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What is Java Programing?

☕ JAVA Programming Language

Beginner Friendly Complete Notes

Java is a powerful, object-oriented programming language developed by James Gosling, Mike Sheridan, and Patrick Naughton in June 1991 at Sun Microsystems (now a subsidiary of Oracle Corporation).

Initially, Java was called “GreenTalk” with the extension .gt. Later, it was renamed “Oak”, symbolizing strength and longevity. In 1995, it was finally renamed JAVA.

šŸ“¦ Parts of Java

  • JDK (Java Development Kit): Tools required to develop Java programs.
  • JRE (Java Runtime Environment): Environment required to run Java programs.
  • JVM (Java Virtual Machine): Executes Java bytecode.

✨ Features of Java

  • Simple
  • Object Oriented
  • Platform Independent
  • Secure
  • Robust
  • Architecture Neutral
  • Portable
  • Dynamic
  • Interpreted
  • High Performance
  • Multithreaded
  • Distributed

šŸ§  Object Oriented Programming (OOP)

Object Oriented Programming organizes software using objects that combine data and behavior. It simplifies development and maintenance by following structured rules.

šŸ”‘ Core Concepts of OOP

  • Object
  • Class
  • Inheritance: Parent to child relationship
  • Polymorphism: Same method, different behavior
  • Abstraction: Hiding internal details
  • Encapsulation: Protecting data using layers

šŸ’» Java Hello World Program

class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

šŸ”¤ Keywords & Identifiers

Keywords are reserved words in Java written in lowercase and cannot be used as variable names.

Identifiers are user-defined names for variables, classes, and methods.

šŸ“Œ Variables

Variables are named memory locations used to store data.

Rules for Naming Variables

  • Must begin with a letter
  • No spaces allowed
  • Keywords cannot be used
  • Only $ and _ allowed
  • Case-sensitive

šŸ“¦ Constants / Literals

  • Numeric Constants: Integers & decimals
  • Character Constants: Stored in single quotes
  • String Constants: Stored in double quotes

šŸ’¬ Comments in Java

Single Line Comment: // This is a comment

Multi Line Comment:

/* This is the first line
   This is the second line */

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