如何将项保存到特定数组索引的次数返回?

I have a class called LetterCounter. This class processes strings by turning the letters of a string into chars and adding them to an array called counts[] with 26 positions, with 0 corresponding to 'a' and 25 corresponding to 'z'. This is what the process() method looks like.I have a class called LetterCounter. This class