code: public static SingleItemSketch create(final String datum, final long seed) {
      if ((datum == null) || datum.isEmpty()) { return null; }
      final byte[] data = datum.getBytes(UTF_8);
      return new SingleItemSketch(hash(data, seed)[0] >>> 1, seed);
    }
docs: Create this sketch with the given String and a seed.
  The string is converted to a byte array using UTF8 encoding.
  If the string is null or empty no create attempt is made and the method returns null.
  
  <p>Note: this will not produce the same output hash values as the {@link #create(char[])}
  method and will generally be a little slower depending on the complexity of the UTF8 encoding.
  </p>
  
  @param datum The given String.
  @param seed used to hash the given value.
  @return a SingleItemSketch or null