使用BufferedReader / PrintWriter时产生Null输出

Question

似乎我也无法读取文件。

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package daos;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import model.City;
import model.YearData;

import repositories.Repository;

/**
 *
 * @author mga
 */
public class DAOTextImpl implements DAOInterface {

    static final char DELIMITER = ',';
    ArrayList yeardata=new ArrayList<>();

    @Override
    public Repository load(String filename) {

        Repository repository = new Repository();

        try (BufferedReader br = new BufferedReader(new FileReader(filename))) {

            String[] temp;
            String line = br.readLine();
            while (line != null) {

                temp = line.split(Character.toString(DELIMITER));
                int id = Integer.parseInt(temp[0]);
                String cityName = stripQuotes(temp[1]);
                String country = stripQuotes(temp[2]);


                int noOfLines = Integer.parseInt(temp[2]);
               // for (int i = 0; i < noOfLines; i++) 
              //  {
                    line = br.readLine();
                    temp = line.split(Character.toString(DELIMITER));
                    String year = stripQuotes(temp[0]);
                    float precipitation = Float.parseFloat(temp[1]);
                    int maxTemp = Integer.parseInt(temp[2]);
                    int minTemp = Integer.parseInt(temp[3]);
                    int windSpeed = Integer.parseInt(temp[4]);
                    String windDirection = stripQuotes(temp[5]);
                    yeardata.add(year);
                    yeardata.add(precipitation);
                    yeardata.add(maxTemp);
                    yeardata.add(minTemp);
                    yeardata.add(windSpeed);
                    yeardata.add(windDirection);
                    City city=new City(id,cityName,country,yeardata);

              //  }
                repository.add(city);
                line = br.readLine();
            }
            br.close();
        } catch (IOException ex) {
            Logger.getLogger(DAOTextImpl.class.getName()).log(Level.SEVERE, null, ex);
        }
        return repository;
    }

    @Override




    public void store(String filename, Repository repository) {
        try (PrintWriter output = new PrintWriter(filename)) {
         output.print(repository.toString());
         output.print(repository);


            output.close();
        } catch (FileNotFoundException ex) {
            Logger.getLogger(DAOTextImpl.class.getName()).log(Level.SEVERE, null, ex);
        }        
    }

    private String stripQuotes(String str) {
        return str.substring(1, str.length() - 1);
    }
}

我的存储库类如下：

package repositories;

import daos.DAOTextImpl;
import java.util.ArrayList;
import java.util.function.Predicate;
import model.City;
import model.YearData;


public class Repository implements RepositoryInterface {
    private ArrayList<City> items; 
     static char DELIMITER=',';

    public Repository() {
        this.items = new ArrayList<>();

    }

    public Repository(ArrayList <City> items) {        
        this.items = items;
    }

    public Repository(String filename) {
        this();
        // Create dao and execute load  
        DAOTextImpl dao = new DAOTextImpl();
    }

    @Override
    public ArrayList<City> getItems() {        
        return this.items;
    }

    @Override
    public void setItems(ArrayList<City> items) {        
        this.items = items;
    }

    @Override
    public void add(City items) {

        this.items.add(items);

    }

    @Override
    public void remove(int id) {
        Predicate<City> predicate = e->e.getId() == id;       
        this.items.removeIf(predicate);
    }

   @Override
    public City getItem(int id) {

        for (City item:this.items) {
            if (item.getId() == id)
                return item;
        }
        return null;
    }

    @Override
    public String toString() {
           System.out.println(items);

        return "\nItems: " + this.items;

    }    

    @Override
    public void store(String filename) {       
        // create dao and execute store    
        DAOTextImpl dao = new DAOTextImpl();
        dao.store(filename, this); 
    }        


}

我已经对该程序进行了压力测试，并在其中插入了多个output.print(repository.toString());语句。例如，插入20条output.print(repository.toString());语句将插入生成的文件20 items:[]中，这会使我认为Repository类/接口内有错误，但我终生都会我完全不确定这是为什么/为什么产生的。

我不确定当前似乎没有与文件正确读取有关的事实，还是一个错误只是掩盖了另一个错误。

由于我不确定导致问题的原因，我觉得我需要包括完整的代码长度，如果只是为了便于进行错误检查的话。