Do not worry - I started to programming in Java also after long pause (more than 10 years) in my early 30s, now I am 6 years in Java development and I greatly increase my value on the market and it is fun. Java is simple comparing to C++ so do not worry and start with something. More or less nowadays is more about knowing libraries/frameworks and combine them together. It is doable if you have basics from C++. At the end it is just about taking data from point A and transfer them to point B with some transformations on the way (if I take mainstream programming nowadays)
