java - 使用 RandomAccessFile 在中间插入文本会删除一些文本

Question

我的示例代码

    String line = null;
    RandomAccessFile file = new RandomAccessFile("D:/mahtew.txt", "rw");
    System.out.println(file.getFilePointer());
    while((line = file.readLine()) != null){
        System.out.println(line);
        System.out.println(file.getFilePointer());

        if(line.contains("Text to be appended with")){
            file.seek(file.getFilePointer());
            file.write(" new text has been appended".getBytes());
            break;
        }
    }
    file.close();

执行前的demo.txt

one two three
Text to be appended with
five six seven
eight nine ten

执行后的demo.txt

one two three
Text to be appended with
 new text has been appendedten

我还尝试在附加新文本之前使用 setLength 更改文件长度。但是仍然有一些文本从输出文件中被删除。任何帮助将不胜感激

谢谢马修

Answer 1

RandomAccessFile

A random access file behaves like a large array of bytes stored in the file system.

实际上它并不关心在写操作的情况下移动数组元素(只有指针是先进的)。这样的操作会覆盖现有值:

Output operations write bytes starting at the file pointer and advance the file pointer past the bytes written.