计算成绩不起作用

Question

对于这段代码，我有一个分数分配给一个分数数组。我想计算成绩（例如：A：3 B：4 C：4 ...）。当我运行程序时，它说：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 70
    at ProcessMarks.gradeDistn(ProcessMarks.java:115)
    at ProcessMarks.main(ProcessMarks.java:38)

代码：

char[] grades = new char[testMarks.length];
getGrades(testMarks, grades);
int[] counts = gradeDistn (grades);

for (int i = 0; i < counts.length; i++){
    System.out.println( grades[i] + " : " + counts[i]);

public static void getGrades (int[] testMarks, char[] grades) {
    for (int i = 0; i < testMarks.length; i++) {
        if (testMarks[i] >= 90)
            grades[i] = 'A';
        else if (testMarks[i] >= 75)
            grades[i] = 'B';
        else if (testMarks[i] >= 60)
            grades[i] = 'C';
        else if (testMarks[i] >= 50)
            grades[i] = 'D';
        else if (testMarks[i] >= 45)
            grades[i] = 'E';
        else
            grades[i] = 'F';
    }
}

public static int[] gradeDistn (char[] grades){
    int[] counts = new int[6];
    for (int i = 0; i < grades.length; i++) //count the occurrences
        counts[grades[i]]++;
    return counts;
}

Answer 1

问题出在您的gradeDistn - 函数中。 您尝试使用等级作为数组的索引。但是等级是一个字符，你需要的是一个数字。 Java 只是将您的字符转换为整数，因此转换为字符的 ascii 代码。

所以你可以这样做：

public static int[] gradeDistn (char[] grades){
        int[] counts = new int[6];
        for (int i = 0; i < grades.length; i++) //count the occurrences
            counts[grades[i] - 'A']++;
        return counts;

    }

编辑：

输出应该是这样的：

for(int i = 0; i < counts.length; i++) {
   char gradeAsChar = 'A' + i;
   System.out.println(gradeAsChar + ":"+ counts[i]);
}