Convert to/from Hex string in Java

/*from   w  ww .  j a v  a  2  s . com*/
public class Main{


  /**
   * Creates byte array representation of HEX string.<br>
   * 
   * @param s
   *            string to parse
   * @return
   */
  public static byte[] fromHexString(String s) {
    int length = s.length() / 2;
    byte[] bytes = new byte[length];
    for (int i = 0; i < length; i++) {
      bytes[i] = (byte) ((Character.digit(s.charAt(i * 2), 16) << 4) | Character
          .digit(s.charAt((i * 2) + 1), 16));
    }
    return bytes;
  }

  /**
   * Creates HEX String representation of supplied byte array.<br/>
   * Each byte is represented by a double character element from 00 to ff
   * 
   * @param fieldData
   *            to be tringed
   * @return
   */
  public static String toHexString(byte[] fieldData) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < fieldData.length; i++) {
      int v = (fieldData[i] & 0xFF);
      if (v <= 0xF) {
        sb.append("0");
      }
      sb.append(Integer.toHexString(v));
    }
    return sb.toString();
  }
  public static void  main(String[] argv){
    System.out.println(fromHexString("java2s.com"));
  }
}