Introduction

Before learning Java,we must know What is Program and Programming language

Program: A program is a sequence of instructions,written to perform specific task with a Computer
Programming Language: A programming language is a formal language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine.

Ada Lovelace created the first algorithm designed for processing by a computer and is usually recognized as history's first computer programmer

What is Java?

        Java is a programming language and computing platform first released by Sun Micro systems in 1995 which was initiated by James Gosling.Java is guaranteed to be WRITE ONCE,RUN ANYWHERE

James Gosling, the creator of Java

                                                      

Java is an Object-Oriented Programming language with extensive class libraries.
You need a Java Run time Environment (JRE), consisting of a Java Virtual Machine (VM) and a copy of the Java API libraries, to run a Java program.
You need the Java Software Development Kit (JSDK), including a Java VM, a copy of the Java API  libraries, and a Java compiler, to create a Java program.
Code written on any platform, with any Java compiler, can be run on any platform with any Java Virtual Machine (interpreter).