java - 用Java查找2个数组中匹配元素的数量

我目前正在从教科书（而不是家庭作业，自学）中进行一项练习，该练习为多选题考试给出了正确答案，我将其命名为answerKey，要求用户输入学生的答案并找到匹配的元素计算成绩。请看我到目前为止所做的。我不明白numCount的行为，为什么它不能正确返回。我想对此提供指导。谢谢！

import java.util.Arrays;
import java.util.Scanner;

public class Drivers_License
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);

        int incorrect = 0;
        double grade = 0.0;
        String input;
        char[] answerKey = {'B', 'D', 'A', 'A', 'C',
                            'A', 'B', 'A', 'C', 'D',
                            'B', 'C', 'D', 'A', 'D',
                            'C', 'C', 'B', 'D', 'A'};
        System.out.println();

        int numCorrect = 0;
        int total = 0;
        char[] responses = new char[20];
        for (int i = 0; i < responses.length; i++) {
            System.out.printf("Enter answer for # %d: ", i+1);
            responses[i] = scan.nextLine().toUpperCase().trim().charAt(0);
            for (int j = 0; j < answerKey.length; j++) {
                if (responses[i] == (answerKey[j])) {
                    System.out.println(responses[i]);
                    numCorrect++; // I don't quite understand
                                  // what is happening here...
                }
            }
        }

        /* Display elements in userAnswers array */
        System.out.println("User answers are below");
        for (int i = 0; i < responses.length; i++) {
            System.out.print(responses[i] + " ");
        }
        System.out.println();
    }


$ java Drivers_License

Enter answer for # 1: a
Enter answer for # 2: b
Enter answer for # 3: c
Enter answer for # 4: d
Enter answer for # 5: a
Enter answer for # 6: b
Enter answer for # 7: c
Enter answer for # 8: d
Enter answer for # 9: a
Enter answer for # 10: b
Enter answer for # 11: c
Enter answer for # 12: d
Enter answer for # 13: a
Enter answer for # 14: b
Enter answer for # 15: c
Enter answer for # 16: d
Enter answer for # 17: a
Enter answer for # 18: b
Enter answer for # 19: c
Enter answer for # 20: d
No. of correct answers: 100
User answers are below
A B C D A B C D A B C D A B C D A B C D

最佳答案

您正在使用两个for循环（一个在另一个内部）。这些嵌套为循环。
上面的代码中发生的是，对于第一个数组中的每个索引i，第二个数组中的所有j都将被访问。

您要做的是只有一个for循环（共20个迭代），并并行访问两个数组中的元素。

    public class Drivers_License
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);

        int incorrect = 0;
        double grade = 0.0;
        String input;
        char[] answerKey = {'B', 'D', 'A', 'A', 'C',
                            'A', 'B', 'A', 'C', 'D',
                            'B', 'C', 'D', 'A', 'D',
                            'C', 'C', 'B', 'D', 'A'};
        System.out.println();

        int total = 0;
        char[] responses = new char[20];
        for (int i = 0; i < responses.length; i++)
        {
            System.out.printf("Enter answer for # %d: ", i+1);
            responses[i] = scan.nextLine().toUpperCase().trim().charAt(0);

        }

        int numCorrect = 0;
        for (int i = 0; i < responses.length; i++) {
           if (responses[i] == (answerKey[i])) { // Look here
                System.out.println(responses[i]);
                numCorrect++;
            }
        }

        /* Display elements in userAnswers array */
        System.out.println("User answers are below");
        for (int i = 0; i < responses.length; i++) {
            System.out.print(responses[i] + " ");
        }
        System.out.println();
    }