java 擷取月、周幾

• • • 擷取月、日 （如：7.13）
    • 擷取星期幾（如：周三）
    • 日期字元串轉時間（如：2020-05-20）
    • 擷取日期前某天或後某天

/**
     * 擷取目前時間月日 7.13
     * @param date
     * @return
     */
    public static String getMonthDay(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        //month從0開始
        int month = calendar.get(Calendar.MONTH) + 1;
        int day = calendar.get(Calendar.DAY_OF_MONTH);
        return month+"."+day;
    }      

/**
     * 擷取周幾
     * @param date
     * @return
     */
    public static String getWeek(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        int weekday = calendar.get(Calendar.DAY_OF_WEEK);
        String week = null;
        if (weekday == 1) {
            week = "周日";
        } else if (weekday == 2) {
            week = "周一";
        } else if (weekday == 3) {
            week = "周二";
        } else if (weekday == 4) {
            week = "周三";
        } else if (weekday == 5) {
            week = "周四";
        } else if (weekday == 6) {
            week = "周五";
        } else if (weekday == 7) {
            week = "周六";
        }
        return week;
    }      

/**
     * 根據日期字元串擷取時間
     * @param str
     * @return
     */
    public static Date getDate(String str) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date parse = null;
        try {
            parse = sdf.parse(str);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return parse;
    }      

/**
     * 擷取目前時間前面某天或者後面某天，date為今天
     * @param amount為-1，表示昨天，amount為1表示明天
     * @param date
     * @return
     */
    public static Date getOtherDay(Date date, int amount) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.DAY_OF_MONTH,amount);
        Date time = calendar.getTime();
        return time;
    }