栈实现HTML和UBB的转换

package com.test;

import java.util.Stack;

public class Test {
class Node {
int start;
int end;
String tagName;
}
/**
* 忽略了匹配细节，实现html解析
* @param html html
* @return
*/
public String ubb(String html){
StringBuffer result = new StringBuffer();
int pos = -1;//标记每个开始标签符号位置
Stack<Node> tagStack = new Stack<Node>();
int len = html.length();
for(int i = 0; i < len; i++){
switch(html.charAt(i)){
case '<':
pos = i;
break;
case '>':
if(pos != -1){
Node node = new Node();
node.start = pos;
node.end = i + 1;
node.tagName = html.substring(pos + 1, i);
if(tagStack.isEmpty() || !tagStack.peek().tagName.equals(node.tagName)){
tagStack.push(node);
}else{
Node startNode = tagStack.pop();
System.out.println(html.substring(startNode.start, i + 1));
}
pos = -1;
}
break;
}
}
return result.toString();
}
public static void main(String[] args) throws Exception {
System.out.println(new Test().ubb("<a><b>asdf<b><a>"));
}
}