Java Files.list

last modified July 6, 2024

In this article we show how to list files in Java with Files.list.

Files.list returns a lazily populated stream of directory elements. The listing is not recursive.

The elements of the stream are Path objects.

Listing current directory

The first example lists the current directory.

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

void main() throws IOException {

    var path = Paths.get(".");

    try (var files = Files.list(path)) {
        files.forEach(System.out::println);
    }
}

The dot symbol represents the current working directory. We get the path object with Paths.get.

Listing directories in home directory

The following example lists directories in the user's home directory.

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;

void main() throws IOException {

    var homeDir = System.getProperty("user.home");
    var path = new File(homeDir).toPath();

    try (var files = Files.list(path)) {
        files.filter(p -> p.toFile().isDirectory())
                .forEach(System.out::println);
    }
}

We convert the path object to a File with toFile and call the isDirectory method. The stream is filtered with filter.

Listing by file extensions

The next program lists all PDF files.

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

void main() throws IOException {

    var homeDir = System.getProperty("user.home")
            + FileSystems.getDefault().getSeparator() + "Downloads";

    try (var files = Files.list(Paths.get(homeDir))) {
        files.filter(path -> path.toString().endsWith(".pdf"))
                .forEach(System.out::println);
    }
}

The program lists PDF files in the Downloads directory. The path object is converted to a string and we call endsWith on the string to check if it ends with pdf extension.

Counting files

We count the number of PDF files.

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

void main() throws IOException {

    var homeDir = System.getProperty("user.home")
            + FileSystems.getDefault().getSeparator() + "Downloads";

    try (var files = Files.list(Paths.get(homeDir))) {
        var nOfPdfFiles = files.filter(path -> path.toString()
                .endsWith(".pdf")).count();
        System.out.printf("There are %d PDF files", nOfPdfFiles);
    }
}

The number of files is determined with count.

Source

Java Basic I/O - tutorial

In this article we have used Files.list to list the directory contents.

Author

My name is Jan Bodnar and I am a passionate programmer with many years of programming experience. I have been writing programming articles since 2007. So far, I have written over 1400 articles and 8 e-books. I have over eight years of experience in teaching programming.

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