java - 如何在java中更新txt文件

Question

我有 JTable，可以在其中显示文本文件中的数据:

现在，为了删除我有这样的方法:

private void delete(ActionEvent evt) {
    DefaultTableModel model = (DefaultTableModel) tblRooms.getModel();
    // get selected row index
    try {
        int SelectedRowIndex = tblRooms.getSelectedRow();
        model.removeRow(SelectedRowIndex);
} catch (Exception ex) {
    JOptionPane.showMessageDialog(null, ex);
}

}

和 Action 监听器:

btnDelete.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                delete(e);
            }
        });

它将删除 JTable 中的行，没关系，但我的文本文件有 7 个分割，其中最后一个分割用于逻辑删除。因此，如果为 false - 房间不会被删除。

13|family room|name apartman|4|true|true|true|false
14|superior room|super room|2|true|false|false|false
15|room|room for one|1|false|false|true|false
0|MisteryRoom|Mistery|0|true|true|free|false

如何正确删除JTable中的某个房间，并由false改为true？

例如，如果我点击 super 房间，如何删除该房间。

Answer 1

出于多种原因，最好使用数据库而不是文本文件来处理此类事情，但由于您使用文本文件作为数据存储，因此我将演示一种替换值(子字符串)的方法)在特定的数据文本文件行中。

现在，以下方法可用于修改任何文件数据行上的任何字段数据......甚至是房间号，因此请记住这一点。您需要确保仅在最合适的情况下进行修改:

/**
 * Updates the supplied Room Number data within a data text file. Even the
 * Room Number can be modified.
 * 
 * @param filePath (String) The full path and file name of the Data File.
 * 
 * @param roomNumber (Integer - int) The room number to modify data for.
 * 
 * @param fieldToModify (Integer - int) The field number in the data line to 
 * apply a new value to. The value supplied here is to be considered 0 based 
 * meaning that 0 actually means column 1 (room number) within the file data 
 * line. A value of 7 would be considered column 8 (the deleted flag).
 * 
 * @param newFieldValue (String) Since the file is string based any new field 
 * value should be supplied as String. So to apply a boolean true you will need 
 * to supply "true" (in quotation marks) and to supply a new room number that 
 * room number must be supplied a String (ie: "666").
 * 
 * @return (Boolean) True if successful and false if not.
 */
public boolean updateRoomDataInFile(String filePath, int roomNumber,
        int fieldToModify, String newFieldValue) {
    // Try with resources so as to auto close the BufferedReader.
    try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
        String line;
        // Add the data file contents to a List interface...
        List<String> dataList = new ArrayList<>();
        while ((line = reader.readLine()) != null) {
            dataList.add(line);
        }

        for (int i = 0; i < dataList.size(); i++) {
            line = dataList.get(i).trim();  // Trim off any leading or trailing whitespaces (if any).
            // Skip Blank lines (if any) and skip Comment lines (if any).
            // In this example file comment lines start with a semicolon.
            if (line.equals("") || line.startsWith(";")) {
                continue;
            }
            //Split each read line so as to collect the desired room number
            // since everything will always be based from this unique ID number.
            // Split is done baesed on the Pipe (|) character since this is
            // what is implied with your data example.
            String[] roomData = line.split("\\|");
            // Get the current file data line room number.
            // Make sure the first piece of data is indeed a valid integer room 
            // number. We use the String.matches() method for this along with a 
            // regular expression.
            if (!roomData[0].trim().matches("\\d+")) {
                // If not then inform User and move on.
                JOptionPane.showMessageDialog(null, "Invalid room number detected on file line: "
                        + (i + 1), "Invalid Room Number", JOptionPane.WARNING_MESSAGE);
                continue;
            }
            // Convert the current data line room number to Integer 
            int roomNum = Integer.parseInt(roomData[0]);
            // Does the current data line room number equal the supplied 
            // room number?
            if (roomNum != roomNumber) {
                // If not then move on...
                continue;
            }

            // If we reach this point then we know that we are currently on 
            // the the data line we need and want to make changes to.
            String strg = "";  // Use for building a modified data line.
            // Iterate through the current data line fields
            for (int j = 0; j < roomData.length; j++) {
                // If we reach the supplied field number to modify
                // then we apply that modification to the field.
                if (j == fieldToModify) {
                    roomData[j] = newFieldValue;
                }
                // Build the new data line. We use a Ternary Operator, it is
                // basicaly the same as using a IF/ELSE.
                strg += strg.equals("") ? roomData[j] : "|" + roomData[j];
            }
            // Replace the current List element with the modified data.
            dataList.set(i, strg);
        }

        // Rewrite the Data File.
        // Try with resources so as to auto close the FileWriter.
        try (FileWriter writer = new FileWriter(filePath)) {
            // Iterate through the List and write it to the data file.
            // This ultimately overwrites the data file.
            for (int i = 0; i < dataList.size(); i++) {
                writer.write(dataList.get(i) + System.lineSeparator());
            }
        }
        // Since no exceptions have been caught at this point return true 
        // for success.
        return true;
    }
    catch (FileNotFoundException ex) {
        Logger.getLogger("updateFileRoomStatus()").log(Level.SEVERE, null, ex);
    }
    catch (IOException ex) {
        Logger.getLogger("updateFileRoomStatus()").log(Level.SEVERE, null, ex);
    }
    // We must of hit an exception if we got
    // here so return false for failure.
    return false;
}

要使用此方法，您可能需要这样做:

private void delete() {
    DefaultTableModel model = (DefaultTableModel) tblRooms.getModel();
    try {
        // get selected row index 
        int SelectedRowIndex = tblRooms.getSelectedRow();
        // Get out if nothing was selected but the button was.
        if (SelectedRowIndex == -1) { return; }
        int roomNumber = Integer.parseInt(model.getValueAt(SelectedRowIndex, 0).toString());
        updateRoomDataInFile("HotelRoomsData.txt", roomNumber, 7, "true");
        model.removeRow(SelectedRowIndex);
} catch (Exception ex) {
    JOptionPane.showMessageDialog(null, ex);
}

在上面的代码中，提供了数据文件名“HotelRoomsData.txt”。当然，这假设数据文件包含该名称并且位于特定项目的根文件夹(目录)内。如果文件的名称不同并且位于某个完全不同的位置，那么您需要将其更改为数据文件的完整路径和文件名，例如:

"C:/Users/Documents/MyDataFile.txt"

代码其实并没有那么长，只是附带了很多注释来解释事情。当然这些注释可以从代码中删除。