title: Is passing null in to a method acceptable
body: <p>Null is an odd data type for me, it seems as though it is wrong to ever use, maybe its the null pointer errors i got so often as a beginner that now have me associating any instance of null to some kind of evil!</p>
  
  <p>Anyway my question is </p>
  
  <p>in some cases is it ok to use null as a parameter? for example, a method may need a and b to do a task, but in some cases it may only need a. Is parsing in null ok for b in those odd instances and checking if(b==null) then we know what called it?</p>
  
  <p>Or am i way of the mark here? </p>
  
  <p>i must admit, what got me wondering whether this was acceptable was, the method in question could be overlaoded, but it would have a difference of possibly 5 or 6 lines out of the whole method. This made me worried about code duplication.</p>