Calendar的使用举个小栗子：
//通过当前时间获取本周周一时间
Date date = new Date();
Calendar calendar = new GregorianCalendar();
calendar.setTime(date );
calendar.add(Calendar.DATE,i + 1 - (calendar.get(Calendar.DAY_OF_WEEK) - 1)
);
date = calendar.getTime();
原文：http://www.cnblogs.com/playa13/p/3738382.html