public class CheckingAccount extends BankAccount {
    private double fee;    // adding new state

    public CheckingAccount(String name, double fee) {
        super(name);       // call superclass c'tor
        this.fee = fee;
    }

    // adding new behavior
    public double getFee() {
        return fee;
    }

    // overriding existing behavior
    public void withdraw(double amount) {
        // balance -= (amount + fee);   // doesn't compile - private access
        super.withdraw(amount + fee);
    }
}