code: public Digester init(String algorithm, Provider provider) {
  		if(null == provider) {
  			this.digest = SecureUtil.createMessageDigest(algorithm);
  		}else {
  			try {
  				this.digest = MessageDigest.getInstance(algorithm, provider);
  			} catch (NoSuchAlgorithmException e) {
  				throw new CryptoException(e);
  			}
  		}
  		return this;
  	}
docs: 初始化
  
  @param algorithm 算法
  @param provider 算法提供者，null表示JDK默认，可以引入Bouncy Castle等来提供更多算法支持
  @return {@link Digester}
  @throws CryptoException Cause by IOException