通过Java将文本插入到现有文件中 [英] Inserting text into an existing file via Java

问题描述

我想创建一个简单的程序（在Java中）编辑文本文件 - 特别是在文本文件中随机位置插入任意文本的文本文件。这个功能是我目前正在编写的一个更大的程序的一部分。

I would like to create a simple program (in Java) which edits text files - particularly one which performs inserting arbitrary pieces of text at random positions in a text file. This feature is part of a larger program I am currently writing.

阅读有关java.util.RandomAccessFile的描述，似乎在文件实际上会覆盖现有的内容。这是一个副作用，我想避免（如果可能的话）。

Reading the description about java.util.RandomAccessFile, it appears that any write operations performed in the middle of a file would actually overwrite the exiting content. This is a side-effect which I would like to avoid (if possible).

有没有一个简单的方法来实现这一点？

Is there a simple way to achieve this?

提前感谢

推荐答案

好的，这个问题很旧，但是FileChannels存在于Java 1.4和我不知道为什么在处理在文件中替换或插入内容的问题时，它们没有被提及。 FileChannels 很快，使用它们。

Okay, this question is pretty old, but FileChannels exist since Java 1.4 and I don't know why they aren't mentioned anywhere when dealing with the problem of replacing or inserting content in files. FileChannels are fast, use them.

这是一个例子（忽略异常和其他一些东西）：

Here's an example (ignoring exceptions and some other stuff):

public void insert(String filename, long offset, byte[] content) {
  RandomAccessFile r = new RandomAccessFile(new File(filename), "rw");
  RandomAccessFile rtemp = new RandomAccessFile(new File(filename + "~"), "rw");
  long fileSize = r.length();
  FileChannel sourceChannel = r.getChannel();
  FileChannel targetChannel = rtemp.getChannel();
  sourceChannel.transferTo(offset, (fileSize - offset), targetChannel);
  sourceChannel.truncate(offset);
  r.seek(offset);
  r.write(content);
  long newOffset = r.getFilePointer();
  targetChannel.position(0L);
  sourceChannel.transferFrom(targetChannel, newOffset, (fileSize - offset));
  sourceChannel.close();
  targetChannel.close();
}

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