Lecture 10
20
Bank and BankAccount cooperate
•public int deposit(int amount)
•{
•    this.incrementBalance( amount);
•    this.countTransaction();
•    return amount ;
•}
•public void incrementBalance(int amount)
•{
•    balance += amount;
•    this.getIssuingBank().         incrementBalance( amount );
•}
this BankAccount asks the Bank it is in to update its own balance field