AJPFX講解java關鍵詞過濾算法

/**

• java關鍵字過濾
• HashMap實現DFA算法
• 關鍵詞替換爲*
• @author Methol
  */

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();
static final String tihuantxt = "**";
private int matchType = 1; // 1:最小長度匹配 2：最大長度匹配

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");
}
}
}
}

/**

• 重置關鍵詞
  */
  public void clearKeywords() {
  keysMap.clear();
  }

  /**

• 檢查一個字符串從begin位置起開始是否有keyword符合， 若是有符合的keyword值，返回值爲匹配keyword的長度，不然返回零

• flag 1:最小長度匹配 2：最大長度匹配
  */
  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中關鍵字的列表
  */
  public String getTxtKeyWords(String txt) {
  Set set = new HashSet();
  int l = txt.length();
  String newtxt = new String();
  for (int i = 0; i < l;) {
  int len = checkKeyWords(txt, i, matchType);
  if (len > 0) {
  newtxt += txt.substring(0, i);
  newtxt += tihuantxt.substring(0, len);
  newtxt += txt.substring(i + len, txt.length());
  txt = newtxt;
  newtxt = "";
  i += len;
  } else {
  i++;
  }
  }
  return txt;
  }

  /**

• 僅判斷txt中是否有關鍵字
  */
  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;}}