Question

我尝试做的是从.txt文件中添加数字并将其拆分;进入我的ArrayList listR2。截至目前，它是半工作的，但结果是只添加了最后2人的分数，第一个人得分只是为空。
我的分裂有问题吗？

我是如何让程序写出所有分数的？

Answer 1

您正在使用

跳过代码中的行（来自您的文件）

for (int i = 3; i < itemStudent.length; i++) {
    String test = studin.readLine(); //<--- this is the error
    listR2.add(test);
}

改为使用

    String test = itemStudent[i]; // to add the scores into the listR2

Answer 2

首先，您的代码：

BufferedReader studin = new BufferedReader(new FileReader(studentFile));
grader.Student student;
student = new Student();
String line, eNamn, fNamn, eMail;
ArrayList<String> listR = new ArrayList<String>();
ArrayList<String> listR2 = new ArrayList<String>();
//loop for the file and setters for first, lastname and email
while ((line = studin.readLine()) != null) {
    if (line.contains(";")) {
        //# you don't need regex to split on a single specific character
        String[] itemStudent = line.split("[;]");
        eNamn = itemStudent[0];
        fNamn = itemStudent[1];
        eMail = itemStudent[2];
        //#why are you using the Student object if you never use it in any way ?
        //#also you are always updating the same "Student". if you expect to add it to say an ArrayList, 
        //#you need to declare a new student at the beginning of the loop (not outside of it)
        student.setFirstName(fNamn);
        student.setLastName(eNamn);
        student.setEmail(eMail);

        //Loop for the sum of the tests
        Integer sum = 0; //# why Interger, the "int" primitive is more than sufficient
        for (int index = 3; index < itemStudent.length; index++) {
            try {
                sum += Integer.parseInt(itemStudent[index]);
                listR.add(itemStudent[index]);
            } catch (Exception ex) {} //very bad practice, nerver silently drop exceptions.
        }
        //# that part is just wrong in many ways, I guess it's some left over debug/testing code
        //# this also makes you skip lines as you will read as many lines as you have elements (minus 3) in itemStudent
        /*
        for (int i = 3; i < itemStudent.length; i++) {
            String test = studin.readLine();
            listR2.add(test);
        }
        */
        System.out.println(eNamn + " " + fNamn + " " + eMail + " SUMMA:" + sum + " " );
        //# you'll get a nice pointer address, but not it's values, you need to itterate the list to view it's content
        System.out.println(listR2);
    }
}

//＃标记我的评论这里有一个显示对象方法的快速示例：（可能包含拼写错误/缺少导入，但编译器应该没问题）。运行它： java Main“your_file”

import java.util.ArrayList;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class Main {
    public static void main(String[] args) {
        class Student{
            String fname;
            String lname;
            String mail;
            int sum;
            Student(String fn,String ln,String ml){
                fname=fn;
                lname=ln;
                mail=ml;
                sum=0;
            }
            void addScore(int n){
                sum += n;
            }
            public String toString() {
                return "Student: "+fname+" "+lname+", "+mail+" sum: "+sum;
            }
        }
        try {
            BufferedReader br = new BufferedReader(new FileReader(args[0]));
            ArrayList<Student> stdnts = new ArrayList<Student>();
            String line = br.readLine();
            while (line != null) {
                if (line.contains(";")) {
                    String[] stdnt_arr = line.split(";");
                    Student stdnt = new Student(stdnt_arr[0],stdnt_arr[1],stdnt_arr[2]);
                    for (int i = 3;i<stdnt_arr.length;i++){
                        try {
                            stdnt.addScore(Integer.parseInt(stdnt_arr[i]));
                        } catch (NumberFormatException e) {
                            //not a number
                            e.printStackTrace();
                        }
                    }
                    stdnts.add(stdnt);
                    System.out.println(stdnt.toString());
                }
                line = br.readLine();
            }
        } catch(IOException e){
            //things went wrong reading the file
            e.printStackTrace();
        }
    }
}

拆分arraylist和textfile

2 个答案: