java Date获取月份两位 java获取月份差

try {
                    String endData = taxStudentList.get(o).getMadEmployee().getHiredDate().substring(0,7);
                    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM");
                    Calendar ca=Calendar.getInstance();
                    ca.setTime(sdf.parse(endData)); //入职日期
                    Calendar ca1=Calendar.getInstance();
                    ca1.setTime(sdf.parse(salTypeVO.getYear() + "-" + salTypeVO.getMo()));  //当前发放工资的日期
                    int y=ca.get(ca.YEAR);
                    int y1=ca1.get(ca1.YEAR);
                    int mon=ca.get(ca.MONTH);
                    int mon1=ca1.get(ca1.MONTH);
                    if(mon < mon1) {
                        int depart = Math.abs(y - y1) * 12 + Math.abs(mon - mon1);//相差的总月份
                        salTypeVO.setMo(depart);
                    }else{
                        int depart = Math.abs(y - y1) * 12 - Math.abs(mon - mon1);
                        salTypeVO.setMo(depart);
                    }
                    p.setTaxThr(taxThr .multiply(new BigDecimal(salTypeVO.getMo())));
                } catch (ParseException e) {
                    e.printStackTrace();
                }