This may give me another answer had I posted in the java section.

I have been making small games in Java.

I am starting a project in unity. Seems like unity uses javascript, C# or Boo. Of those 3 I would like to use C#.

Is it possible to use some of my existing Java code or should i translate it.

If I have to translate my java code, does someone have experience with the various translators out there ?
Is it useful or does it only work with very simple code ?

C# feels a lot like java. A lot of people call it C's version of Java. Translators? You mean something that will compile Java code to C#? You're better off just rewriting it.

There are some source code translators. Like these. http://designzum.com/2014/03/27/best-tools-to-convert-java-to-c-source-code/

Maybe you are right. Just thought that it would help kickstart it if I saw some of my own code in C#.

C#

I know there are source code translators. I never said they didn't exist. What do you think a compiler is? It takes a source language and translates it into an intermediary (usually machine code/byte code). Any language that has a Context-free grammar can compiled into another language with a context-free grammar through common compilation methods (lexical and syntactic analysis). Thus, if you look hard enough you will find someone who has created some translator (compiler) from one language into another. They just aren't very good. Clunky at times. Which is why I said you are better off just rewriting your Java into C#.