import java.security.MessageDigest;    /**   * 对密码进行加密和验证的程序   */  public class Password {     /** 十六进制下数字到字符的映射数组 */   private final static String[] hexDigits = { "0", "1", "2", "3", "4", "5",     "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };     /**    * 把inputString加密。    *     * @param inputString    *            待加密的字符串    * @return    */   public static String createPassword(String inputString) {    return encodeByMD5(inputString);   }     /**    * 验证输入的密码是否正确    *     * @param password    *            真正的密码（加密后的真密码）    * @param inputString    *            输入的字符串    * @return    */   public static boolean authenticatePassword(String password,     String inputString) {    if (password.equals(encodeByMD5(inputString))) {     return true;    } else {     return false;    }   }     /**    * 对字符串进行MD5编码    *     * @param originString    * @return    */   private static String encodeByMD5(String originString) {    if (originString != null) {     try {      MessageDigest md = MessageDigest.getInstance("MD5");      byte[] results = md.digest(originString.getBytes());      String resultString = byteArrayToHexString(results);      return resultString.toUpperCase();     } catch (Exception ex) {      ex.printStackTrace();     }    }    return null;   }     /**    * 转换字节数组为16进制字串    *     * @param b    *            字节数组    * @return 十六进制字串    */   private static String byteArrayToHexString(byte[] b) {    StringBuffer resultSb = new StringBuffer();    for (int i = 0; i < b.length; i++) {     resultSb.append(byteToHexString(b[i]));    }    return resultSb.toString();   }     /**    * 将一个字节转化成16进制形式的字符串    *     * @param b    * @return    */   private static String byteToHexString(byte b) {    int n = b;    if (n < 0)     n = 256 + n;    int d1 = n / 16;    int d2 = n % 16;    return hexDigits[d1] + hexDigits[d2];   }     public static void main(String[] args) {    String password = Password.createPassword("888888");    System.out.println("对888888用MD5摘要后的字符串：" + password);    String inputString = "8888";    System.out.println("8888与密码匹配？"      + Password.authenticatePassword(password, inputString));    inputString = "888888";    System.out.println("888888与密码匹配？"      + Password.authenticatePassword(password, inputString));   }  }