Codename One is a development framework created by SUN that allows developers to write native mobile apps in Java that can run on all major platforms. It provides an SDK and cloud build server so that developers can write their code once in Java and deploy created apps to iOS, Android, and other devices without having to use separate languages or write platform-specific code. Codename One handles the cross-platform deployment and provides features like GPS, maps, camera, contacts and more through its APIs and plugins.