Java First Program
Understanding the Basics
Starting your journey with Java begins with writing your first program. This isn’t just tradition — it’s a practical way to understand how Java works under the hood. The classic "Hello, World!" program is simple, but it introduces key concepts that every Java developer must know.
What You’ll Learn
How to write and structure a basic Java program
The role of the main() method
How to display output using System.out.println()
How to compile and run Java code using the command line
The Code
HelloWorld.java
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}This code might look small, but it packs a punch. Let’s break it down:
public class HelloWorld — defines a class named HelloWorld. In Java, every program starts with a class.
public static void main(String[] args) — the entry point. Java looks for this method to begin execution.
System.out.println("Hello, World!") — prints the message to your screen.
Running the Program
Install Java — download and install the Java Development Kit (JDK) from Oracle’s official site.
Write the code — use any text editor (Notepad, VS Code, etc.) and save the file as HelloWorld.java.
Compile the code — open a terminal in the file’s folder and run javac.
Run the program — once compiled, run java HelloWorld.
Compile
javac HelloWorld.java
Run
java HelloWorld
Output
Hello, World!
Why This Matters
This first program teaches you:
How Java syntax is structured
How to use the command line for compiling and running code
How output is displayed in Java
It’s your first step toward building real-world applications — from simple calculators to full-stack systems.
What’s Next?
Now that you’ve written and executed your first Java program, you’re ready to explore:
Variables and data types
Conditional logic
Loops and functions
Object-oriented programming