Stage 1 · Lesson 1 of 9
The JDK, compiling and running
Java code is , turned into another form, before it runs. You write Hello.java and run javac Hello.java. That gives you Hello.class, which contains : instructions for a rather than a real chip.
Then java Hello starts the JVM (Java Virtual Machine), which runs that bytecode on any . For a single file you can also run java Hello.java directly. Every program starts at a main method, classically public static void main(String[] args), inside a class whose name matches the file.
Install a JDK (the full developer kit), not just a runtime. Do all this from the terminal before letting an IDE hide it. are a feature: the compiler catches type mistakes before the program ever runs. Read the first error, with its file and line number.
A question to check yourself, an AI practice session and 2 cheat sheet entries come when you add the roadmap to your account. Add it
Resources for this stage
Start with· follow one of these
- CourseFreeJava Programming MOOC
University of Helsinki · Beginner
Free Helsinki course with hundreds of auto-tested exercises; parts 1 to 8 cover this stage
- GuideFreeDev.java: Learn Java
Oracle · Beginner
Official tutorials from the Java team: read the language basics path next to the MOOC