title: How to create own filetype?
body: <p>I want to create own filetype to save objects in my app. Basically, I urgently do not need new filetype, but it will be better.</p>
  
  <p>I have class. For example Car. It has constructor (String name, String color, int length, Driver driver). When a car is created (its instance), how to save it like a file?</p>