And what's wrong with java? Why do you think that c++ is better for a crypto coin?
Java is interpreted, not compiled; it's under the control of Oracle Corporation. It's probably fine for a prototyping language and for quick interactive demos. But it does add a layer of complexity, which slows things down (not a huge problem with today's hardware) and creates another failure point.
Java is compiled as bytecode and run by JVM. It's not just oracle, there are also other VMs, including Open JDK, which is open source. It doesn't add another "layer of complexity". It adds more security and versatility (Same compiled bytecode behaves exactly same on Windows, Linux, Mac; you can't always say that about C++ apps, making it less secure). It's much harder to write secure C++ applications, especially due to things like pointers that arbitrarily access memory and buffer overruns. It's much easier to miss bugs in C++ applications. It's much harder to fix bugs in C++ applications, even if you know there is a bug. Vast majority of server side apps are written in Java. That includes almost all banks,, amazon, ebay. There is really no reason to write crypto in C++ as you don't need native integration with operating system and faster startups, two things that C++ does better.
I am pretty sure C++ is absolutely worst choice for crypto. Python is probably the best (Electrum?).