Java写出一段测试代码 在准备类Fraction时，创建一个类nul1denominatoreexception，它必须是一个检查异常，如果类Fraction的对象的分母为0，则抛出其实例。将Fraction类的各种方法完整呈现出来

下面是一个例子，展示了如何在 Fraction 类中使用 NullDenominatorException：

public class NullDenominatorException extends Exception {
    public NullDenominatorException(String message) {
        super(message);
    }
}


public class Fraction {
    private int numerator;
    private int denominator;

    public Fraction(int numerator, int denominator) throws NullDenominatorException {
        if (denominator == 0) {
            throw new NullDenominatorException("分母不能为0");
        }
        this.numerator = numerator;
        this.denominator = denominator;
    }

    public String toString() {
        return numerator + "/" + denominator;
    }

    public Fraction add(Fraction other) throws NullDenominatorException {
        int newNumerator = numerator * other.denominator + other.numerator * denominator;
        int newDenominator = denominator * other.denominator;
        return new Fraction(newNumerator, newDenominator);
    }

    public Fraction subtract(Fraction other) throws NullDenominatorException {
        int newNumerator = numerator * other.denominator - other.numerator * denominator;
        int newDenominator = denominator * other.denominator;
        return new Fraction(newNumerator, newDenominator);
    }

    public Fraction multiply(Fraction other) throws NullDenominatorException {
        int newNumerator = numerator * other.numerator;
        int newDenominator = denominator * other.denominator;
        return new Fraction(newNumerator, newDenominator);
    }

    public Fraction divide(Fraction other) throws NullDenominatorException {
        int newNumerator = numerator * other.denominator;
        int newDenominator = denominator * other.numerator;
        return new Fraction(newNumerator, newDenominator);
    }

    public void simplify() {
        int gcd = _gcd(numerator, denominator);
        numerator /= gcd;
        denominator /= gcd;
    }

    private static int _gcd(int a, int b) {
        if (b == 0) {
            return a;
        }
        return _gcd(b, a % b);
    }
}

下面是一段测试代码：

try {
    // 创建一个分母为0的分数
    Fraction f = new Fraction(1, 0);
    System.out.println("分数为：" + f);
} catch (NullDenominatorException e) {
    System.out.println("发生异常：" + e.getMessage());
}

// 创建两个分数
Fraction f1 = new Fraction(1, 2);
Fraction f2 = new Fraction(3, 4);

// 进行加法运算
Fraction f3 = f1.add(f2);
System.out.println(f1 + " + " + f2 + " = " + f3);

// 进行减法运算
Fraction f4 = f1.subtract(f2);
System.out.println(f1 + " - " + f2 + " = " + f4);

// 进行乘法运算
Fraction f5 = f1.multiply(f2);
System.out.println(f1 + " * " + f2 + " = " + f5);

// 进行除法运算
Fraction f6 = f1.divide(f2);
System.out.println(f1 + " / " + f2 + " = " + f6);

// 简化分数
Fraction f7 = new Fraction(2, 4);
System.out.println("原分数：" + f7);
f7.simplify();
System.out.println("简化后的分数：" + f7);

当分母为0时，运行上述代码会抛出 NullDenominatorException 异常。如果分母不为0，会进行加、减、乘、除、简化等运算，并输出结果。