Question

How can I expand an array without knowing its type?

I have an Object[], and I know it contains only, say, Car instances. When I try to typecast it to a Car[], it throws a ClassCastException. I’m working in an environment where Generics are not available.

Must I use a for-loop to copy each element manually into a new array like this:

Car[] cars = new Car[objects.length];
for (int i = 0; i < objects.length; i++) {
    cars[i] = (Car) objects[i];
}

?

Answer 1

Just because the Object[] happens only to contain Cars, doesn’t mean it can be cast to Car[]. You would need to copy the contents of the array to a new Car[], casting where necessary.

Remember that arrays are themselves objects, and their type isn’t governed by what’s in them – it’s the other way around.