Java Basic PART 1




why should you learn java



Java is easy to learn 

java is object oriented

java has rich API

powerful developement tools


GREAT COLLECTION OF OPEN SOURCE LIBRARIES

Wonderful community support

Java is FREE

Excellent documentation support - Javadocs




Java is Platform Independent

write once run anywhere



Java is Everywhere

Desktop, mobile,  card, and so Java programmers,
 organizations



Introduction 

Developed By : James Gosling 

Owner : Sun Microsystems 

Released in : 1995 

Stable Release : Java Standard Edition 7 (1.7.0) 

 OS : Cross Platform (Multi Platform)

 Extensions : .java, .class, .jar


JAVA Platform

 JAVA Platform It is Platform Independent. It compiles Java language code in Java bytecode , not in Machine code. A major benefit of using bytecode is porting.



Virtual machine 

ByteCode




Automatic Memory Management




JAVA Syntax

Commenting Methods

// /*  *//***@author yuri...*/ 


A Simple JAVA Program

class Hello {
    public static void main(String args []) 
       {
     System.out.println (“Hello"+                               "World”);        } 
}


Some abbreviations

 JDK : JAVA Development Kit

 JVM : JAVA Virtual Machine 

JRE : JAVA Runtime Environment 

javac : JAVA Compiler


 JVM : JAVA Virtual Machine 

 KVM : Kilobyte Virtual Machine 

CVM : Card Virtual Machine 

DVM : Delwik Virtual Machine 

Points to be remembered

Java programs need to be compiled only once.

 When a class is defined as public, class name and file name must be same. 

”;” can be put anywhere before a new statement. 




Java does not support operator overloading.


 Operator “+” is by default overloaded in JAVA.

Objectives

Class
Objects
 Identifiers
Methods
Encapsulation
 inheritance
polymorphism
Constructors



Class

Template,

State and behaviour of object at run time, Abstract class ,Final class


Interface

 A 100% abstract class,

A contact for what a implementing class can do.

Behavioural purposes

Class can implement multiple interfaces



Variables

Primitives, Reference, Local variables Arrays, Final variables ,Transient


Methods

static

abstract

final




Encapsulation

 Keep data protected

Keep services open

Setters and getters method



Inheritance

 Re-usability

Sometimes we have no implementation

Is-a vs has-a relationship


Polymorphism

 Overloading

Overridding



Constructors

 Need?

Default constructor

Constructor overloading

Constructor calls in inheritance tree


operators

postfix     expr++ expr--
unary     ++expr --expr +expr -expr ~ !
multiplicative     * / %
additive     + -

equality     == !=

relational     < > <= >= instanceof

More operators

shift     << >> >>>
bitwise AND     &
bitwise exclusive OR     ^
bitwise inclusive OR     |
logical AND     &&
logical OR     ||
ternary     ? :
assignment     = += -= *= /= %= &= ^= |= <<= >>= >>>=


.equals() 

VS

==


exemple

 
String user1 = "YuriLz";
String user2 = "YuriLz";
String user3 = "Yuritta";
String user4 = new
String("YuriLz");

String user5 = new String();
String user6 = new String();




 user5 = "YuriLz";
user6 += "YuriLz";



OUTSTREAM

 System.out.println( (user1==user2)? "Equal" : "Not Equal" );
System.out.println( (user3==user2)? "Equal" : "Not Equal" );
System.out.println( (user1==user2)? "Equal" : "Not Equal" );
System.out.println( (user4==user2)? "Equal" : "Not Equal" );
System.out.println( (user5==user2)? "Equal" : "Not Equal" );
System.out.println( (user5==user6)? "Equal" : "Not Equal" );
System.out.println( (user5.equals(user2))? "Equal" : "Not Equal" );
System.out.println( (user5.equals(user3))? "Equal" : "Not Equal" );



(user1==user2)? "Equal" : "Not Equal" );
(user3==user2)? "Equal" : "Not Equal" );
(user4==user2)? "Equal" : "Not Equal" );
(user5==user2)? "Equal" : "Not Equal" );
(user5==user6)? "Equal" : "Not Equal" );
(user5.equals(user2))? "Equal" : "Not Equal" );
(user5.equals(user3))? "Equal" : "Not Equal" );

OUPUT


~$ javac StringsExemple.java~$ java StringsExemple
Equal
Not Equal
Not Equal
Equal
Not Equal
Equal
Not Equal 



THANKS!


JAVA BASIC

By Yuri Laaziz

JAVA BASIC

JAVA BASIC I, last update mai 2014

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