问Java如何进行日历比较

EN

public static void main(String[] rags) throws ParseException{
    String total= "I am Going to join in scholl at 21/10/2108";
    String[] effectiveDateText=total.split(" ");
    String effectiveDate=effectiveDateText[effectiveDateText.length-1];
    System.out.println(effectiveDate);
    SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
    Calendar today = Calendar.getInstance();
    String todate=sdf.format(today.getTime());
    System.out.println(todate);
    if(effectiveDate<todate){
        System.out.println("effective date is less then the previous date");
    }