該程序使用遞歸算法通過遍歷打印二叉樹所有節點的值 InOrder 。

在中序遍歷中，先打印左子樹的值，然后是根和右子樹。

import java.util.Stack;
/*
 * Java Program to traverse a binary tree
 * using inorder traversal without recursion.
 * In InOrder traversal first left node is visited, followed by root
 * and right node.
 *
 * input:
 *      40
 *     /\
 *    20   50
 *   / \\
 *  10  30   60
 * /   /\
 * 5  67  78
 *
 * output: 5 10 20 30 40 50 60 67 78
 */
public class Main {
  public static void main(String[] args) throws Exception {
    // construct the binary tree given in question
    BinaryTree bt = BinaryTree.create();
    // traversing binary tree using InOrder traversal using recursion
    System.out
        .println("printing nodes of binary tree on InOrder using recursion");
    bt.inOrder();
  }
}
class BinaryTree {
  static class TreeNode {
    String data;
    TreeNode left, right;
    TreeNode(String value) {
      this.data = value;
      left = right = null;
    }
  }
  // root of binary tree
  TreeNode root;
  /**
   * traverse the binary tree on InOrder traversal algorithm
   */
  public void inOrder() {
    inOrder(root);
  }
  private void inOrder(TreeNode node) {
    if (node == null) {
      return;
    }
    inOrder(node.left);
    System.out.printf("%s ", node.data);
    inOrder(node.right);
  }
  /**
   * Java method to create binary tree with test data
   *
   * @return a sample binary tree for testing
   */
  public static BinaryTree create() {
    BinaryTree tree = new BinaryTree();
    TreeNode root = new TreeNode("40");
    tree.root = root;
    tree.root.left = new TreeNode("20");
    tree.root.left.left = new TreeNode("10");
    tree.root.left.left.left = new TreeNode("5");
    tree.root.left.right = new TreeNode("30");
    tree.root.right = new TreeNode("50");
    tree.root.right.right = new TreeNode("60");
    tree.root.left.right.left = new TreeNode("67");
    tree.root.left.right.right = new TreeNode("78");
    return tree;
  }
}
Output
printing nodes of binary tree on InOrder using recursion
5 10 20 30 67 78 40 50 60