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Java---题库管理系统项目中的Dao类

2023-02-23 60
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简介： Java---题库管理系统项目中的Dao类

说明

在该项目中entity建了四个实体分别是

1.Collection实体

2.User实体

3.Note实体

4.Qestions实体

Dao包只用了缓冲流与文件进行交互

代码

接口

// ICollectionDao
import studio.lyl.questionbankmanagementsystem.entity.Collection;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/7 17:32
 */
public interface ICollectionDao {
    /**
     * 添加到收藏
     * @param collection
     * @return boolean
     */
    boolean insetCollection(Collection collection);
    /**
     *根据用户id删除收藏夹
     * @param id
     * @return boolean
     */
    boolean deleteCollection(Integer id) throws Exception;
    /**
     * 根据用户id更改收藏
     * @param id
     * @param collection
     * @return
     */
    boolean updateCollection(Integer id,Collection collection) throws Exception;
    /**
     * 根据用户id查看收藏夹
     * @param id
     * @return List
     */
    List<Collection> selectCollectionById(Integer id) throws Exception;
    /**
     *查看所有的收藏
     * @return List
     */
    List<Collection> selectCollection() throws Exception;
}
// INoteDao
import studio.lyl.questionbankmanagementsystem.entity.Note;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/7 18:13
 */
public interface INoteDao {
    /**
     * 增加笔记
     * @param note
     * @return boolean
     */
    boolean insetNote(Note note) throws Exception;
    /**
     * 根据用户id删除笔记
     * @param id
     * @return boolean
     */
    boolean deleteNote(Integer id) throws Exception;
    /**
     * 根据用户id更改笔记
     * @param id
     * @param note
     * @return
     */
    boolean updateNote(Integer id,Note note) throws Exception;
    /**
     * 根据用户id查看笔记
     * @param id
     * @return
     */
    List<Note> selectNoteById(Integer id) throws Exception;
    /**
     * 查看所有的笔记
     * @return
     */
    List<Note> selectNote() throws Exception;
}
// IQuestionDao
import studio.lyl.questionbankmanagementsystem.entity.Questions;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/7 17:15
 */
public interface IQuestionDao{
    /**
     * 增加题目
     * @param questions
     * @return boolean
     */
    boolean insetQuestion(Questions questions) throws Exception;
    /**
     * 根据序号删除题目
     * @param sign
     * @param type
     * @return boolean
     */
    boolean deleteQuestion(int sign,String type) throws Exception;
    /**
     * 根据序号删除题目
     * @param sign
     * @param questions
     * @param type
     * @return
     */
    boolean updateQuestion(int sign ,String type ,Questions questions) throws Exception;
    /**
     * 根据序号查看题目
     * @param sign
     * @param type
     * @return String
     */
    List<Questions> selectQuestion(int sign, String type) throws Exception;
    /**
     * 查看一个类型里所有的题目
     * @param type
     * @return List
     * @throws Exception
     */
    List<Questions> selectQuestions(String type) throws Exception;
}
// IUserDao
import studio.lyl.questionbankmanagementsystem.entity.User;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/7 16:23
 */
public interface IUserDao {
    /**
     * 创建用户
     * @param user
     * @return boolean
     */
    boolean insertUser(User user) throws Exception;
    /**
     * 根据id删除用户
     * @param id
     * @return boolean
     */
    boolean deleteUserById(Integer id) throws  Exception;
    /**
     * 修改用户信息
     * @param id
     * @return boolean
     */
    boolean updateUser(Integer id,User user) throws Exception;
    /**
     * 根据id查看用户信息
     * @param id
     * @return List
     */
    List<User> selectUserById(Integer id) throws Exception;
    /**
     * 查看所有用户信息
     * @return
     * @throws Exception
     */
    List<User> selectUser() throws Exception;
}

实现

// CollectionDaoImpl implements ICollectionDao
import studio.lyl.questionbankmanagementsystem.dao.ICollectionDao;
import studio.lyl.questionbankmanagementsystem.entity.Collection;
import java.io.*;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/7 19:36
 */
public class CollectionDaoImpl implements ICollectionDao {
    @Override
    public boolean insetCollection(Collection collection) {
        try {
            BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\Collections.txt",true));
            bufferedWriter.write( collection.getTime()+","+collection.getId()+"," + collection.getUserName() + ","+ collection.getCount()+"," + collection.getSign());
            bufferedWriter.newLine();
            bufferedWriter.flush();
            bufferedWriter.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return false;
    }
    @Override
    public boolean deleteCollection(Integer id) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Collections.txt"));
        List<Collection> collectionList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Collection collection=new Collection(strings[0],Integer.parseInt(strings[1]),strings[2],Integer.parseInt(strings[3]),Integer.parseInt(strings[4]));
            collectionList.add(collection);
        }
        for (int i = 0; i < collectionList.size(); i++) {
            Collection collection = collectionList.get(i);
            if (collection.getId().equals(id)) {
                collectionList.remove(i);
            }
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\Collections.txt"));
        for (int j = 0; j < collectionList.size(); j++) {
            Collection collection=collectionList.get(j);
            String returnFile=String.format("%s,%s,%s,%s,%s",collection.getTime(),collection.getId(),collection.getUserName(),collection.getCount(),collection.getSign());
            bufferedWriter.write(returnFile);
            bufferedWriter.newLine();
            bufferedWriter.flush();
        }
        bufferedReader.close();
        bufferedWriter.close();
        return false;
    }
    @Override
    public boolean updateCollection(Integer id, Collection collection) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Collections.txt"));
        List<Collection> collectionList=new ArrayList<>();
        String s=null;
        while((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Collection returnCollection = new Collection(strings[0],Integer.parseInt(strings[1]),strings[2],Integer.parseInt(strings[3]),Integer.parseInt(strings[4]));
            collectionList.add(returnCollection);
        }
        for (int i = 0; i < collectionList.size(); i++) {
            Collection returnCollection=collectionList.get(i);
            if(returnCollection.getId().equals(id)){
                collectionList.set(i,collection);
            }
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\Collections.txt"));
        for (int i = 0; i < collectionList.size(); i++) {
            Collection returnCollection = collectionList.get(i);
            String returnString = String.format("%s,%s,%s,%s,%s",returnCollection.getTime(),returnCollection.getId(),returnCollection.getUserName(),returnCollection.getCount(),returnCollection.getSign());
            bufferedWriter.write(returnString);
            bufferedWriter.newLine();
            bufferedWriter.flush();
        }
        bufferedReader.close();
        bufferedWriter.close();
        return false;
    }
    @Override
    public List<Collection> selectCollectionById(Integer id) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Collections.txt"));
        List<Collection> collectionList=new ArrayList<>();
        String s=null;
        while((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Collection returnCollection = new Collection(strings[0],Integer.parseInt(strings[1]),strings[2],Integer.parseInt(strings[3]),Integer.parseInt(strings[4]));
            collectionList.add(returnCollection);
        }
        for (int i = 0; i < collectionList.size(); i++) {
            Collection collection=collectionList.get(i);
            if(collection.getId().equals(id)){
                System.out.println(collection.toString());
            }
        }
        return null;
    }
    @Override
    public List<Collection> selectCollection() throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Collections.txt"));
        List<Collection> collectionList=new ArrayList<>();
        String s=null;
        while((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Collection returnCollection = new Collection(strings[0],Integer.parseInt(strings[1]),strings[2],Integer.parseInt(strings[3]),Integer.parseInt(strings[4]));
            collectionList.add(returnCollection);
        }
        for (int i = 0; i < collectionList.size(); i++) {
            Collection collection=collectionList.get(i);
            System.out.println(collection.toString());
        }
        return null;
    }
}
// NoteDaoImpl implements INoteDao
import studio.lyl.questionbankmanagementsystem.dao.INoteDao;
import studio.lyl.questionbankmanagementsystem.entity.Note;
import java.io.*;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/8 8:37
 */
public class NoteDaoImpl implements INoteDao {
    @Override
    public boolean insetNote(Note note) throws Exception{
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\Note.txt",true));
        bufferedWriter.write(note.getMaster()+","+note.getId()+","+note.getCount()+","+note.getSign()+","+note.getContent());
        bufferedWriter.newLine();
        bufferedWriter.flush();
        bufferedWriter.close();
        return false;
    }
    @Override
    public boolean deleteNote(Integer id) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Note.txt"));
        List<Note> noteList=new ArrayList<>();
        String s;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Note note=new Note(strings[0],Integer.parseInt(strings[1]),Integer.parseInt(strings[2]),Integer.parseInt(strings[3]),strings[4]);
            System.out.println(note);
            noteList.add(note);
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\Note.txt"));
        for (int i = 0; i < noteList.size(); i++) {
            Note note=noteList.get(i);
            if(note.getId().equals(id)){
                noteList.remove(i);
            }
        }
        for (int i = 0; i < noteList.size(); i++) {
            Note note=noteList.get(i);
            String returnString=String.format("%s,%s,%s,%s,%s",note.getMaster(),note.getId(),note.getCount(),note.getSign(),note.getContent());
            bufferedWriter.write(returnString);
        }
        bufferedReader.close();
        bufferedWriter.flush();
        bufferedWriter.close();
        return false;
    }
    @Override
    public boolean updateNote(Integer id, Note note) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Note.txt"));
        List<Note> noteList=new ArrayList<>();
        String s;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Note noteGet=new Note(strings[0],Integer.parseInt(strings[1]),Integer.parseInt(strings[2]),Integer.parseInt(strings[3]),strings[4]);
            System.out.println(noteGet);
            noteList.add(noteGet);
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\Note.txt"));
        for (int i = 0; i < noteList.size(); i++) {
            Note noteSet=noteList.get(i);
            if(noteSet.getId().equals(id)) {
                noteList.add(note.getSign(), note);
            }
        }
        for (int i = 0; i < noteList.size(); i++) {
            Note returnNote=noteList.get(i);
            String returnString=String.format("%s,%s,%s,%s,%s",returnNote.getMaster(),returnNote.getId(),returnNote.getCount(),returnNote.getSign(),returnNote.getContent());
            bufferedWriter.write(returnString);
        }
        bufferedReader.close();
        bufferedWriter.flush();
        bufferedWriter.close();
        return false;
    }
    @Override
    public List<Note> selectNoteById(Integer id) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Note.txt"));
        List<Note> noteList=new ArrayList<>();
        String s;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Note note=new Note(strings[0],Integer.parseInt(strings[1]),Integer.parseInt(strings[2]),Integer.parseInt(strings[3]),strings[4]);
            noteList.add(note);
        }
        for (int i = 0; i < noteList.size(); i++) {
            Note note=noteList.get(i);
            if(note.getId().equals(id)){
                System.out.println(note);
            }
        }
        bufferedReader.close();
        return null;
    }
    @Override
    public List<Note> selectNote() throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\Note.txt"));
        List<Note> noteList=new ArrayList<>();
        String s;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Note note=new Note(strings[0],Integer.parseInt(strings[1]),Integer.parseInt(strings[2]),Integer.parseInt(strings[3]),strings[4]);
            noteList.add(note);
        }
        for (int i = 0; i < noteList.size(); i++) {
            Note note=noteList.get(i);
                System.out.println(note);
        }
        return null;
    }
}
// QuestionDaoImpl implements IQuestionDao
import studio.lyl.questionbankmanagementsystem.dao.IQuestionDao;
import studio.lyl.questionbankmanagementsystem.entity.Questions;
import java.io.*;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/8 20:18
 */
public class QuestionDaoImpl implements IQuestionDao {
    @Override
    public boolean insetQuestion(Questions questions) throws Exception{
    //这里不想把路径写死就做了如下处理
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(("QuestionBankManagementSystem\\Questions\\".endsWith("/") ? "QuestionBankManagementSystem\\Questions\\":"QuestionBankManagementSystem\\Questions\\"+"/")+questions.getType()+".txt",true));
        bufferedWriter.write(questions.getContent()+","+questions.getType()+","+questions.getSign()+","+questions.getComplexity()+","+questions.getAnswer());
        bufferedWriter.newLine();
        bufferedWriter.flush();
        bufferedWriter.close();
        return false;
    }
    @Override
    public boolean deleteQuestion(int sign,String type) throws Exception {
        BufferedReader bufferedReader=new BufferedReader(new FileReader(("QuestionBankManagementSystem\\Questions\\".endsWith("/") ? "QuestionBankManagementSystem\\Questions\\":"QuestionBankManagementSystem\\Questions\\"+"/")+type+".txt"));
        List<Questions> questionsList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Questions questions=new Questions(strings[0],strings[1],Integer.parseInt(strings[2]),strings[3],strings[4]);
            questionsList.add(questions);
        }
        for (int i = 0; i < questionsList.size(); i++) {
            Questions questions=questionsList.get(i);
            if(questions.getSign()==sign){
                questionsList.remove(i);
            }
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(("QuestionBankManagementSystem\\Questions\\".endsWith("/") ? "QuestionBankManagementSystem\\Questions\\":"QuestionBankManagementSystem\\Questions\\"+"/")+type+".txt"));
        for (int i = 0; i < questionsList.size(); i++) {
            Questions questions=questionsList.get(i);
            String returnString=String.format("%s,%s,%s,%s,%s",questions.getContent(),questions.getType(),questions.getSign(),questions.getComplexity(),questions.getAnswer());
            bufferedWriter.write(returnString);
            bufferedWriter.newLine();
        }
        bufferedReader.close();
        bufferedWriter.flush();
        bufferedWriter.close();
        return false;
    }
    @Override
    public boolean updateQuestion(int sign,String type,Questions questions) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader(("QuestionBankManagementSystem\\Questions\\".endsWith("/") ? "QuestionBankManagementSystem\\Questions\\":"QuestionBankManagementSystem\\Questions\\"+"/")+type+".txt"));
        List<Questions> questionsList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Questions questionsSet=new Questions(strings[0],strings[1],Integer.parseInt(strings[2]),strings[3],strings[4]);
            questionsList.add(questionsSet);
        }
        for (int i = 0; i < questionsList.size(); i++) {
            Questions questionsSet=questionsList.get(i);
            if(questionsSet.getSign()==sign){
                questionsList.set(i,questions);
            }
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(("QuestionBankManagementSystem\\Questions\\".endsWith("/") ? "QuestionBankManagementSystem\\Questions\\":"QuestionBankManagementSystem\\Questions\\"+"/")+type+".txt"));
        for (int i = 0; i < questionsList.size(); i++) {
            Questions questionsSet=questionsList.get(i);
            String returnString=String.format("%s,%s,%s,%s,%s",questionsSet.getContent(),questionsSet.getType(),questionsSet.getSign(),questionsSet.getComplexity(),questionsSet.getAnswer());
            bufferedWriter.write(returnString);
            bufferedWriter.newLine();
        }
        bufferedReader.close();
        bufferedWriter.flush();
        bufferedWriter.close();
        return false;
    }
    @Override
    public List<Questions> selectQuestion(int sign,String type) throws Exception {
        BufferedReader bufferedReader=new BufferedReader(new FileReader(("QuestionBankManagementSystem\\Questions\\".endsWith("/") ? "QuestionBankManagementSystem\\Questions\\":"QuestionBankManagementSystem\\Questions\\"+"/")+type+".txt"));
        List<Questions> questionsList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Questions questions=new Questions(strings[0],strings[1],Integer.parseInt(strings[2]),strings[3],strings[4]);
            questionsList.add(questions);
        }
        for (int i = 0; i < questionsList.size(); i++) {
            Questions questions=questionsList.get(i);
            if(questions.getSign()==sign){
                System.out.println(questions.getContent());
            }
        }
        return null;
    }
    @Override
    public List<Questions> selectQuestions(String type) throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader(("QuestionBankManagementSystem\\Questions\\".endsWith("/") ? "QuestionBankManagementSystem\\Questions\\":"QuestionBankManagementSystem\\Questions\\"+"/")+type+".txt"));
        List<Questions> questionsList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            Questions questions=new Questions(strings[0],strings[1],Integer.parseInt(strings[2]),strings[3],strings[4]);
            questionsList.add(questions);
        }
        for (int i = 0; i < questionsList.size(); i++) {
            Questions questions=questionsList.get(i);
            System.out.println(questions.getContent());
        }
        return null;
    }
}
// UserDaoImpl implements IUserDao 
import studio.lyl.questionbankmanagementsystem.dao.IUserDao;
import studio.lyl.questionbankmanagementsystem.entity.User;
import java.io.*;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: Re
 * @Date: 2020/12/8 22:12
 */
public class UserDaoImpl implements IUserDao {
    @Override
    public boolean insertUser(User user) throws Exception {
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\User.txt"));
        List<User> userList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            User userGet=new User(Integer.parseInt(strings[0]),strings[1],strings[2]);
            userList.add(userGet);
        }
        for (int i = 0; i < userList.size(); i++) {
            User userGet=userList.get(i);
            if(userGet.getId()==user.getId()){
                System.out.println("用户已存在，请重新输入");
            }else {
                userList.add(user);
            }
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\User.txt",true));
        for (int i = 0; i < userList.size(); i++) {
            User userGet=userList.get(i);
            String returnString=String.format("%s,%s,%s",userGet.getId(),userGet.getPassword(),userGet.getUserName());
            bufferedWriter.write(returnString);
            bufferedWriter.newLine();
        }
        bufferedReader.close();
        bufferedWriter.flush();
        bufferedReader.close();
        return false;
    }
    @Override
    public boolean deleteUserById(Integer id) throws Exception {
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\User.txt"));
        List<User> userList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            User user=new User(Integer.parseInt(strings[0]),strings[1],strings[2]);
            userList.add(user);
        }
        for (int i = 0; i < userList.size(); i++) {
            User userGet=userList.get(i);
            if(userGet.getId()==id) {
                userList.remove(i);
            }
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\User.txt"));
        for (int i = 0; i < userList.size(); i++) {
            User user=userList.get(i);
            String returnString=String.format("%s,%s,%s",user.getId(),user.getPassword(),user.getUserName());
            bufferedWriter.write(returnString);
            bufferedWriter.newLine();
        }
        bufferedReader.close();
        bufferedWriter.flush();
        bufferedReader.close();
        return false;
    }
    @Override
    public boolean updateUser(Integer id,User user) throws Exception {
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\User.txt"));
        List<User> userList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            User userGet=new User(Integer.parseInt(strings[0]),strings[1],strings[2]);
            userList.add(userGet);
        }
        for (int i = 0; i < userList.size(); i++) {
            User userGet=userList.get(i);
            if(userGet.getId()==id) {
                userList.set(i,user);
            }
        }
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter("QuestionBankManagementSystem\\User.txt"));
        for (int i = 0; i < userList.size(); i++) {
            User userGet=userList.get(i);
            String returnString=String.format("%s,%s,%s",userGet.getId(),userGet.getPassword(),userGet.getUserName());
            bufferedWriter.write(returnString);
            bufferedWriter.newLine();
        }
        bufferedReader.close();
        bufferedWriter.flush();
        bufferedReader.close();
        return false;
    }
    @Override
    public List<User> selectUserById(Integer id) throws Exception {
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\User.txt"));
        List<User> userList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            User user=new User(Integer.parseInt(strings[0]),strings[1],strings[2]);
            userList.add(user);
        }
        for (int i = 0; i < userList.size(); i++) {
            User user=userList.get(i);
            if(user.getId()==id){
                System.out.println(user);
            }
        }
        return null;
    }
    @Override
    public List<User> selectUser() throws Exception{
        BufferedReader bufferedReader=new BufferedReader(new FileReader("QuestionBankManagementSystem\\User.txt"));
        List<User> userList=new ArrayList<>();
        String s=null;
        while ((s=bufferedReader.readLine())!=null){
            String[] strings=s.split(",");
            User user=new User(Integer.parseInt(strings[0]),strings[1],strings[2]);
            userList.add(user);
        }
        for (int i = 0; i < userList.size(); i++) {
            User user=userList.get(i);
            System.out.println(user);
        }
        return null;
    }
}


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