code: public void toJson(Writer writer) throws IOException {
  		startArray(writer);
  
  		int size = size();
  		for (int i = 0; i < size; i++) {
  			put(writer, get(i));
  			if (i + 1 < size) {
  				addSeparator(writer);
  			}
  		}
  
  		endArray(writer);
  	}
docs: Encodes into the JSON format.
  @param writer {@link Writer} to be used for writing
  @throws IOException
  @author vvakame