1、程式碼

public class DateUtils {

    public static void main(String[] args) throws ParseException {
        String str = "2021-11-01 06:07:08";
        Date date = str2Date(str);
        System.out.println("當天時間為: " + str);
        System.out.println("昨天時間為: " + getYesterday(date));
        System.out.println("前天時間為: " + getBeforeYesterday(date));
    }

    // 字串轉日期
    public static Date str2Date(String str) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date date = sdf.parse(str);
        return date;
    }

    // 獲取昨天的時間格式字串
    public static String getYesterday(Date date) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Calendar calendar = new GregorianCalendar();
        calendar.setTime(date);
        calendar.add(calendar.DATE, -1);
        return sdf.format(calendar.getTime());
    }

    // 獲取前天的時間格式字串
    public static String getBeforeYesterday(Date date) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Calendar calendar = new GregorianCalendar();
        calendar.setTime(date);
        calendar.add(calendar.DATE, -2);
        return sdf.format(calendar.getTime());
    }
}
 

2、測試結果