(EASY) Given an input String consisting of only uppercase letters, change each letter into a number representing that letter's position in the alphabet and return an ArrayList of Integer values representing those positions. So 'A' becomes 0, 'B' becomes 1, ..., 'Z' becomes 25.

HINT: one easy way to do this is with the charAt method of String, which takes an index and returns the char at that index. Also useful: the char data type is a 16-bit integer, which can be assigned directly into a 32-bit int primitive.