为什么＃字符在Perl中被视为“单词”字符？(Why is the # character seen as a 'word' character in Perl?)

 你忘了填充成绩数组:)你需要： 
 
grades[n] = grade;
 
 在递增n之前; 否则grade数组将为空。 除此之外，n ++可以正常工作： 
 
public static char[] grading(int[] testMarks) {

    char grade = '0';
    char[] grades = new char[testMarks.length];
    int value = 0;
    int n = 0;
        while (n < testMarks.length) {
            value = testMarks[n];
            if (value >= 90) {
            grade = 'A';
            }
            else if (value < 90 && value >= 75) {
            grade = 'B';
            }
            else if (value < 75 && value >= 60) {
            grade = 'C';
            }
            else if (value < 60 && value >= 50) {
            grade = 'D';
            }
            else if (value < 50 && value >= 45) {
            grade = 'E';
            }
            else {
            grade = 'F';
            }
            grades[n] = grade;
            n++;
    }
    return grades;
}

You forgot to populate the grades array :) you need to:
 
grades[n] = grade;
 
before incrementing n; otherwise the grades array would be empty. Other than that, n++ would work just fine:
 
public static char[] grading(int[] testMarks) {

    char grade = '0';
    char[] grades = new char[testMarks.length];
    int value = 0;
    int n = 0;
        while (n < testMarks.length) {
            value = testMarks[n];
            if (value >= 90) {
            grade = 'A';
            }
            else if (value < 90 && value >= 75) {
            grade = 'B';
            }
            else if (value < 75 && value >= 60) {
            grade = 'C';
            }
            else if (value < 60 && value >= 50) {
            grade = 'D';
            }
            else if (value < 50 && value >= 45) {
            grade = 'E';
            }
            else {
            grade = 'F';
            }
            grades[n] = grade;
            n++;
    }
    return grades;
}