问题：

将单独的“double”值转换为ArrayList中的数组

樊烨烨

2023-03-14

我创建了一个程序，其中包含一个ArrayList，其中包含学生成绩的单独“双”值。然而，本课程要求创建一个分数整数数组，而不是我之前使用的单独值。

我的学生类代码（我已经删除了不相关的代码，开门见山）：

public class Student {

    private int[] Grades = new int[3];

    public Student(String stuid, String fname, String lname, String email, int age, int[] grades) {
        this.Grades = grades;
    }

    public int[] getGrades() {
        return Grades;
    }

    public void setGrades(int[] grades) {
        Grades = grades;
    }

    public String toString() {
        return String.format("StuID: %s\t First Name: %s\t Last Name: %s\t E-Mail: %s\t Age: %s\t Grades: %s\t",
                this.StuID, this.FName, this.LName, this.Email, this.Age, this.Grades);
    }
}

名册等级：

import java.util.ArrayList;

public class Roster {
    static ArrayList<Student> studentArray;

    public Roster(ArrayList<Student> ar) {
        studentArray = ar;
    }

    // 3.C - Print Average Grade
    public static void print_average_grade(String studentID) {
        for (Student v : studentArray) {
            if (v.getStuID().equals(studentID)) {
                double total = v.getGrade1() + v.getGrade2() + v.getGrade3();
                double average = total / 3;
                System.out.println("Student ID#" + studentID + " Grade AVG= " + average);
            }
        }
    }

    public static void main(String[] args) {

        ArrayList<Student> studentArray = new ArrayList<Student>();

        studentArray.add(new Student("1", "John", "Smith", "John1989@gmail.com", 20, 88, 79, 59));
        studentArray.add(new Student("2", "Susan", "Erickson", "Erickson_1990@gmailcom", 19, 91, 72, 85));
        studentArray.add(new Student("3", "Jack", "Napoli", "The_lawyer99yahoo.com", 19, 85, 84, 87));
        studentArray.add(new Student("4", "Erin", "Black", "Erin.black@comcast.net", 22, 91, 98, 82));
        studentArray.add(new Student("5", "Captain", "Planet", "PowIsYours@planet.edu", 65, 99, 98, 97));

        new Roster(studentArray);
        for (Student v : studentArray) {
            print_average_grade(v.getStuID());
        }
    }
}

我已经将分隔的值（Grade1、Grade2、Grade3）更改为“int[]Grades”数组，修改了构造函数，并添加了setter和getter。所以，我认为学生班很好，然而花名册班，是我陷入困境的地方。有两件事：

1）如何将等级的值添加到现在是ArrayList一部分的数组中？

2）我如何调整我的平均等级方法来执行与之前相同的任务，但使用数组的值？

任何帮助都会很好，因为我已经被困在这个问题上好几天了。

谢谢

P、如果发布完整的代码会更容易，我将很乐意发布它，以帮助解决这个问题。

共有2个答案

南宫阳冰

2023-03-14

下面是我如何完成相同项目的。我的仍在评分中，所以我不知道它是否会第一次通过。但也许我的分享会对某人有所帮助。

import java.util.ArrayList;

public class Roster {

   public static ArrayList<Student> students = new ArrayList<>();   

    public static void main(String[] args)
    {
        // input student grades
        int[] grade0 = {0,0,0}; // filler to make grade array equal to student ID
        int[] grade1 = {88, 79, 59};
        int[] grade2 = {91, 72, 85};
        int[] grade3 = {85, 84, 87};
        int[] grade4 = {91, 98, 82};
        int[] grade5 = {99, 98, 97};

        // input student info
        addStudent(0, "null", "null", "null@null.com", 0, grade0); // filler to align student ID with array number
        addStudent(1, "John", "Smith", "John1989@gmail.com", 20, grade1);
        addStudent(2, "Suzan", "Erickson", "Erickson_1990@gmailcom", 19, grade2);
        addStudent(3, "Jack", "Napoli", "The_lawyer99yahoo.com", 19, grade3);
        addStudent(4, "Erin", "Black", "Erin.black@comcast.net", 22, grade4);
        addStudent(5, "Habib", "Trump", "someemail@mywqu.edu", 42, grade5);

        // printing related subroutines/methods
        Student student = students.get(3); //get student 3 for printing
        System.out.println("Print one student:");
        student.print(); //prints specific student data as per 2.D
        printAllStudents(); //print all students as per 3.B
        print_invalid_emails(); //checks email addresses for proper form as per 3.D
        printAverageGrade(); //print grades as per 3.C    
        remove(); // removes student 5 as per 3.A
        printAllStudents(); // shows student 3 has been removed
        remove(); // shows error as student already removed
    }

    public static void addStudent(int studentID, String firstName, String lastName, String email, int age, int[] grades){
            Student newStudent = new Student(studentID, firstName, lastName, email, age, grades);
            students.add(newStudent);
    }

    public static void remove(){ // remove student 
            try{
                System.out.println("Remove student: 5 ");
                students.remove(5);
            } catch (IndexOutOfBoundsException e) {
                System.err.println("IndexOutOfBoundsException: No such student ID");
    }}

    public static void printAverageGrade(){ // print Average Grade
                System.out.println("Print Average Grade: ");
            for(Student eachItem : students){
                double total = eachItem.getgrades()[0] + eachItem.getgrades()[1] + eachItem.getgrades()[2];
                double average = total / 3;
                System.out.println(average);
    }}

    public static void printAllStudents(){ // print All Students
                System.out.println("Print all Students: ");
            for(int i=0; i < students.size(); i++){
                students.get(i).print();    
    }}

    public static void print_invalid_emails(){ // check Email Addresses for proper form
            System.out.println("Check for proper form of email addresses: ");       
            for(Student student : students) {
            if (student.getemail().contains("@") && student.getemail().contains(".") && !student.getemail().contains(" ")){
                System.out.println("Passed format check");
            }
            else
            {
                System.out.println("Invalid email address");
            }}
    }}

public class Student extends Roster
{
   private int studentID;
   private String firstName;
   private String lastName;
   private String email;
   private int age;
   private int[] grades = new int[3];

   public Student(int studentID, String firstName, String lastName, String email, int age, int[] grades)
   {
       setstudentID(studentID);
       setfirstName(firstName);
       setlastName(lastName);
       setemail(email);
       setage(age);
       setgrades(grades);
   }           
   public int getstudentID(){
       return studentID;
   }
   public void setstudentID(int studentID)
   {
       this.studentID = studentID;
   }   
   public String getfirstName(){
       return firstName;
   }
   public void setfirstName(String firstName)
   {
       this.firstName = firstName;
   }
   public String getlastName(){
       return lastName;
   }
   public void setlastName (String lastName)
   {
       this.lastName = lastName;
   }
   public String getemail(){
       return email;
   }
   public void setemail(String email)
   {
       this.email = email;
   }
   public int getage(){
       return age;
   }
   public void setage(int age)
   {
       this.age = age;
   }
   public void setgrades(int[] grades){
       this.grades = grades;
   }
   public int[] getgrades(){
       return grades;
   }
   public void print(){
       System.out.println(
       "Student ID = \t" + getstudentID() + ", \t" +
       "First Name = \t" + getfirstName() + ", \t" +
       "Last Name = \t" + getlastName() + ", \t" + 
       "Email = \t" + getemail() + ", \t" +
       "Age = \t" + getage());
   }
}

端木高邈

2023-03-14

我试图根据这两个要求（数组、平均值）修复您的代码。请参阅以下代码（我已经测试过）。

学生班级：

public class Student {

    String StuID;
    String FName;
    String LName;
    String Email;
    int Age;
    private int[] Grades = new int[3];

    public Student(String stuid, String fname, String lname, String email, int age, int[] grades) {
        this.StuID = stuid;
        this.FName = fname;
        this.LName = lname;
        this.Email = email;
        this.Grades = grades;
    }

    public int[] getGrades() {
        return Grades;
    }

    public void setGrades(int[] grades) {
        Grades = grades;
    }

    public String toString() {
        return String.format("StuID: %s\t First Name: %s\t Last Name: %s\t E-Mail: %s\t Age: %s\t Grades: %s\t", this.StuID, this.FName, this.LName, this.Email, this.Age, this.Grades);
    }

    public String getFName() {
        return FName;
    }

    public void setFName(String fName) {
        FName = fName;
    }

    public String getEmail() {
        return Email;
    }

    public void setEmail(String email) {
        Email = email;
    }

    public int getAge() {
        return Age;
    }

    public void setAge(int age) {
        Age = age;
    }

    public String getStuID() {
        return StuID;
    }

    public void setStuID(String stuID) {
        StuID = stuID;
    }

    public String getLName() {
        return LName;
    }

    public void setLName(String lName) {
        LName = lName;
    }
}

名册等级：

import java.util.ArrayList;

public class Roster {
    ArrayList<Student> studentArray;

    public Roster(ArrayList<Student> ar) {
        studentArray = ar;
    }

    // 3.C - Print Average Grade
    public void print_average_grade(String studentID) {
        for (Student v : studentArray) {
            if (v.getStuID().equals(studentID)) {
                double total = v.getGrades()[0] + v.getGrades()[1] + v.getGrades()[2];
                double average = total / 3;
                System.out.println("Student ID#" + studentID + " Grade AVG= " + average);
            }
        }
    }

    public static void main(String[] args) {

        ArrayList<Student> studentArray = new ArrayList<Student>();

        int[] grades1 = {88, 79, 59};
        int[] grades2 = {91, 72, 85};
        int[] grades3 = {85, 84, 87};
        int[] grades4 = {91, 98, 82};
        int[] grades5 = {99, 98, 97};

        studentArray.add(new Student("1", "John", "Smith", "John1989@gmail.com", 20, grades1));
        studentArray.add(new Student("2", "Susan", "Erickson", "Erickson_1990@gmailcom", 19, grades2));
        studentArray.add(new Student("3", "Jack", "Napoli", "The_lawyer99yahoo.com", 19, grades3));
        studentArray.add(new Student("4", "Erin", "Black", "Erin.black@comcast.net", 22, grades4));
        studentArray.add(new Student("5", "Captain", "Planet", "PowIsYours@planet.edu", 65, grades5));

        Roster r = new Roster(studentArray);
        for (Student v : studentArray) {
            r.print_average_grade(v.getStuID());
        }
    }
}

输出：

Student ID#1 Grade AVG= 75.33333333333333
Student ID#2 Grade AVG= 82.66666666666667
Student ID#3 Grade AVG= 85.33333333333333
Student ID#4 Grade AVG= 90.33333333333333
Student ID#5 Grade AVG= 98.0

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