To be honest, I’m not even sure if Julia is currently used as a backend within Java applications. This was something I explored a while ago, inspired by how R was integrated into Java using RCaller. JuliaCaller was an attempt to replicate that approach. While you can certainly invoke a Julia instance as a separate process, making sequential calls is inefficient due to Julia’s well-documented startup latency.
While JuliaCaller aimed to facilitate sequential calls using sockets, I’m frankly not confident about its current applicability. Industry changes by time.