java 實現本月日曆

最終的效果:

 星期日 星期一 星期二 星期三 星期四 星期五 星期六
                                 1     2 
  3     4     5     6     7*     8     9 
 10    11     12   13     14     15    16 
 17    18     19   20     21     22    23 
 24    25     26   27     28     29    30 
 31 

public class Test {

    public static void main(String[] arg) {
        GregorianCalendar d = new GregorianCalendar();
        int today = d.get(Calendar.DAY_OF_MONTH);
        int month = d.get(Calendar.MONTH);

        d.set(Calendar.DAY_OF_MONTH, 1);
        int weekday = d.get(Calendar.DAY_OF_WEEK);

        int firstDayOfWeek = d.getFirstDayOfWeek();

        int indent = 0;
        while (weekday != firstDayOfWeek) {
            indent++;
            d.add(Calendar.DAY_OF_MONTH, -1);
            weekday = d.get(Calendar.DAY_OF_WEEK);
        }

        String[] weekdayNames = new DateFormatSymbols().getShortWeekdays();
        do {
            System.out.printf("%4s", weekdayNames[weekday]);
            d.add(Calendar.DAY_OF_MONTH, 1);
            weekday = d.get(Calendar.DAY_OF_WEEK);
        } while (weekday != firstDayOfWeek);

        System.out.println();

        for (int i = 0; i < indent; i++){
            System.out.print("    ");
        }    
        d.set(Calendar.DAY_OF_MONTH, 1);

        do {
            int day = d.get(Calendar.DAY_OF_MONTH);
            System.out.printf("%3d", day);

            if (day == today) {
                System.out.printf("*");
            } else {
                System.out.printf(" ");
            }
            d.add(Calendar.DAY_OF_MONTH, 1);
            weekday = d.get(Calendar.DAY_OF_WEEK);

            if (weekday == firstDayOfWeek) {
                System.out.println();
            }
        } while (month == d.get(Calendar.MONTH));

        if (weekday != firstDayOfWeek) {
            System.out.println();
        }
    }
}