一、數字轉字母

//數字轉字母 1-26 ： A-Z
private String numberToLetter(int num) {
    if (num <= 0) {
        return null;
    }
    String letter = "";
    num--;
    do {
        if (letter.length() > 0) {
            num--;
        }
        letter = ((char) (num % 26 + (int) 'A')) + letter;
        num = (int
 
) ((num - num % 26) / 26);
    } while (num > 0);

    return letter;
}

二、字母轉數字

//字母轉數字  A-Z ：1-26
public int letterToNumber(String letter) {
    int length = letter.length();
    int num = 0;
    int number = 0;
    for(int i = 0; i < length; i++) {
        char ch = letter.charAt(length - i - 1
 
);
        num = (int)(ch - 'A' + 1) ;
        num *= Math.pow(26, i);
        number += num;
    }
    return number;
}