I am planning to integrate Lua into my java application. Could you please tell about performance comparison between implementing a script in LuaJ vs pure java. Are there other alternatives which have better performance ?
Lua is just insane fast with JIT compiling by LuaJIT, the reference implementation (also known as CLua) is fast too but no match for JIT compiled Java.
LuaJ can compile Lua to Java bytecode but not as effective as Java to bytecode because the Java language is nearer to hardware architecture and thus results in faster machine code.
Using LuaJ makes sense to add a scripting language to your project but for performance go with Java.