使用推理的Java方法

Question

我有一个有理类和一个主类。我的很多代码都是在rational类中完成的，然后我在main类中调用它。然而，一些理由并不像真实的数字那样打印出来。它们看起来是这样的：rational.Rational@7852e922.我不知道如何正确打印它们。此外，在我的add方法中添加了rationals之后，我无法弄清楚如何使用reduce方法。主类中代码的最后一行出现了一个错误。

public class Rational {
/**
 * @param args the command line arguments
 */
double num;
double den;
public Rational() {
    this.num = 0.0;
    this.den = 0.0;
}
public static void printRational(Rational r) {
    System.out.println(r.num + " / " + r.den);
}
public Rational(double num, double den) {
    this.num = num;
    this.den = den;
}
public static void negate(Rational r) {
    r.num = -r.num;
}
public static double invert(Rational r) {
    return Math.pow(r.num / r.den, -1);
}
public double toDouble() {
    return (double) num / den;
}
public static int gcd(int n, int d) {
    if (n < 0) {
        n = -n;
    }
    if (d < 0) {
        d = -d;
    }
    return n * (d / gcd (n, d));
}
public Rational reduce() {
    double g = num;
    double gcd = den;
    double tmp;
    if (g < gcd) {
        tmp = g;
        g = gcd;
        gcd = tmp;
    }
    while (g != 0) {
        tmp = g;
        g = gcd % g;
        gcd = tmp;
    }
    return new Rational(num / gcd, den / gcd);
}
public static Rational add(Rational a, Rational b) {
    double den = a.den * b.den;
    double num = a.num * b.num;
    return new Rational(num, den);
}
}

这是我的主课。

public class Main {
    public static void main(String[] args) {
        Rational x = new Rational();           
        x.num = 2.0;
        x.den = 3.0;
        System.out.println(x);
        System.out.println();
        Rational.negate(x);
        System.out.println(x);
        System.out.println();
        Rational y = new Rational(2.0, 3.0);
        System.out.println(Rational.invert(y));
        System.out.println();
        System.out.println(y.toDouble());
        System.out.println();
        Rational z = new Rational();
        Rational w = new Rational();
        z.num = 5.0;
        z.den = 3.0;
        w.num = 4.0;
        w.den = 3.0;
        Rational.add(z, w);
        System.out.println(Rational.add(z, w));
        System.out.println(Rational.reduce(z,w));
    }
}

Answer 1

您需要覆盖Rational中的toString()方法。

例如

public String toString() {
    return num + " / " + den;
}

Answer 2

将此方法添加到Rational类：

@Override
public String toString() {
    return printRational(this);
}

toString的默认实现将只提供类名及其哈希代码的十六进制字符串。