文本中实现树型结构

import java.util.ArrayList;
import java.util.List;

public class Folder
{
    public Folder(String title)
    {
        this.title = title;
    }

    private String title;

    private List   children = new ArrayList();

    public void addChild(Folder f)
    {
        children.add(f);
    }

    public List getChildren()
    {
        return children;
    }

    public void setChildren(List children)
    {
        this.children = children;
    }

    public String getTitle()
    {
        return title;
    }

    public void setTitle(String title)
    {
        this.title = title;
    }

    public String toString(String lftStr, String append)
    {
        StringBuffer b = new StringBuffer();
        b.append(append + title);
        b.append(" ");
        if (children.size() > 0)
        {
            for (int i = 0; i < children.size() - 1; i++)
            {
                b.append(lftStr
                        + ((Folder) children.get(i))
                                .toString(lftStr + "│", "├"));
            }
            b.append(lftStr
                    + ((Folder) children.get(children.size() - 1)).toString(
                            lftStr + " ", "└"));
        }
        return b.toString();
    }

    public static void main(String[] args)
    {
        Folder root = new Folder("菜单列表");
        Folder f1 = new Folder("开始菜单");
        root.addChild(f1);
        Folder f1_1 = new Folder("程序");
        f1.addChild(f1_1);
        Folder f1_1_1 = new Folder("附件");
        f1_1.addChild(f1_1_1);
        Folder f1_1_1_1 = new Folder("娱乐");
        f1_1_1.addChild(f1_1_1_1);
        Folder f1_1_1_2 = new Folder("娱乐2");
        f1_1_1.addChild(f1_1_1_2);
        Folder f1_2 = new Folder("辅助工具");
        f1.addChild(f1_2);
        Folder f2 = new Folder("My Documents ");
        root.addChild(f2);
        Folder f3 = new Folder("My Documents2 ");
        root.addChild(f3);
        System.out.println(root.toString("    \r\n", ""));
    }
}