import java.text.Format;
import java.text.SimpleDateFormat;
import java.util.Calendar;
public class Test {
public static void main(String[] args) {
int day = 100;//改成你所需要的天数
Calendar c = Calendar.getInstance();
c.set(Calendar.DAY_OF_YEAR, day);
Format f = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(f.format(c.getTime()));
}
}