关于日期，String和Date的一些整理

通过日期来知道当天是星期几,及日期，String转为Date

public class Once{ 
     public final static String dayNames[] = { 
         "星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"};

     public static String dateToDay(String date) throws ParseException
     {
    	 Calendar calendar = Calendar.getInstance(); 
    	 calendar.setTime(new SimpleDateFormat("yyyy-MM-dd").parse(date));
    	 int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK); 
    	 String day=dayNames[dayOfWeek - 1]; 	 
    	 return day;
     }
     public static void main(String[] args) throws ParseException {
    	String day= Once.dateToDay("2009-04-01");
    	System.out.println("这一天是："+day);
    	
    	Calendar calendar = Calendar.getInstance(); 
    	Calendar calendar2 = Calendar.getInstance(); 
    	Date newit=new SimpleDateFormat("yyyy-MM-dd").parse("2009-04-01");
    	Date newit2=new SimpleDateFormat("yyyy-MM-dd").parse("2009-04-02");
    	calendar.setTime(newit);
    	calendar2.setTime(newit2);
    	System.out.println("比大小："+(calendar2.getTimeInMillis()-calendar.getTimeInMillis()>0));
    	
    	
	}
}