output: #fixed code
                                  @Override
      public HWDiskStore[] getDisks() {
          List<HWDiskStore> result;
          result = new ArrayList<>();
          readMap.clear();
          writeMap.clear();
          populateReadWriteMaps();
  
          Map<String, List<Object>> vals = WmiUtil.selectObjectsFrom(null, "Win32_DiskDrive",
                  "Name,Manufacturer,Model,SerialNumber,Size,Index", null, DRIVE_TYPES);
          for (int i = 0; i < vals.get("Name").size(); i++) {
              HWDiskStore ds = new HWDiskStore();
              ds.setName((String) vals.get("Name").get(i));
              ds.setModel(String.format("%s %s", vals.get("Model").get(i), vals.get("Manufacturer").get(i)).trim());
              // Most vendors store serial # as a hex string; convert
              ds.setSerial(ParseUtil.hexStringToString((String) vals.get("SerialNumber").get(i)));
              String index = vals.get("Index").get(i).toString();
              if (readMap.containsKey(index)) {
                  ds.setReads(readMap.get(index));
              }
              if (writeMap.containsKey(index)) {
                  ds.setWrites(writeMap.get(index));
              }
              // If successful this line is the desired value
              try {
                  ds.setSize(Long.parseLong((String) vals.get("Size").get(i)));
              } catch (NumberFormatException e) {
                  // If we failed to parse, give up
                  // This is expected for an empty string on some drives
                  ds.setSize(0L);
              }
              result.add(ds);
          }
          return result.toArray(new HWDiskStore[result.size()]);
      }
input: #vulnerable code 
                                  @Override
      public HWDiskStore[] getDisks() {
          List<HWDiskStore> result;
          result = new ArrayList<>();
  
          Map<String, List<String>> vals = WmiUtil.selectStringsFrom(null, "Win32_DiskDrive",
                  "Name,Manufacturer,Model,SerialNumber,Size", null);
          for (int i = 0; i < vals.get("Name").size(); i++) {
              HWDiskStore ds = new HWDiskStore();
              ds.setName(vals.get("Name").get(i));
              ds.setModel(String.format("%s %s", vals.get("Model").get(i), vals.get("Manufacturer").get(i)).trim());
              // Most vendors store serial # as a hex string; convert
              ds.setSerial(ParseUtil.hexStringToString(vals.get("SerialNumber").get(i)));
              // If successful this line is the desired value
              try {
                  ds.setSize(Long.parseLong(vals.get("Size").get(i)));
              } catch (NumberFormatException e) {
                  // If we failed to parse, give up
                  // This is expected for an empty string on some drives
                  ds.setSize(0L);
              }
              result.add(ds);
          }
          return result.toArray(new HWDiskStore[result.size()]);
      } 
                              #location 16 
                              #vulnerability type NULL_DEREFERENCE