java - 使用带有数组的compareTo方法按姓名和考试成绩对学生进行排序

Question

我需要使用比较接口(interface)和compareTo 方法按字母顺序对学生列表进行排序，然后按测试分数进行排序。我正在努力让它在我的应用程序中发挥作用。

需要从文本文件中读取名称列表。我不知道我的教授使用的文本文件中会有多少个名字，只是它会少于 100 个。我还应该在底部显示成绩的平均值，并在任何名字旁边写一条消息比平均分低 15 分的学生。我还没有真正开始编写消息部分，因为我目前一直在打印和排序姓名和分数。

文本文件应如下所示:

Steelman Andrea 95

Murach Joel 98

Lowe Doug 82

Murach Mike 93

这就是我到目前为止所拥有的......如果有人能给我一点指导，我将不胜感激。谢谢。

package chapt11;
import java.io.FileReader;  
import java.util.Arrays; 
importjava.util.Scanner;
public class CH11AS8App {

/**
 * @param args
 */
public static void main(String[] args) throws Exception {

    System.out.println("Welcome to the Student Scores Application.");
    System.out.println();

    Scanner aScanner = new Scanner(new FileReader(
            "src//chapt11//ch11AS8data.txt"));

    Student [] studentArray;

    String lastName;
    String firstName;
    int examScore = 0;
    double average = 0;

    int nStudent = 100;  //array size not set unit run time
    studentArray = new Student[nStudent];
    
    for (int i=0; i<nStudent; i++)
    {
    System.out.println();

        while (aScanner.hasNext()) {
            lastName = aScanner.next();
            firstName = aScanner.next();
            examScore = aScanner.nextInt();

            System.out.println("Student " + nStudent++ + " " + firstName
                    + " " + lastName + " " + +examScore);
        
            studentArray[i] = new Student(lastName, firstName, examScore);
        
    
    }
        double sum = 0.0;
        sum += examScore;
        average = sum/nStudent;
    
        Arrays.sort(studentArray);

        System.out.println();

        for (Student aStudent: studentArray)
        {
            System.out.println(aStudent);
            
            if (examScore<= (average-10))
            {
                System.out.println ("Score 10 points under average");
        }
        System.out.println("Student Average:" +average);

        }
}
}
public interface Comparable {
    int compareTo(Object o);
}

class Student implements Comparable {

    private String firstName;
    private String lastName;
    private int examScore;

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

    // Get & Set Methods
    public int getExamScore() {
        return examScore;
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    @Override
    public int compareTo(Object o) {
        Student s = (Student) o;

        if (s.lastName.equals(lastName)) {
            return firstName.compareToIgnoreCase(s.firstName);
        } else {
            return lastName.compareToIgnoreCase(s.lastName);
        }
    }

    public String toString() {
        return lastName + ", " + firstName + ": " + examScore;
    
    }

}

}

Answer 1

首先，完全删除您的Comparable 界面。使用Comparable来自 JDK。

将您的代码更改为此

public static class Student implements Comparable<Student> {

    // rest of class omitted

    @Override
    public int compareTo(Student s) {
        if (s.lastName.equals(lastName)) {
            return firstName.compareToIgnoreCase(s.firstName);
        }
        return lastName.compareToIgnoreCase(s.lastName);return
    }
}

另请注意，条件返回后没有“else”，因此我省略了代码的冗余部分