Java-对象不能存储数据

Question

我和爸爸将范围缩小到对象无法存储数据。另外，我是java新手。该代码应该在控制台中打印名字、姓氏、成绩和平均成绩。我认为问题出在 public double getCalcGraeAverage() 中，但如果错误，请纠正我。

import java.util.Scanner;
/**
 * Write a description of class Student here.
 * 
 * @author XXXX
 * @version XXXX
 */
public class Student
{
    String firstName;
    String lastName;
    int gradeLevel;
    double gradeAverage;
    int totalAssignments;
    double totalPoints;

      /**
     * Create a new student with student's name, grade, and average
     */
    public Student(String newFirstName, String newLastName, int newGradeLevel, double newGradeAverage)
    {
        firstName = newFirstName;
        lastName = newLastName;
        gradeLevel = newGradeLevel;
        gradeAverage = newGradeAverage = 0.0;
    }

      /**
     * Return the student's first name. 
     */
    public String getFirstName()
    {
        return firstName;
    }

      /**
     * Return the student's last name. 
     */
    public String getLastName()
    {
        return lastName;
    }

      /**
     * Return the grade level of the student. 
     */
    public int getGradeLevel()
    {
        return gradeLevel;
    }

         /**
     * Calculates grade average. 
     */
    public double getCalcGradeAverage()
    {

       double gradeAverage = totalAssignments / totalPoints;
       return gradeAverage;
    }

    public static void main (String[] args)
    { 
        Student student1 = new Student ("XXXX", "XXXX", 11, 0.0);

        System.out.println("The student's first name is: " + student1.getFirstName());
        System.out.println("The student's last name is: " + student1.getLastName());
        System.out.println("The student's grade level is: " + student1.getGradeLevel());

        System.out.println("Please enter the total assignment points the student has earned: ");

        Scanner input = new Scanner(System.in);
        Double totalAssignments  = input.nextDouble();

        System.out.println("Please enter the number of assignments given: ");

        double totalpoints  = input.nextDouble();

        System.out.println(student1.getFirstName() + " " + student1.getLastName() +  " average grade is" + student1.getCalcGradeAverage());
    }
}

Answer 1

在您的代码中，您是:

1. 创建一个学生student1对象
2. 从System.in读取totalAssignments、totalpoints
3. 调用student1.getCalcGradeAverage()

在步骤 2 和 3 之间，您必须将 student 的字段 totalAssignments、totalpoints 设置为您读取的值，否则他们将保留其值默认值为零。例如

student1.totalAssignments = totalAssignments;
student1.totalpoints = totalpoints;

此外，由于 totalAssignments 的类型为 int，您可能希望将其读作:

int totalAssignments  = input.nextInt();