public class md5_test {
//MD5的字符串常量
private final static String[] hexDigits = { "0", "1", "2", "3", "4",
   "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
public static void main(String[] args) {
   // TODO Auto-generated method stub
   try {
    MessageDigest messageDigest= MessageDigest.getInstance("MD5");
    System.out.println(byteArrayToHexString(messageDigest.digest("baidu.com".getBytes())));
   } catch (NoSuchAlgorithmException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }

}
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();
}
/** 將一個字節轉化成十六進制形式的字符串 */
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];
}
}

import org.apache.commons.codec.digest.DigestUtils;
public class ToMain {
public static void main(String[] args) {
   System.out.println(DigestUtils.md5Hex("baidu.com"));
}
}