Question

I have two classes : Year and LeapYear setting the days of the year to 365 and 366 respectively within their constructors. I want to achieve something specific here.i want to override the Year’s constructor in the LeapYear’s constructor to set the number of days to 366? Alternatively i have done the following.

public class Year {

private int days;

public Year() {
    this.days = 365;
}
public void setDays(int days) {
    this.days = days;
}

public int getDays() {
    return this.days;
}

}

public class LeapYear extends Year {

public LeapYear() {
    setDays(366);
}

}

Answer 1

The model is wrong and that’s why you have trouble with the constructors: it’s simply not true that a 366-days-leap-year is-a 365-days-year. But that’s what you model tries to tell us.

You better model it like that:

public abstract class PeriodOfDays {
   int days;
   public PeriodOfDays(int days) { this.days = days; }
}

public class StandardYear extends PeriodOfDays {
   public StandardYear() { super(365); }
}

public class LeapYear extends PeriodOfDays {
   public LeapYear() { super(366); }
}