为什么替换 ArrayList 中的文件内容会返回不需要的结果？

Question

如何将我编辑的文件行添加到我从 txt 文件中获取内容的同一行？

1,House mack,house,123 mack road,155,40000,40000,2022-09-29,no,Bill,123456,bill@gmail.com,12 Bill road,Jack,456789,jack@gmail.com,23 Jack road,John,789632,john@gmail.com,34 John road,
2,House John,house,123 John road,183,50000,50000,2022-09-10,yes,Bill,123456,bill@gmail.com,12 Bill road,Jack,456789,jack@gmail.com,23 Jack road,John,789632,john@gmail.com,34 John road,

但是我对 txt 文件的输出看起来像这样

1,House mack,house,123 mack road,155,40000,111,2022-09-29,no,Bill,123456,bill@gmail.com,12 Bill road,Jack,456789,jack@gmail.com,23 Jack road,John,789632,john@gmail.com,34 John road,

1,House mack,house,123 mack road,155,40000,111,2022-09-29,no,Bill,123456,bill@gmail.com,12 Bill road,Jack,456789,jack@gmail.com,23 Jack road,John,789632,john@gmail.com,34 John road,

如何让我的程序仅在已编辑的行中替换旧行，而不理会其他文件内容？

if (option.equals("cp")) {
    Array.set(values, 6, newPaid);
    findString = "\n" + values[0] + "," + values[1] + "," + values[2] + ","
        + values[3] + "," + values[4] + "," + values[5] + "," + values[6] + ","
        + values[7] + "," + values[8] + "," + values[9] + "," + values[10] + ","
        + values[11] + "," + values[12] + "," + values[13] + "," + values[14] + ","
        + values[15] + "," + values[16] + "," + values[17] + "," + values[18] + ","
        + values[19] + "," + values[20] + ",";
                                
    replaceLines(findString);
    System.out.println("Your Price has been changed and contents has been successfully updated! ");
    break;

我的方法包含所有计算

public static void replaceLines(String findString) {
    try {
        BufferedReader file = new BufferedReader(new FileReader("tasks.txt"));
        StringBuffer inputBuffer = new StringBuffer();
        String line;
    
        while ((line = file.readLine()) != null) {
            line = findString; 
            inputBuffer.append(line);
            inputBuffer.append('\n');
        }
        file.close();
    
        // write the new string with the replaced line OVER the same file
        FileOutputStream fileOut = new FileOutputStream("tasks.txt");
        fileOut.write(inputBuffer.toString().getBytes());
        fileOut.close();
    
    } catch (Exception e) {
        System.out.println("Problem reading file.");
    }
}

Answer 1

特定文件记录中普遍存在的某些内容已将您指向正确的（不同的）记录以执行价格更改，无论是 ID 号、名称、地址还是其他任何内容。你需要持有任何东西。大多数将使用不同的记录 ID 号，以便您仅更改该特定记录中的数据，否则您可能会更改文件中的多个记录。

在replaceLines() 方法中，findString 参数为要替换的文件和同一文件中的现有行保存一个新的（修改的）数据行。这里的问题是....替换什么线？您不会将该信息传递给您的方法。更改哪个人、地点或事物的价格？这显然需要在进行任何更改之前确定。例如，假设我们要更改 ID 为 1 的文件记录中的价格（在索引 6 处），对 replaceLines() 方法的调用应该是：

replaceLine( 1, findLines );

如果您指定记录、需要更改的列以及该特定列的新值可能是什么，则会更容易，例如：

updateRecord( 1, 6, "111" );

它可能是这样的：

public static void updateRecord(int recordID, int recordColumnIndex, String newValue) throws IOException {
    java.io.PrintWriter writer;
    try (java.io.BufferedReader reader = new java.io.BufferedReader(new java.io.FileReader("tasks.txt"))) {
        writer = new java.io.PrintWriter("temp.tmp");
        String line;
        // Read file line by line...
        while ((line = reader.readLine()) != null) {
            if (line.trim().isEmpty()) {
                writer.println(line);
                continue;
            }
            // Split each read line to separate data.
            String[] lineParts = line.split("\s*,\s*");
            
            /* If the record ID value matches the supplied ID value
               then make the desired changes to that line.    */
            if (Integer.parseInt(lineParts[0]) == recordID) {
                lineParts[recordColumnIndex] = newValue;
                // Rebuild the data line...
                StringBuilder sb = new StringBuilder(String.valueOf(recordID));
                for (int i = 1; i < lineParts.length; i++) {
                    sb.append(",").append(lineParts[i]);
                }
                line = sb.toString();
            }
            writer.println(line);  // write line to `temp.tmp` file.
            writer.flush();        // Immediate write.
        }
    }
    writer.close();

    /* Delete the `tasks.txt` file and then rename 
       `temp.tmp` to `tasks.txt`.            */
    if (new File("tasks.txt").delete()) {
        java.nio.file.Path source = java.nio.file.Paths.get("temp.tmp");
        java.nio.file.Files.move(source, source.resolveSibling("tasks.txt"));
    }

}

如果我正在查看最初来自 tasks.txt 文件的记录列表，我可以看到 ID 为1需要将第 7 列（索引 6）中的价格从 40000 更改为 111，然后我会调用：

try {
    updateRecord(1, 6, "111");
}
catch (IOException ex) {
    System.err.println(ex.getMessage());
}

一方面：

只是好奇，你为什么用换行符开始你的文件记录（ ) 字符，为什么你所有的记录都以逗号 (,) 结尾？