首先用Node类定义一个节点，用来存储每个节点的内容：

public class Node {    // 关键字    private int keyData;        // 其他数据    private int otherData;        // 左子节点    private Node leftNode;        // 右子节点    private Node rightNode;    public Node(int keyData, int otherDate) {        this.keyData = keyData;        this.otherData = otherDate;    }    public int getKeyData() {        return keyData;    }    public void setKeyData(int keyData) {        this.keyData = keyData;    }    public Node getLeftNode() {        return leftNode;    }    public void setLeftNode(Node leftNode) {        this.leftNode = leftNode;    }    public int getOtherData() {        return otherData;    }    public void setOtherData(int otherData) {        this.otherData = otherData;    }    public Node getRightNode() {        return rightNode;    }    public void setRightNode(Node rightNode) {        this.rightNode = rightNode;    }    // 显示方法    public void display(){        System.out.println(keyData + "," + otherData);    }        }

然后定义一个Tree类，并用前序遍历、中序遍历和后序遍历

public class Tree {    // 根    private Node root;    // 插入方法    public void insert(int keyData, int otherData) {        Node newNode = new Node(keyData, otherData);        // 如果说没有节点        if (root == null) {            root = newNode;        } else {            Node current = root;            Node parent;            while (true) {                parent = current;                if (keyData < current.getKeyData()) {                    current = current.getLeftNode();                    if (current == null) {                        parent.setLeftNode(newNode);                        return;                    }                } else {                    current = current.getRightNode();                    if (current == null) {                        parent.setRightNode(newNode);                        return;                    }                }            }        }    }    // 查找方法    public Node find(int keyData) {        Node current = root;        while (current.getKeyData() != keyData) {            if (keyData < current.getKeyData()) {                current = current.getLeftNode();            } else {                current = current.getRightNode();            }            if (current == null) {                return null;            }        }        return current;    }    // 修改方法    public void change(int keyData, int newOtherData) {        Node findNode = find(keyData);        findNode.setOtherData(newOtherData);    }    // 先序遍历    public void preOrder(Node node) {        if (node != null) {            node.display();            preOrder(node.getLeftNode());            preOrder(node.getRightNode());        }    }    // 中序遍历    public void inOrder(Node node) {        if (node != null) {            inOrder(node.getLeftNode());            node.display();            inOrder(node.getRightNode());        }    }    // 后序遍历    public void endOrder(Node node) {        if (node != null) {            endOrder(node.getLeftNode());            endOrder(node.getRightNode());            node.display();        }    }    public Node getRoot() {        return root;    }}

测试:

Tree tree = new Tree();        tree.insert(80, 80);        tree.insert(49, 49);        tree.insert(42, 42);        tree.insert(30, 30);        tree.insert(45, 45);        tree.insert(90, 90);        tree.insert(150, 150);        tree.insert(130, 130);        tree.insert(82, 82);        System.out.println("前序遍历：");        tree.preOrder(tree.getRoot());        System.out.println("中序遍历：");        tree.inOrder(tree.getRoot());        System.out.println("后序遍历：");        tree.endOrder(tree.getRoot());