LuaJ

LuaJ, sometimes written Luaj, is a lightweight, embeddable Lua interpreter implemented in Java. It enables Lua scripting within Java applications by running Lua code on the Java Virtual Machine and by providing a bridge between Lua and Java for interoperation. It is designed to be easily integrated into Java programs and to run on standard Java environments.

LuaJ provides both a pure Java implementation of a Lua interpreter and a compiler that translates Lua code into Java bytecode for improved performance. It can operate in an interpreted mode or use its bytecode compiler to speed up execution. The runtime includes a Lua standard library subset and supports core Lua features such as tables, first-class functions, coroutines, and metatables, with some deviations from the reference Lua versions.

The framework exposes a Java-friendly API that allows Lua scripts to create and manipulate Java objects, invoke Java methods, and pass values between Lua and Java. Conversely, Java applications can call Lua functions, register Java classes for use in Lua, and load Lua modules. This bidirectional interoperability makes LuaJ suitable for embedding scripting capabilities in Java programs.

LuaJ is commonly used to embed scripting in desktop and server applications, games, data processing pipelines, and automation tasks where Lua scripts can customize behavior without recompiling Java code. It is available as an open-source library and can be integrated via build tools such as Maven or Gradle. LuaJ runs on the Java Virtual Machine and supports multiple platforms that implement Java.