Java calendar getting weekdays not working

Question

I am trying to get this to output all the weekdays (MON-FRI) between 5/16/2010 (a sunday) and 5/25/2010 (a tuesday). The correct output should be 17,18,19,20,21,24,25. However, the result im getting is 17,18,19,20,21,17,18,19. The other methods just split up the string the date is in

import java.util.*;
public class test
{
    public static void main(String[] args) {

        String startTime = "5/16/2010 11:44 AM";
        String endTime = "5/25/2010 12:00 PM";
        GregorianCalendar startCal = new GregorianCalendar();
        startCal.setLenient(true);
        String[] start = splitString(startTime);   
        //this sets year, month day
        startCal.set(Integer.parseInt(start[2]),Integer.parseInt(start[0])-1,Integer.parseInt(start[1]));
        startCal.set(GregorianCalendar.HOUR, Integer.parseInt(start[3]));
        startCal.set(GregorianCalendar.MINUTE, Integer.parseInt(start[4]));
        if (start[5].equalsIgnoreCase("AM")) { startCal.set(GregorianCalendar.AM_PM, 0); }
        else { startCal.set(GregorianCalendar.AM_PM, 1); }

        GregorianCalendar endCal = new GregorianCalendar();
        endCal.setLenient(true);
        String[] end = splitString(endTime);
        endCal.set(Integer.parseInt(end[2]),Integer.parseInt(end[0])-1,Integer.parseInt(end[1]));
        endCal.set(GregorianCalendar.HOUR, Integer.parseInt(end[3]));
        endCal.set(GregorianCalendar.MINUTE, Integer.parseInt(end[4]));
        if (end[5].equalsIgnoreCase("AM")) { endCal.set(GregorianCalendar.AM_PM, 0); }
        else { endCal.set(GregorianCalendar.AM_PM, 1); }


        for (int i = startCal.get(Calendar.DATE); i < endCal.get(Calendar.DATE); i++)
        {
            startCal.set(Calendar.DATE, i);
            startCal.set(Calendar.DAY_OF_WEEK, i);
            if (startCal.get(Calendar.DAY_OF_WEEK) == Calendar.MONDAY || startCal.get(Calendar.DAY_OF_WEEK) == Calendar.TUESDAY || startCal.get(Calendar.DAY_OF_WEEK) == Calendar.WEDNESDAY || startCal.get(Calendar.DAY_OF_WEEK) == Calendar.THURSDAY || startCal.get(Calendar.DAY_OF_WEEK) == Calendar.FRIDAY)
            {
                System.out.println("\t" + startCal.get(Calendar.DATE));
            }
        }
    }

    private static String[] splitDate(String date)
    {
        String[] temp1 = date.split(" "); // split by space
        String[] temp2 = temp1[0].split("/"); // split by /
        //5/21/2010 10:00 AM
        return temp2; // return 5 21 2010 in one array
    }

    private static String[] splitTime(String date)
    {
        String[] temp1 = date.split(" "); // split by space
        String[] temp2 = temp1[1].split(":"); // split by :
        //5/21/2010 10:00 AM
        String[] temp3 = {temp2[0], temp2[1], temp1[2]};
        return temp3; // return 10 00 AM in one array
    }

    private static String[] splitString(String date)
    {
        String[] temp1 = splitDate(date);
        String[] temp2 = splitTime(date);
        String[] temp3 = new String[6];
        return dateFill(temp3, temp2[0], temp2[1], temp2[2], temp1[0], temp1[1], temp1[2]);
    }

    private static String[] dateFill(String[] date, String hours, String minutes, String ampm, String month, String day, String year) {
        date[0] = month;
        date[1] = day;
        date[2] = year;
        date[3] = hours;
        date[4] = minutes;
        date[5] = ampm;
        return date;
    }

    private String dateString(String[] date) {
        //return month+" "+day+", "+year+" "+hours+":"+minutes+" "+ampm
        //5/21/2010 10:00 AM
        return date[3]+"/"+date[4]+"/ "+date[5]+" "+date[0]+":"+date[1]+" "+date[2];
    }
}

Answer 1

This code isn't good.

I don't understand why you're doing all this parsing of Strings to get to Date and visa versa when you have java.text.DateFormat and java.text.SimpleDateFormat to do it easily for you.

I think this is better. See if you agree:

package com.contacts.util;

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

public class DateUtils
{
    private static final DateFormat DEFAULT_FORMAT = new SimpleDateFormat("dd-MMM-yyyy");

    public static void main(String[] args)
    {
        try
        {
            Date startDate = ((args.length > 0) ? DEFAULT_FORMAT.parse(args[0]) : new Date());
            Date endDate   = ((args.length > 1) ? DEFAULT_FORMAT.parse(args[1]) : new Date());

            List<Date> weekdays = DateUtils.getWeekdays(startDate, endDate);
            Calendar calendar = Calendar.getInstance();
            for (Date d : weekdays)
            {
                calendar.setTime(d);
                int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);
                int month = calendar.get(Calendar.MONTH);
                int year = calendar.get(Calendar.YEAR);
    //          System.out.println(DEFAULT_FORMAT.format(d));
                System.out.println("day: " + dayOfMonth + " month: " + (month+1) + " year: " + year);
            }
        }
        catch (ParseException e)
        {
            e.printStackTrace();
        }
    }

    public static List<Date> getWeekdays(Date startDate, Date endDate)
    {
        List<Date> weekdays = new ArrayList<Date>();

        if ((startDate == null) || (endDate == null))
            return weekdays;

        if (startDate.equals(endDate))
        {
            if (isWeekday(startDate))
            {
                weekdays.add(startDate);
            }
        }
        else if (startDate.after(endDate))
        {
            weekdays = getWeekdays(endDate, startDate);
        }
        else
        {
            Calendar calendar = Calendar.getInstance();

            calendar.setTime(startDate);
            Date d = startDate;
            while (endDate.equals(d) || endDate.after(d))
            {
                if (isWeekday(d))
                {
                    weekdays.add(d);
                }

                calendar.add(Calendar.DATE, 1);
                d = calendar.getTime();

            }
        }

        return weekdays;
    }

    public static boolean isWeekday(Date d)
    {
        if (d == null)
            return false;

        Calendar calendar = Calendar.getInstance();
        calendar.setTime(d);
        int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);

        return ((dayOfWeek >= Calendar.MONDAY) && (dayOfWeek <= Calendar.FRIDAY));
    }
}

Answer 2

I don't know if this is an issue with your code, but JDK uses some unexpected values for Calendar constants. For example, months star with zero. In other words, Calendar.JANUARY is 0. On the other hand, weekdays are 1 to 7, starting with Sunday as 1. etc.

Answer 3

startCal.set(Calendar.DAY_OF_WEEK, i); Will flip flip your date back every 7 loops.

Answer 4

I luckily don't know much about Date in Java, but I know it's basically a difficult and bad API. Go for JodaTime until the new JSR-310 is done.