Cfrgtkky

I have a class called Monster, every Monster has a name, dateofbirth, and a weapon. and The Monster constructor
should have the following signature:

Monster(String name, int day, int month, int year, String weaponName)

To create a monster the following code should work:

new Monster("Godzilla",11,10,2000,"VenomThrower")

So I create the datafield in Monster:

public String name;

public MyDate dateOfBirth;

public int day;

public int month;

public int year;

public Weapon weapon;

However, I have to use the MyDate class defined below to create a MyDate object for dateofbirth.
And use the Weapon class defined below to create a Weapon object for the monster’s weapon.

If I have to use the Object MyDate and Weapon, their type would be different from the constructor(int day, int month, int year) and (String weaponName), I try to cast the parameters, but it compiles error. Except casting, is there another way to achieve this?? Thank you.

public class MyDate {



    private int year;

    private int month;

    private int day;





    MyDate(int year, int month, int day) {

        this.year = year;

        this.month = month;

        this.day = day;

    }



    public int getYear() {

        return year;

    }



    public void setYear(int year) {

        this.year = year;

    }



    public int getMonth() {

        return month;

    }



    public void setMonth(int month) {

        this.month = month;

    }



    public int getDay() {

        return day;

    }



    public void setDay(int day) {

        this.day = day;

    }

}



public class Weapon {



    private String name;

    Weapon(String n) {

        this.name = n;

    }

    public String getName()   {

        return name;

    }

}

As you've seen, you can't just go and cast arbitrary variables to other classes. You could, however, call the respective constructors of MyDate and Weapon in Monster's constructor:

public class Monster {

    private String name;

    private MyDate dateOfBirth;

    private Weapon weapon;



    public Monster(String name, int day, int month, int year, String weaponName) {

       this.name = name;

       this.dateOfBirth = new MyDate(year, month, day);

       this.weapon = new Weapon(weaponName);

    }

}

I would go at it like this:

public class Monster{



    public String name;

    public MyDate dateOfBirth;

    public Weapon weapon;



    public Monster(String name, int day, int month, int year, String weaponName){

        this.name = name;

        this.dateOfBirth = new DateOfBirth(day, month, year);

        this.weapon = new Weapon(weaponName);

    }



    //second constructor for good measure

    public Monster(String name, DateOfBirth day, Weapon weapon){

        this.name = name;

        this.dateOfBirth = day;

        this.weapon = weapon;

    }



    //also relay all getters and setters to the underlying objects:

    public int getDay(){

        return dateOfBirth.getDay()

    }

    //...

}

You should definitely drop the redundant day, month and year, because they are stored in dayOfMonth.

You could either create another constructor to accept MyDate and Weapon objects:

public Monster(String name, MyDate birthDay, Weapon weapon) {

   //...

}

or in your constructor you could do:

public Monster(String name, int day, int month, int year, String weaponName){ 

    this.weapon = new Weapon(weaponName);

    this.dateOfBirth = new MyDate(day, month, year);

    //...

}

To create the appropriate objects from the given parameters

I'm not exactly clear on what you're asking. If you are indicating that you must retain the Monster constructor as you have defined it, but store MyDate and Weapon objects in your Monster class, then the answer is simple.

Monster(String name, int day, int month, int year, String weaponName) {

    this.name = name;

    this.dateOfBirth = new MyDate(year, month, day);

    this.weapon = new Weapon(weaponName);

}

I don't think this kind of coupling is a very good idea. Better to define your constructor like so:

Monster(String name, MyDate dateOfBirth, Weapon weapon) {

    this.name = name;

    this.dateOfBirth = dateOfBirth;

    this.weapon = weapon;

}

and call the constructor like this:

Monster m = new Monster("Godzilla", new MyDate(2000,11,10), new Weapon("VenomThrower"));

Also, You might want to have a look at using java.time.LocalDate to replace your MyDate class.

If you have a fixed set of Weapons. You could redefine Weapon as an enum rather than a class

public enum Weapon {

   VenomThrower, . . . ;

}

Then Weapon references will look like,

Weapon.VenomThrower