The era that that particular one was written in, java was still accepted in RT systems. These days, that is not the case (I've worked on them myself). They are

The era that that particular one was written in, java was still accepted in RT systems. These days, that is not the case (I've worked on them myself). They are typically written in C/C++/ADA. Bear in mind that there are typically many levels to something like an ESM system, the lower levels would always be in something like C/C++/ADA (or possibly FPGA) but if Java does come into it, it would be for the UI but even that is more likely C# these days. This is not the RT level code.