Java Introduction

What is Java?

Java is a high-level, object-oriented programming language used to build everything from desktop applications to mobile apps, enterprise systems, and cloud-based services.

Originally developed by James Gosling in 1995 at Sun Microsystems (now owned by Oracle), Java is known for its philosophy:

Write Once, Run Anywhere

This means code written in Java can run on any system that has a Java Virtual Machine (JVM), without modification.

Key Features of Java

Platform Independent – Runs on Windows, Mac, Linux, etc. No need to change code for different systems.

Object-Oriented – Everything is based on classes and objects, making code reusable and easy to manage.

Secure & Robust – Offers strong memory management, built-in security, and exception handling.

Multithreaded – Supports running multiple tasks simultaneously for better performance.

Massive Community Support – Backed by millions of developers, a rich ecosystem of tools, and countless libraries/frameworks.

How Java Works

Write Code – You write your code in a .java file.

Compile – The javac compiler converts your code into bytecode (.class file).

Execute – The JVM (Java Virtual Machine) runs the bytecode on any platform.

Tip: You do not need to memorize the code execution process. The Java compiler and JVM handle it for you!

Your First Java Program

Here is a simple Java program that prints "Hello, Java!" to the screen:


// First Java Program
public class HelloJava {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

Output:

Hello, Java!

Where is Java Used?

Java powers many real world applications, including:

Web Development: Frameworks like Spring Boot and Hibernate

Android Development: Apps built with Java and Kotlin

Enterprise Software: Banking systems, CRM, ERP solutions

Game Development: Popular games like Minecraft and Runescape

Cloud & Big Data: Technologies like Hadoop and Apache Spark

Two Minute Drill

Java is powerful and object oriented.

Write once, run anywhere with the help of JVM.

Secure and reliable with automatic memory management.