如何根据用户输入创建对应账户对象以避免重复编写业务方法？

完全可以实现，核心是利用Java多态特性抽离重复逻辑，不需要为两类账户单独编写相同的业务代码，具体优化步骤如下：

步骤1：调整Bank类的成员变量与方法参数 #

移除Bank类中写死的DepositAccount account成员变量，将账户实例改为方法入参传入，同时增加文件名后缀参数区分不同账户的存储文件。另外原来作为成员变量的交易列表transactionsToAdd会导致多调用场景下的数据污染，改成方法内局部变量更合理。

步骤2：合并重复的账户管理方法 #

将两套几乎完全一致的账户管理逻辑合并为一个通用方法，根据传入的后缀动态生成文件名，根据传入的账户实例执行对应逻辑：

public class Bank {
    ScannerClass scanner = new ScannerClass();
    DateManager dateManager = new DateManager();
    Writer writer = new Writer();
    Reader reader = new Reader();

    // 通用账户管理方法
    public void ManageAccount(String name, BankAccount account, String fileSuffix) {
        // 每次调用初始化独立的交易列表，避免数据互相干扰
        List<Transaction> transactionsToAdd = new ArrayList<Transaction>();
        try {
            // 动态生成文件名
            String baseFileName = name + fileSuffix;
            File myObj = new File(baseFileName + ".txt");

            if (myObj.createNewFile()) {
                File myTransactionObj = new File(baseFileName + "Transactions.txt");
                myTransactionObj.createNewFile();
                writer.SingleLineWriter(baseFileName, "0");
            } else {
                account.setName(name);
                String line = reader.SingleLineRead(baseFileName);
                double balance = Double.parseDouble(line);
                // 把账户实例、基础文件名、交易列表传入后续业务方法
                double newBalance = ManageBank(balance, account, baseFileName, transactionsToAdd);
                writer.BalanceAppender(newBalance, baseFileName);
            }
        } catch (IOException e) {
            System.out.println("发生错误");
            e.printStackTrace();
        }
    }

    // 调整ManageBank的入参，接收外部传入的账户、文件名和交易列表
    public double ManageBank(double balance, BankAccount account, String baseFileName, List<Transaction> transactionsToAdd) throws IOException {
        boolean quit = false;
        List<String> transactions = reader.readPreviousTransactions(baseFileName);
        do {
            int userChoice = scanner.InitialChoiceScanner();
            switch (userChoice) {
                case 1:
                    double amount = scanner.DepositScanner();
                    balance = account.Deposit(balance, amount);
                    System.out.print("你的新余额为：" + balance);
                    String depositFullDate = dateManager.getDateAsString();
                    Transaction depositTransaction = new Transaction("存款", amount, depositFullDate);
                    transactionsToAdd.add(depositTransaction);
                    break;
                case 2:
                    double withdrawAmount = scanner.WithdrawScanner();
                    if (withdrawAmount > balance) {
                        System.out.println("抱歉，余额不足");
                        break;
                    }
                    balance = account.Withdraw(balance, withdrawAmount);
                    System.out.print("你的新余额为：" + balance);
                    String withdrawFullDate = dateManager.getDateAsString();
                    Transaction withdrawTransaction = new Transaction("取款", withdrawAmount, withdrawFullDate);
                    transactionsToAdd.add(withdrawTransaction);
                    break;
                case 3:
                    System.out.print("你的当前余额为：" + balance);
                    break;
                case 4:
                    writer.displayStatement(baseFileName);
                    break;
                case 0:
                    quit = true;
                    break;
                default:
                    System.out.println("请选择有效选项");
                    break;
            }
            System.out.println();
        } while (!quit);

        List<Transaction> parsedTransactions = writer.parseStringToTransaction(transactions);
        for (Transaction transaction : parsedTransactions) {
            transactionsToAdd.add(transaction);
        }
        writer.transactionWriter(transactionsToAdd, baseFileName);
        System.out.println("感谢使用银行服务！");
        return balance;
    }
}

步骤3：按账户类型调用通用方法 #

用户选择账户类型后，创建对应实例传入通用方法即可，不需要再单独编写两套业务逻辑：

// 调用存款账户管理
Bank bank = new Bank();
BankAccount depositAccount = new DepositAccount();
bank.ManageAccount("张三", depositAccount, "");

// 调用储蓄账户管理
BankAccount savingsAccount = new SavingsAccount();
bank.ManageAccount("张三", savingsAccount, "-Savings");

后续扩展建议 #

如果后续两类账户需要新增差异化逻辑，直接在对应的SavingsAccount或DepositAccount类中重写Deposit、Withdraw等方法即可，上层的通用管理逻辑不需要修改，符合面向对象的开闭原则。

内容的提问来源于stack exchange，提问作者Connor Gill