POI EXCEL列宽自适应中文情况下不自动适应问题

for (int columnNum = 0; columnNum <= titles.length; columnNum++) {
int columnWidth = sheet.getColumnWidth(columnNum) / 256;
for (int rowNum = 0; rowNum < sheet.getLastRowNum(); rowNum++) {
HSSFRow currentRow;
//当前行未被使用过
if (sheet.getRow(rowNum) == null) {
currentRow = sheet.createRow(rowNum);
} else {
currentRow = sheet.getRow(rowNum);
}

if (currentRow.getCell(columnNum) != null) {
HSSFCell currentCell = currentRow.getCell(columnNum);
if (currentCell.getCellType() == HSSFCell.CELL_TYPE_STRING) {
int length = currentCell.getStringCellValue().getBytes().length;
if (columnWidth < length) {
columnWidth = length;
}
}

}
}
sheet.setColumnWidth(columnNum, columnWidth * 256);
}