如何制作n-tree树并预先遍历

Question

我正在开发一个j2ee项目，我需要一个动态菜单。 我有数据库中的数据。现在我想制作一棵树并遍历树的预订。 你能帮我怎么做吗？

Answer 1

这是我的工作代码，用于创建树并遍历预订和有序。

希望它能帮助你。

public class NaryTree { 
    static HashMap<String, NaryTree.Node> tree = new HashMap<String, NaryTree.Node>(); 

    public static void main(String[] args) { 
     new NaryTree().makeTree(); 
     traverseFrom(tree.get("000")); 
    } 

    public static void traverseFrom(Node rootNode) {  
     if(rootNode.getChildren().size()!= 0) { 
      for (Node pNode : rootNode.getChildren()) {    
       System.out.println(" Lavel:"+pNode.lavel+" - Node Value:"+pNode.val); // preorder traverse    
       traverseFrom(pNode); 
       //System.out.print(" Lavel :"+pNode.lavel+"- Node Value :"+pNode.val); // preorder traverse 
      }   
     }  
    } 

    private void makeTree() { 

     Node newNode = new Node("000", null, new ArrayList<NaryTree.Node>()); 
     newNode.setLavel(0); 
     tree.put("000", newNode);  
     //newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("101", tree.get("000"), new ArrayList<NaryTree.Node>()); 
     tree.put("101", newNode); 
     newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("102", tree.get("000"), new ArrayList<NaryTree.Node>()); 
     tree.put("102", newNode); 
     newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("103", tree.get("000"), new ArrayList<NaryTree.Node>()); 
     tree.put("103", newNode); 
     newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("201", tree.get("101"), new ArrayList<NaryTree.Node>()); 
     tree.put("201", newNode); 
     newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("202", tree.get("101"), new ArrayList<NaryTree.Node>()); 
     tree.put("202", newNode); 
     newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("205", tree.get("103"), new ArrayList<NaryTree.Node>()); 
     tree.put("205", newNode); 
     newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("301", tree.get("201"), new ArrayList<NaryTree.Node>()); 
     tree.put("301", newNode); 
     newNode.getParent().getChildren().add(newNode); 

     newNode = new Node("104", tree.get("000"), new ArrayList<NaryTree.Node>()); 
     tree.put("104", newNode); 
     newNode.getParent().getChildren().add(newNode); 
    } 

private class Node { 

     private String val; 
     private int lavel; 
     private Node parent; 
     private List<Node> children; 

     public Node(String val, Node parent, List<Node> children) { 
      this.val = val; 
      this.parent = parent; 
      this.children = children; 
      if(parent!=null) 
       this.lavel = (int) parent.getLavel()+1; 
      else 
       this.lavel = 0; 
     } 

     public String getVal() { 
      return val; 
     } 
     public void setVal(String val) { 
      this.val = val; 
     } 
     public Node getParent() { 
      return parent; 
     } 
     public void setParent(Node parent) { 
      this.parent = parent; 
     } 
     public List<Node> getChildren() { 
      return children; 
     } 
     public void setChildren(List<Node> children) { 
      this.children = children; 
     } 

     public int getLavel() { 
      return lavel; 
     } 

     public void setLavel(int lavel) { 
      this.lavel = lavel; 
     } 
    } 
} 

Answer 2

看看Primefaces的树组件，特别是java代码和文档：p:tree。它显示了哪些对象被用作树节点以及树是如何初始化的。希望这可以帮助。