在 atm 项目中实现异常答案

【问题标题】：Implementing exceptions into atm project在 atm 项目中实现异常
【发布时间】：2013-11-21 01:36:57
【问题描述】：

我有一项任务是创建一个小型银行程序，该程序有两个账户，普通账户和储蓄账户。然而，当我即将完成一个粗略的版本时，我读到提示我应该使用我们在生病那天学到的东西，例外。

我并不清楚如何使用异常或是否应该创建自己的异常类。我想要一个例外，以便在程序中的任何时候，如果输入以“q”或“Q”开头的内容，程序就会退出并结束。另一个规定是，如果储蓄低于 25 美元，则冻结账户。我想异常对于该功能来说是理想的。

public abstract class BankAccount {

    int balance;
    int deposits;
    int withdrawals;
    int annualInterestRate;
    int charges;

    public void _BankAccount(int newBalance, int newInterest) {
        balance = newBalance;
        annualInterestRate = newInterest;
    }

    public void Deposit(int newDeposit) {
        balance = balance + newDeposit;
        deposits++;
    }

    public void Withdraw(int newWithdraw) {
        balance = balance - newWithdraw;
        withdrawals++;
    }

    public void calcInterest() {
        int monthlyInterestRate = (annualInterestRate / 12);
        int monthlyInterest = balance * monthlyInterestRate;
        balance = balance + monthlyInterest;
    }

    public void monthlyProcess() {
        balance = balance - charges;
        calcInterest();
        deposits = 0;
        withdrawals = 0;
    }
}

public class SavingsAccount extends BankAccount {

    boolean status;

    public void savingWithdraw(int newWithdraw) {
        if (balance < 25) {
            System.out.println("Error – Not enough funds.");
        } else {
            Withdraw(newWithdraw);
        }
    }

    public void savingDeposit(int newDeposit) {
        if (balance < 25) {
            Deposit(newDeposit);
            System.out.println("Savings account is now active.");
        } else {
            Deposit(newDeposit);
        }
    }

    public void savingMonthlyProcess() {
        if (withdrawals > 4) {
            charges = ((withdrawals - 4) * 1);
            balance = balance - ((withdrawals - 4) * 1);
            if (balance < 25) {
                System.out.println("Savings account is now inactive.");
            }
        }
    }
}

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    String choice;
    int num = 0;
    boolean quit = false;
    do {
        System.out.println("Which account would you like to access, regular or savings?:");
        choice = in.nextLine();
        if (choice.equals("regular")) {
            num = 0;
        }
        if (choice.equals("savings")) {
            num = 1;
        }
        switch (num) {
            case 0:
                System.out.println("What action do you wish to perform \n(Withdraw, deposit, monthly processing)?:");
                choice = in.nextLine();
                if (choice.equals("withdraw")) {
                    num = 0;
                }
                if (choice.equals("deposit")) {
                    num = 1;
                }
                if (choice.equals("monthly processing")) {
                    num = 2;
                }
                switch (num) {
                    case 0:
                        System.out.println("Enter amount to withdraw:");
                        Withdraw(in.nextInt());
                    case 1:
                        System.out.println("Enter amount to withdraw:");
                        Deposit(in.nextInt());
                    case 2:
                        MonthlyProcess();
                }
            case 1:
                System.out.println("What action do you wish to perform \n(Withdraw, deposit, monthly processing)?:");
                choice = in.nextLine();
                if (choice.equals("withdraw")) {
                    num = 0;
                }
                if (choice.equals("deposit")) {
                    num = 1;
                }
                if (choice.equals("monthly processing")) {
                    num = 2;
                }
                switch (num) {
                    case 0:
                        System.out.println("Enter amount to withdraw:");
                        savingsWithdraw(in.nextInt());
                    case 1:
                        System.out.println("Enter amount to withdraw:");
                        savingsDeposit(in.nextInt());
                    case 2:
                        savingMonthlyProcess();
                }

        }
    }


}

}

【问题讨论】：

" I want an exception so that at any point in the program if something that starts with 'q' or 'Q' is entered the program quits and end." -- 我不确定我是否会为此行为使用例外。相反，如果用户在需要数字的地方输入非数字输入，或者如果用户尝试提取的金额超过帐户持有的金额，我会使用异常。
异常通常保留给不规则的、非标准的行为。如果推送Q 是退出程序的预期方法，则不应通过异常处理。您应该处理诸如输入$34aby53 作为存款金额等的例外情况。或者将负值发送到Deposit 和Withdraw 方法，因为-$25 存款应该是$25 取款等。
您需要先将 break; 添加到您的 switch - case 语句中。继续。

标签： java exception bank

【解决方案1】：

异常用于处理不需要的情况。在您的情况下，您可以使用内置的异常类来处理大多数运行时异常，但使用自定义消息。

另一个规定是，如果储蓄低于 25 美元，则冻结帐户。

对于上述情况，您可以很好地创建一个新的异常类并使用用户定义的错误消息来处理此异常。

您可以在Exception handling in java阅读更多信息。

【讨论】：