1 .java basic

 Java - What, Where and Why?
 What is Java
 Where Java is used
 Java Applications

What is Java
 Java is a programming language and
a platform.
 Java is a high level, robust, secured and
object-oriented programming language.
 Platform: Any hardware or software
environment in which a program runs, is
known as a platform. Since Java has its
own runtime environment (JRE) and API, it
is called platform.

Java Example
 Let's have a quick look at java
programming example. A detailed
description of hello java example is given
in next page.
 class Simple{
 public static void main(String args[]){
 System.out.println("Hello Java");
 }
 }

Where it is used?
 According to Sun, 3 billion devices run java. There are
many devices where java is currently used. Some of them
are as follows:
 Desktop Applications such as acrobat reader, media
player, antivirus etc.
 Web Applications such as irctc.co.in, javatpoint.com etc.
 Enterprise Applications such as banking applications.
 Mobile
 Embedded System
 Smart Card
 Robotics
 Games etc.

Types of Java Applications
 There are mainly 4 type of applications
that can be created using java
programming:
 1) Standalone Application :-It is also known
as desktop application or window-based
application. An application that we need
to install on every machine such as media
player, antivirus etc. AWT and Swing are
used in java for creating standalone
applications.

2) Web Application
An application that runs on the server side
and creates dynamic page, is called web
application. Currently, servlet, jsp, struts, jsf etc.
technologies are used for creating web applications
in java.
3) Enterprise Application
An application that is distributed in nature,
such as banking applications etc. It has the
advantage of high level security, load balancing and
clustering. In java, EJB is used for creating enterprise
applications.

 4) Mobile Application
An application that is created for
mobile devices. Currently Android and Java
ME are used for creating mobile
applications.

History of Java
1. Brief history of Java
2. Java Version History

1. Brief history of Java
 Java history is interesting to know. The history
of java starts from Green Team. Java team
members (also known as Green Team),
initiated a revolutionary task to develop a
language for digital devices such as set-top
boxes, televisions etc.
 For the green team members, it was an
advance concept at that time. But, it was
suited for internet programming. Later, Java
technology as incorporated by Netscape.

Brief history of Java
 Currently, Java is used in internet programming,
mobile devices, games, e-business solutions etc.
There are given the major points that describes the
history of java.
1) James Gosling, Mike Sheridan, and Patrick
Naughtoninitiated the Java language project in June
1991. The small team of sun engineers called Green
Team.

2) Originally designed for small,
embedded systems in electronic appliances
like set-top boxes.
3) Firstly, it was called "Greentalk" by James
Gosling and file extension was .gt.
4) After that, it was called Oak and was
developed as a part of the Green project.

 5) Why Oak? Oak is a symbol of strength
and choosen as a national tree of many
countries like U.S.A., France, Germany,
Romania etc.
 6) In 1995, Oak was renamed
as "Java" because it was already a
trademark by Oak Technologies.

 7) Why they choosed java name for java
language? The team gathered to choose a new
name. The suggested words were "dynamic",
"revolutionary", "Silk", "jolt", "DNA" etc. They wanted
something that reflected the essence of the
technology: revolutionary, dynamic, lively, cool,
unique, and easy to spell and fun to say.
 According to James Gosling "Java was one of the
top choices along with Silk". Since java was so
unique, most of the team members preferred java.
 8) Java is an island of Indonesia where first coffee
was produced (called java coffee).

 9) Notice that Java is just a name not an
acronym.
 10) Originally developed by James
Gosling at Sun Microsystems (which is now
a subsidiary of Oracle Corporation) and
released in 1995.
 11) In 1995, Time magazine called Java
one of the Ten Best Products of 1995.
 12) JDK 1.0 released in(January 23, 1996).

2. Java Version History
 There are many java versions that has been released.
Current stable release of Java is Java SE 8.
 JDK Alpha and Beta (1995)
 JDK 1.0 (23rd Jan, 1996)
 JDK 1.1 (19th Feb, 1997)
 J2SE 1.2 (8th Dec, 1998)
 J2SE 1.3 (8th May, 2000)
 J2SE 1.4 (6th Feb, 2002)
 J2SE 5.0 (30th Sep, 2004)
 Java SE 6 (11th Dec, 2006)
 Java SE 7 (28th July, 2011)
 Java SE 8 (18th March, 2014)

Features of Java
 Simple
 Object-Oriented
 Platform Independent
 secured
 Robust
 Architecture Neutral
 Portable
 High Performance
 Distributed
 Multi-threaded

Simple:
According to Sun, Java language is simple because:
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.

Object-oriented
Object-oriented means we organize our software as a combination of
different types of objects that incorporates both data and behaviour.
Object-oriented programming(OOPs) is a methodology that simplify
software development and maintenance by providing some rules.
Basic concepts of OOPs are:
1.Object
2.Class
3.Inheritance
4.Polymorphism
5.Abstraction
6.Encapsulation

Platform Independent
 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. The Java platform
differs from most other platforms in the sense
that it's a software-based platform that runs
on top of other hardware-based platforms.It
has two components:
 Runtime Environment
 API(Application Programming Interface)

Platform Independent cont… Java code can be run Java code can be on
multiple platforms

Platform Independent cont..
 e.g.Windows,Linux,Sun Solaris,Mac/OS
etc. Java code is compiled by the
compiler and converted into
bytecode.This bytecode is a platform
independent code because it can be run
on multiple platforms i.e. Write Once and
Run Anywhere(WORA).

Secured
Java is secured because:
•No explicit pointer
•Programs run inside virtual machine sandbox.

Secured•Classloader- adds security by separating the package for the
classes of the local file system from those that are imported from
network sources.
•Bytecode Verifier- checks the code fragments for illegal code that
can violate access right to objects.
•Security Manager- determines what resources a class can access
such as reading and writing to the local disk.
These security are provided by java language. Some security can
also be provided by application developer through
SSL,JAAS,cryptography etc.

Robust
 Robust simply means strong. Java uses
strong memory management. There are
lack of pointers that avoids security
problem. There is automatic garbage
collection in java. There is exception
handling and type checking mechanism
in java. All these points makes java robust.

Architecture-neutral
• There is no implementation dependent features e.g. size of
primitive types is set.

Portable
• We may carry the java bytecode to any platform.

High-performance
 Java is faster than traditional
interpretation since byte code is "close" to
native code still somewhat slower than a
compiled language (e.g., C++)

Distributed
 We can create distributed applications in
java. RMI and EJB are used for creating
distributed applications. We may access
files by calling the methods from any
machine on the internet.

Multi-threaded
 A thread is like a separate program,
executing concurrently. We can write
Java programs that deal with many tasks
at once by defining multiple threads. The
main advantage of multi-threading is that
it shares the same memory. Threads are
important for multi-media, Web
applications etc.

Simple Program of Java
 Software Requirements
 Creating Hello Java Example
 Resolving javac is not recognized problem

Simple Program of Java
 We can write a simple hello java program
easily after installing the JDK.
 To create a simple java program, you
need to create a class that contains main
method. Let's understand the requirement
first.

Requirement for Hello Java
Example
 For executing any java program, you
need toinstall the JDK if you don't have
installed it, download the JDK and install
it.
 set path of the jdk/bin directory.create
the java program
 compile and run the java program

Creating hello java example
class Simple{
public static void main(String args[]){
System.out.println("Hello Java");
}
}
save this file as Simple.java
To compile: javac Simple.java
To execute: java Simple

Understanding first java
program
 Let's see what is the meaning of class, public,
static, void, main, String[], System.out.println().
 class keyword is used to declare a class in java.
 public keyword 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.

Understanding first java
program
 void is the return type of the method, it
means it doesn't return any value.
 main represents startup of the program.
 String[] args is used for command line
argument. We will learn it later.
 System.out.println() is used print statement.
We will learn about the internal working of
System.out.println statement later.

To write the simple program, open notepad by start menu -> All Programs
-> Accessories -> notepad and write simple program as displayed below:

As displayed in the above diagram, write the simple program
of java in notepad and saved it as Simple.java. To compile
and run this program, you need to open command prompt
by start menu -> All Programs -> Accessories -> command
prompt.

To compile and run the above program, go to your current directory
first; my current directory is c:new . Write here:
To compile: javac Simple.java
To execute: java Simple
To compile and run the above program, go to your current
directory first; my current directory is c:new . Write here:

How many ways can we write a
java program
 There are many ways to write a java
program. The modifications that can be
done in a java program are given below:
1) By changing sequence of the
modifiers, method prototype is not changed.
Let's see the simple code of main
method.
static public void main(String args[])

 2) subscript notation in java array can be
used after type, before variable or after
variable.
 Let's see the different codes to write the
main method.
public static void main(String[] args)
public static void main(String []args)
public static void main(String args[])

 3) You can provide var-args support to
main method by passing 3 ellipses (dots)
 Let's see the simple code of using var-args
in main method. We will learn about var-
args later in Java New Features chapter.
public static void main(String... args)

 4) Having semicolon at the end of class in
java is optional.
 Let's see the simple code.
class A
{
Static public void main(String... args)
{
System.out.println("hello java4");
}
};

Valid java main method
signature
 public static void main(String[] args)
 public static void main(String []args)
 public static void main(String args[])
 public static void main(String... args)
 static public void main(String[] args)
 public static final void main(String[] args)
 final public static void main(String[] args)
 final strictfp public static void main(String[] arg
s)

Invalid java main method
signature
 public void main(String[] args)
 static void main(String[] args)
 public void static main(String[] args)
 abstract public static void main(String[] ar
gs)

Resolving an error "javac is not
recognized as an internal or
external command" ?
 If there occurs a problem like displayed in
the below figure, you need to set path.
Since DOS doesn't know javac or java, we
need to set path. Path is not required in
such a case if you save your program
inside the jdk/bin folder. But its good
approach to set path. Click here for How
to set path in java.

How to set path of JDK in
Windows OS
 Setting Temporary Path of JDK
 Setting Permanent Path of JDK

 The path is required to be set for using tools such
as javac, java etc.
 If you are saving the java source file inside the
jdk/bin directory, path is not required to be set
because all the tools will be available in the
current directory.
 But If you are having your java file outside the
jdk/bin folder, it is necessary to set path of JDK.
 There are 2 ways to set java path:
 temporary
 permanent

1) How to set Temporary Path
of JDK in Windows
 To set the temporary path of JDK, you
need to follow following steps:
 Open command prompt
 copy the path of jdk/bin directory
 write in command prompt: set
path=copied_path
 For Example:
set path=C:Program
FilesJavajdk1.6.0_23bin

2) How to set 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

3)click on environment
variables

4)click on new tab of user
variables

7)paste path of bin folder in
variable value

Setting Java Path in Linux OS
 Setting the path in Linux OS is same as
setting the path in the Windows OS. But
here we use export tool rather than set.
Let's see how to set path in Linux OS:
export
PATH=$PATH:/home/jdk1.6.01/bin/
Here, we have installed the JDK in the home
directory under Root (/home).

1 .java basic

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1 .java basic