快速阅读文本文件的最后一行？ [英] Quickly read the last line of a text file?

问题描述

解决方案

从Java中的[非常大的]文件中读取最后一行文本是最快最有效的方法>

看看我对类似C＃的问题。代码将非常相似，尽管编码支持在Java中有所不同。

基本上，这不是一件非常简单的事情。正如MSalter指出的那样，UTF-8确实可以轻松地将 \r 或 \\\
作为UTF这些字符的-8表示与ASCII相同，这些字节不会发生在多字节字符中。

所以基本上，要缓冲（说）2K，并逐渐向后读（跳到2K之前，之前，读下一个2K）检查线终止。然后跳到正确的流中的正确位置，在顶部创建一个 InputStreamReader ，另外还有一个 BufferedReader 那。然后调用 BufferedReader.readLine（）。

What's the quickest and most efficient way of reading the last line of text from a [very, very large] file in Java?

解决方案

Have a look at my answer to a similar question for C#. The code would be quite similar, although the encoding support is somewhat different in Java.

Basically it's not a terribly easy thing to do in general. As MSalter points out, UTF-8 does make it easy to spot \r or \n as the UTF-8 representation of those characters is just the same as ASCII, and those bytes won't occur in multi-byte character.

So basically, take a buffer of (say) 2K, and progressively read backwards (skip to 2K before you were before, read the next 2K) checking for a line termination. Then skip to exactly the right place in the stream, create an InputStreamReader on the top, and a BufferedReader on top of that. Then just call BufferedReader.readLine().

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