In this post, we will see how to traverse a directory and list out all files present in it and all its subdirectories in Java 7 and 8.
In the previous post, we have seen how to traverse the given directory and print all files present in it and its subdirectories using BFS and DFS. In this post, we will discuss latest API introduced in Java 7 and Java 8 for this purpose.
1. Java 8
In Java 8, we can use Files.walk(...) method that takes the starting file as parameter and return a Stream of Path objects by walking the file tree in depth-first manner, which is rooted at a given starting file.
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import java.io.IOException; import java.nio.file.Files; import java.nio.file.Paths; class FileUtils { // Function to traverse a directory and list all the files in Java 8 public static void main(String[] args) { // Root directory String rootDir = "C:\\Users"; try { // using Files.walk method Files.walk(Paths.get(rootDir)) .filter(Files::isRegularFile) .forEach(System.out::println); } catch (IOException e) { e.printStackTrace(); } } } |
We can use try-with-resources construct to ensure that the stream is closed after the stream operations are completed. Below example uses Files.walk(...) method with try-with-resources.
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try { // using Files.walk method with try-with-resources try (Stream<Path> paths = Files.walk(Paths.get(rootDir))) { paths.filter(Files::isRegularFile) .forEach(System.out::println); } } catch (IOException e) { e.printStackTrace(); } |
We can also use Files.find(...) method that walks the file tree in exactly the manner specified by the walk method.
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import java.io.IOException; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; import java.util.stream.Stream; class FileUtils { // Function to traverse a directory and list all the files in Java 8 public static void main(String[] args) { // Root directory String rootDir = "C:\\Users"; try { // using Files.find method with try-with-resources try (Stream<Path> paths = Files.find(Paths.get(rootDir), Integer.MAX_VALUE, (path, file) -> file.isRegularFile())) { paths.forEach(System.out::println); } } catch (IOException e) { e.printStackTrace(); } } } |
2. Java 7
In Java 7, we can use Files.walkFileTree(...) that walks a file tree. It requires only a starting point and an instance of FileVisitor to invoke for each file.
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import java.io.IOException; import java.nio.file.*; import java.nio.file.attribute.BasicFileAttributes; class FileUtils { // Function to traverse a directory and list all the files in Java 7 public static void main(String[] args) { // Root directory String rootDir = "C:\\Users"; try { // using Files.walkFileTree method in Java 7 Files.walkFileTree(Paths.get(rootDir), new SimpleFileVisitor<Path>() { @Override public FileVisitResult visitFile(Path filePath, BasicFileAttributes attributes) { System.out.println(filePath); return FileVisitResult.CONTINUE; } }); } catch (IOException e) { e.printStackTrace(); } } } |
Also see: List all files in a directory in Java using Guava and Apache Commons
References: https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html
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