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