This tutorial describes how to print names of the files in a directory and all of its subdirectories.

Problem Statement

Print all the file names recrusively in a given directory.

Assumptions:

1. Files can be printed in any order.
2. Multi-threading needs to be utilized to make program faster on multi-core machines.

Solution

This problem can be easily solved using recursion as we can simply create a method to print file names in a directory and then call itself for every sibdirectory.

However since we need to use multi-threading, we will use ForkJoinPool executor service of Java.

Finally here is the program for printing file names in a directory recrusively -

package com.aksain.data.structures;

import java.io.File;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;
import java.util.concurrent.TimeUnit;

public class PrintingFilesRecursivelyInDirectory {
	
	private static class FilesPrinter extends RecursiveAction {
		private static final long serialVersionUID = 1L;
		private File directory;
		public FilesPrinter(File directory) {
			this.directory = directory;
		}
		
		@Override
		protected void compute() {
			for(File file : directory.listFiles()) {
				if(file.isDirectory()) {
					new FilesPrinter(file).fork();
				} else {
					System.out.println(file.getAbsolutePath());
				}
			}
		}
	}

	public static void main(String[] args) throws InterruptedException {
		final ForkJoinPool forkJoinPool = ForkJoinPool.commonPool();
		forkJoinPool.execute(new FilesPrinter(new File("C:\\Tutorials")));
		
		forkJoinPool.awaitTermination(10, TimeUnit.SECONDS);
	}
}

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