code: public static void validateNull( Object object, String identifier )
          throws PostConditionException
      {
          if( object == null )
          {
              return;
          }
          throw new PostConditionException( identifier + " was NOT NULL." );
      }
docs: Validates that the object is null.
  
  @param object     The object to be validated.
  @param identifier The name of the object.
  
  @throws PostConditionException if the object is not null.