Find files in a folder using Java

Question

What I need to do if Search a folder say C  example  I then need to go through each file and check to see if it matches a few start characters so if files start  temp     txt tempONE txt tempTWO txt   So if the file starts with temp and has an extension  txt I would like to then put that file name into a File file   new File  C  example temp    txt   so I can then read in the file  the loop then needs to move onto the next file to check to see if it meets as above

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Appache commons IO various  FilenameUtils wildcardMatch  See Apache javadoc here  It matches the wildcard with the filename  So you can use this method for your comparisons

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Matcher find and Files walk methods could be an option to search files in more flexible way String format combines regular expressions to create search restrictions Files isRegularFile checks if a path is t directory  symbolic link  etc    Usage     Searches file names  start with  temp  and extension   txt     in the current directory and subdirectories recursively Path initialPath   Paths get       PathUtils searchRegularFilesStartsWith initialPath   temp     txt                                           stream   forEach System out  println     Source   public final class PathUtils        private static final String startsWithRegex       lt       -  p L   d                      private static final String endsWithRegex             n         private static final String containsRegex     s                    i  s                public static List lt Path gt  searchRegularFilesStartsWith final Path initialPath                                final String fileName  final String fileExt  throws IOException           return searchRegularFiles initialPath  startsWithRegex   fileName  fileExt              public static List lt Path gt  searchRegularFilesEndsWith final Path initialPath                                final String fileName  final String fileExt  throws IOException           return searchRegularFiles initialPath  fileName   endsWithRegex  fileExt              public static List lt Path gt  searchRegularFilesAll final Path initialPath  throws IOException           return searchRegularFiles initialPath                      public static List lt Path gt  searchRegularFiles final Path initialPath                               final String fileName  final String fileExt              throws IOException           final String regex   String format containsRegex  fileName  fileExt           final Pattern pattern   Pattern compile regex           try  Stream lt Path gt  walk   Files walk initialPath toRealPath                   return walk filter path - gt  Files isRegularFile path   amp  amp                                         pattern matcher path toString    find                         collect Collectors toList                          private PathUtils               Try startsWith regex for  txt temp tempZERO0 txt      lt      - p L  d           temp                 i   txt           Try endsWith regex for  txt temp ZERO0temp txt   temp         n                   i   txt           Try contains regex for  txt temp tempZERO0tempZERO0temp txt   temp                 i   txt

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Consider Apache Commons IO  it has a class called FileUtils that has a listFiles method that might be very useful in your case

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As  Clarke said  you can use java io FilenameFilter to filter the file by specific condition    As a complementary  I d like to show how to use java io FilenameFilter to search file in current directory and its subdirectory   The common methods getTargetFiles and printFiles are used to search files and print them   public class SearchFiles          It s used in dfs     private Map lt String  Boolean gt  map   new HashMap lt String  Boolean gt          private File root       public SearchFiles File root           this root   root                        List eligible files on current path         param directory             The directory to be searched         return             Eligible files             private String   getTargetFiles File directory           if directory    null               return null                     String   files   directory list new FilenameFilter                  Override             public boolean accept File dir  String name                       TODO Auto-generated method stub                 return name startsWith  Temp    amp  amp  name endsWith   txt                                        return files                        Print all eligible files             private void printFiles String   targets           for String target  targets               System out println target                       I will demo how to use recursive  bfs and dfs to get the job done   Recursive              How many files in the parent directory and its subdirectory  lt br gt     depends on how many files in each subdirectory and their subdirectory     private void recursive File path        printFiles getTargetFiles path        for File file  path listFiles             if file isDirectory                 recursive file                       if path isDirectory             printFiles getTargetFiles path             public static void main String args         SearchFiles searcher   new SearchFiles new File  C   example         searcher recursive searcher root       Breadth First Search          Search the node s neighbors firstly before moving to the next level neighbors     private void bfs        if root    null           return             Queue lt File gt  queue   new LinkedList lt File gt         queue add root        while  queue isEmpty             File node   queue remove            printFiles getTargetFiles node            File   childs   node listFiles new FileFilter                  Override             public boolean accept File pathname                       TODO Auto-generated method stub                 if pathname isDirectory                        return true                   return false                                      if childs    null               for File child  childs                   queue add child                                    public static void main String args         SearchFiles searcher   new SearchFiles new File  C   example         searcher bfs        Depth First Search           Search as far as possible along each branch before backtracking     private void dfs         if root    null           return             Stack lt File gt  stack   new Stack lt File gt         stack push root       map put root getAbsolutePath    true       while  stack isEmpty             File node   stack peek            File child   getUnvisitedChild node            if child    null               stack push child               printFiles getTargetFiles child                map put child getAbsolutePath    true            else              stack pop                               Get unvisited node of the node         private File getUnvisitedChild File node        File   childs   node listFiles new FileFilter              Override         public boolean accept File pathname                   TODO Auto-generated method stub             if pathname isDirectory                    return true               return false                          if childs    null           return null             for File child  childs            if map containsKey child getAbsolutePath       false               map put child getAbsolutePath    false                      if map get child getAbsolutePath       false               return child                        return null     public static void main String args         SearchFiles searcher   new SearchFiles new File  C   example         searcher dfs

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As of Java 1 8  you can use Files list to get a stream    Path findFile Path targetDir  String fileName  throws IOException       return Files list targetDir  filter   p  - gt            if  Files isRegularFile p                 return p getFileName   toString   equals fileName             else               return false                   findFirst   orElse null

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What you want is File listFiles FileNameFilter filter    That will give you a list of the files in the directory you want that match a certain filter   The code will look similar to      your directory File f   new File  C   example    File   matchingFiles   f listFiles new FilenameFilter         public boolean accept File dir  String name            return name startsWith  temp    amp  amp  name endsWith  txt

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For list out Json files from your given directory   import java io File      import java io FilenameFilter       public class ListOutFilesInDir           public static void main String   args  throws Exception                File   fileList   getFileList  directory path                 for File file   fileList                    System out println file getName                                      private static File   getFileList String dirPath                File dir   new File dirPath                   File   fileList   dir listFiles new FilenameFilter                     public boolean accept File dir  String name                        return name endsWith   json                                                  return fileList

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You give the name of your file  the path of the directory to search  and let it make the job   private static String getPath String drl  String whereIAm        File dir   new File whereIAm     StaticMethods currentPath        src  main  resources           for File e   dir listFiles              if e isFile    amp  amp  e getName   equals drl    return e getPath             if e isDirectory                  String idiot   getPath drl  e getPath                 if idiot    null   return idiot                       return null

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Have a look at java io File list    and  FilenameFilter

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I know  this is an old question  But just for the sake of completeness  the lambda version     File dir   new File directory   File   files   dir listFiles  dir1  name  - gt  name startsWith  temp    amp  amp  name endsWith   txt

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To elaborate on this response  Apache IO Utils might save you some time   Consider the following example that will recursively search for a file of a given name       File file   FileUtils listFiles new File  the desired root path                     new NameFileFilter  filename ext                     FileFilterUtils trueFileFilter                 iterator   next      See    org apache commons io FileUtils org apache commons io filefilter FileFilterUtils https   commons apache org proper commons-io javadocs api-2 5 org apache commons io filefilter IOFileFilter html

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You can use a FilenameFilter  like so   File dir   new File directory    File   matches   dir listFiles new FilenameFilter       public boolean accept File dir  String name           return name startsWith  temp    amp  amp  name endsWith   txt

[java] Find files in a folder using Java

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