java遍历二叉树

public class BTNode {
	private char key;
	private BTNode left,right;
	public BTNode(char key) {
		// TODO Auto-generated constructor stub
		this(key,null,null);
	}
	public BTNode(char key, BTNode left, BTNode right) {
		// TODO Auto-generated constructor stub
		this.key = key;
		this.left = left;
		this.right = right;
	}
	public char getKey() {
		return key;
	}
	public void setKey(char key) {
		this.key = key;
	}
	public BTNode getLeft() {
		return left;
	}
	public void setLeft(BTNode left) {
		this.left = left;
	}
	public BTNode getRight() {
		return right;
	}
	public void setRight(BTNode right) {
		this.right = right;
	}
	
}

import java.util.Stack;

public class BinTree {
	protected BTNode root;
	public BinTree(BTNode root) {
		this.root = root;
	}
	public BTNode getRoot() {
		return root;
	}
	/**构造树*/
	public static BTNode init() {
		BTNode a = new BTNode('A');
		BTNode b = new BTNode('B',null,a);
		BTNode c = new BTNode('C');
		BTNode d = new BTNode('D',b,c);
		BTNode e = new BTNode('E');
		BTNode f = new BTNode('F',e,null);
		BTNode g = new BTNode('G',null,f);
		BTNode h = new BTNode('H',d,g);
		// return root;
		return h;
	}
	/**访问节点*/
	public static void visit(BTNode p) {
		System.out.print(p.getKey() + "");
	}
	/** 递归实现前序遍历 */
	protected static void preorder(BTNode p) {
		if(p != null) {
			visit(p);
			preorder(p.getLeft());
			preorder(p.getRight());
		}
	}
	/**递归实现中序遍历*/
	protected static void inorder(BTNode p) {
		if(p != null) {
			inorder(p.getLeft());
			visit(p);
			inorder(p.getRight());
		}
	}
	/**递归实现后序遍历*/
	protected static void postorder(BTNode p) {
		if(p!= null) {
			postorder(p.getLeft());
			postorder(p.getRight());
			visit(p);
		}
	}
	/**非递归实现前序遍历*/
	protected static void iterativePreorder(BTNode p) {
		Stack<BTNode> stack = new Stack<BTNode>();
		if(p != null) {
			stack.push(p);
			while (!stack.empty()) {
				p = stack.pop();
				visit(p);
				if(p.getRight() != null) {
					stack.push(p.getRight());
				if(p.getLeft() != null)
					stack.push(p.getLeft());
				}
			}
		}
	}
	/** 非递归实现后序遍历 */ 
	protected static void iterativePostorder(BTNode p) {
		BTNode q = p;
		Stack<BTNode> stack = new Stack<BTNode>();
		while(p != null) {
			// 左子树入栈 
			for(;p.getLeft()!=null;p=p.getLeft()) {
				stack.push(p);
			}
			//当前节点无右子或右子已经输出
			while(p != null && (p.getRight() == null || p.getRight() == q)) {
				visit(p);
				q = p;	//记录上一个已输出节点
				if(stack.empty()) {
					return ;
				}
				p = stack.pop();
			}
			//处理右子
			stack.push(p);
			p = p.getRight();
		}
	} 
	/**非递归实现中序遍历*/
	protected static void iterativeInorder(BTNode p) {
		Stack<BTNode> stack = new Stack<BTNode>();
		while(p != null) {
			if(p.getRight() != null){
				stack.push(p.getRight());//当前节点右子入栈
			}
			stack.push(p);	//当前节点入栈
			p = p.getLeft();
		}
		p = stack.pop();
		while(!stack.empty() && p.getRight() == null) {
			visit(p);
			p = stack.pop();
		}
		visit(p);
		if(!stack.empty())
			p = stack.pop();
		else 
			p = null;
	}
	public static void main(String[] args) {
		BinTree tree = new BinTree(init());
		//递归实现前序遍历
		System.out.print("递归先序遍历:");
		preorder(tree.getRoot());
		System.out.println();
		//递归实现中序遍历
		System.out.print("递归中序遍历：");
		inorder(tree.getRoot());
		System.out.println();
		//递归实现后序遍历
		System.out.print("递归后序遍历：");
		postorder(tree.getRoot());
		System.out.println();
	}
}