What Is Java? A Beginner's Guide to the Java Programming Language

Java is a general-purpose programming language used to build everything from bank systems and online stores to Android apps. You write your code once, and it runs on Windows, macOS, or Linux without changes. This guide explains what Java is, how it works behind the scenes, and how to write your very first program.

What is the Java programming language?

Java is a language for giving instructions to a computer. It was created by James Gosling and his team at Sun Microsystems and released in 1995. Today Oracle maintains it, together with a large open-source community through the OpenJDK project.

You'll often hear Java described with three words. Here's what each one means in plain English:

• Object-oriented — you organise code around "things" (objects) that hold data and actions together, like a Customer with a name and a sendInvoice() action. We cover this in Java classes and objects.
• Statically typed — every variable has a fixed type (number, text, and so on) that Java checks before the program runs. Many mistakes get caught early.
• Platform independent — the same compiled program runs on any operating system that has Java installed.

Why does Java matter?

How does Java work? Write once, run anywhere

Most languages are either compiled straight to machine code (fast, but tied to one operating system) or interpreted line by line (portable, but slower). Java does a bit of both:

JDK vs JRE vs JVM: what's the difference?

These three acronyms confuse almost every beginner. Think of them as boxes inside boxes:

Let's see it in action: your first Java program

Create a file named Hello.java and type this in:

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

Here's what each line does:

• public class Hello — declares a class called Hello. In Java, all code lives inside a class, and a public class must have the same name as its file.
• public static void main(String[] args) — the entry point. When you run the program, Java starts here. static means Java can call it without creating an object first (see the static keyword).
• System.out.println(...) — prints a line of text to the console.

Now compile and run it from a terminal:

javac Hello.java   # creates Hello.class (bytecode)
java Hello         # the JVM runs it

Hello, Java!

What should you learn first in Java?

Java is easiest to learn in layers. This series follows the order below. Each step builds on the one before:

1. Classes and objects — the building blocks of every Java program.
2. Access modifiers — controlling who can see and change your data.
3. Inheritance, abstract classes, and interfaces — reusing and organising code.
4. Java keywords — this, super, static, final, new, and more.
5. The Collections Framework — lists, sets, and maps for storing groups of data.

Quick recap

What's next?

Start with Java classes and objects. Once you're comfortable with the basics, see which Java web frameworks professionals use to build real applications.