operator7

:hi-ts bits to the right

with the speci-ied

number o- times and

-ill le-t side empty

places with 1eroes. Ternar! Operator or Conitional Operator

+his acts an an alternative -or i- else statement.

:ynta)/ variable Ne)pressionW e)pressionM/e)pression9

)ample/ ma) N 6aQb7W a /b

- e)p evaluates to true e)pM will be e)ecuted. Otherwise e)p9 will be e)ecuted.

&e"+er operator 6#7

+his is used in 9ways.

Hsed when re-er to subpac,age and class o- a pac,age.

)ample/ import java).swing.JOptionPane

Hsed when re-er to variable o- a class or object.

)ample/ :ystem.out

Hsed when re-er to method o- a class or object.

)ample/ #ath.s8rt6M97



instanceo Operator

+his is used to test i- an object belongs to a 6class or inter-ace7 or not.

:ynta)/ oolean variableN object instanceo- class

)ample/ oolean )N custobj instanceo- customer

Ne5 operator

new operator is o-ten used to create objects to classes.

:ynta)/ classname objNnew classname67

)ample/ customer custobjNnew customer67 Cast operator

*ast operator is used to convert one data type into another data type.

:ynta)/ datatype target3varN6target3datatype7variable

)ample/ int )

-loat yNM."CX%

)N6int7y

Priorit! o operators

n an e)pression some o- the operators will e)ecute -irst and some operators will e)ecute ne)t.

+o determine which operators e)ecute -irst priority will be assigned to operators.

+he priority is as -ollows.

priorit! operators

st 67 ' I

Mnd ' 33

9rd ;' 0'

th ' 3

"th Lelational operators

Cth oolean and bitwise

operators

Xth 5ogical operators

%th +ernary operator

!th Assignment operator

DATATYPES

$atatype is an identi-ied type -or any data being used in a program.

+his is used to determine the -ollowing.

o +ype o- data stored in a variable

o 4o o- bytes it occupies in memory

o Lange o- data.

n java datatypes are divided into M categories.

• Primitive datatypes

• 4on primitive datatypes

Hnder primitive datatypes we have % datatypes. Hnder non primitive we have class, arra!,

interace#



+he -ollowing table shows various datatypes with their details.

*ategory $atatype 4o.o- bytes

occupied

#in3ma) value $e-ault

value

e)ample

nteger type

byte byte 63MX73 6MX37 B byte bNB

short Mbytes 63M"73 6M"37 B short sNM9"

int bytes 63M973 6M937 B int iNM9"CCC

long %bytes 63MC973 6MC937 B long lN9M"CX%!

(loating type-loat bytes 69.e3B9%73 69.eB9%7 B.B- (loat -N9."-

double %bytes 69.e39B%73 69.e9B%7 B.Bd double dN9.M9d

+e)tual type char Mbytes 3 C""9" 4ull char chN’)’

5ogical type boolean bit 3 -alse boolean bNtrue

• (loat can represent upto X digits accurately a-ter decimal point' whereas double can represent

upto " digits accurately a-ter decimal point.

• char datatype can support C""9C characters including all human language characters which isthere in the Hnicode system.

8ARIAB'E

A variable is an identi-ier -or the data in the program.

t holds data in a program

t is named location in memory whose value changes during program e)ecution.

+he type o- data stored in the variables can be speci-ied with datatype.

S!nta%$ datatype variable3nameNvalue

E%a"ple$ int )NM9"C

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Unit-I JAVA