Write a method named mean that accepts as a parameter an ArrayList of real numbers, and returns the arithmetic mean (average) of the integers in the list as a real number. For example, if the list passed contains {2.0, 4.5, 6.5, 1.0}, your method should return 3.5. If the list is empty, return 0.0. Do not modify the list that is passed in.

Make sure to just write one method, not a whole class