#vulnerable code 
                              @ManagedMetric(description = "Total Disk Space free")
  public long getTotalDiskFree() {
    return (Long) parseStorageTotals().get("hdd").get("free");
  } 
                            #location 3 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              @ManagedMetric(description = "Total Disk Space free")
  public long getTotalDiskFree() {
    return convertPotentialLong(parseStorageTotals().get("hdd").get("free"));
  }