output: #fixed code
                                  private void setPostUsed(GCEvent event, StartElement startEl) {
          long total = NumberParser.parseLong(getAttributeValue(startEl, "total"));
          event.setPostUsed(toKiloBytes(total - NumberParser.parseLong(getAttributeValue(startEl, "free"))));
      }
input: #vulnerable code 
                                  private void setPostUsed(GCEvent event, StartElement startEl) {
          long total = NumberParser.parseInt(getAttributeValue(startEl, "total"));
          event.setPostUsed(toKiloBytes(total - NumberParser.parseInt(getAttributeValue(startEl, "free"))));
      } 
                              #location 2 
                              #vulnerability type NULL_DEREFERENCE