Java Introduction

What is Java ?

Java is a General-Purpose Programming Language that is Object-Oriented Based.

Java is a High Level Programming Language that is used to developed Applications.

Java is a Third Generation Language which is based on compiler and interpreter.

What is the Area of Java ?

Java is used in different areas but basically used in following three areas:

1. It is used in Desktop Based Applications.

2. It is used in Web Based Applications.

3. It is used in Mobile Based Applications.

History of Java ?

Initially in 1991 Java is called OAK that was a Green Project and its extension was .gt that was Green Talk but due to some copy right issue in 1995 its rename and name is Java. James Gosling is founder of Java at Sun Micro System but in 2010 Oracle purchase Java so now Java is product of Oracle Company.

Why Java is Invented or Developed ?

Java is invented or developed just because of WORA concept where WORA stand for "Write Once Run Anywhere". It means developer can compile a Java code single time and execute that code in different Platform or Operating System. Simply you can say using WORA concept you can acheive Platform Independent.

What are the Java or JDK Versions

1. JDK 1.0 (January 23, 1996)
2. JDK 1.1 (February 19, 1996)
3. J2SE 1.2 (December 8, 1998)
4. J2SE 1.3 (May 8, 2000)
5. J2SE 1.4 (February 6, 2002)
6. J2SE 5.0 (September 30, 2004)
7. Java SE 6 (December 11, 2006)
8. Java SE 7 (July 28, 2011)
9. Java SE 8 (March 18, 2014)
10. Java SE 9 (September 21, 2017)
11. Java SE 10 (March 20, 2018)
12. Java SE 11 (September 25, 2018)
13. Java SE 12 (March 19, 2019)
14. Java SE 13 (September 17, 2019)

What is the Features of Java ?

Java has following features :

1. Simple
2. Robust
3. Platform Independent
4. Dynamic
5. Interpreter
6. Secure
7. Architecture Neutral
8. Distributed
9. Multithreaded
10. Open Source
11. API Based
12. Portable
13. High Performance
14. Object Oriented Programming

Simple

1. Java is simple because its sytax is borrow from C and C++.

2. Java is simple because it does not have Destructor.

3. Java is simple because it does not have explicit pointer.

4. Java is simple because it support call by value only.

5. Java is simple because it provide built API(Application Programming Language).

6. Java is simple because it does not support Operator Overloading.

7. Java is simple because it does not support Multiple Inheritence.

Robust

1. Java supported Automatic Garbage Collection that means you dont need to remove object which is not used by applications any more. It take care by Automatic Garbage Collection.

2. It means you dont need to worried about Memory Management.

3. Java supported better Exception Handling and Type checking.

Platform Independent

1. Java source code compile with javac tool and it create a .class that contain bytecode which is an intermediate code which can be executed on any Platform or Operating System.

2. It means you can write a java program once and run it on any Platform without recompiling the code.

3. Thus the slogan is "Write Once Run Anywhere".

Dynamic

1. In java the class is loaded at runtime in to the JVM(Java Virtual Machine) thats why everything is happens at runtime.

2. In java memory is allocated at runtime when class is loaded.

Interpreter

1. Java is compiler and interpreter based where compiler compile source code to bytecode and when class (bytecode) loaded in JVM then interpreter convert to byte code in native code.

2. This Interepreter is kind of platform dependent because it can convert byte code in to the particular platform or machine.

3. This Interpreter is design for every platform seperated thats why it can covert bytecode into a single machine only.

Secure

1. Java is secure because of no explict pointer that means no one can access address explicit without Authentication.

2. Java is secure because of Byte Code Verifier. Using Byte Code Verifier it checks class code at Runtime when class is loaded on JVM.

3. Java is secure because of SandBox that means no one can access other resources without Authentication.

Architecture Neutral

1. In Java primitive data type size is fixed for all type of architecture (32 bit or 64 bit).

2. Architecture neutral means you dont need to change Hardware or software for executing code in different platform architecture.

Distributed

1. Java is also Distributed Language that means a program can be run on computer networks.

2. Using RMI (Remote Method Invocation) you can create Distributed Application.

3. Using Webservices also can create Distributed Application for different Language.

4. Webservices can be acheive using SOAP(Simple Object Access Protocol) and RESTful.

Multithreaded

1. Java supports multithreading to acheive multitasking.

2. Multitasking means you can perform multiple task simultaneously.

3. You can use multithreading when you have limited resources.

4. Example like you want to create a game or share resources at same time from different machine.

Open Source

1. Open source means you can use java tools free for compiling and running.

2. You can also use Java Frameworks Open Source like Spring Framework and Hibernate Framework for RAD (Rapid Application Development).

3. There are lot of Editors for java Programming like Netbeans, Eclipse, Spring Tool Suite and IntelliJ Idea etc.

API Based

1. Java provide some predefine API or library that contains classes and methods to perform a task without writing own logic.

2. Java also supports third party API to use other developers classess like GSON, ITEXT, PAYMENT GATEWAY, GOOGLE MAP etc.

Portable

1. Java is portable just because of WORA concept (Write Once Run Anywhere).

2. Java code is easy to carry from one platform to another platform.

High Performance

1. Java is High Performance just because of Byte code converted to native or machine code once.

2. Using JIT (Just In Time) you can acheive this tracking because JIT has Profiler Tool.

Object Oriented Programming Language

1. Java supports OOPS to acheive code reuseability.

2. There are following OOPS Components:

i. Class

ii. Object

iii. Polymorphism

iv. Inheritence

v. Interface and Abstraction

vi. Encapsulation