Java GPA计算问题

我的总数不会更新。每次我执行代码时，gpa显示0.0。我添加了gp，以查看在输入用户信息时，分数是否会更新，但不会更新。任何帮助都会很好！我看了其他问题，似乎无法解决我的问题

import javax.swing.JOptionPane;

public class GUITestClient {
    public static void main(String[] args) {

        StudentInfo student = new StudentInfo();
        double credits;
        String name = JOptionPane.showInputDialog("Please enter your name:");
        student.setName(name);
        credits = Double.parseDouble(JOptionPane.showInputDialog("Please enter the credits:"));
        student.setCredits(credits);

        String grade = JOptionPane.showInputDialog("Please enter your grade:");
        student.setGrade(grade);

        JOptionPane.showMessageDialog(null, student.displayStudentInformation());           
    } 
}

public class StudentInfo {
        private String  name;
        private double  totalGradePoints;
        private double  credits;
        private String  grade;
        private double  gpa;

        public StudentInfo(){
            setGrade(null);
            setCredits(0);
            setGradePoints(0);
        }
        public StudentInfo(double credits, double totalGradePoints, String grade){
            setGrade(grade);
            setCredits(credits);
            setGradePoints(totalGradePoints);
        }

        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }

        public String getGrade() {
            return grade;
        }
        public void setGrade(String grade) {
            this.grade = grade;
        }
        public double getCredits() {
            return credits;
        }
        public void setCredits(double credits) {
            this.credits = credits;
        }

        public double getGradePoints() {
            return totalGradePoints;
        }
        public void setGradePoints(double totalGradePoints) {
            this.totalGradePoints = totalGradePoints;
        }

        public double getGpa() {
            return gpa;
        }
        public void setGpa(double gpa) {
            this.gpa = gpa;
        }

        public double addClass(double totalGradePoints, String grade){
        double gradePoints = 0;
        if(grade.equals("A")){
            gradePoints = 4.0;
        }else if(grade.equals("B")){
            gradePoints = 3.0;
        } else if(grade.equals("C")){
            gradePoints = 2.0;
        } else if(grade.equals("D")){
            gradePoints = 1.0;}
        totalGradePoints = (totalGradePoints +gradePoints);

        return getGradePoints();
        }

        public double getGPA(){
            this.setGpa(this.getCredits() / this.getGradePoints());
            return this.getGpa();
        }

        public String displayStudentInformation(){
            String output = "";

            output = output + "Name: " + this.getName() + "\n";
            output = output + "Total Credits: " + this.getCredits() + "\n";
            output = output + "Your grade is: " + this.getGrade() + "\n";
            output = output + "Your GPA is: " + this.getGpa() +  "\n";
            output = output + "Press any key to continue!" + "\n";
            output = output + "gp" + totalGradePoints + "\n";

            return output;
        }
}

---

在addClass方法中，将totalGradePoints作为局部变量

public double addClass(double totalGradePoints, String grade)

您应该使用全局变量totalGradePoints，而不是局部变量。因此，请删除该变量，使该方法看起来像

public double addClass(String grade)

但是我没有看到任何地方可以调用addClass方法

    public double addClass(double totalGradePoints, String grade){
    double gradePoints = 0;
    if(grade.equals("A")){
        gradePoints = 4.0;
    }else if(grade.equals("B")){
        gradePoints = 3.0;
    } else if(grade.equals("C")){
        gradePoints = 2.0;
    } else if(grade.equals("D")){
        gradePoints = 1.0;}

    totalGradePoints = (totalGradePoints +gradePoints);
}

问题在addClass的最后一个语句中。Java是按值传递的，这意味着此处可见的totalGradePoints是addClass方法中的一个局部变量，包含调用addClass时传递的任何值的副本。对该值所做的任何更新仅影响本地副本，而不影响原始变量

方法签名不需要totalGradePoints参数。应该是

public double addClass(String grade) {
    ...

---

您需要将本地成绩点添加到类的成员变量totalGradePoints。

问题在于您的this.getGradePoints。它不是一个值的getter，并且您不在函数中为StudentInfo student=new StudentInfo中的学生的同一对象实例设置值； 您必须在创建的对象“student”上设置所有setter变量

试试这个：

package guitestclient;

import javax.swing.JOptionPane;

public class GUITestClient {
    public static void main(String[] args) {

        StudentInfo student = new StudentInfo();
        double credits;
        double gradePoints = 0;
        double gradePointsTot = 0;
        double gpa = 0;
        int classCount = 0;


        String name = JOptionPane.showInputDialog("Please enter your name:");
        student.setName(name);
      do{
        credits = Double.parseDouble(JOptionPane.showInputDialog("Please enter the credits:"));
        student.setCredits(credits);

        String grade = JOptionPane.showInputDialog("Please enter your grade:");
        student.setGrade(grade);

        //calculates gpa value for grade
        gradePoints = StudentInfo.addClass(gradePoints, grade);
        gradePointsTot += gradePoints;
        classCount++;
     } while (classCount < 5);    

        //after loop
        student.setGradePoints(gradePointsTot);
        gpa = StudentInfo.getGPA(credits, gpa, classCount);
        student.setGpa(gpa);


        JOptionPane.showMessageDialog(null, student.displayStudentInformation());           
    } 
}

class StudentInfo {
        private String  name;
        private double  totalGradePoints;
        private double  credits;
        private String  grade;
        private double  gpa;

        public StudentInfo(){
            setGrade(null);
            setCredits(0);
            setGradePoints(0);
        }
        public StudentInfo(double credits, double totalGradePoints, String grade){
            setGrade(grade);
            setCredits(credits);
            setGradePoints(totalGradePoints);
        }

        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }

        public String getGrade() {
            return grade;
        }
        public void setGrade(String grade) {
            this.grade = grade;
        }
        public double getCredits() {
            return credits;
        }
        public void setCredits(double credits) {
            this.credits = credits;
        }

        public double getGradePoints() {
            return totalGradePoints;
        }
        public void setGradePoints(double totalGradePoints) {
            this.totalGradePoints = totalGradePoints;
        }

        public double getGpa() {
            return gpa;
        }
        public void setGpa(double gpa) {
            this.gpa = gpa;
        }

        public static double addClass(double totalGradePoints, String grade){
        double gradePoints = 0;
        if(grade.equals("A")){
            gradePoints = 4.0;
        }else if(grade.equals("B")){
            gradePoints = 3.0;
        } else if(grade.equals("C")){
            gradePoints = 2.0;
        } else if(grade.equals("D")){
            gradePoints = 1.0;}
        totalGradePoints = (totalGradePoints +gradePoints);

        return totalGradePoints;
        }

        public static double getGPA(double totalGradePoints, double credits, double gpa){
            gpa = (credits * totalGradePoints)/ credits;
            return gpa;
        }


        public String displayStudentInformation(){
            String output = "";

            output = output + "Name: " + this.getName() + "\n";
            output = output + "Total Credits: " + this.getCredits() + "\n";
            output = output + "Your grade is: " + this.getGrade() + "\n";
            output = output + "Your GPA is: " + this.getGpa() +  "\n";
            output = output + "Press any key to continue!" + "\n";
            output = output + "gp" + this.getGradePoints() + "\n";

            return output;z
        }
}

---

是的，这将是一个多个班级/年级项目的循环，但我想确保我能首先得到一个。我按照您的指示进行了操作，但它们仍然不会根据用户输入进行更新。我不确定我是否理解这会是什么样子？获得/设置分数？我不仅想现在就拥抱你，我还想开始跑步，跳起来，用腿搂住你，拥抱你直到感觉奇怪。这不是100%正确，但它让我达到了我需要的地方。这里是唯一的更正：public static double getGPAdouble totalGradePoints，double credits，double gpa{gpa=credits*totalGradePoints/credits；return gpa；}您还应该检查已接受的答案是否对您的问题找到解决方案最有帮助：如果我知道答案的位置，我会这样做。你不会碰巧知道如何在do while循环中添加累加器来累加变量Credit和totalGradePoints吧？它就在答案左侧的upvote/downvote箭头的正下方