import java.text.SimpleDateFormat; import java.util.Date; public class A { public static void main(String[] args) { System.out.println(new SimpleDateFormat("yyyy-MM-dd").format(new Date())); // OK System.out.println(new SimpleDateFormat("YYYY-ww").format(new Date())); // OK System.out.println(new SimpleDateFormat("YYYY-MM-dd").format(new Date())); // BAD } }