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Is there a workaround for Java's poor performance on walking huge directories?

I created a utility which lists all the files within some directory by using File.listFiles() function, but the problem occurred when i copied huge amount of files (around 100K) under that directory.

I was looking for some solution take actually takes some fixed no of files (say X) from that directory and processes and then deletes those files and takes next X number of files.
Can any one please suggest me any solution.

Regards

Answer 1

One solution could be to use a FileNameFilter that either returns false after a certain number of files have been accepted or, if you are prepared to abuse Exceptions a little, throw an Exception at that point.

class CountedFilter implements FilenameFilter {
  int limit = 0;

  public CountedFilter ( int limit ) {
    this.limit = limit;
  }

  public boolean accept(File file, String string) {
    return limit-- > 0;
  }

}

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There is another option which is nowhere near as succinct but I believe is more effective. It involves a FilenameFilter that posts each file back to the caller through a BlockingQueue. The File.list is called in a separate thread so you don’t have to wait for it to complete.

This solution has the added benefit that the files can be processed while File.list is running producing a much smoother solution, much like an iterator. If encouraged I will post the code as a separate answer.