二叉查找树的实现（插入+递归调用）

package BinaryTree;


public class BinarySearchTree {

	public TreeNode root;
	public BinarySearchTree(){
		//root=new TreeNode(1,"A");
		//root=null;
	} 
	
	private class TreeNode{
		private int key;
		private String data;
		private TreeNode leftChild;
		private TreeNode rightChild;
		
		public TreeNode(int key,String data){
			this.key=key;
			this.data=data;
			this.leftChild=null;
			this.rightChild=null;
		}
	}
	public TreeNode getTreeNode(int key,String data){
		return new TreeNode(key,data);
	}
	
	

	private void insert(TreeNode node){
		root=insert(root,node);
	}
	public TreeNode insert(TreeNode subTree,TreeNode node){
		if(node==null){  //不可插入null
			return null;
		}
		if(subTree==null){  //根节点为空，插入
			subTree=node;
		}else{
			if(node.key<subTree.key){//比根节点小？ 插左边
				subTree.leftChild=insert(subTree.leftChild,node);
			}else{ //否则，插右边
				subTree.rightChild=insert(subTree.rightChild,node);
			}
		}
		return subTree;
	}
	/**
	 * 前序遍历
	 *  先访问根节点，再分别访问其左、右子树
	 * @param subTree
	 */
	public void preOrder(){
		preOrder(root);
	}
	private void preOrder(TreeNode subTree){
		if(subTree!=null){
			System.out.println("key:"+subTree.key+"--name:"+subTree.data);
			preOrder(subTree.leftChild);
			preOrder(subTree.rightChild);
		}
	}
	
	/**
	 * 中序遍历
	 *  根节点的遍历在其左、右子树之间
	 * @param subTree
	 */
	public void inOrder(){
		inOrder(root);
	}
	public void inOrder(TreeNode subTree){
		if(subTree!=null){
			inOrder(subTree.leftChild);
			System.out.println("key:"+subTree.key+"--name:"+subTree.data);
			inOrder(subTree.rightChild);
		}
	}		
	/**
	 * 后序遍历
	 * 访问根节点在遍历其左右子树之后
	 * @param subTree
	 */
	public void postOrder(){
		postOrder(root);
	}
	public void postOrder(TreeNode subTree){
		if(subTree!=null){
			postOrder(subTree.leftChild);
			postOrder(subTree.rightChild);
			System.out.println("key:"+subTree.key+"--name:"+subTree.data);
		}
	}
	
	public static void main(String[] args) {

		BinarySearchTree bst=new BinarySearchTree();
		
		
		bst.insert(bst.getTreeNode(4, "D"));
		bst.insert(bst.getTreeNode(1, "A"));
		bst.insert(bst.getTreeNode(2, "B"));
		bst.insert(bst.getTreeNode(5, "E"));
		bst.insert(bst.getTreeNode(3, "C"));
		
		sop("前序遍历");
		bst.preOrder();
		sop("中序遍历：结果为从小到大");
		bst.inOrder();
		sop("后序遍历");
		bst.postOrder();
		
	}

	public static void sop(Object o){
		System.out.println(o);
	}

}