Question

这是我的代码，除了一个错误外，我几乎已经完成了所有的工作：

import java.util.*;
import java.io.*;

public class Proj5 {
public static void main(String[] args)throws IOException{
    Scanner s = new Scanner(System.in);
    int [] quizKey = {1,1,2,2,1,1,3,2,4,1,3,5,4,1,2};
    String [] userAnswers = new String[100];
    String [] wid = new String[100];
    int [][] userIndividualAnswers = new int[quizKey.length][userAnswers.length];
    int [] numCorrect = new int[quizKey.length];
    int max;
    int min;

    int lines=0;
    readInText();
    s = readInText();
    while(s.hasNext()){
        String line = s.nextLine();
        String[] tokens = line.split(",");
        wid[lines] = tokens[0];
        userAnswers[lines] = tokens[1];
        lines ++;

    }// end while loop
    Long[][] userAnswersInt = new Long[quizKey.length][lines];
    numCorrect = gradeSingleQuiz(lines, quizKey, userAnswers, numCorrect, userAnswersInt);
    double[] percentCorrect = new double[lines];
    percentCorrect = percentCorrect(lines, numCorrect, quizKey);
    char[] grades = new char[lines];
    grades = grade(numCorrect, lines);

    displayOutput(wid, lines, numCorrect, grades, percentCorrect);
}//end main

public static Scanner readInText()throws IOException{
    Scanner inFile = new Scanner(new File("QuizScores.txt"));
    return inFile;


}// end readInText

public static String[] userAnswers(String userAnswers[]){
    return userAnswers;
}

public static int[] gradeSingleQuiz(int lines, int quizKey[], String userAnswers[], int numCorrect[], Long userAnswersInt[][]){
    for (int j=0; j<lines; j++){
    numCorrect[j]=0;
        long[] ara = new long[userAnswers.length];
        long[] abc = new long[userAnswers.length];
        ara [j] = Long.parseLong(userAnswers[j]);
    for(int p=0; p<ara.length; p++){
        abc [p] = ara[j]%10;
        userAnswersInt[p][j] = ara[j]/10;
    }
    for(int n=0; n<=quizKey.length; n++){

        if(userAnswersInt[j][n]==(quizKey[n])){
                    numCorrect[j]++;    
            }
    }
    }//end for loop

return numCorrect;
}// end gradeSingleQuiz

public static int max(int max, int numCorrect[]){
    max = numCorrect[0];
    for(int r=1; r<numCorrect.length; r++){
        if(numCorrect[r]>max){
            max=numCorrect[r];
        }
    }
return max;
}

public static int min(int min, int numCorrect[]){
    min = numCorrect[0];
    for(int r=1; r<numCorrect.length; r++){
        if(numCorrect[r]<min){
            min=numCorrect[r];
        }
    }
return min;
}

public static char[] grade(int numCorrect[], int lines){
    char[] grade = new char[lines];
    for (int j=0; j<=lines; j++){

        if(numCorrect[j]>=14)
            grade[j]='A';
        else if((numCorrect[j]>=12)&&(numCorrect[j]<14))
            grade[j]='B';
        else if((numCorrect[j]>=11)&&(numCorrect[j]<12))
            grade[j]='C';
        else if ((numCorrect[j]>=9)&&(numCorrect[j]<11))
            grade[j]='D';
        else
            grade[j]='F';
    }
    return grade;
}//end grade


public static double[] percentCorrect(int lines, int numCorrect[], int quizKey[]){
    double[] centCorrect = new double[100];
    for (int j=0; j<=lines; j++){
    centCorrect[j] = numCorrect[j]/quizKey.length;
    }
return centCorrect;
}

public static void averageScore(int lines, double percentCorrect[]){
    double add=0;
    for(int d=0; d<=lines; d++){    
        add = percentCorrect[d] + add;
    }//end for loop
    System.out.println("Average: " + add + "%");
}// end averageScore

public static void displayOutput(String wid[], int lines, int numCorrect[], char grades[], double percentCorrect[]){
    System.out.println("Student ID    # Correct    %Correct    Grade");
    for(int i=0; i<lines; i++){
        System.out.println(wid[0] + "    " + numCorrect[i] + "    " +
                (percentCorrect[i]) + "    " + grades[i]);  
    }

}// end display output

}//end class

当我尝试编译它时，它给我这个错误，我正在使用eclipse：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 15
at Proj5.gradeSingleQuiz(Proj5.java:55)
at Proj5.main(Proj5.java:27)

有问题的一行

userAnswersInt[p][j] = ara[j]/10;

我似乎无法弄清楚自己，有什么我没有在这里看到的，或者我只是完全以错误的方式解决这个问题？

提前致谢

编辑：

来自txt文件的

txt是：

4563123,112211324135412
2312311,222121324135211
2312345,112211324135421
5527687,212111313124412
7867567,111111111111111

Answer 1

在gradeSingleQuiz（）方法中，数组ara的初始化大小为userAnswersArray，但是从j = 0到j = lines-1循环。数组userAnswersArray的大小始终为100，但lines的长度取决于控制台的输入。

Answer 2

我检查了你的逻辑，发现了以下逻辑错误

您将数组ara分配给长度为100，然后尝试循环一个只有15个元素长的数组对象

long [] ara = new long [userAnswers.length];
下面的行返回null，因此抛出空指针异常。

如果（userAnswersInt [j]的[N] ==（quizKey [N]））

我建议您重新审视逻辑，如果需要帮助，请在此处发布要求，可以帮助解决逻辑问题。

给我一个数组的超出界限错误，我不知道如何解决它

2 个答案: