java正则表达式 验证时间(yyyy-MM-dd)合法性

/**
	 * 验证开始和结束时间，格式必须为yyyy-MM-dd或者yyyy/MM/dd，且开始时间要小于结束时间
	 */
	public boolean validate(String start , String end){
		//这个正则匹配的是日期格式为:yyyy/MM/dd或者yyyy-MM-dd
		String rexp = "^(((\\d{2}(([02468][048])|([13579][26]))[\\-]((((0?[13578])|(1[02]))[\\-]((0?[1-9])|([1-2][0-9])|(3[01])))|(((0?[469])|(11))[\\-]((0?[1-9])|([1-2][0-9])|(30)))|(0?2[\\-]((0?[1-9])|([1-2][0-9])))))|(\\d{2}(([02468][1235679])|([13579][01345789]))[\\-]((((0?[13578])|(1[02]))[\\-]((0?[1-9])|([1-2][0-9])|(3[01])))|(((0?[469])|(11))[\\-]((0?[1-9])|([1-2][0-9])|(30)))|(0?2[\\-]((0?[1-9])|(1[0-9])|(2[0-8]))))))|"
				+ "((\\d{2}(([02468][048])|([13579][26]))[\\/]((((0?[13578])|(1[02]))[\\/]((0?[1-9])|([1-2][0-9])|(3[01])))|(((0?[469])|(11))[\\/]((0?[1-9])|([1-2][0-9])|(30)))|(0?2[\\/]((0?[1-9])|([1-2][0-9])))))|(\\d{2}(([02468][1235679])|([13579][01345789]))[\\/]((((0?[13578])|(1[02]))[\\/]((0?[1-9])|([1-2][0-9])|(3[01])))|(((0?[469])|(11))[\\/]((0?[1-9])|([1-2][0-9])|(30)))|(0?2[\\/]((0?[1-9])|(1[0-9])|(2[0-8])))))))";
		Pattern p = Pattern.compile(rexp);
		Matcher startM = p.matcher(start);
		Matcher endM = p.matcher(end);
		
		if(startM.matches() == false || endM.matches() == false){
			return false;
			
		}else{
			String sfh = start.charAt(4)+"";
			String efh = end.charAt(4)+"";
			String[] startTime = start.split(sfh);
			String[] endTime = end.split(efh);
			
			Calendar startC = Calendar.getInstance();
			startC.set(Integer.parseInt(startTime[0]), Integer.parseInt(startTime[1]), Integer.parseInt(startTime[2]));
			
			Calendar endC = Calendar.getInstance();
			endC.set(Integer.parseInt(endTime[0]), Integer.parseInt(endTime[1]), Integer.parseInt(endTime[2]));
			
			boolean b = startC.before(endC);
			if(b){
				return true;
			}else{
				return false;
			}
		}
	}