得到昨天时间

import java.util.*;
import java.text.*;
public class Time
{
public static void main(String [] args) throws java.io.IOException
{
Calendar cal = Calendar.getInstance();
cal.add(Calendar.DATE,-1);
java.util.Date da = cal.getTime();

String yesterday = new SimpleDateFormat("yyyy-MM-dd:hh-mm-ss").format(da);
         //年－月－日：时－分－秒
System.out.println (yesterday);

}
}