Java Date Calculation example - Add and Subtract days

Its very easy with the help of Calendar.add() method. First get the Calendar instance for your given date and then use the add method. For date subtraction just use a negative number in the parameter. Here is a sample code ...

package com.as400samplecode;

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

public class DateCalculations {

 public static void main(String[] args) {

  String myInputDate = "20120607";
  
  String myFutureDate = addDays(myInputDate, "30");
  System.out.println(myFutureDate);
  
  String myPastDate = subtractDays(myInputDate, "30");
  System.out.println(myPastDate);
  
 } 

 private static String addDays(String fromDate, String days) {

  Calendar c = Calendar.getInstance();
  DateFormat df = new SimpleDateFormat("yyyyMMdd");
  try {
   Date myDate = df.parse(fromDate.trim());
   c.setTime(myDate);
   c.add(Calendar.DATE, Integer.parseInt(days));
  } catch (ParseException e) {
   e.printStackTrace();
  }

  String toDate = df.format(c.getTime()); 
  return toDate;

 }
 
 private static String subtractDays(String fromDate, String days) {

  Calendar c = Calendar.getInstance();
  DateFormat df = new SimpleDateFormat("yyyyMMdd");
  try {
   Date myDate = df.parse(fromDate.trim());
   c.setTime(myDate);
   c.add(Calendar.DATE, (Integer.parseInt(days)*-1));
  } catch (ParseException e) {
   e.printStackTrace();
  }

  String toDate = df.format(c.getTime()); 
  return toDate;

 }

}