Java替换文本文件中的行

• Z时代
• 2024-01-10
• 分类：问答

如何替换在文本文件中找到的一行文本？

我有一个字符串，例如：

Do the dishes0

我想用更新它：

Do the dishes1

（反之亦然）

我该如何完成？

ActionListener al = new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    JCheckBox checkbox = (JCheckBox) e.getSource();
                    if (checkbox.isSelected()) {
                        System.out.println("Selected");
                        String s = checkbox.getText();
                        replaceSelected(s, "1");
                    } else {
                        System.out.println("Deselected");
                        String s = checkbox.getText();
                        replaceSelected(s, "0");
                    }
                }
            };
public static void replaceSelected(String replaceWith, String type) {
}

顺便说一句，我只想替换已读取的行。不是整个文件。

回答：

在底部，我有一个通用的解决方案来替换文件中的行。但是首先，这是眼前特定问题的答案。辅助功能：

public static void replaceSelected(String replaceWith, String type) {
    try {
        // input the file content to the StringBuffer "input"
        BufferedReader file = new BufferedReader(new FileReader("notes.txt"));
        StringBuffer inputBuffer = new StringBuffer();
        String line;
        while ((line = file.readLine()) != null) {
            inputBuffer.append(line);
            inputBuffer.append('\n');
        }
        file.close();
        String inputStr = inputBuffer.toString();
        System.out.println(inputStr); // display the original file for debugging
        // logic to replace lines in the string (could use regex here to be generic)
        if (type.equals("0")) {
            inputStr = inputStr.replace(replaceWith + "1", replaceWith + "0"); 
        } else if (type.equals("1")) {
            inputStr = inputStr.replace(replaceWith + "0", replaceWith + "1");
        }
        // display the new file for debugging
        System.out.println("----------------------------------\n" + inputStr);
        // write the new string with the replaced line OVER the same file
        FileOutputStream fileOut = new FileOutputStream("notes.txt");
        fileOut.write(inputStr.getBytes());
        fileOut.close();
    } catch (Exception e) {
        System.out.println("Problem reading file.");
    }
}

然后调用它：

public static void main(String[] args) {
    replaceSelected("Do the dishes", "1");   
}

原始文本文件内容：

Do the dishes0

Feed the dog0

Cleaned my room1

Output:

Do the dishes0

Feed the dog0

Cleaned my room1

Do the dishes1

Feed the dog0

Cleaned my room1

New text file content:

Do the dishes1

Feed the dog0

Cleaned my room1

And as a note, if the text file was:

Do the dishes1

Feed the dog0

Cleaned my room1并且你使用了方法replaceSelected(“Do the dishes”, “1”);，它将不会更改文件。

由于这个问题非常具体，因此我将在此处为将来的读者添加一个更通用的解决方案（基于标题）。

// read file one line at a time
// replace line as you read the file and store updated lines in StringBuffer
// overwrite the file with the new lines
public static void replaceLines() {
    try {
        // input the (modified) file content to the StringBuffer "input"
        BufferedReader file = new BufferedReader(new FileReader("notes.txt"));
        StringBuffer inputBuffer = new StringBuffer();
        String line;
        while ((line = file.readLine()) != null) {
            line = ... // replace the line here
            inputBuffer.append(line);
            inputBuffer.append('\n');
        }
        file.close();
        // write the new string with the replaced line OVER the same file
        FileOutputStream fileOut = new FileOutputStream("notes.txt");
        fileOut.write(inputBuffer.toString().getBytes());
        fileOut.close();
    } catch (Exception e) {
        System.out.println("Problem reading file.");
    }
}

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