인터페이스와 추상클래스

// 인터페이스
interface Payable {
    void pay(int amount);
    default String getType() { return "UNKNOWN"; }  // default 메서드
}

// 추상 클래스
abstract class Account {
    protected String owner;
    public Account(String owner) { this.owner = owner; }
    public abstract int getBalance();
    public void printInfo() {
        System.out.println(owner + ": " + getBalance() + "원");
    }
}

class BankAccount extends Account implements Payable {
    private int balance;

    public BankAccount(String owner, int balance) {
        super(owner);
        this.balance = balance;
    }

    @Override
    public int getBalance() { return balance; }

    @Override
    public void pay(int amount) {
        balance -= amount;
        System.out.println(amount + "원 결제 완료. 잔액: " + balance);
    }

    @Override
    public String getType() { return "BANK"; }
}