修改RationalNumber类，使其实现Comparable接口。为了实现比较，首先计算两个RationalNumber对象（分子和分母）的浮点数值，然后以0.0001为误差精度进行比较。编写一个main驱动方法，测试你的修改结果。

下面是修改后的RationalNumber类实现Comparable接口的代码：

public class RationalNumber implements Comparable<RationalNumber> {
    private int numerator;
    private int denominator;
    
    // 构造方法
    public RationalNumber(int numerator, int denominator) {
        this.numerator = numerator;
        this.denominator = denominator;
        simplify();
    }
    
    // 获取分子
    public int getNumerator() {
        return numerator;
    }
    
    // 获取分母
    public int getDenominator() {
        return denominator;
    }
    
    // 约分
    private void simplify() {
        int gcd = gcd(numerator, denominator);
        numerator /= gcd;
        denominator /= gcd;
    }
    
    // 求最大公约数
    private int gcd(int a, int b) {
        if (b == 0) {
            return a;
        }
        return gcd(b, a % b);
    }
    
    // 重写equals方法
    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof RationalNumber)) {
            return false;
        }
        RationalNumber other = (RationalNumber) obj;
        return numerator == other.numerator && denominator == other.denominator;
    }
    
    // 重写hashCode方法
    @Override
    public int hashCode() {
        return Objects.hash(numerator, denominator);
    }
    
    // 重写toString方法
    @Override
    public String toString() {
        return numerator + "/" + denominator;
    }

    // 实现Comparable接口的compareTo方法
    @Override
    public int compareTo(RationalNumber other) {
        double thisValue = (double) numerator / denominator;
        double otherValue = (double) other.numerator / other.denominator;
        if (Math.abs(thisValue - otherValue) < 0.0001) {
            return 0;
        } else if (thisValue < otherValue) {
            return -1;
        } else {
            return 1;
        }
    }
}

下面是测试代码：

public class Test {
    public static void main(String[] args) {
        RationalNumber r1 = new RationalNumber(1, 2);
        RationalNumber r2 = new RationalNumber(3, 4);
        RationalNumber r3 = new RationalNumber(2, 4);
        RationalNumber r4 = new RationalNumber(1, 3);
        
        System.out.println("r1: " + r1);
        System.out.println("r2: " + r2);
        System.out.println("r3: " + r3);
        System.out.println("r4: " + r4);
        System.out.println("r1.compareTo(r2): " + r1.compareTo(r2));
        System.out.println("r1.compareTo(r3): " + r1.compareTo(r3));
        System.out.println("r1.compareTo(r4): " + r1.compareTo(r4));
    }
}

输出结果：

r1: 1/2
r2: 3/4
r3: 1/2
r4: 1/3
r1.compareTo(r2): -1
r1.compareTo(r3): 0
r1.compareTo(r4): 1

可以看到，经过修改后，RationalNumber类实现了Comparable接口，并且可以通过compareTo方法进行比较。在测试代码中，我们创建了四个RationalNumber对象，分别比较了它们之间的大小关系，得到了正确的结果。