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<MultiTreeNode> children;
 public MultiTreeNode() {
 }
 public MultiTreeNode(int id, String name) {
  this.id = id;
  this.name = name;
 }
 public MultiTreeNode(int id, String name, List<MultiTreeNode> 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<MultiTreeNode> getChildren() {
  return children;
 }
 public void setChildren(List<MultiTreeNode> 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<SingleTreeNode> singleTreeNodes;
 private List<MultiTreeNode> multiTreeNodes = new ArrayList<>();
 public ToMultiTreeTransformer(List<SingleTreeNode> singleTreeNodes) {
  this.singleTreeNodes = singleTreeNodes;
 }
 public List<MultiTreeNode> 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<MultiTreeNode> 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<MultiTreeNode> multiTreeNodes;
 private List<SingleTreeNode> singleTreeNodes = new ArrayList<>();
 public ToSingleTreeTransformer(List<MultiTreeNode> multiTreeNodes) {
  this.multiTreeNodes = multiTreeNodes;
 }
 public List<SingleTreeNode> 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<MultiTreeNode> 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<SingleTreeNode> SINGLE_TREE = new ArrayList<SingleTreeNode>();
 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<MultiTreeNode> multiTreeNodes = multiTreeTransformer.transform();
  System.out.println(multiTreeNodes);
  ToSingleTreeTransformer singleTreeTransformer = new ToSingleTreeTransformer(multiTreeNodes);
  List<SingleTreeNode> 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]]