Convert unknown type generic list to array

I'm doing a mapping using reflection.

With reflection I can know if each of the the Fields of a Class refers to an attribute of type "array", and also I can get the Class with the type of the array.

Now, I want to set the value of the field of an object. Now, for some reason, I can get the data to fill the object field, but it's not in the form of an array. Is, instead, a Collection<?>.

Just to make it easy to visualize, I have some code like that:

/** create a new T instance, with the data taken from something*/
<T> T convert(Class<T> cls, Object something) {
    T obj = cls.newInstance();
    for (Field field : cls.getFields()) {
        if (field.getType().isArray()) {
            Class<?> arrayType = field.getType().getComponentType();
            Collection<?> collection = this.getData(arrayType, something);

            Object array = CONVERT(collection);

            field.set(obj, arrayData);
        }
    }
}

At the end of the day, I need to convert a Collection<?> object to (hypotetically) a ?[] object, where "?" is dinamically correct.

I know there is collData.toArray(), but it builds an Object[], witch is incompatible; and I know there is collData.toArray(T[]), but I have no idea of how to use it in this context.