It's July. You haven't worked on this yet? Luckily for you, C++ and Java are relatively close. Other languages would be more difficult.
In short, what you are trying to do is write a compiler, but one that output code in another high level language vs. machine code. This is quite a big job. However, you might be able to take a number of shortcuts. For example, you could skip the C++ preprocessor (i.e. macros).
What you have to do is look at the statements allowed in the source language and see how they translate to the other. How do basic types compare? How do you declare classes and functions?
You will have to write a parser for the source language. This is probably the most difficult part. Maybe you can restrict the number of language elements at first to make the problem tractable.
In the end, it is possible. since both language are compilable to machine(-ish) languages, they can be translated in theory. In practice, because of differences in system libraries there will be a lot of rote work.
You can't expect YA to come up with a major part of your thesis. You are out of the range by many orders of magnitude.