获取当前calendar

Calendar cd = Calendar.getInstance();

//日加7天

cd.add(Calendar.DAY_OF_WEEK,7);

根据日期获取calendar

Calendar cd = Calendar.getInstance();

Date d = new Date();

cd.setTime(d);

cd.add(Calendar.DAY_OF_WEEK,7);

根据字符串获取

DateFormat  df = new SimpleDateFormat("yyyy-MM-dd");

Date d = Df.parse("2014-02-19");

Calendar cd = Calendar.getInstance();

Cd.setTime(d);

cd.add(Calendar.DAY_OF_WEEK,7);

日期加法

cd.add(Calendar.DAY_OF_WEEK,7);

日期减法

cd.add(Calendar.DAY_OF_WEEK,7);