How to get size of a directory in Java

By mkyong | Updated: July 29, 2020

Viewed: 7,847 (+53 pv/w)

Tags: commons-io directory file size file visitor file walker java 8 java.io java.nio

In Java, we can use Files.size to get the size of a file; for the directory or folder size, we need to count the size of a directory recursively (sum of the Files.size of all files).

This example shows a few common ways to get the size of a directory or folder.

1. FileVisitor (Java 7)
2. Files.walk (Java 8)
3. FileUtils.sizeOfDirectory (Apache Common IO)
4. Sum file.length of all files. (Legacy IO)

1. Directory Size – FileVisitor (Java 7)

This example uses the FileVisitor to visit all files from a specified path and sum the size of all files.

  // size of directory in bytes
  public static long getDirectorySizeJava7(Path path) {

      AtomicLong size = new AtomicLong(0);

      try {

          Files.walkFileTree(path, new SimpleFileVisitor<>() {

              @Override
              public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
                  // sum size of all visit file
                  size.addAndGet(attrs.size());
                  return FileVisitResult.CONTINUE;
              }

              @Override
              public FileVisitResult visitFileFailed(Path file, IOException e) {
                  System.out.printf("Failed to get size of %s%n%s", file, e);
                  return FileVisitResult.CONTINUE;
              }

          });
      } catch (IOException e) {
          System.out.printf("%s", e);
      }

      return size.get();

  }

2. Directory Size – Files.walk (Java 8)

This example uses Java 8 Files.walk and Stream to walk a directory recursively and sum the size of all files.

  // size of directory in bytes
  public static long getDirectorySizeJava8(Path path) {

      long size = 0;

      // need close Files.walk
      try (Stream<Path> walk = Files.walk(path)) {

          size = walk
                  //.peek(System.out::println) // debug
                  .filter(Files::isRegularFile)
                  .mapToLong(p -> {
                      // ugly, can pretty it with an extract method
                      try {
                          return Files.size(p);
                      } catch (IOException e) {
                          System.out.printf("Failed to get size of %s%n%s", p, e);
                          return 0L;
                      }
                  })
                  .sum();

      } catch (IOException e) {
          System.out.printf("IO errors %s", e);
      }

      return size;

  }

3. Directory Size – FileUtils (Apache Common IO)

This example uses the Apache Common IO FileUtils.sizeOfDirectory to get the size of a directory.

  <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.7</version>
  </dependency>

  public static long getDirectorySizeCommonIO(File dir) {

      return FileUtils.sizeOfDirectory(dir);

  }

4. Legacy IO

In legacy IO, we can use file.listFiles() to walk a directory recursively, and file.length() to sum the size of all files.

  public static long getDirectorySizeLegacy(File dir) {

      long length = 0;
      File[] files = dir.listFiles();
      if (files != null) {
          for (File file : files) {
              if (file.isFile())
                  length += file.length();
              else
                  length += getDirectorySizeLegacy(file);
          }
      }
      return length;

  }

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References

• Walking the File Tree
• Files JavaDoc
• FileUtils JavaDoc