2)定义钱类，包括元角分信息，提供构造方法、钱加减方法、钱翻倍方法、钱比较大小的方法、格式化显示钱的方法。

在Java中，我们可以创建一个名为`Money`的类来表示金额，包含元（yuan）、角（jiao）和分（fen）的信息。这个类可以有以下几个关键方法：

1. **构造方法**（Constructor）:

public class Money {
    private int yuan;
    private int jiao;
    private int fen;

    // 构造函数接受整数作为元、角、分的值
    public Money(int yuan, int jiao, int fen) {
        this.yuan = yuan;
        this.jiao = jiao;
        this.fen = fen;
    }
}

2. **加减方法** (`add`, `subtract`):

public Money add(Money other) {
    Money result = new Money(this.yuan + other.yuan, this.jiao + other.jiao, this.fen + other.fen);
    return result;
}

public Money subtract(Money other) {
    Money result = new Money(this.yuan - other.yuan, Math.min(this.jiao - other.jiao, 99), this.fen - other.fen);
    // 确保结果的角不超过99
    return result;
}

3. **翻倍方法** (`doubleAmount`):

public Money doubleAmount() {
    return new Money(this.yuan * 2, this.jiao * 2, this.fen * 2);
}

4. **比较大小方法** (`compareTo` 或 `equals`):

@Override
public int compareTo(Money other) {
    int totalComparison = Integer.compare(this.getTotalValue(), other.getTotalValue());
    if (totalComparison == 0) return 0; // 如果相等则返回0
    return totalComparison > 0 ? 1 : -1;
}

@Override
public boolean equals(Object obj) {
    if (this == obj) return true;
    if (obj == null || getClass() != obj.getClass()) return false;
    Money money = (Money) obj;
    return yuan == money.yuan && jiao == money.jiao && fen == money.fen;
}

5. **格式化显示方法** (`toString`):

@Override
public String toString() {
    return yuan + "元" + jiao + "角" + fen + "分";
}