实现代码如下：

结点数据结构：package com.test.forest; import java.io.Serializable; import java.util.ArrayList; import java.util.List; import java.util.Random; public class SerPath implements Serializable{ private int fakePath = 0; public int layerIndex = -1; public List childList = new ArrayList<>(); public SerPath(int index){ fakePath = index; } public int getPath(){ return fakePath; } }

遍历流程：package com.test.forest; import java.util.ArrayList; import java.util.List; import java.util.Queue; import java.util.concurrent.LinkedBlockingQueue; public class Forest { /**构造测试样本**/ public List createForest() { /**森林表**/ List forestTreeHeadList = new ArrayList<>(); /**第一棵树**/ SerPath treeHead1 = new SerPath(1); treeHead1.childList.add(new SerPath(2)); treeHead1.childList.add(new SerPath(3)); treeHead1.childList.add(new SerPath(4)); treeHead1.childList.add(new SerPath(5)); treeHead1.childList.get(2).childList.add(new SerPath(6)); treeHead1.childList.get(2).childList.add(new SerPath(7)); treeHead1.childList.get(2).childList.add(new SerPath(8)); treeHead1.childList.get(2).childList.add(new SerPath(9)); forestTreeHeadList.add(treeHead1); /**第2棵树**/ SerPath treeHead2 = new SerPath(10); treeHead2.childList.add(new SerPath(11)); treeHead2.childList.add(new SerPath(12)); treeHead2.childList.add(new SerPath(13)); treeHead2.childList.get(0).childList.add(new SerPath(14)); treeHead2.childList.get(0).childList.add(new SerPath(15)); treeHead2.childList.get(0).childList.add(new SerPath(16)); treeHead2.childList.get(2).childList.add(new SerPath(17)); treeHead2.childList.get(2).childList.add(new SerPath(18)); forestTreeHeadList.add(treeHead2); return forestTreeHeadList; } /**遍历森林中的所有树和树节点**/ public void readForest(List forestTreeHeadList) { for(SerPath treeHead : forestTreeHeadList){ Queue> layerQueue = new LinkedBlockingQueue<>(); //输出头结点的值： System.out.println(treeHead.getPath()); //发现头结点有孩子表，表入队： if(!treeHead.childList.isEmpty()){ layerQueue.add(treeHead.childList); } //只要孩子表队列不为空就循环 while(!layerQueue.isEmpty()){ List nodeList = layerQueue.poll(); //出队孩子表表头 for(SerPath childNode : nodeList){ //遍历当前孩子表，如果孩子节点也有孩子表，则将这个孩子节点的孩子表放入队尾等候遍历 System.out.println(childNode.getPath()); //读孩子数据 if(!childNode.childList.isEmpty()) { //如果孩子节点也有孩子表，则将这个孩子节点的孩子表放入队尾等候遍历 layerQueue.add(childNode.childList); } } } } } public static void main(String[] args) { Forest forest = new Forest(); forest.readForest(forest.createForest()); } }

实际输出：

利用序列化保存再读取的测试：package com.test.forest; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.util.ArrayList; import java.util.List; import java.util.Queue; import java.util.concurrent.LinkedBlockingQueue; public class Forest { /**构造测试样本**/ public List createForest() { /**森林表**/ List forestTreeHeadList = new ArrayList<>(); /**第一棵树**/ SerPath treeHead1 = new SerPath(1); treeHead1.childList.add(new SerPath(2)); treeHead1.childList.add(new SerPath(3)); treeHead1.childList.add(new SerPath(4)); treeHead1.childList.add(new SerPath(5)); treeHead1.childList.get(2).childList.add(new SerPath(6)); treeHead1.childList.get(2).childList.add(new SerPath(7)); treeHead1.childList.get(2).childList.add(new SerPath(8)); treeHead1.childList.get(2).childList.add(new SerPath(9)); forestTreeHeadList.add(treeHead1); /**第2棵树**/ SerPath treeHead2 = new SerPath(10); treeHead2.childList.add(new SerPath(11)); treeHead2.childList.add(new SerPath(12)); treeHead2.childList.add(new SerPath(13)); treeHead2.childList.get(0).childList.add(new SerPath(14)); treeHead2.childList.get(0).childList.add(new SerPath(15)); treeHead2.childList.get(0).childList.add(new SerPath(16)); treeHead2.childList.get(2).childList.add(new SerPath(17)); treeHead2.childList.get(2).childList.add(new SerPath(18)); forestTreeHeadList.add(treeHead2); return forestTreeHeadList; } /**遍历森林中的所有树和树节点**/ public void readForest(List forestTreeHeadList) { for(SerPath treeHead : forestTreeHeadList){ Queue> layerQueue = new LinkedBlockingQueue<>(); //输出头结点的值： System.out.println(treeHead.getPath()); //发现头结点有孩子表，表入队： if(!treeHead.childList.isEmpty()){ layerQueue.add(treeHead.childList); } //只要孩子表队列不为空就循环 while(!layerQueue.isEmpty()){ List nodeList = layerQueue.poll(); //出队孩子表表头 for(SerPath childNode : nodeList){ //遍历当前孩子表，如果孩子节点也有孩子表，则将这个孩子节点的孩子表放入队尾等候遍历 System.out.println(childNode.getPath()); //读孩子数据 if(!childNode.childList.isEmpty()) { //如果孩子节点也有孩子表，则将这个孩子节点的孩子表放入队尾等候遍历 layerQueue.add(childNode.childList); } } } } } /**前序遍历、深度优先遍历**/ public void readForestDepthFirst(List forestTreeHeadList){ if(forestTreeHeadList == null || forestTreeHeadList.isEmpty()) return; for(SerPath path : forestTreeHeadList) { System.out.println(path.getPath()); readForest(path.childList); } } public static void main(String[] args) { Forest forest = new Forest(); List forestTreeHeadList = forest.createForest(); //广度遍历： forest.readForest(forestTreeHeadList); System.out.println(); try { File file = new File("E:\\1.temp"); if(!file.exists()){ file.createNewFile(); } FileOutputStream outputStream = new FileOutputStream(file); ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream); objectOutputStream.writeObject(forestTreeHeadList); FileInputStream inputStream = new FileInputStream(file); ObjectInputStream objectInputStream = new ObjectInputStream(inputStream); List reLoad = (List) objectInputStream.readObject(); //读取之后广度遍历第二次： forest.readForest(reLoad); //读取之后深度遍历： System.out.println(); forest.readForestDepthFirst(reLoad); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } } }

测试结果：