Question

我有一个学校项目，我在编码部分遇到了一些问题我希望在我输入的文件中有一种数据库。文件中的文本我想要添加到ArrayList中，之后我想添加一个新成员。添加新成员后，我希望将其添加到ArrayList并显示在输出文件中。

这是主要的：

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

public class Main {


    public static List<Member> membersList = new ArrayList<>();

    public static readFile file = new readFile();
    public static writeFile write = new writeFile();

    public static void main(String[] args) throws FileNotFoundException, IOException
    {
        Main call = new Main();
        int choice;
        Scanner in = new Scanner(System.in);
        do {
            System.out.println("\n<<<< CLUB CHAIRMAN >>>>\n");

            System.out.println("1-Display members list");
            System.out.println("2-Modify a member");
            System.out.println("3-Add member");
            System.out.println("0-Exit");
            System.out.println("\n Select: ");
            choice = in.nextInt();
            in.nextLine();
            if(choice == 1)
            {
                file.openFile();
                file.readFile(membersList);
                file.closeFile();
            }
            if(choice == 2)
            {
                write.writer();
            }

            if(choice == 3)
            {
                call.addNewMember();
            }
        }while(choice != 0);
    }
    private void addNewMember() {
        int numberOfMembers;
        Scanner in = new Scanner(System.in);
        System.out.println("How many members do you want to add?");
        numberOfMembers = in.nextInt();
        in.nextLine();
        String[][] newMember = new String[numberOfMembers][4];

        for (int i = 0; i < numberOfMembers; i++)
        {
            System.out.println("\nEnter details for member " + (i + 1) + ":");
            System.out.println("Name:");
            newMember[i][0] = in.nextLine();
            System.out.println("Age:");
            newMember[i][1] = in.nextLine();
            System.out.println("Gender:");
            newMember[i][2] = in.nextLine();
            System.out.println("Experience(elite swimmer/swimming for the exercise:");
            newMember[i][3] = in.nextLine();
            System.out.println("Membership Type(passive/active):");
            newMember[i][4] = in.nextLine();

        }
        for(int i = 0; i < newMember.length; i++)
        {
            membersList.add(new Member( newMember[i][0], Integer.parseInt( newMember[i][1]),  newMember[i][2],  newMember[i][3],newMember[i][4]));
        }
        System.out.println("\nThe action completed successfully");



    }
}


class Member
{

    private String name;
    private int age;
    private String gender;
    private String experience;
    private String membershipType;

    Member(String name, int age, String gender, String experience, String membershipType)
    {
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.experience = experience;
        this.membershipType = membershipType;
    }

}

填充新成员的部分后出现此错误：线程中的异常＆＃34; main＆＃34; java.lang.ArrayIndexOutOfBoundsException：4 在Main.addNewMember（Main.java:64）在Main.main（Main.java:40）

读取文件类：

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

public class readFile {

    private Scanner x ;

    public void openFile() throws FileNotFoundException {
        try {
            x = new Scanner(new File("D:\\Trial Exam\\USE CASE 1\\src\\members"));
        } catch (Exception e) {
            System.out.println("Couldn't find file");
        }
    }

    public void readFile(List<Member> list) throws FileNotFoundException {
        String fileName = "D:\\Trial Exam\\USE CASE 1\\src\\members";
        String line = null;
        Scanner x = new Scanner(new File(fileName));

        try {

            FileReader fileReader = new FileReader(fileName);

            BufferedReader bufferedReader = new BufferedReader(fileReader);

            while ((line = bufferedReader.readLine()) != null) {

                String a = x.next();
                String b = x.next();
                String c = x.next();
                String d = x.next();
                String e = x.next();
                list.add(new Member(a,Integer.parseInt(b),c,d,e));
                System.out.println(line);
            }

            bufferedReader.close();
        } catch (FileNotFoundException ex) {
            System.out.println(
                    "Unable to open file '" + fileName + "'");
        } catch (IOException ex) {
            System.out.println(
                    "Error reading file '" + fileName + "'");

        }

    }
    public void closeFile() {
        x.close();
    }

}

写文件类：

 import java.io.*;

public class writeFile {
    private static String fileName = "D:\\Trial Exam\\USE CASE 1\\src\\output";

    public void writer() throws IOException {

        Main call = new Main();
        PrintWriter pw = null;
        FileOutputStream fo = null;
        File file = null;
        try {
            file = new File("D:\\Trial Exam\\USE CASE 1\\src\\output");
            pw = new PrintWriter(new FileOutputStream(file));
            fo = new FileOutputStream(file);
            int memberList = call.membersList.size();
            for (int i = 0; i < memberList; i++) {
                pw.write(call.membersList.get(i).toString() + "\n");
            }
        } finally {
            pw.flush();
            pw.close();
            fo.close();
        }
    }
}

这是成员输入文件：会员1 27男初中被动会员2名28名女性高级活跃会员3 32女高级被动

Answer 1

您可以定义数组4的大小，因此您可以访问最大索引3。

 //Array's second dimension size is 4
 //you can access max index 3
//Example  numberOfMembers[i][3]
 String[][] newMember = new String[numberOfMembers][4];

在此行中，您访问索引4，因此您将获得ArrayIndexOutOfBoundsException。

 for (int i = 0; i < numberOfMembers; i++)
 {
      ....
     //you can access max index  newMember[i][3], not 4
     newMember[i][4] = in.nextLine();

 }

使用ArrayList Java输入和输出文件

1 个答案: