I think their complexity is very different

C++ the language is exceptionally complicated, but the ecosystem is relatively simple

Java is the opposite, the language itself is simple enough but the ecosystem is humongous (spring/J2EE, maven/gradle, n^2 logging frameworks/adapters, application servers, anything involving classloaders/annotation processing/dynamic bytecode manipulation, ...)

syntactically they look similar, but other than that there's not much in the way of transferable skills between the two