JAVA　新しいコンストラクタの設定

前提・実現したいこと

ここに質問の内容を詳しく書いてください。
（例）PHP(CakePHP)で●●なシステムを作っています。
■■な機能を実装中に以下のエラーメッセージが発生しました。

MyDate クラスに，文字列を１つだけ受け取るコンストラクタを新たに作成し，MyDate md = new MyDate("1974/2/3"); とすればMyDate型のインスタンスが生成されるようにしたいです。コンストラクタへの引数の形式は，yyyy/mm/dd (yyyy/m/d などでも可) とします。

該当のソースコード

JAVA
ソースコード
class MyName {
String firstName;
String lastName;

MyName(String name) {
    String[] list = name.split(" ", 2);
    firstName = list[0];
    lastName = list[1];
}

MyName(String firstName, String lastName) {
    this.firstName = firstName;
    this.lastName  = lastName;
}

public String toString(){
    return lastName + " " + firstName;
}

}

class MyDate {
int year;
int month;
int day;

MyDate(int y, int m, int d) {
    this.year  = y;
    this.month = m;
    this.day  = d;
}

}

class Person {
MyName name;
MyDate birthday;
String phoneNumber;
Person[] friends;

Person(String name, MyDate birthday, String phone) {
    this.name        = new MyName(name);
    this.birthday    = birthday;
    this.phoneNumber = phone;
}

Person(String name, int year, int month, int day, String phone) {
    this.name        = new MyName(name);
    this.birthday    = new MyDate(year, month, day);
    this.phoneNumber = phone;
}

Person(MyName name, int year, int month, int day, String phone) {
    this.name        = name;
    this.birthday    = new MyDate(year, month, day);
    this.phoneNumber = phone;
}

Person(MyName name, MyDate birthday, String phone) {
    this.name        = name;
    this.birthday    = birthday;
    this.phoneNumber = phone;
}

public String toString(){
    int i;
    String str;
    str = "NAME: " 
         + name 
         +" (Date of Birth: "
         + this.birthday.year 
         + "/" 
         + this.birthday.month
         + "/" 
         + this.birthday.day 
         + ")\n"
         + "  Number of friends = " 
         + this.friends.length 
         + "\n";
    
    for( i = 0; i < this.friends.length; i ++ ) {
        str = str 
            + "    Name of friend " 
            + i
            + ": " 
            + this.friends[i].name 
            + " (Date of Birth: " + this.friends[i].birthday.year
            + "/" + this.friends[i].birthday.month
            + "/" + this.friends[i].birthday.day
            + ")\n"; 
    }
    return str;
}

}

class Ex6_3 {
public static void main(String args[]) {
// create objects
Person person1 = new Person("Taro Tokyo" , 1985, 9, 20, "080-1234-5678");
Person person2 = new Person(new MyName("Jiro", "Osaka") , 1981, 6, 18, "090-8765-4321");
Person person3 = new Person(new MyName("Saburo Aichi"), new MyDate(1981, 12, 23), "090-3333-5555");
Person person4 = new Person(new MyName("Shiro Gifu"), new MyDate(1974, 2, 3), "090-2222-1111");

    // register friends of each person
    // Taro's friends
    Person[] person1Friends = new Person[2]; 
    person1Friends[0] = person2; // Jiro
    person1Friends[1] = person3; // Saburo

    // Jiro's friends
    Person[] person2Friends = new Person[3]; 
    person2Friends[0] = person1; // Taro
    person2Friends[1] = person3; // Saburo
    person2Friends[2] = person4; //Shiro

    // Saburo's friends
    Person[] person3Friends = new Person[1]; 
    person3Friends[0] = person4; // Shiro

    // Shiro's friends
    Person[] person4Friends = new Person[2]; 
    person4Friends[0] = person2; // Jiro
    person4Friends[1] = person3; // Saburo
    
    // set values to each objects
    person1.friends = person1Friends;
    person2.friends = person2Friends;
    person3.friends = person3Friends;
    person4.friends = person4Friends;

    // print each person's data
    System.out.print(person1);
    System.out.print(person2);
    System.out.print(person3);
    System.out.print(person4);
}

}