package com.zzj.tree;
public class SingleTreeNode {
	private int id;
	private int pId;
	private String name;
	public SingleTreeNode() {
	}
	public SingleTreeNode(int id, int pId, String name) {
		this.id = id;
		this.pId = pId;
		this.name = name;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public int getpId() {
		return pId;
	}
	public void setpId(int pId) {
		this.pId = pId;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@Override 
	  public String toString() {
		return "SingleTreeNode [id=" + id + ", pId=" + pId + ", name=" + name + "]";
	}
}

package com.zzj.tree;
import java.util.List;
public class MultiTreeNode {
	private int id;
	private String name;
	private List children;
	public MultiTreeNode() {
	}
	public MultiTreeNode(int id, String name) {
		this.id = id;
		this.name = name;
	}
	public MultiTreeNode(int id, String name, List children) {
		this.id = id;
		this.name = name;
		this.children = children;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public List getChildren() {
		return children;
	}
	public void setChildren(List children) {
		this.children = children;
	}
	@Override 
	  public String toString() {
		return "MultiTreeNode [id=" + id + ", name=" + name + ", children=" + children + "]";
	}
}

package com.zzj.tree;
import java.util.ArrayList;
import java.util.List;
public class ToMultiTreeTransformer {
	private List singleTreeNodes;
	private List multiTreeNodes = new ArrayList<>();
	public ToMultiTreeTransformer(List singleTreeNodes) {
		this.singleTreeNodes = singleTreeNodes;
	}
	public List transform(){
		// 先找出所有的根节点 
		for (int i = 0; i < singleTreeNodes.size(); i++) {
			SingleTreeNode singleTreeNode = singleTreeNodes.get(i);
			Boolean isRoot = true;
			for (int j = 0; j < singleTreeNodes.size(); j++) {
				SingleTreeNode temp = singleTreeNodes.get(j);
				if (singleTreeNode.getpId() == temp.getId()) {
					isRoot = false;
					break;
				}
			}
			if (isRoot) {
				MultiTreeNode multiTreeNode = new MultiTreeNode(singleTreeNode.getId(),  
				            singleTreeNode.getName());
				multiTreeNodes.add(multiTreeNode);
			}
		}
		// 设置子节点 
		for (int i = 0; i < multiTreeNodes.size(); i++) {
			MultiTreeNode multiTreeNode = multiTreeNodes.get(i);
			setChildren(multiTreeNode);
		}
		return multiTreeNodes;
	}
	/** 
   * 设置子节点 
   * @param multiTreeNode 
   */
	private void setChildren(MultiTreeNode multiTreeNode){
		for (int j = 0; j < singleTreeNodes.size(); j++) {
			SingleTreeNode temp = singleTreeNodes.get(j);
			if (temp.getpId() == multiTreeNode.getId()) {
				MultiTreeNode child = new MultiTreeNode(temp.getId(),  
				            temp.getName());
				List children = multiTreeNode.getChildren();
				if (children == null) {
					children = new ArrayList<>();
					multiTreeNode.setChildren(children);
				}
				children.add(child);
				setChildren(child);
			}
		}
	}
}

package com.zzj.tree;
import java.util.ArrayList;
import java.util.List;
public class ToSingleTreeTransformer {
	private List multiTreeNodes;
	private List singleTreeNodes = new ArrayList<>();
	public ToSingleTreeTransformer(List multiTreeNodes) {
		this.multiTreeNodes = multiTreeNodes;
	}
	public List transform(){
		// 先获取根节点 
		for (int i = 0; i < multiTreeNodes.size(); i++) {
			MultiTreeNode multiTreeNode = multiTreeNodes.get(i);
			SingleTreeNode singleTreeNode = new SingleTreeNode(multiTreeNode.getId(),  
			          0, multiTreeNode.getName());
			singleTreeNodes.add(singleTreeNode);
		}
		// 获取子节点 
		for (int i = 0; i < multiTreeNodes.size(); i++) {
			MultiTreeNode multiTreeNode = multiTreeNodes.get(i);
			getChildren(multiTreeNode);
		}
		return singleTreeNodes;
	}
	/** 
   * 获取子节点 
   * @param multiTreeNode 
   */
	private void getChildren(MultiTreeNode multiTreeNode){
		for (int i = 0; i < singleTreeNodes.size(); i++) {
			SingleTreeNode temp = singleTreeNodes.get(i);
			if (multiTreeNode.getId() == temp.getId()) {
				List children = multiTreeNode.getChildren();
				if (children != null) {
					for (int j = 0; j < children.size(); j++) {
						MultiTreeNode child = children.get(j);
						SingleTreeNode singleTreeNode = new SingleTreeNode(child.getId(),  
						                multiTreeNode.getId(), child.getName());
						singleTreeNodes.add(singleTreeNode);
						getChildren(child);
					}
				}
			}
		}
	}
}

package com.zzj.tree;
import java.util.ArrayList;
import java.util.List;
public class TreeTransformerTest {
	private final static List SINGLE_TREE = new ArrayList();
	static {
		SingleTreeNode China = new SingleTreeNode(1, 0, "中国");
		SINGLE_TREE.add(China);
		SingleTreeNode Hunan = new SingleTreeNode(2, 1, "湖南");
		SINGLE_TREE.add(Hunan);
		SingleTreeNode Changsha = new SingleTreeNode(3, 2, "长沙");
		SINGLE_TREE.add(Changsha);
		SingleTreeNode Hubei = new SingleTreeNode(4, 1, "湖北");
		SINGLE_TREE.add(Hubei);
		SingleTreeNode Wuhan = new SingleTreeNode(5, 4, "武汉");
		SINGLE_TREE.add(Wuhan);
		SingleTreeNode America = new SingleTreeNode(6, 0, "美国");
		SINGLE_TREE.add(America);
		SingleTreeNode California = new SingleTreeNode(7, 6, "加利福尼亚");
		SINGLE_TREE.add(California);
		SingleTreeNode LosAngeles = new SingleTreeNode(8, 7, "洛杉矶");
		SINGLE_TREE.add(LosAngeles);
	}
	public static void main(String[] args) throws Exception {
		ToMultiTreeTransformer multiTreeTransformer = new ToMultiTreeTransformer(SINGLE_TREE);
		List multiTreeNodes = multiTreeTransformer.transform();
		System.out.println(multiTreeNodes);
		ToSingleTreeTransformer singleTreeTransformer = new ToSingleTreeTransformer(multiTreeNodes);
		List singleTreeNodes = singleTreeTransformer.transform();
		System.out.println(singleTreeNodes);
	}
}

[MultiTreeNode [id=1, name=中国, children=[MultiTreeNode [id=2, name=湖南, children=[MultiTreeNode [id=3, name=长沙, children=null]]], MultiTreeNode [id=4, name=湖北, children=[MultiTreeNode [id=5, name=武汉, children=null]]]]], MultiTreeNode [id=6, name=美国, children=[MultiTreeNode [id=7, name=加利福尼亚, children=[MultiTreeNode [id=8, name=洛杉矶, children=null]]]]]] 
[SingleTreeNode [id=1, pId=0, name=中国], SingleTreeNode [id=6, pId=0, name=美国], SingleTreeNode [id=2, pId=1, name=湖南], SingleTreeNode [id=3, pId=2, name=长沙], SingleTreeNode [id=4, pId=1, name=湖北], SingleTreeNode [id=5, pId=4, name=武汉], SingleTreeNode [id=7, pId=6, name=加利福尼亚], SingleTreeNode [id=8, pId=7, name=洛杉矶]]