import java.io.File;
import java.util.Stack;

public class Main {

    public static void main(String[] args) {
        printFiles(new File("C:\\Users\\Marek\\Downloads"));
    }

    static private void printFiles(File dir) {
        Stack<FileObj> stack = new Stack<>();
        stack.push(new FileObj("", dir));
        while(!stack.isEmpty()) {
            FileObj child = stack.pop();
            if (child.file.isDirectory()) {
                System.out.println(child.depth + "<" + child.file.getName() + ">");
                for(File f : child.file.listFiles())
                {
                    stack.push(new FileObj(child.depth + "\t", f));
                }
            } else if (child.file.length() / 1024 < 500) {
                System.out.println(child.depth + child.file.getName() + " (" + child.file.length() / 1024 + "KB)");
            }
        }
    }

    private static class FileObj {
        private final String depth;
        private final File file;

        public FileObj(String depth, File file) {
            this.depth = depth;
            this.file = file;
        }
    }

}