POI如何自动调整Excel单元格中字体的大小

public static void main(String[] args) {

    try (InputStream is = new FileInputStream("E:\\test1.xls");
         Workbook book = new HSSFWorkbook(is);) {

        Cell cell = book.getSheetAt(0).getRow(3).getCell(5);
        String str = "一二三四五六七八九十一二三四五六七八九十一二三四五六七八九十";
        cell.setCellValue(str);

        setFontSize(book, cell);

        File f = new File("E:\\test2.xls");
        FileOutputStream out = new FileOutputStream(f);
        book.write(out);
    } catch (IOException e) {
        //return;
    }
}

/**
 * 设置单元格字体大小
 */
private static void setFontSize(Workbook book, Cell cell) {
    Font font = book.createFont();
    font.setFontName("EUDC");
    cell.getCellStyle().setWrapText(true);
    cell.getCellStyle().setFont(font);
    for (short k = 10; k >= 5; k--) {
        font.setFontHeightInPoints(k);
        if (checkCellReasonable(cell, k)) {
            break;
        }
    }
}

/**
 * 校验单元格中的字体大小是否合理
 */
private static boolean checkCellReasonable(Cell cell, short fontSize) {
    int sum = cell.getStringCellValue().length();
    double cellWidth = getTotalWidth(cell);
    double fontWidth = (double) fontSize / 72 * 96 * 2;
    double cellHeight = cell.getRow().getHeightInPoints();
    double rows1 = fontWidth * sum / cellWidth;
    double rows2 = cellHeight / fontSize;
    return rows2 >= rows1;
}

/**
 * 获取单元格的总宽度（单位：像素）
 */
private static double getTotalWidth(Cell cell) {
    int x = getColNum(cell.getSheet(), cell.getRowIndex(), cell.getColumnIndex());
    double totalWidthInPixels = 0;
    for (int i = 0; i < x; i++) {
        totalWidthInPixels += cell.getSheet().getColumnWidthInPixels(i + cell.getColumnIndex());
    }
    return totalWidthInPixels;
}

/**
 * 获取单元格的列数，如果是合并单元格，就获取总的列数
 */
private static int getColNum(Sheet sheet, int row, int column) {
    int sheetMergeCount = sheet.getNumMergedRegions();
    //判断该单元格是否是合并区域的内容
    for (int i = 0; i < sheetMergeCount; i++) {
        CellRangeAddress ca = sheet.getMergedRegion(i);
        int firstColumn = ca.getFirstColumn();
        int lastColumn = ca.getLastColumn();
        int firstRow = ca.getFirstRow();
        int lastRow = ca.getLastRow();

        if (row >= firstRow && row <= lastRow && column >= firstColumn && column <= lastColumn) {
            return lastColumn - firstColumn + 1;
        }
    }
    return 1;
}