How to convert java.lang.Object to ArrayList?

You can create a static util method that converts any collection to a Java List

public static List<?> convertObjectToList(Object obj) {
    List<?> list = new ArrayList<>();
    if (obj.getClass().isArray()) {
        list = Arrays.asList((Object[])obj);
    } else if (obj instanceof Collection) {
        list = new ArrayList<>((Collection<?>)obj);
    }
    return list;
}

you can also mix the validation below:

public static boolean isCollection(Object obj) {
  return obj.getClass().isArray() || obj instanceof Collection;
}