I learned java before C++ myself. Java will help you with some minor concepts and basic C-style syntax. The main thing with C++ is you will have to do memory management, you have pointers, structs, graphics, etc, and you will need to understand how compilers work. Unlike Java's compile once, run anywhere scheme, C++ needs to be built for a particular platform (Operating System). I would highly recommend checking out thenewboston on youtube for basic java and C++ tutorials.
Thank you for wanting to learn instead of just C&P code off of others like 90% of people who visit these forums. It will be a difficult road, but well worth it! C++ is a lot of fun once you break the "I can't" barrier.