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Java was developed by James Ghosling and his team at Sun
Microsystems in California in 1991.
It took 18 months to develop the first working version.
The development of java solves the limitation of C and C++.
This language was first called as Oak named after the oak tree
that stood outside Ghosling’s office .
But the name was already taken, so the team renamed it Java in
1995
Java is the name of hot drinks which is very popular in USA.
All java team like this hot drink very much, so they decided to
give name of the language as a java.
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1) Simple
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Java is easy to learn and its syntax is quite simple, clean and
easy to understand.
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The confusing and ambiguous concepts of C++ are either left
out in Java or they have been re-implemented in a cleaner way.
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Pointers and Operator Overloading are not there in java but
were an important part of C++.
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2) Object Oriented
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Java is a true objected-oriented language.
Almost everything in Java is an object.
All program code and data resides within objects and classes.
3) Platform-independent
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Unlike other programming languages such as C, C++ etc. which
are compiled into platform specific machines.
Java is guaranteed to be write-once, run-anywhere language.
Java programs can be easily moved from anywhere at anytime.
Changes in OS and processors do not force any changes in Java
program.
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On compilation Java program is compiled into byte-code .
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This byte-code is platform independent and can be run on any
machine, plus this byte-code format also provides security.
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Any machine with Java Runtime Environment(JRE) can run Java
Programs.
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4) Secure
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When it comes to security, Java is always the first choice.
With java secure features it enables us to develop virus free system.
Java program always runs in Java runtime environment with
almost null interaction with system OS, hence it is more secure.
5) Multi Threading
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Java multithreading feature makes it possible to write program that
can do many tasks simultaneously.
Benefit of multithreading is that it utilizes same memory and other
resources to execute multiple threads at the same time, like While
typing, grammatical errors are checked along.
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6) Portable
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Java Byte code can be carried to any platform.
7) High performance
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Java performance is impressive due to the use of byte-code and
multithreading.
8) Distributed
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Java is designed as a distributed language for creating applications
on networks.
Java applications can access remote objects on Internet.
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How Java is different from C++?
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Java is a true object oriented language while C++ is basically C
with object-oriented extensions.
Java has replaced multiple inheritances of classes with a new
feature called interface.
Java doesn’t support pointers.
There are no header files in Java.
Java does not support global variables. Every variable and method
forms part of a class.
Java does not structures and unions.
Java supports automatic garbage collection and makes a lot of
programming problems vanish.
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Java Environment
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This includes a large number of development tools and hundreds
of classes and methods.
◦ The development tools are part of JDK(Java Development Kit).
◦ Classes and methods are part of JSL(Java Standard Library).
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1) Java Development Kit (JDK)
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Tools in JDK are used for developing and running Java programs:
Sr. no
Tool
Description
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appletviewer
Enables to view Java applets without actually using a Java-compatible
browser.
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Javac
Java compiler, which translates Java source code to byte-code files.
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Javap
Java disassembler, which converts byte-code files into a program description.
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Javah
Produces header files for use with native methods
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Java
It is the launcher for Java applications
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Javadoc
Creates HTML documents from Java source code files.
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Jar
Create and manage Java Archive (JAR) files.
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2) Application Programming Interface
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Java Standard Library or (API) includes hundreds of classes and
methods grouped into several packages such as:
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Package
Description
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Language Support
Package
Required for implementing basic features of Java.
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Utilities Package
Provides utility functions such as date and time functions.
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Input/Output
Package
Required for input/output manipulation.
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Networking Package
Enables to communicate with other computers via Internet
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AWT Package
The Abstract Window Tool Kit package contains classes that implement
platform-independent GUI.
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Applet Package
Includes a set of classes that allows to create Java applets.
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JVM
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Java virtual Machine(JVM) is a virtual Machine that provides
runtime environment to execute java byte-code.
JVM are most often implemented to run on existing operating
system.
JVM control execution of every Java program.
JVM is distributed with Java class library, a set of standard class library in
byte-code.
That implements the Java Application Programming Interface (API).
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Setting Java Environment
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Java is freely available on Oracle's Website.
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Download the latest version of JDK (Java Development Kit) on your operating
system.
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Install JDK on your machine.
Once you have installed Java on your machine you would need to set
environment variable to point to correct installation directory.
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Setting up path for windows OS
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1) Right click on my computer and select properties
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2) Go to the advanced system settings tab.
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3) Click on the Environment Variables button
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3) Enter the variable name and variable value as follows
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First Java Program
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class Hello
{
public static void main (String[] args)
{
System.out.println ("Hello World program");
}
}
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Step to compile and execute java program
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1) Open a text editor i.e. notepad++ and write the code as above.
2) Save the file as Hello.java.
3) Open the command prompt and go to the directory where you
saved your java program.
4) Type javac Hello.java and press enter to compile your code.
if there is no error then the command prompt will take you to the
next line.
5) Now type java Hello on command prompt to run your program.
6) You will be able to see Hello world program printed on the
command prompt.
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