Question

I am trying to write a method that will take in an array and return another array of the same type, double the size and with the same contents. However I need a way of assigning the array type to something that will not be known until runtime. example:

public object[] doubleArray(object[] array) {
---[] arrayCopy = new ---[array.length*2];
//copy content
for (int i = 0; i < array.length; i++) {
        arrayCopy[i] = array[i];
}
return arrayCopy;
}

The array passed in will not be known until runtime.
Thanks any help will be greatly appreciated

PS I realise that managing of array sizes can be done with ArrayLists etc but for this purposes it would be great to keep things to arrays.

Answer 1

What you can do for a generic array is

public static <A> A doubleArray(A array) {
    int length = Array.getLength(array);
    Class<?> componentType = array.getClass().getComponentType();
    A copy = (A) Array.newInstance(componentType, length * 2);
    System.arraycopy(array, 0, copy, 0, length);
    return copy;
}

Note: this will work for all arrays including primitive arrays.

int[] ints = doubleArray(new int[4]);
String[] strings = doubleArray("a,b,c,d,e,f".split(","));