public class SavingsAccount extends BankAccount {
    protected double interestRate;
    // Konstruktor:
    public SavingsAccount(int id,double init,double rate){
        super(id, init); 
        interestRate = rate;
    }
    // zusaetzliche Objekt-Methode:
    public void addInterest() {
        balance = balance * (1 + interestRate);
        System.out.println(
            "Interest added to account: "+ account
            + "\nNew balance:\t" + balance);
    }
} // end of class SavingsAccount