(1)String类型转换成日期(Date类型)
SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM-dd");
java.util.Date date = myFormatter.parse(sj1);
java.util.Date mydate = myFormatter.parse(sj2);
http://www.cnblogs.com/boonya/archive/2011/08/03/2126695.html
http://www.cnblogs.com/wxxian001/archive/2011/09/06/2168859.html