anchor.diff:  
   
   String prevSortByStr = (String) request.getSession().getAttribute("sortBy");
  -if (prevSortByStr != null) {
  +if (prevSortByStr != null && prevSortByStr.compareTo("null") != 0) {
       prevSortBy = Integer.parseInt(prevSortByStr);
   }
   
  
positive.code: }
  
  
  if (resultsPerPage != null) {
      bean.setPageSize(Integer.parseInt(resultsPerPage));
  }
  
  
negative.code: 
  String page_number = HTTPUtils.cleanXSS((String) request.getParameter("page_number"));
  int pageNum = 0;
  if (page_number != null && page_number.compareTo("null") != 0) {
      pageNum = Integer.parseInt(page_number);
  }
  
  