请将这段C#的MD5加密转化成java代码

MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
string str = rdm1 + clientFlag + strData + strSeed + strConst + rdm2;
byte[] byteStr = System.Text.Encoding.UTF8.GetBytes(str);
string strMd5 = BitConverter.ToString(md5.ComputeHash(byteStr)).Replace("-", "").ToLower();
return rdm1 + strMd5.Substring(7, 21) + rdm2;