public class Account {
    private String accountNumber;
    private double balance;

    public Account(String accountNumber, double balance) {
        this.accountNumber = accountNumber;
        this.balance = balance;
    }

    public void withdraw(double amount) {
        if (amount < 0) {
            throw new IllegalArgumentException("Withdrawal amount cannot be negative.");
        }
        if (amount > balance) {
            throw new IllegalArgumentException("Insufficient funds.");
        }
        balance -= amount;
    }

    public double getBalance() {
        return balance;
    }
}