CODEWITHSUNDEEP
javadatetimecalendar
Anuj Kulkarni
Anuj Kulkarni

Reputation: 2199

How to find out start of next day using Java

In my simple application, I am storing the timestamp into the database table programmatically by using new Timestamp(System.currentTimeMillis()).

Now, I have one condition, where I have to store the onClick count for a particular day, and all onClick counts into two different columns.

So for that, I need to find out onClicks for today. So how can I find out if the time onclicks occur are today? I mean for say 1st August, I want all the onclick counts in one column and all previous onClick counts into another column.

*In simple words - storing clicks for today in one column and storing clicks till now in another column, so if today expires, I want to add clicks for today with total clicks and then make the today_clicks column count to 0 and then when there is new click on next day, store it in the today_clicks column by starting it with count 1*

How can I decide that? Which Java class should I use for that?

Upvotes: 2

Views: 1823

Answers (3)

MadProgrammer
MadProgrammer

Reputation: 347214

First, I'd suggest taking a look at Joda Time.

Second, I'd take a look at Calendar:

Calendar lower = Calendar.getInstance();
lower.setTime(new Date());
lower.set(Calendar.HOUR_OF_DAY, 0);
lower.set(Calendar.MINUTE, 0);
lower.set(Calendar.SECOND, 0);
lower.set(Calendar.MILLISECOND, 0);

Calendar upper = Calendar.getInstance();
upper.setTime(new Date());
upper.set(Calendar.HOUR_OF_DAY, 23);
upper.set(Calendar.MINUTE, 59);
upper.set(Calendar.SECOND, 59);
upper.set(Calendar.MILLISECOND, 99);

Date clickTime = new Date(timeInMillis);
if (clickTime.after(lower.getTime()) && clickTime.before(upper.getTime())) {
    // Is today
}

Upvotes: 0

akf
akf

Reputation: 39485

If I understand correctly, you are looking for a way to best store your data in your database. You have decided to maintain a clicks-for-today column and a clicks-until-now column. (I may be off base on this, but it wasnt completely clear from the question)

I would suggest that you dont try to manipulate the data from column to column as you have described, but instead do so by maintaining click counts per day:

 date | count
------|-------
Jul 31| 10876
Aug  1| 15721

(where date is a in the db timestamp/date datatype)

How would this work?

At startup, you could then bring into memory all rows, and sum their counts to get a clicks-until-now value, if needed.

You then have special handling for today's row, where you update the appropriate context with the clicks-for-today value.

To determine whether you've passed a day threshold, you could simply:

  1. maintain a Calendar instance for 'today' (call it todayCal)
  2. generate a new Calendar each time you record a click (call it clickCal)
  3. test Calendar.DAY_OF_YEAR from todayCal and clickCal
  4. if you identify a day roll, you persist the clicks-for-today in the db and initialized a new clicks-for-today.
  5. if you are maintaining total click count in memory, you can do the math at this point.

Upvotes: 0

tenorsax
tenorsax

Reputation: 21223

Not sure if that is what are you after. To get start of next day you can use Calendar: 

public static Date nextDayStart(Date date) {
    Calendar cal = Calendar.getInstance();
    cal.setTime(date);
    cal.set(Calendar.HOUR_OF_DAY, 0);
    cal.set(Calendar.MINUTE, 0);
    cal.set(Calendar.SECOND, 0);
    cal.set(Calendar.MILLISECOND, 0);
    cal.add(Calendar.DATE, 1);

    return cal.getTime();
}

To get tomorrow: 

Date tomorrow = nextDayStart(new Date());

To get Timestamp from Date:

Timestamp s = new Timestamp(date.getTime());

Upvotes: 4

Related Questions