public class CalendarBook {

    public static void main(String[] args) throws ParseException {
        CalendarBook cb = new CalendarBook();
        cb.printWeekTitle();
        cb.printCalendar(2015,8);
    }

    public void printCalendar(int year,int month) throws ParseException{
        String monthStr;  //格式化月份，因為要轉成yyyyMMdd格式的
 

        if(month<10){
            monthStr = "0"+month;
        } else{
            monthStr = month+""; //數字跟字串拼接轉成字串格式
        }
        String yearMonthStr = year+monthStr;
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
        Calendar calendarEnd = Calendar.getInstance();
        Calendar calendarStart = Calendar.getInstance();
        //根據年份和月份得到輸入月份有多少天
 

        int monthDays = getMonthLastDay(year, month);  
        //月初的date字串
        String dateStartStr = yearMonthStr+"01";    
        //月末的date字串
        String dateEndStr = yearMonthStr+monthDays;  
        Date startDate = sdf.parse(dateStartStr);
        Date endDate = sdf.parse(dateEndStr);
        calendarStart.setTime(startDate);
        calendarEnd.setTime(endDate);
        //得到輸入月份有多少周
 

        int weeks = calendarEnd.get(Calendar.WEEK_OF_MONTH);  
        //得到當月第一天是星期幾，這裡週日為第一天，從1開始，週一則為2
        int dayOfWeek = calendarStart.get(Calendar.DAY_OF_WEEK);  
        int day = 1;
        //當月的第一週做特殊處理，單獨列印一行
        for(int i=1;i<=7;i++){
            if(i>=dayOfWeek){
                System.out.print(" "+day+"  ");
                day++;
            } else{
                System.out.print("    ");
            }
        }
        System.out.println();
        //開始列印從第二週開始的日期
        for(int week=1;week<weeks;week++){
            for(int i=1;i<=7;i++){
                if(day>monthDays){
                    break;
                }
                if(day<10){
                    System.out.print(" "+day+"  ");
                } else{
                    System.out.print(day+"  ");
                }
                day++;
            }
            System.out.println();
        }
    }


    public int getMonthLastDay(int year,int month){
        int monthDay;
        int[][] day = {{0,31,28,31,30,31,30,31,31,30,31,30,31},
                        {0,31,29,31,30,31,30,31,31,30,31,30,31}};
        if(year%4==0 && year%100!=0 || year%400==0){
            //閏年
            monthDay = day[1][month];
        } else{
            monthDay = day[0][month];
        }
        return monthDay;
    }
    public void printWeekTitle(){ 
        System.out.println("日"+"     "+"一"+"     "+"二"+"    "+"三"+"    "+"四"+"     "+"五"+"     "+"六");
    }
}

執行結果截圖（執行效果，字型大小5號最佳）：