Java 8 – List of All Files in a Directory

Learn to use Java 8 APIs such as Files.list() and DirectoryStream to list all files present in a directory, including hidden files, recursively.

For using external iteration (for loop) use DirectoryStream. For using Stream API operations (map, filter, sorted, collect), use Files.list() instead.

1. Files.list() – Iterate over all files and sub-directories

Java example to iterate over a directory and get the List<File> using Files.list() method.

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;

public class IterateDirectoryExample {

	public static void main(String[] args) {

		String dirLocation = "C:/temp";

		try {
			List<File> files = Files.list(Paths.get(dirLocation))
						.map(Path::toFile)
						.collect(Collectors.toList());
			
			files.forEach(System.out::println);
		} catch (IOException e) {
			// Error while reading the directory
		}
	}
}

Program Output:

C:\temp\filename1.txt
C:\temp\directory1
C:\temp\filename2.txt
C:\temp\Employee.java

2. Files.list() – List only files excluding sub-directories

Use the filter expression Files::isRegularFile to check if a file is normal file, and not any directory.

String dirLocation = "C:/temp";

List<File> files = Files.list(Paths.get(dirLocation))
				.filter(Files::isRegularFile)
				.map(Path::toFile)
				.collect(Collectors.toList());

files.forEach(System.out::println);

Program Output:

C:\temp\filename1.txt
C:\temp\filename2.txt
C:\temp\Employee.java

To list files in a different directory, we can replace "." with the full path of the directory we desire.

3. Files.newDirectoryStream() – List all files and sub-directories

Java provides a more flexible way of traversing a directory content using Files.newDirectoryStream().

Please note that if we’re working with a large directory, then using DirectoryStream actually make code faster.

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class IterateDirectoryExample {

	public static void main(String[] args) {

		String dirLocation = "C:/temp";

		try {
			for (Path path : Files.newDirectoryStream(Paths.get(dirLocation))) {

				path = path.normalize();
				System.out.println(path.getFileName());
			}
		} catch (IOException e) {
			// Error while reading the directory
		}
	}
}

Program Output:

C:\temp\filename1.txt
C:\temp\directory1
C:\temp\filename2.txt
C:\temp\Employee.java

4. Files.newDirectoryStream() – Iterate only files excluding sub-directories

To loop through only the files and excluding all the sub-directories from the stream, use path filter isFile() as the second argument to the newDirectoryStream() constructor.

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class IterateDirectoryExample {

	public static void main(String[] args) {

		String dirLocation = "C:/temp";

		try {
			for (Path path : Files.newDirectoryStream(Paths.get(dirLocation), 
						path -> path.toFile().isFile())) {

				path = path.normalize();
				System.out.println(path.getFileName());
			}
		} catch (IOException e) {
			// Error while reading the directory
		}
	}
}

Program Output:

C:\temp\filename1.txt
C:\temp\filename2.txt
C:\temp\Employee.java

5. List of all files of certain extention only

To get the list of all files of certain extensions only, use two predicates Files::isRegularFile and path.toString().endsWith(".java") together.

With the above predicate, we are listed all .java files in a folder.

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;

public class IterateDirectoryExample {

	public static void main(String[] args) {

		String dirLocation = "C:/temp";

		try {
			List<File> files = Files.list(Paths.get(dirLocation))
									.filter(Files::isRegularFile)
									.filter(path -> path.toString().endsWith(".java"))
									.map(Path::toFile)
									.collect(Collectors.toList());
			
			files.forEach(System.out::println);
		} catch (IOException e) {
			// Error while reading the directory
		}
	}
}

Program Output:

C:\temp\Employee.java

6. Finding all hidden files in a directory

To find all the hidden files, we can use filter expression file -> file.isHidden() in any of above example.

List<File> files = Files.list(Paths.get(dirLocation))
			.filter(path -> path.toFile().isHidden())
			.map(Path::toFile)
			.collect(Collectors.toList());

In the above examples, we learn to use the java 8 APIs loop through the files in a directory recursively using various search methods. Feel free to modify the code and play with it.

Happy Learning !!

References:

DirectoryStream
Files.list() method