public class SavingAccount extends Account {?private double interestRate;?public SavingAccount(double init_balance,double interest_rate) {??super(init_balance);??interestRate=interest_rate;?}?@Override//withdraw()是一個(gè)抽象方法?public boolean withdraw(double amount) {??if(amount<=balance){balance-=amount;return true;}??else return false;?}}