java敏感词过滤-使用HashMap实现DFA算法

转载：http://blog.shilimin.com/298.htm

package arrayDemo;


import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Set;


@SuppressWarnings( { "rawtypes", "unchecked" })
public class KeywordFilter {
/** 直接禁止的 */
private HashMap keysMap = new HashMap();
private int matchType = 1; // 1:最小长度匹配 2：最大长度匹配


public void addKeywords(List<String> keywords) {
for (int i = 0; i < keywords.size(); i++) {
String key = keywords.get(i).trim();
HashMap nowhash = null;
nowhash = keysMap;
for (int j = 0; j < key.length(); j++) {
char word = key.charAt(j);
Object wordMap = nowhash.get(word);
if (wordMap != null) {
nowhash = (HashMap) wordMap;
} else {
HashMap<String, String> newWordHash = new HashMap<String, String>();
newWordHash.put("isEnd", "0");
nowhash.put(word, newWordHash);
nowhash = newWordHash;
}
if (j == key.length() - 1) {
nowhash.put("isEnd", "1");
}
}
}
}


/**
* 重置关键词
*/
public void clearKeywords() {
keysMap.clear();
}


/**
* 检查一个字符串从begin位置起开始是否有keyword符合， 如果有符合的keyword值，返回值为匹配keyword的长度，否则返回零
* flag 1:最小长度匹配 2：最大长度匹配
*/
private int checkKeyWords(String txt, int begin, int flag) {
HashMap nowhash = null;
nowhash = keysMap;
int maxMatchRes = 0;
int res = 0;
int l = txt.length();
char word = 0;
for (int i = begin; i < l; i++) {
word = txt.charAt(i);
Object wordMap = nowhash.get(word);
if (wordMap != null) {
res++;
nowhash = (HashMap) wordMap;
if (((String) nowhash.get("isEnd")).equals("1")) {
if (flag == 1) {
wordMap = null;
nowhash = null;
txt = null;
return res;
} else {
maxMatchRes = res;
}
}
} else {
txt = null;
nowhash = null;
return maxMatchRes;
}
}
txt = null;
nowhash = null;
return maxMatchRes;
}


/**
* 返回txt中关键字的列表
*/
public Set<String> getTxtKeyWords(String txt) {
Set set = new HashSet();
int l = txt.length();
for (int i = 0; i < l;) {
int len = checkKeyWords(txt, i, matchType);
if (len > 0) {
set.add(txt.substring(i, i + len));
i += len;
} else {
i++;
}
}
txt = null;
return set;
}

/**
* 返回过滤违禁词后的列表，并且被替换为“*”
*/
public String getFilerWords(String txt) {
int l = txt.length();
String filterWords=txt;
for (int i = 0; i < l;) {
int len = checkKeyWords(txt, i, matchType);
if (len > 0) {
filterWords=filterWords.replaceAll(txt.substring(i, i + len),"*");
i += len;
} else {
i++;
}
}
return filterWords;
}


/**
* 仅判断txt中是否有关键字
*/
public boolean isContentKeyWords(String txt) {
for (int i = 0; i < txt.length(); i++) {
int len = checkKeyWords(txt, i, 1);
if (len > 0) {
return true;
}
}
txt = null;
return false;
}


public int getMatchType() {
return matchType;
}


public void setMatchType(int matchType) {
this.matchType = matchType;
}


public static void main(String[] args) {
KeywordFilter filter = new KeywordFilter();
List<String> keywords = new ArrayList<String>();//可以把这个列表变成word.properties文件（包含所有违禁词）
keywords.add("中国人");
keywords.add("黄色");
filter.addKeywords(keywords);


String txt = "中国人民站起来了，黄色";
boolean boo = filter.isContentKeyWords(txt);
System.out.println(boo);
Set set = filter.getTxtKeyWords(txt);
System.out.println(set);
System.out.println(filter.getFilerWords(txt));
}
}