Getting Started with Java

What is Java?

Java is a general-purpose, object-oriented programming language created by Sun Microsystems (now Oracle).
It is one of the most widely used languages for web, desktop, and mobile applications.

Java is known for its motto: “Write Once, Run Anywhere” — meaning code compiled on one system can run on any other system with the Java Virtual Machine (JVM).

Why Learn Java?

It powers millions of applications (banking systems, Android apps, enterprise software).
It’s platform independent (runs on Windows, macOS, Linux).
Huge ecosystem and community support.
In-demand skills for jobs in backend, mobile, and enterprise development.

Key Features of Java

Object-Oriented – everything is structured around classes & objects.
Platform Independent – JVM allows the same program to run on multiple systems.
Secure & Robust – strong memory management and error handling.
Multithreaded – supports running tasks in parallel.
Rich Libraries – built-in APIs for networking, data, GUIs, etc.

Getting Started with Java

Follow these steps to set up Java and run your first program.

Why Install Java?

Java programs require the Java Development Kit (JDK).
The JDK includes tools to compile and run Java code.

Installation Commands

# macOS (Homebrew)
brew install openjdk

# Ubuntu/Debian
sudo apt update
sudo apt install openjdk-17-jdk

# Windows (winget)
winget install Microsoft.OpenJDK.17

Verify Installation

Run this command to confirm:

java -version

You should see your installed version of Java.

Create the File

Open your editor and create a file named HelloWorld.java.

Add the Code

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

Notes

The filename must match the class name (HelloWorld).
System.out.println prints text to the screen.

What is Compilation?

Java code is not run directly — it is compiled into bytecode first.
This makes it platform-independent.

Compile Command

javac HelloWorld.java

This creates a file called HelloWorld.class.

Check for Errors

If nothing is printed, it means the compilation was successful.

Execute the Program

Run the compiled class with:

java HelloWorld

(don’t add .class — just the class name).

Expected Output

Hello, Java!

What’s Next?

You’ve written, compiled, and run your first Java program!

Next steps:

Try printing your name.
Add simple math (e.g., System.out.println(2 + 3)).
Explore variables, loops, and conditions.

Getting Started with Java

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