在Java中使用HashMap计算平均值（等级）

Question

嘿，我正在尝试根据地图中的数据计算平均值。

首先在代码中有一个 Student 类，其中创建了一个学生，其参数如下： 字符串名字，字符串姓氏，int registerDiaryNumber。

方法 equals、hashCode 和 toString 也被重写。

然后创建了 Grade 类，它以 8 int 作为参数（总共 8 个 Grade）

最后在main中有这段代码：

public static void main (String[] args) {

Student student1 = new Student("Terry", "Pratchett", 2);
Student student2 = new Student("Arashi", "Ryuuno", 3);
Student student3 = new Student("Nobunaga", "Oda", 4); 
Student student4 = new Student("Pheonix", "Wright", 5);
Student student5 = new Student("Ainz", "Gown", 1);

Grades student1Math = new Grades(4, 5, 4, 3, 2, 5, 5, 3);
Grades student2Math = new Grades(5, 6, 5, 5, 6, 5, 5, 4);
Grades student3Math = new Grades(3, 3, 5, 4, 3, 4, 5, 2);
Grades student4Math = new Grades(5, 4, 5, 3, 4, 5, 3, 5);
Grades student5Math = new Grades(4, 5, 5, 3, 3, 4, 6, 5);

Map<Student, Grades> mathGrades = new HashMap<>();
mathGrades.put(student1, student1Math);
mathGrades.put(student2, student2Math);
mathGrades.put(student3, student3Math);
mathGrades.put(student4, student4Math);
mathGrades.put(student5, student5Math);

for (Map.Entry<Student, Grades> entry : mathGrades.entrySet()){
    System.out.println("Number " + entry.getKey() +" got grades as follow:" +entry.getValue());
    System.out.println("Student average grade is: ");
    }
}

这就是我陷入困境的地方 - 我不知道如何计算给定成绩的平均值，我尝试将方法放入班级成绩中，但它不起作用。 如果您想检查整个代码，请检查下面的链接（这是 JAVA 训练营的作业，其中指出“使用 HashMap 创建一个程序来存储学生（个人）数据及其成绩。程序必须显示平均值”每个学生的成绩。” 平均值可以是 int 或 double（四舍五入）。

https://kodilla.com/pl/project-java/173235#

Answer 1

下面是JAVA代码，可能对这个问题有帮助。

这是另一个java文件中的Student类。

package StudentGradeTracker;

public class Student {

private int eng, maths, sci;

public Student(int eng, int maths, int sci) {
    this.eng = eng;
    this.maths = maths;
    this.sci = sci;
}

public Student() {
    // TODO Auto-generated constructor stub
}

@Override
public String toString() {
    return "[" + eng + ", " + maths + ", " + sci + "]";
}

public int getEng() {
    return eng;
}

public void setEng(int eng) {
    this.eng = eng;
}

public int getMaths() {
    return maths;
}

public void setMaths(int maths) {
    this.maths = maths;
}

public int getSci() {
    return sci;
}

public void setSci(int sci) {
    this.sci = sci;
}

}

这是 MainClass，它是另一个 java 文件。

package StudentGradeTracker;

import java.util.HashMap;

public class mainClass {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    
    
    HashMap<String, Student> hm = new HashMap<>();
    
    hm.put("Hassan", new Student(67, 65, 66));
    hm.put("Abrar", new Student(35,45,55));
    hm.put("Tausif", new Student(65,35,50));
    hm.put("Maikal", new Student(35,25,55));
    hm.put("Ali", new Student(64,65,60));
    
    for (String string : hm.keySet()) {
        calculateAverage(hm.get(string), hm, string);
    }
    
}

static void calculateAverage(Student student, HashMap<String, Student> 
hm1, String key)
{
    int sum = 0;
    
    sum = sum + student.getEng() + student.getMaths() + student.getSci();
    
    double avg = (double) sum / hm1.size();
    
    System.out.println("Key : " + key + " Marks : " + hm1.get(key) + " Percentage : " + avg + calculateGrade(avg));
    
}

static String calculateGrade(double avg){
    char result, grade;
    
    if(avg > 55.0 && avg <= 70.0){
        result = 'P';
        grade = 'A';
    }
    else if(avg > 45.0 && avg <= 55.0){
        result = 'P';
        grade = 'B';
    }
    else if(avg > 33.0 && avg <= 45.0){
        result = 'P';
        grade = 'C';
    }
    else{
        result = 'F';
        grade = ' ';
    }
    
    return " Result : " + result + " Grade : " + grade;
}

}

Answer 2

您需要更改

Grade

类的构造函数，例如采用整数

List

。

问题的解决方案将简单如下：

public static void main(String[] args) {
    Student student1 = new Student("Terry", "Pratchett", 2);
    Student student2 = new Student("Arashi", "Ryuuno", 3);
    Student student3 = new Student("Nobunaga", "Oda", 4);
    Student student4 = new Student("Pheonix", "Wright", 5);
    Student student5 = new Student("Ainz", "Gown", 1);

    // A static initialization of a list of integers
    Grades student1Math = new Grades(new ArrayList<Integer>() {{
        add(5);
        add(6);
        add(5); // add more here...
    }});
    Grades student2Math = new Grades(new ArrayList<Integer>() {{
        add(5);
        add(6);
        add(5);
    }});
    Grades student3Math = new Grades(new ArrayList<Integer>() {{
        add(3);
        add(3);
        add(5);
    }});
    Grades student4Math = new Grades(new ArrayList<Integer>() {{
        add(5);
        add(4);
        add(5);
    }});
    Grades student5Math = new Grades(new ArrayList<Integer>() {{
        add(4);
        add(5);
        add(5);
    }};

    Map<Student, Grades> mathGrades = new HashMap<>();
    mathGrades.put(student1, student1Math);
    mathGrades.put(student2, student2Math);
    mathGrades.put(student3, student3Math);
    mathGrades.put(student4, student4Math);
    mathGrades.put(student5, student5Math);

    for (Map.Entry<Student, Grades> entry : mathGrades.entrySet()){
        double currentStudentAvgSum = 0.0;
        
        List<Integer> studentGrades = mathGrades.get(entry.getKey());
        for(Dobule currentGrade : studentGrades){
            currentStudentAvgSum + = currentGrade;
        }
        double currentStudentAvg = currentStudentAvgSum / studentGrades.size();
        
        System.out.println("Student average grade is: " + currentStudentAvg);
    }
}

for 循环计算每个学生的平均分数。