概念性的东西，自行百度。

按照国际管理，直接上代码来分析。

1、Node节点类

package com.tree.thread;

/**

 * Author: lihao

 * Date：2017/8/30

 * Description:ThreadBinaryTree Node

 */

public class Node

{

    private int data;

    private Node left;

    private boolean leftIsThread;        // 左孩子是否为线索

    private Node right;

    private boolean rightIsThread;       // 右孩子是否为线索

    public Node(int data)

    {

        this.data = data;

        this.left = null;

        this.leftIsThread = false;

        this.right = null;

        this.rightIsThread = false;

    }

    public int getData()

    {

        return data;

    }

    public void setData(int data)

    {

        this.data = data;

    }

    public Node getLeft()

    {

        return left;

    }

    public void setLeft(Node left)

    {

        this.left = left;

    }

    public boolean isLeftIsThread()

    {

        return leftIsThread;

    }

    public void setLeftIsThread(boolean leftIsThread)

    {

        this.leftIsThread = leftIsThread;

    }

    public Node getRight()

    {

        return right;

    }

    public void setRight(Node right)

    {

        this.right = right;

    }

    public boolean isRightIsThread()

    {

        return rightIsThread;

    }

    public void setRightIsThread(boolean rightIsThread)

    {

        this.rightIsThread = rightIsThread;

    }

    @Override

    public boolean equals(Object obj)

    {

        if (obj instanceof Node)

        {

            Node temp = (Node) obj;

            if (temp.getData() == this.data)

            {

                return true;

            }

        }

        return false;

    }

    @Override

    public int hashCode()

    {

        return super.hashCode() + this.data;

    }

}

2、创建二叉树、二叉树中序线索化(线索化有3种，此处单讲中序)

package com.tree.thread;

public class ThreadTree {

    private Node root;         // 根节点

    private Node pre = null;   // 线索化的时候保存前驱

    public ThreadTree() {

        this.root = null;

        this.pre = null;

    }

    public ThreadTree(int[] data) {

        this.pre = null;

        this.root = createTree(data, 0);   // 创建二叉树

    }

    /**

     * 创建二叉树

     */

    public Node createTree(int[] data, int index) {

        if (index >= data.length) {

            return null;

        }

        Node node = new Node(data[index]);

        node.setLeft(createTree(data, 2 * index + 1));

        node.setRight(createTree(data, 2 * index + 2));

        return node;

    }

    /**

     * 将以root为根节点的二叉树线索化  中序法

     */

    public void inThread(Node root) {

        if (root != null) {

            inThread(root.getLeft());     // 线索化左孩子

            if (null == root.getLeft())   // 左孩子为空

            {

                root.setLeftIsThread(true);    // 将左孩子设置为线索

                root.setLeft(pre);

            }

            if (pre != null && null == pre.getRight())  // 右孩子为空

            {

                pre.setRightIsThread(true);

                pre.setRight(root);

            }

            pre = root;                 //每次将当前节点设置为pre

            inThread(root.getRight());       // 线索化右孩子

        }

    }

    /**

     * 中序遍历线索二叉树

     */

    public void inThreadList(Node root) {

        if (root == null) {

            return;

        }

        //查找中序遍历的起始节点

        while (root != null && !root.isLeftIsThread()) {

            root = root.getLeft();

        }

        while (root != null) {

            System.out.print(root.getData() + ",");

            if (root.isRightIsThread())   // 如果右孩子是线索

            {

                root = root.getRight();

            } else         // 有右孩子

            {

                root = root.getRight();

                while (root != null && !root.isLeftIsThread()) {

                    root = root.getLeft();

                }

            }

        }

    }

    /**

     * 中序遍历

     */

    public void inList(Node root) {

        if (root != null) {

            inList(root.getLeft());

            System.out.print(root.getData() + ",");

            inList(root.getRight());

        }

    }

    public Node getRoot() {

        return root;

    }

    public void setRoot(Node root) {

        this.root = root;

    }

}