java根据开始时间结束时间计算中间间隔日期

DateFormat FORMATTER = new SimpleDateFormat("yyyy-MM-dd");
        List<SatisticsByCustomer> list=null;
        try{
            String beginTime="2013-01-01";
            String endTime="2013-01-21";
            Calendar startDay = Calendar.getInstance();
            Calendar endDay = Calendar.getInstance();
            startDay.setTime(FORMATTER.parse(beginTime));
            endDay.setTime(FORMATTER.parse(endTime));
            // 给出的日期开始日比终了日大则不执行打印
            list=new ArrayList<SatisticsByCustomer>();
            SatisticsByCustomer s1=new SatisticsByCustomer();
            s1.setColumnName(beginTime);
            list.add(s1);
            if(!beginTime.equals(endTime)){
                if(startDay.compareTo(endDay)<=0){
                    //现在打印中的日期
                    Calendar currentPrintDay = startDay;
                    while (true){
                        SatisticsByCustomer s=new SatisticsByCustomer();
                        // 日期加一
                        currentPrintDay.add(Calendar.DATE, 1);
                        // 日期加一后判断是否达到终了日，达到则终止打印
                        if (currentPrintDay.compareTo(endDay) == 0) {
                            break;
                        }
                        s.setColumnName(FORMATTER.format(currentPrintDay.getTime()));
                        list.add(s);
                    }
                    SatisticsByCustomer s2=new SatisticsByCustomer();
                    s2.setColumnName(endTime);
                    list.add(s2);
                }
            }
            for (SatisticsByCustomer customer : list)
            {
                System.out.println(customer.getColumnName());
            }
        }catch (Exception e){
            e.printStackTrace();
        }