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Java is Very Fast, If You Don’t Create Many Objects
(blog.vanillajava.blog)
For discussing Java, the JVM, languages that run on the JVM, and other related technologies.
So, Java is fast if you use it like C.
Its even better...
In C/C++ you have to create/destroy objects, deal with pointers (**& for the win!). As a result the average C/C++ developer has to think about alot more than the average Java developer.
In a previous job there were a lot of legacy C and C++ applications. They wanted to replace some components with Java local applications because Eclipse RCP was the new cool thing.
So we would build it and then have 2-4 weeks for performance tuning. It basically involved one person from the team attaching Yourkit profiler and either nudging code to pure OO or C like procedural at bottleneck points.
Every single time the result used less CPU and RAM than the C/C++ application when running through the original applications test packs. Even when those applications had gone through multiple rounds of performance tuning.
We got given some time to figure out why, our conclusion was while any one part of the Java application would be slower, the reduced mental load lead to better performance in total.