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我正在开发一个程序，用户输入两个不同的分数，然后计算机通过分数方法运行它们以测试它们是否相等。分配中的另一个步骤是抛出 IllegalArgumentException 以识别分母之一是否为 0，然后重新启动程序。Fraction 和 testFraction 类如下：

分数类：

class Fraction {

    private int numerator;
    private int denominator;

    Fraction() {
        numerator = 0;
        denominator = 1;

    }

    Fraction (int num, int den) {
        numerator = num;
        denominator = den;
        if (denominator == 0){
            throw new IllegalArgumentException (
            "Denominator cannot be zero");
        }
    }

    public void setNum(int num){
        numerator = num;
    }

    public void setDen(int den){
        denominator = den;

        }

    public int getNum(){
        return numerator;
    }

    public int getDen(){
        return denominator;
    }

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

    public boolean equals(Fraction other){
    if (numerator * other.getDen() == denominator * other.getNum()){
            return true;
         } 
        else {
            return false;
        }
    }
}

testFraction 类：

import java.util.Scanner;

public class testFraction {

public static void main(String[] args) {

    Scanner keyboard = new Scanner(System.in); 
    int a = 1;
    int b = 1;
    int c = 1;
    int d = 1;

    Fraction f1 = new Fraction(a, b);
    Fraction f2 = new Fraction(c, d);


    System.out.println("Enter the numerator of the first fraction: ");
    f1.setNum(keyboard.nextInt());

    System.out.println("Enter the denominator of the first fraction: ");
    f1.setDen(keyboard.nextInt());

    try{
        int fraction = a/b; 
    }
    catch (IllegalArgumentException e){
        System.out.println(e.getMessage);
        main(args);
    }

    System.out.println("\nEnter the numerator of the second fraction: ");
    f2.setNum(keyboard.nextInt());

    System.out.println("Enter the denominator of the second fraction: ");
    f2.setDen(keyboard.nextInt());

    System.out.println("\nFraction 1: " + f1);
    System.out.println("Fraction 2: " + f2);

    System.out.println("\nAre fractions equal? " + f1.equals(f2));

    System.out.println(("\nWould you like to run the counter with a different integer? \n(1 for YES - 0 for NO): "));
    int answer = keyboard.nextInt();

    if (answer == 1){
        System.out.println("\nLet's Rock 'n Roll! ");
        main(args);
    }

    else if (answer == 0){
        System.out.println("\nLater Dude! ");
        System.exit(0);
    }       
}
}

我觉得我在 try/catch 中工作不正确。谢谢你的帮助。

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1 回答 1

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您在初始化 Fraction 时抛出了 IllegalArgumentException，但是当您在 testFraction 中进行实际除法时尝试捕获它。永远不会到达您的捕获，因为初始化时的异常将阻止代码到达不正确的除法。相反，您应该将 try/catch 放在创建 Fractions 的代码周围。

此外，您使用模拟值初始化您的分数： 1. 这并不是真正有用，并且会带来一个问题：您的构造函数永远不会抛出它的 IllegalArgumentException，因为它是用正确的值调用的。您应该改为在 setDenominator 中引发 IllegalArgumentException，并从构造函数中调用它。

于 2015-10-22T12:28:30.403 回答