//  取某月的天数,strMonth的格式是"yyyy.MM" 
public static int getDaysInAMonth(String strMonth) {
  String[] arr=strMonth.split("[.]");

  // Create a calendar object of the desired month
  Calendar cal = new GregorianCalendar(Integer.parseInt(arr[0]),Integer.parseInt(arr[1])-1, 1);

  // Get the number of days in that month
  int days = cal.getActualMaximum(Calendar.DAY_OF_MONTH);

  return days;
 }

//  某月第一天是周几,strMonth的格式是"yyyy.MM"
 public static int getWeekOfFirstDay(String strMonth){
  String[] arr=strMonth.split("[.]");
  
  Calendar xmas = new GregorianCalendar(Integer.parseInt(arr[0]),Integer.parseInt(arr[1])-1, 1);
     int dayOfWeek = xmas.get(Calendar.DAY_OF_WEEK)-1;   
     return dayOfWeek;
 }