Java

// Ví dụ cấu trúc cấp độ động vật Java
public interface Playable {
    void play();
}

public interface Comparable {
    int compareTo(Object other);
}

public abstract class Animal implements Comparable {
    protected String name;
    private int age;

    public Animal(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public abstract void makeSound();

    public String getInfo() {
        return name + " là " + age + " tuổi";
    }

    public int compareTo(Object other) {
        Animal a = (Animal) other;
        return this.name.compareTo(a.name);
    }
}

public class Dog extends Animal implements Playable {
    private String breed;
    static String species = "Chó";

    public Dog(String name, int age, String breed) {
        super(name, age);
        this.breed = breed;
    }

    public void makeSound() {
        System.out.println("Gâu gâu!");
    }

    public void play() {
        System.out.println(name + " đang chơi bắt bóng");
    }
}

public class Cat extends Animal {
    private String furColor;

    public Cat(String name, int age, String furColor) {
        super(name, age);
        this.furColor = furColor;
    }

    public void makeSound() {
        System.out.println("Meo meo!");
    }
}

public interface PaymentProcessor {
    boolean processPayment(double amount);
}

public abstract class Order {
    private String orderId;
    protected double totalAmount;

    public Order(String orderId, double totalAmount) {
        this.orderId = orderId;
        this.totalAmount = totalAmount;
    }

    public abstract void fulfill();
}

public class CreditCardOrder extends Order implements PaymentProcessor {
    private String cardNumber;

    public CreditCardOrder(String orderId, double totalAmount, String cardNumber) {
        super(orderId, totalAmount);
        this.cardNumber = cardNumber;
    }

    public boolean processPayment(double amount) {
        return true;
    }

    public void fulfill() {
        System.out.println("Đơn hàng " + orderId + " đã được xử lý qua Thẻ tín dụng.");
    }
}

public interface UserRepository {
    User findById(String id);
    void save(User user);
}

public class User {
    private String id;
    private String username;
    private String email;

    public User(String id, String username, String email) {
        this.id = id;
        this.username = username;
        this.email = email;
    }

    public String getUsername() {
        return username;
    }
}

public class UserServiceImpl implements UserRepository {
    public User findById(String id) {
        return new User(id, "johndoe", "[email protected]");
    }

    public void save(User user) {
        System.out.println("Đang lưu người dùng: " + user.getUsername());
    }
}