java - 日期相减、四舍五入

public static void convertYearStudy(Connection conn, ResultSet rs, String dateStartStr, String dateEndStr, String updateField) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String yearStr = null;
Date dateStart;
Date dateEnd;
if (dateStartStr != null && dateEndStr != null) {
try {
dateStart = sdf.parse(dateStartStr);
dateEnd = sdf.parse(dateEndStr);
double yearDecimal = ((dateEnd.getTime() - dateStart.getTime()) / (1000 * 60 * 60 * 24)) / 365.0; // 日期相减(年)
BigDecimal year = new BigDecimal(yearDecimal).setScale(0, BigDecimal.ROUND_HALF_UP); 	// 四舍五入
yearStr = year.toString();
} catch (ParseException e) {
e.printStackTrace();
}
}
update(conn, rs, updateField, yearStr);
}