这段程序系统时间怎么取不出来
import java.util.Calendar;
import java.util.GregorianCalendar;


public class TimeDemo {
private Calendar calendar = new GregorianCalendar();
public String getDate()
{
StringBuffer buf= new StringBuffer();
buf.append(calendar.get(Calendar.YEAR)).append("-");
buf.append(calendar.get(Calendar.MONTH)).append("-");
buf.append(calendar.get(Calendar.DAY_OF_MONTH));
return calendar.toString();
}

public static void main(String[] args) {
System.out.println(new TimeDemo().getDate());
}
}

[解决办法]

 return calendar.toString();

 return buf.toString();