Java is a high-level language programming language Named developer friendly language which is developed by SUN microsystem in 1995. It use to make game applications and desktop applications also.
Java is open source technology, So it’s available free on Internet you can use without paying money.
You can see java anywhere anytime, In your daily life :-
When you go to railway station you can see the digital time clock, In that case java application has been used. When you play games in your mobile they made on java application. Your Desktop Calculator also made on java application. It also allows you to play online games, made on java. Chat with people all over the world.
So, Why I use Java ?? .. Maybe Beause it’s
Simple : Programs are easy to write and debug because java does not use the pointers explicitly, No Craches , Provide the automatic memory allocation and deallocation system.
Object Oriented : Provides characteristics of Object Oriented like :- Inheritance , Encapsulation , Polymorphism , Dynamic binding,
Distributed : Use protocols like HTTP and FTP, Sothat the Internet Programmers can get access the file from any remote machine on the internet instead od writing the same code again on the local machine system.
Multithreaded : One single program can have different threads executing independently at the same time.
Portable : The Main feature Write-once-run-anywhere .. JDO http://blog.catreloaded.org/2012/03/11/jdo/
High performance , Dynamic && Secure ! .
Some features of Java :
The Java Virtual Machine :- The hardware platform specifications to which you compile all Java code.
In Java , all source code :-
1.first written in text file ending with the extension .java Those source files are
2.Then compiled into .class files by the javac compiler.
The .class contains bytescodes.
* Note That the ByteCode is a special machine language that the Java Virtual Machine (JVM) can understand, ** will be defined later **
3.Then the Java Launcher runs runs the application with instance of the Language of the Java Virtual Machine “JVM”.
Garbage Collection : Simply it can free any space in the memory, and collect the unused spaces, this method of allocation and de-allocation happens automatically during the lifetime of the Java program and the execution.
What’s Java tools ?
– Compiler (javac)
– Interpreter (java)
– Documentation generator (javadoc)
– a Class file and so on ..
Now .. We have to define some concepts and defintions to get the whole view of java program execution.
First , What’s Java Byte Code ?
The low level source code that is executed by JVM when you run your Java program, when you compile your program, the Java compiler produces an output in Bytecode form.
Second , What’s Java Run Time ?
It’s the set of tools and software that runs and executes the Java program and it’s the environment required to execute Java programs, Java Virtual Machine (JVM) – JRE.
The JRE allows applets written in the Java programming language to run inside various browsers
Finally , What’s Java Compiler ?
A Java Compiler is a tool which compilers your source code and generates Bytecode output which can then be executed by the Java Runtime.
So, What’s the JAVA Decompiler ?
It’s the same, it’s the tool which can convert the Java Bytecode back to the original source code.
The whole process of compiling and executing a JAVA program.
In Fact .. “Java” refers to both a language and a platform, the runtime and libraries that comprise the platform are based on the Java language.
So what’s JAVA Platforms ?
There are four platforms of the Java programming language :-
1- JAVA SE (Standard Edition) platform :– for local and standard applications that don’t require enterprise servers behind them, multi-user accessing the single DataBase.
For example, if you want to access an Oracle database server from a remote client, you need to have the oracle client installed on the remote machine.
2- JAVA EE (Enterprise Edition) platform :- for enterprise applications, bussines and web based applications. Servlets, JSPs, Java Beans,..
The Java EE platform is built on top of the Java SE platform,it provides an API and runtime environment for developing and running reliable, and secure network applications.
The big thing associating with enterprise is Server.
3- JAVA ME (Micro Edition) platform :- It includes most of Java SE and some additional APIs for handheld small portable devices, provides an API and a small virtual machine for running Java programming language applications on small devices, specifically designed for mobile phone platforms.
API (Application Programming Interface) is a subset of the Java SE API,with special class libraries useful for small device application development.
4- JAVA FX platform:– for creating rich internet applications using a light user interface API, using hardware graphics and media engines to achieve higher performance, it extends the power of Java by allowing developers to use any Java library in JavaFX application
JavaScirpt is not part of the Java platform.
JavaScirpt code needed only to build websites.
Java is an OOP programming language, while Java Script is an OOP scripting language.
Finally .. WHY JAVA !
Write Once Run Everywhere .. Write your code on one platform and run it on virtually any other platform.
Create programs to run within a Web browser and Web services.
Write powerful and efficient applications for mobile phones , remote processors , low-cost products.