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Introduction of Java

Java is object oriented programming language.

What is Java?

Java is object oriented programming language.

The Java programming language was developed by James Gosling from Sun in 1995.

Features of Java.

  • Simple
  • Portable
  • Object oriented
  • Platform Independent
  • Secured
  • Robust
  • Architecture neutral
  • Interpreted
  • High performance
  • Multi threaded
  • Distributed
  • Dynamic

What is OOPS?

OOPS is a programming approach which revolvs around the concept of "object".
Any entity in the system that can be defined as a set of properties and set of operations performed using entity's property set, is known as object.'

  • Encapsulation
  • Data hiding
  • Abstraction
  • Polymorphism
  • Inheritance


variables are the names of memory locations where we store data.
variable name is any combination of alphabet (a to z or A to Z), digit(0 to 9) and underscore (_).

Rules for naming variables in C#

  • First character must be alphabet or underscore(_).
  • no commas, blanks allowed
  • no special symbol other than (_) allowed
  • variables names are case sensitive we must create meaningful variables name in our programms.

Types of variables

  • local
  • global
  • static

local variable

local variable can declare and defineinside function of constructor block. It cannot access outside of function block.

global variable

global variable can declare out side of function block. global variable can acces any where in program, if it is public.

static variable

static variable can declare at the class level. No need to create an object to access static variable.


Keywords are reserved words, whose meaning is already known to the compiler.

abstract assert boolean break byte case
catch char class continue const default
do double else enum exports extends
final finally float for goto if
implements import instanceof int interface long
module native new package private protected
public requires return short static strictfp
super switch synchronized this throw throws
transient try var void volatile while


comments are used to clarify something about the program in plain languagqe.

There are two types of comments in C#.

  • Single line comment.
  • Multi line comment.