最近有人老是问我在Java中如何实现Tree的数据结构算法，今天在网上看了一篇关于这方面的代码，拿出来和大家分享一下吧！

代码实现[一]部分

package ChapterEight;

class Tree {

class Node {

public long value;

public Node leftChild;

public Node rightChild;

public Node(long value) {

this.value = value;

leftChild = null;

rightChild = null;

}

}

public Node root;

public Tree() {

root = null;

}

// 向树中插入一个节点

public void insert(long value) {

Node newNode = new Node(value);

// 树是空的

if (root == null)

root = newNode;

else {

Node current = root;

Node parentNode;

while (true) {

parentNode = current;

if (value < current.value) {

current = current.leftChild;

// 要插入的节点为左孩子节点

if (current == null) {

parentNode.leftChild = newNode;

return;

}

} else {

// 要插入的节点为右孩子节点

current = current.rightChild;

if (current == null) {

parentNode.rightChild = newNode;

return;

}

}

}

}

}

// 先续遍历树中的所有节点

public void preOrder(Node currentRoot) {

if (currentRoot != null) {

System.out.print(currentRoot.value + " ");

preOrder(currentRoot.leftChild);

preOrder(currentRoot.rightChild);

}

}

// 中续遍历树中的所有节点

public void inOrder(Node currentNode) {

if (currentNode != null) {

inOrder(currentNode.leftChild);

System.out.print(currentNode.value + " ");

inOrder(currentNode.rightChild);

}

}

// 后续遍历树中的所有节点

public void postOrder(Node currentNode) {

if (currentNode != null) {

postOrder(currentNode.leftChild);

postOrder(currentNode.rightChild);

System.out.print(currentNode.value + " ");

}

}

public void traverse(int traverseType) {

switch (traverseType) {

case 1:

preOrder(root);

break;

case 2:

inOrder(root);

break;

case 3:

postOrder(root);

break;

default:

break;

}

// 依据树节点的值删除树中的一个节点

public boolean delete(int value) {

// 遍历树过程中的当前节点

Node current = root;

// 要删除节点的父节点

Node parent = root;

// 记录树的节点为左孩子节点或右孩子节点

boolean isLeftChild = true;

while (current.value != value) {

parent = current;

// 要删除的节点在当前节点的左子树里

if (value < current.value) {

isLeftChild = true;

current = current.leftChild;

}

// 要删除的节点在当前节点的右子树里

else {

isLeftChild = false;

current = current.rightChild;

}

// 在树中没有找到要删除的节点

if (current == null)

return false;

}

// 要删除的节点为叶子节点

if (current.leftChild == null && current.rightChild == null) {

// 要删除的节点为根节点

if (current == root)

root = null;

// 要删除的节点为左孩子节点

else if (isLeftChild)

parent.leftChild = null;

// 要删除的节点为右孩子节点

else

parent.rightChild = null;

}

// 要删除的节点有左孩子节点，没有右孩子节点

else if (current.rightChild == null) {

// 要删除的节点为根节点

if (current == null)

root = current.leftChild;

// 要删除的节点为左孩子节点

else if (isLeftChild)

parent.leftChild = current.leftChild;

// 要删除的节点为右孩子节点

else

parent.rightChild = current.leftChild;

}

// 要删除的节点没有左孩子节点，有右孩子节点

else if (current.leftChild == null) {

// 要删除的节点为根节点

if (current == root)

root = root.rightChild;

// 要删除的节点为左孩子节点

else if (isLeftChild)

parent.leftChild = current.rightChild;

// 要删除的节点为右孩子节点

else

parent.rightChild = current.rightChild;

}

// 要删除的接节点既有左孩子节点又有右孩子节点

else {

Node successor = getSuccessor(current);

// 要删除的节点为根节点

if (current == root)

root = successor;

// 要删除的节点为左孩子节点

else if (isLeftChild)

parent.leftChild = successor;

// 要删除的节点为右孩子节点

else

parent.rightChild = successor;

}

return true;

}

// 找到要删除节点的替补节点

private Node getSuccessor(Node delNode) {

// 替补节点的父节点

Node successorParent = delNode;

// 删除节点的替补节点

Node successor = delNode;

Node current = delNode.rightChild;

while (current != null) {

// successorParent指向当前节点的上一个节点

successorParent = successor;

// successor变为当前节点

successor = current;

current = current.leftChild;

}

// 替补节点的右孩子节点不为空

if (successor != delNode.rightChild) {

successorParent.leftChild = successor.rightChild;

successor.rightChild = delNode.rightChild;

}

return successor;

}

}

public class TreeApp {

public static void main(String[] args) {

Tree tree = new Tree();

tree.insert(8);

tree.insert(50);

tree.insert(45);

tree.insert(21);

tree.insert(32);

tree.insert(18);

tree.insert(37);

tree.insert(64);

tree.insert(88);

tree.insert(5);

tree.insert(4);

tree.insert(7);

System.out.print("PreOrder : ");

tree.traverse(1);

System.out.println();

System.out.print("InOrder : ");

tree.traverse(2);

System.out.println();

System.out.print("PostOrder : ");

tree.traverse(3);

System.out.println();

System.out.println(tree.delete(7));

System.out.print("PreOrder : ");

tree.traverse(1);

System.out.println();

System.out.print("InOrder : ");

tree.traverse(2);

System.out.println();

System.out.print("PostOrder : ");

tree.traverse(3);

System.out.println();

}

}