Iterate through all files in Java

Question

I want to make my program print huge list of all files that I have on my computer. My problem is that it only prints files from first folder of the first hard-drive, when I want it to print all files located on my computer. Any ideas what am I doing wrong here? Thanks.

Here is code I use:

Main:

import java.io.File; import java.util.ArrayList; import java.util.Arrays; public class Main { public static void main(String[] args) { ArrayList<File> roots = new ArrayList(); roots.addAll(Arrays.asList(File.listRoots())); for (File file : roots) { new Searcher(file.toString().replace('\\', '/')).search(); } } }

and Searcher class:

import java.io.File; public class Searcher { private String root; public Searcher(String root) { this.root = root; } public void search() { System.out.println(root); File folder = new File(root); File[] listOfFiles = folder.listFiles(); for (File file : listOfFiles) { String path = file.getPath().replace('\\', '/'); System.out.println(path); if (!path.contains(".")) { new Searcher(path + "/").search(); } } } }

Although there are duplicate questions (stackoverflow.com/questions/3154488/… and stackoverflow.com/questions/4917326/…), some answers are including Java 7, which was not available when the others were posted. — rajah9
– rajah9, Commented May 21, 2012 at 19:51

mprivat · Accepted Answer · 2012-05-21 19:19:19Z

I just tried this and it worked for me. I did have to add one null check and changed the directory evaluation method though:

package test; import java.io.File; import java.util.ArrayList; import java.util.Arrays; public class Searcher { public static void main(String[] args) { ArrayList<File> roots = new ArrayList<File>(); roots.addAll(Arrays.asList(File.listRoots())); for (File file : roots) { new Searcher(file.toString().replace('\\', '/')).search(); } } private String root; public Searcher(String root) { this.root = root; } public void search() { System.out.println(root); File folder = new File(root); File[] listOfFiles = folder.listFiles(); if(listOfFiles == null) return; // Added condition check for (File file : listOfFiles) { String path = file.getPath().replace('\\', '/'); System.out.println(path); if (file.isDirectory()) { new Searcher(path + "/").search(); } } } }

Hakan Serce · Accepted Answer · 2012-05-21 19:19:23Z

You should update your search method like this:

public void search() { System.out.println(root); File folder = new File(root); File[] listOfFiles = folder.listFiles(); for (File file : listOfFiles) { String path = file.getPath().replace('\\', '/'); System.out.println(path); if (file.isDirectory()) { new Searcher(path + "/").search(); } } }

Thorn G · Accepted Answer · 2012-05-21 19:19:36Z

If Java 7 is an option, look into the walkFileTree() method. It will allow you to visit all files and directories in a tree, which you can start from the root of your drive. Just implement a basic FileVisitor to process the file attributes for each Path. You can get started here.

you might want to update your first hyperlink... There is no walkFileTree() method on the Files page. And thank you for providing this Java 7 option.

Puce · Accepted Answer · 2012-05-21 19:20:18Z

If you're using Java SE 7, use the new file API:

http://docs.oracle.com/javase/7/docs/api/java/nio/file/FileVisitor.html

http://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#walkFileTree%28java.nio.file.Path,%20java.util.Set,%20int,%20java.nio.file.FileVisitor%29

http://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#walkFileTree%28java.nio.file.Path,%20java.nio.file.FileVisitor%29

SantoshK · Accepted Answer · 2012-05-21 19:34:38Z

I don't know what error you are getting but I got a NPE because you are not checking for the null after the following line.

File[] listOfFiles = folder.listFiles();

After changing the code as follows it seemed to run fine , I stopped it because I have a lot of files. I am assuming it will go on to the next root after the first root(c:/ in my case)

import java.io.File;

import java.util.ArrayList; import java.util.Arrays;

public class Search {

 public static void main(String[] args) { ArrayList<File> roots = new ArrayList(); roots.addAll(Arrays.asList(File.listRoots())); for (File file : roots) { System.out.println(file.toString()); new Searcher(file.toString().replace('\\', '/')).search(); } } }

class Searcher {

private String root; public Searcher(String root) { this.root = root; } public void search() { System.out.println(root); File folder = new File(root); File[] listOfFiles = folder.listFiles(); if(listOfFiles!=null) { for (File file : listOfFiles) { String path = file.getPath().replace('\\', '/'); System.out.println(path); if (!path.contains(".")) { new Searcher(path + "/").search(); } } } }

}

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