java 时间转换帮助类

public static void main(String[]args) throws ParseException {
String DATE_FORMAT = "yyyy-MM-dd";
SimpleDateFormat formatter = new SimpleDateFormat(DATE_FORMAT);
Date date_end= formatter.parse("2017-10-30");
Date date_start= formatter.parse("2017-10-25");
Long l_end= date_end.getTime()/1000;
Long l_start=date_start.getTime()/1000;
Long span=l_end-l_start;//432000  5天
System.out.println(31*24*3600);
//test12();
}