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Architecture

This project is organized around a modular architecture that separates the concerns of the Java runtime, the Java standard library, application code, and supporting tooling. The main components are:

1. VM

The Virtual Machine (VM) is built from OpenJDK/mobile. It provides the core runtime functionality of OpenJDK on mobile platforms and is implemented natively on each target OS.

  • Delivered as a shared or static library.
  • Contains the standard OpenJDK VM features adapted for mobile environments.
  • Ensures compatibility between server/cloud/desktop Java and mobile Java.

2. JDK Classes

The JDK classes component is also built from OpenJDK/mobile and contains the standard Java libraries for mobile:

  • Includes class files in bytecode form (jars, jmods, or optionally AOT-compiled classes).
  • Includes native code required by these class files.
  • Ensures that mobile developers can use standard Java APIs without writing platform-specific code.

3. Application Code and Dependencies

Application-specific code represents the project or app being developed:

  • Can contain Java and native code.
  • May depend on external libraries or frameworks.
  • Is project-specific and built separately from the VM and JDK classes.

4. Tooling

The tooling component ties everything together:

  • Bundles the VM, JDK classes, and application code efficiently.
  • Produces outputs ready for mobile deployment (e.g., Play Store, App Store) or development integration (e.g., Xcode, Android Studio).
  • Configurable to allow different use cases, from full apps to reusable Java libraries for mobile.

This architecture ensures a clear separation of concerns, maintains alignment with upstream OpenJDK, and enables developers to work with standard Java on mobile platforms without compromise.