public abstract class Node {
  List<Node> children;

  public List<Node> getChidren() {
    if (children == null) {
      children = new ArrayList<>();
    }
    return chidren;
  }
}

它非常简单，很容易使用。要使用它，请扩展它:

public class MenuItem extends Node {
  String label;
  String href;
  ...
}

你可以使用Java的任何XML API作为文档和节点..因为XML是一个带有字符串的树结构

简单的例子:

public class ArbrePlaner {

public static void main(String[] args) {
    ArbrePlaner ll = new ArbrePlaner();
    
    ll.add(1,"A");
    ll.add(2,"B");
    ll.add(1,"C");
    ll.add(3,"D");
    ll.add(1,"Z");
    
    for(int i = 0; i < ll.size; i++){
    //  System.out.println(ll.isIdExist(i));
        System.out.println("-----------------");
        System.out.println(ll.getIdAt(i)+" :");
        linkedList lst = ll.getListDataById(ll.getIdAt(i));
        for(int j = 0; j < lst.size; j++){
            System.out.println(lst.getElementAt(j));
        }
    }
    
    
    
    
}

private int size;
private Noeud root;

public Noeud add(long Id, Object data){
    if(isIdExist(Id)){
        Noeud nd = getNoeudId(Id);
        nd.add(data);
        return nd;
    }else{
        Noeud nd = new Noeud(Id, data, this.root);
        this.root = nd;
        this.size++;
        return nd;
    }
}
 
 public Object getDataById(long Id, int x){
        Noeud thisNode = this.root;
        while(thisNode!=null){
            if(thisNode.getId() == Id){
                return thisNode.getLl().getElementAt(x);
            }
            thisNode = thisNode.getNextNoeud();
        }
        return null;
    }
 
 public long getIdAt(int x){
        if(size >= x){
            Noeud nd = this.root;
            for(int i = 0; i<x; i++)try {nd = nd.getNextNoeud();} catch (Exception e) {return -1;}
            return nd.getId();
        }
            return -1;
    }
 
 public linkedList getListDataById(long Id){
        Noeud thisNode = this.root;
        while(thisNode!=null){
            if(thisNode.getId() == Id){
                return thisNode.getLl();
            }
            thisNode = thisNode.getNextNoeud();
        }
        return null;
    }
 
public boolean deleteById(long id){
    Noeud thisNode = this.root;
    Noeud prevNode = null;
    
    while(thisNode != null){
        if(thisNode.getId() == id){
            prevNode.setNextNoeud(thisNode.getNextNoeud());
            this.setSize(this.getSize()-1);
            return true;
        }
        prevNode = thisNode;
        thisNode = thisNode.getNextNoeud();
    }
    return false;
}

 public boolean isIdExist(long Id){
        Noeud thisNode = this.root;
        while(thisNode!=null){
            if(thisNode.getId()== Id){
                return true;
            }
            thisNode = thisNode.getNextNoeud();
        }
        return false;
    }

 public boolean isDataExist(long Id, Object data){
     if(isIdExist(Id)){
         Noeud thisNode = this.root;
            while(thisNode!=null){
                if(thisNode.getId() == Id){
                    linkedList ll = thisNode.getLl();
                    long x = ll.hashCode();
                    long y = data.hashCode();
                    if(x==y) return true;
                }
                thisNode = thisNode.getNextNoeud();
            }
     }
     return false;
 }
 
 public Noeud getNoeudId(long Id){
        Noeud thisNode = this.root;
        while(thisNode!=null){
            if(thisNode.getId() == Id){
                return thisNode;
            }
            thisNode = thisNode.getNextNoeud();
        }
        return null;
    }

public ArbrePlaner() {
    this.root = root;
}

public ArbrePlaner(Noeud root) {
    this.root = root;
}

public ArbrePlaner(int size, Noeud root) {
    this.size = size;
    this.root = root;
}

public int getSize() {
    return size;
}

public void setSize(int size) {
    this.size = size;
}

public Noeud getRoot() {
    return root;
}

public void setRoot(Noeud root) {
    this.root = root;
}

private class Noeud{
    private long id;
    private Noeud nextNoeud;
    private linkedList Ll;
    
    public void add(Object data){
        Ll.add(data);
    }
    
    public Noeud(long id, Object data ,Noeud nextNoeud){
        this.id = id;
        this.nextNoeud = nextNoeud;
        Ll = new linkedList();
        Ll.add(data);
    }
    
    public long getId() {
        return id;
    }
    
    public Noeud(Object data){
        Ll.add(data);
    }
            
    public void setId(long id) {
        this.id = id;
    }
    public Noeud getNextNoeud() {
        return nextNoeud;
    }
    public void setNextNoeud(Noeud nextNoeud) {
        this.nextNoeud = nextNoeud;
    }
    public linkedList getLl() {
        return Ll;
    }
    public void setLl(linkedList ll) {
        Ll = ll;
    }
}
}

Java中有一些树数据结构，比如JDK Swing中的DefaultMutableTreeNode, Stanford解析器包中的tree，以及其他一些玩具代码。但这些都不够，也不够小，不能用于一般用途。

Java tree项目试图在Java中提供另一种通用的树数据结构。这个和其他的区别是

Totally free. You can use it anywhere (except in your homework :P) Small but general enough. I put everything of the data structure in one class file, so it would be easy to copy/paste. Not just a toys. I am aware of dozens of Java tree codes that can only handle binary trees or limited operations. This TreeNode is much more than that. It provides different ways of visiting nodes, such as preorder, postorder, breadthfirst, leaves, path to root, etc. Moreover, iterators are provided too for the sufficiency. More utils will be added. I am willing to add more operations to make this project comprehensive, especially if you send a request through github.

在这里:

public class Tree<T> {
    private Node<T> root;

    public Tree(T rootData) {
        root = new Node<T>();
        root.data = rootData;
        root.children = new ArrayList<Node<T>>();
    }

    public static class Node<T> {
        private T data;
        private Node<T> parent;
        private List<Node<T>> children;
    }
}

这是一个基本的树结构，可用于String或任何其他对象。实现简单的树来满足您的需要是相当容易的。

您需要添加的只是用于添加、删除、遍历和构造函数的方法。节点是树的基本构建块。

JDK中实际上实现了一个非常好的树结构。

看看javax.swing。tree、TreeModel和TreeNode。它们被设计为与JTreePanel一起使用，但实际上，它们是一个非常好的树实现，没有什么可以阻止你使用它与swing接口。

注意，从Java 9开始，你可能不希望使用这些类，因为它们不会出现在“压缩配置文件”中。