title: Make a variable final in any given moment (after initialization and eventual code)
body: <p>Is it possible to make a variable <code>final</code> in any given moment?
  I would like to decide when its immutable, not just with the first assignment.</p>
  
  <p>It would be perfect, if <code>null</code> would not count as an assignment. So if you would initialize it with null, you would still have a wildcard for the first assignment  after some code, not necessarily in the constructor.</p>