Question

我在此代码中遇到问题。我想要做的是读取一个文件并存储一个学生ID并将一个分数数组分成一个学生对象的分数属性，但我只有在打印时才能获得最后的分数。这是代码。你能告诉我，我的setter属性是否是在学生班级中分配数组的正确方法？问题是得分文件的最后一行存储在每个数组中，即使我调试它时我看到得分数组被传递，而且studentID数组工作正常。

import lab6.*;//importing the necessary classes

public class Main 
{
    public static void main(String[] args) 
    {
        Student lab6 [] = new Student[40];
        //Populate the student array
        lab6 = Util.readFile("studentScores.txt", lab6);    
        lab6[4].printStudent();         
    }

}

学生班------------------------------------

package lab6;

public class Student 
{
    private int SID;
    private int scores[] = new int[5];
      //write public get and set methods for SID and scores
    public int getSID()
    {
        return SID;
    }

    public void setSID(int SID)
    {
        this.SID = SID;
    }
    public int[] getScores()
    {
        return scores;
    }

    public void setScores(int scores[])
    {
        this.scores = scores;
    }
    //add methods to print values of instance variables.
     public void printStudent()
     { 
         System.out.print(SID);
         System.out.printf("\t");
         for(int i = 0; i < scores.length; i++)
         {
             System.out.printf("%d\t", scores[i]);
         }
     }
}


the util class --------------------------------------------------------------------

import java.io.*;
import java.util.StringTokenizer;

//Reads the file and builds student array.
//Open the file using FileReader Object.
//In a loop read a line using readLine method.
//Tokenize each line using StringTokenizer Object
//Each token is converted from String to Integer using parseInt method
//Value is then saved in the right property of Student Object.
public class Util 
{
    public static Student [] readFile(String filename, Student [] stu)
    {
        try {
            String line[] = new String[40];//one line of the file to be stored in here
            StringTokenizer stringToken;
            int studentID;//for storing the student id
            int[] studentScoreArray = new int[5];//for storing the student score

            FileReader file = new FileReader(filename);
            BufferedReader buff = new BufferedReader(file);

            boolean eof = false;
            int i = 0;
            buff.readLine();//used this to skip the first line
            while (!eof) //operation of one line
            { 
                line[i] = buff.readLine();
                if (line[i] == null)
                    eof = true;
                else //tokenize and store
                {
                    stringToken = new StringTokenizer(line[i]);
                    String tokenID = stringToken.nextToken().toString();//for storing the student id
                    studentID = Integer.parseInt(tokenID);
                    stu[i] = new Student();//creating student objects
                    stu[i].setSID(studentID);//stored in student object
                    //now storing the score-------------------------------------------------
                    int quizNumberCounter = 0;
                    while (stringToken.hasMoreTokens()) 
                    {
                        String tokens = stringToken.nextToken().toString();
                        studentScoreArray[quizNumberCounter] = Integer.parseInt(tokens);//converting and storing the scores in an array
                        quizNumberCounter++;//array progression

                    }
                    stu[i].setScores(studentScoreArray);//setting the score(passing it as an array)
                    //-----------------------------------------------------------------------

                }
                i++;

            }
            buff.close();
        } catch (IOException e) {
            System.out.println("Error -- " + e.toString());
        }

        return stu;
    }
/*
     StringTokenizer st = new StringTokenizer("this is a test");
     while (st.hasMoreTokens()) {
         System.out.println(st.nextToken());
     }
//How to convert a String to an Integer
    int x = Integer.parseInt(String) ;*/
}

示例文件结构-------------------------------------------- -----------

4532 011 017 081 032 077

Answer 1

问题在于

int[] studentScoreArray = new int[5];

你必须在学生循环中移动这个并为每个学生初始化数组。否则你会为所有学生重复使用相同的数组（即内存），并且你会一遍又一遍地覆盖分数。

// int[] studentScoreArray = new int[5]; // <= line removed here!!!

...

while (!eof) //operation of one line
{ 
    line[i] = buff.readLine();
    if (line[i] == null)
        eof = true;
    else //tokenize and store
    {
        int[] studentScoreArray = new int[5]; // <= line moved over to here!!!

        ...
    }
}

Answer 2

您可能只看到一行结果的一个原因是您只打印一行结果：

lab6[4].printStudent();

如果要查看所有结果，则需要将其更改为循环遍历数组：

foreach (Student student : lab6)
{
    student.printStudent();
}

另外，您的数组可能会被称为students而不是lab6。在java中使用Type[] identifier而不是Type identifier []来声明数组也是惯用的。

免责声明：可能还有其他错误，我没有阅读所有发布的数百行！

Answer 3

我没有根据我的建议测试代码，但请看一下：

int[] studentScoreArray = new int[5];

您只为整个文件创建一次和一次。一个简单而容易的解决方法就是为每个新行读取它。

像这样：

int[] studentScoreArray = new int[5];
int quizNumberCounter = 0;
while(..) { ...}

java数组传递，我不断到处都是最后一个数组

3 个答案: