java编写二叉树以及前序遍历、中序遍历和后序遍历 .

/**
 * 实现二叉树的创建、前序遍历、中序遍历和后序遍历
 **/
package DataStructure;

/**
 * Copyright 2014 by Ruiqin Sun
 * All right reserved
 * created  on 2014-9-9 下午2:34:15
 **/
public class BinTreeInt {
	private Node root;
	
	/**
	 * 创建内部节点类
	 **/
	private class Node{
//		左节点
		private Node leftChild;
//		右节点
		private Node rightChild;
//		节点对应的值
		private int data;
		
		public Node(int data){
			this.leftChild = null;
			this.rightChild = null;
			this.data = data;
		}
	}// class Node
	
	public BinTreeInt(){
		root = null;
	}
	
	/*
	 *递归的创建二叉树
	 * */
	public void buildTree(Node node ,int data){
		if (root == null){// 如果根节点为空，创建根节点
			root = new Node(data);
		}else{
			if(data <node.data){//插入到左子树
				if(node.leftChild == null){//左节点为空，直接创建值为data的左节点
					node.leftChild = new Node(data);
				}else{//左节点不为空，调用buildTree函数插到左子树中
					buildTree(node.leftChild,data);
				}
			}else{
				if(node.rightChild == null){
					node.rightChild = new Node(data);
				}else{
					buildTree(node.rightChild,data);
				}
			}		
		}
	}//end buildTree
	/*
	 *前序遍历二叉树
	 * */
	public void preOrder(Node node){
		if(node != null){
			System.out.print(node.data);
			preOrder(node.leftChild);
			preOrder(node.rightChild);
		}
	}
	/*
	 *中序遍历二叉树
	 * */
	public void inOrder(Node node){
		if(node != null){
			inOrder(node.leftChild);
			System.out.print(node.data);
			inOrder(node.rightChild);
		}
	}
	/*
	 *后序遍历二叉树
	 * */
	public void postOrder(Node node){
		if(node != null){
			postOrder(node.leftChild);
			postOrder(node.rightChild);
			System.out.print(node.data);			
		}
	}
	
	public static void main(String ars[]){
		int[] a={2,4,12,45,21,6,111};
		BinTreeInt binTree = new BinTreeInt();
		for(int i = 0; i<a.length; i++){
			binTree.buildTree(binTree.root, a[i]);
		}
		System.out.print("前序遍历");
		binTree.preOrder(binTree.root);
		System.out.println("");
		System.out.print("中序遍历");
		binTree.inOrder(binTree.root);
		System.out.println("");
		System.out.print("后序遍历");
		binTree.postOrder(binTree.root);
	}
}