Re: List of files with given extension in a directory

From:

"John B. Matthews" <nospam@nospam.invalid>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 22 Aug 2009 15:07:28 -0400

Message-ID:

<nospam-C9C0CD.15072722082009@news.aioe.org>

In article <nospam-160AB9.11552021082009@news.aioe.org>,
"John B. Matthews" <nospam@nospam.invalid> wrote:

[...]

This works for me:

public boolean accept(File dir, String name) {
return new File(dir + File.separator + name).isDirectory();
}

Alternatively, consider this implementation:

[...]

  public boolean accept(File dir, String name) {
    File[] list = dir.listFiles();
    for (File file : list) {
      if (file.getName().equals(name)) {
        return file.isDirectory();
      }
    }
    return false;
  }

Shamefully following up to my own post, I have considered the
implementation and found it wanting: the latter has O(n^2) worst-case
performance and is typically several time slower than the former. In
some ways, it is the bubble-sort [1] of directory filters.

Aware of the dangers of premature optimization, I cite this as an
example of precipitous degradation. I blame errant caffeine levels.

[1]<http://en.wikipedia.org/wiki/Bubble_sort>

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>