Questions about the Calendar/Date class,BUG?

User_IZ661

• My English is poor, but I hope to describe it clearly
• precondition: JDK 1.8

I need to create a tool class to handle the date: convert the input string to the date N days ago

Several of Date's constructors were found to be out of date during use: "@Deprecated" , so I chose "Date(long date)" , but found problems with the handling of February

• This method is to process strings into dates

public static Date stringToDate(String str) {
    SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");
    Date date = null;
    try {
        date = format.parse(str);
    } catch (ParseException e) {
        e.printStackTrace();
    }

    return date;
}

• Use "Date(long date)" (error)

public static Date getNDays(String str, int n) {
    Calendar init = Calendar.getInstance();
    init.set(1970,01,01,00,00,00);

    Calendar calendar = Calendar.getInstance();
    Date date = DateUtil.stringToDate(str);
    calendar.setTime(date);
    calendar.add(Calendar.DATE, -n);
    calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) + 1);

    long begin = init.getTimeInMillis();
    long now = calendar.getTimeInMillis();

    return new Date(now - begin);
}

• use "Date(int year, int month, int date, int hrs, int min, int sec)" but @Deprecated (true)

public static Date getNDays(String str, int n) {
    Calendar calendar = Calendar.getInstance();
    Date date = DateUtil.stringToDate(str);

    calendar.setTime(date);
    calendar.add(Calendar.DATE, -n);

    return new Date(
            calendar.get(Calendar.YEAR) - 1900,
            calendar.get(Calendar.MONTH),
            calendar.get(Calendar.DAY_OF_MONTH),
            0,
            0,
            0
    );
}

I hope to receive a reply,tanks!

email: [email protected]