[crypt00n1t3]

Assuming someone has senior experience in C#, can it be carried over as senior experience as a developer or do companies view this differently and do you start as a junior/medior if you apply for java jobs?

[peter8]

Senior developers are called seniors because they understand Programming patterns, architecture etc. not only just one language

[Eric52]

Should be easy to transition.

[Super_Afternoon]

Being a Senior programmer isn't just the experience with that language. By that point its usually about knowledge of programming in general, problem solving. People/task management as well as mentoring.