良いコード／悪いコードで学ぶ設計入門を読み終えたらリファクタリングする予定のコード

Main.java

import java.util.Random;

public class Main{
    /**
     * あるお店にかけられた問い合わせ電話の応対をシミュレートするコード
     * 
     * 客からの電話にまず店員が出て質問内容を聞いて答える。
     * もし自分では答えられない内容だったら店長に取り次ぐ。
     * 
     * しかし、店長が忙しくて電話に出られない時は、
     * 客の電話番号を聞いて折り返すと伝えて終了する。
     * @param args
     */
    public static void main(String[] args){
        // 顧客、店員、店長のインスタンスを作る
        Customer customer = new Customer(
            new Name("Charley"),
            new TelephoneNumber("00-1234-5678"),
            new Inquiry()
        );
        Staff staff = new Staff(new Name("Alice"));
        Manager manager = new Manager(new Name("Bob"));

        // 電話がかかってきた
        Telephone phone = new Telephone(customer, staff);

        phone.callOn();
        phone.call(phone.staff.askNameOf(phone.caller));
        phone.call(phone.staff.askInquiryAbout(phone.caller));
        if (phone.staff.canAnswer(phone.caller.inquiry)) {
            phone.call(phone.staff.answer(phone.caller.inquiry));
        } else if (!manager.isBusy()) {
            phone = phone.takenOverReceiver(manager);
            phone.call(phone.manager.helloProtocol());
            phone.call(phone.manager.answer(phone.caller.inquiry));
        } else {
            phone.call(phone.staff.askTelephoneNumber(phone.caller));
        }
        phone.callOff();
        return;
    }
}

class Name {
    final String name;

    Name(final String name) {
        if (name == null) {
            throw new IllegalArgumentException("名前を指定してください。");
        }
        this.name = name;
    }
}

class TelephoneNumber {
    final String number;

    TelephoneNumber(final String number) {
        if (!number.matches("^[0-9]{2,3}-[0-9]{4}-[0-9]{4}$")) {
            throw new IllegalArgumentException("電話番号が正しくありません");
        }

        this.number = number;
    }
}

class Inquiry {
    final int number;
    private static final String INQUIRY_A = "閉店時間";
    private static final String INQUIRY_B = "お店の場所";
    private static final String INQUIRY_C = "予約できるコース";

    Inquiry() {
        Random randomObject = new Random();
        this.number = randomObject.nextInt(3);
    }

    // 問い合わせ内容を答えるメソッド
    String detail() {
        switch(this.number) {
            case 0:
                return this.INQUIRY_A;
            case 1:
                return this.INQUIRY_B;
            case 2:
                return this.INQUIRY_C;
        }
        throw new IllegalArgumentException("問い合わせ内容が存在しません。");
    }
}

class Telephone {
    final Customer caller;
    final People receiver;
    Staff staff;
    Manager manager;

    Telephone(final Customer caller, People receiver) {
        if (caller == null || receiver == null) {
            throw new IllegalArgumentException("架電者と受電者を設定してください。");
        }
        this.caller = caller;
        this.receiver = receiver;
        if (receiver instanceof Staff) {
            this.staff = new Staff(receiver.name);
        } else if (receiver instanceof Manager) {
            this.manager = new Manager(receiver.name);
        } else {
            throw new IllegalArgumentException("受電者はStaffかManagerにしてください。");
        }
    }

    Telephone takenOverReceiver(final People receiver) {
        return new Telephone(this.caller, receiver);
    }

    void call(final String conversations) {
        System.out.print(conversations);
        return;
    }

    void callOn() {
        this.call(this.caller.helloProtocol());
        this.call(this.receiver.helloProtocol());
        return;
    }

    void callOff() {
        this.call(this.caller.byeProtocol());
        this.call(this.receiver.byeProtocol());
        System.out.println("ガチャン（電話を切る音）");
        return;
    }
}

class People {
    final Name name;

    People(final Name name) {
        this.name = name;
    }

    String helloProtocol() {
        return this.myName() + " : もしもし？\n";
    }

    String byeProtocol() {
        return this.myName() + " : それでは失礼します。\n";
    }

    String myName() {
        return this.name.name;
    }
}

class Customer extends People {
    final TelephoneNumber telephoneNumber;
    final Inquiry inquiry;

    Customer(
        final Name name,
        final TelephoneNumber telephoneNumber,
        final Inquiry inquiry
    ) {
        super(name);
        this.telephoneNumber = telephoneNumber;
        this.inquiry = inquiry;
    }

    String answerName() {
        return this.myName() + " : " + this.myName() + "です。\n";
    }

    String answerTelephoneNumber() {
        return this.myName() + " : " + this.telephoneNumber.number + "です。\n";
    }

    String askingInquiry() {
        return this.myName() + " : " + this.inquiry.detail() + "を伺いたいです。\n";
    }

    String byeProtocol() {
        return this.myName() + " : ありがとうございます。それでは失礼します。\n";
    }
}

class Staff extends People {
    private static final String ANSWER_A = "21時です。";
    private static final String ANSWER_B = "駅の東口のすぐ前です。";

    Staff(final Name name) {
        super(name);
    }

    String helloProtocol() {
        return this.myName() + " : もしもし、都会の隠れ家亭です。\n";
    }

    String askNameOf(final Customer caller) {
        String talking;
        talking = this.myName() + " : お名前をお伺いしてもよろしいでしょうか？\n";
        talking += caller.answerName();
        return talking;
    }

    String askInquiryAbout(final Customer caller) {
        String talking;
        talking = this.myName() + " : ご用件をお聞かせください。\n";
        talking += caller.askingInquiry();
        return talking;
    }

    String askTelephoneNumber(final Customer caller) {
        String talking;
        talking = this.myName() + " : 調べて後ほど折り返しますので、お電話番号をお聞かせください。\n";
        talking += caller.answerTelephoneNumber();
        return talking;
    }

    Boolean canAnswer(final Inquiry inquiry) {
        return(inquiry.number == 0 || inquiry.number == 1);
    }

    String answer(final Inquiry inquiry) {
        String talking;
        talking = this.myName() + " : ";

        if (inquiry.number == 0) {
            talking += ANSWER_A + "\n";
        } else if (inquiry.number == 1) {
            talking += ANSWER_B + "\n";
        } else {
            talking += "わかりません。\n";
        }
        return talking;
    }
}

class Manager extends People {
    private static final String ANSWER_A = "21時です。";
    private static final String ANSWER_B = "駅の東口のすぐ前です。";
    private static final String ANSWER_C = "春のフレンチディナーが予約できます。";

    Manager(final Name name) {
        super(name);
    }

    Boolean isBusy() {
        Random randomObject = new Random();

        return randomObject.nextBoolean();
    }

    String helloProtocol() {
        return this.myName() + " : もしもし、お電話変わりました。\n";
    }

    String answer(final Inquiry inquiry) {
        String talking;
        talking = this.myName() + " : ";

        if (inquiry.number == 0) {
            talking += ANSWER_A + "\n";
        } else if (inquiry.number == 1) {
            talking += ANSWER_B + "\n";
        } else if (inquiry.number == 2) {
            talking += ANSWER_C + "\n";
        } else {
            talking += "わかりません。\n";
        }
        return talking;
    }
}