Introduction To JAVA

By:

Anirudh Rajan

Dilsahib Singh

Kamal Kumar Vishwakarma

Sourabh Sharma

Context

• History
• Features
• JVM, JDK and JRE
• Array
• Namming Convention

History

• James Gosling, Mike Sheridan and Patrick Naughton (1991) 
• Green Team
• Greentalk (.gt) by James Gosling
• Oak (Green Project) --> Symbol of Strength
• 1995 --> Oak to JAVA

Why name JAVA

• Reflect the essence of Technology
• "JAVA was one of the top choices along with Silk" - James Gosling
• Java Island -> First Coffee -> Java coffee
• Developer - James Gosling at Sun Microsystems (sub. ORACLE Corporation)
• Time Magazine (1995) - "JAVA one of the 10 Best Products of 1995"
• JDK 1.0 - Jan 23, 1996

Features

• Simple
• Object Oriented
• Platform Independent
• Secure
• Robust
• Architecture Neutral
• Portable
• Dynamic
• Interpreted
• High Performance
• Multithreaded
• Dustributed

Simple

• Syntax based on C++
• Removed many confusing or rarely-used features
  • explicit Pointers
  • operator overloading
• Automatic Garbage Collection

Object-Oriented

• Different type of objects that incorporates both data and behaviour
• Object-Oriented Programming is a methodology
• Basic concepts
  • Object
  • Class
  • Inheritance
  • Polymorphism
  • Abstraction
  • Encapsulation

Platform Independent

• Two Types
  • Hardware - based
  • Software - based
• JAVA provides software - based Platform
• JAVA code can run on multiple platforms(Windows, Linux, etc.)
• Java code is compiled by the compiler and converted into bytecode.
• Write Once and Run Anywhere (WORA)

Secured

• No Explicit Pointer
• Program run inside virtual machine sandbox
• Classloader
• Bytecode Verifier
• Security Manager
  • SSL
  • JAAS
  • cryptography

Robust

• Strong
• Lack of pointers that avoids security problem
• Automatic Garbage collection
• Exception handling and type checking mechanism

Architecture-Neutral

• No Implementation Dependent Features

Portable

• Carry java bytecode to any platform

High - Performance

• Java is faster then traditional interpretation

Distributed

• RMI and EJB are used
• Access files by calling the methods from any machine

Multi - Threaded

• Deal with many tasks by defining multiple threads
• Share same memory
  • Multimedia
  • Web Application

JVM, JDK and JRE

JVM

• Abstract Machine
• Run Time Environment
• Tasks
  • Loads code
  • Verifies code
  • Executes code
  • Provides runtime environment

• JVM, JRE and JDK are platform dependent

JDK

• Contains JRE + development tools

JRE

• Provide Run Time Environment
• Implementation of JVM
• Contains set of libraries + other files that JVM uses at runtime

ARRAY in JAVA

• Collection of similar type of elements
• Contiguous memory location
• Java array is an object the contains elements of similar data type

Advantage

• Code Optimization
• Random Access

Disadvantage

• Size Limit

Types of Array

• Single-Dimention Array
• Multi-Dimention Array

Single-Dimention Array

Syntax :

1. dataType[] arr;  
2. dataType []arr;   
3. dataType arr[];  

Instantiation of an Array

Syntax :

1. arrayRefVar=new datatype[size]; 

Declaration, Instantiation and Initialization

Syntax :

1. int a[]={33,3,4,5};

Multidimensional array

Syntax :

1. dataType[][] arrayRefVar;   
2. dataType [][]arrayRefVar;   
3. dataType arrayRefVar[][];  
4. dataType []arrayRefVar[]; 

Instantiate Multidimensional Array

Syntax :

1. int[][] arr=new int[3][3];

Initialize Multidimensional Array

Syntax :

arr[0][0]=1;

arr[0][1]=2;

arr[0][2]=3;

arr[1][0]=4;

arr[1][1]=5;

arr[1][2]=6;

arr[2][0]=7;

arr[2][1]=8;

arr[2][2]=9;