Java representation of directory structure. Need help on rewriting buildJson function. It should return JSON compatible with D3's circle packing data source. And mainly it should work :-|

Dir.java

package codesnapper;

import com.google.gson.Gson;
import com.google.gson.JsonArray;

import com.google.gson.JsonObject;

import java.util.HashMap;
import java.util.Map;

public class Dir {
    private Map<String, Dir> dirs = new HashMap<>();
    private Map<String, GitFile> files = new HashMap<>();
    private String name;
    public Dir(String name){
        this.name = name;
    }
    public String getName() {
        return name;
    }

    public void addFile(GitFile gitFile) {
        String[] folders = gitFile.getPath().split("/");
        Dir leafNode = this;
        for (String folder : folders) {
            if (!folder.isEmpty()) {
                if (leafNode.dirs.containsKey(folder)) {
                    leafNode = leafNode.dirs.get(folder);
                } else {
                    Dir newLeaf = new Dir(folder);
                    leafNode.dirs.put(folder, newLeaf);
                    leafNode = newLeaf;
                }
            }
        }
        leafNode.files.put(gitFile.getName(), gitFile);
        System.out.println(new Gson().toJson(this) );
    }

    public Dir get(String path) {
        Dir dir = this;
        String[] folders = path.split("/");
        for (String folder : folders) {
            if (!folder.isEmpty()) {
                dir = dir.dirs.get(folder);
            }
        }
        return dir;
    }

    public JsonObject toJson(){
        JsonObject object = new JsonObject();
       // buildJson(object);
        //System.out.println(object);
        return buildJson(object);
    }

    private JsonObject buildJson(JsonObject object){
        System.out.println("generating json for "+this.name);
        for(Map.Entry<String,Dir> entry:dirs.entrySet()){

            Dir thisDir = entry.getValue();
            object.addProperty("name",thisDir.name);
            JsonArray element = (JsonArray) new Gson().toJsonTree( thisDir.files.values());
            element.add(thisDir.toJson());
            object.add("children",element);

        }
        System.out.println(object);
        return object;
    }

    @Override
    public String toString() {
        return "Dir{" +
                "dirs=" + dirs +
                ", files=" + files +
                '}';
    }

    public GitFile getGitFile(String name) {
        return this.files.get(name);
    }
}