Simple java date related question

Question

Hi Friends,
I have written this custom date class that compares two dates. The user can enter any number of days,and it should calculate the next date,is that possible???
public class Date implements Comparable {
     private int month, day, year;
     public Date(int m, int d, int y) {
          month = m;
          day = d;
          year = y;
     public int compareTo(Object o) {
          Date a = this;
          Date b = (Date) o;
          if (a.year < b.year) return -1;
          if (a.year > b.year) return 1;
          if (a.month < b.month) return -1;
          if (a.month > b.month) return 1;
          if (a.day < b.day) return -1;
          if (a.day > b.day) return 1;
          return 0;
     public String toString() {
          return month + "/" + day + "/" + year;
     public static void main(String[] args) {
          Date d1 = new Date(21, 03, 2007);
          int days = Integer.parseInt(args[0]);
          System.out.println("New date is:"); // Need to print new date
Expected output:
java Date 30
New date is: 04/20/2007If this is not possible with this class,how can we do this, any ideas.
Your help would be appreciated.
Thanks

Answer 1

Hi,
Try this code out:
import java.text.DateFormat;
import java.util.*;
import javax.swing.JOptionPane;
public class SimpleDate {
     private int month, day, year;
     public SimpleDate() {
          Date date = new Date();
         String myString = DateFormat.getDateInstance().format(date);
         StringTokenizer tokens = new StringTokenizer(myString, "/");
         day = Integer.parseInt(tokens.nextToken());
         month = Integer.parseInt(tokens.nextToken());
         year = Integer.parseInt(tokens.nextToken());
     public SimpleDate(String stdate) {
          try {
               StringTokenizer tokens = new StringTokenizer(stdate, "/");
               day = Integer.parseInt(tokens.nextToken());
               month = Integer.parseInt(tokens.nextToken());
               year = Integer.parseInt(tokens.nextToken());
          catch(Exception e) {
               Date date = new Date();
              String myString = DateFormat.getDateInstance().format(date);
              StringTokenizer tokens = new StringTokenizer(myString, "/");
              day = Integer.parseInt(tokens.nextToken());
              month = Integer.parseInt(tokens.nextToken());
              year = Integer.parseInt(tokens.nextToken());
               JOptionPane.showMessageDialog(null, "Invalid String,\nDate set to current", "Invalid String", JOptionPane.ERROR_MESSAGE);
     public SimpleDate(int d, int m, int y) {
          month = m;
          day = d;
          year = y;
     public int compareTo(Object o) {
          SimpleDate a = this;
          SimpleDate b = (SimpleDate) o;
          if (a.year < b.year) return -1;
          if (a.year > b.year) return 1;
          if (a.month < b.month) return -1;
          if (a.month > b.month) return 1;
          if (a.day < b.day) return -1;
          if (a.day > b.day) return 1;
          return 0;
     private int getNumOfDaysInMonth() {
          boolean leap = false;
          int days = 30;
          if (year % 4 == 0) leap = true;
          if ((month == 1) | (month == 3) | (month == 5) | (month == 7) |
                    (month == 8) | (month == 10) | (month == 12)) {
               days = 31;
          if ((month == 4) | (month == 6) | (month == 9) | (month == 11)) {
               days = 30;
          if (month == 2) {
               if (leap) {
                    days = 29;
               else days = 28;
          return days;
     public void addDays(int nums) {
          while (nums > getNumOfDaysInMonth()) {
               nums = nums - getNumOfDaysInMonth();
               addMonths(1);
          day = day + nums;
          while (day > getNumOfDaysInMonth()) {
               day = day - getNumOfDaysInMonth();
               addMonths(1);
     public void addMonths(int nums) {
          while (nums > 12) {
               nums = nums - 12;
               addYears(1);
          month = month + nums;
          while (month > 12) {
               month = month - 12;
               addYears(1);
     public void addYears(int nums) {
          year = year + 1;
     public int getDay() {
          return day;
     public int getMonth() {
          return month;
     public int getYear() {
          return year;
     public String toString() {
          return day + "/" + month + "/" + year;
}I have swapped the day and month around from mm/dd/yyyy to dd/mm/yyyy
but otherwise its still the same basic code