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Introduction to Java

Introduction

Java is a high level, robust, secured and object-oriented programming language. It is both programming language and a software platform.

It is created by James Gosling from Sun Microsystems (Sun) in 1991.The target of Java is to write a program once and then run this program on multiple operating systems.

Software Platform

An environment in which a program runs, is known as a platform. In order to execute java program we need platform specific java runtime environment i.e. java platform.

Java Overview

An environment in which a program runs, is known as a platform. In order to execute java program we need platform specific java runtime environment i.e. java platform.

Platform Independent

We can run java program on any kind of operating system e.g. Windows, Linux, Mac/OS etc. Java code is compiled by the java compiler (javac) and generates the bytecode.

The bytecode is a platform independent code because it can be run on multiple platforms.

We write java program and saved it with .java extension. This .java file is known as source file or java file.

Java compiler compilesjava file and generates a class file. JVM reads the class file and converts it into native code (OS specific code).

Object-Oriented

Everything is an Object in java. We are writing java program based on object’s data and behavior.

Portable

We may run java bytecode to any platform.

Secured

  • Java does not support pointer arithmetic.
  • Java program runs in its own platform (jvm).
  • Byte code verifier.

No virus will infect the byte code. Even if the virus entered into byte code the jvm doesn't understand it, so jvm keeps these instructions as it is. No executable code will be generated to this virus.




Robust

Robust means powerful. Java is powerful because:

  • Strong memory management
  • No Pointers concept
  • Exception handling
  • Platform Independent
  • High-performance

Java enables high performance with the use of just-in-time compiler.

Distributed

We can access files by calling the methods from any machine on the internet.

Multi-threaded

The purpose of multithreading is to provide simultaneous execution of two or more parts of a program to maximum utilize the CPU time.

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