java-字符串日期判断有效性

String birthday="20110230";
SimpleDateFormat dateFormat=new SimpleDateFormat("yyyyMMdd");
		try {
			Date date = dateFormat.parse(birthday);
			String newDateStr= dateFormat.format(date);
			
			if(!birthday.equalsIgnoreCase(newDateStr))
			System.out.println(false);
			else 
				System.out.println(true);
		} catch (ParseException e) {
			e.printStackTrace();
		}