java实现二叉树遍历

package test;

public class Node {
	protected char key;
	protected Node left,right;
	public Node(){
		left=right=null;
	}
	public Node(char key){
		this(key, null, null);
	}
	public Node(char key,Node left,Node right){
		this.key=key;
		this.left=left;
		this.right=right;
	}

	public char getKey(){
		return this.key;
	}
	public void visit(){
		System.out.print(getKey()+", ");
	}
	public static void preOrderTraverse(Node t){//先序遍历
		t.visit();
		if(t.left!=null)
			preOrderTraverse(t.left);
		if(t.right!=null)
			preOrderTraverse(t.right);
	}
	public static void InOrderTraverse(Node t){//中序遍历
		if(t.left!=null)
			InOrderTraverse(t.left);
		t.visit();
		if(t.right!=null){
			InOrderTraverse(t.right);
		}
	}
	public static void PostOrderTraverse(Node t){//后序遍历
		if(t.left!=null)
			PostOrderTraverse(t.left);
		if(t.right!=null)
			PostOrderTraverse(t.right);
		t.visit();
	}
	public static void main(String[] args){
			Node g=new Node('g');
			Node e=new Node('e');
			Node f=new Node('f');
			Node d=new Node('d',g,null);
			Node b=new Node('b',null,d);
			Node c=new Node('c',e,f);
			Node a=new Node('a',b,c);
			System.out.print("PreOrderTraverse: ");
			Node.preOrderTraverse(a);
			System.out.println();
			System.out.print("InOrderTraverse: ");
			Node.InOrderTraverse(a);
			System.out.println();
			System.out.print("PostOrderTraverse: ");
			Node.PostOrderTraverse(a);
	}
}