Hi-speed trading is a zero-sum game, like poker. Every single gain is somebody's loss. Either you rip the other guy's heart out and eat it, or he rips your heart out and eats yours. There is no other choice.

Choosing Java over C++ is choosing to be that second guy.

Sure, Java coders are cheaper and easier to hire, and they produce lots more code. But if lots of code is a liability, lots of Java code is a bigger liability.

A trading house with a lot of Java code is a red warning.