How to read all files in a folder from Java?

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<Path> 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.

File folder = new File("/Users/you/folder/");
File[] listOfFiles = folder.listFiles();

for (File file : listOfFiles) {
    if (file.isFile()) {
        System.out.println(file.getName());
    }
}

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.