How to read all files in a folder from Java?
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I agree, point out the class to use so the poster can become familiar with the various method, otherwise the poster doesn’t bother to read the API to find out what other methods are available.
If you are using Java 7 or newer you can use Files.walkFileTree , see stackoverflow.com/a/23814217/1115554
34 Answers 34
public void listFilesForFolder(final File folder) < for (final File fileEntry : folder.listFiles()) < if (fileEntry.isDirectory()) < listFilesForFolder(fileEntry); >else < System.out.println(fileEntry.getName()); >> > final File folder = new File("/home/you/Desktop"); listFilesForFolder(folder); Files.walk API is available from Java 8.
try (Stream paths = Files.walk(Paths.get("/home/you/Desktop"))) The example uses try-with-resources pattern recommended in API guide. It ensures that no matter circumstances the stream will be closed.
getName() will only give the name of the file in its directory, which could be a subdirectory of the original. If you plan to use this information to find the files, you may find the path given by getPath() to be more useful.
Can I use this method to find all files of a specific type say pdf or html across my whole system? My concern is efficiency, is it fast enough to be used for systems with thousands of files or is there a better alternative?
@codeln As of Java 8, the performance is very acceptable, you don’t notice anything laggy about it. It’s fast, efficient, and readable enough to get your job done.
In Java 8 you can also make use of the filter method. Then forEach is not longer needed. See here -> stackoverflow.com/a/26215931/1029251
File folder = new File("/Users/you/folder/"); File[] listOfFiles = folder.listFiles(); for (File file : listOfFiles) < if (file.isFile()) < System.out.println(file.getName()); >> @sam1370 Because this doesn’t read all files in the directory, it only gets the files directly inside the given directory. If the given directory itself contains other directories, their content won’t be read
In Java 8 you can do this
Files.walk(Paths.get("/path/to/folder")) .filter(Files::isRegularFile) .forEach(System.out::println); which will print all files in a folder while excluding all directories. If you need a list, the following will do:
Files.walk(Paths.get("/path/to/folder")) .filter(Files::isRegularFile) .collect(Collectors.toList()) If you want to return List instead of List just map it:
List filesInFolder = Files.walk(Paths.get("/path/to/folder")) .filter(Files::isRegularFile) .map(Path::toFile) .collect(Collectors.toList()); You also need to make sure to close the stream! Otherwise you might run into an exception telling you that too many files are open. Read here for more information.
Getting an error with .map(Path::toFile) Also .forEach(path -> System.out.println(path.toString()); should be .forEach(path -> System.out.println(path.toString()));
It says «Invalid method reference, cannot find symbol» «Method toFile» is toFile supposed to be something else?
Can u please paste your code in a PasteBin? Are you using java.nio.file.Path ? I just checked the method toFile() should exist even prior to java 8 -> docs.oracle.com/javase/7/docs/api/java/nio/file/…
@NadjibMami Please have a look here: razem.io/blog/posts/year2015/0819_try_catch_lambda Was to compilcated to answer in a comment. So I wrote a quick blog post.
If anyone is still looking for the try catch lambda topic the url of my blog has been changed -> razem.io/blog/y2015/0819_try_catch_lambda.html
All of the answers on this topic that make use of the new Java 8 functions are neglecting to close the stream. The example in the accepted answer should be:
try (Stream filePathStream=Files.walk(Paths.get("/home/you/Desktop"))) < filePathStream.forEach(filePath -> < if (Files.isRegularFile(filePath)) < System.out.println(filePath); >>); > From the javadoc of the Files.walk method:
The returned stream encapsulates one or more DirectoryStreams. If timely disposal of file system resources is required, the try-with-resources construct should be used to ensure that the stream’s close method is invoked after the stream operations are completed.
I mean the correct way is to use it in that way: Files.walk(Paths.get(«/home/you/Desktop»)).filter(Files::isRegularFile).forEach(filePath->. )
One remark according to get all files in the directory.
The method Files.walk(path) will return all files by walking the file tree rooted at the given started file.
For instance, there is the next file tree:
\---folder | file1.txt | file2.txt | \---subfolder file3.txt file4.txt Using the java.nio.file.Files.walk(Path) :
Files.walk(Paths.get("folder")) .filter(Files::isRegularFile) .forEach(System.out::println); Gives the following result:
folder\file1.txt folder\file2.txt folder\subfolder\file3.txt folder\subfolder\file4.txt To get all files only in the current directory use the java.nio.file.Files.list(Path) :
Files.list(Paths.get("folder")) .filter(Files::isRegularFile) .forEach(System.out::println); folder\file1.txt folder\file2.txt Upvote for the Files.list example. If you do not want to search recursively, this can be the best option sometimes.
what if i want to find, for example, amonst all the files, just the .pdf ones? how can I use the match function?
import java.io.File; public class ReadFilesFromFolder < public static File folder = new File("C:/Documents and Settings/My Documents/Downloads"); static String temp = ""; public static void main(String[] args) < // TODO Auto-generated method stub System.out.println("Reading files under the folder "+ folder.getAbsolutePath()); listFilesForFolder(folder); >public static void listFilesForFolder(final File folder) < for (final File fileEntry : folder.listFiles()) < if (fileEntry.isDirectory()) < // System.out.println("Reading files under the folder "+folder.getAbsolutePath()); listFilesForFolder(fileEntry); >else < if (fileEntry.isFile()) < temp = fileEntry.getName(); if ((temp.substring(temp.lastIndexOf('.') + 1, temp.length()).toLowerCase()).equals("txt")) System.out.println("File= " + folder.getAbsolutePath()+ "\\" + fileEntry.getName()); >> > > > Welcome to Stack Overflow! Rather than only post a block of code, please explain why this code solves the problem posed. Without an explanation, this is not an answer.
In Java 7 and higher you can use listdir
Path dir = . ; try (DirectoryStream stream = Files.newDirectoryStream(dir)) < for (Path file: stream) < System.out.println(file.getFileName()); >> catch (IOException | DirectoryIteratorException x) < // IOException can never be thrown by the iteration. // In this snippet, it can only be thrown by newDirectoryStream. System.err.println(x); >You can also create a filter that can then be passed into the newDirectoryStream method above
DirectoryStream.Filter filter = new DirectoryStream.Filter() < public boolean accept(Path file) throws IOException < try < return (Files.isRegularFile(path)); >catch (IOException x) < // Failed to determine if it's a file. System.err.println(x); return false; >> >; I’m confused by the create filter example. What is newDirectoryStream.Filter
I think i figured it out. its a copy and paste typo. there is a space between the «new» and the «DirectoryStream.Filter. «. If i’m right recommend correcting your example.
private static final String ROOT_FILE_PATH="/"; File f=new File(ROOT_FILE_PATH); File[] allSubFiles=f.listFiles(); for (File file : allSubFiles) < if(file.isDirectory()) < System.out.println(file.getAbsolutePath()+" is directory"); //Steps for directory >else < System.out.println(file.getAbsolutePath()+" is file"); //steps for files >> Just walk through all Files using Files.walkFileTree (Java 7)
Files.walkFileTree(Paths.get(dir), new SimpleFileVisitor() < @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException < System.out.println("file: " + file); return FileVisitResult.CONTINUE; >>); Note, that this code will throw an exception (and not report any further files) if for some file or directory the file attributes could not be read, e.g. because of permissions. Easy to reproduce on `C:`.
If you want more options, you can use this function which aims to populate an arraylist of files present in a folder. Options are : recursivility and pattern to match.
public static ArrayList listFilesForFolder(final File folder, final boolean recursivity, final String patternFileFilter) < // Inputs boolean filteredFile = false; // Ouput final ArrayListoutput = new ArrayList (); // Foreach elements for (final File fileEntry : folder.listFiles()) < // If this element is a directory, do it recursivly if (fileEntry.isDirectory()) < if (recursivity) < output.addAll(listFilesForFolder(fileEntry, recursivity, patternFileFilter)); >> else < // If there is no pattern, the file is correct if (patternFileFilter.length() == 0) < filteredFile = true; >// Otherwise we need to filter by pattern else < filteredFile = Pattern.matches(patternFileFilter, fileEntry.getName()); >// If the file has a name which match with the pattern, then add it to the list if (filteredFile) < output.add(fileEntry); >> > return output; > File directory = new File("/user/folder"); File[] myarray; myarray=new File[10]; myarray=directory.listFiles(); for (int j = 0; j < myarray.length; j++) < File path=myarray[j]; FileReader fr = new FileReader(path); BufferedReader br = new BufferedReader(fr); String s = ""; while (br.ready()) < s += br.readLine() + "\n"; >> You might want to add an explanation what you are trying to achieve, instead of only showing code. Furthermore, myarray=new File[10]; is not required, as it will be overwritten by the next line!
File fl = new File(dir); File[] files = fl.listFiles(new FileFilter() < public boolean accept(File file) < return file.isFile(); >>); docs.oracle.com/javase/7/docs/api/java/io/… public File[] listFiles() Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname.
static File mainFolder = new File("Folder"); public static void main(String[] args) < lf.getFiles(lf.mainFolder); >public void getFiles(File f) < File files[]; if (f.isFile()) < String name=f.getName(); >else < files = f.listFiles(); for (int i = 0; i < files.length; i++) < getFiles(files[i]); >> > I think this is good way to read all the files in a folder and sub folder’s
private static void addfiles (File input,ArrayList files) < if(input.isDirectory()) < ArrayList path = new ArrayList(Arrays.asList(input.listFiles())); for(int i=0 ; i if(path.get(i).isFile()) < files.add(path.get(i)); >> > if(input.isFile()) < files.add(input); >> Simple example that works with Java 1.7 to recursively list files in directories specified on the command-line:
import java.io.File; public class List < public static void main(String[] args) < for (String f : args) < listDir(f); >> private static void listDir(String dir) < File f = new File(dir); File[] list = f.listFiles(); if (list == null) < return; >for (File entry : list) < System.out.println(entry.getName()); if (entry.isDirectory()) < listDir(entry.getAbsolutePath()); >> > > While I do agree with Rich, Orian and the rest for using:
final File keysFileFolder = new File(); File[] fileslist = keysFileFolder.listFiles(); if(fileslist != null) < //Do your thing here. > for some reason all the examples here uses absolute path (i.e. all the way from root, or, say, drive letter (C:\) for windows..)
I’d like to add that it is possible to use relative path as-well. So, if you’re pwd (current directory/folder) is folder1 and you want to parse folder1/subfolder, you simply write (in the code above instead of ):
final File keysFileFolder = new File("subfolder"); Here is a safe solution , not though so elegant as Java 8 Files.walk(..) :
int[] count = ; try < Files.walkFileTree(Paths.get(dir.getPath()), new HashSet(Arrays.asList(FileVisitOption.FOLLOW_LINKS)), Integer.MAX_VALUE, new SimpleFileVisitor() < @Override public FileVisitResult visitFile(Path file , BasicFileAttributes attrs) throws IOException < System.out.printf("Visiting file %s\n", file); ++count[0]; return FileVisitResult.CONTINUE; >@Override public FileVisitResult visitFileFailed(Path file , IOException e) throws IOException < System.err.printf("Visiting failed for %s\n", file); return FileVisitResult.SKIP_SUBTREE; >@Override public FileVisitResult preVisitDirectory(Path dir , BasicFileAttributes attrs) throws IOException < System.out.printf("About to visit directory %s\n", dir); return FileVisitResult.CONTINUE; >>); > catch (IOException e) < // TODO Auto-generated catch block e.printStackTrace(); >package com; import java.io.File; /** * * @author ?Mukesh */ public class ListFiles < static File mainFolder = new File("D:\\Movies"); public static void main(String[] args) < ListFiles lf = new ListFiles(); lf.getFiles(lf.mainFolder); long fileSize = mainFolder.length(); System.out.println("mainFolder size in bytes is: " + fileSize); System.out.println("File size in KB is : " + (double)fileSize/1024); System.out.println("File size in MB is :" + (double)fileSize/(1024*1024)); >public void getFiles(File f) < File files[]; if(f.isFile()) System.out.println(f.getAbsolutePath()); else< files = f.listFiles(); for (int i = 0; i < files.length; i++) < getFiles(files[i]); >> > > Just to expand on the accepted answer I store the filenames to an ArrayList (instead of just dumping them to System.out.println) I created a helper class «MyFileUtils» so it could be imported by other projects:
class MyFileUtils < public static void loadFilesForFolder(final File folder, ListfileList) < for (final File fileEntry : folder.listFiles()) < if (fileEntry.isDirectory()) < loadFilesForFolder(fileEntry, fileList); >else < fileList.add( fileEntry.getParent() + File.separator + fileEntry.getName() ); >> > > I added the full path to the file name. You would use it like this:
import MyFileUtils; List fileList = new ArrayList(); final File folder = new File("/home/you/Desktop"); MyFileUtils.loadFilesForFolder(folder, fileList); // Dump file list values for (String fileName : fileList) The ArrayList is passed by «value», but the value is used to point to the same ArrayList object living in the JVM Heap. In this way, each recursion call adds filenames to the same ArrayList (we are NOT creating a new ArrayList on each recursive call).
There are many good answers above, here’s a different approach: In a maven project, everything you put in the resources folder is copied by default in the target/classes folder. To see what is available at runtime
ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader(); URL resource = contextClassLoader.getResource(""); File file = new File(resource.toURI()); File[] files = file.listFiles(); for (File f : files) Now to get the files from a specific folder, let’s say you have a folder called ‘res’ in your resources folder, just replace:
URL resource = contextClassLoader.getResource("res"); If you want to have access in your com.companyName package then:
contextClassLoader.getResource("com.companyName"); A one liner using .map to get all the filenames in yourDirectory :
List files = Files.list(Paths.get(yourDirectory)).map(path -> path.getFileName().toFile().getName()).collect(Collectors.toList());
You can put the file path to argument and create a list with all the filepaths and not put it the list manually. Then use a for loop and a reader. Example for txt files:
public static void main(String[] args) throws IOException < File[] files = new File(args[0].replace("\\", "\\\\")).listFiles(new FilenameFilter() < @Override public boolean accept(File dir, String name) < return name.endsWith(".txt"); >>); ArrayList filedir = new ArrayList(); String FILE_TEST = null; for (i=0; i>> package com.commandline.folder; import java.io.File; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; import java.util.stream.Stream; public class FolderReadingDemo < public static void main(String[] args) < String str = args[0]; final File folder = new File(str); // listFilesForFolder(folder); listFilesForFolder(str); >public static void listFilesForFolder(String str) < try (Streampaths = Files.walk(Paths.get(str))) < paths.filter(Files::isRegularFile).forEach(System.out::println); >catch (Exception e) < e.printStackTrace(); >> public static void listFilesForFolder(final File folder) < for (final File fileEntry : folder.listFiles()) < if (fileEntry.isDirectory()) < listFilesForFolder(fileEntry); >else < System.out.println(fileEntry.getName()); >> > > We can use org.apache.commons.io.FileUtils, use listFiles() mehtod to read all the files in a given folder.
FileUtils.listFiles(directory, new String[] , true) This read all the files in the given directory with given extensions, we can pass multiple extensions in the array and read recursively within the folder(true parameter).
public static List files(String dirname) < if (dirname == null) < return Collections.emptyList(); >File dir = new File(dirname); if (!dir.exists()) < return Collections.emptyList(); >if (!dir.isDirectory()) < return Collections.singletonList(file(dirname)); >return Arrays.stream(Objects.requireNonNull(dir.listFiles())) .collect(Collectors.toList()); > import java.io.File; import java.util.ArrayList; import java.util.List; public class AvoidNullExp < public static void main(String[] args) < ListfileList =new ArrayList<>(); final File folder = new File("g:/master"); new AvoidNullExp().listFilesForFolder(folder, fileList); > public void listFilesForFolder(final File folder,List fileList) < File[] filesInFolder = folder.listFiles(); if (filesInFolder != null) < for (final File fileEntry : filesInFolder) < if (fileEntry.isDirectory()) < System.out.println("DIR : "+fileEntry.getName()); listFilesForFolder(fileEntry,fileList); >else < System.out.println("FILE : "+fileEntry.getName()); fileList.add(fileEntry); >> > > > list down files from Test folder present inside class path
import java.io.File; import java.io.IOException; public class Hello < public static void main(final String[] args) throws IOException < System.out.println("List down all the files present on the server directory"); File file1 = new File("/prog/FileTest/src/Test"); File[] files = file1.listFiles(); if (null != files) < for (int fileIntList = 0; fileIntList < files.length; fileIntList++) < String ss = files[fileIntList].toString(); if (null != ss && ss.length() >0) < System.out.println("File: " + (fileIntList + 1) + " :" + ss.substring(ss.lastIndexOf("\\") + 1, ss.length())); >> > > > /** * Function to read all mp3 files from sdcard and store the details in an * ArrayList */ public ArrayList> getPlayList() < ArrayList> songsList=new ArrayList<>(); File home = new File(MEDIA_PATH); if (home.listFiles(new FileExtensionFilter()).length > 0) < for (File file : home.listFiles(new FileExtensionFilter())) < HashMapsong = new HashMap(); song.put( "songTitle", file.getName().substring(0, (file.getName().length() - 4))); song.put("songPath", file.getPath()); // Adding each song to SongList songsList.add(song); > > // return songs list array return songsList; > /** * Class to filter files which have a .mp3 extension * */ class FileExtensionFilter implements FilenameFilter < @Override public boolean accept(File dir, String name) < return (name.endsWith(".mp3") || name.endsWith(".MP3")); >> You can filter any textfiles or any other extension ..just replace it with .MP3