用java实现二叉树遍历

public class BinaryTree {// design node for treepublic void printNode(TreeNode node) {System.out.print(node.getData());}class TreeNode {private String data;private TreeNode leftNode;private TreeNode rightNode;public TreeNode(String data, TreeNode leftNode, TreeNode rightNode) {this.data = data;this.leftNode = leftNode;this.rightNode = rightNode;}public String getData() {return data;}public void setData(String data) {this.data = data;}public TreeNode getLeftNode() {return leftNode;}public void setLeftNode(TreeNode leftNode) {this.leftNode = leftNode;}public TreeNode getRightNode() {return rightNode;}public void setRightNode(TreeNode rightNode) {this.rightNode = rightNode;}}public static void main(String[] args) {BinaryTree tree = new BinaryTree();TreeNode node = tree.init();// 先序遍历。。。。。。。System.out.println("**************************");System.out.println("先序遍历。。。。。。。");tree.xianIterator(node);System.out.println("");// 中序遍历。。。。。。。System.out.println("**************************");System.out.println("中序遍历。。。。。。。");tree.zhongIterator(node);System.out.println("");// 后续遍历。。。。。。。System.out.println("**************************");System.out.println("后序遍历。。。。。。。");tree.houIterator(node);}public TreeNode init() {TreeNode D = new TreeNode("D", null, null);TreeNode H = new TreeNode("H", null, null);TreeNode I = new TreeNode("I", null, null);TreeNode J = new TreeNode("J", null, null);TreeNode P = new TreeNode("P", null, null);TreeNode G = new TreeNode("G", P, null);TreeNode F = new TreeNode("F", null, J);TreeNode E = new TreeNode("E", H, I);TreeNode B = new TreeNode("B", D, E);TreeNode C = new TreeNode("C", F, G);TreeNode A = new TreeNode("A", B, C);return A;}public void xianIterator(TreeNode node) {this.printNode(node);if (node.getLeftNode() != null) {this.xianIterator(node.getLeftNode());}if (node.getRightNode() != null) {this.xianIterator(node.getRightNode());}}public void zhongIterator(TreeNode node) {if (node.getLeftNode() != null) {this.zhongIterator(node.getLeftNode());}this.printNode(node);if (node.getRightNode() != null) {this.zhongIterator(node.getRightNode());}}public void houIterator(TreeNode node) {if (node.getLeftNode() != null) {this.houIterator(node.getLeftNode());}if (node.getRightNode() != null) {this.houIterator(node.getRightNode());}this.printNode(node);}}