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Summary of Java utility classes: Java utility classes

  • This article will be updated with the daily work, as a record.
  • In my daily work, I would unify the time-related methods of many business scenarios into tool classes for use.
  • Convenient for later use.
  • Hope these tool classes are helpful!
  • Click follow oh ~

A collection of time utility classes

Get the time from a week ago

  • Business scenarios:

    • You need to collect statistics on the data list within one week after the current time is rolled back.
  • public static String sevenDatysAgo(a){
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        Calendar c = Calendar.getInstance();
        // Last seven days
        c.setTime(new Date());
        c.add(Calendar.DATE, - 7);
        Date d = c.getTime();
        String day = format.format(d);
        day = day+"00:00:00";
        return day;
}
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  • Demonstration effect

  •     public static void main(String[] args) {
       // This method returns the current time one week ago zero minutes zero seconds
        System.out.println(sevenDatysAgo());
    }
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②, get the month before several months

  • The business scenario

    • You can choose to use this tool class if it involves statistics across the New Year.
    • For example, the current data analysis starts three months back.
  • public static String[] getDateBeforeMonth(String dateKey, Integer length){
        String[] arrData = new String[2];
         try {
            //dateKey is the date passed in, and length is the month that needs to be pushed forward
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM");
            Calendar c = Calendar.getInstance();
            Date nowMonth = format.parse(dateKey);
            c.setTime(nowMonth);
            c.add(Calendar.MONTH, -length);
            Date m3 = c.getTime();
            String mon3 = format.format(m3);
            System.out.println("The past"+length+"Month:"+mon3);
            arrData[0] = mon3;
            arrData[1] = dateKey;
            return arrData;
            } catch (ParseException e) {
            e.printStackTrace();
         }
         return arrData;
}
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  • Demonstration effect

  • public static void main(String[] args) {
        getDateBeforeMonth("The 2021-08".6);
}
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③ Hours turn to minutes

  • The business scenario

    • Statistics page for easy viewing.
  • public static int hoursTOminute(String date) {
        String[] dataArr = date.split("Hour");
        int Hminute = Integer.parseInt(dataArr[0]) * 60;
        int Mminute = Integer.parseInt(dataArr[1].replace("Points".""));
        int hoursToMinute = Hminute + Mminute;
        return hoursToMinute;
}
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  • Demonstration effect

  • public static void main(String[] args) {
        String str = "3 hours and 24 minutes.";
        System.out.println(str+":"+hoursTOminute(str));
}
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④ Get the date of N hours

  • The business scenario

    • It is generally used for data batch running
    • For example, fake data to make pages move and frame time frames!
  • Public static String getAfterHourCycleByHour(Date Date, Date Date, Date Date) String days) { int daysInt = Integer.parseInt(days); Calendar canlendar = Calendar.getInstance(); canlendar.setTime(date); canlendar.add(Calendar.HOUR, daysInt); SimpleDateFormat sdfd = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String dateStr = sdfd.format(canlendar.getTime()); return dateStr; }Copy the code

  • Demonstration effect

  • public class test {
    public static void main(String[] args) {
        Date date = new Date();
        String endTime = DateUtils.getAfterHourCycleByHour(date, "2"); System.out.println(endTime); }}Copy the code

Calculate a person’s age according to the date of birth

  • The business scenario

    • This is the age of a person based on the date of birth entered by someone else. The scenario is very simple.
  • /** * Age is calculated based on birth date **@returnFuture dates return 0 */
    public static int getAge(Date birthDay) throws Exception {
        Calendar cal = Calendar.getInstance();

        if (cal.before(birthDay)) {
            return 0;
        }

        int yearNow = cal.get(Calendar.YEAR);
        int monthNow = cal.get(Calendar.MONTH);
        int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);
        cal.setTime(birthDay);

        int yearBirth = cal.get(Calendar.YEAR);
        int monthBirth = cal.get(Calendar.MONTH);
        int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);

        int age = yearNow - yearBirth;

        if (monthNow <= monthBirth) {
            if (monthNow == monthBirth) {
                if(dayOfMonthNow < dayOfMonthBirth) { age--; }}else{ age--; }}return age;
    }
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  • Demonstration effect

  • public class test {
    public static void main(String[] args) throws Exception{
        DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Date birthDay = df.parse("1996-08-27"); System.out.println(DateUtils.getAge(birthDay)); }}Copy the code

Get the start time of the week

  • The business scenario

    • Statistical analysis of this week’s data
  • public static Date getBeginDayOfWeek(a) {
        Date date = new Date();
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int dayofweek = cal.get(Calendar.DAY_OF_WEEK);
        if (dayofweek == 1) {
            dayofweek += 7;
        }
        cal.add(Calendar.DATE, 2 - dayofweek);
        return getDayStartTime(cal.getTime());
}
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  • Demonstration effect

  • public class test {
    public static void main(String[] args) throws Exception{ System.out.println(DateUtils.getBeginDayOfWeek()); }}Copy the code

To be continued

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