java - 从 .txt 调用列表作为数组并需要显示平均值

Question

.txt 文件如下所示:

Gator Ali 85
Vator Ella 75
Beam James 95
Lastin Class 55

我看到其他人试图在这里获取类似的代码，但没有任何帮助。
我可以得到平均值；但是，如果分数低于平均分 10 分，我还需要打印出来。
这是我的输出:运行:

欢迎使用学生成绩申请表。

Ali Gator 85
Ella Vator 75
James Beam 95
Class Lastin 55
Beam, James: 95
Gator, Ali: 85
Lastin, Class: 55
Vator, Ella: 75

Your score is 10 points or more below the class average

Class Average: 77.5

这是我的代码:

public static void main(String[] args) throws Exception {

    Scanner aScanner = new Scanner(new FileReader("src//chapt11//Studentdata.txt"));
    System.out.println("Welcome to the Student Scores Application.\n");

    int nStudent = 100;
    Student[] studentArray = new Student[nStudent];
    int counter = 0;
    while (aScanner.hasNext()) {
        String lastName = aScanner.next();
        String firstName = aScanner.next();
        int score = aScanner.nextInt();
        System.out.println(firstName + " " + lastName + " " + score);
        studentArray[counter++] = new Student(lastName, firstName, score);  
        Arrays.sort(studentArray, 0, counter); 
    } 

    System.out.println();

    for(int j = 0; j < counter; j++){  
        System.out.println(studentArray[j]);
    }

    double sum = 0;
    for(int j = 0; j < counter; j++){    
        sum += studentArray[j].getExamScore();
    }
    double average = (sum*1.0)/counter;

    for(int j = 0; j < counter; j++){    
        int score = studentArray[j].getExamScore();
        if (score <= (average - 10)){
             System.out.println("Your score is 10 points or more below the class average");
        } 
    }
    System.out.println();
    System.out.println("Class Average: " + average);

    System.out.println();
    aScanner.close();  
}

class Student implements Comparable<Student> {
private String firstName;
private String lastName;
private int score;

public Student(String firstName, String lastName, int score) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.score = score;
}

public int getExamScore() {
    return score;
}

public String getFirstName() {
    return firstName;
}

public String getLastName() {
    return lastName;
}

@Override
public int compareTo(Student s) {
    if(!firstName.equalsIgnoreCase( s.firstName)) {
        return firstName.compareToIgnoreCase(s.firstName);
    }
    if(!lastName.equalsIgnoreCase(s.lastName)) {
        return lastName.compareToIgnoreCase(s.lastName);
    }
        return score - s.score;
    }
 @Override 
 public String toString(){ 
        return firstName + ", " + lastName + ": "+ score;
    }
}

Answer 1

我发现您的代码存在一些问题。

首先，不需要调用Arrays.sort每次添加 Student到studentArray 。将此方法调用放置在 while 末尾之外只需调用一次该方法即可对整个数组进行排序。

其次，更重要的是，您想要 Student 怎么样？比较对象？

compareTo里面的方法Student没有意义。如果您希望学生仅按分数排序，您应该这样做:

@Override
public int compareTo(Student s) {
    return this.score - s.score;
}

就预期输出而言，这就是正在发生的事情。

以下行打印每个 Student当它们添加到数组中时:

System.out.println(firstName + " " + lastName + " " + score);

这部分打印每个 Student再次反对:

for (int j = 0; j < counter; j++) {
    System.out.println(studentArray[j]);
}

只有在 score <= (average - 10) 时才会打印此行评估结果为真:

System.out.println("Your score is 10 points or more below the class average");

我相信您现在已经看到问题所在了。