【发布时间】：2016-10-18 01:35:34
【问题描述】：
好的，这是一个简单的决策树，广度和深度优先搜索程序。在我的打印树方法中，我使用与搜索方法相同的元素转换过程，当我自己运行打印树方法时没有错误，当我取消注释我的搜索方法时，我在 main 中得到一个异常并且不能在深度优先和广度优先方法中都抛出异常，但树仍然打印。在我在方法中获得根子项后，异常特别来自演员表。我需要新的眼光，我对在 java 中使用 xml 是全新的，所以我把头发拉了出来。
xml：（评论说我错误地假设所有子节点都是元素，我实际上是假设所有节点都是节点，而不是元素并且它们可以转换为元素，抱歉）
<root>
<node behavior="Idle" response="">
<node behavior="" response="Use Computer"/>
<node behavior="" response="Patrol"/>
</node>
<node behavior="Incoming Projectile">
<node behavior="" response="Evade"/>
</node>
<node behavior="Combat" response="">
<node behavior="Melee" response="">
<node behavior="" response="Flee"/>
<node behavior="" response="Attack"/>
</node>
<node behavior="Ranged" response="">
<node behavior="" response="Weapon 1"/>
<node behavior="" response="Weapon 2"/>
<node behavior="" response="Weapon 3"/>
</node>
</node>
</root>
这是当我使用搜索运行打印树时程序的输出，就像我说的，如果我不使用它运行搜索，我不会得到第一个异常：
Specify BehaviorIdle
behavior= Idle
Exception in thread "main" response= Use Computer
response= Patrol
behavior= Incoming Projectile
response= Evade
behavior= Combat
behavior= Melee
response= Flee
response= Attack
behavior= Ranged
response= Weapon 1
response= Weapon 2
response= Weapon 3
java.lang.ClassCastException:com.sun.org.apache.xerces.internal.dom.DeferredTextImpl cannot be cast to org.w3c.dom.Element
at XmlTree.breadthFirst(XmlTree.java:58)
at decisiontree.main(decisiontree.java:34)
主要：
import java.util.*;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class decisiontree {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
ArrayList <org.w3c.dom.Node> queue = new ArrayList<org.w3c.dom.Node>();
int dCounter = 0;
int bCounter = 0;
System.out.print("Type in path for xml file: ");
String path = scan.nextLine();
System.out.print("Specify Behavior");
String target = scan.nextLine();
scan.close();
XmlTree dTree = new XmlTree();
Document doc =dTree.xmlIn(path);
NodeList thisList = doc.getElementsByTagName("root");
Node root = thisList.item(0);
dTree.printTree(doc);
String dResponse = dTree.depthFirst(root, target, dCounter);
String bResponse = dTree.breadthFirst(root, queue, target, bCounter);
System.out.println("Behavior: "+ target +"\n"+"Depth First Response: " + dResponse +
"\n" + "Breadth First Response: "+ bResponse + "\n" + "Depth First Took "+
dCounter + " jumps"+"\n"+"Breadth First Took "+ bCounter +" jumps");
}
}
打印树：
public void printTree(Document doc){
NodeList rootList = doc.getElementsByTagName("root");
org.w3c.dom.Node root = rootList.item(0);
Element rootElement = (Element) root;
NodeList nodeList = rootElement.getElementsByTagName("node");
for(int i = 0; i < nodeList.getLength(); i++){
org.w3c.dom.Node nodes = nodeList.item(i);
Element nodeElement = (Element) nodes;
if(nodeElement.getAttribute("behavior") != ""){
if(nodeElement.getParentNode() != rootElement){
System.out.println(" behavior= " + nodeElement.getAttribute("behavior"));
}else{
System.out.println("behavior= " + nodeElement.getAttribute("behavior"));
}
}else if(nodeElement.getAttribute("behavior") == ""){
if(nodeElement.getParentNode() != rootElement.getChildNodes()){
System.out.println(" response= " + nodeElement.getAttribute("response"));
}else{
System.out.println(" response= " + nodeElement.getAttribute("response"));
}
}
}
}
深度优先：
public String depthFirst(org.w3c.dom.Node root, String target, int dCounter){
if (root.getChildNodes() == null){
return "no tree";
}
dCounter++;
NodeList nL = root.getChildNodes();
for(int i = 0;i < nL.getLength();i++){
org.w3c.dom.Node node = nL.item(i);
Element nodeElement = (Element) node; //ERROR ON THIS LINE
if(nodeElement.getAttribute("behavior") == target){
while(nodeElement.hasChildNodes()){
NodeList newNL = nodeElement.getChildNodes();
Random rand = new Random();
int x = rand.nextInt(newNL.getLength());
node = newNL.item(x);
Element newElement = (Element) node;
nodeElement = newElement;
dCounter++;
}
String response = nodeElement.getAttribute("response");
return response;
}else{
depthFirst(node, target, dCounter);
}
}
return null;
}
广度优先：
public String breadthFirst(Node root, ArrayList<org.w3c.dom.Node> q, String target, int bCounter){
if(!root.hasChildNodes()){
return "no tree";
}
bCounter++;
NodeList nL = root.getChildNodes();
for(int i = 0; i < nL.getLength(); i++){
q.add(nL.item(i));
}
Node node = q.get(0);
Element nodeElement = (Element) node; // ERROR ON THIS LINE
if(nodeElement.getAttribute("behavior") != target){
q.remove(0);
Node newNode = q.get(0);
Element newElement = (Element) newNode;
breadthFirst(newElement, q, target, bCounter);
}
if(nodeElement.getAttribute("behavior") == target){
while(nodeElement.hasChildNodes()){
NodeList newNL = node.getChildNodes();
Random rand = new Random();
int x = rand.nextInt(newNL.getLength());
Element newElement = (Element) newNL.item(x);;
nodeElement = newElement;
bCounter++;
}
String response = nodeElement.getAttribute("response");
return response;
}
return null;
}
【问题讨论】：
-
您错误地假设
<root>的所有子节点都是元素节点。如果您想了解其他子节点是什么，请编辑您的问题并包含您正在阅读的 XML。
标签： java xml dom elements decision-tree