一个简单高效的禁词过滤类

使用方法：

public static void main(String[] args) {
		  SimpleTreeFilter filter = new SimpleTreeFilter();
		  filter.addKeyword("禁词1");
		  filter.addKeyword("禁词2");
		  filter.addKeyword("其它禁词");
		  
		  System.out.println(filter.contains("我是合法的"));
		  System.out.println(filter.contains("我包含禁词1"));
		  System.out.println(filter.contains("我包含禁词2"));
		  System.out.println(filter.contains("我包含其它禁词1"));
		  System.out.println(filter.contains("来个别的吧"));
		  System.out.println(filter.contains("再见"));
	}

输出：
null
禁词1
禁词2
其它禁词
null
null

import java.util.HashMap;

public class SimpleTreeFilter{

	public class TreeNode{
		public char c;
		public HashMap<Character, TreeNode> next;
		public boolean isEnd=false;
	}
	HashMap<Character, TreeNode> head = new HashMap<Character, TreeNode>();
	
	public void addKeyword(String word) {
		word=word.toLowerCase();
		int len = word.length();
		if(len==0){
			return;
		}
		char firstChar = word.charAt(0);
		TreeNode node;
		if(head.containsKey(firstChar)){
			node = head.get(firstChar);
		}else{
			node = new TreeNode();
			node.c=firstChar;
			head.put(firstChar, node);
		}	
		for(int i=1;i<len;i++){
			char c=word.charAt(i);
			if(node.next==null){
				node.next = new HashMap<Character, TreeNode>();
			}
			if(node.next.containsKey(c)){
				node = node.next.get(c);
			}else{
				TreeNode tNode = new TreeNode();
				tNode.c=c;
				node.next.put(c, tNode);
				node = tNode;
			}
		}
		node.isEnd=true;
	}

	public String contains(String line) {
		int len = line.length();
		line=line.toLowerCase();
		for(int i=0;i<len;i++){
			char c=line.charAt(i);
			if(head.containsKey(c)){
				TreeNode node = head.get(c);
				if(node.isEnd==true){
					return (c+"").toLowerCase();
				}
				int j=i+1;
				while(j<len){
					char cTemp = line.charAt(j);
					if(node.next.containsKey(cTemp)){
						node = node.next.get(cTemp);
						if(node.isEnd==true){
							return line.substring(i,j+1).toLowerCase();
						}
					}else{
						break;
					}
					j++;
				}
			}
		}
		return null;
	}	
}