How to read all files in a folder from Java

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How to read all the files in a folder through Java

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This will Read Specified file extension files in given path looks sub folders also   public static Map lt String List lt File gt  gt  getFileNames String  dirName Map lt String List lt File gt  gt  filesContainer final String fileExt       String dirPath   dirName      List lt File gt files   new ArrayList lt  gt         Map lt String List lt File gt  gt  completeFiles   filesContainer       if completeFiles    null            completeFiles   new HashMap lt  gt               File file   new File dirName        FileFilter fileFilter   new FileFilter              Override         public boolean accept File file                boolean acceptFile   false              if file isDirectory                      acceptFile   true               else if  file getName   toLowerCase   endsWith fileExt                                   acceptFile   true                              return acceptFile                       for File dirfile   file listFiles fileFilter             if dirfile isFile    amp  amp   dirfile getName   toLowerCase   endsWith fileExt                 files add dirfile            else if dirfile isDirectory                  if  files isEmpty                      completeFiles put dirPath  files                    getFileNames dirfile getAbsolutePath   completeFiles fileExt                       if  files isEmpty              completeFiles put dirPath  files               return completeFiles

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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 lt File gt  files        if input isDirectory                  ArrayList  lt File gt  path   new ArrayList lt File gt  Arrays asList input listFiles              for int i 0   i lt path size     i                        if path get i  isDirectory                                  addfiles path get i  files                             if path get i  isFile                                  files add path get i                                      if input isFile                  files add input

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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 lt File gt  instead of List lt Path gt  just map it   List lt File gt  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

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to prevent Nullpointerexceptions on the listFiles   function and recursivly get all files from subdirectories too     public void listFilesForFolder final File folder List lt File gt  fileList        File   filesInFolder   folder listFiles        if  filesInFolder    null            for  final File fileEntry   filesInFolder                if  fileEntry isDirectory                  listFilesForFolder fileEntry fileList             else               fileList add fileEntry                               List lt File gt  fileList   new List lt File gt      final File folder   new File   home you Desktop     listFilesForFolder folder

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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 lt String gt  filedir   new ArrayList lt String gt         String FILE TEST   null      for  i 0  i lt files length  i                 filedir add files i  toString                 CSV FILE TEST filedir get i            try Reader testreader   Files newBufferedReader Paths get FILE TEST                                   write your stuff

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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

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Function to read all mp3 files from sdcard and store the details in an    ArrayList       public ArrayList lt HashMap lt String  String gt  gt  getPlayList                  ArrayList lt HashMap lt String  String gt  gt  songsList new ArrayList lt  gt             File home   new File MEDIA PATH            if  home listFiles new FileExtensionFilter    length  gt  0                for  File file   home listFiles new FileExtensionFilter                       HashMap lt String  String gt  song   new HashMap lt String  String gt                     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

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nice usage of java io FileFilter as seen on https   stackoverflow com a 286001 146745  File fl   new File dir   File   files   fl listFiles new FileFilter                   public boolean accept File file            return file isFile

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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  lt  files length  i                       getFiles files i

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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 lt Path gt  paths   Files walk Paths get   home you Desktop           paths          filter Files  isRegularFile           forEach System out  println        The example uses try-with-resources pattern recommended in API guide  It ensures that no matter circumstances the stream will be closed

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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  lt  files length  i                      getFiles files i

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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

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import java io File  import java util ArrayList  import java util List   public class AvoidNullExp    public static void main String   args         List lt File gt  fileList  new ArrayList lt  gt          final File folder   new File  g  master         new AvoidNullExp   listFilesForFolder folder  fileList          public void listFilesForFolder final File folder List lt File gt  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

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void getFiles            String dirPath    E  folder name           File dir   new File dirPath           String   files   dir list            if  files length    0                System out println  The directory is empty              else               for  String aFile   files                    System out println aFile

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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            System out println f getName             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

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In Java 7 and higher you can use listdir  Path dir        try  DirectoryStream lt Path gt  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 lt Path gt  filter   new DirectoryStream Filter lt Path gt          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                       For other filtering examples   see documentation   http   docs oracle com javase tutorial essential io dirs html glob

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Java 8 Files walk     is good when you are soore it will not throw Avoid Java 8 Files walk     termination cause of   java nio file AccessDeniedException      Here is a safe solution   not though so elegant as Java 8Files walk        int   count    0   try       Files walkFileTree Paths get dir getPath     new HashSet lt FileVisitOption gt  Arrays asList FileVisitOption FOLLOW LINKS                Integer MAX VALUE  new SimpleFileVisitor lt Path gt                       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

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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     Result   folder file1 txt folder file2 txt

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import java io File    public class Test    public void test1         System out println  TEST 1       public static void main String   args  throws SecurityException  ClassNotFoundException       File actual   new File  src        File list     actual listFiles        for int i 0  i lt list length  i             String substring   list i  getName   substring 0  list i  getName   indexOf                if list i  isFile    amp  amp  list i  getName   contains   java                     if Class forName substring  getMethods   0  getName   contains  main                         System out println  CLASS NAME   Class forName substring  getName                                                Just pass your folder it will tell you main class about the method

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While I do agree with Rich  Orian and the rest for using       final File keysFileFolder   new File  lt path gt         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

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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  lt  files length  fileIntList                      String ss   files fileIntList  toString                    if  null    ss  amp  amp  ss length    gt  0                        System out println  File       fileIntList   1           ss substring ss lastIndexOf         1  ss length

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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

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Just walk through all Files using Files walkFileTree  Java 7   Files walkFileTree Paths get dir   new SimpleFileVisitor lt Path gt           Override     public FileVisitResult visitFile Path file  BasicFileAttributes attrs  throws IOException           System out println  file      file           return FileVisitResult CONTINUE

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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  List lt String gt  fileList           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 lt String gt  fileList   new ArrayList lt String gt     final File folder   new File   home you Desktop    MyFileUtils loadFilesForFolder folder  fileList       Dump file list values for  String fileName   fileList       System out println fileName       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

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File directory   new File   user folder          File   myarray    myarray new File 10   myarray directory listFiles    for  int j   0  j  lt  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

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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 lt File gt  listFilesForFolder final File folder          final boolean recursivity          final String patternFileFilter            Inputs     boolean filteredFile   false          Ouput     final ArrayList lt File gt  output   new ArrayList lt File gt              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      Best  Adrien

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This will work fine   private static void addfiles File inputValVal  ArrayList lt File gt  files      if inputVal isDirectory            ArrayList  lt File gt  path   new ArrayList lt File gt  Arrays asList inputVal listFiles           for int i 0  i lt path size      i                if path get i  isDirectory                          addfiles path get i  files                     if path get i  isFile                          files add path get i                              Optional   if you need to have the counts of all the folders and files you can create 2 global arrays          and store the results of the above 2 if loops inside these arrays             if inputVal isFile              files add inputVal

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We can use org apache commons io FileUtils  use listFiles   mehtod to read all the files in a given folder  eg  FileUtils listFiles directory    quot array of extension quot    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

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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 lt Path gt  filePathStream Files walk Paths get   home you Desktop           filePathStream forEach filePath - gt            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

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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  Stream lt Path gt  paths   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

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File folder   new File   Users you folder     File   listOfFiles   folder listFiles     for  File file   listOfFiles        if  file isFile              System out println file getName

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Given a baseDir  lists out all the files and directories below it  written iteratively       public static List lt File gt  listLocalFilesAndDirsAllLevels File baseDir         List lt File gt   collectedFilesAndDirs     new ArrayList lt  gt         Deque lt File gt  remainingDirs             new ArrayDeque lt  gt          if baseDir exists              remainingDirs add baseDir            while  remainingDirs isEmpty                  File dir   remainingDirs removeLast                List lt File gt  filesInDir   Arrays asList dir listFiles                 for File fileOrDir   filesInDir                     collectedFilesAndDirs add fileOrDir                   if fileOrDir isDirectory                          remainingDirs add fileOrDir                                                        return collectedFilesAndDirs

[java] How to read all files in a folder from Java?

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