I am writing a method that can advance the date by a given number of weeks. Here is my code:
public class Date {
int year;
int month;
int day;
public Date (int year, int month, int day){
this.year = year;
this.month = month;
this.day = day;
}
public void addWeeks (int weeks){
int week = weeks * 7;
DateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.DAY_OF_MONTH, this.day);
calendar.set(Calendar.MONTH, this.month);
calendar.set(Calendar.YEAR, this.year);
calendar.add(Calendar.DAY_OF_MONTH, week);
System.out.println();
System.out.println("Date after adding " + weeks + " weeks is: " + dateFormat.format(calendar.getTime()));
}
So if I pass today's date to year, month and day. (03/08/2019) and then call the addWeeks(1) for example, then the date should advance as (03/15/2019) but it gives me (04/15/2019). For some reason the month is always 1 more than what I enter. If I enter 2 for the month, it gives 3, if I enter 3 it gives 4.
Here's why:
public static final int MONTH
: Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year in the Gregorian and Julian calendars is JANUARY which is 0; the last depends on the number of months in a year.
So, you need:
calendar.set(Calendar.MONTH, this.month-1);
Jan: 0
Feb: 1
Mar: 2
Apr: 3
May: 4
Jun: 5
Jul: 6
Aug: 7
Sep: 8
Oct: 9
Nov: 10
Dec: 11