创建银行卡类，并设计银行卡的两个子类：储蓄卡和信用卡。

创建银行卡类是一个基础的面向对象编程示例，可以用于模拟金融领域中的卡片服务。下面是一个简单的银行卡类以及其两个子类储蓄卡和信用卡的设计：

// 银行卡类
public class BankAccount {
    private String accountNumber;
    private String holderName;
    private double balance;

    // 构造函数、getter和setter省略

    // 操作方法，如存款、取款等
    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    public void withdraw(double amount) {
        if (amount <= balance) {
            balance -= amount;
        } else {
            System.out.println("余额不足");
        }
    }
}

// 存储卡子类 - 储蓄卡
public class SavingsCard extends BankAccount {
    public SavingsCard(String accountNumber, String holderName) {
        super(accountNumber, holderName);
    }

    // 特有的储蓄卡功能，比如利息计算
    public double calculateInterest(double annualRate, int months) {
        double interest = balance * (annualRate / 12) * months;
        return interest;
    }
}

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

    public CreditCard(String accountNumber, String holderName, int creditLimit) {
        super(accountNumber, holderName);
        this.creditLimit = creditLimit;
        this.isOverlimit = false;
    }

    // 透支处理
    public void charge(double amount) {
        if (balance + amount <= creditLimit) {
            withdraw(amount);
        } else {
            isOverlimit = true;
            System.out.println("已达到信用额度!");
        }
    }

    // 查看是否超限
    public boolean isOverCreditLimit() {
        return isOverlimit;
    }
}