java创建银行卡类，并且设计银行卡的两个子类储蓄卡和信用卡

在Java中，我们可以首先创建一个名为`BankAccount`的基类，它代表所有类型的银行卡。然后，可以创建两个子类`SavingsCard`和`CreditCard`来体现具体的储蓄卡和信用卡特性。这里是一个简单的例子：

// 银行卡基类
public abstract class BankAccount {
    private String accountNumber;
    private String holderName;
    private double balance;

    // 构造函数
    public BankAccount(String accountNumber, String holderName) {
        this.accountNumber = accountNumber;
        this.holderName = holderName;
        this.balance = 0.0;
    }

    // 抽象方法，用于存款和取款操作
    public abstract void deposit(double amount);
    public abstract void withdraw(double amount);

    // 公共方法获取信息
    public String getAccountNumber() { return accountNumber; }
    public String getHolderName() { return holderName; }
    public double getBalance() { return balance; }
}

// 储蓄卡子类
public class SavingsCard extends BankAccount {
    // 存储额外的信息，如利息率
    private double interestRate;

    public SavingsCard(String accountNumber, String holderName, double initialBalance) {
        super(accountNumber, holderName, initialBalance);
        this.interestRate = 0.05; // 例如年利率为5%
    }

    @Override
    public void deposit(double amount) {
        super.deposit(amount);
        balance += amount * interestRate; // 计算并更新余额
    }

    @Override
    public void withdraw(double amount) {
        if (amount <= balance) {
            super.withdraw(amount);
            balance -= amount;
        } else {
            System.out.println("Insufficient funds.");
        }
    }
}

// 信用卡子类
public class CreditCard extends BankAccount {
    private int creditLimit;
    private boolean isOverLimit;

    public CreditCard(String accountNumber, String holderName, double initialBalance, int limit) {
        super(accountNumber, holderName, initialBalance);
        creditLimit = limit;
        isOverLimit = false;
    }

    @Override
    public void deposit(double amount) {
        if (amount > 0) {
            super.deposit(amount);
            if (getBalance() + amount > creditLimit) {
                isOverLimit = true;
            }
        }
    }

    @Override
    public void withdraw(double amount) {
        if (!isOverLimit && amount <= getBalance()) {
            super.withdraw(amount);
        } else {
            System.out.println("Withdrawal denied due to credit limit or insufficient funds.");
        }
    }
}

// 示例用法
public static void main(String[] args) {
    SavingsCard savings = new SavingsCard("123456", "Alice", 1000.0);
    savings.deposit(500.0);
    System.out.println(savings.getBalance());

    CreditCard credit = new CreditCard("789012", "Bob", 5000.0, 6000.0);
    credit.withdraw(2000.0);
    System.out.println(credit.isOverLimit());
}