JAVA&Android: 如何显示比当前DATE时间,提前一个月的时间

private String getFrontDate()

{

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

String mDate = "2012-09-12";

Calendar cal = Calendar.getInstance();

Date date = null;

try

{

date = sdf.parse(mDate);

}

catch (ParseException e)

{

e.printStackTrace();

}

cal.setTime(date);

cal.add(Calendar.MONTH, -1);

Date fDate = cal.getTime();

mFDate = sdf.format(fDate);

return mFDate;

}