java获得上一月

Date d1=new Date();
SimpleDateFormat yearFormat=new SimpleDateFormat("yyyy");
SimpleDateFormat monthFormat=new SimpleDateFormat("MM");
Calendar c = Calendar.getInstance();
c.setTime(d1);
c.add(c.MONTH, -1);//上一月
Date temp_date = c.getTime();
String year=yearFormat.format(temp_date);
String month=monthFormat.format(temp_date);