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(用 Java)来编辑文本文件 - 特别是一个在文本文件中的随机位置插入任意文本片段的程序.此功能是我目前正在编写的更大程序的一部分.

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，似乎在文件中间执行的任何写操作实际上都会覆盖现有内容.这是我想避免的副作用(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).

有没有简单的方法来实现这一目标?

Is there a simple way to achieve this?

提前致谢.

推荐答案

好吧，这个问题很老了，但是 FileChannels 从 Java 1.4 开始就存在了，我不知道为什么在处理替换或插入文件中的内容.FileChannels 速度很快，请使用它们.

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();
}

这篇关于通过 Java 将文本插入到现有文件中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！