10. Create an enum of the least-valuable six types of paper currency. Loop through the values( ) and print each value and its ordinal( ).

首先，我们创建一个枚举（enum）类型，代表最不值钱的六种纸币类型。在Java中，枚举是一种特殊的类，它可以包含常量和方法。然后我们可以使用`values()`方法获取枚举的所有实例，并通过循环打印它们的名称和对应的序号（ordinal）。

public enum CurrencyValue {
    DOLLAR("$1", 0),
    QUARTER("$0.25", 1),
    NICKEL("$0.05", 2),
    PENNY("$0.01", 3),
    HALF_DOLLAR("$0.50", 4),
    ONE_CENT("1 cent", 5); // 尽管1 cent的实际价值非常小，但我们仍将其视为一种货币

    private final String denomination;
    private final int ordinal;

    CurrencyValue(String denomination, int ordinal) {
        this.denomination = denomination;
        this.ordinal = ordinal;
    }

    public String getDenomination() {
        return denomination;
    }

    public int getOrder() {
        return ordinal;
    }

    public static void printValues() {
        for (CurrencyValue currency : CurrencyValue.values()) {
            System.out.println("Value: " + currency.getDenomination() + ", Ordinal: " + currency.getOrder());
        }
    }
}

// 调用printValues()方法来显示所有枚举值
CurrencyValue.printValues();

当你运行这段代码，它会输出每种纸币类型及其对应的序号：

Value: $1, Ordinal: 0
Value: $0.25, Ordinal: 1
Value: $0.05, Ordinal: 2
Value: $0.01, Ordinal: 3
Value: $0.50, Ordinal: 4
Value: 1 cent, Ordinal: 5