Now, obviously this relies on knowing that there is at least one element in the list, and, if there is more than one, which one is the correct one
On a Mac no two devices will be given the same name. It the device is not on the list it will default to the first device in the list.
I have found that the list on a Mac is sometimes in the order the devices were added and sometimes in the reverse order depending on the version of Processing. The "bad" way just picks the first device on the list. The way I have developed attaches a specific arduino. This is usefull when there is more than one arduino in your setup. The printing of what device was chosen is a good reminder that things are set up correctly.