java 捕获数字类型的 NumberFormatException

Question

您好，我已经使用 Java 创建了一个测验应用程序，但我不确定如何实现这个小部分。它要求我:添加异常以在用户输入字符(即“a”)时捕获 NumericQuestion 类型的 NumberFormatException

我最初尝试在 presentQuestion 方法的开头插入一个 try catch block ，但它给我带来了很多错误。我在实现这些 try-catch 方法方面没有太多经验。我知道这可能很简单，所以任何帮助都将不胜感激。我的代码如下所示。

package QuestionGame;

import java.util.Scanner;

public class NumericQuestionTester {

    public static void main(String[] args) {
        boolean userCorrect;
        Scanner input = new Scanner(System.in);
        NumericQuestion quThree = new NumericQuestion("What is the answer to 5 divided by 3?", "1.67", 2, 0.03, 0.07);
        presentQuestion(input, quThree);
        input.close();

    }

    public static void presentQuestion(Scanner input, NumericQuestion q) {
        boolean userCorrect;
        q.displayQuestion();
        System.out.println("Enter your answer: ");
        String answer = input.nextLine();
        userCorrect = q.checkAnswer(answer);
        if (userCorrect){
            System.out.println("Correct! The answer is : " + q.getAnswer() + " and you have a score of : " + q.getMark());
        } else {
            System.out.println(answer + " is incorrect. You scored zero.");
        }
        System.out.println();
    }
}


package QuestionGame;

public class NumericQuestion extends Question {

    //instance variables
    private double ansNumeric;
    private double positiveRange;
    private double negativeRange;

    //constructor
    public NumericQuestion(String quText, String answer, int mark, double positiveRange, double negativeRange) {
        super(quText, answer, mark);
        this.ansNumeric = Double.parseDouble(answer);
        this.positiveRange = positiveRange;
        this.negativeRange = negativeRange;
    }

    //accessors & mutators
    public double getAnsNumeric() {
        return ansNumeric;
    }

    public void setAnsNumeric(double ansNumeric) {
        this.ansNumeric = ansNumeric;
    }

    //methods

    public boolean checkAnswer (String answer) {
        double answerDouble = Double.parseDouble(answer);
        if (answerDouble > (this.ansNumeric + this.positiveRange)) {
            return false;
        } else if (answerDouble < (this.ansNumeric - this.negativeRange)) {
            return false;
        } else {
            return true;
        }
    }

}

Answer 1

除了 exception 处理，我建议您添加持续检查，而用户不会输入预期的整数答案。

do{
     System.out.println("You Numeric answer, please")
     String answer = input.nextLine();
}while !answerIsNumeric(answer);
userCorrect = q.checkAnswer(answer);

public boolean answerIsNumeric(String answer){
     try{
         Double.parseDouble(answer);
     }catch(NumberFormatException e){
         return false;
     }
     return true;
}