Java 使用数组按姓名和分数对学生进行排序

昨晚我发布了一个关于这个的问题，但我仍然在努力。我需要对文本文件中的学生列表进行排序，首先按姓名（这种格式为姓氏、名字），然后按考试成绩。我不知道文本文件中会有多少学生，除了不到100人。我必须使用compareTo方法（我认为我做得对）和数组（我认为我没有正确地使用它）。我已经连续几个小时胡闹了，我就是不明白。这本教科书似乎对我没有任何帮助。如何让我的应用程序类打印已排序的学生姓名/成绩

其他说明是获得平均分数，并在低于平均分数的任何分数旁边发表评论。不过，在整理好分类后，我可以继续处理这些问题

这是我的密码

 package CH11AS8App;

 import java.io.FileReader;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.Scanner;


 public class kjkkkkkkkkkkk {

 public static void main( String[] args ) throws Exception {
    // TODO Auto-generated method stub

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



        int numOfStudents = 100;
        Student[] studentArray = new Student[numOfStudents];
        Scanner sc = null;

        int counter = 0;
        while (aScanner.hasNext()) {
            sc = new Scanner(aScanner.nextLine());
            String lastName = sc.next();
            String firstName = sc.next();
            int score = sc.nextInt();


            studentArray[counter++] = new Student(lastName, firstName, score);

            studentArray[counter] = new Student(lastName, firstName, score); 

            int average= 0;
            int sum = 0;
            sum += score; 
             if (counter < numOfStudents); 
            average = sum / counter;
            if (score <= (average - 10)) {
             System.out.println("Score 10 points under average");
            System.out.println("Student Average:" + average);
        }



            sc.close();


            // Display Welcome Message
            System.out.println("Welcome to the Student Scores Application.\n");

            //Sort Names
            Arrays.sort(studentArray,0,counter, new Comparator<Student>(){
                @Override
                public int compare(Student s1, Student s2) {
                    return s1.getLastName().compareTo(s2.getLastName());
                }
            });

            System.out.println();
            System.out.println("Student list by name:");
            System.out.println();
            for(int j = 0; j < counter; j++){  
                System.out.println(studentArray[j]);

            }

            //Sort Scores
            Arrays.sort(studentArray,0,counter, new Comparator<Student>(){
                @Override
                public int compare(Student s1, Student s2) {
                    return Integer.valueOf(s2.getScore()).
                                       compareTo(Integer.valueOf(s1.getScore()));
                }
            });


            System.out.println();
            System.out.println();
            System.out.println("Student list by score:");
            System.out.println();
            for(int j = 0; j < counter; j++){  
                System.out.println(studentArray[j]);

            }


            //Close Scanner
            aScanner.close();

包CH11AS8App；
导入java.io.FileReader；
导入java.util.array；
导入java.util.Comparator；
导入java.util.Scanner；
公共类KKKKKKKK{
公共静态void main（字符串[]args）引发异常{
//TODO自动生成的方法存根
扫描仪aScanner=新扫描仪(
新的文件阅读器（“src//chapt11//ch11AS8data.txt”）；
学生人数=100；
学生[]学生阵列=新学生[NumofStudentArray]；
扫描仪sc=空；
int计数器=0；
while（aScanner.hasNext（））{
sc=新扫描仪（aScanner.nextLine（））；
字符串lastName=sc.next（）；
字符串firstName=sc.next（）；
int score=sc.nextInt（）；
studentArray[counter++]=新学生（姓、名、分数）；
学生阵列[计数器]=新学生（姓、名、分数）；
整数平均=0；
整数和=0；
总和+=分数；
如果（柜台<学生）；
平均值=总和/计数器；
如果（score您的错误出现在
compareTo（）方法的最后一行
中：

改变

return examScore = s.examScore;

到



您希望返回一个差异，而不是设置实例变量！
我认为您应该将比较中的最后一行更改为如下所示：

    return (new Integer(examScore)).compareTo((new Integer(s.examScore));

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

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

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

    int nStudent = 100;
    Student[] studentArray = new Student[nStudent];
    Scanner lineScanner = null;

    int counter = 0;
    while (aScanner.hasNext()) {
        lineScanner = new Scanner(aScanner.nextLine());
        String lastName = lineScanner.next();
        String firstName = lineScanner.next();
        int examScore = lineScanner.nextInt();
        System.out.println("Student " + counter + " " + firstName + " "
                + lastName + " " + +examScore);

        studentArray[counter++]=new Student(lastName, firstName, examScore);
        lineScanner.close();
    }

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



    //sort based on first name
    Arrays.sort(studentArray,0,counter, new Comparator<Student>(){
        @Override
        public int compare(Student s1, Student s2) {
            return s1.getFirstName().compareTo(s2.getFirstName());
        }
    });
    System.out.println("Students sorted by first name in ascending order");
    for(int j = 0; j < counter; j++){  
        System.out.println(studentArray[j]);
    }

    //sort based on score
    Arrays.sort(studentArray,0,counter, new Comparator<Student>(){
        @Override
        public int compare(Student s1, Student s2) {
            return Integer.valueOf(s1.getExamScore()).
                               compareTo(Integer.valueOf(s2.getExamScore()));
        }
    });
    System.out.println("Students sorted by score in ascending order");
    for(int j = 0; j < counter; j++){  
        System.out.println(studentArray[j]);
    }

    //To compute the average:
    double sum = 0.0;
    for(int j = 0; j < counter; j++){  
        sum+=studentArray[j].getExamScore();
    }
    double average = (sum*1.0)/counter;
    System.out.println("Average Score = "+average );


    aScanner.close();
}

或

这将比较两个值并相应地返回

编辑：

程序中的一些更正：

在
Student
类中添加
toString（）
方法，如下所示：

@凌驾
公共字符串toString（）{
返回firstName+“”+lastName+：“+examcore；
}

更新应用程序中的
main（）
方法，如下所示：

    return (new Integer(examScore)).compareTo((new Integer(s.examScore));

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

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

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

    int nStudent = 100;
    Student[] studentArray = new Student[nStudent];
    Scanner lineScanner = null;

    int counter = 0;
    while (aScanner.hasNext()) {
        lineScanner = new Scanner(aScanner.nextLine());
        String lastName = lineScanner.next();
        String firstName = lineScanner.next();
        int examScore = lineScanner.nextInt();
        System.out.println("Student " + counter + " " + firstName + " "
                + lastName + " " + +examScore);

        studentArray[counter++]=new Student(lastName, firstName, examScore);
        lineScanner.close();
    }

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



    //sort based on first name
    Arrays.sort(studentArray,0,counter, new Comparator<Student>(){
        @Override
        public int compare(Student s1, Student s2) {
            return s1.getFirstName().compareTo(s2.getFirstName());
        }
    });
    System.out.println("Students sorted by first name in ascending order");
    for(int j = 0; j < counter; j++){  
        System.out.println(studentArray[j]);
    }

    //sort based on score
    Arrays.sort(studentArray,0,counter, new Comparator<Student>(){
        @Override
        public int compare(Student s1, Student s2) {
            return Integer.valueOf(s1.getExamScore()).
                               compareTo(Integer.valueOf(s2.getExamScore()));
        }
    });
    System.out.println("Students sorted by score in ascending order");
    for(int j = 0; j < counter; j++){  
        System.out.println(studentArray[j]);
    }

    //To compute the average:
    double sum = 0.0;
    for(int j = 0; j < counter; j++){  
        sum+=studentArray[j].getExamScore();
    }
    double average = (sum*1.0)/counter;
    System.out.println("Average Score = "+average );


    aScanner.close();
}

publicstaticvoidmain（字符串[]args）引发异常{
扫描仪aScanner=新扫描仪(
新的文件阅读器（“src//chapt11//ch11AS8data.txt”）；
System.out.println（“欢迎使用学生成绩应用程序。\n”）；
int nStudent=100；
学生[]学生阵列=新学生[n学生]；
Scanner lineScanner=null；
int计数器=0；
while（aScanner.hasNext（））{
lineScanner=新扫描仪（aScanner.nextLine（））；
字符串lastName=lineScanner.next（）；
String firstName=lineScanner.next（）；
int examcore=lineScanner.nextInt（）；
System.out.println（“学生”+计数器+“”+名字+“”
+lastName++++examcore）；
studentArray[counter++]=新学生（姓、名、ExamCore）；
lineScanner.close（）；
}
对于（int j=0；j

因为这是家庭作业，所以我不会给你完整的答案…但这里是你应该努力的总体想法

import java.io.FileReader;
import java.util.Scanner;

public class App {

    public static void main( String[] args ) throws Exception {
        // TODO Auto-generated method stub

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

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

        Student[] studentArray;

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

        int nStudent = 100;
        studentArray = new Student[nStudent];

        int counter = 0;

        while( aScanner.hasNext() ) {

            lastName = aScanner.next();
            firstName = aScanner.next();
            examScore = aScanner.nextInt();

            studentArray[counter] = new Student( lastName, firstName, examScore );

            System.out.println( "Student " + studentArray[counter].getFirstName() + " " +  studentArray[counter].getLastName() + "'s " + "Test Score is :" + studentArray[counter].getExamScore() );
            ++counter;
            if( counter >= nStudent ) {
                break;
            }
        }
    }

    static class Student implements Comparable<Student> {

        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( Student s ) {

            if( !lastName.equalsIgnoreCase( s.lastName ) ) {

                return lastName.compareToIgnoreCase( s.lastName );
            }

            if( !firstName.equalsIgnoreCase( s.firstName ) ) {

                return firstName.compareToIgnoreCase( s.firstName );

            }

            return examScore - s.examScore;

        }

    }

}

导入java.io.FileReader；
导入java.util.Scanner；
公共类应用程序{
公共静态void main（字符串[]args）引发异常{
//TODO自动生成的方法存根
Scanner aScanner=newscanner（newfilereader（“src/scores.txt”）；
System.out.println（“欢迎使用学生成绩应用程序”）；
System.out.println（）；
学生[]学生阵列；
字符串lastName；
字符串名；
int examcore=0；
双平均=0；
int nStudent=100；
学生阵列=新生[学生]；
int计数器=0；
while（aScanner.hasNext（））{
lastName=aScanner.next（）；
firstName=aScanner.next（）；
examcore=aScanner.nextInt（）；
学生阵列[计数器]=新学生（姓、名、ExamCore）；
System.out.println（“学生”+studentArray[counter].getFirstName（）+“”+studentArray[counter].getLastName（）+“'s”+”的测试分数为：“+studentArray[counter].getExamCore（））；
++计数器；
如果（计数器>=N学生）{
import java.io.FileReader;
import java.util.Scanner;

public class App {

    public static void main( String[] args ) throws Exception {
        // TODO Auto-generated method stub

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

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

        Student[] studentArray;

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

        int nStudent = 100;
        studentArray = new Student[nStudent];

        int counter = 0;

        while( aScanner.hasNext() ) {

            lastName = aScanner.next();
            firstName = aScanner.next();
            examScore = aScanner.nextInt();

            studentArray[counter] = new Student( lastName, firstName, examScore );

            System.out.println( "Student " + studentArray[counter].getFirstName() + " " +  studentArray[counter].getLastName() + "'s " + "Test Score is :" + studentArray[counter].getExamScore() );
            ++counter;
            if( counter >= nStudent ) {
                break;
            }
        }
    }

    static class Student implements Comparable<Student> {

        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( Student s ) {

            if( !lastName.equalsIgnoreCase( s.lastName ) ) {

                return lastName.compareToIgnoreCase( s.lastName );
            }

            if( !firstName.equalsIgnoreCase( s.firstName ) ) {

                return firstName.compareToIgnoreCase( s.firstName );

            }

            return examScore - s.examScore;

        }

    }

}