如何按順序打印我的二叉樹

Question

我相信我的inOrderTraverseTree()方法將樹按順序排列，但我不確定如何按順序實際打印樹。 有什么建議么？ 為什么該方法不能按原樣打印出來？ 謝謝，扎克

    public class Tree 
        {
    Node root;
    public static void main(String[] args){
        Tree t = new Tree();
        t.addNode("hey");
        t.addNode("fghjk");
        t.addNode("aaaaaa");
        t.addNode("zzzzzz");
        t.addNode("egh");
        t.addNode("rrrrrr");
        t.inOrderTraverseTree(t.root);



    }

    public void displayTree(){
        Node link = root;

        while(link != null){


        }
    }
    public void addNode(String line){

        //Create a new Node and initialize it
        Node newNode = new Node(line);

        //If there is no root this becomes root

        if(root == null){
            root = newNode;
        } else {

            //Set root as the Node we will start
            //with as we traverse the tree

            Node focusNode = root;

            // Future parent for our new Node

            Node parent;

            while(true){

                // root is the top parent so we start there

                parent = focusNode;

                //Check if the new Node should go on the left 
                //side of the parent node

                if(line.compareTo(focusNode.line) == -1){

                    focusNode = focusNode.leftChild;

                    //If the left child has no children

                    if(focusNode == null){
                        parent.leftChild = newNode;
                        return; //All Done
                    }

                } else { // If we get here put the node on the right

                    focusNode = focusNode.rightChild;

                    //If the right child has no children

                    if(focusNode == null){

                        //then place the node on the right of it

                        parent.rightChild = newNode;
                        return; //All Done
                    }

                }
            }
        }

    }

    public void inOrderTraverseTree(Node focusNode)
    {
        if(focusNode != null){

            //traverse the left node

            inOrderTraverseTree(focusNode.leftChild);

            //Visit the currently focused on node

            System.out.println(focusNode);

            //Traverse the right node 

            inOrderTraverseTree(focusNode.rightChild);

        }
    }
    class Node {

        String line;

        Node leftChild;
        Node rightChild;

        Node(String line){
            this.line = line;
        }

        //this method overrides toString in Object class
        public String toString(){
            return line;
        }

    }


}

Answer 1

該錯誤在addNode（）的這一行中：

if(line.compareTo(focusNode.line) == -1){
.
.

更改為：

if(line.compareTo(focusNode.line) < 0){
.
.

在此處查看有關返回值的更多詳細信息：

http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#compareTo%28java.lang.String%29

和

字符串比較到實際返回值

其余的代碼對我來說看起來不錯。