docs: private static char[] encodeHex(byte[] data, char[] toDigits) {
  		final int len = data.length;
  		final char[] out = new char[len << 1];//len*2
  		// two characters from the hex value.
  		for (int i = 0, j = 0; i < len; i++) {
  			out[j++] = toDigits[(0xF0 & data[i]) >>> 4];// 高位
  			out[j++] = toDigits[0x0F & data[i]];// 低位
  		}
  		return out;
  	}