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public class Keywords {
  private static ScheduledExecutorService scheduler
      = Executors.newSingleThreadScheduledExecutor();
  private static CharBuffer log;
  private static final Object lock = new Object();

  // Map log file into memory, and periodically reload
  static {
    try {
      FileChannel channel = new FileInputStream(
          "path").getChannel();

      // Get the file's size and map it into memory
      int size = (int) channel.size();
      final MappedByteBuffer mappedBuffer = channel.map(
          FileChannel.MapMode.READ_ONLY, 0, size);

      Charset charset = Charset.forName("ISO-8859-15");
      final CharsetDecoder decoder = charset.newDecoder();

      log = decoder.decode(mappedBuffer); // Read file into char buffer

      Runnable periodicLogRead = new Runnable() {
        @Override public void run() {
          synchronized (lock) { 
            try {
              log = decoder.decode(mappedBuffer);
            } catch (CharacterCodingException e) {
              // Forward to handler 
            } 
          }
        }
      };
      scheduler.scheduleAtFixedRate(periodicLogRead, 0, 5, TimeUnit.SECONDS);
    } catch (Throwable t) {
      // Forward to handler
    }
  }


  public static Set<String> suggestSearches(String search) {
    synchronized (lock) {
      Set<String> searches = new HashSet<String>();

      // Construct regex dynamically from user string
      String regex = "(.*? +public\\[\\d+\\] +.*" + search + ".*)";
  
      Pattern keywordPattern = Pattern.compile(regex);
      Matcher logMatcher = keywordPattern.matcher(log);
      while (logMatcher.find()) {
        String found = logMatcher.group(1);
        searches.add(found);
      }
      return searches;
    }  
  }

}

public class Keywords {
  // ...
  public static Set<String> suggestSearches(String search) {
    synchronized (lock) {
      Set<String> searches = new HashSet<String>();

      StringBuilder sb = new StringBuilder(search.length());
      for (int i = 0; i < search.length(); ++i) {
        char ch = search.charAt(i);
        if (Character.isLetterOrDigit(ch) ||
            ch == ' ' ||
            ch == '\'') {
          sb.append(ch);
        }
      }
      search = sb.toString();

      // Construct regex dynamically from user string
      String regex = "(.*? +public\\[\\d+\\] +.*" + search + ".*)";
      // ...
    }
  }
}