Java中实现分数的四则运算

public class Fraction {
    private int numerator;//分子
    private int denominator;//分母
    public Fraction (){}
    public Fraction (int numerator,int denominator){
        this.numerator=numerator;
        this.denominator=denominator;
    }

    public int getDenominator() {
        return denominator;
    }

    public int getNumerator() {
        return numerator;
    }

    public void setDenominator(int denominator) {
        this.denominator = denominator;
    }

    public void setNumerator(int numerator) {
        this.numerator = numerator;
    }

        //约分
    public void reduction(Fraction fra){
        int num=fra.getNumerator();
        int den=fra.getDenominator();
        int i=0;
        do {
            i++;
            if (num%i==0 && den%i==0){
                num=num/i;
                den=den/