how to get previous date in java

Question

I have a String in format yyyyMMdd. Is there a simple way to get a String with previous date in the same format? Thanks

Answer 1

use SimpleDateFormat to parse the String to Date, then subtract one day. after that convert the date to String again.

Answer 2

It's much harder than it should be in Java without library support.

You can parse the given String into a Date object using an instance of the SimpleDateFormat class.

Then you can use Calendar's add() to subtract one day.

Then you can use SimpleDateFormat's format() to get the formatted date as a String.

The Joda Time library a much easier API.

Answer 3

Here is how to do it without Joda Time:

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class Main {

    public static String previousDateString(String dateString) 
            throws ParseException {
        // Create a date formatter using your format string
        DateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");

        // Parse the given date string into a Date object.
        // Note: This can throw a ParseException.
        Date myDate = dateFormat.parse(dateString);

        // Use the Calendar class to subtract one day
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(myDate);
        calendar.add(Calendar.DAY_OF_YEAR, -1);

        // Use the date formatter to produce a formatted date string
        Date previousDate = calendar.getTime();
        String result = dateFormat.format(previousDate);

        return result;
    }

    public static void main(String[] args) {
        String dateString = "20100316";

        try {
            // This will print 20100315
            System.out.println(previousDateString(dateString));
        } catch (ParseException e) {
            System.out.println("Invalid date string");
            e.printStackTrace();
        }
    }
}

Answer 4

I would rewrite these answers a bit.

You can use

        DateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");

        // Get a Date object from the date string
        Date myDate = dateFormat.parse(dateString);

        // this calculation may skip a day (Standard-to-Daylight switch)...
        //oneDayBefore = new Date(myDate.getTime() - (24 * 3600000));

        // if the Date->time xform always places the time as YYYYMMDD 00:00:00
        //   this will be safer.
        oneDayBefore = new Date(myDate.getTime() - 2);

        String result = dateFormat.format(oneDayBefore);

To get the same results as those that are being computed by using Calendar.