Java-OS4

A Java 8 runtime for AmigaOS 4 (PowerPC) — JamVM 2.0 + the OpenJDK 8 class library, with a native AWT/Swing toolkit so Java GUIs run in Workbench windows.

Beta. Java-OS4 runs real headless and Swing applications, but it is still under active development — expect rough edges, gaps, and changes between releases. Bug reports and feedback are welcome.

Java-OS4 brings a real, modern-enough Java to 32-bit big-endian PowerPC AmigaOS 4: it runs ordinary Java 8 .jar files — collections, streams and lambdas, NIO, reflection, serialization — and renders Swing user interfaces through Intuition and graphics.library. It is built by reviving and extending the JAmiga prior art rather than starting from scratch.

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Status

Phase	Scope	State
0	Vendor sources + cross-build environment	✅ Done
1	JamVM engine bring-up (Hello World)	✅ Done
2	OpenJDK 8 class library integration (java -version, headless)	✅ Done
3	Headless conformance — io/nio/util/text/zip/reflection, threads + GC	✅ Done (48/48 tests)
4	AWT/Swing GUI — Intuition windows, Java2D, real input, dialogs	✅ Done
5	Packaging, polish, performance	🚧 In progress (first release: 0.5.0)

The current release runs headless Java 8 programs and Swing applications (windows, widgets, mouse, keyboard, resize, modal dialogs) in Workbench windows. See docs/ for screenshots of each milestone.

Features

• Engine: JamVM 2.0 — an inline-threaded / stack-caching interpreter, retargeted to AmigaOS 4 PowerPC.
• Class library: the full OpenJDK 8 runtime (rt.jar and friends), so real Java 8 application compatibility — not a subset.
• C runtime: clib4 (pthreads, mmap, dlopen).
• GUI: a Caciocavallo-style AWT toolkit (sun.awt.amiga) — only top-level windows get native peers (Intuition windows backed by an ARGB framebuffer blitted with graphics.library); every widget inside is a Swing lightweight painted by Java2D. Fonts via FreeType.
• Zero-flag GUI launch: java -cp app.jar Main starts a Swing app with no special options — the Amiga toolkit is the platform default.

Quick start

A packaged release is an .lha containing a Java-OS4 installer drawer. Download the latest from the Releases page, or build it from source (see Building from source below). Per-release changes are listed in CHANGELOG.md.

0.5.4 fixes the sun.boot.class.path separator on AmigaOS: Swing apps and the test suite no longer pop a "Please insert volume niopatch.zip" requester or crash with "Trampoline must not be defined by the bootstrap class loader" (amigans.net report). Upgrading is recommended for anyone on 0.5.1–0.5.3.

Requirements:

• AmigaOS 4 (PowerPC). Swing/AWT GUIs additionally need graphics.library V52+ and intuition.library (standard on current AmigaOS 4); headless programs do not.
• clib4.library 2.1 or newer in LIBS: — the C runtime the VM depends on. The installer copies the bundled copy there if it is missing (get the latest from clib4 to update it).
• The installer runs under Sys:Utilities/Installation Utility (AmigaOS 4.1).

1. Unpack it anywhere on your AmigaOS 4 machine.

2. Double-click the Java-OS4 drawer icon to launch the installer (it runs under Sys:Utilities/Installation Utility). The wizard asks where to install the runtime, copies it there, adds a permanent JAVA: assign to S:User-Startup (live immediately, no reboot needed), and copies the java launcher to C: so it runs from any Shell.

3. Run programs from a Shell — the release bundles runnable examples:

   java -version
   java -cp examples/HelloJava.jar HelloJava   ; headless demo
   java -cp examples/SwingDemo.jar  SwingDemo   ; Swing demo
   java -cp examples/testsuite.zip  VmSuite     ; self-test
   

   Swing/AWT applications need no extra flags. Application classpath entries are resolved from the JAVA: drawer; reference jars elsewhere by absolute path.

javac is not included — compile on a host JDK 8 (use javac --release 8) and copy the .jar over. Bytecode newer than Java 8 is rejected up front with UnsupportedClassVersionError rather than failing mysteriously at run time.

Building from source

The toolchain runs in a Docker image — the AmigaOS 4 PowerPC cross compiler plus a host JDK 8 — driven by the Makefile:

git submodule update --init     # check out the clib4/ submodule (or clone --recursive)
make vendor                     # fetch the JamVM + IcedTea 8 upstream sources, once
make image                      # build the cross-build image (pulls the public
                                #   walkero/amigagccondocker base), once
make build                      # clib4 + VM + native libraries + AWT toolkit
make dist                       # assemble the install tree + the .lha release
                                #   -> build/JavaOS4-<ver>.lha

make release does build then dist in one step; make help lists every target. The clib4 C runtime is the in-repo clib4/ git submodule (AmigaLabs/clib4, development), built by make clib4 automatically. The larger JamVM + OpenJDK 8 (IcedTea) upstream trees are public but not committed here — make vendor fetches them (see docs/BUILDING.md for the full source-acquisition flow). No external paths are needed.

Full instructions, the build-script order, and how to run on QEMU or hardware are in docs/BUILDING.md.

How it works

        Java apps (.class/.jar)  +  Swing
                          |
        OpenJDK 8 class library (rt.jar) + native libs
                          |
   AWT toolkit: sun.awt.amiga peers -> Intuition + graphics.library V52+
                          |
        JamVM 2.0  (libjvm.so: interpreter + GC + JNI)
                          |
   os/amiga glue: pthreads, dll loading, exception proxy, callNative
                          |
        clib4  on  AmigaOS 4 exec/dos/intuition/graphics  (PPC32 BE)

The key engineering work (cooperative GC safepoints, the Amiga path model, native symbol resolution via clib4's shared-library model, the AWT peer design) lives in the src/ tree; build and run instructions are in docs/BUILDING.md.

Repository layout

src/amigaawt/     the sun.awt.amiga AWT toolkit (Java peers + JNI)
src/niopatch/     NIO.2 provider patch for the Amiga path model
src/fontconfig/   minimal fontconfig.properties for the font pipeline
src/tools/        small native helpers (e.g. an input injector for GUI tests)
tests/            self-verifying conformance + GUI test programs
tools/            Docker image + build/package scripts
docs/             notes, screenshots, and the JamVM vendor patch

The upstream JamVM / OpenJDK trees are not committed here; the AmigaOS 4 changes to JamVM are carried as a patch at docs/jamvm-amiga-openjdk.patch.

Acknowledgements

Java-OS4 stands on a great deal of prior work, with gratitude:

• JAmiga by jaokim — the Java-on-Amiga effort this project revives and extends. The AmigaOS 4 JamVM port and the IcedTea 8 build harness are the foundation we built on.
• JamVM by Robert Lougher — the compact, fast Java virtual machine at the core. (GPLv2)
• OpenJDK and IcedTea — the Java 8 class library and build tooling. (GPLv2 with Classpath Exception) The class-library bytecode used at runtime comes from Eclipse Temurin 8.
• clib4 — the modern AmigaOS 4 C runtime (pthreads, mmap, dlopen) this build targets.
• GNU Classpath — used as the engine bring-up stepping stone in Phase 1. (GPLv2 with Classpath Exception)
• AmigaOS 4 and its SDK — intuition.library, graphics.library V52+, keymap.library, and the PowerPC toolchain.
• The OpenJDK Caciocavallo project, whose peer-toolkit design informs the sun.awt.amiga approach.

License

Java-OS4 is distributed under the GNU General Public License, version 2 — see LICENSE. This matches JamVM (GPLv2); the OpenJDK-derived parts carry the GPLv2 Classpath Exception. Original source in this repository (src/, tools/, tests/) is GPLv2-compatible; the AWT toolkit and other class-library-adjacent code additionally grant the Classpath Exception, as noted in their file headers.

When redistributing a built release you are combining GPLv2 (JamVM) and GPLv2-with-Classpath-Exception (OpenJDK) components; the result is governed by the GPLv2.