As an HFT developer myself I have to disagree. I worked for tier 1 banks that used both:java and cpp.
The trend is moving towards quicker time to market and simpler implementations and replacing cpp with java.
The cpp code bases I had to deal with were old, hard to maintain and easy to break.
More often than not cpp was a pretty bad lock in as well. For example a big evil bank very well known here struggled for 3 years to upgrade the compiler on one of those projects.
Did not happen to this day, I'm told. Few years later they are still on RHEL6 and gcc 4.
Speed is an important factor in this business, but so is time-to-market.
I am afraid tier 1 banks aren't tier 1 in HFT though. Best HFTs are at "small" houses and your tier 1 bank experience isn't reflective of what they do.
How is replacing with Java better than replacing with C++? Legacy code is a problem, and bad programmers will write bad code in any language. If you need to start over does Java give you anything you can't get with modern C++?
From my personal experience I'd say java is much more forgiving than c/cpp and things like debugging or dependency management make it a tempting option in a time-constrained environment.
The trend is moving towards quicker time to market and simpler implementations and replacing cpp with java. The cpp code bases I had to deal with were old, hard to maintain and easy to break. More often than not cpp was a pretty bad lock in as well. For example a big evil bank very well known here struggled for 3 years to upgrade the compiler on one of those projects. Did not happen to this day, I'm told. Few years later they are still on RHEL6 and gcc 4.
Speed is an important factor in this business, but so is time-to-market.