Cast Object to Array

Question

So I have an Object which MIGHT be an array. It can also be primitive, or a string. If it is an array, it can be an array of literally anything.

I have no problem figuring out if it is an array but I can't seem to cast it into anything that I can iterate through to get the values out of.

// o is an object and clazz is the class of the o
if (clazz == Array.class) {
            Class ofArray = o.getClass().getComponentType();
            String arrayType = ofArray.getName(); // 'Double' for my test case
            //ERROR: [D cannot be cast to [Ljava.lang.Object 
            Object[] objects = (Object[]) o; 
    }

My background is in ruby and php (where it would just work) and the static typing is messing with my head. Any ideas?

EDIT:

This throws the error

[D cannot be cast to [Ljava.lang.Object.

What am I missing?

if (o.getClass().isArray()) {
    Object[] objects = (Object[]) o;  
}

Answer 1

If you do not want to make the switch for all primitive types you could do like this:

if (ofArray.isPrimitive()) {
    int length = Array.getLength(o);
    for (int i = 0; i < length; i++) {
        Object obj = Array.get(o, i);
        System.out.println(obj);
    }
}
else {
    Object[] objects = (Object[]) o;
    for (Object obj : objects) {
        System.out.println(obj);
    }
}

Edit: If you don't want to loop in two different places in your code use this method to convert the primitive arrays to an object array:

static Object[] convertToObjectArray(Object array) {
    Class ofArray = array.getClass().getComponentType();
    if (ofArray.isPrimitive()) {
        List ar = new ArrayList();
        int length = Array.getLength(array);
        for (int i = 0; i < length; i++) {
            ar.add(Array.get(array, i));
        }
        return ar.toArray();
    }
    else {
        return (Object[]) array;
    }
}

Answer 2

This will work for arrays with elements that are sublcasses of Object:

if (clazz.isArray()) {
    Object[] objects = (Object[]) o;
    for (Object obj : objects)
        System.out.println(obj);
}   

If you need to cast the array to an specific array type you could (ab)use instanceof but for, say, just printing the contents as strings, an Object[] suffices.

UPDATE

If the array is of primitive types, you have no option but to test for each one and cast to the correct type, Object[] won't work for this case - but there aren't that many primitive types in Java, so it won't be a gigantic switch :) . This is what I mean:

if (clazz.isArray()) {
    if (clazz.getComponentType().equals(double.class)) {
        double[] numbers = (double[]) o;
        for (double d : numbers)
            System.out.println(d);
    }
}