二叉树的遍历方式有多种，前序遍历为其中一种，前序遍历的方式是按照根---左--右的顺序遍历的，即先遍历完所有的根，再遍历左，最后遍历右子树，如下图

前序遍历的理想结果是： 10, 6, 4, 8, 14, 12, 16

下面使用代码来实现上面的遍历，代码分别使用递归和非递归的方法实现，两者输出的结果一致

package com.silverbox.user.web.htmdemo;import java.util.ArrayList;import java.util.List;import java.util.Stack;/** * 二叉树的前序遍历的非递归和递归的实现 *  * @author ssj * */public class PreList {	public static void main(String[] args) {		// 创建一颗二叉树		TreeNode root = new TreeNode("10");		TreeNode n6 = new TreeNode("6");		TreeNode n14 = new TreeNode("14");		n6.setParent(root);		n14.setParent(root);		root.setLeft(n6);		root.setRight(n14);		TreeNode n4 = new TreeNode("4");		TreeNode n8 = new TreeNode("8");		n6.setLeft(n4);		n6.setRight(n8);		TreeNode n12 = new TreeNode("12");		TreeNode n16 = new TreeNode("16");		n14.setLeft(n12);		n14.setRight(n16);		System.out.println("---------递归遍历结果--------------------");		List list = new ArrayList();		preListDiGui(root, list);		System.out.println(list);						System.out.println("---------非递归遍历结果--------------------");		List list2 = preList(root);		System.out.println(list2);	}	/**	 * 递归前序遍历	 * 	 * @param root	 * @return	 */	public static void preListDiGui(TreeNode root, List list) {		if (root == null) {			return;		}		list.add(root.name);		preListDiGui(root.left, list);		preListDiGui(root.right, list);	}	/**	 * 非递归前序遍历	 * 	 * @param root	 * @return	 */	public static List preList(TreeNode root) {		Stack<TreeNode> sk = new Stack<TreeNode>();		List list = new ArrayList();		TreeNode n = root;		while (n != null) {			// 从当前节点开始，一直往左方向前进			while (n != null) {				// 输出当前节点				list.add(n.getName());				if (n.right != null) {					// 遇到右节点，入栈					sk.push(n.right);				}				n = n.left;			}			// 取出入栈的右节点			while (!sk.empty()) {				TreeNode n2 = sk.pop();				list.add(n2.getName());				if (n2.right != null) {					sk.push(n2.right);				}				// 如果该节点存在左节点，先输出所有的左节点，即重复以上过程				if (n2.left != null) {					n = n2.left;					break;				}			}		}		return list;	}}/** * 树节点 * @author ssj * */class TreeNode {	public String name;	public TreeNode left;	public TreeNode right;	public TreeNode parent = null;	public boolean visitor=false;//标记该节点是否访问过	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public TreeNode getParent() {		return parent;	}	public void setParent(TreeNode parent) {		this.parent = parent;	}	public TreeNode(String name) {		super();		this.name = name;	}	public TreeNode getLeft() {		return left;	}	public void setLeft(TreeNode left) {		this.left = left;	}	public TreeNode getRight() {		return right;	}	public void setRight(TreeNode right) {		this.right = right;	}}

运行结果