Question

我在尝试找出代码问题时遇到了问题。基本上，该程序应该是GPA计算器。

第一部分：

import java.io.*; 
import java.util.ArrayList;

public class Student {
    // Data 
    private String name;
    private int student_id;
    private double gpa;
    private ArrayList<Integer> grades;
    private int num_courses;

    // Methods
    // Constructor Method
    public Student() {
        name = "";
        student_id = 0;
        gpa = 0.0;
        grades = new ArrayList<Integer>();
    }

    // Accessor Methods (getters and setters)
    public void setGrade(int g) {
        grades.add(g);
        calcGPA();
    }

    public String getName() {
        return name;
    }

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

    public int getStudent_id() {
        return student_id;
    }

    public void setStudent_id(int student_id) {
        this.student_id = student_id;
    }

    public double getGPA() {
        return gpa;
    }

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

    public int getNum_courses() {
        return num_courses;
    }

    public void setNum_courses(int num_courses) {
        this.num_courses = num_courses;
    }

    // Functional Methods
    public void calcGPA() {
        int sum_grades = 0;
        for (int i=0; i<this.grades.size(); i++) {
            sum_grades = sum_grades * this.grades.get(i);
        }
        gpa = sum_grades/this.grades.size();
    }

    public void displayGrades() { 
        for (int i=0; i<this.grades.size(); i++) {
            System.out.println("Grade in course " + i + ": " + this.grades.get(i));
        }
    }
}

和第二节课：

import java.io.*;

public class TestStudent {
    public static void main(String[] args) {
        Student s1 = new Student();         //Object creation/instantiation
        s1.setName("John Rodgers");
        s1.setStudent_id(111);
        s1.setGrade(3);
        s1.setGrade(4);
        s1.setGrade(3);
        System.out.println("Student " + s1.getName() + "\'s GPA: " + s1.getGPA());

        Student s2 = new Student();
        s2.setName("Jenny Marshall");
        s2.setStudent_id(333);
        s2.setGrade(4);
        s2.setGrade(4);
        s2.setGrade(3);
        s2.setGrade(4);
        s2.setGrade(3);
        System.out.println("Student " + s2.getName() + "\'s GPA: " + s2.getGPA());
    }
}

输出显示为：

Student John Rodgers's GPA: 0.0
Student Jenny Marshall's GPA: 0.0

应该计算GPA，但它显示为0.0。

Answer 1

您的calcGPA()逻辑不正确（您正在制作0 的产品），而应该按如下所示对所有成绩求和：

public void calcGPA(){
   int sum_grades = 0;
   for(int i=0; i<this.grades.size(); i++){
       sum_grades = sum_grades + this.grades.get(i);//sum the grades
   }
    gpa = sum_grades/this.grades.size();
}

Java对象和类 - 我的代码出了什么问题？

1 个答案: