Introduction to Java · The Java Tutorial, 4th Edition, Prentice Hall PTR, 2006 Louridas...

IntroductionThe Basics

Programming in JavaFurther Reading

Introduction to Java

Panagiotis Louridas [email protected]

DIEPTELO

Louridas Introduction to Java



Outline

1 IntroductionA Bit of HistoryThe Java Runtime EnvironmentJava Programs

2 The BasicsJava Compared to Other LanguagesJava PrinciplesObject Orientation in a Nutshell

3 Programming in JavaHello WorldGraphical Hello WorldGraphical Hello World with InteractionCollections

4 Further Reading




A Bit of HistoryThe Java Runtime EnvironmentJava Programs

A Bit of History

Bill Joy, 1990: Sun Aspen Smallworks

James Gosling, 1992: FirstPerson. Work on “C++ minusminus”

Demise of Apple Newton: efforts shift to interactive TV (ITV)

Oak: a language for ITV

1993: Oak becomes Java





The Java Runtime Environment

Learning Java, 3rd Edition, O’Reilly, 2005





Types of Java Programs

Applets

j2me

Desktop applications

Server applications

Network applications

. . .




Java Compared to Other LanguagesJava PrinciplesObject Orientation in a Nutshell

Java Compared to Other Languages






Java Principles

Simplify

Object Orientation

Type safety

Runtime information

Error handling

Threads

Collections





What is an Object

An object is an entity containing data and code, or state andbehaviour

The Java Tutorial, 4th Edition, Prentice Hall PTR, 2006





A class example

c l a s s B i c y c l e {

i n t cadence = 0 ;i n t speed = 0 ;i n t g e a r = 1 ;

void changeCadence ( i n t newValue ) {cadence = newValue ;

}

void changeGear ( i n t newValue ) {g e a r = newValue ;

}

void speedUp ( i n t i n c r e m e n t ) {speed = speed + i n c r e m e n t ;

}

void a p p l y B r a k e s ( i n t decrement ) {speed = speed − decrement ;

}

void p r i n t S t a t e s ( ) {System . out . p r i n t l n ( ” cadence : ”+cadence+” speed : ”+speed+” g e a r : ”+g e a r ) ;

}}






A Bicycle Demo

c l a s s BicycleDemo {pub l i c s t a t i c void main ( S t r i n g [ ] a r g s ) {

// Crea te two d i f f e r e n t B i c y c l e o b j e c t sB i c y c l e b i k e 1 = new B i c y c l e ( ) ;B i c y c l e b i k e 2 = new B i c y c l e ( ) ;

// Invoke methods on tho s e o b j e c t sb i k e 1 . changeCadence ( 5 0 ) ;b i k e 1 . speedUp ( 1 0 ) ;b i k e 1 . changeGear ( 2 ) ;b i k e 1 . p r i n t S t a t e s ( ) ;

b i k e 2 . changeCadence ( 5 0 ) ;b i k e 2 . speedUp ( 1 0 ) ;b i k e 2 . changeGear ( 2 ) ;b i k e 2 . changeCadence ( 4 0 ) ;b i k e 2 . speedUp ( 1 0 ) ;b i k e 2 . changeGear ( 3 ) ;b i k e 2 . p r i n t S t a t e s ( ) ;

}}






Inheritance


c l a s s MountainBike extends B i c y c l e {

// new f i e l d s and methods d e f i n i n g a mountain b i k e// would go he r e

}





InterfacesInterfaces are like classes, but without implementation

i n t e r f a ce D r i v e a b l e {boolean s t a r t E n g i n e ( ) ;void s t o p E n g i n e ( ) ;f l o a t a c c e l e r a t e ( f l o a t acc ) ;boolean t u r n ( D i r e c t i o n d i r ) ;

}

c l a s s Automobi le implements D r i v e a b l e {. . .pub l i c boolean s t a r t E n g i n e ( ) {

i f ( notTooCold )e n g i n e R u n n i n g = true ;. . .

}

pub l i c void s t o p E n g i n e ( ) {e n g i n e R u n n i n g = f a l s e ;

}

pub l i c f l o a t a c c e l e r a t e ( f l o a t acc ) {. . .

}

pub l i c boolean t u r n ( D i r e c t i o n d i r ) {. . .

}. . .

}





Hello WorldGraphical Hello WorldGraphical Hello World with InteractionCollections

Hello World

pub l i c c l a s s H e l l o J a v a {pub l i c s t a t i c void main ( S t r i n g [ ] a r g s ) {

System . out . p r i n t l n ( ” H e l l o , Java ! ” ) ;}

}





Graphical Hello World

import j a v a x . swing . ∗ ;

pub l i c c l a s s H e l l o J a v a S w i n g {pub l i c s t a t i c void main ( S t r i n g [ ] a r g s ) {

JFrame frame = new JFrame ( ” H e l l o , Java ! ” ) ;J L a b e l l a b e l = new J L a b e l ( ” H e l l o , Java ! ” ,

J L a b e l . CENTER ) ;f rame . add ( l a b e l ) ;f rame . s e t S i z e (300 , 3 0 0 ) ;f rame . s e t V i s i b l e ( true ) ;

}}






Graphical Hello World with InteractionThe main class

import j a v a . awt . ∗ ;import j a v a . awt . e v e n t . ∗ ;import j a v a x . swing . ∗ ;

pub l i c c l a s s H e l l o J a v a 2 {pub l i c s t a t i c void main ( S t r i n g [ ] a r g s ) {

JFrame frame = new JFrame ( ” H e l l o J a v a 2 ” ) ;f rame . getContentPane ( )

. add (new Hel loComponent ( ” H e l l o , Java ! ” ) ) ;f rame . s e t D e f a u l t C l o s e O p e r a t i o n ( JFrame . EXIT ON CLOSE ) ;f rame . s e t S i z e (300 , 3 0 0 ) ;f rame . s e t V i s i b l e ( true ) ;

}}






Graphical Hello World with InteractionThe HelloComponent class

c l a s s Hel loComponent extends JComponentimplements M o u s e M o t i o n L i s t e n e r {

S t r i n g theMessage ;i n t messageX = 125 , messageY = 9 5 ; // Coo rd i n a t e s o f the message

pub l i c Hel loComponent ( S t r i n g message ) {theMessage = message ;addMouseMot ionL i s tener ( t h i s ) ;

}

pub l i c void paintComponent ( G r a p h i c s g ) {g . d r a w S t r i n g ( theMessage , messageX , messageY ) ;

}

pub l i c void mouseDragged ( MouseEvent e ) {// Save the mouse c o o r d i n a t e s and pa i n t the message .messageX = e . getX ( ) ;

messageY = e . getY ( ) ;r e p a i n t ( ) ;

}

pub l i c void mouseMoved ( MouseEvent e ) { }}






Sort Arguments

import j a v a . u t i l . ∗ ;

pub l i c c l a s s FindDups {pub l i c s t a t i c void main ( S t r i n g [ ] a r g s ) {

Set<S t r i n g > s = new HashSet<S t r i n g >() ;f o r ( S t r i n g a : a r g s )

i f ( ! s . add ( a ) )System . out . p r i n t l n ( ” D u p l i c a t e d e t e c t e d : ” + a ) ;

System . out . p r i n t l n ( s . s i z e ( ) +” d i s t i n c t words : ” + s ) ;

}}






Shuffle Arguments

import j a v a . u t i l . ∗ ;

pub l i c c l a s s S h u f f l e {pub l i c s t a t i c void main ( S t r i n g [ ] a r g s ) {

L i s t <S t r i n g > l i s t = A r r a y s . a s L i s t ( a r g s ) ;C o l l e c t i o n s . s h u f f l e ( l i s t ) ;System . out . p r i n t l n ( l i s t ) ;

}}





Further Reading

S. Zakhour, S. Hommel, J. Royal, I. Rabinovitch, T. Risser, M.Hoeber, The Java Tutorial: A Short Course on the Basics, 4th

edition, Prentice Hall PTR, 2006. Online version at: http://java.sun.com/docs/books/tutorial/index.html

J. Knudsen, P. Niemeyer, Learning Java, 3rd edition, O’ Reilly,2005.

B. Eckel, Thinking in Java, 4th edition, Prentice Hall PTR,2006.


http://java.sun.com/docs/books/tutorial/index.html

http://java.sun.com/docs/books/tutorial/index.html

Introduction to Java · The Java Tutorial, 4th Edition, Prentice Hall PTR, 2006 Louridas...

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