java日期操作

1.比较两个日期大小

public static String compareDate(String s1,String s2){

        java.text.DateFormat df = new java.text.SimpleDateFormat("yyyy-MM-dd");
        java.util.Calendar c1 = java.util.Calendar.getInstance();
        java.util.Calendar c2 = java.util.Calendar.getInstance();

        try{
            c1.setTime(df.parse(s1));
            c2.setTime(df.parse(s2));
        }catch(java.text.ParseException e){
            e.printStackTrace();
        }

        int result = c1.compareTo(c2);

        if(result == 0){
            return "S1 = S2";
        }else if (result < 0){
            return "S1 < S2";
        }else{
            return "S1 > S2";
        }
    }