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From "Sebb (JIRA)" <>
Subject [jira] [Commented] (IO-355) IOUtils read() and skip() methods are performance hogs
Date Wed, 31 Oct 2012 20:27:12 GMT


Sebb commented on IO-355:

The API change is deliberate.

I've added Javadoc to note that the performance may not be as good as using skip.

I'm not sure that it is possible to fix the code without breaking the API and existing applications
that depend on the guaranteed skip behaviour that the methods provide.
> IOUtils read() and skip() methods are performance hogs
> ------------------------------------------------------
>                 Key: IO-355
>                 URL:
>             Project: Commons IO
>          Issue Type: Bug
>          Components: Utilities
>    Affects Versions: 2.3, 2.4
>            Reporter: Uli Bubenheimer
> IOUtils.skip(InputStream, long) and IOUtils.skip(Reader, long) have the worst possible
performance as they always use read() on the input instead of using skip(). In many cases,
using skip() from a subclass of InputStream is much faster than read(), as the skip() can
be implemented via a disk seek.
> The IOUtils.skip() methods are used in the read() methods of IOUtils and their similarly
named siblings, so they tend to bring down the performance of all reads that involve a skip.
> Case in point: I have observed this performance degradation with Java 7 on Windows 7.
A series of consecutive reads on a large file on disk that involved skips changed my performance
from 30 secs as my baseline to 10 minutes after starting to use

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