java - 我使用 BigInteger 创建了 Rational 类，但没有显示任何内容

Question

import java.math.*;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int T = sc.nextInt();

        for (int t = 0; t < T; t++) {
            Rational r1 = new Rational(new BigInteger(sc.next()), new BigInteger(sc.next()));
            Rational r2 = new Rational(new BigInteger(sc.next()), new BigInteger(sc.next()));

            System.out.println(r1 + " + " + r2 + " = " + r1.add(r2));
            System.out.println(r1 + " - " + r2 + " = " + r1.subtract(r2));
            System.out.println(r1 + " * " + r2 + " = " + r1.multiply(r2));
            System.out.println(r1 + " / " + r2 + " = " + r1.divide(r2));
        }
    }
}

class Rational extends Number implements Comparable<Rational> {
    private static final long serialVersionUID = 1L;
    private BigInteger numerator = BigInteger.ZERO;
    private BigInteger denominator = BigInteger.ONE;

    public Rational() {
        this(BigInteger.ZERO, BigInteger.ONE);
    }
    // set numerator and denominator
    public Rational(BigInteger numerator, BigInteger denominator) {
        BigInteger gcd = gcd(numerator, denominator);
        this.numerator = ((denominator.compareTo(BigInteger.ZERO) > 0) ? new BigInteger("1") : new BigInteger("-1"))
            .multiply(numerator.divide(gcd));
        this.denominator = denominator.abs().divide(gcd);
    }
    // Find GCD of two BigIntegers
    private static BigInteger gcd(BigInteger n, BigInteger d) {
        BigInteger n1 = n.abs();
        BigInteger n2 = d.abs();
        BigInteger gcd = BigInteger.ONE;

        for (BigInteger k = BigInteger.ONE; k.compareTo(n1) <= 0 && k.compareTo(n2) <= 0; k.add(BigInteger.ONE)) {
            if (n1.mod(k).equals(BigInteger.ZERO) && n2.mod(k).equals(BigInteger.ZERO))
                gcd = k;
        }
        return gcd;
    }

    public BigInteger getNumerator() {
        return numerator;
    }

    public BigInteger getDenominator() {
        return denominator;
    }

    public Rational add(Rational secondRational) {
        BigInteger n = (numerator.multiply(secondRational.getDenominator()))
            .add(denominator.multiply(secondRational.getNumerator()));
        BigInteger d = denominator.multiply(secondRational.getDenominator());
        return new Rational(n, d);
    }

    public Rational subtract(Rational secondRational) {
        BigInteger n = (numerator.multiply(secondRational.getDenominator()))
            .subtract(denominator.multiply(secondRational.getNumerator()));
        BigInteger d = denominator.multiply(secondRational.getDenominator());
        return new Rational(n, d);
    }

    public Rational multiply(Rational secondRational) {
        BigInteger n = numerator.multiply(secondRational.getNumerator());
        BigInteger d = denominator.multiply(secondRational.getDenominator());
        return new Rational(n, d);
    }

    public Rational divide(Rational secondRational) {
        BigInteger n = numerator.multiply(secondRational.getDenominator());
        BigInteger d = denominator.multiply(secondRational.numerator);
        return new Rational(n, d);
    }

    @Override
    public String toString() {
        if (denominator.compareTo(BigInteger.ONE) == 0)
            return numerator + "";
        else
            return numerator + "/" + denominator;
    }

    @Override
    public boolean equals(Object other) {
        if ((this.subtract((Rational) (other))).getNumerator().equals(BigInteger.ZERO))
            return true;
        else
            return false;
    }

    @Override
    public int intValue() {
        return (int) doubleValue();
    }

    @Override
    public float floatValue() {
        return (float) doubleValue();
    }

    @Override
    public double doubleValue() {
        double x = this.getNumerator().doubleValue();
        double y = this.getDenominator().doubleValue();
        return x / y;
    }

    @Override
    public long longValue() {
        return (long) doubleValue();
    }

    @Override
    public int compareTo(Rational o) {
        if (this.subtract(o).getNumerator().compareTo(BigInteger.ZERO) > 0)
            return 1;
        else if (this.subtract(o).getNumerator().compareTo(BigInteger.ZERO) < 0)
            return -1;
        else
            return 0;
    }
}

大家好，我是学java的。我尝试在 Rational 类中使用 BigInteger。上网查了很多地方的代码，还是不行。

如果我在控制台上写输入，程序不会显示任何内容并且不会终止。

我的代码有什么问题？我真的压力很大:(请帮助我!

Answer 1

BigInteger 是不可变的。您不能执行 k.add(BigInteger.ONE) 并期望 k 发生变化。您必须执行k = k.add(BigInteger.ONE)。

您可以在构造期间调用的 gcd 方法中执行此操作，因此第一次创建 Rational gcd 时会进入无限循环.