This document provides an overview of Java including its history, versions, key features, and basic programming concepts. It describes how Java was originally called Oak and later renamed to Java in 1995. It also lists the main Java versions from 1995 to 2011. Additionally, it defines Java as a platform independent language and outlines some of its common uses. The document proceeds to explain Java's main features such as being simple, object-oriented, platform independent, secure, portable, dynamic, high performance, and multithreaded. It also includes examples of a simple Java program, variables, and packages.

2. contents
History Of Java
Java Versions
What is Java
Java Features
Simple java program
Understanding first java program
How to set path of JDK in windows
Variable
Package

3. History of java
James Gosling initiated the Java language project in June 1991.
Firstly, it was called "Greentalk" by James Gosling and file extension was .gt.
After that, it was called Oak and was developed as a part of the Green project.
 Why Oak? Oak is a symbol of strength and chosen as a national tree of many countries like U.S.A.,
France, Germany, Romania etc.
In 1995, Oak was renamed as "Java" because it was already a trademark by Oak Technologies.

4. Java Versions
There are many java versions like as::
1. JDK Alpha and Beta (1995)
2. JDK 1.0 (23rd Jan, 1996)
3. JDK 1.1 (19th Feb, 1997)
4. J2SE 1.2 (8th Dec, 1998)
5. J2SE 1.3 (8th May, 2000)
6. J2SE 1.4 (6th Feb, 2002)
7. J2SE 5.0 (30th Sep, 2004)
8. Java SE 6 (11th Dec, 2006)
9. Java SE 7 (28th July, 2011)

5. What is java
Java is a programming language and a platform independent language.
Platform :-Any hardware or software environment in which a program runs, known
as a platform. Since Java has its own Runtime Environment (JRE) and API, it is called
platform
According to Sun, 3 billion devices run java. There are many devices where java is
currently used. Some of them are as follows:
1. Desktop Applications such as acrobat reader, media player, antivirus etc.
2. Web Applications such as irctc.co.in, javatpoint.com etc.
3. Enterprise Applications such as banking applications.
4. Mobile
5. Embedded System
6. Smart Card
7. Robotics
8. Games etc.

6. Features of java
 Simple
 Object-oriented
 Platform indepented
 Secured
 Portable
 Dynamic
 High performance
 Multithreaded

7. simple
According to sun, Java language is simple .
Syntax is based on C++ (so easier for programmers to learn it
after C++).
Removed many confusing and/or rarely-used features e.g.,
explicit pointers, operator overloading etc.
No need to remove unreferenced objects because there is
Automatic Garbage Collection in java.

8. Object-oriented
Object-oriented programming(OOPs) is a methodology that
simplify software development and maintenance by providing
some rules.
We can do program with the help of object.
Basic concepts of OOPs are:
1.Object
2.Class
3.Inheritance
4.Polymorphism
5.Abstraction
6.Encapsulation

9. Platform indepented
 A platform is the hardware or software environment in which a
program runs.
 There are two types of platforms, software-based and hardware-based.
 Java provides software-based platform.
.class
jvm
Windows os
Linux os
MAC os
 JVM:- java virtual machine
 .class:- byte code

10. secured
Java is secured because:
•No explicit pointer & operator overloading.
•Programs run inside virtual machine sandbox.
multithreaded
Multithreaded means handling multiple tasks simultaneously.
Java supports multithreaded programs. This means that we need not wait for the
application to finish one task before beginning another.

11. portable
 Java is portable because we can move the bytecode to any platform as well as
run successfully.

12. Simple java program
class Simple{
public static void main(String args[]){
System.out.println(“Amlendu kumar Dubey")
}
}
save this file as Simple.java
Run Program
To compile: javac Simple.java
To execute: java Simple
Output:- Amlendu kumar Dubey

13. Understanding first java program
 class is used to declare a class in java.
 public is an access modifier which represents visibility, it means it is visible to
all.
 static is a keyword, if we declare any method as static, it is known as static
method. The core advantage of static method is that there is no need to create
object to invoke the static method. The main method is executed by the JVM,
so it doesn't require to create object to invoke the main method. So it saves
memory.
 void is the return type of the method, it means it doesn't return any value.
 main represents start-up of the program.
 String[] args is used for command line argument.
 System.out.println() is used print statement.

14. How to set path of JDK in windows
 Path is required for using tools such as javac, java etc. If you are saving the
java file in jdk/bin folder, path is not required. But If you are having your java
file outside the jdk/bin folder, it is necessary to set path of JDK.
 There are two ways to set path of JDK:
1. temporary
2. permanent
1)Setting temporary Path of JDK in Windows:
For setting the temporary path of JDK, you need to follow these steps:
•Open command prompt
•copy the path of bin folder
•write in command prompt: set path=copiedpath

15. How to set path of JDK in windows
2.)Setting Permanent Path of JDK in Windows:
For setting the permanent path of JDK, you need to follow these steps:
Go to MyComputer properties -> advanced tab -> environment variables
-> new tab of user variable -> write path in variable name -> write path
of bin folder in variable value -> ok -> ok -> ok

16. Variable
 Variable is a name of memory location.
 There are three types of variables:
 local, instance and static.

17. Variable
local variable :- A variable that is declared inside the method is called
local variable.
Instance variable:-A variable that is declared inside the class but outside
the method is called instance variable . It is not declared as static.
Static variable:-A variable that is declared as static is called static
variable. It cannot be local.

18. Example of variable
class variable
{
int x; //Instance variable
static int y; //Static variable
void sum() // Non Static method
{
int x=5; // local variable
}
public static void main(String args[]) // Static
method
{
System.out.println("Example of variable");
}
}
Run Program

19. Package
A package is a group of similar types of classes, interfaces and sub-packages.
More importantly, it helps improve re-usability .
 Package is used to categorize the classes and interfaces so that they
can be easily maintained.
 Package provids access protection.
 Package removes naming collision.

20. Example of package::
package p1;
class c1
{
public void m1()
{
System.out.println("method m1 of class c1");
}
public static void main(String arg[])
{
c1 obj=new c1();
obj.m1();
}
}
Save the file as : demo.java
To Compile: javac -d . demo.java
To Run: java p1.c1