一个构造方法的问题

import static java.lang.System.*;
public class Date {
        private int day,month,year;
        Date(int i,int j,int k){
            day=i;month=j;year=k;
        }
        Date(){
            day=28;month=2;year=2000;
        }
        Date(Date d){
            day=d.day;month=d.month;year=d.year;
        }
        public void printdate(){out.println(day+"/"+month+"/"+year);}
        public Date tomorrow(){
            Date d=new Date(this);
            d.day++;
            if(d.day>d.daysInMonth()){
                d.day=1;
                d.month++;
                if(d.month>12){
                    d.month=1;
                    d.year++;
                    }
                }return d;
        }
        public int daysInMonth(){
            switch(month){
            case 1:case 3:case 5:case 7:case 8:case 10:case 12:return 31;
            case 4:case 6:case 9:case 11:return 30;
            default:if(year%100!=0&&year%4==0){
                return 29;
            }
            else return 28;
            }
        }
        
        
    public static void main(String[] args) {
        Date d1=new Date();
        out.print("the current date is(dd/mm/yy):");
        d1.printdate();
        out.println();
        out.print("its tomorrow is (dd/mm/yy):");
        d1.tomorrow().printdate();
        out.println();
        
        Date d2=new Date(28,2,1964);
        out.print("the current date is (dd/mm/yy):");
        d2.printdate();
        out.println();
        out.print("its tomorrow is (dd/mm/yy):");
        d2.tomorrow().printdate();
        out.println();


    }
}