Create your first Codename One project and get a green build

1. Use any modern JDK (17–25). You do not need to downgrade to JDK 17 to build. (Codename One supports a large subset of the Java API, not the full Java 25 library — so a few newer APIs aren't available at runtime, but that never blocks a build.) Make sure JAVA_HOME points to a JDK, not a JRE.
2. Create the project from the Codename One initializr / Maven archetype and open it in your IDE. The tool defaults to IntelliJ/Idea if you use a different IDE make sure to select it in initializr.
3. Build for desktop or Android first. Pick Windows/Linux desktop or Android — no certificate required, and you'll have a running app in minutes. (iOS next — see the iOS signing article.)

Common setup errors

• "Problem downloading the Maven project" / archetype fails → almost always a corporate proxy/mirror or JAVA_HOME pointing at a JRE. Check both; retry.
• "Why is it Java 17 and not 25?" → it isn't a JDK limit — build with any JDK. It's about which Java APIs we implement. Full list: {link to API docs}.

Updated on: 07/14/2026