Should I choose to C++ or java for an interview?

I have been coding in c# for three years. However, I am considering to apply for Google, and I need to pick C++ or Java for the interview.

I learned C++ 12 years ago in my first Bachelor's year. I loved the language at the time but never did any serious project with that.

I used Java for my Master's course projects, and later worked in some Java-based company for a short time, so I am pretty comfortable with it but don't know various details and tricks of the language.

A Noogler friend suggested C++, and her reason was that the interviews are likely to be altra good at Java, and may ask language-specific questions that you don't know. During the past couple of weeks, I started reading "Thinking in C++" and learning C++ Standard Library, created a couple of small projects on Visual Studio and stuff. But I am not exactly comfortable with the language. Like I try to code the "Cracking the Coding Interview" questions and with each questions I have to spend hours(!!) to just get to build my C++ code!

I need your ideas on what to do, to continue the path with C++, or to switch to Java (and the past couple of weeks will be sort of wasted time)