java获得指定日期的前一天，后一天的代码

/**
* 获得指定日期的前一天
* @param specifiedday
* @return
* @throws exception
*/
public static string getspecifieddaybefore(string specifiedday){
//simpledateformat simpledateformat = new simpledateformat("yyyy-mm-dd");
calendar c = calendar.getinstance();
date date=null;
try {
date = new simpledateformat("yy-mm-dd").parse(specifiedday);
} catch (parseexception e) {
e.printstacktrace();
}
c.settime(date);
int day=c.get(calendar.date);
c.set(calendar.date,day-1);

string daybefore=new simpledateformat("yyyy-mm-dd").format(c.gettime());
return daybefore;
}
/**
* 获得指定日期的后一天
* @param specifiedday
* @return
*/
public static string getspecifieddayafter(string specifiedday){
calendar c = calendar.getinstance();
date date=null;
try {
date = new simpledateformat("yy-mm-dd").parse(specifiedday);
} catch (parseexception e) {
e.printstacktrace();
}
c.settime(date);
int day=c.get(calendar.date);
c.set(calendar.date,day+1);

string dayafter=new simpledateformat("yyyy-mm-dd").format(c.gettime());
return dayafter;
}