时间段转换

//201908,201910,201911,201912,202001,202004,202006,202007,202011,202012变成201908,201910-202001,202004,202006-202007,202011-202012
    public static String stringToString(String s){
        SimpleDateFormat format = new SimpleDateFormat("yyyyMM");
        String[] split = s.split(",");
        Date date=new Date();
        String newString="";
        boolean flag=false;
        for(int p=0;p<split.length;p++) {
            try {
                if(p!=0){
                    Calendar bef = Calendar.getInstance();
                    Calendar aft = Calendar.getInstance();
                    Date date2 =format.parse(split[p]);
                    bef.setTime(date);
                    aft.setTime(date2);
                    int result = aft.get(Calendar.MONTH) - bef.get(Calendar.MONTH);
                    int month = (aft.get(Calendar.YEAR) - bef.get(Calendar.YEAR)) * 12;
                    if((Math.abs(month + result)!=1)){
                        if(p!=1 && flag== true){
                            newString=newString+"-"+format.format(date);
                        }
                        newString=newString+","+split[p];
                        flag=false;
                    }else {
                        flag=true;
                        if(p==split.length-1&&flag==true){
                            newString=newString+"-"+split[p];
                        }
                    }
                    date=date2;
                }else{
                    date = format.parse(split[p]);
                    newString=newString+split[p];
                }
            } catch (ParseException e) {
                e.printStackTrace();
            }
        }
        return newString;
    }