advanced java lecture-1

8/10/2019 Advanced Java Lecture-1

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1

Lecture 1: Overview of Java


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2

Object OrientedLanguages??

Object Oriented Languages arebased upon Classes and Objects.

Helps us to create Real WorldApplicationsvery easily


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3

JavasHistory

Developed by Sun Microsystems (ames!osling"

# general$purpose object$oriented language

Oa% $ &n 1''1 ava $ &n 1''

Hot ava ) *irst ava +nabled ,ro-ser

etscape avigator ) &n 1'' to incorporateava /ec0nology

,ased on

Designed 4or easy 5eb&nternet applications


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6

Javas Magic : yte Code

/0e %ey t0at allo-s java to solvebot0 t0e security and t0e portabilityproblems

!ource Code yte Code

Output

Co"piler

(avac" J#M

(ava 7un/ime+nvironment"


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ava8rogram

9irtualmac0ine

avaompiler

Mac0inecode

ava&nterpreter

,yte code

Sourcecode

,yte ode

9irtual Mac0ine 7eal Mac0ine


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:

yte Code

/ranslating a java program into bytecode0elps ma%es it muc0 easier to run aprogram in a -ide variety o4 environments.

,yte ode is interpreted (-0ic0 0elps toma%e it secure"

&nterpretation is slo-er but t0e use o4bytecode enables t0e java run$time systemto e;ecute programs muc0 4aster t0an youmig0t e;pect.


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Java Class Lifecycle

Source File

(.java)

Class File

(.class)

Compiler(javac)

Java Virtual Machie (JVM)

ClassLoa!er

"#teco!e Verifier

$terpreter

Securit# Maa%er

Operati% S#stem

&etwor'

or

File S#stem

securit# %atewa#


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oats=c0aractersE

O4ten -ant to 0ave an array o4

objects Students= ,oo%s= Loans EE

eed to 4ollo- 3 steps.


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Declaring t0e #rray

1. Declare t0e array

Student sPQF t0is declares s as an object

2 .reate t0e array sPQ G ne9StudentP1AQF

t0is sets up 1A spaces in memory t0at can0old re4erences to Student objects

3. reate Student objects and addt0em to t0e array sPAQ G ne9Student("F


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#rrays are @;ed lengt0

Lengt0 is speci@ed at create time

&n java= all arrays store t0eallocated si?e in a variablenamed lengt0J.

5e can access t0e lengt0 o4arrays as arrayame.lengt0

e.%. it stu!ets.le%th()/ 00 G

#rrays ) Lengt0


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Strings in java


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Strings represent a seBuence o4 c0aracters./0e

easiest -ay to represent a seBuence o4c0aracters

in java is by using a c0aracter array.

+;ample0ar c0ar#rrayPQGne- c0arP6QF

c0ar#rrayPAQGTjUF

c0ar#rrayP1QGTaUFc0ar#rrayP2QGTvUF

c0ar#rrayP3QGTaUF


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Strings may be declared and created as 4ollo-s

String stringameF

stringameGne- String(stringJ"F+g

String @rstnameF

@rstnameGne- String(#nilJ"F orString @rstnameGne- String(anilJ"F


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Li%e arrays= it is possible to get t0elengt0 o4

string using t0e lengt'met0od o4 Strinclass

int [email protected]("F

ava strings can be concatenated usingt0e

Operator. +g=

String 4ullameGname1name2F J J J


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String arrays

5e can create and use arrays t0at containstrings.

/0e statement

String item#rrayPQGne- StringP3QF

5ill create an item#rray o4 si?e 3 to 0oldt0ree string

constants


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String met0ods

String class de@nes a number o4 met0odst0at allo- us to

accomplis0 a variety o4 stringmanipulation tas%s


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S2Gs1.toLo-eraseF converts string s1 tolo9ercase

S2Gs1.topperaseF converts string s1 to

uppercaseS2Gs1.replace(T;U= UyU"F replace all appearance o& ,

9it' y

S1.eBuals(s2"F returns true i& s1 is e;ual to s3

S1.eBuals&gnorease(s2"F returns true i& s1

advanced java lecture-1

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