RegexEscape.java

/**
 *
 * Ray Tayek needs function that escapes all regular expression characters in a string.
 */
public class RegexEscape {
  private static char[] reserved="$()*+-.?[\\]^{|}".toCharArray();

  //the toCharArray() way
  public static String encode(String arg){
    char[] source = arg.toCharArray();
    char[] target = new char[source.length *2]; //worst case we have to escape everything
    int target_index = 0;
    for (char c : source) {
      for (char r : reserved) {
        if (c == r) {
          target[target_index++] = '\\';
          break;
        }
      }
      target[target_index++] = c;
    }
    return new String(target, 0,  target_index);
  }


  //just a testing main
  public static void main(String args[]){
    //visual inspection to make sure it works. expect: fi \\ fi\{\}\+fo fum\^
    System.out.println(encode("fi \\ fi{}+fo fum^"));

    //now a simple profile
    long start = System.currentTimeMillis();
    for (int i=0; i<100000; i++){
      encode("fi \\ fi{}+fo fum^");
    }
    long stop = System.currentTimeMillis();
    System.out.println((stop - start) + "ms");

  }
}