Java Interface Validator Tutorial

AgeUserValidator.java

public class AgeUserValidator implements UserValidator {
    @Override
    public void validate(User user) {
        if(user.age <= 0 || user.age > 99) {
            System.out.println("에러: 올바른 나이를 입력해주세요.");
        }
    }
}

Main.java

import java.util.Scanner;

public class Main {

    final static UserValidator[] userValidator = {new NameUserValidator(), new AgeUserValidator()};

    public static void main(String[] args) {
        User user = new User();
        System.out.print("## 이름 :");
        user.name = new Scanner(System.in).next();
        System.out.print("## 나이 :");
        user.age = new Scanner(System.in).nextInt();

        for (int i = 0; i < userValidator.length; i++) {
            userValidator[i].validate(user);
        }
    }
}

NameUserValidator.java

public class NameUserValidator implements UserValidator {
    @Override
    public void validate(User user) {
        if(user.name == null || user.name.isEmpty()) {
            System.out.println("에러: 이름을 입력해주세요.");
        }
    }
}

User.java

public class User {
    public String name;
    public int age;
}

UserValidator.java

public interface UserValidator {
    void validate(User user);
}