一个具有多态特性的银行系统程序,允许用户从帐户中存钱、取钱.功能：计算账户应得的利息，然后把利息加到帐户余额上。账户交易完之后收取费用。打印帐户余额。帐户余额不足时抛出一个异常-A program of the banking system of the multi-state characteristics, allows users to save money from the account, withdraw money. Functions: calculation of the interest of the account, and then add the interest on the account balance. Account after the completion of the transaction fee. Print the account balance. Throw an exception when the account balance is less