Java Fundamentals · Getting Started · Lesson 2 of 22

Compiling and Running Java

Concept

Compiling and Running Java

Java source files compile to bytecode with javac, then run on the Java Virtual Machine (JVM) with the java command — which is how the same compiled program can run on any device with a JVM installed.

By the end of this lesson

Explain the core idea behind Compiling and Running Java.
Predict output before running a change.
Test one realistic and one unusual input.
Use the result to make the next decision.

How to study this page

1. Read one concept.
2. Change the example.
3. Run, compare, and explain.
4. Complete the challenge below.

ExampleRunnable

// Compile: javac Main.java
// Run:     java Main
public class Main {
    public static void main(String[] args) {
        System.out.println("Compiled and running!");
    }
}

Try it Yourself »

Self-check before continuing

Without looking at the example, describe what changes when you modify one input in Compiling and Running Java. Then reopen the editor and prove your explanation with a small test.

You are ready to continue when you can predict, test, and explain the result.

Your turn

Explain, in a comment, the difference between compiling and running a Java program.

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Console

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