GPA数组计算错误

Question

我有我的GPA程序的问题，我必须使用两个数组来存储一个等级，它是学分，并计算GPA。到目前为止，除了gpa不会正确计算，我不知道我错过了什么（可能很简单），所有其他东西似乎都在工作。

我的代码到目前为止是：

千兆帕类：

import java.util.*; 

public class Gpa{ 

     int[] credits = new int[4]; 
     String[] grades = new String[4]; 

     private int numCourses; 
     private int maxCourses; 
     private int sumOfCourses; 
     private int sumCredits; 
     private int sumPoints; 
     int newCredits; 
     int totalSum = 0; 
     int total = 0; 


     public Gpa(int noCourses){ 
     maxCourses = noCourses; 
     numCourses = 0; 


     } 

     public void addCourse(int _newCredits, String newGrade){ 
     for (int i=0; i<maxCourses; i++){ 
      newCredits = _newCredits; 
      credits[i] = newCredits; 
     } 
     for (int i=0; i<maxCourses; i++){ 
      grades[i] = newGrade; 
     } 
      switch (newGrade) { 
       case "A": 
       case "a": 
        newGrade = "4"; 
        break; 
       case "B": 
       case "b": 
        newGrade = "3"; 
        break; 
       case "C": 
       case "c": 
        newGrade = "2"; 
        break; 
       case "D": 
       case "d": 
        newGrade = "1"; 
        break; 
       case "F": 
       case "f": 
        newGrade = "0"; 
        break; 
       } 
      sumPoints = sumPoints + (newCredits * Integer.parseInt(newGrade)); 
      numCourses++; 

     } 

     public double calcGPA(){ 
     for (int i=0; i<maxCourses; i++){ 
      sumCredits = sumCredits + newCredits; 
     } 
     double gpa = (double)sumPoints/sumCredits; 
     return gpa; 
     } 


















} // end class 

测试仪类：

import java.util.Scanner; 

public class GpaTestEx2 
{ 

    public static void main (String[] args) 
    { 
     //declarations 
     Scanner in = new Scanner(System.in); //input object 
     int numCourses; //number of courses - can be changed 
     int credits;  //number of credits for a course 
     String grade;  //grade for course 


     //read in number of courses 
     System.out.print("Enter number of courses: "); 
     numCourses = in.nextInt(); 

     //create Gpa object to hold specified number of courses 
     Gpa myGPA = new Gpa(numCourses); 

     //read in all courses and add course information to Gpa object 
     for (int k=0; k<numCourses; k++) 
     { 
      System.out.print("Enter credits for course " + (k+1) + ": "); 
      credits = in.nextInt(); 
      System.out.print("Enter grade for course " + (k+1) + ": "); 
      grade = in.next(); 

      myGPA.addCourse(credits, grade); 
     } 

     //print results 
     System.out.println(); 
     System.out.printf("GPA is %4.2f%n", myGPA.calcGPA()); 

    } //end main 
} 

当我进入课程学分和档次不正确地计算GPA 。例如，如果用户输入说有2门课程，其中一门课程有4学分，A分等级，另一门课程有3学分，等级为B，我应得3.57分时获得约4.17分的GPA。

任何帮助将是伟大的，我可能会或可能不会错过简单的东西。

Answer 1

似乎你每次插入某个值时都会索引数组中的每个元素。我们只需要在添加新等级时更改一个元素。 GPA类：

public class Gpa { 

    private int[] credits; 
    private String[] grades; 
    private int currentGrade; 

    public Gpa(int numGrades) { 
     credits = new int[numGrades]; 
     grades = new String[numGrades]; 
     currentGrade = 0; 
    } 

    public void addGrade(String letterGrade, int credit) { 
     grades[currentGrade] = letterGrade; 
     credits[currentGrade] = credit; 
     currentGrade = currentGrade + 1; 
    } 

    public double getGpa() { 
     double totalPoints = 0; 
     double totalWeight = 0; 

     for (int i = 0; i < currentGrade; i++) { 
      totalPoints = totalPoints + (letterToGpa(grades[i]) * credits[i]); 
      totalWeight = totalWeight + credits[i]; 
     } 

     return totalPoints/totalWeight; 
    } 

    private double letterToGpa(String letter) { 
     char first = letter.toUpperCase().charAt(0); 
     switch (first) { 
      case 'A': 
       return 4.0; 
      case 'B': 
       return 3.0; 
      case 'C': 
       return 2.0; 
      case 'D': 
       return 1.0; 
     } 
     return 0.0; 
    } 
} 

测试类应该可以正常工作现在：

public static void main(String[] args) { 
    Scanner in = new Scanner(System.in); //input object 
    int numCourses; //number of courses - can be changed 
    int credits;  //number of credits for a course 
    String grade;  //grade for course 

    //read in number of courses 
    System.out.print("Enter number of courses: "); 
    numCourses = in.nextInt(); 

    //create Gpa object to hold specified number of courses 
    Gpa t = new Gpa(numCourses); 

    //read in all courses and add course information to Gpa object 
    for (int k=0; k<numCourses; k++) 
    { 
     System.out.print("Enter credits for course " + (k+1) + ": "); 
     credits = in.nextInt(); 
     System.out.print("Enter grade for course " + (k+1) + ": "); 
     grade = in.next(); 

     t.addGrade(grade, credits); 
    } 

    //print results 
    System.out.println(); 
    System.out.printf("GPA is %4.2f%n", t.getGpa()); 
} 

只是要注意，这显然是不这样做的最好办法，也没有遵循面向对象模式非常好，但是OP的任务要求我们只使用一个类，等等。