How can I modify a specific line of a file in Java?

In Java, you can use the RandomAccessFile class to modify a specific line of a file. The specific steps are as follows:

1. Create a RandomAccessFile object, specifying the file path and open mode (for example, read and write mode: “rw”).
2. Use the seek() method to position the file pointer at the beginning of the line you want to modify. The position can be calculated by adding up the lengths of each line.
3. Use the write() method to write new content to the file.
4. Close the RandomAccessFile object.

Here is a sample code:

import java.io.RandomAccessFile;

public class ModifyFileLine {
    public static void main(String[] args) {
        String filePath = "path/to/file.txt";
        int lineNumberToModify = 3;
        String newContent = "New line content";

        try {
            RandomAccessFile file = new RandomAccessFile(filePath, "rw");

            // 定位到要修改的行的起始位置
            long position = 0;
            for (int i = 1; i < lineNumberToModify; i++) {
                position += file.readLine().length() + 1; // 1 表示换行符的长度
            }
            file.seek(position);

            // 写入新的内容
            file.write(newContent.getBytes());

            file.close();
            System.out.println("文件内容修改成功。");
        } catch (Exception e) {
            System.out.println("文件内容修改失败：" + e.getMessage());
        }
    }
}

Please note that this method is only suitable for text files. Modifying the content of binary files (such as images, audio, video, etc.) may result in file corruption.