What Is Java?

Welcome! If you have never written a single line of code, you are in exactly the right place. By the end of this lesson you'll know what programming is, what Java is, and why it quietly runs a huge part of the modern world.

What is programming, really?

A computer is astonishingly fast but completely literal. It does exactly what it is told - nothing more, nothing less. Programming is the act of writing those instructions in a language the computer can eventually understand.

The catch is that computers don't understand English (or German). They ultimately only understand machine code - long strings of 1s and 0s. Writing that by hand would be miserable, so we use friendly programming languages instead, and a translator turns our code into something the machine can run.

Java is one of those friendly languages - and one of the most important ever created.

So what is Java?

Java is a high-level, object-oriented programming language. Let's unpack that phrase without any jargon:

• High-level - it reads much more like English than like 1s and 0s, so humans can actually work with it.
• Object-oriented - you model your program as a collection of "objects" (like a Car, a BankAccount, or a Player) that hold data and can do things. You'll learn all about this in Stage 2.

Here is a complete, real Java program. Don't worry about understanding every symbol yet - just notice that you can almost read it:

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

When you run it, the computer prints:

Hello, Java!

That one line - System.out.println(...) - literally means "print this line of text to the screen." You just read your first Java program. 🎉

Where does Java actually run?

This is where Java's magic lives. Most of your code runs on top of something called the Java Virtual Machine (JVM) - a program that runs your program.

We'll explore the JVM in detail in The Java Ecosystem, but keep this mental picture: your code → the JVM → any machine.

Why should you learn Java?

Java has been around since 1995, and far from fading away, it powers an enormous amount of the software you use every day:

Because so much critical software is written in Java, skilled Java developers are consistently among the most in-demand and well-paid engineers in the industry. Learning it is a genuinely valuable investment.

Quick check

Next up, we'll travel back to 1991 and meet the small team that created Java - and discover why it was almost called Oak.