从txt文件中删除一行java [英] Removing a line from a txt file java

问题描述

我有一个大文件，我只需要删除多行
有没有办法在不打开新文件的情况下执行此操作并复制整个文本？

I have a large file in which I need to remove only a number of lines Is there any way to do this without opening a new file and copy the whole text?

编辑：
主要问题是当它在多个带有大txt文件的线程中运行时程序失败

edit: the main problem is when it runs in more then one thread with large txt filse the program fails

推荐答案

如果没有打开新文件并复制整个文本，有没有办法做到这一点？

Is there any way to do this without opening a new file and copy the whole text?

不，没有。当然，如果你想安全地安装，就没有。

No there isn't. Certainly, there isn't if you want to do it safely.

和 RandomAccessFile 也不会真的帮助你。它允许您用相同数量的字节替换文件中的字节序列，但这并不等于删除一行。

And RandomAccessFile won't really help you either. It would allow you to replace a sequence of bytes in the file with an equal number of bytes, but that doesn't amount to deleting a line.

您可以使用这样的RAF：

You could use a RAF like this:

给定初始状态 L1L2L3 ... LN 替换 L2L3 ... LN 与 L3 ... LN

或者你可以使用RAF按照@ halfbit的答案一次滑动一行。

or you could use the RAF to "slide" the lines one at a time as per @halfbit's answer.

然而：

• 在最坏的情况下，你是在复制整个文件内容，平均情况涉及读取和写入 O（N）行的字节。

这样做的简单方法是在内存中保留 O（N）行。

The simple way of doing this requires holding O(N) lines in memory.

滑动方法需要 O（N） I / O操作（即系统调用）。

The "sliding" approach requires O(N) I/O operations (i.e. system calls).

最重要的是：通过就地文件更新删除行是有风险的。如果应用程序在进程中间被中断（例如电源故障），那么您将最终得到一个损坏的文件。

Most importantly: line deletion by in-place file update is risky. If the application is interrupted in the middle of the process (e.g. power failure), then you will end up with a corrupted file.

FWIW：这不是Java 本身的限制。相反，它限制了现代操作系统表示/模型文件的方式。

FWIW: this is not a limitation in Java per se. Rather it is a limitation of the way that modern operating systems represent / model files.

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