为什么编译器会在构造函数调用中引发错误？

Question

我收到此错误:

Fraction类中的构造函数分数不能应用于给定类型

我认为问题在于最后一种方法multiply.我正在尝试返回一个新的对象分数实例,其中分子字段乘以参数.

public class Fraction {   
    private int numerator; 
    private int denominator;    
    public Fraction() {
        numerator = 0; 
        denominator = 1;
    }

    public void setNumerator(int newNum) {
        numerator = newNum;
    }

    public void setDenominator(int newDenom) {
        denominator = newDenom;
    }

    public int getNumerator() {
        return numerator;
    }

    public int getDenominator() {                           
        return denominator;
    }

    public double getValue() {
        return (double) numerator/denominator;
    }

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

    public Fraction multiply(int num) {
        return new Fraction(numerator, denominator);
    }
}

Answer 1

new Fraction(numerator, denominator)- 你Fraction的构造函数不带参数;public Fraction()

如果您需要此功能,则需要实现它

public Fraction() 
{
    this(0, 1);
}

public Fraction(int numerator, int denominator) 
{
    this.numerator = numerator; 
    this.denominator = denominator;
}

举个例子