3.创建××数据结构及其基本操作。 与创建用户数据结构类似，根据系统的功能定义，创建其他类型的数据结构，例如，校园卡数据结构 Card类、卡交易数据结构 Transaction类等等，请自行设计完成。使用java进行编程

创建数据结构和基本操作通常是面向对象编程中的关键步骤，这里以Java为例，来创建两个简单的数据结构：`Card`类（代表校园卡）和`Transaction`类（代表卡交易）。我们将包括一些基本属性和方法。

首先，我们定义`Card`类：

public class Card {
    private String cardNumber;
    private String holderName;
    private double balance;

    // 构造函数
    public Card(String cardNumber, String holderName) {
        this.cardNumber = cardNumber;
        this.holderName = holderName;
        this.balance = 0;
    }

    // 基本属性获取和设置
    public String getCardNumber() { return cardNumber; }
    public void setCardNumber(String cardNumber) { this.cardNumber = cardNumber; }
    public String getHolderName() { return holderName; }
    public void setHolderName(String holderName) { this.holderName = holderName; }
    public double getBalance() { return balance; }
    public void deposit(double amount) { balance += amount; }
    public void withdraw(double amount) { if (amount <= balance) { balance -= amount; } else { System.out.println("Insufficient balance"); } }
}

接下来，我们定义`Transaction`类：

public class Transaction {
    private Card card;
    private double amount;
    private Date timestamp;

    // 构造函数
    public Transaction(Card card, double amount, Date timestamp) {
        this.card = card;
        this.amount = amount;
        this.timestamp = timestamp;
    }

    // 属性获取和setter
    public Card getCard() { return card; }
    public void setCard(Card card) { this.card = card; }
    public double getAmount() { return amount; }
    public void setAmount(double amount) { this.amount = amount; }
    public Date getTimestamp() { return timestamp; }
    public void setTimestamp(Date timestamp) { this.timestamp = timestamp; }

    // 交易方法
    public void execute() {
        card.withdraw(amount);
        System.out.println("Transaction of " + amount + " completed at " + timestamp);
    }
}