Constants.Friends[Integer.parseInt(custom.getFriendsList())]

String[] MyList = {"One","Two","Three","Four"};

int pos = Integer.parseInt(custom.getFriendsList());
if (pos < 0 || pos >= Constants.Friends.length) {
    // Handle the error and exit or re-read the pos
}
// Accessing Friends[pos] is safe now:
String friend = Constants.Friends[pos];

int index = Integer.parseInt(custom.getFriendsList());
if (index < 0 || index > list.length)
{
    //notify user that input is invalid retry getting input
}
else
{
    return list[index];
}