我的Java代码不断向文本文件添加重复项

Question

我正在用Java编写一些代码，这些代码将能够为股票投资组合项目读取和写入文本文件。我可以读写，但当我尝试在同一个runner类中读两次文件时，它首先输出内容，然后输出两次内容，而不是两次输出相同的内容。

相关类别是(请原谅它们的长度(：

import java.util.ArrayList;
import java.io.*;
public class FileModifier {
    private String path;
    private int numOfLines;
    private ArrayList<String[]> arr;
    private BufferedReader br;
    private BufferedWriter bw;
    public FileModifier(String p){
        path = p;
        numOfLines = 0;
        arr = new ArrayList<String[]>();
    }
    public void read(){
        try{
            br = new BufferedReader(new FileReader(path));
            String line;
            while ((line = br.readLine()) != null) {
                String[] row = line.split("tt");
                arr.add(row);
                numOfLines++;
            }
            br.close();
        }
        catch(Exception e){
        }
    }
    public void write(){
        try{
            read();
            bw = new BufferedWriter(new FileWriter(path));
            String content = "";
            for (String[] line : arr) {
                for (int i = 0; i < line.length; i++) {
                    content += (line[i] + "tt");
                }
                content += "r";
            }
            bw.write(content);
            bw.close();
        }
        catch(Exception e){
        }
    }
    public ArrayList<String[]> getContents(){
        read();
        return arr;
    }
    public int getNumberOfLines(){
        read();
        return numOfLines;
    }
    public String[] getLine(int n){
        read();
        return arr.get(n);
    }
    public void addLine(int n, String[] newLine){
        read();
        arr.set(n, newLine);
    }
}

和

import java.util.ArrayList;
abstract public class Account {
    private FileModifier file;
    public Account(String historyPath){
        file = new FileModifier(historyPath);
    }
    abstract public double getBalance();
    public void addToHistory(String[] newLine){
        ArrayList<String[]> contents = file.getContents();
        contents.add(newLine);
        file.write();
    }
    public String getHistory(){
        String history = "";
        for(String[] line: file.getContents()){
            for(String part: line){
                history += part + "tt";
            }
            history += "n";
        }
        return history;
    }
}

和

import java.util.ArrayList;
import java.util.Date;
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
public class StockAccount extends Account{
    private ArrayList<String[]> arr;
    private DecimalFormat df;
    private SimpleDateFormat da;
    private int numOfShares;
    private double portfolioValue;
    private double balance;
    private FileModifier portfolio;
    public StockAccount(String p){
        super("C:\stock_transaction_history.txt");
        portfolio = new FileModifier(p);
        numOfShares = portfolio.getNumberOfLines();
        arr = portfolio.getContents();
        portfolioValue = 10000;
        balance = 10000;
        df = new DecimalFormat(".##");
        da = new SimpleDateFormat("HH:mm:ss");
    }
    public String displayPortfolio(){
        String output = "";
        String[] temp;
        for(int i = 0; i < numOfShares; i++){
            temp = arr.get(i);
            for(int k = 0; k < temp.length; k++){
                output += temp[k];
                output += "tt";
            }
            if(i < numOfShares - 1)
                output += "r";
        }
        return output;
    }
    public double getStockPrice(String symbol){
        for(String[] line: arr){
            if(line[0].equals(symbol))
                return Double.parseDouble(line[2]);
        }
        return -1;
    }
    public int getAmountOwned(String symbol){
        for(String[] line: arr){
            if(line[0].equals(symbol))
                return Integer.parseInt(line[1]);
        }
        return -1;
    }
    public double getStockValue(String symbol){
        int amt = getAmountOwned(symbol);
        double price = getStockPrice(symbol);
        if(amt == -1 || price == -1){
            return -1;
        }
        return amt * price;
    }
    public double getBalance(){
        double value = 0;
        for(int i = 0; i < arr.size()/2; i++){
            value += getStockValue(arr.get(i)[0]);
        }
        balance = Double.parseDouble(df.format(portfolioValue - value));
        return balance;
    }
}

现在，当我尝试做时

StockAccount sa = new StockAccount("C:\Result.txt");
System.out.println(sa.getHistory());
System.out.println();
System.out.println(sa.getHistory());

我得到

Event       Symbol      Owned       Price       Value       Time        
Buy     GOOG        10      $577.49     $5774.90        09:40:07        
Buy     MSFT        100     $30.00      $3000.00        13:37:00        

Event       Symbol      Owned       Price       Value       Time        
Buy     GOOG        10      $577.49     $5774.90        09:40:07        
Buy     MSFT        100     $30.00      $3000.00        13:37:00        
Event       Symbol      Owned       Price       Value       Time        
Buy     GOOG        10      $577.49     $5774.90        09:40:07        
Buy     MSFT        100     $30.00      $3000.00        13:37:00

我已经仔细阅读了我的代码，但我没有看到任何文件会重复。是不是有一些我不知道的关于文件阅读的东西？

Answer 1

此时应该使用调试器进入检测模式。为什么它恰好是两次的实际内容第二次time？内容存储在什么变量中？它何时附加到？你会不会两次那样做都是偶然的？故意地

仔细看看你是如何与FileModifier#arr交互的。

Answer 2

这与实现public void read()的方式有关。您的getHistory()调用file.getContents()，后者调用read((。Read为您的ArrayList<String[]> arr添加元素。则CCD_ 5返回CCD_。请注意，每次调用getHistory时，arr都将保持增长。如果你调用它一次，你就会得到预期的结果，但如果你多次调用它，你就会开始看到代码中的异常。

我不知道你在用什么工具，但这里有一个关于eclipse调试的好教程，或者如果你喜欢视频教程，那就自己动手吧。