This is a bit pedantic, but I've seen some people use Id as in:



private int userId;
public int getUserId();


and others use:

private int userID;
public int getUserID();


Is one of these a better name than the other? Why? I've seen this done very inconsistently in large projects. If I were to set a standard which would most people be familiar with? Which is the conventional standard?

Consistency is king; pick one or the other, but do it consistently everywhere.

That said, I prefer the first variation, because it doesn't violate camelCase (doing so means you have two style rules to remember, not just one).  

Two capital letters is sometimes used because of this, but an ID is really just a form of Id-entification.
