What is Java ?

What is Java?, Where we can use?, Why Java?, How Java?
[ANS]  A high-level programming language developed by Sun Microsystems. Java was originally called OAK, and was designed for handheld devices and set-top boxes. Oak was unsuccessful so in 1995 Sun changed the name to Java and modified the language to take advantage of the burgeoning World Wide Web.
Java is an object-oriented language similar to C++, but simplified to eliminate language features that cause common programming errors.
Java source code files (files with a .java extension) are compiled into a format called bytecode (files with a .class extension), which can then be executed by a Java interpreter. Compiled Java code can run on most computers because Java interpreters and runtime environments, known as Java Virtual Machines (JVMs), exist for most operating systems, including UNIX, the Macintosh OS, and Windows. Bytecode can also be converted directly into machine language instructions by a just-in-time compiler (JIT).

Popularity of java:

1. Rich library: Java provides so many build-in APIs (Classes and Methods).
In C/C++ first we need to write concepts then we can make a application but Java provide so many build-in APIs, with the help of these APIs we can easily make a application.

Example: sorting of arrays. in c/c++ we need to write concept of sorting but java provides build-in APIs for sorting. no need to write manual concept just call that APIs and execute your code.
2. Rich constructs. Java made by a team not by a single person and it is the result of many years of consistent hard work.
3. Applets: Small programs written in Java executed within Browser.
4. Servlets: Small programs written in Java executed on Server.
5. Midlets: Small programs written in Java executed on Micro Devices.
6. Xlets: Small programs written in Java executed in Desktop Box.
7. Application: Programs written in Java executed in Desktop.

Features of java:
1. Simple: Resembled With C/C++.
2. Portable: Small Programs.
3. Powerful: Because of Rich Library.
4. Secure and Robust: No pointers And Does NOT interact with Hardware Directly.
5. Dynamic in nature.
6. Distributed: Distributed Storage and Distributed Processing.
7. Multi-Threading: [Multitasking +Sharing of Data+ Interthread Communication].
8. True OOPs: support Encapsulation, Inheritance, Abstraction and Polymorphism.
9. Compiled and Interpreted, yet High Performance:
[Source Code]——————[Byte Code]

10. Platform Independent:
C/C++: Program Compiled in Window XP can only execute in Window XP.
It’s Called Platform Dependent.
JAVA : Program Compiled in Window XP can execute in Window XP, Linux and Solaris. But it requires JRE dependency. It’s Called Platform Independent.
The Technologies that comes within Java can be classified in 5 Categories:
1. Desktop Technologies:
Core Java
Java2 (Second Generation)
Scope: Desktop / LAN
2. Distributed Technologies:
Remote Method Invocation (RMI)
Scope: Distributed Storage and Distributed Processing
3. Web Technologies:
Java Server Pages (JSP)
Java Server Faces (JSF)
Scope: Intranet / Extranet / Internet
4. Enterprise Technologies:
Java 2 Enterprise Edition (J2EE)
Enterprise Java Beans (EJB)
Scope: Enterprise
5. Micro Technologies:
Java 2 Micro Edition (J2ME)
Scope: Mobiles / PDAS / Set Top Boxes

Requirements for Interpretation:
JVM: Java Virtual Machine,
JRE: Java Runtime Environment.
Software Requirements:
1. JDK: Java Development Kit
Compiler: javac
Interpreter: java
Debugger: jdb
Documentation: javadoc
To View Applets: appletviewer
Java APIs
2. Editor:
Notepad, VI, Edit
OR IDE [Integrated Development Environment]
Example: NetBeans, Eclips, JCreator.

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