How to read all files in a folder from Java?

Answer 1

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
    }
}

Answer 2

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<File> instead of List<Path> just map it:

List<File> 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.

Answer 3

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);
            }
        }
    }

Answer 4

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");

Answer 5

Just walk through all Files using Files.walkFileTree (Java 7)

Files.walkFileTree(Paths.get(dir), new SimpleFileVisitor<Path>() {
    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        System.out.println("file: " + file);
        return FileVisitResult.CONTINUE;
    }
});

Answer 6

This will work fine:

private static void addfiles(File inputValVal, ArrayList<File> files)
{
  if(inputVal.isDirectory())
  {
    ArrayList <File> path = new ArrayList<File>(Arrays.asList(inputVal.listFiles()));

    for(int i=0; i<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);
   }

}