创建银行卡类，设计两个子类：储蓄卡（取钱)和信用卡(取钱和借钱)。JAVA

在Java中，我们可以创建一个名为BankAccount的抽象基类，然后派生出两个具体的子类：SavingsAccount和CreditCard。这里是一个简单的例子：

// 定义一个抽象银行账户类
public abstract class BankAccount {
    protected String accountNumber;
    protected double balance;

    public BankAccount(String accountNumber, double initialBalance) {
        this.accountNumber = accountNumber;
        this.balance = initialBalance;
    }

    // 公共方法：获取余额和转账操作
    public double getBalance() {
        return balance;
    }

    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    public abstract void withdraw(double amount);
}

// 存款账户（储蓄卡）子类
public class SavingsAccount extends BankAccount {
    @Override
    public void withdraw(double amount) {
        if (amount <= balance) {
            balance -= amount;
        } else {
            System.out.println("取款金额超过可用余额");
        }
    }
}

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

    public CreditCard(String accountNumber, double initialBalance, int creditLimit) {
        super(accountNumber, initialBalance);
        this.creditLimit = creditLimit;
    }

    @Override
    public void withdraw(double amount) {
        if (amount <= balance && amount <= creditLimit) {
            balance -= amount;
        } else if (amount > creditLimit) {
            System.out.println("取款金额超过了信用额度");
        } else {
            System.out.println("取款金额超过当前可用余额");
        }
    }

    // 这里可以添加借款功能
    public void borrow(double amount) {
        if (balance + amount <= creditLimit) {
            balance += amount;
        } else {
            System.out.println("借款超出了信用额度");
        }
    }
}