遍历日期范围的Java，奇怪的结果

Question

I want to iterate through date ranges without using libraries (ie Joda). I wrote that simple code but got strange results. For example, for dates 2010-01-01 2010-02-01 it prints:

1.0.2010
2.0.2010
3.0.2010
4.0.2010
5.0.2010
6.0.2010
7.0.2010
8.0.2010
9.0.2010
10.0.2010
11.0.2010
12.0.2010
13.0.2010
14.0.2010
15.0.2010
16.0.2010
17.0.2010
18.0.2010
19.0.2010
20.0.2010
21.0.2010
22.0.2010
23.0.2010
24.0.2010
25.0.2010
26.0.2010
27.0.2010
28.0.2010
29.0.2010
30.0.2010
31.0.2010
1.1.2010

the problem exists also for dates: 2010-05-01 2010-06-01 (prints april instead of may). Any help?

import java.util.Calendar;
import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.text.DateFormatSymbols;
import java.util.Locale;
import java.util.Map;
import java.util.HashMap;
import javax.swing.JOptionPane;
import java.util.GregorianCalendar;

class test
{
    public static void main(String[] args) {

        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
        Date startDate = null, endDate = null;

        try 
        {
            startDate = dateFormat.parse("2010-01-01"); // or 2010-05-01
            endDate = dateFormat.parse("2010-02-01"); // or 2010-06-01
        } 
        catch (ParseException pe) 
        {
            System.exit(-1);
        }

        Calendar start = Calendar.getInstance();
        start.setTime(startDate);
        Calendar end = Calendar.getInstance();
        end.setTime(endDate);

        for (Date date = start.getTime(); !start.after(end); start.add(Calendar.DATE, 1), date = start.getTime()) 
        {
            Calendar cal = Calendar.getInstance();
            cal.setTime(date);
            int year = cal.get(Calendar.YEAR);
            int month = cal.get(Calendar.MONTH);
            int day = cal.get(Calendar.DAY_OF_MONTH);
            int dow = cal.get(Calendar.DAY_OF_WEEK);  
            System.out.printf("%d.%d.%d\n", day, month, year);
        }
    }
}

Answer 1

Month that the library return start at 0 .. 11

Also your loop could be simplified liked this. Note that this might not be the best solution.

while(!start.after(end)) 
{
    int year = start.get(Calendar.YEAR);
    int month = start.get(Calendar.MONTH) + 1;
    int day = start.get(Calendar.DAY_OF_MONTH);
    System.out.printf("%d.%d.%d\n", day, month, year);        
    start.add(Calendar.DATE, 1);
}