一.概述

1. 在sheet中，sheet的列号为A、B。。。Z、AA、AB。。。

2. 但是有时我们想用数字表示列号，就需要字符串与数字之间相互转换

二.方法

1.位置：org.apache.poi.ss.util.CellReference

2.字符串转数字方法

/**
     * takes in a column reference portion of a CellRef and converts it from
     * ALPHA-26 number format to 0-based base 10.
     * 'A' -> 0
     * 'Z' -> 25
     * 'AA' -> 26
     * 'IV' -> 255
     * @return zero based column index
     */
    public static int convertColStringToIndex(String ref) {
        int retval=0;
        char[] refs = ref.toUpperCase(Locale.ROOT).toCharArray();
        for (int k=0; k<refs.length; k++) {
            char thechar = refs[k];
            if (thechar == ABSOLUTE_REFERENCE_MARKER) {
                if (k != 0) {
                    throw new IllegalArgumentException("Bad col ref format '" + ref + "'");
                }
                continue;
            }

            // Character is uppercase letter, find relative value to A
            retval = (retval * 26) + (thechar - 'A' + 1);
        }
        return retval-1;
    }

3.数字转字符串

/**
     * Takes in a 0-based base-10 column and returns a ALPHA-26
     *  representation.
     * eg column #3 -> D
     */
    public static String convertNumToColString(int col) {
        // Excel counts column A as the 1st column, we
        //  treat it as the 0th one
        int excelColNum = col + 1;

        StringBuilder colRef = new StringBuilder(2);
        int colRemain = excelColNum;

        while(colRemain > 0) {
            int thisPart = colRemain % 26;
            if(thisPart == 0) { thisPart = 26; }
            colRemain = (colRemain - thisPart) / 26;

            // The letter A is at 65
            char colChar = (char)(thisPart+64);
            colRef.insert(0, colChar);
        }

        return colRef.toString();
    }