package com.my.tree;import java.util.List;public class Tree {	private String id; // 节点ID		private String parentId; // 节点父ID		private List
    
      children;	public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getParentId() {		return parentId;	}	public void setParentId(String parentId) {		this.parentId = parentId;	}	public List
     
       getChildren() {		return children;	}	public void setChildren(List
      
        children) {		this.children = children;	}	}
      
     
    

package com.my.tree;import java.util.ArrayList;import java.util.List;public class TreeUtils {	public static List
    
      formatTree(List
     
       list) {		List
      
        nodeList = new ArrayList
       
        ();		for (Tree node1 : list) {			boolean mark = false;			for (Tree node2 : list) {				if (node1.getParentId() != null && node1.getParentId().equals(node2.getId())) {					mark = true;					if (node2.getChildren() == null) {						node2.setChildren(new ArrayList
        
         ());					}					node2.getChildren().add(node1);					break;				}			}			if (!mark) {				nodeList.add(node1);			}		}		return nodeList;	}	}