java 获取指定月份的前几个月

public String getStrDate(String strDate,int num ){

String stringDate="";

try {

SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM");//格式化为2017-10

Date month=formatter.parse(strDate);

Calendar calendar = Calendar.getInstance();//得到Calendar实例

calendar.setTime(month);

calendar.add(Calendar.MONTH, -num);//把月份减三个月

Date starDate = calendar.getTime();//得到时间赋给Data

stringDate = formatter.format(starDate).replace("-","");//使用格式化Data

return stringDate;

}catch (Exception e){

e.printStackTrace();

logger.error("获取时间报错：", e);

return stringDate;

}

}