Is it possible to use a class structure written in Java in C#?

Question

Java

Actually a subject.
Why is it necessary?
It is necessary to develop and write a small application (thesis project) for Android and for Windows. The essence of the applications is the same, the functions are completely repeated, just different graphical interfaces. The set of objects that applications operate on is, of course, also the same. There is an idea to write a class structure once, and then use the written structure both in a Java application on a mobile device and in a C # application under Windows.
Total 2 questions.
1. Is it reasonable to try to include the structure of objects described in one language in another language? Yes, writing once may be easy, but then it will be much more difficult to maintain, right? You will have to edit in several places at the same time, there is a chance of making a mistake (and this will 100% happen).
2. Is it possible in principle and if so, then please poke how exactly you need to apply Google-

Answer 1

The languages ​​are practically copies, write in one, then transfer to another and correct the mistakes, of which there will not be many.

Answer 2

Use mono.

Answer 3

And the option to write in Java under Windows is not considered at all?