从Java

Question

从方法返回的数组包含不需要的值。我不知道为什么。

这是DriverExam类：

public class DriverExam 
{

    private char[] answer = {'B','D','A','A','C','A','B','A','C','D',
                             'B','C','D','A','D','C','C','B','D','A'};
    private char[] stuAnswer = new char[20];
    private int totalCorrect = 0;
    private int[] missed = new int[20];

    public DriverExam(char stuAnswer[])
    {
        for (int i = 0; i < stuAnswer.length; i++)
        {
            this.stuAnswer[i] = stuAnswer[i];
        }
    }

    public int gettotalCorrect()
    {
        int k = 0;
        for (int i = 0; i < stuAnswer.length; i++)
        {
            if (stuAnswer[i] == answer[i])
                totalCorrect++;
        }
        return totalCorrect;
    }

    public int gettotalIncorrect()
    {
        return 20-totalCorrect;
    }

    public int[] getMissed()
    {
        int k = 0;
        for (int i = 0; i < stuAnswer.length; i++)
        {
            if (stuAnswer[i] != answer[i])
            {
                missed[k] = i;
                k++;
            }
        }
        return missed;
    }
}

这是主程序：

import java.util.Scanner;
public class Main6 
{
    public static void main(String[] args) 
    {
        char[] answer = new char[20];
        int[] missed2;
        String str;
        Scanner keyboard = new Scanner(System.in);

        for (int i = 1; i <= 20; i++)
        {
            System.out.println("Enter the answer for question #"+i);
            str = keyboard.nextLine();

            while (Character.toUpperCase(str.charAt(0)) != 'A' 
                    && Character.toUpperCase(str.charAt(0)) != 'B'
                    && Character.toUpperCase(str.charAt(0)) != 'C'
                    && Character.toUpperCase(str.charAt(0)) != 'D')
            {
                System.out.println("Your input is invalid. Only accept A, B, C, or D");
                System.out.println("Enter the answer for question #"+i);
                str = keyboard.nextLine();
            }

            answer[i-1] = Character.toUpperCase(str.charAt(0));
        }

        DriverExam de = new DriverExam (answer);

        System.out.print("***FINAL RESULT:");
        System.out.print("\nTotal correct answers: "+de.gettotalCorrect());
        System.out.print("\nTotal incorrect answers: "+de.gettotalIncorrect());
        System.out.print("\nQuestions missed: ");

        missed2 = de.getMissed();
        for (int i = 0; i < missed.length; i++)
        {
            System.out.print(i+" ");
        }
    }
}

在DriverExam类中，我返回一个名为＆＃34;错过＆＃34;的数组。到主程序。在主程序中，我使用一个名为＆＃34; miss2＆＃34;存储返回的数组。但是当我打印结果时（我用＆＃34键入所有答案; A＆＃34;）。它如下所示：

  

最终结果：
  总答错：6
  总答错：14
  错过的问题：0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

错过结果的问题很奇怪且不正确。

Answer 1

你想要“错过”的是一个可变长度的结果。要使用数组执行此操作，您将需要一个表示结果结束的值。在这里，我使用了-1。

public int[] getMissed()
{
    int k = 0;
    for (int i = 0; i < stuAnswer.length; i++)
    {
        if (stuAnswer[i] != answer[i])
        {
            missed[k] = i;
            k++;
        }
    }
    if(k < missed.length)
    {
      missed[k] = -1
    }
    return missed;
}

然后，在for循环中，检查结束值。奇怪的值可能是由于未在数组中明确设置它们而导致的默认int值。

    for (int i = 0; i < missed2.length && missed2[i] != -1; i++)
    {
        System.out.print(i+" ");
    }