Project Panama

Project Panama is the OpenJDK project concerned with the boundary between the JVM and everything outside it: native libraries, off-heap memory, and hardware the JVM does not expose directly. Its goal is to make that boundary crossable from plain Java, without writing C.

Its deliverables:

• Foreign Function & Memory API — call native functions and safely access off-heap memory from Java. Finalised in Java 22 (JEP 454), and the replacement for JNI in new code.
• jextract — a tool that reads a C header file and generates the Java bindings for it, so wrapping a native library is a build step rather than a hand-written project.
• Vector API — expresses computations that reliably compile to SIMD instructions on the CPU. It has been incubating for many releases, deliberately: the API is held back until the underlying compiler support is ready, and it depends on work in Project Valhalla.

Why this replaced JNI rather than improving it. JNI required a C shim compiled for every platform you shipped to, and a mistake in it crashed the JVM rather than throwing. The Foreign Function & Memory API keeps the checks in Java: memory is accessed through a MemorySegment with known bounds and a known lifetime, so a use-after-free becomes an exception instead of a segfault. The cost is that unsafe operations are explicit and must be enabled — which is the point.

More reading on Foojay:

• Building Project Panama’s jextract tool by yourself
• Java Panama Polyglot (C++) Part 1
• Foojay Podcast #82: OpenJDK Projects (Leyden, Babylon, Panama) and TornadoVM

See Also

• Foreign Function & Memory API
• Java Native Interface (JNI)
• Value Objects (Project Valhalla)
• OpenJDK Projects