public class CheckingAccount extends BankAccount
 { 
     private int transactionCount;

     public CheckingAccount() {
	 super(); // unnötig
	 transactionCount = 0;
     }
     public CheckingAccount(double initialBalance) {
	 super(initialBalance);
	 transactionCount = 0;
     }
     public void deposit(double amount) {
	 super.deposit(amount);
	 transactionCount++;
     }
     public void withdraw(double amount) {
	 super.withdraw(amount);
	 transactionCount++;
     } 	
    public String toString() {
	return "CheckingAccount[b = "
	    + getBalance() 
	    + ", t = " + transactionCount
	    + "]";
    }
}