Recursive directory size counting in Java

SizeAnnotatedFileTree.java

import lombok.Builder;
import lombok.Getter;
import lombok.SneakyThrows;
import lombok.Value;

import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Deque;
import java.util.List;

public class SizeAnnotatedFileTree {

    // TODO bool flag to distinguish files from directories
    @Value
    @Builder
    static class Node {
        private String name;
        private long size;
        private List<Node> children;
    }

    /**
     * Builds an abstract representation of a file tree annotated with file/directory sizes.
     */
    static class SizeFileVisitor extends SimpleFileVisitor<Path> {

        @Getter
        private final Deque<List<Node>> stack = new ArrayDeque<>() {{
            stack.push(new ArrayList<>());
        }};

        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
            stack.push(new ArrayList<>());
            return FileVisitResult.CONTINUE;
        }

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
            Node fileNode = new Node(file.getFileName().toString(), Files.size(file), Collections.emptyList());
            stack.peek().add(fileNode);
            return FileVisitResult.CONTINUE;
        }

        @Override
        public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
            List<Node> children = stack.pop();
            long directorySize = children.stream().mapToLong(Node::getSize).sum();
            Node dirNode = new Node(dir.getFileName().toString(), directorySize, children);
            stack.peek().add(dirNode);
            return FileVisitResult.CONTINUE;
        }
    }

    @SneakyThrows
    public Node getAbstractFileTree(Path root) {
        SizeFileVisitor visitor = new SizeFileVisitor();
        Files.walkFileTree(root, visitor);
        return visitor.getStack().peek().get(0);
    }
}