How to scan a folder in Java

Question

How can I get list all the files within a folder recursively in Java

User · Accepted Answer

Not sure how you want to represent the tree? Anyway here's an example which scans the entire subtree using recursion. Files and directories are treated alike. Note that File.listFiles() returns null for non-directories.

public static void main(String[] args) {
    Collection<File> all = new ArrayList<File>();
    addTree(new File("."), all);
    System.out.println(all);
}

static void addTree(File file, Collection<File> all) {
    File[] children = file.listFiles();
    if (children != null) {
        for (File child : children) {
            all.add(child);
            addTree(child, all);
        }
    }
}

Java 7 offers a couple of improvements. For example, DirectoryStream provides one result at a time - the caller no longer has to wait for all I/O operations to complete before acting. This allows incremental GUI updates, early cancellation, etc.

static void addTree(Path directory, Collection<Path> all)
        throws IOException {
    try (DirectoryStream<Path> ds = Files.newDirectoryStream(directory)) {
        for (Path child : ds) {
            all.add(child);
            if (Files.isDirectory(child)) {
                addTree(child, all);
            }
        }
    }
}

Note that the dreaded null return value has been replaced by IOException.

Java 7 also offers a tree walker:

static void addTree(Path directory, final Collection<Path> all)
        throws IOException {
    Files.walkFileTree(directory, new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
                throws IOException {
            all.add(file);
            return FileVisitResult.CONTINUE;
        }
    });
}

User · Answer

import java io File  public class Test       public static void main  String    args             File actual   new File               for  File f   actual listFiles                 System out println  f getName                          It displays indistinctly files and folders   See the methods in File class to order them or avoid directory print etc   http   java sun com javase 6 docs api java io File html

User · Answer

Check out Apache Commons FileUtils  listFiles  iterateFiles  etc    Nice convenience methods for doing what you want and also applying filters   http   commons apache org io api-1 4 org apache commons io FileUtils html

User · Answer

In JDK7   more NIO features  should have methods to apply the visitor pattern over a file tree or just the immediate contents of a directory - no need to find all the files in a potentially huge directory before iterating over them

User · Answer

Check out Apache Commons FileUtils  listFiles  iterateFiles  etc    Nice convenience methods for doing what you want and also applying filters   http   commons apache org io api-1 4 org apache commons io FileUtils html

User · Answer

import java io File  public class Test       public static void main  String    args             File actual   new File               for  File f   actual listFiles                 System out println  f getName                          It displays indistinctly files and folders   See the methods in File class to order them or avoid directory print etc   http   java sun com javase 6 docs api java io File html

User · Answer

You can also use the FileFilter interface to filter out what you want  It is best used when you create an anonymous class that implements it   import java io File  import java io FileFilter   public class ListFiles       public File   findDirectories File root             return root listFiles new FileFilter                 public boolean accept File f                    return f isDirectory                                public File   findFiles File root            return root listFiles new FileFilter                 public boolean accept File f                    return f isFile

User · Answer

public static void directory File dir        File   files   dir listFiles        for  File file   files            System out println file getAbsolutePath             if  file listFiles      null              directory file                      Here dir is Directory to be scanned  e g  c

User · Answer

public static void directory File dir        File   files   dir listFiles        for  File file   files            System out println file getAbsolutePath             if  file listFiles      null              directory file                      Here dir is Directory to be scanned  e g  c

User · Answer

Check out Apache Commons FileUtils  listFiles  iterateFiles  etc    Nice convenience methods for doing what you want and also applying filters   http   commons apache org io api-1 4 org apache commons io FileUtils html

User · Answer

Visualizing the tree structure was the most convenient way for me    public static void main String   args  throws IOException       printTree 0  new File  START FROM DIR        static void printTree int depth  File file  throws IOException        StringBuilder indent   new StringBuilder        String name   file getName         for  int i   0  i  lt  depth  i              indent append                    Pretty print for directories     if  file isDirectory               System out println indent toString                   if isPrintName name                System out println indent toString           file getName                                 Print file name     else if isPrintName name             System out println indent toString     file getName                  Recurse children     if  file isDirectory               File   files   file listFiles             for  int i   0  i  lt  files length  i                 printTree depth   4  files i                          Exclude some file names static boolean isPrintName String name       if  name charAt 0                    return false            if  name contains  svn              return false                        Some more exclusions             return true

User · Answer

In JDK7   more NIO features  should have methods to apply the visitor pattern over a file tree or just the immediate contents of a directory - no need to find all the files in a potentially huge directory before iterating over them

User · Answer

You can also use the FileFilter interface to filter out what you want  It is best used when you create an anonymous class that implements it   import java io File  import java io FileFilter   public class ListFiles       public File   findDirectories File root             return root listFiles new FileFilter                 public boolean accept File f                    return f isDirectory                                public File   findFiles File root            return root listFiles new FileFilter                 public boolean accept File f                    return f isFile

User · Answer

You can also use the FileFilter interface to filter out what you want  It is best used when you create an anonymous class that implements it   import java io File  import java io FileFilter   public class ListFiles       public File   findDirectories File root             return root listFiles new FileFilter                 public boolean accept File f                    return f isDirectory                                public File   findFiles File root            return root listFiles new FileFilter                 public boolean accept File f                    return f isFile

User · Answer

Visualizing the tree structure was the most convenient way for me    public static void main String   args  throws IOException       printTree 0  new File  START FROM DIR        static void printTree int depth  File file  throws IOException        StringBuilder indent   new StringBuilder        String name   file getName         for  int i   0  i  lt  depth  i              indent append                    Pretty print for directories     if  file isDirectory               System out println indent toString                   if isPrintName name                System out println indent toString           file getName                                 Print file name     else if isPrintName name             System out println indent toString     file getName                  Recurse children     if  file isDirectory               File   files   file listFiles             for  int i   0  i  lt  files length  i                 printTree depth   4  files i                          Exclude some file names static boolean isPrintName String name       if  name charAt 0                    return false            if  name contains  svn              return false                        Some more exclusions             return true

User · Answer

import java io File  public class Test       public static void main  String    args             File actual   new File               for  File f   actual listFiles                 System out println  f getName                          It displays indistinctly files and folders   See the methods in File class to order them or avoid directory print etc   http   java sun com javase 6 docs api java io File html

User · Answer

In JDK7   more NIO features  should have methods to apply the visitor pattern over a file tree or just the immediate contents of a directory - no need to find all the files in a potentially huge directory before iterating over them

User · Answer

You can also use the FileFilter interface to filter out what you want  It is best used when you create an anonymous class that implements it   import java io File  import java io FileFilter   public class ListFiles       public File   findDirectories File root             return root listFiles new FileFilter                 public boolean accept File f                    return f isDirectory                                public File   findFiles File root            return root listFiles new FileFilter                 public boolean accept File f                    return f isFile

User · Answer

import java io File  public class Test       public static void main  String    args             File actual   new File               for  File f   actual listFiles                 System out println  f getName                          It displays indistinctly files and folders   See the methods in File class to order them or avoid directory print etc   http   java sun com javase 6 docs api java io File html

User · Answer

In JDK7   more NIO features  should have methods to apply the visitor pattern over a file tree or just the immediate contents of a directory - no need to find all the files in a potentially huge directory before iterating over them

User · Answer

Check out Apache Commons FileUtils  listFiles  iterateFiles  etc    Nice convenience methods for doing what you want and also applying filters   http   commons apache org io api-1 4 org apache commons io FileUtils html

[java] How to scan a folder in Java?

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