## 節點
```java
/**
* @author virus
* @date 2020/11/30
*/
public class Node {
private int data;
private Node leftNode;
private Node rightNode;
public Node(int data, Node leftNode, Node rightNode) {
this.data = data;
this.leftNode = leftNode;
this.rightNode = rightNode;
}
public int getData() {
return data;
}
public void setData(int data) {
this.data = data;
}
public Node getLeftNode() {
return leftNode;
}
public void setLeftNode(Node leftNode) {
this.leftNode = leftNode;
}
public Node getRightNode() {
return rightNode;
}
public void setRightNode(Node rightNode) {
this.rightNode = rightNode;
}
}
```
## 遞歸遍歷
```java
/**
* @author virus
* @date 2020/11/30
*/
public class BinaryTree {
private Node init() {
Node J = new Node(8, null, null);
Node H = new Node(4, null, null);
Node G = new Node(2, null, null);
Node F = new Node(7, null, J);
Node E = new Node(5, H, null);
Node D = new Node(1, null, G);
Node C = new Node(9, F, null);
Node B = new Node(3, D, E);
Node A = new Node(6, B, C);
// 返回根節點
return A;
}
private void printNode(Node node) {
System.out.print(node.getData());
}
/**
* 先(根)序遍歷(根左右)
*
* @param root
*/
private void theFirstTraversal(Node root) {
printNode(root);
// 使用遞歸進行遍歷左孩子
if (root.getLeftNode() != null) {
theFirstTraversal(root.getLeftNode());
}
// 遞歸遍歷右孩子
if (root.getRightNode() != null) {
theFirstTraversal(root.getRightNode());
}
}
/**
* 中(根)序遍歷(左根右)
*
* @param root
*/
private void theInOrderTraversal(Node root) { //中序遍歷
if (root.getLeftNode() != null) {
theInOrderTraversal(root.getLeftNode());
}
printNode(root);
if (root.getRightNode() != null) {
theInOrderTraversal(root.getRightNode());
}
}
/**
* 后(根)序遍歷(左右根)
*
* @param root
*/
private void thePostOrderTraversal(Node root) { //后序遍歷
if (root.getLeftNode() != null) {
thePostOrderTraversal(root.getLeftNode());
}
if (root.getRightNode() != null) {
thePostOrderTraversal(root.getRightNode());
}
printNode(root);
}
public static void main(String[] args) {
BinaryTree tree = new BinaryTree();
Node root = tree.init();
System.out.println("先序遍歷");
tree.theFirstTraversal(root);
System.out.println("");
System.out.println("中序遍歷");
tree.theInOrderTraversal(root);
System.out.println("");
System.out.println("后序遍歷");
tree.thePostOrderTraversal(root);
System.out.println("");
}
}
```
