private static Object serialize()

in firebase-database/src/main/java/com/google/firebase/database/core/utilities/encoding/CustomClassMapper.java [110:170]
61 lines of code
21 McCabe index (conditional complexity)

  private static <T> Object serialize(T o) {
    if (o == null) {
      return null;
    } else if (o instanceof Number) {
      if (o instanceof Float || o instanceof Double) {
        double doubleValue = ((Number) o).doubleValue();
        if (doubleValue <= Long.MAX_VALUE
            && doubleValue >= Long.MIN_VALUE
            && Math.floor(doubleValue) == doubleValue) {
          return ((Number) o).longValue();
        }
        return doubleValue;
      } else if (o instanceof Long || o instanceof Integer) {
        return o;
      } else {
        throw new DatabaseException(
            String.format(
                "Numbers of type %s are not supported, please use an int, long, float or double",
                o.getClass().getSimpleName()));
      }
    } else if (o instanceof String) {
      return o;
    } else if (o instanceof Boolean) {
      return o;
    } else if (o instanceof Character) {
      throw new DatabaseException("Characters are not supported, please use Strings");
    } else if (o instanceof Map) {
      Map<String, Object> result = new HashMap<>();
      for (Map.Entry<Object, Object> entry : ((Map<Object, Object>) o).entrySet()) {
        Object key = entry.getKey();
        if (key instanceof String) {
          String keyString = (String) key;
          result.put(keyString, serialize(entry.getValue()));
        } else {
          throw new DatabaseException("Maps with non-string keys are not supported");
        }
      }
      return result;
    } else if (o instanceof Collection) {
      if (o instanceof List) {
        List<Object> list = (List<Object>) o;
        List<Object> result = new ArrayList<>(list.size());
        for (Object object : list) {
          result.add(serialize(object));
        }
        return result;
      } else {
        throw new DatabaseException(
            "Serializing Collections is not supported, " + "please use Lists instead");
      }
    } else if (o.getClass().isArray()) {
      throw new DatabaseException(
          "Serializing Arrays is not supported, please use Lists " + "instead");
    } else if (o instanceof Enum) {
      return ((Enum<?>) o).name();
    } else {
      Class<T> clazz = (Class<T>) o.getClass();
      BeanMapper<T> mapper = loadOrCreateBeanMapperForClass(clazz);
      return mapper.serialize(o);
    }
  }